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Dead zone for hydrogenation of propylene reaction carried out on commercial catalyst pellets

  • M. Szukiewicz EMAIL logo , E. Chmiel-Szukiewicz , K. Kaczmarski and A. Szałek
Published/Copyright: June 3, 2019
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Open Chemistry
From the journal Open Chemistry Volume 17 Issue 1

Abstract

Heterogeneous catalytic processes have for years been of crucial importance in the chemical industry, while biocatalitic processes have become more and more important. For both types of the processes the existence of zones without reactants were reported. Despite the fact that the dead zone can appear in real processes relatively often, the most important problem in practice is the real size of a dead zone inside a catalyst pellet or the real depth of penetration reagents in a biofilm and this is still unsolved. The knowledge of the parameters and some information about the process can allow improvement in yield, and selectivity, reduce consumption of catalyst by reducing the bed size etc. Presented in this work is a simple method of predicting the size of the inactive core of a uniformly activated catalyst pellet. The method is based on a simple mathematical model of catalyst pellet with inactive pellet centre and experimental investigations.

Keywords: dead zone; dead core; diffusional resistances

1 Introduction

Heterogeneous catalytic processes have for years been of crucial importance in the chemical industry, while biocatalitic processes have become more and more important. For both types of processes the existence of zones without reactants were reported. It should be noted that we don’t think about the physical defects of catalysts resulting mainly from imperfections of manufacturing or activation processes such as phase inhomogeneity, improper pellet making, passivation of active sites, shapes or sizes distributions, improper porosity etc. We are interested in regions of catalysts or biofilms without reactants that arise spontaneously as a result of a fast reaction run, despite the fact that in this area the catalyst is active. Lack of substrata in the zone lessens reactor or bioreactor productivity and influences the process economy. The phenomenon describing this is especially important now, when a lot of institutes work on producing more active and more selective catalysts (e.g. obtained by promotion). On the large scale, formation of zones without reactants can reduce or even destroy effects obtained in the laboratory. Furthermore, the reaction process can be so fast that the reaction only really takes place in the narrow, surface part of the catalyst pellet. In such a case it makes no sense to produce catalysts with active materials placed in non-productive core part of the pellet. For this reason it is especially important to develop methods and tools of the phenomenon analysis.

For heterogeneous catalysis the zone without reactants is called the “dead zone” and it was predicted by Aris [1] and Temkin [2].While for bio-processes a few terms concerning this phenomena are found e.g. “biological dead zone”, “enzymatic inactive region” all mentioned terms are used to describe region where diffusional resistances are sufficiently large and in catalyst appears the zone where reaction rate is equal to zero. The essence of the dead zone concept is presented in Figure 1.

Figure 1 Concentration profiles in catalyst.
Figure 1

Concentration profiles in catalyst.

If internal diffusional resistances are small (small Thiele modulus value) concentration of the reagent drops down towards pellet center but it is always larger than zero (solid line in Figure 1). The larger the internal diffusional resistances the smaller the value of substrata concentration in the pellet center and, finally, for critical Thiele modulus value, reagent concentration drops down to zero (dashed line in Figure 1). For larger resistances in the pellet center the zone without reactant the dead zone is formed (dotted line in Figure 1).

It should be noted that solution for the mathematical model of dead zone problem is a harder task than the regular model (model without dead zone, commonly applied and discussed in literature). From a mathematical point of view the regular model is typical boundary value problem while the dead zone model belongs to the free boundary value problems. More details concerning dead zone model will be presented in Methods section.

Previous investigations focused on the theoretical aspects of the dead zone model, for instance mathematical consideration on the existence of free boundary problems for chemical reactions, Diaz and Hernandez [3] or existence and formation of dead core, Bandle and Stackgold [4]. Next Bobisud [5] applied singular perturbation analysis for dead core behavior and Bobisud and Royalty [6] studied formation of dead zone for some diffusion-reaction equations (the generation term could be simplified to Langmuir-Hinshelwood or Michelis-Menten kinetics). In the 1980s some works were published concerning more practical aspects, e.g. Fedotov et al. [7] investigated the conditions which have to be satisfied for dead zone formation for selected kinetic equations (so-called necessary conditions of dead zone formation) and Garcia Ochoa and Romero [8] presented both necessary and sufficient conditions of dead zone formation for the simplest kinetic equation (power law equation for one-component isothermal reaction). Similar points was raised by Andreev [9] in more recent work. Of course, the dead zone can also be detected in real processes. For instance for methanol steam reforming over Cu/ZnO/Al2O3 catalyst (reported by Lee et al. [10]), for hydrogenation of benzene over nickel-alumina catalyst [11], or for acetic acid oxidation [12,13].

