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Preparation of Pd/Ce(F)-MCM-48 catalysts and their catalytic performance of n-heptane isomerization

  • Yanhong Cui , Yanhua Suo , Wei Zhang , Yingjun Wang EMAIL logo , Chunhong Nie and Yanhong Wang
Published/Copyright: September 25, 2023
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Green Processing and Synthesis
From the journal Green Processing and Synthesis Volume 12 Issue 1

Abstract

Ce and F were added to MCM-48 molecular sieve by hydrothermal synthesis, and Pd/Ce(F)-MCM-48 metal acid bifunctional catalysts were prepared by impregnation method. The physical and chemical properties of Ce(F)-MCM-48 and Pd/Ce(F)-MCM-48 were characterized by X-ray diffraction, scanning electron microscope, NH3 temperature programmed desorption instrument, Fourier infrared spectrometer, and X-ray photoelectronic spectrometer characterization methods. The results showed that when the molar ratio of the raw materials was n(Ce):n(TEOS) = 0.02 and n(NaF):n(TEOS) = 0.10, Ce(F)-MCM-48-0.10 molecular sieve had a high degree of order and large specific surface area and pore volume, the total acid content increased, and the acid strength also increased. And it had an acidic center and generated certain oxygen vacancies. The catalyst prepared after Pd impregnation had good dispersibility. 0.4% Pd/Ce(F)-MCM-48-0.10 catalyst still maintained the crystalline phase of MCM-48 molecular sieve. A micro-reaction device was used to examine the catalytic performance of n-heptane isomerization of Pd/Ce(F)-MCM-48-0.10 catalysts. When the hydrogen flow rate was 30 mL·min−1, reduction temperature was 300°C, reduction time was 4 h, weight hourly space velocity was 7.6 h−1, and reaction temperature was 280°C, 0.4% Pd/Ce(F)-MCM-48-0.10 catalyst was used in the heptane isomerization reaction, where the conversion of n-heptane was 67.3% and the selectivity of isoheptane was 96.5%.

Keywords: Pd/Ce (F)-MCM-48 catalyst; fluorine; cerium; n-heptane; isomerization

1 Introduction

With the promulgation of the EU’s Euro V and Euro VI vehicle emission standards and the enhanced global awareness of energy conservation, emission reduction, and environmental protection [1], relevant environmental protection regulations had become stricter in terms of pollutant types and limits. To adapt to stricter emission regulations while meeting the demands of engine technology, the problems relating to pollutant emissions reduction, gasoline quality improvement, and the presence of n-alkane with zero octanes in straight-run gasoline must be resolved. Since straight-run gasoline contained multiple n-paraffins, the best way to improve the octane number was to convert straight chain alkanes into branched chain alkanes. Consequently, n-alkane isomerization had become an important process in the refining industry [2,3,4]. Some recognized industrialized technologies [5] had been developed for the isomerization of relatively short straight-chain (C5 and C6) alkanes, but satisfactory mature technologies for the isomerization of long straight-chain (≥C7) alkanes were still not available [6]. Accordingly, the development of catalysts for n-heptane isomerization had become an important issue.

Many materials can serve as a promising candidate for catalyst supports to immobilize the active species [7], Xie et al. [8,9] prepared a core–shell structured Fe3O4-MCM-41 nanocomposite, and the lipase and sodium silicate were successfully immobilized on the core–shell structured support, respectively. It was shown that the immobilized lipase and sodium silicate had good catalytic activity for transesterification of lard and soybean oil. Most catalysts used in n-heptane isomerization reactions were metal/support bifunctional catalysts. The structural characteristics and acidic properties of these catalyst supports had a considerable influence on the isomerization of straight-chain heptane. Regarding the preparation of support materials, MCM-48 was considered important. For the pure silicon MCM-48 molecular sieve, the surface of the silicon-oxygen tetrahedron was a charge balance system with a low acid concentration due to fewer lattice defects in its skeleton. As a result, there was a lack of catalytic active sites which limited the application and required some functional modifications to the mesoporous molecular sieve. Currently, the method of introducing heteroatoms is widely used [10]. Scholars had successively replaced some elements with similar properties, such as Fe and Co [11], and Mo and Al [12,13], with skeleton silicon elements, forming special metal complex heteroatomic molecular sieves. Another important support modification strategy was to introduce anions such as F−, Cl−, S2−, N3−, etc., [14] into the molecular sieve skeleton. Among them, fluorine possessed unique properties such as high electronegativity and a small atomic radius [15]. Recently, Jiang et al. [16] synthesized a fluorine-enhanced Pd/HZSM-5 catalyst whose surface morphology, hydrophobicity, acidity, and electronic properties could be regulated by the doping amount of fluorine, and the catalyst demonstrated good catalytic activity for the hydrodeoxygenation of acetophenone. Yang et al. [17] prepared an anionic fluorine-doped La0.6Sr0.4Fe0.8Ni0.2O3−δ perovskite cathode material with enhanced electrocatalytic activity. Some progress had been made in several catalytic material studies, where their surface and structure had been modified to attain special physical and chemical properties.

The nano-sized porous materials, as used for the preparation of solid catalysts, can permit the higher loading of active species and better access of the active sites [18,19]. Roy et al. [20] synthesized the novel mesoporous catalysts consisting of Ru and Fe3O4 nanoparticles (NPs) impregnated over ceria promoted 2D-hexagonal SBA-15 type mesoporous silica material and employed it in the CO2 reduction reaction. Optimal process conditions could render much higher CO2 conversion efficacy for selective methane synthesis in comparison with previous investigations. However, studies regarding the catalytic performance of n-heptane isomerization with a Pd-loaded catalyst on MCM-48 molecular sieves modified by Ce and F simultaneously had not been reported yet.

The novelty of this study was that Ce(F)-MCM-48 molecular sieve was prepared by hydrothermal synthesis, while Pd/Ce(F)-MCM-48 bimetallic catalyst was prepared by impregnation method. Pd NPs were used as catalytic active sites [21], Ce was used as catalyst additives to mainly increase the acidity of molecular sieve support, Ce-MCM-48 provided alkane isomerization sites [3], F doping took away part of oxygen to produce surface defects and oxygen vacancies, which was conducive to anchoring metal Pd atoms [22], making Pd NPs have good dispersion. Based on the characterization results, the effects of Ce and F introduction on the structure of the support and catalyst were discussed, and then the catalytic performance of these catalysts in n-heptane isomerization was investigated on a microreactor. It was hoped that such catalysts would be applied in the development of long-chain alkane isomerization catalysts, thereby laying a theoretical foundation for the production of green and clean gasoline.

2 Materials and methods

2.1 Materials

Tetraethyl orthosilicate (TEOS, AR), sodium fluoride (NaF, AR) were purchased from Tianjin Damao Chemical Reagent Factory, cetyltrimethylammonium bromide (CTAB, AR), cerous nitrate [Ce(NO3)3·6H2O] and palladium nitrate [Pd(NO3)2·2H2O, AR] were purchased from Sinopharm Chemical Reagent Co. Ltd, sodium hydroxide (NaOH, GR) was purchased from Tianjin Kemiou Chemical Reagent Co. Ltd, absolute ethyl alcohol (AR) was purchased from Liaoning Quanrui Reagent Co. Ltd, n-heptane (AR) was purchased from Shenyang East China Reagent Factory, deionized water from a Milli-Q System was used in all experiments, and hydrogen (volume fraction 99.99%) was purchased from Daqing Xuelong Gas Station.

2.2 Synthesis of the Ce(F)-MCM-48 mesoporous material

Under alkaline conditions, CTAB was used as the template, and Ce(NO3)3·6H2O and NaF were used as the added reagents, Ce(F)-MCM-48 was synthesized by hydrothermal method.

First, NaOH was dissolved in deionized water. Then, Ce(NO3)·6H2O and NaF were stirred at 35℃ for 0.5 h and CTAB was gradually added to the above solution and stirred for 1.5 h until the mixtures became clear and transparent, and then TEOS was added dropwise to the mixture by pipette and stirred for 1 h. The molar ratio of reactant raw materials was n(TEOS):n(CTAB):n(H2O):n(NaOH):n(Ce):n(NaF) = 1.0:0.65:62:0.5:0.02:x (x = 0, 0.05, 0.10, 0.15). The initial as-prepared gel was transferred into a stainless-steel reactor lined with polytetrafluoroethylene and placed in a drying oven for crystallization at 120°C for 72 h. The product was washed and filtered with water and dried at 90°C for 6 h on a polytetrafluoroethylene-coated electric heating plate, further dried at 105°C for 5 h in an electric blast drying oven, and calcinated at 550°C for 6 h in a box-type resistance furnace.

The prepared sample was marked as Ce(F)-MCM-48-x, and when x = 0, it was marked as Ce-MCM-48. MCM-48 was synthesized without the addition of Ce(NO3)3·6H2O and NaF, which was marked as MCM-48, and the other steps were the same as above.

