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Reaction Kinetics, Mechanisms and Catalysis
Journal Prestige (SJR): 0.409  Citation Impact (citeScore): 2 Number of Followers: 3  Hybrid journal (It can contain Open Access articles)ISSN (Print) 1878-5190 - ISSN (Online) 1878-5204 Published by Springer-Verlag  [2469 journals]
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- Mg(NO3)2·6H2O-modified porous carbon derived from peanut shell: formation
mechanism and efficient removal of p-nitrophenol-
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Abstract: Mg(NO3)2·6H2O-modified porous carbon derived from peanut shell (PS) (MN-PSC) was fabricated by a facile one-step approach, i.e., direct calcining the mixture of PS and Mg(NO3)2·6H2O (MN). The effects of calcination temperature, time and PS-MN ratio on the structure, texture, morphology and p-nitrophenol (pNP) adsorption of MN-PSC were investigated via characterization techniques such as XRD, TG-DSC, SEM, N2 adsorption/desorption and batch adsorption. The results show MN obviously decreased PS’s carbonization temperature. An interconnected pore structure was formed in MN-PSC with a surface area of 773.5 m2 g−1 and pore volume of 0.5310 m3 g−1 as the pyrolysis procedure is 200 °C for 1 h coupled with 750 °C for 2 h and the mass ratio of PS and MN is 1:1 (MN-PSC750–2). The formation mechanism of MN-PSC750–2 is that MN is firstly decomposed as MgO and oxidants such as NO2, O2 and HNO3 at 200 °C. These oxidants make PS cellulose carbonization in-situ form initial biochar-MgO with micropores and mesopore. MgO was blown out at 750 °C from inner biochar to form porous biochar with micro-, meso- and macro-pores. The adsorption capacity of MN-PSC750–2 for pNP is 106.95 mg g−1, which is obviously higher than those of PSCs due to the MN-PSC750–2’s well ordered porosity and the exist of functional group (C=O).
PubDate: 2022-05-11
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- Asymmetric reduction of 4-trimethylsilyl-3-butyn-2-one to
(R)-4-trimethylsilyl-3-butyn-2-ol catalyzed by a novel strain lyophilized
Acetobacter sp. CCTCC M209061 in an aqueous/ionic liquid biphasic system-
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Abstract: Abstract In the present work, the feasibility of synthesis of enantiopure (R)-4-(trimethylsilyl)-3-butyn-2-ol {(R)-TMSBL} in aqueous/ionic liquid (IL) mediated system catalyzed by lyophilized Acetobacter sp. CCTCC M209061 was systematically evaluated. Results showed that C4MIm·PF6-based biphasic system exhibited the best biocompatibility with the cells, the biocatalytic reduction proceeded with the fastest initial reaction rate and the highest substrate conversion. Furthermore, effect of various variables on the reaction were intensively investigated. The results showed that the optimal volume ratio of buffer to C4MIm·PF6, buffer pH, substrate concentration, and incubation temperature were 4:1, 5.0, 60 mmol/L, 30 °C. Under the optimal conditions, the initial reaction rate, maximum substrate conversion, and product e.e. were 9.4 µmol/h, 93%, and > 99%. More interestingly, after being repeated for 8 batches (50 h per batch), the cells remained over 80% of their original activity in the C4MIm·PF6 based biphasic system, which was higher than that in the monophasic buffer system (64.7%), indicating that C4MIm·PF6 is a promising candidate medium for biocatalytic synthesis of (R)-TMSBL.
PubDate: 2022-04-24
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- Efficient catalytic dehydration of fructose into 5-hydroxymethylfurfural
by carbon dioxide-
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Abstract: Abstract To enhance the selective fructose dehydration to 5-hydroxymethylfurfural (HMF), an efficient dehydration of fructose to 5-HMF in H2O-MIBK- pressured CO2 in 20 min at 200 °C with a better product yield of 85.6% and 89.1% product selectivity was achieved. The high activity attributed to the combination of the weak acidity by CO2 dissolved in the water and the efficient separation of fructose with 5-HMF in this H2O-MIBK two-phase system. The possible reaction mechanism is discussed. It was found that the solvents ratio was the one of key factors determining the yield of target products. Compared to the related reported results in the reaction, this process characterized of more favorable product yield and higher selectivity, it can be considered as a potential technique for the scale-up production of 5-HMF from fructose.