For biotechnology the dead zone was reported for limitation created by oxygen diffusion into gel beads for cephalosporin C production processes [14,15], for the process of Penicillin G enzymatic hydrolysis to 6-Aminopenicillanic acid [16] or the process of 3-chloro-1,2-propanediol degradation by Ca-alginate immobilized Pseudomonas putida cells [17]. Regions with negligible mass transfer flux in an anaerobic fixed-bed reactor were founded by Zaiat et al. [18] and Pereira and Oliveira [19] analyzed the occurrence of dead core in catalytic particles containing immobilized enzymes for the Michaelis-Menten kinetics.

Despite the dead zone can appearing in real processes relatively often, the most important problem in practice is the real size of a dead zone inside a catalyst pellet or the real depth of penetration reagents in a biofilm and this has not been reported. To our best knowledge, the general method of prediction of these parameters have not been published. The knowledge of the parameters and some information about the process can allow improved yield, selectivity and reduce the consumption of catalyst and reduce the bed size etc.

Advances in computing hardware and algorithms have dramatically improved the ability to simulate complex processes. Presented in the work is a simple evaluation method for estimating size of inactive core of uniformly activated catalyst pellet. The method is based on a mathematical model of catalyst pellet with inactive core and experimental investigations.

2 Methods

The aim of this work is the development of an evaluation method for dead zone size estimate. To do this the following two conditions should be met:

  1. A reference reaction that promises formation of dead zone inside the catalyst pellet as well as catalyst itself should be chosen. As a reference reaction for investigation of the dead zone problem we choose propylene hydrogenation reaction. The reaction is easy to carry out and proceeds under mild conditions. As the catalyzer the commercial catalyst produced by New Chemical Syntheses Institute, Catalyst Department, Puławy, Poland was chosen. The physico-chemical properties of substrates and properties of catalyst indicate that the reaction should run very fast and diffusional limitations should be sufficiently large to produce dead zone.

  2. Next, a model of sufficient precision for description of the process should be chosen. If reaction zone is narrow, heat generation in the pellet is not very intensive and temperature inside a pellet and in fluid bulk should be almost the same. So, the process can be regarded as isothermal. On other hand the mass transfer resistances from bulk phase into catalyst cannot be neglected. In the following it was assumed that the process can be described by the simple isothermal mass transfer model coupled with chemical reaction, taking into account mass transfer resistance.

3 Experiment

The propene hydrogenation reaction was carried out in tubular reactor (Microactivity-Efficient Unit, manufacturer: Process Integral Development Eng&tech, Madrid, Spain) on heterogeneous nickel catalyst (type of KUB-3, manufacturer: New Chemical Syntheses Institute, Catalyst Department, Puławy, Poland). Nickel catalyst was activated in accordance with the manufacturer’s instructions. Post reaction mixtures were analysed with gas chromatograph (CALIDUS™ 101 Gas Chromatograph, manufacturer: Falcon Analytical, Lewisburg, WV, USA).

The system was flushed for 30 minutes with a constant flow of hydrogen until a stable right temperature and pressure were obtained. Next, flow of propylene was started. Reaction was carried out for circa 1hr until the stable temperature inside the tubular reactor was reached. The relatively long time was taken to ensure that the steady-state conditions were reached. Next the reaction mixture was analyzed.

Investigations were made in two steps

  1. preliminary step, reaction had run on well-crushed catalyst pellet (crushed pellet size was about 40 micrometers)

  2. main investigations, reaction had run on spherical catalyst pellet (pellet diameter was about 4.6 mm)

Operating conditions are presented in Table 1. As usually the conditions Step 1 encompass the conditions where model is verified.

Table 1

Reactor operating conditions.

