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Synthesis of vitamin E succinate catalyzed by nano-SiO2 immobilized DMAP derivative in mixed solvent system

  • Dan Chen , Binglin Li , Bin Li , Xiaoli Zhang EMAIL logo , Longhui Wei and Wenwen Zheng
Published/Copyright: July 13, 2019
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Green Processing and Synthesis
From the journal Green Processing and Synthesis Volume 8 Issue 1

Abstract

Catalytic efficiency in synthesis of vitamin E succinate was dramatically increased via the preparation of robust catalyst and the improvement of reaction system. 4-dimethylaminopyridine (DMAP) was covalently immobilized on nano-SiO2 to avoid the catalyst contamination of the product and permit the easy recycling of DMAP. Then, a hexane-acetone mixed solvent system was firstly introduced to replace the traditional single-solvent system, which was employed to improve the activity of immobilized DMAP derivative and the substrate solubility of the reaction system. The highest vitamin E succinate yield of 94% was achieved. In addition, the recyclability and stability of the immobilized DMAP derivative was excellent, the yield of vitamin E succinate had no obvious loss and remained 90% after recycling 20 times. The excellent results make this technology be a promising candidate for the industrial production of vitamin E succinate.

Keywords: vitamin E succinate; nano-SiO2; 4-dimethylaminopyridine (DMAP); immobilization; mixed solvent system

1 Introduction

Vitamin E as antioxidant has many applications in the treatment of cardiovascular disease, microvascular and hypercholesterolemia [1, 2, 3]. However, vitamin E is unstable and its antioxidant value is easily reduced by light, air, oxidizing agent and heat [4,5]. Therefore, many researchers have devoted to increase its stability and developed many relevant derivatives. In all kinds of vitamin E, α-tocopherol is the most representative isoform, which shows the highest vitamin E activity [6,7]. To increase its stability, many relevant α-tocopherol derivatives have been developed [8]. As reported, α-tocopherol succinate was the most biologically and chemically active, in which the original hydroxyl of α-tocopherol was converted to the succinic anhydride ring-opened carboxyl group. The obtained α-tocopherol succinate showed the great stability and the excellent performance as the antioxidant. In addition, the pharmacological effects of α-tocopherol succinate have been also confirmed in animal experiments and clinical researches with the treatments of cancer and cataract [9, 10, 11, 12, 13, 14].

Generally, α-tocopherol succinate was prepared by enzymatic or chemical synthesis. For example, it has reported that α-tocopherol succinate was obtained over modified Novozym-435 lipase-catalyzed reaction [15]. However, the unsatisfactory stability and high cost of enzyme were the serious problems of biocatalytic approaches. Recently, ionic liquids were employed for the synthesis of α-tocopherol succinate [16]. A serious drawback of the system was the complicated process of separation of the product. And the expensive price of ionic liquids was another limiting factor for future industrial production. So far, a variety of organic catalysts were widely used for the synthesis of α-tocopherol derivatives, which was involved in DMAP, tertiary amine and pyridine [17,18]. Among these catalysts, DMAP was deemed as the best candidate due to its high catalytic activity and great reaction selectivity. However, the application of DMAP for industrial production was easily limited by the problem of difficulty in separating from the solvent. In addition, it has reported that the toxicity of DMAP made it inappropriate for production of food and medicine [19]. With regard to α-tocopherol derivatives as medicine for human being, the DMAP contamination of the product should be avoided.

In the present work, DMAP was covalently immobilized on the surface of nano-SiO2 to prepare a robust catalyst for the synthesis of α-tocopherol succinate. The obtained immobilized DMAP derivative permitted the easy separation of catalyst from the product, avoiding DMAP contamination and raising the safety of the product. Moreover, the immobilization also provided a promising way for the easy recycling of DMAP, which can reduce the production cost significantly. It is worth noting that nano-SiO2 was a kind of inexpensive nanoparticles (NPs) with unique properties including large area, suitable density and great mechanical properties [20,21]. Thus, the use of nano-SiO2 was adequate for the properties of carrier.

The reaction solvent is another crucial factor affecting the catalytic performance of the reaction system. It has reported that a high-polar solvent presumably promoted the protonation of DMAP by intermediate by-product acid, which would result in the deactivation of DMAP. [22,23]. However, the solubility of succinic anhydride increased with increasing the polarity of solvent. Therefore, it was very hard to obtain a balance between catalyst activity and substrates solubility just through the single solvent. Herein, α-tocopherol succinate was efficiently synthesized in the mixed solvent system using immobilized DMAP derivative. The mixed solvent consisted of hexane and acetone, the less-polar hexane was used to improve the activity of catalyst and the high-polar acetone was to increase the solubility of succinic anhydride. Moreover, hexane and acetone belonging to class 3 residual solvents were promising candidates toward environmentally friendly solvents due to their no health-based exposure limit and low toxicity [24]. In addition, the phase resistance was also avoided due to the miscible property of two solvents. Comparing with other reported approaches, we developed a promising way for the industrial production of α-tocopherol succinate, which completely avoided the catalyst contamination and significantly enhanced the safety of product.