PubDate: 2022-04-15
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- Semi-analytical expressions for the concentrations and effectiveness
factor for the three general catalyst shapes-
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Abstract: Abstract In this contribution, a Langmuir–Hinshelwood–Hougen–Watson (LHHW) type kinetic model is discussed for simple one-dimensional geometry of porous catalysts such as a sphere, infinite cylinder, and flat pellets. The system is described in finite-range Fickian diffusion and nonlinear reaction kinetics to produce a nonlinear reaction–diffusion equation. This paper aims to employ efficient and reliable approximate analytical methods to derive semi-analytical expressions for species concentrations and the effectiveness factor for the underlying kinetic model. The accuracy of the derived approximate analytical expressions of the concentrations is validated by directed comparison with derived numerical simulations. The analytical expressions will simplify investigating the effect of various parameters on the concentration and effectiveness factor.
PubDate: 2022-04-12
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- Comparison of two new graphene-based magnetic and non-magnetic
nanocatalysts for Suzuki–Miyaura coupling and optimization of reaction
conditions using design of experiment (DoE)-
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Abstract: Abstract In this study, hydantoin derivative 5-methyl-5-(4-pyridyl)hydantoin (HL) was covalently functionalized onto graphene oxide/magnetic graphene oxide nanosheets. The chemical structure of the functionalized graphene oxide nanosheets and the HL were characterized with FT-IR, XRD, EDS, TEM, UV–Vis, FE-SEM, 1H, and 13C NMR spectra. We demonstrate that the (GO/HL-Pd) and (NPs@GO/HL-Pd) compounds can act as efficient nano-catalyst for the Suzuki–Miyaura reaction under aqueous and aerobic conditions in a short time. The effect of the concentration of the variable such as temperature, time, base, and nano-catalysts value on the performance of the Suzuki–Miyaura reaction was evaluated using statistical methods (DoE) for both synthesized nanocatalysts in a systematic sequential study. According to the results, the magnetized compound with iron nanoparticles has a higher catalytic activity. Therefore, the optimum point of the design involves a 3.3 ml solvent, 0.0175 mol% of NPs@GO/HL-Pd catalyst, 2.75 eq K2CO3, furthermore a 3.5 h reaction time, and reaction temperature of 77.5 °C. Optimal conditions lead to the maximum yield value. Furthermore, the as-prepared nano-catalysts can be easily recovered and reused after a catalysis reaction.
PubDate: 2022-04-12
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- Synthesis, characterization and kinetics of sustained pantoprazole release
studies of interpenetrated poly(acrylic acid)-chitosan-bentonite hydrogels
for drug delivery systems-
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Abstract: Abstract Clays are widely used in controlled drug delivery systems due to their strong adsorption properties and natural origin. In this study, a drug carrier was prepared using chitosan, a natural polymer, mixed with bentonite clay. Then, poly(acrylic acid) was added to improve its swelling properties. Pantoprazole was chosen as the model drug. The swelling properties of the prepared samples were investigated at two different temperatures: 25 and 37 °C. The prepared samples were examined by Fourier-transform infrared spectroscopy and scanning electron microscopy. The controlled release of the pantoprazole from the drug carriers indicated that the release of the pantoprazole is temperature-sensitive. In order to study the effect of bentonite on the drug carrier system, drug release was also investigated in the samples without adding clay. It was observed that the drug release profiles of the prepared sample containing bentonite fitted better than the sample without clay. The release kinetics analysis showed that the first-order and the Korsmeyer-Peppas models fit the best, and that pantoprazole was transported via Fickian diffusion. The prepared samples showed the capability of pantoprazole loading and, thus, its possibility to be used in drug delivery systems.