Step 1Step 2
Pressure, Pa1.2×1051.2×105
hydrogen flow rate, cm3 min-13030
temperature of the catalyst bed, °C45-8550-80
propylene flow rate, cm3 min-13.33 to 7.54.0 to 6.6

4 Mathematical model

Mass balance:

(1)DeRT(d2ppdr2+2rdppdr)−rp=0

BC:

(2)dppdr|r=Rdz     =0 and pp|r=Rdz=0
(3)−dppdr|r=Rz =kgDe(pp,b−pp,s)

If kgDe→∞eq.(5) becomes

(3a)pp|r=Rz =pp,s

where Rdz is a radius of inactive core of catalyst pellet.

A comment is required for equation (2). Generally in the literature it is assumed that the derivative of unknown function in the centre of the pellet is equal to zero. It is a simplification which can follow to unphysical solution when concentration in the particle drops to zero at position 0<r<Rz. In the general case the correct condition is that which requires the specification in which point the derivative becomes zero (this position is unknown and has to be established in the calculations). It should be noted that conditions (2) cannot be treated as two independent conditions. So the general rule that for second order derivative two boundary conditions should be implemented is fulfilled in this case by Eq.(2) and Eq.(3) or Eq.(3a). This is similar to condition (3) in which there are two unknown parameters namely derivative and the concentration on the pellet surface and they should be calculated simultaneously.

In the following boundary conditions (2) and (3) were applied.

The foundations of engineering mathematics of the diffusion and reaction processes were presented by Aris [1]. The model presented corresponds to the Aris’ model for description of dead zone problem. Moreover, the kinetic equation rp should meet necessary conditions of dead zone formation presented e.g. by Andreev [9]. Presented below Eq.(5) met them.

The model presented is an example of a free boundary problem. In chemical engineering, the most recognizable problem of this type is the Stefan problem in which a phase boundary can move with time. Solution of the free boundary value problem needs special numerical algorithms. In the present work the method presented by Szukiewicz [20] is used.

Ethical approval: The conducted research is not related to either human or animal use.

5 Results

Kinetic equation of the process was determined on the basis of results obtained in the first step (diffusion limitation was eliminated due to very small size of crushed catalyst). We choose power-law type of kinetic equation:

(4)rp=k∞ppne−ERT    [mol/(m3s)]

Frequency factor, reaction order and activation energy were estimated using Excel, applying multiple linear regression (Equation (4) was previously linearized). The kinetic parameters have high correlation (R2=0.963), the standard error of the regression is equal to 0.063. Values of parameters are presented in Table 2.

Table 2

Kinetic parameters.

k∞, mol m-3 Pa-n s-144467±2222
n, -0.51±0.036
E, J mol-1-26513±986

For further consideration the following equation was accepted

(5)rp=44400pp0.5e−26500RT    [mol/(m3s)]

6 Discussion

Before the main investigation were started we had confirmed a assumption about quasi isothermal process conditions. Namely, for inlet propylene concentrations less than 18% vol. and reactor oven temperature less than 85°C the gas temperature increase between reactor inlet and outlet was less than one degree, what justify assumption of quasi isothermal process conditions.

The obtained kinetic equation (5) met necessary condition for appearance of dead zone [9] namely the value of power is inside the range (-1,1). It suggests that appearing of dead zone is very likely for operating conditions presented in Table 1.

To realize the aim of the work, at first it must be concerned with how closely the model reflects the system definition - the domain of applicability for this model should be specified. If the model approximates real processes with sufficient precision then its solution

determines both the location of dead zone and model applicability region. Then, if calculated and experimental values of effectiveness factor defined by

(6)η=actual overall rate of reactionrate of reaction that would result if entire interior surface were exposed to the external pellet surface conditions

are the same (an error is within the specified tolerance), the dead zone with the radius equal to Rdz is present inside the pellet.

The results of validation of the model eq.(1)-(3), are presented in Figure 2. Necessary external mass transfer coefficients, were calculated from well-known, recommended in Perry’s handbook [21] equation

Figure 2 Mathematical model validation. In the region between dashed lines the model fulfills the required accuracy.
Figure 2

Mathematical model validation. In the region between dashed lines the model fulfills the required accuracy.