2.3 Preparation of Pd/Ce(F)-MCM-48 catalyst

Pd-loaded catalysts with mass fractions of 0.4% were prepared by impregnation method. Pd(NO3)2·2H2O was dissolved in deionized water, Ce(F)-MCM-48-0.10 was then immersed in the solution which was then subjected to ultrasonic dispersion at 50°C for 0.5 h. Subsequently, the solution was left in a static state at room temperature overnight, the drying steps were same as 2.2. Then, the above mixtures were calcinated at 400°C for 4 h in a resistance furnace, 0.4% Pd/Ce(F)-MCM-48-0.10 catalysts were obtained. Pd/MCM-48 and Pd/Ce-MCM-48 catalysts were prepared using the same method.

2.4 Characterization of catalysts

An X-ray diffractometer (XRD, smartLAB SE, Japanese Rigaku Corporation) was used for crystal structure analysis with Cu Kα as the radiation source operated at the tube voltage of 40 kV and tube current of 40 mA. A scanning electron microscope (SEM, Hitachi High-Technologies S-4800II, Japan) was used for the microscopic surface morphology analysis of the molecular sieve samples. A Fourier infrared spectrometer (FT-IR, AVATAR-360, American Thermo Nicolet) was used for infrared spectroscopy analysis of the samples. A specific surface area and pore size test analyzer (TriStar II, American Micromeritics) was used to determine the structural parameters of the sample. An ion chromatograph (SGB-YY101040H, American Thermo Fisher) was used to characterize the F content. An inductively coupled plasma optical emission spectrometer (ICP-OES, Optima8000, American PerkinElmer) was used to characterize the Pd and Ce content. An NH3 temperature programmed desorption instrument (NH3-TPD, Autochem II 2920, American Micromeritics) was used to test the surface acid content and acid intensity distribution of the samples. A transmission electron microscope (TEM, JEM-2100PLUS, Japanese JEOL Ltd) was used to record the sample images with an acceleration voltage of 100–120 kV. A field emission scanning electron microscope (FESEM, Czech TESCAN MIRA LMS) with energy dispersive spectroscopy (EDS) was used for the surface morphology evaluation. An X-ray photoelectronic spectrometer (XPS, American Thermo Fisher Nexsa type) was used for the qualitative and quantitative characterization of the chemical state of the surface elements of the samples. An infrared spectrometer (VERTEX 70, German Bruker) was used for the pyridine infrared spectroscopy analysis of the samples. A gas chromatograph (GC-7980A, Zhengzhou, China) was used to analyze the heptane isomer products.

2.5 Evaluation of the n-heptane hydroisomerization reaction

The catalytic reaction performance experiment was conducted in a micro fixed-bed reactor under atmospheric pressure. The catalyst powder was pressed and sieved to collect 60–80 mesh particles for use. Then, 0.40 g particles were placed in the reaction tube (inner diameter 6 mm). The catalyst was activated in a hydrogen atmosphere for 4 h at 400°C before the reaction, and then the temperature was lowered to the required reaction temperature. The reaction evaluation was performed under the conditions of an H2 flow rate of 30 mL·min−1, molar ratio of n(H2):n(C7H16) = 12, and WHSV of 7.6 h−1. After the reaction was stable for 0.5 h, the sample was taken, and the product was analyzed online by gas chromatograph FID detector. The catalytic performance was evaluated via the conversion rate (x) of n-heptane, the selectivity (s), and the yield (y) of the product. These can be calculated by Eqs. 1–3 as follows:

(1) x ( % ) = The amount of n - heptane consumed in the reaction The amount of n - heptane passed in the reaction × 100 %

(2) s ( % ) = The amount of isoheptane generated in the reaction The amount of n - heptane consumed in the reaction × 100 %

(3) y ( % ) = The amount of isoheptane generated in the reaction The amount of n - heptane passed in the reaction × 100 %

3 Results and discussion

3.1 Effect of NaF doping on the preparation of the support.

Figure 1 showed the small-angle XRD of Ce(F)-MCM-48-x mesoporous material. All the five materials showed strong (211) diffraction peaks at 2θ = 2–3° [23]. Compared with MCM-48, the intensity of the (211) diffraction peak of Ce-MCM-48 decreased and the (220) diffraction peak almost disappeared, the phenomenon of peak broadening appeared. This indicated that the crystallinity decreased after the doping of Ce. When n(F):n(Si) was 0.05, the (211) diffraction peak was enhanced and the (220) diffraction peak was clearly visible. When n(F):n(Si) was 0.10, the (420) and (332) diffraction peaks appeared and all the diffraction peaks became sharp, and the intensity was obviously enhanced. The resolution of the peak was better. Diffraction peaks at 2θ = 4–5° all conformed to the Ia3d (211, 220, 420, 332) space group of the characteristic MCM-48 diffraction peaks [13]. This was the main factor that contributed to the good chemical stability of the material molecules. The hydration layer of CTAB and silicate can be effectively removed by adding F-anions with strong self-hydration tendency in the synthesis system. The key condition for the synthesis of cubic MCM-48 was to facilitate the formation and growth of CTAB micelles and increase the g value [24]. According to literature report [25], F− and O2− had equivalent ionic radius, and the addition of F− would replace part of O2−, which would destroy the lattice structure of some oxides. The oxide crystal was distorted, and unsaturated bonds were generated on its surface, which could increase the lattice defects of oxides. When n(F):n(Si) was 0.15, the intensity of each diffraction peak decreased, the possible reason was that the excessive doping of F−1 in the system led to the continuous destruction of the oxide lattice, causing local pore collapse and the decrease in the order of pore structure. Therefore, the optimal concentration of n(F):n(Si) was 0.10. At this ratio, F and Ce synergistically promoted the polymerization of silicates, resulting in better crystallization. In subsequent experiments, the Ce(F)-MCM-48-0.10 was selected as the support for F-doping.

Figure 1 XRD patterns of MCM-48 and Ce(F)/MCM-48-x (x = 0, 0.05, 0.10, 0.15).
Figure 1

XRD patterns of MCM-48 and Ce(F)/MCM-48-x (x = 0, 0.05, 0.10, 0.15).

Figure 2 displayed the SEM images of MCM-48, Ce-MCM-48, and Ce(F)-MCM-48-0.10. The MCM-48 mesoporous material synthesized by conventional hydrothermal synthesis had a spherical particle morphology accompanied by a small amount of agglomeration and small particles with good regularity and purity [11]. After Ce was doped, the morphology became irregular, accompanied by pits, broken hemispheres, and agglomeration. For mesoporous material synthesized with the addition of F, recombination occurred in the crystal cage due to further changes in the chemical bonds, where the silicate was re-polymerized to form regular spherical particles of uniform size [26]. The order and purity were greatly improved and more spheres with a particle size of nearly 1 µm were generated. This indicated that the introduction of F was conducive to the formation of a cubic phase of MCM-48 structure. Furthermore, the introduction of Ce and F weakened the force between inorganic and organic interfaces. Under the action of surfactants, SiO2 was arranged in an orderly manner according to certain crystallographic rules to obtain a crystalline mesoporous material [14]. This series of changes was consistent with the XRD pattern of the samples in Figure 1.

Figure 2 SEM images of the products of (a) MCM-48, (b) Ce-MCM-48, and (c) Ce(F)-MCM-48-0.10.
Figure 2

SEM images of the products of (a) MCM-48, (b) Ce-MCM-48, and (c) Ce(F)-MCM-48-0.10.

3.2 N2 adsorption–desorption and texture properties

Figure 3a shows the N2 adsorption–desorption isotherms of MCM-48, Ce-MCM-48, Ce(F)-MCM-48-0.10, 0.4% Pd/Ce-MCM-48, and 0.4% Pd/Ce(F)-MCM-48-0.10 which can all be classified as Langmuir IV isotherms and exhibited H4 hysteresis loops. The hysteresis loop of the samples showed an obvious change within the range of relative pressure p/p 0 of about 0.4–0.9, indicating the presence of large mesopores produced by inter-particle space [27]. Figure 3b shows the pore size distribution curve. The pore size distribution was obtained by the Barrett–Joyner–Halenda equation. The Ce-MCM-48 pore size distribution range was slightly larger than that of MCM-48, while that of Ce(F)-MCM-48-0.10 narrowed with the trend of the H4 hysteresis loop, which confirmed the existence of uniform and cylindrical mesopores [28].

Figure 3 N2 adsorption–desorption isotherms (a) and pore size distributions (b) of MCM-48, Ce-MCM-48, Ce(F)-MCM-48-0.10, 0.4% Pd/Ce-MCM-48, and 0.4% Pd/Ce(F)-MCM-48-0.10.
Figure 3

N2 adsorption–desorption isotherms (a) and pore size distributions (b) of MCM-48, Ce-MCM-48, Ce(F)-MCM-48-0.10, 0.4% Pd/Ce-MCM-48, and 0.4% Pd/Ce(F)-MCM-48-0.10.