PubDate: 2022-04-10
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- A temperature-sensitive modified imprinted Ag-Poly (o-phenylenediamine)
photocatalyst synthesized by microwave method for efficient degradation of
ciprofloxacin-
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Abstract: Abstract The magnetic carbon material was synthesized by a simple solid-phase method, and a modified imprinting layer was formed on the surface of the magnetic carbon material by molecular imprinting and microwave methods, and the final modified imprinted Ag-Poly (o-phenylenediamine) (Ag-POPD) photocatalyst was used to degrade the antibiotic ciprofloxacin. The as prepared photocatalyst is very sensitive to temperature, and the ciprofloxacin degradation rate in ambient environment (25 °C) was 73.25% higher than at 40 °C. The photocatalyst has high selectivity to ciprofloxacin and is convenient to recover due to its magnetic properties. The significant increase in photocatalytic activity is mainly attributed to the synergistic effect between Ag and magnetic carbon materials that can accelerate the spatial separation of charge carriers. Furthermore, details of the photocatalytic degradation mechanism of the photocatalyst composite are discussed. The described method is a new single-step continuous microwave synthesis, which also opens new ways to modify/tune materials.
PubDate: 2022-04-09
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- Effect of reaction conditions and kinetics of the isomerization of
β-pinene epoxide to myrtanal in the presence of Fe/MCM-41 and Fe/SBA-15-
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Abstract: Biomass valorization by isomerization of β-pinene epoxide was carried out over Fe supported on MCM-41 and SBA-15 materials. Several reaction conditions (kind of solvent, amount of catalyst, temperature, and time) were evaluated; myrtanal selectivity up to 85% was obtained (70 °C, 750 rpm, acetonitrile as solvent, 24 h) at a conversion of 99%. Apparently, solvent polarity affect myrtanal selectivity; the lowest conversions were obtained with the cyclic molecules THF and dioxane that have oxygen which pair electron free could be coordinated to the Fe center. Amount of catalyst increases availability of the active sites in the reaction medium which improves the conversion, nevertheless myrtanal selectivity did not change in the case of Fe/SBA-15. Yield to myrtanal increased as the amount of catalyst was raised. Estimated kinetic reaction constants for β-pinene epoxide isomerization over Fe/MCM-41 and Fe/SBA-15 were 1.6285 mol0.4 h−0.4 gFe−1 and 0.1404 mol1.7 h−1.7 gFe−1, respectively. Apparently, β-pinene epoxide is more strongly adsorbed on Fe/SBA-15 than on Fe/MCM-41 catalyst. Fe/SBA-15 is a very attractive material for obtaining myrtanal with a high yield (up to 85%) and it is one of the best materials reported up to now for the synthesis of this aldehyde. Graphical abstract
PubDate: 2022-04-09
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- Glucose-derived carbon-coated Ni–In intermetallic compounds for in situ
aqueous phase selective hydrogenation of methyl palmitate to hexadecanol-
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Abstract: Abstract The carbon-coated Ni (Ni@C) and Ni–In intermetallic compounds (IMCs) (Ni–In@C) catalysts were synthesized via combining one-pot hydrothermal method with glucose as carbon source and the carbonization under N2 atmosphere. Their reactivities were compared in in situ aqueous phase selective hydrogenation of methyl palmitate to hexadecanol using methanol as a H2 donor. The Ni@C catalyst dominatingly catalyzes decarbonylation/decarboxylation, accompanying with the serious C–C bond hydrogenolysis and methanation. In contrast, hexadecanol is mainly generated on Ni–In@C, where C–C bond hydrogenolysis and methanation are remarkably inhibited. This is ascribed to the geometric and electronic property of Ni–In IMCs. The hexadecanol yield reaches 84.0% under an optimal condition on Ni–In@C. The structure of NiIn IMC is hydrothermally stable even at 330 °C, and the Ni–In IMCs particles highly resist to sintering and leaching under harsh hydrothermal condition due to the confinement of carbon. Catalyst deactivation is mainly due to the carbonaceous deposition, and the catalyst reactivity is mostly recovered by the regeneration with CO2.