(7)Sh=0.33 Re0.6Sc0.33

It is easy to observe, that inside the operation condition range the proposed model describes the real process very well. Calculated from the model effectiveness factor values varies from experimental ones no more than 10% for 61 of 71 measurements. Selected results of the experiments and computations are presented in details in Table 3. Actual overall reaction rates presented in Table 3 results from experiment. The reference reaction rate that would result if entire interior surface were exposed to the bulk conditions was calculated from Eq.(5) using data presented in Table 1 and Table 3.

Table 3

Model validation and relative volume of dead zone.

NoTyprp,av,expDekghcalchexprelative radius of dead zonerelative volume of dead zone
K—mol s-1m-3m2s-1m s-1——%%
1322.30.1818.207.30×10-82.62×10-20.06100.058993.782.4
2321.40.1617.327.30×10-82.39×10-20.06000.061493.882.6
3322.60.1617.347.30×10-82.38×10-20.05880.059394.083.0
4328.30.1821.298.16×10-82.63×10-20.05820.057994.083.1
5328.50.1620.298.16×10-82.39×10-20.05620.058594.283.7
6328.40.1618.848.16×10-82.40×10-20.05630.054594.283.7
7332.20.1822.651.01×10-72.66×10-20.06060.055393.882.5
8332.70.1622.171.01×10-72.42×10-20.05820.057094.083.1
9332.40.1420.821.01×10-72.19×10-20.05640.058294.283.7
10338.10.1626.021.27×10-72.44×10-20.05960.058193.982.7
11338.20.1625.741.27×10-72.44×10-20.05950.057393.982.8
123380.1424.271.27×10-72.20×10-20.05750.058694.183.3
13342.80.1630.001.63×10-72.46×10-20.06240.059793.682.0
143430.1630.411.63×10-72.46×10-20.06220.060293.682.0
15343.10.1428.631.63×10-72.22×10-20.05980.061193.982.7
163480.1633.751.99×10-72.48×10-20.06340.059293.581.7
17348.10.1431.801.99×10-72.24×10-20.06080.060393.882.4
18347.90.1229.451.99×10-72.01×10-20.05830.061694.083.1
19352.70.1234.112.54×10-72.02×10-20.06070.064593.882.4
20352.90.1435.982.54×10-72.26×10-20.06350.061593.581.7
21353.10.1638.252.54×10-72.50×10-20.06590.059993.281.0

The very good precision of the model presented in entire range of tested reactor operation conditions follows that the model is applicable in the specified range and predicted sizes of dead zone are trustworthy. The estimated Rdz –values are approximately equal to 2.15 mm. It show that most of catalyst pellet is inactive – reaction runs in the surface shell of the pellet only and circa 80-83% of the pellet volume remains inactive. This is despite the fact that the catalyst pellet was fully active – active places are uniformly distributed in manufacturing process. The only reason for the described situation remain diffusional resistance inside the pellet. Advice for catalyst manufacturing can be proposed to place active material in the outer part of catalyst pellet. Application of so-called “core-shell” type of catalyst should improve yield of reaction and reduce the consumption of an active material.

The results obtained confirm that the choice of reaction and the mathematical model for description of experiment was correct. Inside the pellet exists dead zone. It should be noted that if the regular model (with typical boundary conditions) would be used instead of presented one, the obtained result of simulations would have no physical sense.

7 Conclusions

On the basis of investigations performed the following conclusions can be drawn:

  1. The method of estimation of dead zone location is relatively simple, it is able to detect a size of dead zone. It has no limits in their applicability. Only selection of the mathematical model to describe chemical or biochemical process can be a bit more confused in specific cases because of unclassical boundary condition.

  2. The method is universal and it is applicable in more complex cases (e.g. non-isothermal processes or for complex reaction systems). In that case successful result of estimation depends on application of correct mathematical model.

  3. The dead zone covers more than 80% of catalyst pellet for propylene hydrogenation (and in consequence 80% of reactor volume). It follows that reaction runs in surface shell of catalyst only. This situation is not optimal and reaction yield can be improved by application of non-uniformly activated catalyst, namely of “core-shell” type.

Acknowledgments

This work was supported by grant no. 2015/17/B/ST8/03369 of the National Science Centre, Poland.