2 Materials and methods

2.1 Materials

Succinic anhydride, α-tocopherol, nano-SiO2, 30 nm diameter, γ-chloropropyltrimethoxysilane (CPTMS) and 4-methylaminopyridine (MAP) were obtained from Aladdin Chemistry Co., Ltd (Shanghai, China), all other reagents and salts were standard laboratory grade.

2.2 Preparation of γ-chloropropyl-functionalized nano-SiO2 particles (NS-Cl)

The γ-chloropropyltrimethoxysiliane (CPTMS) was covalently bonded on the surface of nano-SiO2 particles. Five grams of nano-SiO2 was added in 70 mL absolute ethanol/water (4:1 volume ratio). Then, 5 mL γ-chloropropyltrimethoxysiliane (CPTMS) was added, and the reaction mixture was stirred for 24 h at room temperature. the resulting γ-chloropropyl-functionalized nano-SiO2 was separated by centrifugation and washed with 40 mL deionized water for 4 times. Finally, the pure γ-chloropropyl-functionalized nano-SiO2 was dried at 60°C for 12 h under vacuum.

2.3 Preparation of nano-SiO2 immobilized DMAP derivative (NS-DMAP)

Nano-SiO2 immobilized DMAP derivative catalyst was prepared as follows: 0.90 mmol 4-methylaminopyridine (MAP) was dissolved in 25 mL o-xylene. Then, 0.40 g nano-SiO2, 1.35 mmol K2CO3 and 0.90 mmol KI were added, and the reaction mixture was stirred at 120°C for 12 h under nitrogen. The reaction was monitored by HPLC. The loading capacity of DMAP was calculated by the content of free MAP before and after reaction. The resulting catalyst was separated by centrifugation and washed with o-xylene (3 × 15 mL), absolute ethanol (2 × 15 mL), deionized water (2 × 15 mL). Finally, the pure immobilized DMAP derivative was dried at 60°C for 12 h under vacuum.

2.4 Synthesis of vitamin E succinate

Vitamin E succinate was synthesized in mixed solvent using immobilized DMAP derivative. The details were as follows: 0.15 mmol α-tocopherol was dissolved in 5 mL mixed solvent (hexane/acetone). Then, 0.45 mmol succinic anhydride, 0.1 mmol NS-DMAP (the molar amount of DMAP that covalently bonded on nano-SiO2) was added, and the reaction mixture was stirred at the setting temperature for 24 h under N2 atmosphere. After reaction, the reaction mixture was cooled and filtered to regenerate nano-SiO2 immobilized DMAP derivative. Small amount of filtrate was analyzed by HPLC to determine the yield of α-tocopherol succinate. The other filtrate was concentrated under vacuum and then diethyl ether was added to remove unreacted succinic anhydride under low temperature, the crude product was purified by hexane to obtain the pure α-tocopherol succinate.

2.5 HPLC analysis

Analysis of reaction solution was performed on a Shimadzu LC-20A HPLC system (Shimadzu, Japan). The detector was SPDFSPD-20A Ultraviolet-Visible Detection Device. HPLC analysis of supernatant of catalytic reaction was carried out under UV wavelength of 254 nm. The column was a BDS Hypersil C18 stainless steel column (250 × 4.6 mm), and the column temperature was 40°C. Mobile phase was chromatographic grade methanol/water/phosphoric acid (60:39.75:0.25 volume ratio) with a flow rate of l.0 mL/min. HPLC analysis of filtrate of acylation reaction was carried out under UV wavelength of 284 nm. The column was a Discovery C18 column (250 × 4.6 mm), and the column temperature was 40°C. Mobile phase was chromatographic grade methanol/ glacial acetic acid (500:3.2 volume ratio) with a flow rate of l.2 mL/ min.

2.6 NS-DMAP characterizations

Thermogravimetric analysis (TG) was performed with a Thermogravimetric analyzer (STA449F3, Netzsch, Germany). The measurement was carried out under N2 atmosphere at a uniform heating rate of 10°C/min from room temperature to 750°C. The Fourier Transform Infrared (FT-IR) spectroscopy was recorded on a Fourier transform infrared spectrometer (Frontier, PerkinElmer, America) in the range from 400 to 4000 cm-1.

3 Results and discussion

3.1 Catalyst preparation

The rationale of immobilizing DMAP derivative on nano-SiO2 was a two-step process described in Figure 1. First, the γ-chloropropyltrimethoxysiliane (CPTMS) was covalently coupled on the surface of nano-SiO2 particles for the preparation of γ-chloropropyl-functionalized nano-SiO2; next, 4-methylaminopyridine (MAP) reacted with the coupled chloropropyl and was covalently bonded on the modified nano-SiO2 over N-alkylation reaction, which was promoted by KI and K2CO3.

Figure 1 Preparation of heterogeneous catalyst (NS-DMAP).
Figure 1

Preparation of heterogeneous catalyst (NS-DMAP).

To investigate the optimal loading capacity of DMAP, the effects of reaction temperature, KI and K2CO3 concentration and reaction time were investigated systematically. As shown in Figure 2, the reaction temperature of 120°C, a molar ratio of KI to MAP of 1:1, a molar ratio of K2CO3 to MAP of 1.5:1 and reaction time of 12 h were found to be the optimal conditions for the N-alkylation reaction. The maximum loading capacity of DMAP reached 0.68 mmol/ g under the optimal conditions.