PubDate: 2022-04-08
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- Solar photodegradation of Solophenyl Red 3BL and Neuro-Fuzzy modeling:
kinetic, mechanism and mineralization studies-
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Abstract: Abstract The photocatalytic degradation of a toxic textile azo dye namely Solophenyl Red 3BL has been investigated under solar light using TiO2 as catalyst. The influence of operational parameters such as catalyst dose (0.1–1 g/L), pH solution (2.5–11) and initial concentration (CO: 5–75 ppm) on the photodegradation efficiency was examined. During 130 min of treatment, a photocatalytic efficiency of 95% was obtained for a concentration of 5 ppm and a catalyst dose of 0.5 g/L at natural pH (~ 6.7). The photocatalytic process is well described by the Langmuir–Hinshelwood (L–H) model. A comparative study showed that the solar radiation is more efficient than the UV light on the photocatalytic process and the catalyst performance reached 98% of dye degradation after five consecutive cycles. The total mineralization of the pollutant to CO2, H2O and mineral salts was achieved but requires a longer time comparatively to its degradation. According to the degradation mechanism, it was found that all species: ·OH, −O2·, h+ and e− contribute to the dye photodegradation. Adaptive Neuro-Fuzzy Inference Systems has been successfully employed to simulate the photocatalytic process and to predict the Solophenyl Red 3BL degradation yield. Statistical errors and graphical plots were used to assess the accuracy of the intelligent model. The determination coefficient and the mean absolute error were 0.982 and 0.707, respectively. The obtained results displayed an excellent accuracy of the developed ANFIS model.
PubDate: 2022-04-08
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- Ruthenium on α-Ni(OH)2 as potential catalyst for anisole hydrotreating
and cinnamyl alcohol oxidation-
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Abstract: Abstract Ruthenium containing α-Ni(OH)2 was prepared by a simple impregnation method, the resultant materials with 4 wt% ruthenium loaded nickel hydroxide forms a solid solution of Ni–Ru mixed metal oxide upon calcination. The formation of uniform layered α-nickel hydroxide with ruthenium dispersed on the surface was evident from various analytical and spectroscopic techniques such as powder XRD, XPS, FT-IR and sorption studies. The Ni–Ru-HT catalyst under hydrogen atmosphere showed as a potential catalyst for hydrotreating of anisole with good conversion (90% at 175 °C and 20 bar H2 pressure), with the formation of toluene as a major product along with a considerable amount of methylcyclohexane and benzene as the minor products. The formation of a solid solution of mixed oxide and the dispersion of Ni and Ru on the surface of the oxide enhanced the catalytic activity. Further, the material obtained by calcination at 200 °C is active for the oxidation of cinnamyl alcohol in the presence of tertiary-butyl-hydroperoxide (TBHP) in decane as an oxidant under ambient conditions (90 °C and 6 h). A maximum of 84% conversion of cinnamyl alcohol and more than 80% selectivity for cinnamaldehyde was obtained on the best catalyst. The activity remains intact even after four cycles. The ruthenium on α-Ni(OH)2 was found to be a potential catalyst for the conversion of lignin model compounds to value-added chemicals.
PubDate: 2022-04-08
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- Simple synthesis of high photocatalytic activity TiO2 nanopowder with
sodium dodecylbenzene sulfonate surfactant for photocatalysis of rhodamine
B and methyl orange-
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Abstract: Abstract In this study, the TiO2 nanopowder with high photocatalytic activity has been successfully synthesized by a simple solvothermal method process without annealing by sodium dodecyl benzene sulfonate(SDBS) as surfactants. Meanwhile, effects of SDBS content on photocatalytic activity and properties of the TiO2 nanopowder were systematically examined by the XRD, SEM, TEM, BET, XPS, UV–Vis DRS, TOC, photoelectrochemical and photodegradation experiments. The sample T without modification showed good photocatalytic performance under visible light irradiation. Its degradation efficiency of rhodamine B (RhB) and methyl orange (MO) was 3.6 times and 3.1 times that of P25, respectively. With the increase of the SDBS content, the photocatalytic activity of TiO2 nanopowder was significantly improved. For degradation of RhB, the photocatalytic degradation efficiency of T-1.0wt%SDBS is 51 times that of P25. For degradation of MO, the photocatalytic degradation efficiency of T-1.0wt%SDBS is 5.3 times that of P25. And the related mechanisms were studied. These experimental results show that adding a small amount of SDBS in the simple synthesis process can observably enhance the specific surface area of TiO2 and the amount of adsorbed O2 and H2O, thereby greatly improves the photocatalytic activity.