  1. Conflict of interest: Authors declare no conflict of interest.

Nomenclature

De

effective diffusivity (m2 s-1)

pi

partial pressure of a compound (Pa)

P

total pressure

r

distance from the center to a given position in a catalyst pellet (m)

Rg

gas constant (J⋅mol-1⋅K-1)

rp

reaction rate in reference to propylene (mol⋅m-3⋅s-1)

Rdz

dead zone radius (m)

Rz

pellet radius (m)

T

bulk temperature of gas mixture (K)

x

dimensionless distance from the center to a given position in catalyst pellet, x=r/R

yi

molar fraction of a compound

Greek symbols

η

effectiveness factor

Φ

Thiele modulus

Subscripts

p

propylene

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Received: 2018-09-02
Accepted: 2019-01-25
Published Online: 2019-06-03

© 2019 M. Szukiewicz et al., published by De Gruyter

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

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  73. Occurrence of Aflatoxin M1 in Milk-based Mithae samples from Pakistan
  74. Kinetics of Iron Removal From Ti-Extraction Blast Furnace Slag by Chlorination Calcination
  75. Increasing the activity of DNAzyme based on the telomeric sequence: 2’-OMe-RNA and LNA modifications
  76. Exploring the optoelectronic properties of a chromene-appended pyrimidone derivative for photovoltaic applications
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  79. Greener synthesis of dimethyl carbonate from carbon dioxide and methanol using a tunable ionic liquid catalyst
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  81. Enhanced adsorption of sulfonamide antibiotics in water by modified biochar derived from bagasse
  82. Study on the Mechanism of Shugan Xiaozhi Fang on Cells with Non-alcoholic Fatty Liver Disease
  83. Comparative Effects of Salt and Alkali Stress on Antioxidant System in Cotton (Gossypium Hirsutum L.) Leaves
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  87. Phytochemistry and toxicological assessment of Bryonia dioica roots used in north-African alternative medicine
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  89. Mechanical Properties of Carbon Fiber Reinforced Nanocrystalline Nickel Composite Electroforming Deposit
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  93. The Sanskruti index of trees and unicyclic graphs
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  100. Generators of Maximal Subgroups of Harada-Norton and some Linear Groups
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  102. Influence of Production Parameters on the Content of Polyphenolic Compounds in Extruded Porridge Enriched with Chokeberry Fruit (Aronia melanocarpa (Michx.) Elliott)
  103. Effects of Supercritical Carbon Dioxide Extraction (SC-CO2) on the content of tiliroside in the extracts from Tilia L. flowers
  104. Impact of xanthan gum addition on phenolic acids composition and selected properties of new gluten-free maize-field bean pasta
  105. Impact of storage temperature and time on Moldavian dragonhead oil – spectroscopic and chemometric analysis
  106. The effect of selected substances on the stability of standard solutions in voltammetric analysis of ascorbic acid in fruit juices
  107. Determination of the content of Pb, Cd, Cu, Zn in dairy products from various regions of Poland
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  109. The Photocatalytic Activity of Zns-TiO2 on a Carbon Fiber Prepared by Chemical Bath Deposition
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  112. Antimalarial Activity of Andrographis Paniculata Ness‘s N-hexane Extract and Its Major Compounds
  113. Special Issue on ABB2018 Conference
  114. Special Issue on ICCESEN 2017
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  116. Determination of Gamma Rays Efficiency Against Rhizoctonia solani in Potatoes
  117. Studies On Compatibilization Of Recycled Polyethylene/Thermoplastic Starch Blends By Using Different Compatibilizer
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  119. Synthesis of Graphene Oxide Through Ultrasonic Assisted Electrochemical Exfoliation
  120. Special Issue on ISCMP 2018
  121. Synthesis and antiproliferative evaluation of some 1,4-naphthoquinone derivatives against human cervical cancer cells
  122. The influence of the grafted aryl groups on the solvation properties of the graphyne and graphdiyne - a MD study
  123. Electrochemical modification of platinum and glassy carbon surfaces with pyridine layers and their use as complexing agents for copper (II) ions