Figure 2 The optimal conditions of N-alkylation reaction.
Figure 2

The optimal conditions of N-alkylation reaction.

3.2 Catalyst characterizations

Next, the obtained immobilized DMAP derivative was characterized in details. As shown in Figure 3, the weight loss of nanoparticles between 30°C and 750°C was observed by TG and DTG curves. For nano-SiO2 (NS), γ-chloropropyl-functionalized nano-SiO2 particles (NS-Cl) and nano-SiO2 immobilized DMAP derivative (NS-DMAP), the weight loss from 30 to 200°C was attributed to the desorption of physically absorbed water [25], which could be confirmed by the peak of DTG at 30 to 200°C. And another main weight loss was observed at 400°C to 600°C, which was ascribed to the decomposition of coupled CPTMS. Besides, DTG showed that the peak at 400 to 600°C only can be observed by NS-Cl and NS-DMAP, the result demonstrated that the CPTMS was successfully coupled on external surface of nano-SiO2. The last weight loss between 200 and 400°C was attributed to the decomposition of DMAP, and the characteristic peak of DTG only can be observed by NS-DMAP [26]. The results indicated that nano-SiO2 immobilized DMAP derivative has been successfully prepared.

Figure 3 TG, DTG curves of (1) NS, (2) NS-Cl, (3) NS-DMAP.
Figure 3

TG, DTG curves of (1) NS, (2) NS-Cl, (3) NS-DMAP.

To prove the structure of the catalyst, the FT-IR spectra of NS, NS-Cl and NS-DMAP was taken and shown in Figure 4. In all curves, the peaks at 1072 cm-1 and 796 cm-1 were assigned to the Si-O-Si asymmetric and symmetric stretching, respectively [27]. After γ-chloropropyl-functionalization of nano-SiO2, the peak corresponding to C-Cl stretching bond appeared at 653 cm-1, and the stretching peaks of alkyl C-H was clearly observed at 2981 cm-1 and 2891 cm-1 [28].

Figure 4 FT-IR spectra of (a) NS, (b) NS-Cl, (c) NS-DMAP.
Figure 4

FT-IR spectra of (a) NS, (b) NS-Cl, (c) NS-DMAP.

For the curve of NS-DMAP, the new characteristic peak at 1658 cm-1 was assigned to stretching bond of aromatic ring [26]. From the analysis of FT-IR, it can be ascertained that we have successfully prepared the catalyst.

3.3 Comparison of the catalytic effect of different carriers immobilized DMAP derivative

In order to investigate the role of carriers in the immobilization, DMAP was immobilized on several different carriers including nano-SiO2 (NS), silica gel (SG) and mesoporous crystalline material (MCM-41). The maximum loading capacity of NS-DMAP, SG-DMAP and MCM-DMAP reached 0.68 mmol/g, 0.89 mmol/g and 1.35 mmol/g, respectively. Then, the performances of three kinds of catalysts were systematically assessed in the synthesis of α-tocopherol succinate. Although the higher loading capacity was observed in preparation of SG-DMAP and MCM-DMAP, the highest catalytic activity was observed during the use of NS-DMAP. SG and MCM-41 with the porous structure had higher specific surface area. Thus, they showed higher DMAP loading capacity than NS. However, their small porous structure also accompanied by the serious internal resistance and reduced reaction rate. As shown in Figure 5, the initial reaction rate of NS-DMAP reached 1.5 mmol··molDMAP-1··min-1, which was more than twice the activity of other two catalysts. DMAP immobilized on the external surface of nonporous NS, which can completely eliminate the internal diffusion problem. More importantly, according to the Stokes-Einstein and collision theory, NS with a very smaller size can enhance the collision between catalysts and reaction substrates, which was the main resistance for substrates availability between the bulk solution and material surface particularly in a biphasic system [29,30]. After reaction, the leakage of DMAP was measured to investigate the stability of the immobilized DMAP derivative by HPLC [31]. The result indicated that the obtained immobilized DMAP derivative possessed the greater stability and completely avoided the DMAP contamination of product, raising the product safety.

Figure 5 Effect of different carriers. Conditions of reaction: 0.15 mmol α-tocopherol, 0.45 mmol succinic anhydride, hexane/acetone (4 mL/1 mL), DMAP equivalent to 0.10 mmol (the same below).
Figure 5

Effect of different carriers. Conditions of reaction: 0.15 mmol α-tocopherol, 0.45 mmol succinic anhydride, hexane/acetone (4 mL/1 mL), DMAP equivalent to 0.10 mmol (the same below).