Based on Figure 3b and Table 1, it can be seen that due to the Ce ions in Ce-MCM-48 having a larger radius than the Si ions, the length of the Ce–O bond was longer than that of the Si–O bond [29], causing the stretching of the skeleton and the increase in average pore size. Further increase in the surface area and total pore volume of Ce(F)-MCM-48-0.10 did not cause any spatial steric resistance of the pore channels on the skeleton. The Ce(F)-MCM-48-0.10 pore size was also further enlarged, and the mesopore size tended to be uniform. The synergy of F and Ce enabled the support frame to form a new structure [26], which was also consistent with the XRD pattern in Figure 1.

Table 1

Physical properties of the samples

Sample Surface area (m2·g−1) Pore volume (cm3·g−1) Average pore diameter (nm) Pd (loading rate, wt%) Ce (loading rate, wt%) F (loading rate, wt%)
MCM-48 897.1 0.93 2.61 — — —
Ce-MCM-48 972.6 0.97 2.78 — 66.5 —
Ce(F)-MCM-48-0.10 1,323.2 1.17 3.07 — 65.5 53.3
0.4% Pd/Ce-MCM-48 894.2 0.95 2.52 97.5 60.5 —
0.4% Pd/Ce(F)-MCM-48-0.10 1,293.0 1.13 2.91 97.8 65.0 52.9

As shown in Table 1, the actual loading content of Ce in Ce(F)-MCM-48-0.10 was slightly reduced, and the doping of F did not cause serious Ce peeling with the actual loading percentage of 53.3% and 65.5%, respectively. According to ion chromatography test, the mass fraction of F in Ce (F)-MCM-48-0.10 was 1.51%. F and Ce can be loaded on the skeleton simultaneously. Due to the Ce(F)-MCM-48-0.10, specific surface area and pore volume were the largest, the adsorption performance of the molecular sieves improved. Both the specific surface area and pore volume of the 0.4% Pd/Ce(F)-MCM-48-0.10 catalyst were reduced slightly, indicating that Pd had been loaded on the support and that F had improved the structural performance. Benaissa et al. [30] reported four mesoporous supports loaded with palladiums, of which MCM-48 had the largest surface area. The effective load rate of Ce in 0.4% Pd/Ce-MCM-48 was 60.5%. While the effective load rate of Pd, F, and Ce were 97.8%, 52.9%, and 65.0%, respectively, and there was almost no loss of F and Ce after Pd impregnation. The ion chromatograph test results indicated that the mass fraction of F in 0.4% Pd/Ce(F)-MCM-48-0.10 was 1.45%.

3.3 Acidic properties

Figure 4 shows the NH3-TPD of the support and catalysts. Each peak area corresponded to the acid strength of the acid center. Within the temperature range of 150–250°C, the NH3 desorption peak corresponded to weak acid strength. Within the range of 250–400°C, the desorption peak corresponded to medium acid strength. There was no peak corresponding to the strong acid site. The order of acid content and strength of the acid sites of the samples was 0.4% Pd/Ce(F)-MCM-48-0.10 > 0.4% Pd/Ce-MCM-48 > Ce(F)-MCM-48-0.10 > Ce-MCM-48 > MCM-48 shown in Table 2. Catalysts with suitable weak acid and medium-strength acid would exhibit a high catalytic activity in isomerization reactions [31].

Figure 4 NH3-TPD characterizations of different samples.
Figure 4

NH3-TPD characterizations of different samples.

Table 2

Acidity of MCM-48, Ce-MCM-48, Ce(F)-MCM-48-0.10, 0.4% Pd/Ce-MCM-48, and 0.4% Pd/Ce(F)-MCM-48-0.10

Sample Br o ̈ nsted acid (mmol·g−1) Lewis acid (mmol·g−1) Amount of acid site (mmol·g−1) Amount of acid site (mmol·g−1)a
MCM-48 0.07 0.00 0.07 −
Ce-MCM-48 0.59 0.30 0.89 0.92
Ce(F)-MCM-48-0.10 0.72 0.52 1.24 1.43
0.4% Pd/Ce-MCM-48 1.45 2.93 4.38 2.76
0.4% Pd/Ce(F)-MCM-48-0.10 1.87 3.84 5.71 3.12

aThe acid content is calculated from NH3-TPD.

Table 2 shows the type and acid content of the acid center on the surface of the support and catalysts. The acid content of MCM-48 was negligible and the surface was non-acidic. After the Ce was doped, it formed a compound with the support. The Bronsted acid content increased due to the formation of Si–O–Ce bonds, the increase in Lewis acid content may be caused by the presence of CeO2 in mesoporous materials [31]. The acid content also increased significantly after the introduction of F. This was because F had a similar radius to the hydroxyl groups and could exchange freely, allowing it to enter the skeleton to form a F–Si structure, releasing lattice oxygen. The function of fluoride was to provide L-acid centers [32,25]. The bridged hydroxyl group (SiF–OH) generated by the isomorphous replacement of the skeleton became the acidic center of the Ce(F)-MCM-48 support, which further increased the total number of acid content. For the Pd/Ce-MCM-48 catalyst, coordination bonds were generated following Pd impregnation, Pd provided Lewis acid, resulting in an increased content of acid sites and the total acid content.

3.4 Crystal structure

Figure 5a shows the small-angle XRD patterns of 0.4% Pd/MCM-48, 0.4% Pd/Ce-MCM-48, and 0.4% Pd/Ce(F)-MCM-48-0.10 catalyst materials prepared by the impregnation of the three supports in Pd. Compared with MCM-48 in Figure 1, the 0.4% Pd/Ce(F)-MCM-48 catalyst exhibited (211) and (220) strong diffraction peaks at 2θ = 2–3° while still exhibited typical MCM-48 characteristics, indicating a relationship with a high degree of support crystallization [13]. 0.4% Pd/MCM-48 and 0.4% Pd/Ce-MCM-48-0.10 only exhibited (211) diffraction peaks with a widened peak shape, but the (220) diffraction peak disappeared. Figure 5b shows the wide-angle XRD patterns of the three corresponding materials, all of which had a wide peak at 2θ = 20–30°. There was a typical silicon-oxygen tetrahedron structure while the peak position remained unchanged. The signal strength of 0.4% Pd/Ce(F)-MCM-48-0.10 was enhanced, indicating that its degree of order was improved. 0.4% Pd/Ce-MCM-48 exhibited the (220) characteristic diffraction peak of CeO2 cubic crystal at 2θ = 47.5° (JCPDS No. 34-0394) [33], but this peak was not observed in 0.4% Pd/Ce(F)-MCM-48-0.10, indicating that Ce was dispersed and assembled in the support skeleton after the introduction of F. No diffraction peaks of Pd species were observed in any of the three materials. This proved that the metal Pd can be well dispersed on the support surface. As shown in Figure 6, it was observed with TEM that the metal oxide clusters of 0.4% Pd/Ce-MCM-48 catalyst formed agglomerations, while the embedded Pd and Ce species were poorly dispersed. The 0.4% Pd/Ce(F)-MCM-48-0.10 catalyst did not exhibit a larger metal oxide crystal phase, indicating that it existed in the form of small particles, or formed metal oxide nanoparticles in the support pores [30]. The distinct hexagonal hole arrangement and different directions of crystal lattice stripes also reflected the three-dimensional direction and well-organized pore structure of the support.

Figure 5 XRD patterns of Pd/MCM-48, Pd/Ce-MCM-48, and Pd/Ce(F)-MCM-48-0.10: (a) small-angle XRD and (b) wide-angle XRD.
Figure 5

XRD patterns of Pd/MCM-48, Pd/Ce-MCM-48, and Pd/Ce(F)-MCM-48-0.10: (a) small-angle XRD and (b) wide-angle XRD.

Figure 6 TEM image of (a) 0.4% Pd/Ce-MCM-48 and (b) 0.4% Pd/Ce(F)-MCM-48-0.10.
Figure 6

TEM image of (a) 0.4% Pd/Ce-MCM-48 and (b) 0.4% Pd/Ce(F)-MCM-48-0.10.

3.5 Microscopic morphology and structure

Based on the SEM scanning and EDS spectroscopy analysis in Figure 7, the 0.4% Pd/Ce(F)-MCM-48-0.10 catalyst demonstrated a regular morphology with a smooth spherical surface. Pd and Ce oxide, as well as the particles of F, were evenly and successfully coated on MCM-48, without any signs of agglomeration or sintering. This can be attributed to the interaction between the chemical bonds formed on the support interface and the Pd particles, which drove the diffusion of Pd atoms to the cerium lattice. It could be inferred that Pd may be added to the cerium lattice in the MCM-48 space [34], which was consistent with the XRD results shown in Figure 5b. This indicated that Ce(F)-MCM-48-0.10 was a satisfactory support for dispersing Pd NPs.

Figure 7 SEM images, EDX spectrum, and SEM mapping of Pd/Ce-MCM-48 and Pd/Ce(F)-MCM-48-0.10.
Figure 7

SEM images, EDX spectrum, and SEM mapping of Pd/Ce-MCM-48 and Pd/Ce(F)-MCM-48-0.10.