PubDate: 2022-04-07
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- Influence of alumina pH on properties of Fe2O3/Al2O3 catalyst for
high-density polyethylene decomposition to H2 generation-
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Abstract: A synthesis of Fe2O3 supported on acid, neutral and basic Al2O3 was carried out by an incipient wet impregnation to test the obtained materials on catalytic decomposition of a high-density polyethylene reaction of H2 production. All materials were characterized by an X-ray diffraction, scanning electron microscopy, energy dispersion spectroscopy, surface area and the H2 and CH4 production by gas chromatography. Results show that the crystal size, particle size and surface area decrease as the pH of the supports increases, the morphology, and the dispersion of the nanoparticles of Fe2O3. This work demonstrates the ability to produce H2 from the catalytic decomposition of high-density polyethylene (Fe2O3/a-Al2O3: 62%) at low temperatures (about 200 °C lower vs other reports). Graphical abstract
PubDate: 2022-04-07
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- Facile and template-free synthesis of nano-macroporous LaCoO3 perovskite
oxide for efficient diesel soot oxidation-
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Abstract: Abstract The basic LaCoO3 perovskite oxides were prepared by the series of methods (reverse co-precipitation, citric acid aided sol–gel, glycine assisted solution combustion), underwent physicochemical characterization (XRD, FTIR, BET, XPS and SEM), followed by their soot oxidation activity tests in both “loose” and “tight” conditions of soot-catalyst contact. The activity tests revealed that the LaCoO3 catalyst formed using glycine assisted combustion synthesis gives the best performance with the T10, T50, and T90 at 361 °C, 404 °C and 445 °C, respectively, in loose contact conditions and T10, T50, and T90 at 306 °C, 330 °C and 355 °C, respectively, in tight contact conditions. Its outstanding performance can be attributed to its unique morphology consisting of scaffolds having an extensively interconnected macroporous network with macropores having nanoporous struts as walls as evidenced by SEM results. Such morphology makes the active sites of inner pores accessible to the gaseous (air) as well solid reactant (soot particles), thereby benefitting soot oxidation reaction.
PubDate: 2022-04-05
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- Facile preparation of a Lewis acidic copper 1,3,5-benzenetricarboxylate
with nanopore confinement superiority effect for enhanced catalytic
Claisen-Schmidt condensation-
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Abstract: Abstract Three copper 1,3,5-benzenetricarboxylate (Cu-BTC) samples were prepared by facile solvothermal methods in two mixed solvents (DMF/EtOH/H2O and EtOH/H2O), and through steam-assisted conversion process (SAC). Furthermore, the physicochemical and spectroscopic analysis indicated the morphology, porosity and Lewis acidity of Cu-BTC samples could be easily changed by adjusting the kinds and amounts of solvents. The catalytic performance for synthesis of chalcone over three Cu-BTC samples was studied. It was found that Cu-BTC-STE shown a smaller acidic amount of 9.2 mmol/g, but presented the maximum yield of 84%, which was ascribed to its nanopore confinement superiority effect. Moreover, Cu-BTC-STE was easy for separation catalyst/product by the simple filtration and reused at least four recycles.
PubDate: 2022-04-04
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- Effect of complexation between cobinamides and bovine serum albumin on
their reactivity toward cyanide-
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Abstract: Abstract Here, we report results of spectrophotometric, spectrofluorimetric, and ultrafiltration studies on the reaction between cobinamides (viz. aquahydroxo-, nitro-, aquacyano- and dicyanocobinamides; Cbi) and bovine serum albumin (BSA), and reactivity of formed complexes toward cyanide. (H2O)(HO−)Cbi binds BSA at almost equimolar ratio predominantly via amino group of lysine side chains. The mechanism of the reaction involves two steps, i.e. the coordination of amino group on Co(III), and further stabilization of the generated complex. The reaction of (H2O)(NO2−)Cbi with BSA is similar with that involving (H2O)(HO−)Cbi, and both complexes bind cyanide significantly slower than free (H2O)(HO−)Cbi and (H2O)(NO2−)Cbi. (H2O)(CN−)Cbi binds BSA predominantly via aminogroup as well, however, its coordination proceeds substantially faster and less tightly than in the case of (H2O)(HO−)Cbi. Binding of (H2O)(CN−)Cbi and (H2O)(HO−)Cbi occurs at different sites of BSA as was indicated by spectrofluorimetric titration. Reaction of the complex between (H2O)(CN−)Cbi and BSA with cyanide proceeds much faster than in the case of the complex between (H2O)(HO−)Cbi and BSA. (CN−)2Cbi is partially decyanated by BSA, however, its binding by BSA is relatively low.