3.4 Effect of organic solvents on yield of vitamin E succinate

The reaction solvent was a crucial factor affecting the catalytic performance [22]. Table 1 showed the effect of organic solvents on the yield of α-tocopherol succinate in the single solvent system. It was found that the yield of α-tocopherol succinate was higher in a less-polar solvent. The phenomenon was attributed to the significantly reduced amount of DMAP protonation in the less-polar solvent [22,23]. However, the lowest yield was observed in the lowest-polar petroleum ether. The main reason was that the solubility of succinic anhydride decreased with decreasing the polarity of solvent. Therefore, a small amount of succinic anhydride was dissolved in petroleum ether, which limited ring-opened reaction of

Table 1

Effect of different organic solvents.

organic solventssolvent polarityYield
petroleum ether0.015.56%
hexane0.0655.45%
toluene2.4030.91%
trichloromethane4.4025.87%
acetone5.4014.65%
dimethyl sulfoxide7.210.91%

  1. Conditions of reaction: 0.15 mmol α-tocopherol, 0.45 mmol succinic anhydride, 0.10 mmol NS-DMAP, 5 mL organic solvent described above, 55°C, nitrogen, 24 h.

succinic anhydride in the first step of mechanism reaction described in Figure 6, affecting the effectivity of the whole reaction [32,33].

Figure 6 Proposed mechanism for the synthesis of α-tocopherol succinate using NS-DMAP in hexane and acetone.
Figure 6

Proposed mechanism for the synthesis of α-tocopherol succinate using NS-DMAP in hexane and acetone.

Herein, a mixed solvent system was introduced for the synthesis of α-tocopherol succinate, which consisted of the less-polar organic solvent hexane and the high-polar organic solvent acetone. The less-polar hexane was used to mitigate DMAP protonation, preventing the deactivation of catalyst, and the high-polar acetone was to increase the solubility of succinic anhydride. Hexane and acetone were environmentally friendly solvents with the properties of no health-based exposure limit and low toxicity [24]. Besides, the phase resistance was also avoided due to the miscible property of two solvents. The mixed solvent system enhanced the activity of the whole system and the safety of product. As shown in Figure 7a, it was found that the yield of α-tocopherol succinate was higher in the mixed solvent system than single solvent system. The optimal volume ratio of hexane to acetone was confirmed as 4:1. Then, the reaction was carried out in four different systems, which was showed in Figure 7b. The result indicated that hexane-acetone mixed solvent system showed higher yields of α-tocopherol succinate and reaction rates comparing with hexane single solvent system in all cases no matter which form of DMAP was employed. Although free DMAP showed the highest catalytic activity in the mixed solvent among four reaction systems, the problem of separation limited its industrial applications. With regard to α-tocopherol succinate as medicine for human being, the DMAP contamination of the product should be avoided. Therefore, a highly efficient and environmentally friendly technology process for the synthesis of α-tocopherol succinate was employing nano-SiO2 immobilized DMAP derivative as catalyst and hexane-acetone mixed solvent as the reaction solvent. The initial reaction rate of 1.5 mmol··molDMAP-1··min-1 of NS-DMAP in mixed solvent was obviously higher than the highest initial reaction rate of 1.1 mmol··molDMAP-1··min-1 in single solvent. Besides, the contamination of DMAP can be completely avoided and this may be the first description of the remarkably high improvement of the efficiency of the production of α-tocopherol succinate.

Figure 7 (a) Effect of mixed solvent system; (b) Effect of different catalytic reaction system. Conditions of reaction: 0.15 mmol α-tocopherol, 0.45 mmol succinic anhydride, 0.10 mmol catalyst, hexane/acetone (4 mL/1 mL), 55°C, nitrogen, 16 h.
Figure 7

(a) Effect of mixed solvent system; (b) Effect of different catalytic reaction system. Conditions of reaction: 0.15 mmol α-tocopherol, 0.45 mmol succinic anhydride, 0.10 mmol catalyst, hexane/acetone (4 mL/1 mL), 55°C, nitrogen, 16 h.

3.5 Effect of molar ratio of substrates on yield of α-tocopherol succinate

The reaction equilibrium was easy to affect by substrates concentration. Therefore, an excess of succinic anhydride would be essential to shift the reaction equilibrium towards to the formation of α-tocopherol succinate [34]. The effect of molar ratio of succinic anhydride to α-tocopherol was showed in Figure 8. The obtained result suggested that the increase in molar ratio of succinic anhydride to α-tocopherol significantly improved the yield of α-tocopherol succinate from 64% to 94%. However, there was no obvious increase in the yield of α-tocopherol succinate when the molar ratio of succinic anhydride to α-tocopherol was higher than 3:1. Therefore, the optimal molar ratio of succinic anhydride to α-tocopherol was confirmed as 3:1.

Figure 8 Effect of molar ratio of substrates. Conditions of reaction: 0.15 mmol α-tocopherol, 0.15 to 0.75 mmol succinic anhydride, 0.10 mmol NS-DMAP, hexane/acetone(4 mL/1 mL), 55°C, nitrogen, 16 h.
Figure 8

Effect of molar ratio of substrates. Conditions of reaction: 0.15 mmol α-tocopherol, 0.15 to 0.75 mmol succinic anhydride, 0.10 mmol NS-DMAP, hexane/acetone(4 mL/1 mL), 55°C, nitrogen, 16 h.