3.6 Chemical environment

In Figure 8, the binding states of the elements in the samples were examined using the XPS spectrum. Figure 8a shows the full spectrum of the two samples. Figure 8b shows the fitted O1s spectra of the two samples. The O1s spectra can be deconvoluted to three peaks: lattice oxygen at 530.31 eV, oxygen modified by the nearby presence of an oxygen vacancy at 532.38 eV, and hydroxyl species at 533.3 eV [5,35,36,37]. This study had deviations, which was consistent with the literature reported, the hypothesis that the replacement of heavier atoms would cause the shift of the O1s peak towards the high binding energy side [38]. The oxygen vacancy areas in 0.4% Pd/Ce-MCM-48 and 0.4% Pd/Ce(F)-MCM-48-0.10 were measured to be 64.7%, and 72.5%, respectively. Oxygen vacancies would take away a pair of electrons [20], promoting metal Pd anchoring on the support [22]. Figure 8c shows the Si2p spectra. The deconvolution produced one peak at binding energies of 103.9 eV, which was assigned to Si4+ species, indicating that amorphous silica was the main phase of nanospheres. The peak near 102.9 eV was related to Si–O–Ce. It was worth noting that due to the strong electronegativity of F being higher than that of Si ion, the binding energy of F–Si was higher than that of Si–Si. The peak of 104.8 eV in 0.4% Pd/Ce (F)-MCM-48-0.10 was related to F–Si–O [39,40,41].

Figure 8 XPS spectra of Pd/Ce-MCM-48 and Pd/Ce(F)-MCM-48-0.10: (a) XPS full spectra, (b) O1s, (c) Si2p, (d) F1s, (e) Ce3d, and (f) Pd3d of Pd/Ce-MCM-48 and Pd/Ce(F)-MCM-48-0.10.
Figure 8

XPS spectra of Pd/Ce-MCM-48 and Pd/Ce(F)-MCM-48-0.10: (a) XPS full spectra, (b) O1s, (c) Si2p, (d) F1s, (e) Ce3d, and (f) Pd3d of Pd/Ce-MCM-48 and Pd/Ce(F)-MCM-48-0.10.

Figure 8d shows the F1s spectra. The characteristic peak at the binding energy of 684.5 eV was attributed to the covalent Si–F bond. F was at the binding energy of 685.8 eV, with high bonding energy [42,43,40]. Due to the hybridization of the Ce4f and ligand orbitals as well as the partial occupation of the 4f orbital, the Ce3d spectra in Figure 8(e) was relatively complex. There were two types of cerium oxide on the surface, namely, Ce3+ and Ce4+. Ce3+ included V′ and u′, while Ce4+ included V′, V″, V‴, u, u″, and u‴ [29,44]. As to the redox coupling Ce3+/Ce4+, it was generally believed that the presence of Ce3+ generated more surface defects and oxygen vacancies which helped improve the catalytic efficiency [45]. In the Pd3d spectra in Figure 8(f), the binding energy of Pd3d5/2 was 337.4 eV, which was attributable to the high dispersion of PdO [46]. The existence of Pd on the surface of the two supports was quite different, due to the different numbers and intensities of active sites on the surface of different supports. F modification can regulate the distribution of Pd3d core electrons and attract electrons from adjacent Pd to trigger charge transfer, thereby improving the stability of Pd particles in a higher oxidation state [16].

Figure 9 shows the FT-IR spectrum of the sample skeleton configuration for analysis. All three materials of Ce-MCM-48, Ce(F)-MCM-48-0.10, and Pd/Ce(F)-MCM-48-0.10 had skeleton vibration peaks at 810 and 1,088 cm−1, as found in the silicate samples. The peak at 970 cm−1 of Ce-MCM-48 was attributed to Si–O–Ce and Si–O tensile vibrations [47]. The asymmetric tensile vibration peak intensity of the Ce(F)-MCM-48-0.10 molecular sieve increased at 1,088 cm−1. This indicated that the chemical bond structure was altered after the introduction of F and the crystallinity was higher, which was consistent with the XRD results in Figure 1. For Ce(F)-MCM-48-0.10, there was a symmetrical tensile vibration at 810 cm−1. These characteristic peaks narrowed and exhibited a red shift after the introduction of F [48]. For the Pd/Ce(F)-MCM-48-0.10 sample, the single peaks were again weakened, which may be related to the F–Si structures formed in the molecular sieve and the coordination bond formed between Pd and the support. Theoretically, Pd–O stretching vibration should be observed at 486 cm−1 in the Pd/Ce(F)-MCM-48-0.10 sample. However, as the infrared spectrum was not sensitive to the coordination bond and the palladium content was low, this vibration was not detected. Only weakened absorption peaks at 486 cm−1 were observed, which also verified the existence of the vibration.

Figure 9 FT-IR spectra.
Figure 9

FT-IR spectra.

3.7 Catalytic performance evaluation

3.7.1 Effect of different Pd supports on the isomerization performance of n-heptane

Pd/MCM-48, Pd/Ce-MCM-48, and Pd/Ce(F)-MCM-48-0.10 were prepared with a Pd mass fraction of 0.4%. Figure 10 shows that n-heptane conversion was 8.8% and the selectivity was 11.2% for the Pd/MCM-48 catalyst. The catalytic performance was the lowest as the support was not acidic. After Ce was introduced into the support, the acidity increased, the isomerized carbocations were rapidly desorbed from the acid sites, which inhibited the cracking reaction. The n-heptane conversion was 47.5% and the selectivity was 76.2% for the Pd/Ce-MCM-48 catalyst. The oxidation state of the metal catalyst remained unchanged after the introduction of F, which was conducive to the transfer of electrons from the support to the metal oxide, subsequently promoting the catalytic reaction [49]. Its larger pore size and shape selectivity enabled the rapid diffusion of isoheptane in the catalyst and reduced the product retention time, which in turn prevented secondary reactions such as cracking and improved the hydroisomerization performance to a certain extent. The chemical environment on the support surface was beneficial in regulating the electronic and geometric properties of the dispersed Pd species. Furthermore, the support enabled the species to exhibit excellent chemical properties [36]. The n-heptane conversion was 67.3% and the isoheptane selectivity was 96.5% for the Pd/Ce(F)-MCM-48-0.10 catalyst, which demonstrated the improved isomerization properties. As shown in Table 3, the effect metal modified catalyst on the hydroisomerization properties of n-heptane reported in the literature.

Figure 10 Catalytic performance of n-heptane isomerization of the catalyst with different supports.
Figure 10

Catalytic performance of n-heptane isomerization of the catalyst with different supports.

Table 3

Effect of metal modified catalyst on the hydroisomerization properties of n-heptane

Catalyst Reaction temperature (K) Reduction temperature (K) Conversion (%) Selectivity (%) Reference
0.4% Pd/Ce(F)-MCM-48-0.10 503 673 67.3 96.5 This paper
Pt/HBM 513 — 55.76 86.11 [27]
M-MCM-48 (M = Zr, Mg) 533/553 673 55.2/91.5 48/72.3 [50]
Mo-MCM-48 523 673 36.71 52.41 [12]
Pt/HBS 513 — 75.57 90.04 [2]
Pt-Beta 563 723 90.7 55.8 [28]
Pt/SBB-25 563 723 81.4 86.4 [28]
Pt/ASA 473–673 573 80.9 81 [3]
Mo/ASA 473–673 573 82 80 [3]
Mo/AI-SBA-15 473–673 573 83 69 [3]
0.5% Pt/5%MoO3-HBEA 523 673 81.6 43.5 [4]
PtSn(2)-micro-SAPO11 523 673 <60 <60 [51]
PZH-0.3 533 723 81.1 94.2 [52]
1% Pt/SBA-15 673 723 85 − [5]
0.05% Pt1@CeOx/SAPO-11 633 523 57.9 89.4 [53]

3.7.2 Effect of reaction temperature on the catalytic performance of 0.4% Pd/Ce(F)-MCM-48-0.10

Figure 11 showed the catalytic performance curve of the 0.4% Pd/Ce(F)-MCM-48-0.10 catalyst for n-heptane isomerization at different reaction temperatures. With reaction temperatures between 220 and 360°C, n-heptane conversion increased as the reaction temperature increased, while the isomerization selectivity exhibited a downward trend. The isomerization of n-heptane was a micro-exothermic reaction, but if the reaction temperature was too low, the overall reaction rate would be slow, resulting in an unsatisfactory conversion. Therefore, the reaction temperature needed to be increased. Only after reaching the specific reaction temperature, the reactants would be activated and the number of activated molecules increased. The increased number of effective reactant collisions was conducive to the reaction. When the reaction temperature was 280°C, the n-heptane conversion was 67.3% and the isomerization selectivity was 96.5%. At this time, the maximum isoheptane yield was 64.9%. Pyrolysis was endothermic, while n-heptane isomerization was exothermic. According to the thermodynamic equilibrium, it could be learned that continuously increasing the temperature will promote endothermic pyrolysis and may even cause excessive carbon deposits on the catalyst surface, resulting in decreased activity, a lower conversion of n-heptane, and a reduced yield. Excessive reaction temperatures could also cause the skeleton structure of the catalyst to collapse. When the reaction temperature exceeded 280°C, the yield gradually decreased. Therefore, the optimal reaction temperature was 280°C.