  124. Effect of Electrospinning Process on Total Antioxidant Activity of Electrospun Nanofibers Containing Grape Seed Extract
  125. Effect Of Thermal Treatment Of Trepel At Temperature Range 800-1200˚C
  126. Topical Issue on Agriculture
  127. The effect of Cladophora glomerata exudates on the amino acid composition of Cladophora fracta and Rhizoclonium sp.
  128. Influence of the Static Magnetic Field and Algal Extract on the Germination of Soybean Seeds
  129. The use of UV-induced fluorescence for the assessment of homogeneity of granular mixtures
  130. The use of microorganisms as bio-fertilizers in the cultivation of white lupine
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  132. Production of phosphorus biofertilizer based on the renewable materials in large laboratory scale
  133. Human health risk assessment of potential toxic elements in paddy soil and rice (Oryza sativa) from Ugbawka fields, Enugu, Nigeria
  134. Recovery of phosphates(V) from wastewaters of different chemical composition
  135. Special Issue on the 4th Green Chemistry 2018
  136. Dead zone for hydrogenation of propylene reaction carried out on commercial catalyst pellets
  137. Improved thermally stable oligoetherols from 6-aminouracil, ethylene carbonate and boric acid
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  140. Special Issue on Chemistry Today for Tomorrow 2019
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  143. Chemomertic Risk Assessment of Soil Pollution
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  145. Photocatalytic activity of NiFe2O4 and Zn0.5Ni0.5Fe2O4 modified by Eu(III) and Tb(III) for decomposition of Malachite Green
  146. Photophysical and antibacterial activity of light-activated quaternary eosin Y
  147. Spectral properties and biological activity of La(III) and Nd(III) Monensinates
  148. Special Issue on Monitoring, Risk Assessment and Sustainable Management for the Exposure to Environmental Toxins
  149. Soil organic carbon mineralization in relation to microbial dynamics in subtropical red soils dominated by differently sized aggregates
  150. A potential reusable fluorescent aptasensor based on magnetic nanoparticles for ochratoxin A analysis
  151. Special Issue on 13th JCC 2018
  152. Fluorescence study of 5-nitroisatin Schiff base immobilized on SBA-15 for sensing Fe3+
  153. Thermal and Morphology Properties of Cellulose Nanofiber from TEMPO-oxidized Lower part of Empty Fruit Bunches (LEFB)
  154. Encapsulation of Vitamin C in Sesame Liposomes: Computational and Experimental Studies
  155. A comparative study of the utilization of synthetic foaming agent and aluminum powder as pore-forming agents in lightweight geopolymer synthesis
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  157. Review of large-pore mesostructured cellular foam (MCF) silica and its applications
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  159. Synthesis And Characterization Of CoMo/Mordenite Catalyst For Hydrotreatment Of Lignin Compound Models
  160. Production of Biodiesel from Nyamplung (Calophyllum inophyllum L.) using Microwave with CaO Catalyst from Eggshell Waste: Optimization of Transesterification Process Parameters
  161. The Study of the Optical Properties of C60 Fullerene in Different Organic Solvents
  162. Composite Material Consisting of HKUST-1 and Indonesian Activated Natural Zeolite and its Application in CO2 Capture
  163. Topical Issue on Environmental Chemistry
  164. Ionic liquids modified cobalt/ZSM-5 as a highly efficient catalyst for enhancing the selectivity towards KA oil in the aerobic oxidation of cyclohexane
  165. Application of Thermal Resistant Gemini Surfactants in Highly Thixotropic Water-in-oil Drilling Fluid System
  166. Screening Study on Rheological Behavior and Phase Transition Point of Polymer-containing Fluids produced under the Oil Freezing Point Temperature
  167. The Chemical Softening Effect and Mechanism of Low Rank Coal Soaked in Alkaline Solution
  168. The Influence Of NO/O2 On The NOx Storage Properties Over A Pt-Ba-Ce/γ-Al2O3 Catalyst
  169. Special Issue on the International conference CosCI 2018
  170. Design of SiO2/TiO2 that Synergistically Increases The Hydrophobicity of Methyltrimethoxysilane Coated Glass
  171. Antidiabetes and Antioxidant agents from Clausena excavata root as medicinal plant of Myanmar
  172. Development of a Gold Immunochromatographic Assay Method Using Candida Biofilm Antigen as a Bioreceptor for Candidiasis in Rats
  173. Special Issue on Applied Biochemistry and Biotechnology 2019