3.6 Effect of temperature on yield of α-tocopherol succinate

Temperature was another crucial factor affecting the activity of the whole reaction system [35]. As shown in Figure 9, it can be clearly observed that the yield of α-tocopherol succinate increased with increasing the

Figure 9 Effect of different temperature. Conditions of reaction: 0.15 mmol α-tocopherol, 0.45 mmol succinic anhydride, hexane/ acetone (4 mL/1 mL), 0.10 mmol NS-DMAP, nitrogen, 16 h.
Figure 9

Effect of different temperature. Conditions of reaction: 0.15 mmol α-tocopherol, 0.45 mmol succinic anhydride, hexane/ acetone (4 mL/1 mL), 0.10 mmol NS-DMAP, nitrogen, 16 h.

temperature from 35 to 55°C. The result suggested that an increase in reaction temperature had a significant effect on the catalytic reaction. However, further increase in the temperature, the yield of α-tocopherol succinate showed no considerable increase. Besides, the structure of α-tocopherol and the color of product were easily affected in a high temperature. The result indicated that the optimal temperature was 55°C.

3.7 Stability of catalyst

The longevity and reusability of heterogeneous catalysts were crucial factors from economy and environmental points of view. Therefore, the recyclability of nano-SiO2 immobilized DMAP derivative was investigated under optimal conditions for the synthesis of α-tocopherol succinate. And the reaction was conducted by the decrease in amount of reaction substrates with catalyst amount loss. As showed in Figure 10, the catalyst showed no significant loss of catalytic activity even after reusing for 20 times. Furthermore, comparing the FT-IR spectrum of the reused catalyst with the fresh catalyst, Figure 11 showed that they had no significant changes. It clearly demonstrated that nano-SiO2 immobilized DMAP derivative showed the excellent stability during the catalytic cycles.

Figure 10 Catalytic recycle times. Conditions of reaction: 0.15 mmol α-tocopherol, 0.45 mmol succinic anhydride, hexane/ acetone (4 mL/1 mL), 0.10 mmol NS-DMAP, nitrogen, 16 h.
Figure 10

Catalytic recycle times. Conditions of reaction: 0.15 mmol α-tocopherol, 0.45 mmol succinic anhydride, hexane/ acetone (4 mL/1 mL), 0.10 mmol NS-DMAP, nitrogen, 16 h.

Figure 11 Comparison of FT-IR for fresh catalyst with reused catalyst.
Figure 11

Comparison of FT-IR for fresh catalyst with reused catalyst.

4 Conclusion

Vitamin E succinate was successfully synthesized with a satisfactory yield in an effective reaction system. Nano-SiO2 immobilized 4-dimethylaminopyridine derivative (NS-DMAP) was employed to synthesize α-tocopherol succinate, which avoided the catalyst contamination of the product and permitted the easy recycling of DMAP. Besides, a hexane-acetone mixed solvent was aimed to improve the activity of immobilized DMAP derivative and the substrate solubility. The maximum yield of α-tocopherol succinate reached 94% under the optimal conditions. To the best of our knowledge, it is the first example that vitamin E succinate was synthesized in a hexane-acetone mixed solvent system using nano-SiO2 immobilized DMAP derivative. And it will be a potential application for the industrial production of vitamin E succinate.

† Dan Chen and Binglin Li contributed equally to this work

Acknowledgements

This work was supported by Key Research and Invention Program in Shaanxi Province of China (Program No. 2018NY-131), Northwest University Doctorate Dissertation of Excellence Funds (Program No. YYB17014) and Northwest University Graduate Innovation and Creativity Funds (Program No. YZZ17130).

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Received: 2018-11-20
Accepted: 2019-05-05
Published Online: 2019-07-13
Published in Print: 2019-01-28