Figure 11 Catalyst performance of 0.4% Pd/Ce(F)-MCM-48-0.10 as a function of reaction temperature.
Figure 11

Catalyst performance of 0.4% Pd/Ce(F)-MCM-48-0.10 as a function of reaction temperature.

3.7.3 Effect of reaction duration on the catalytic performance of 0.4% Pd/Ce(F)-MCM-48-0.10

Figure 12 shows the catalytic performance curve of the 0.4% Pd/Ce(F)-MCM-48-0.10 catalyst for n-heptane isomerization at the reaction duration. When the reaction temperature was fixed at 280°C, the conversion of n-heptane and isomerization selectivity increased with the extension of reaction duration within 0–2 h. The conversion of n-heptane was 67.3% and the isomerization selectivity was 96.5% when the reaction duration exceeded 2 h. Compared with previous studies [6,12,26], excellent catalytic performance was achieved in a relatively short period, which was probably related to the excellent mass transfer rate of the catalyst. When the reaction duration was extended to 24 h, the catalytic performance slowly decreased, and the conversion of n-heptane dropped to 62.5%. This may be due to the formation of some carbon deposits on the active center of the catalyst which lowered the conversion rate as the reaction progressed. Furthermore, the collapse of the pore channels, blockage of the pore structure, loss of acid sites, etc., also caused the catalyst activity to decrease. During the 24 h continuous reaction, the selectivity increased slightly to 98.9%. This was probably due to carbon deposition at the strong acid center that catalyzed the pyrolysis [54], thereby improving isomerization selectivity. The reaction duration test of the catalyst showed that the catalyst exhibited satisfactory stability. For further understanding the as-prepared catalysts of the n-heptane hydrogenation conversion, the consideration of the reaction mechanism was vital. According to the literature [3,12,28,52], the reaction of long-chain alkanes on metal-support bifunctional catalysts was generally considered a bifunctional mechanism. While in this study, the precious metal Pd was loaded on the Ce(F)-MCM-48-0.10 mesoporous molecular sieve to prepare the catalyst, which could be inferred that the conventional bifunctional mechanism was followed. It was generally believed that the isomerization was completed through the bifunctional reaction mechanism on the above catalysts. The catalytic mechanism was usually loading precious metal Pd on acid supports. N-heptane dehydrogenated at the precious metal Pd active sites to form olefins, then the olefins migrated to the acid sites and underwent isomerization reactions, thereby generating isomer olefins, and finally the isomer olefins were hydrogenated at the precious metal active sites to generate the product, isoheptane. It provided hydrogenation/dehydrogenation function at metal sites, and protonation/deprotonation and skeleton rearrangement function at acid sites.

Figure 12 Catalyst performance of 0.4% Pd/Ce(F)-MCM-48-0.10 as a function of reaction time.
Figure 12

Catalyst performance of 0.4% Pd/Ce(F)-MCM-48-0.10 as a function of reaction time.

4 Conclusion

  1. When the molar ratio of the reaction raw materials was n(Ce):n(TEOS) = 0.02 and n(NaF):n(TEOS) = 0.10, Ce and F were used as structural additives, the Ce(F)-MCM-48-0.10 molecular sieve was characterized by a high degree of order, increased specific surface area and pore volume, uniform pore size distribution, augmented acid content, and enhanced acidity. The specific order was Ce(F)-MCM-48-0.10 > Ce-MCM-48 > MCM-48.

  2. Pd/Ce(F)-MCM-48-0.10 catalyst demonstrated a satisfactory degree of order and Pd dispersion a high effective loading percentage, and a slight loss of Ce and F after the impregnation of Pd. The prepared bifunctional catalyst had the metal sites and the acidic sites of the support. Under the synergistic effect of Ce and F, the Ce(F)-MCM-48-0.10 molecular sieve proved to be a good support for the dispersion of Pd nanoparticles.

  3. Based on the study on the catalyst performance of the isomerization reaction of n-heptane, under the conditions of the optimal precious metal Pd loading of 0.4%, the reaction temperature of 280°C, and a reaction time of 24 h, the conversion of n-heptane isomerization was 67.3%, and the selectivity of isoheptane was 96.5%, and the catalytic performance of Pd/Ce(F)-MCM-48-0.10 was relatively stable. For the Pd-loaded catalyst with MCM-48 as the support for heptane isomerization, it was necessary to modify MCM-48 with Ce and F synergistically.

Acknowledgement

The authors acknowledge the support of Analysis and Test Center of Northeast Petroleum University.

  1. Funding information: This work was supported by both the Support Plan for Outstanding Scientific Research Talents of Provincial Advantageous and Characteristic Disciplines of Chemical Engineering and Technology of Northeast Petroleum University and Natural Science Foundation of Heilongjiang Province, China (No. LH2021E012).

  2. Author contributions: Yanhong Cui: writing – original draft, writing – review and editing, methodology, conceptualization, software, and investigation; Yanhua Suo: validation, visualization, and supervision; Wei Zhang: formal analysis, writing – review and editing; Yingjun Wang: project administration, funding acquisition, and resources; Chunhong Nie: project administration and formal analysis; Yanhong Wang: formal analysis and data analysis.

  3. Conflict of interest: The authors state no conflict of interest.

  4. Data availability statement: All data generated or analyzed during this study are included in this published article.

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Received: 2023-04-17
Accepted: 2023-07-24
Published Online: 2023-09-25

© 2023 the author(s), published by De Gruyter

This work is licensed under the Creative Commons Attribution 4.0 International License.