PubDate: 2022-04-04
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- Kinetic modeling and optimization of the operating conditions of benzene
alkylation with ethane on PtH-ZSM-5 catalyst-
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Abstract: Abstract In this work, a Langmuir–Hinshelwood kinetic model was proposed for benzene alkylation with ethane over PtH-ZSM-5 catalyst, based on two-step mechanism of ethane dehydrogenation and benzene alkylation reactions. Further, a network of side reactions was also considered. Reaction rate equations were introduced and the kinetic parameters were optimized using the genetic algorithm to minimize the objective function of deviation between the model and experimental data obtained from an isothermal fixed-bed micro-reactor. In addition, temperature dependence of the rate constants was derived by evaluation of the results at several temperatures of 330, 370, 410, 450, 490 °C. For more evaluation and comparison, a model with elementary reactions was compared with the proposed kinetic model. Results revealed that the proposed model could predict the experimental data with higher precision than the elementary model. Finally, by using this kinetic model, the effect of significant operating conditions such as temperature, pressure, inlet molar ratio of ethane to benzene and contact time was investigated on the products’ distribution to predict the optimal conditions to achieve maximum yield of ethylbenzene in this process.
PubDate: 2022-04-01
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- Experimental and kinetic study of vacuum residue cracking over zirconium
based catalysts-
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Abstract: Abstract In this study, thermal cracking and catalytic cracking over zirconium-based catalysts of the vacuum residue were achieved in the presence of supercritical steam at 400–450 °C, 20 bar, and 2–4 h. Two different catalysts (ZrFeNi and ZrCoNi) were prepared using a sol–gel precipitation method and characterized using X-ray diffraction, EDX-spectrum, scanning electron microscopy, and BET surface area. The results showed the lowest VR conversion was achieved in the thermal cracking, catalytic cracking using ZrFeNi and catalytic cracking using ZrCoNi were 31.7, 35.3, and 38% while the highest VR conversion was achieved in the thermal cracking, catalytic cracking using ZrFeNi and catalytic cracking using ZrCoNi were 38.6, 71.1 and 76.3%. A new kinetic model of the eight lumps and 28 reaction steps were developed to describe the VR cracking while a genetic algorithm optimization method was used to predict the optimum set of kinetic parameters in which all computations were achieved using MATLAB version 2020a.
PubDate: 2022-04-01
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- Direct synthesis of dimethyl carbonate from methanol and carbon dioxide
over nickel loaded ceria as improved catalysts-
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Abstract: Abstract The direct synthesis of dimethyl carbonate (DMC) without a dehydrating agent is challenging but has a significant value. Here we demonstrate the catalytic activity of inexpensive nickel loaded ceria in both batch and continuous processes for this reaction. The prepared catalysts were characterized by various physicochemical characterization techniques. The nickel-loaded ceria catalysts exhibited good catalytic activity for the synthesis of DMC in good yield (4.6 mmol) and 100% selectivity. The yield obtained is nearly six times higher than pristine CeO2, which clearly depicts the role of nickel. Reaction under high pressure continuous flow also provided a similar trend wherein a maximum yield of 15 mmol with 100% liquid phase selectivity of DMC was noted. Density functional theory calculations were carried out to investigate the adsorption energies of CO2 and methanol on pristine ceria and Ni modified ceria. The high catalytic activity of Ni-modified catalyst was attributed to the presence of strong acidic and moderate basic sites as elucidated from temperature-programmed desorption and pyridine adsorption monitored via FT-IR studies. The experiment result revealed that the CexNix−yO2−δ could be a reusable and longer active catalyst for the direct synthesis of DMC.
PubDate: 2022-04-01
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- Ernő Keszei: Reaction kinetics. An introduction
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PubDate: 2022-03-31
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