© 2019 Chen et al., published by De Gruyter

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

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  7. Green synthesis of iron oxide nanoparticles using Platanus orientalis leaf extract for antifungal activity
  8. Ultrasound assisted chemical activation of peanut husk for copper removal
  9. Room temperature silanization of Fe3O4 for the preparation of phenyl functionalized magnetic adsorbent for dispersive solid phase extraction for the extraction of phthalates in water
  10. Evaluation of the saponin green extraction from Ziziphus spina-christi leaves using hydrothermal, microwave and Bain-Marie water bath heating methods
  11. Oxidation of dibenzothiophene using the heterogeneous catalyst of tungsten-based carbon nanotubes
  12. Calcined sodium silicate as an efficient and benign heterogeneous catalyst for the transesterification of natural lecithin to L-α-glycerophosphocholine
  13. Synergistic effect between CO2 and H2O2 on ethylbenzene oxidation catalyzed by carbon supported heteropolyanion catalysts
  14. Hydrocyanation of 2-arylmethyleneindan-1,3-diones using potassium hexacyanoferrate(II) as a nontoxic cyanating agent
  15. Green synthesis of hydratropic aldehyde from α-methylstyrene catalyzed by Al2O3-supported metal phthalocyanines
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  18. Production of value-added chemicals from esterification of waste glycerol over MCM-41 supported catalysts
  19. Green synthesis of zerovalent copper nanoparticles for efficient reduction of toxic azo dyes congo red and methyl orange
  20. Optimization of the biological synthesis of silver nanoparticles using Penicillium oxalicum GRS-1 and their antimicrobial effects against common food-borne pathogens
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  24. Green cyclic acetals production by glycerol etherification reaction with benzaldehyde using cationic acidic resin
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  30. Green synthesis and structural characterization of novel N1-substituted 3,4-dihydropyrimidin-2(1H)-ones
  31. Biodiesel production from cotton oil using heterogeneous CaO catalysts from eggshells prepared at different calcination temperatures
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  33. Green synthesis of the innovative super paramagnetic nanoparticles from the leaves extract of Fraxinus chinensis Roxb and their application for the decolourisation of toxic dyes
  34. Biogenic ZnO nanoparticles: a study of blueshift of optical band gap and photocatalytic degradation of reactive yellow 186 dye under direct sunlight
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  36. Enhancement of molecular weight reduction of natural rubber in triphasic CO2/toluene/H2O systems with hydrogen peroxide for preparation of biobased polyurethanes
  37. An efficient green synthesis of novel 1H-imidazo[1,2-a]imidazole-3-amine and imidazo[2,1-c][1,2,4]triazole-5-amine derivatives via Strecker reaction under controlled microwave heating
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  54. Assessment of aqueous extract of Gypsophila aretioides for inhibitory effects on calcium carbonate formation
  55. An environmentally friendly acylation reaction of 2-methylnaphthalene in solvent-free condition in a micro-channel reactor
  56. Aegle marmelos phytochemical stabilized synthesis and characterization of ZnO nanoparticles and their role against agriculture and food pathogen
  57. A reactive coupling process for co-production of solketal and biodiesel
  58. Optimization of the asymmetric synthesis of (S)-1-phenylethanol using Ispir bean as whole-cell biocatalyst
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  61. Extraction of glycyrrhizic acid by aqueous two-phase system formed by PEG and two environmentally friendly organic acid salts - sodium citrate and sodium tartrate
  62. Green synthesis of copper oxide nanoparticles using Juglans regia leaf extract and assessment of their physico-chemical and biological properties
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  69. Selenium supplementation during fermentation with sugar beet molasses and Saccharomyces cerevisiae to increase bioethanol production
  70. Biosynthetic potential assessment of four food pathogenic bacteria in hydrothermally silver nanoparticles fabrication
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  72. Pyrolysis of palm oil using zeolite catalyst and characterization of the boil-oil
  73. Azadirachta indica leaves extract assisted green synthesis of Ag-TiO2 for degradation of Methylene blue and Rhodamine B dyes in aqueous medium
  74. Synthesis of vitamin E succinate catalyzed by nano-SiO2 immobilized DMAP derivative in mixed solvent system
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  76. Production of uronic acids by hydrothermolysis of pectin as a model substance for plant biomass waste
  77. Biofabrication of highly pure copper oxide nanoparticles using wheat seed extract and their catalytic activity: A mechanistic approach
  78. Intelligent modeling and optimization of emulsion aggregation method for producing green printing ink
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  81. Optimization of acid catalyzed esterification and mixed metal oxide catalyzed transesterification for biodiesel production from Moringa oleifera oil
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  83. Aiming for a standardized protocol for preparing a process green synthesis report and for ranking multiple synthesis plans to a common target product
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  88. Biodiesel production from waste cooking oil
  89. The effect of activation temperature on structure and properties of blue coke-based activated carbon by CO2 activation
  90. Optimization of reaction parameters for the green synthesis of zero valent iron nanoparticles using pine tree needles
  91. Microwave-assisted protocol for squalene isolation and conversion from oil-deodoriser distillates
  92. Denitrification performance of rare earth tailings-based catalysts
  93. Facile synthesis of silver nanoparticles using Averrhoa bilimbi L and Plum extracts and investigation on the synergistic bioactivity using in vitro models
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https://doi.org/10.1515/gps-2019-0037
Keywords for this article
vitamin E succinate; nano-SiO2; 4-dimethylaminopyridine (DMAP); immobilization; mixed solvent system
Creative Commons
BY 4.0