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  11. Synthesis and characterization of silver nanoparticles using Origanum onites leaves: Cytotoxic, apoptotic, and necrotic effects on Capan-1, L929, and Caco-2 cell lines
  12. Exergy analysis of a conceptual CO2 capture process with an amine-based DES
  13. Construction of fluorescence system of felodipine–tetracyanovinyl–2,2′-bipyridine complex
  14. Excellent photocatalytic degradation of rhodamine B over Bi2O3 supported on Zn-MOF nanocomposites under visible light
  15. Optimization-based control strategy for a large-scale polyhydroxyalkanoates production in a fed-batch bioreactor using a coupled PDE–ODE system
  16. Effectiveness of pH and amount of Artemia urumiana extract on physical, chemical, and biological attributes of UV-fabricated biogold nanoparticles
  17. Geranium leaf-mediated synthesis of silver nanoparticles and their transcriptomic effects on Candida albicans
  18. Synthesis, characterization, anticancer, anti-inflammatory activities, and docking studies of 3,5-disubstituted thiadiazine-2-thiones
  19. Synthesis and stability of phospholipid-encapsulated nano-selenium
  20. Putative anti-proliferative effect of Indian mustard (Brassica juncea) seed and its nano-formulation
  21. Enrichment of low-grade phosphorites by the selective leaching method
  22. Electrochemical analysis of the dissolution of gold in a copper–ethylenediamine–thiosulfate system
  23. Characterisation of carbonate lake sediments as a potential filler for polymer composites
  24. Evaluation of nano-selenium biofortification characteristics of alfalfa (Medicago sativa L.)
  25. Quality of oil extracted by cold press from Nigella sativa seeds incorporated with rosemary extracts and pretreated by microwaves
  26. Heteropolyacid-loaded MOF-derived mesoporous zirconia catalyst for chemical degradation of rhodamine B
  27. Recovery of critical metals from carbonatite-type mineral wastes: Geochemical modeling investigation of (bio)hydrometallurgical leaching of REEs
  28. Photocatalytic properties of ZnFe-mixed oxides synthesized via a simple route for water remediation
  29. Attenuation of di(2-ethylhexyl)phthalate-induced hepatic and renal toxicity by naringin nanoparticles in a rat model
  30. Novel in situ synthesis of quaternary core–shell metallic sulfide nanocomposites for degradation of organic dyes and hydrogen production
  31. Microfluidic steam-based synthesis of luminescent carbon quantum dots as sensing probes for nitrite detection
  32. Transformation of eggshell waste to egg white protein solution, calcium chloride dihydrate, and eggshell membrane powder
  33. Preparation of Zr-MOFs for the adsorption of doxycycline hydrochloride from wastewater
  34. Green nanoarchitectonics of the silver nanocrystal potential for treating malaria and their cytotoxic effects on the kidney Vero cell line
  35. Carbon emissions analysis of producing modified asphalt with natural asphalt
  36. An efficient and green synthesis of 2-phenylquinazolin-4(3H)-ones via t-BuONa-mediated oxidative condensation of 2-aminobenzamides and benzyl alcohols under solvent- and transition metal-free conditions
  37. Chitosan nanoparticles loaded with mesosulfuron methyl and mesosulfuron methyl + florasulam + MCPA isooctyl to manage weeds of wheat (Triticum aestivum L.)
  38. Synergism between lignite and high-sulfur petroleum coke in CO2 gasification
  39. Facile aqueous synthesis of ZnCuInS/ZnS–ZnS QDs with enhanced photoluminescence lifetime for selective detection of Cu(ii) ions
  40. Rapid synthesis of copper nanoparticles using Nepeta cataria leaves: An eco-friendly management of disease-causing vectors and bacterial pathogens
  41. Study on the photoelectrocatalytic activity of reduced TiO2 nanotube films for removal of methyl orange
  42. Development of a fuzzy logic model for the prediction of spark-ignition engine performance and emission for gasoline–ethanol blends
  43. Micro-impact-induced mechano-chemical synthesis of organic precursors from FeC/FeN and carbonates/nitrates in water and its extension to nucleobases
  44. Green synthesis of strontium-doped tin dioxide (SrSnO2) nanoparticles using the Mahonia bealei leaf extract and evaluation of their anticancer and antimicrobial activities
  45. A study on the larvicidal and adulticidal potential of Cladostepus spongiosus macroalgae and green-fabricated silver nanoparticles against mosquito vectors
  46. Catalysts based on nickel salt heteropolytungstates for selective oxidation of diphenyl sulfide
  47. Powerful antibacterial nanocomposites from Corallina officinalis-mediated nanometals and chitosan nanoparticles against fish-borne pathogens
  48. Removal behavior of Zn and alkalis from blast furnace dust in pre-reduction sinter process
  49. Environmentally friendly synthesis and computational studies of novel class of acridinedione integrated spirothiopyrrolizidines/indolizidines
  50. The mechanisms of inhibition and lubrication of clean fracturing flowback fluids in water-based drilling fluids
  51. Adsorption/desorption performance of cellulose membrane for Pb(ii)
  52. A one-pot, multicomponent tandem synthesis of fused polycyclic pyrrolo[3,2-c]quinolinone/pyrrolizino[2,3-c]quinolinone hybrid heterocycles via environmentally benign solid state melt reaction
  53. Green synthesis of silver nanoparticles using durian rind extract and optical characteristics of surface plasmon resonance-based optical sensor for the detection of hydrogen peroxide
  54. Electrochemical analysis of copper-EDTA-ammonia-gold thiosulfate dissolution system
  55. Characterization of bio-oil production by microwave pyrolysis from cashew nut shells and Cassia fistula pods
  56. Green synthesis methods and characterization of bacterial cellulose/silver nanoparticle composites
  57. Photocatalytic research performance of zinc oxide/graphite phase carbon nitride catalyst and its application in environment
  58. Effect of phytogenic iron nanoparticles on the bio-fortification of wheat varieties
  59. In vitro anti-cancer and antimicrobial effects of manganese oxide nanoparticles synthesized using the Glycyrrhiza uralensis leaf extract on breast cancer cell lines
  60. Preparation of Pd/Ce(F)-MCM-48 catalysts and their catalytic performance of n-heptane isomerization
  61. Green “one-pot” fluorescent bis-indolizine synthesis with whole-cell plant biocatalysis
  62. Silica-titania mesoporous silicas of MCM-41 type as effective catalysts and photocatalysts for selective oxidation of diphenyl sulfide by H2O2
  63. Biosynthesis of zinc oxide nanoparticles from molted feathers of Pavo cristatus and their antibiofilm and anticancer activities
  64. Clean preparation of rutile from Ti-containing mixed molten slag by CO2 oxidation
  65. Synthesis and characterization of Pluronic F-127-coated titanium dioxide nanoparticles synthesized from extracts of Atractylodes macrocephala leaf for antioxidant, antimicrobial, and anticancer properties
  66. Effect of pretreatment with alkali on the anaerobic digestion characteristics of kitchen waste and analysis of microbial diversity
  67. Ameliorated antimicrobial, antioxidant, and anticancer properties by Plectranthus vettiveroides root extract-mediated green synthesis of chitosan nanoparticles
  68. Microwave-accelerated pretreatment technique in green extraction of oil and bioactive compounds from camelina seeds: Effectiveness and characterization
  69. Studies on the extraction performance of phorate by aptamer-functionalized magnetic nanoparticles in plasma samples
  70. Investigation of structural properties and antibacterial activity of AgO nanoparticle extract from Solanum nigrum/Mentha leaf extracts by green synthesis method
  71. Green fabrication of chitosan from marine crustaceans and mushroom waste: Toward sustainable resource utilization
  72. Synthesis, characterization, and evaluation of nanoparticles of clodinofop propargyl and fenoxaprop-P-ethyl on weed control, growth, and yield of wheat (Triticum aestivum L.)
  73. The enhanced adsorption properties of phosphorus from aqueous solutions using lanthanum modified synthetic zeolites
  74. Separation of graphene oxides of different sizes by multi-layer dialysis and anti-friction and lubrication performance
  75. Visible-light-assisted base-catalyzed, one-pot synthesis of highly functionalized cinnolines
  76. The experimental study on the air oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid with Co–Mn–Br system
  77. Highly efficient removal of tetracycline and methyl violet 2B from aqueous solution using the bimetallic FeZn-ZIFs catalyst
  78. A thermo-tolerant cellulase enzyme produced by Bacillus amyloliquefaciens M7, an insight into synthesis, optimization, characterization, and bio-polishing activity
  79. Exploration of ketone derivatives of succinimide for their antidiabetic potential: In vitro and in vivo approaches
  80. Ultrasound-assisted green synthesis and in silico study of 6-(4-(butylamino)-6-(diethylamino)-1,3,5-triazin-2-yl)oxypyridazine derivatives
  81. A study of the anticancer potential of Pluronic F-127 encapsulated Fe2O3 nanoparticles derived from Berberis vulgaris extract
  82. Biogenic synthesis of silver nanoparticles using Consolida orientalis flowers: Identification, catalytic degradation, and biological effect
  83. Initial assessment of the presence of plastic waste in some coastal mangrove forests in Vietnam
  84. Adsorption synergy electrocatalytic degradation of phenol by active oxygen-containing species generated in Co-coal based cathode and graphite anode
  85. Antibacterial, antifungal, antioxidant, and cytotoxicity activities of the aqueous extract of Syzygium aromaticum-mediated synthesized novel silver nanoparticles
  86. Synthesis of a silica matrix with ZnO nanoparticles for the fabrication of a recyclable photodegradation system to eliminate methylene blue dye
  87. Natural polymer fillers instead of dye and pigments: Pumice and scoria in PDMS fluid and elastomer composites
  88. Study on the preparation of glycerylphosphorylcholine by transesterification under supported sodium methoxide
  89. Wireless network handheld terminal-based green ecological sustainable design evaluation system: Improved data communication and reduced packet loss rate
  90. The optimization of hydrogel strength from cassava starch using oxidized sucrose as a crosslinking agent
  91. Green synthesis of silver nanoparticles using Saccharum officinarum leaf extract for antiviral paint
  92. Study on the reliability of nano-silver-coated tin solder joints for flip chips
  93. Environmentally sustainable analytical quality by design aided RP-HPLC method for the estimation of brilliant blue in commercial food samples employing a green-ultrasound-assisted extraction technique
  94. Anticancer and antimicrobial potential of zinc/sodium alginate/polyethylene glycol/d-pinitol nanocomposites against osteosarcoma MG-63 cells
  95. Nanoporous carbon@CoFe2O4 nanocomposite as a green absorbent for the adsorptive removal of Hg(ii) from aqueous solutions
  96. Characterization of silver sulfide nanoparticles from actinobacterial strain (M10A62) and its toxicity against lepidopteran and dipterans insect species
  97. Phyto-fabrication and characterization of silver nanoparticles using Withania somnifera: Investigating antioxidant potential
  98. Effect of e-waste nanofillers on the mechanical, thermal, and wear properties of epoxy-blend sisal woven fiber-reinforced composites
  99. Magnesium nanohydroxide (2D brucite) as a host matrix for thymol and carvacrol: Synthesis, characterization, and inhibition of foodborne pathogens
  100. Synergistic inhibitive effect of a hybrid zinc oxide-benzalkonium chloride composite on the corrosion of carbon steel in a sulfuric acidic solution
  101. Review Articles
  102. Role and the importance of green approach in biosynthesis of nanopropolis and effectiveness of propolis in the treatment of COVID-19 pandemic
  103. Gum tragacanth-mediated synthesis of metal nanoparticles, characterization, and their applications as a bactericide, catalyst, antioxidant, and peroxidase mimic
  104. Green-processed nano-biocomposite (ZnO–TiO2): Potential candidates for biomedical applications
  105. Reaction mechanisms in microwave-assisted lignin depolymerisation in hydrogen-donating solvents
  106. Recent progress on non-noble metal catalysts for the deoxydehydration of biomass-derived oxygenates
  107. Rapid Communication
  108. Phosphorus removal by iron–carbon microelectrolysis: A new way to achieve phosphorus recovery
  109. Special Issue: Biomolecules-derived synthesis of nanomaterials for environmental and biological applications (Guest Editors: Arpita Roy and Fernanda Maria Policarpo Tonelli)
  110. Biomolecules-derived synthesis of nanomaterials for environmental and biological applications
  111. Nano-encapsulated tanshinone IIA in PLGA-PEG-COOH inhibits apoptosis and inflammation in cerebral ischemia/reperfusion injury
  112. Green fabrication of silver nanoparticles using Melia azedarach ripened fruit extract, their characterization, and biological properties
  113. Green-synthesized nanoparticles and their therapeutic applications: A review
  114. Antioxidant, antibacterial, and cytotoxicity potential of synthesized silver nanoparticles from the Cassia alata leaf aqueous extract
  115. Green synthesis of silver nanoparticles using Callisia fragrans leaf extract and its anticancer activity against MCF-7, HepG2, KB, LU-1, and MKN-7 cell lines
  116. Algae-based green AgNPs, AuNPs, and FeNPs as potential nanoremediators
  117. Green synthesis of Kickxia elatine-induced silver nanoparticles and their role as anti-acetylcholinesterase in the treatment of Alzheimer’s disease
  118. Phytocrystallization of silver nanoparticles using Cassia alata flower extract for effective control of fungal skin pathogens
  119. Antibacterial wound dressing with hydrogel from chitosan and polyvinyl alcohol from the red cabbage extract loaded with silver nanoparticles
  120. Leveraging of mycogenic copper oxide nanostructures for disease management of Alternaria blight of Brassica juncea
  121. Nanoscale molecular reactions in microbiological medicines in modern medical applications
  122. Synthesis and characterization of ZnO/β-cyclodextrin/nicotinic acid nanocomposite and its biological and environmental application
  123. Green synthesis of silver nanoparticles via Taxus wallichiana Zucc. plant-derived Taxol: Novel utilization as anticancer, antioxidation, anti-inflammation, and antiurolithic potential
  124. Recyclability and catalytic characteristics of copper oxide nanoparticles derived from bougainvillea plant flower extract for biomedical application
  125. Phytofabrication, characterization, and evaluation of novel bioinspired selenium–iron (Se–Fe) nanocomposites using Allium sativum extract for bio-potential applications
  126. Erratum
  127. Erratum to “Synthesis, characterization, and evaluation of nanoparticles of clodinofop propargyl and fenoxaprop-P-ethyl on weed control, growth, and yield of wheat (Triticum aestivum L.)”
https://doi.org/10.1515/gps-2023-0066
Keywords for this article
Pd/Ce (F)-MCM-48 catalyst; fluorine; cerium; n-heptane; isomerization
Creative Commons
BY 4.0