  174. Adsorption of copper ions on Magnolia officinalis residues after solid-phase fermentation with Phanerochaete chrysosporium
  175. Erratum
  176. Erratum to: Sand Dune Characterization For Preparing Metallurgical Grade Silicon
https://doi.org/10.1515/chem-2019-0037
Keywords for this article
dead zone; dead core; diffusional resistances
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  124. Effect of Electrospinning Process on Total Antioxidant Activity of Electrospun Nanofibers Containing Grape Seed Extract
  125. Effect Of Thermal Treatment Of Trepel At Temperature Range 800-1200˚C
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  133. Human health risk assessment of potential toxic elements in paddy soil and rice (Oryza sativa) from Ugbawka fields, Enugu, Nigeria
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  141. Applying Discriminant and Cluster Analyses to Separate Allergenic from Non-allergenic Proteins
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  143. Chemomertic Risk Assessment of Soil Pollution
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  145. Photocatalytic activity of NiFe2O4 and Zn0.5Ni0.5Fe2O4 modified by Eu(III) and Tb(III) for decomposition of Malachite Green
  146. Photophysical and antibacterial activity of light-activated quaternary eosin Y
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  148. Special Issue on Monitoring, Risk Assessment and Sustainable Management for the Exposure to Environmental Toxins
  149. Soil organic carbon mineralization in relation to microbial dynamics in subtropical red soils dominated by differently sized aggregates
  150. A potential reusable fluorescent aptasensor based on magnetic nanoparticles for ochratoxin A analysis
  151. Special Issue on 13th JCC 2018
  152. Fluorescence study of 5-nitroisatin Schiff base immobilized on SBA-15 for sensing Fe3+
  153. Thermal and Morphology Properties of Cellulose Nanofiber from TEMPO-oxidized Lower part of Empty Fruit Bunches (LEFB)
  154. Encapsulation of Vitamin C in Sesame Liposomes: Computational and Experimental Studies
  155. A comparative study of the utilization of synthetic foaming agent and aluminum powder as pore-forming agents in lightweight geopolymer synthesis
  156. Synthesis of high surface area mesoporous silica SBA-15 by adjusting hydrothermal treatment time and the amount of polyvinyl alcohol
  157. Review of large-pore mesostructured cellular foam (MCF) silica and its applications
  158. Ion Exchange of Benzoate in Ni-Al-Benzoate Layered Double Hydroxide by Amoxicillin
  159. Synthesis And Characterization Of CoMo/Mordenite Catalyst For Hydrotreatment Of Lignin Compound Models
  160. Production of Biodiesel from Nyamplung (Calophyllum inophyllum L.) using Microwave with CaO Catalyst from Eggshell Waste: Optimization of Transesterification Process Parameters
  161. The Study of the Optical Properties of C60 Fullerene in Different Organic Solvents
  162. Composite Material Consisting of HKUST-1 and Indonesian Activated Natural Zeolite and its Application in CO2 Capture
  163. Topical Issue on Environmental Chemistry
  164. Ionic liquids modified cobalt/ZSM-5 as a highly efficient catalyst for enhancing the selectivity towards KA oil in the aerobic oxidation of cyclohexane
  165. Application of Thermal Resistant Gemini Surfactants in Highly Thixotropic Water-in-oil Drilling Fluid System
  166. Screening Study on Rheological Behavior and Phase Transition Point of Polymer-containing Fluids produced under the Oil Freezing Point Temperature
  167. The Chemical Softening Effect and Mechanism of Low Rank Coal Soaked in Alkaline Solution
  168. The Influence Of NO/O2 On The NOx Storage Properties Over A Pt-Ba-Ce/γ-Al2O3 Catalyst
  169. Special Issue on the International conference CosCI 2018
  170. Design of SiO2/TiO2 that Synergistically Increases The Hydrophobicity of Methyltrimethoxysilane Coated Glass
  171. Antidiabetes and Antioxidant agents from Clausena excavata root as medicinal plant of Myanmar
  172. Development of a Gold Immunochromatographic Assay Method Using Candida Biofilm Antigen as a Bioreceptor for Candidiasis in Rats
  173. Special Issue on Applied Biochemistry and Biotechnology 2019
  174. Adsorption of copper ions on Magnolia officinalis residues after solid-phase fermentation with Phanerochaete chrysosporium
  175. Erratum
  176. Erratum to: Sand Dune Characterization For Preparing Metallurgical Grade Silicon
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