Articles in the same Issue

  1. Regular Articles
  2. Studies on the preparation and properties of biodegradable polyester from soybean oil
  3. Flow-mode biodiesel production from palm oil using a pressurized microwave reactor
  4. Reduction of free fatty acids in waste oil for biodiesel production by glycerolysis: investigation and optimization of process parameters
  5. Saccharin: a cheap and mild acidic agent for the synthesis of azo dyes via telescoped dediazotization
  6. Optimization of lipase-catalyzed synthesis of polyethylene glycol stearate in a solvent-free system
  7. Green synthesis of iron oxide nanoparticles using Platanus orientalis leaf extract for antifungal activity
  8. Ultrasound assisted chemical activation of peanut husk for copper removal
  9. Room temperature silanization of Fe3O4 for the preparation of phenyl functionalized magnetic adsorbent for dispersive solid phase extraction for the extraction of phthalates in water
  10. Evaluation of the saponin green extraction from Ziziphus spina-christi leaves using hydrothermal, microwave and Bain-Marie water bath heating methods
  11. Oxidation of dibenzothiophene using the heterogeneous catalyst of tungsten-based carbon nanotubes
  12. Calcined sodium silicate as an efficient and benign heterogeneous catalyst for the transesterification of natural lecithin to L-α-glycerophosphocholine
  13. Synergistic effect between CO2 and H2O2 on ethylbenzene oxidation catalyzed by carbon supported heteropolyanion catalysts
  14. Hydrocyanation of 2-arylmethyleneindan-1,3-diones using potassium hexacyanoferrate(II) as a nontoxic cyanating agent
  15. Green synthesis of hydratropic aldehyde from α-methylstyrene catalyzed by Al2O3-supported metal phthalocyanines
  16. Environmentally benign chemical recycling of polycarbonate wastes: comparison of micro- and nano-TiO2 solid support efficiencies
  17. Medicago polymorpha-mediated antibacterial silver nanoparticles in the reduction of methyl orange
  18. Production of value-added chemicals from esterification of waste glycerol over MCM-41 supported catalysts
  19. Green synthesis of zerovalent copper nanoparticles for efficient reduction of toxic azo dyes congo red and methyl orange
  20. Optimization of the biological synthesis of silver nanoparticles using Penicillium oxalicum GRS-1 and their antimicrobial effects against common food-borne pathogens
  21. Optimization of submerged fermentation conditions to overproduce bioethanol using two industrial and traditional Saccharomyces cerevisiae strains
  22. Extraction of In3+ and Fe3+ from sulfate solutions by using a 3D-printed “Y”-shaped microreactor
  23. Foliar-mediated Ag:ZnO nanophotocatalysts: green synthesis, characterization, pollutants degradation, and in vitro biocidal activity
  24. Green cyclic acetals production by glycerol etherification reaction with benzaldehyde using cationic acidic resin
  25. Biosynthesis, characterization and antimicrobial activities assessment of fabricated selenium nanoparticles using Pelargonium zonale leaf extract
  26. Synthesis of high surface area magnesia by using walnut shell as a template
  27. Controllable biosynthesis of silver nanoparticles using actinobacterial strains
  28. Green vegetation: a promising source of color dyes
  29. Mechano-chemical synthesis of ammonia and acetic acid from inorganic materials in water
  30. Green synthesis and structural characterization of novel N1-substituted 3,4-dihydropyrimidin-2(1H)-ones
  31. Biodiesel production from cotton oil using heterogeneous CaO catalysts from eggshells prepared at different calcination temperatures
  32. Regeneration of spent mercury catalyst for the treatment of dye wastewater by the microwave and ultrasonic spray-assisted method
  33. Green synthesis of the innovative super paramagnetic nanoparticles from the leaves extract of Fraxinus chinensis Roxb and their application for the decolourisation of toxic dyes
  34. Biogenic ZnO nanoparticles: a study of blueshift of optical band gap and photocatalytic degradation of reactive yellow 186 dye under direct sunlight
  35. Leached compounds from the extracts of pomegranate peel, green coconut shell, and karuvelam wood for the removal of hexavalent chromium
  36. Enhancement of molecular weight reduction of natural rubber in triphasic CO2/toluene/H2O systems with hydrogen peroxide for preparation of biobased polyurethanes
  37. An efficient green synthesis of novel 1H-imidazo[1,2-a]imidazole-3-amine and imidazo[2,1-c][1,2,4]triazole-5-amine derivatives via Strecker reaction under controlled microwave heating
  38. Evaluation of three different green fabrication methods for the synthesis of crystalline ZnO nanoparticles using Pelargonium zonale leaf extract
  39. A highly efficient and multifunctional biomass supporting Ag, Ni, and Cu nanoparticles through wetness impregnation for environmental remediation
  40. Simple one-pot green method for large-scale production of mesalamine, an anti-inflammatory agent
  41. Relationships between step and cumulative PMI and E-factors: implications on estimating material efficiency with respect to charting synthesis optimization strategies
  42. A comparative sorption study of Cr3+ and Cr6+ using mango peels: kinetic, equilibrium and thermodynamic
  43. Effects of acid hydrolysis waste liquid recycle on preparation of microcrystalline cellulose
  44. Use of deep eutectic solvents as catalyst: A mini-review
  45. Microwave-assisted synthesis of pyrrolidinone derivatives using 1,1’-butylenebis(3-sulfo-3H-imidazol-1-ium) chloride in ethylene glycol
  46. Green and eco-friendly synthesis of Co3O4 and Ag-Co3O4: Characterization and photo-catalytic activity
  47. Adsorption optimized of the coal-based material and application for cyanide wastewater treatment
  48. Aloe vera leaf extract mediated green synthesis of selenium nanoparticles and assessment of their In vitro antimicrobial activity against spoilage fungi and pathogenic bacteria strains
  49. Waste phenolic resin derived activated carbon by microwave-assisted KOH activation and application to dye wastewater treatment
  50. Direct ethanol production from cellulose by consortium of Trichoderma reesei and Candida molischiana