Articles in the same Issue

  1. Research Articles
  2. Value-added utilization of coal fly ash and recycled polyvinyl chloride in door or window sub-frame composites
  3. High removal efficiency of volatile phenol from coking wastewater using coal gasification slag via optimized adsorption and multi-grade batch process
  4. Evolution of surface morphology and properties of diamond films by hydrogen plasma etching
  5. Removal efficiency of dibenzofuran using CuZn-zeolitic imidazole frameworks as a catalyst and adsorbent
  6. Rapid and efficient microwave-assisted extraction of Caesalpinia sappan Linn. heartwood and subsequent synthesis of gold nanoparticles
  7. The catalytic characteristics of 2-methylnaphthalene acylation with AlCl3 immobilized on Hβ as Lewis acid catalyst
  8. Biodegradation of synthetic PVP biofilms using natural materials and nanoparticles
  9. Rutin-loaded selenium nanoparticles modulated the redox status, inflammatory, and apoptotic pathways associated with pentylenetetrazole-induced epilepsy in mice
  10. Optimization of apigenin nanoparticles prepared by planetary ball milling: In vitro and in vivo studies
  11. Synthesis and characterization of silver nanoparticles using Origanum onites leaves: Cytotoxic, apoptotic, and necrotic effects on Capan-1, L929, and Caco-2 cell lines
  12. Exergy analysis of a conceptual CO2 capture process with an amine-based DES
  13. Construction of fluorescence system of felodipine–tetracyanovinyl–2,2′-bipyridine complex
  14. Excellent photocatalytic degradation of rhodamine B over Bi2O3 supported on Zn-MOF nanocomposites under visible light
  15. Optimization-based control strategy for a large-scale polyhydroxyalkanoates production in a fed-batch bioreactor using a coupled PDE–ODE system
  16. Effectiveness of pH and amount of Artemia urumiana extract on physical, chemical, and biological attributes of UV-fabricated biogold nanoparticles
  17. Geranium leaf-mediated synthesis of silver nanoparticles and their transcriptomic effects on Candida albicans
  18. Synthesis, characterization, anticancer, anti-inflammatory activities, and docking studies of 3,5-disubstituted thiadiazine-2-thiones
  19. Synthesis and stability of phospholipid-encapsulated nano-selenium
  20. Putative anti-proliferative effect of Indian mustard (Brassica juncea) seed and its nano-formulation
  21. Enrichment of low-grade phosphorites by the selective leaching method
  22. Electrochemical analysis of the dissolution of gold in a copper–ethylenediamine–thiosulfate system
  23. Characterisation of carbonate lake sediments as a potential filler for polymer composites
  24. Evaluation of nano-selenium biofortification characteristics of alfalfa (Medicago sativa L.)
  25. Quality of oil extracted by cold press from Nigella sativa seeds incorporated with rosemary extracts and pretreated by microwaves
  26. Heteropolyacid-loaded MOF-derived mesoporous zirconia catalyst for chemical degradation of rhodamine B
  27. Recovery of critical metals from carbonatite-type mineral wastes: Geochemical modeling investigation of (bio)hydrometallurgical leaching of REEs
  28. Photocatalytic properties of ZnFe-mixed oxides synthesized via a simple route for water remediation
  29. Attenuation of di(2-ethylhexyl)phthalate-induced hepatic and renal toxicity by naringin nanoparticles in a rat model
  30. Novel in situ synthesis of quaternary core–shell metallic sulfide nanocomposites for degradation of organic dyes and hydrogen production
  31. Microfluidic steam-based synthesis of luminescent carbon quantum dots as sensing probes for nitrite detection
  32. Transformation of eggshell waste to egg white protein solution, calcium chloride dihydrate, and eggshell membrane powder
  33. Preparation of Zr-MOFs for the adsorption of doxycycline hydrochloride from wastewater
  34. Green nanoarchitectonics of the silver nanocrystal potential for treating malaria and their cytotoxic effects on the kidney Vero cell line
  35. Carbon emissions analysis of producing modified asphalt with natural asphalt
  36. An efficient and green synthesis of 2-phenylquinazolin-4(3H)-ones via t-BuONa-mediated oxidative condensation of 2-aminobenzamides and benzyl alcohols under solvent- and transition metal-free conditions
  37. Chitosan nanoparticles loaded with mesosulfuron methyl and mesosulfuron methyl + florasulam + MCPA isooctyl to manage weeds of wheat (Triticum aestivum L.)
  38. Synergism between lignite and high-sulfur petroleum coke in CO2 gasification
  39. Facile aqueous synthesis of ZnCuInS/ZnS–ZnS QDs with enhanced photoluminescence lifetime for selective detection of Cu(ii) ions
  40. Rapid synthesis of copper nanoparticles using Nepeta cataria leaves: An eco-friendly management of disease-causing vectors and bacterial pathogens
  41. Study on the photoelectrocatalytic activity of reduced TiO2 nanotube films for removal of methyl orange
  42. Development of a fuzzy logic model for the prediction of spark-ignition engine performance and emission for gasoline–ethanol blends
  43. Micro-impact-induced mechano-chemical synthesis of organic precursors from FeC/FeN and carbonates/nitrates in water and its extension to nucleobases
  44. Green synthesis of strontium-doped tin dioxide (SrSnO2) nanoparticles using the Mahonia bealei leaf extract and evaluation of their anticancer and antimicrobial activities
  45. A study on the larvicidal and adulticidal potential of Cladostepus spongiosus macroalgae and green-fabricated silver nanoparticles against mosquito vectors
  46. Catalysts based on nickel salt heteropolytungstates for selective oxidation of diphenyl sulfide
  47. Powerful antibacterial nanocomposites from Corallina officinalis-mediated nanometals and chitosan nanoparticles against fish-borne pathogens
  48. Removal behavior of Zn and alkalis from blast furnace dust in pre-reduction sinter process
  49. Environmentally friendly synthesis and computational studies of novel class of acridinedione integrated spirothiopyrrolizidines/indolizidines
  50. The mechanisms of inhibition and lubrication of clean fracturing flowback fluids in water-based drilling fluids
  51. Adsorption/desorption performance of cellulose membrane for Pb(ii)
  52. A one-pot, multicomponent tandem synthesis of fused polycyclic pyrrolo[3,2-c]quinolinone/pyrrolizino[2,3-c]quinolinone hybrid heterocycles via environmentally benign solid state melt reaction
  53. Green synthesis of silver nanoparticles using durian rind extract and optical characteristics of surface plasmon resonance-based optical sensor for the detection of hydrogen peroxide
  54. Electrochemical analysis of copper-EDTA-ammonia-gold thiosulfate dissolution system
  55. Characterization of bio-oil production by microwave pyrolysis from cashew nut shells and Cassia fistula pods
  56. Green synthesis methods and characterization of bacterial cellulose/silver nanoparticle composites
  57. Photocatalytic research performance of zinc oxide/graphite phase carbon nitride catalyst and its application in environment
  58. Effect of phytogenic iron nanoparticles on the bio-fortification of wheat varieties
  59. In vitro anti-cancer and antimicrobial effects of manganese oxide nanoparticles synthesized using the Glycyrrhiza uralensis leaf extract on breast cancer cell lines
  60. Preparation of Pd/Ce(F)-MCM-48 catalysts and their catalytic performance of n-heptane isomerization
  61. Green “one-pot” fluorescent bis-indolizine synthesis with whole-cell plant biocatalysis
  62. Silica-titania mesoporous silicas of MCM-41 type as effective catalysts and photocatalysts for selective oxidation of diphenyl sulfide by H2O2
  63. Biosynthesis of zinc oxide nanoparticles from molted feathers of Pavo cristatus and their antibiofilm and anticancer activities
  64. Clean preparation of rutile from Ti-containing mixed molten slag by CO2 oxidation
  65. Synthesis and characterization of Pluronic F-127-coated titanium dioxide nanoparticles synthesized from extracts of Atractylodes macrocephala leaf for antioxidant, antimicrobial, and anticancer properties
  66. Effect of pretreatment with alkali on the anaerobic digestion characteristics of kitchen waste and analysis of microbial diversity
  67. Ameliorated antimicrobial, antioxidant, and anticancer properties by Plectranthus vettiveroides root extract-mediated green synthesis of chitosan nanoparticles
  68. Microwave-accelerated pretreatment technique in green extraction of oil and bioactive compounds from camelina seeds: Effectiveness and characterization
  69. Studies on the extraction performance of phorate by aptamer-functionalized magnetic nanoparticles in plasma samples
  70. Investigation of structural properties and antibacterial activity of AgO nanoparticle extract from Solanum nigrum/Mentha leaf extracts by green synthesis method
  71. Green fabrication of chitosan from marine crustaceans and mushroom waste: Toward sustainable resource utilization
  72. Synthesis, characterization, and evaluation of nanoparticles of clodinofop propargyl and fenoxaprop-P-ethyl on weed control, growth, and yield of wheat (Triticum aestivum L.)
  73. The enhanced adsorption properties of phosphorus from aqueous solutions using lanthanum modified synthetic zeolites
  74. Separation of graphene oxides of different sizes by multi-layer dialysis and anti-friction and lubrication performance
  75. Visible-light-assisted base-catalyzed, one-pot synthesis of highly functionalized cinnolines
  76. The experimental study on the air oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid with Co–Mn–Br system
  77. Highly efficient removal of tetracycline and methyl violet 2B from aqueous solution using the bimetallic FeZn-ZIFs catalyst
  78. A thermo-tolerant cellulase enzyme produced by Bacillus amyloliquefaciens M7, an insight into synthesis, optimization, characterization, and bio-polishing activity
  79. Exploration of ketone derivatives of succinimide for their antidiabetic potential: In vitro and in vivo approaches
  80. Ultrasound-assisted green synthesis and in silico study of 6-(4-(butylamino)-6-(diethylamino)-1,3,5-triazin-2-yl)oxypyridazine derivatives
  81. A study of the anticancer potential of Pluronic F-127 encapsulated Fe2O3 nanoparticles derived from Berberis vulgaris extract
  82. Biogenic synthesis of silver nanoparticles using Consolida orientalis flowers: Identification, catalytic degradation, and biological effect
  83. Initial assessment of the presence of plastic waste in some coastal mangrove forests in Vietnam
  84. Adsorption synergy electrocatalytic degradation of phenol by active oxygen-containing species generated in Co-coal based cathode and graphite anode
  85. Antibacterial, antifungal, antioxidant, and cytotoxicity activities of the aqueous extract of Syzygium aromaticum-mediated synthesized novel silver nanoparticles
  86. Synthesis of a silica matrix with ZnO nanoparticles for the fabrication of a recyclable photodegradation system to eliminate methylene blue dye
  87. Natural polymer fillers instead of dye and pigments: Pumice and scoria in PDMS fluid and elastomer composites
  88. Study on the preparation of glycerylphosphorylcholine by transesterification under supported sodium methoxide
  89. Wireless network handheld terminal-based green ecological sustainable design evaluation system: Improved data communication and reduced packet loss rate
  90. The optimization of hydrogel strength from cassava starch using oxidized sucrose as a crosslinking agent
  91. Green synthesis of silver nanoparticles using Saccharum officinarum leaf extract for antiviral paint
  92. Study on the reliability of nano-silver-coated tin solder joints for flip chips
  93. Environmentally sustainable analytical quality by design aided RP-HPLC method for the estimation of brilliant blue in commercial food samples employing a green-ultrasound-assisted extraction technique
  94. Anticancer and antimicrobial potential of zinc/sodium alginate/polyethylene glycol/d-pinitol nanocomposites against osteosarcoma MG-63 cells
  95. Nanoporous carbon@CoFe2O4 nanocomposite as a green absorbent for the adsorptive removal of Hg(ii) from aqueous solutions
  96. Characterization of silver sulfide nanoparticles from actinobacterial strain (M10A62) and its toxicity against lepidopteran and dipterans insect species
  97. Phyto-fabrication and characterization of silver nanoparticles using Withania somnifera: Investigating antioxidant potential
  98. Effect of e-waste nanofillers on the mechanical, thermal, and wear properties of epoxy-blend sisal woven fiber-reinforced composites
  99. Magnesium nanohydroxide (2D brucite) as a host matrix for thymol and carvacrol: Synthesis, characterization, and inhibition of foodborne pathogens
  100. Synergistic inhibitive effect of a hybrid zinc oxide-benzalkonium chloride composite on the corrosion of carbon steel in a sulfuric acidic solution
  101. Review Articles
  102. Role and the importance of green approach in biosynthesis of nanopropolis and effectiveness of propolis in the treatment of COVID-19 pandemic
  103. Gum tragacanth-mediated synthesis of metal nanoparticles, characterization, and their applications as a bactericide, catalyst, antioxidant, and peroxidase mimic
  104. Green-processed nano-biocomposite (ZnO–TiO2): Potential candidates for biomedical applications
  105. Reaction mechanisms in microwave-assisted lignin depolymerisation in hydrogen-donating solvents
  106. Recent progress on non-noble metal catalysts for the deoxydehydration of biomass-derived oxygenates
  107. Rapid Communication
  108. Phosphorus removal by iron–carbon microelectrolysis: A new way to achieve phosphorus recovery
  109. Special Issue: Biomolecules-derived synthesis of nanomaterials for environmental and biological applications (Guest Editors: Arpita Roy and Fernanda Maria Policarpo Tonelli)
  110. Biomolecules-derived synthesis of nanomaterials for environmental and biological applications
  111. Nano-encapsulated tanshinone IIA in PLGA-PEG-COOH inhibits apoptosis and inflammation in cerebral ischemia/reperfusion injury
  112. Green fabrication of silver nanoparticles using Melia azedarach ripened fruit extract, their characterization, and biological properties
  113. Green-synthesized nanoparticles and their therapeutic applications: A review
  114. Antioxidant, antibacterial, and cytotoxicity potential of synthesized silver nanoparticles from the Cassia alata leaf aqueous extract
  115. Green synthesis of silver nanoparticles using Callisia fragrans leaf extract and its anticancer activity against MCF-7, HepG2, KB, LU-1, and MKN-7 cell lines
  116. Algae-based green AgNPs, AuNPs, and FeNPs as potential nanoremediators
  117. Green synthesis of Kickxia elatine-induced silver nanoparticles and their role as anti-acetylcholinesterase in the treatment of Alzheimer’s disease
  118. Phytocrystallization of silver nanoparticles using Cassia alata flower extract for effective control of fungal skin pathogens
  119. Antibacterial wound dressing with hydrogel from chitosan and polyvinyl alcohol from the red cabbage extract loaded with silver nanoparticles
  120. Leveraging of mycogenic copper oxide nanostructures for disease management of Alternaria blight of Brassica juncea
  121. Nanoscale molecular reactions in microbiological medicines in modern medical applications
  122. Synthesis and characterization of ZnO/β-cyclodextrin/nicotinic acid nanocomposite and its biological and environmental application
  123. Green synthesis of silver nanoparticles via Taxus wallichiana Zucc. plant-derived Taxol: Novel utilization as anticancer, antioxidation, anti-inflammation, and antiurolithic potential
  124. Recyclability and catalytic characteristics of copper oxide nanoparticles derived from bougainvillea plant flower extract for biomedical application
  125. Phytofabrication, characterization, and evaluation of novel bioinspired selenium–iron (Se–Fe) nanocomposites using Allium sativum extract for bio-potential applications
  126. Erratum
  127. Erratum to “Synthesis, characterization, and evaluation of nanoparticles of clodinofop propargyl and fenoxaprop-P-ethyl on weed control, growth, and yield of wheat (Triticum aestivum L.)”
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