  51. Agricultural waste biomass-assisted nanostructures: Synthesis and application
  52. Biodiesel production from rubber seed oil using calcium oxide derived from eggshell as catalyst – optimization and modeling studies
  53. Study of fabrication of fully aqueous solution processed SnS quantum dot-sensitized solar cell
  54. Assessment of aqueous extract of Gypsophila aretioides for inhibitory effects on calcium carbonate formation
  55. An environmentally friendly acylation reaction of 2-methylnaphthalene in solvent-free condition in a micro-channel reactor
  56. Aegle marmelos phytochemical stabilized synthesis and characterization of ZnO nanoparticles and their role against agriculture and food pathogen
  57. A reactive coupling process for co-production of solketal and biodiesel
  58. Optimization of the asymmetric synthesis of (S)-1-phenylethanol using Ispir bean as whole-cell biocatalyst
  59. Synthesis of pyrazolopyridine and pyrazoloquinoline derivatives by one-pot, three-component reactions of arylglyoxals, 3-methyl-1-aryl-1H-pyrazol-5-amines and cyclic 1,3-dicarbonyl compounds in the presence of tetrapropylammonium bromide
  60. Preconcentration of morphine in urine sample using a green and solvent-free microextraction method
  61. Extraction of glycyrrhizic acid by aqueous two-phase system formed by PEG and two environmentally friendly organic acid salts - sodium citrate and sodium tartrate
  62. Green synthesis of copper oxide nanoparticles using Juglans regia leaf extract and assessment of their physico-chemical and biological properties
  63. Deep eutectic solvents (DESs) as powerful and recyclable catalysts and solvents for the synthesis of 3,4-dihydropyrimidin-2(1H)-ones/thiones
  64. Biosynthesis, characterization and anti-microbial activity of silver nanoparticle based gel hand wash
  65. Efficient and selective microwave-assisted O-methylation of phenolic compounds using tetramethylammonium hydroxide (TMAH)
  66. Anticoagulant, thrombolytic and antibacterial activities of Euphorbia acruensis latex-mediated bioengineered silver nanoparticles
  67. Volcanic ash as reusable catalyst in the green synthesis of 3H-1,5-benzodiazepines
  68. Green synthesis, anionic polymerization of 1,4-bis(methacryloyl)piperazine using Algerian clay as catalyst
  69. Selenium supplementation during fermentation with sugar beet molasses and Saccharomyces cerevisiae to increase bioethanol production
  70. Biosynthetic potential assessment of four food pathogenic bacteria in hydrothermally silver nanoparticles fabrication
  71. Investigating the effectiveness of classical and eco-friendly approaches for synthesis of dialdehydes from organic dihalides
  72. Pyrolysis of palm oil using zeolite catalyst and characterization of the boil-oil
  73. Azadirachta indica leaves extract assisted green synthesis of Ag-TiO2 for degradation of Methylene blue and Rhodamine B dyes in aqueous medium
  74. Synthesis of vitamin E succinate catalyzed by nano-SiO2 immobilized DMAP derivative in mixed solvent system
  75. Extraction of phytosterols from melon (Cucumis melo) seeds by supercritical CO2 as a clean technology
  76. Production of uronic acids by hydrothermolysis of pectin as a model substance for plant biomass waste
  77. Biofabrication of highly pure copper oxide nanoparticles using wheat seed extract and their catalytic activity: A mechanistic approach
  78. Intelligent modeling and optimization of emulsion aggregation method for producing green printing ink
  79. Improved removal of methylene blue on modified hierarchical zeolite Y: Achieved by a “destructive-constructive” method
  80. Two different facile and efficient approaches for the synthesis of various N-arylacetamides via N-acetylation of arylamines and straightforward one-pot reductive acetylation of nitroarenes promoted by recyclable CuFe2O4 nanoparticles in water
  81. Optimization of acid catalyzed esterification and mixed metal oxide catalyzed transesterification for biodiesel production from Moringa oleifera oil
  82. Kinetics and the fluidity of the stearic acid esters with different carbon backbones
  83. Aiming for a standardized protocol for preparing a process green synthesis report and for ranking multiple synthesis plans to a common target product
  84. Microstructure and luminescence of VO2 (B) nanoparticle synthesis by hydrothermal method
  85. Optimization of uranium removal from uranium plant wastewater by response surface methodology (RSM)
  86. Microwave drying of nickel-containing residue: dielectric properties, kinetics, and energy aspects
  87. Simple and convenient two step synthesis of 5-bromo-2,3-dimethoxy-6-methyl-1,4-benzoquinone
  88. Biodiesel production from waste cooking oil
  89. The effect of activation temperature on structure and properties of blue coke-based activated carbon by CO2 activation
  90. Optimization of reaction parameters for the green synthesis of zero valent iron nanoparticles using pine tree needles
  91. Microwave-assisted protocol for squalene isolation and conversion from oil-deodoriser distillates
  92. Denitrification performance of rare earth tailings-based catalysts
  93. Facile synthesis of silver nanoparticles using Averrhoa bilimbi L and Plum extracts and investigation on the synergistic bioactivity using in vitro models
  94. Green production of AgNPs and their phytostimulatory impact
  95. Photocatalytic activity of Ag/Ni bi-metallic nanoparticles on textile dye removal
  96. Topical Issue: Green Process Engineering / Guest Editors: Martine Poux, Patrick Cognet
  97. Modelling and optimisation of oxidative desulphurisation of tyre-derived oil via central composite design approach
  98. CO2 sequestration by carbonation of olivine: a new process for optimal separation of the solids produced
  99. Organic carbonates synthesis improved by pervaporation for CO2 utilisation
  100. Production of starch nanoparticles through solvent-antisolvent precipitation in a spinning disc reactor
  101. A kinetic study of Zn halide/TBAB-catalysed fixation of CO2 with styrene oxide in propylene carbonate
  102. Topical on Green Process Engineering
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