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1.
Kinetics of the liquid‐phase catalytic hydrogenation of m‐phenoxybenzaldehyde to m‐phenoxybenzyl alcohol have been investigated over the Raney nickel catalyst. Effects of hydrogen partial pressure (500‐2000 kPa), catalyst loading (1.6‐6.4 g.L?1), m‐phenoxybenzaldehyde concentration (0.2‐0.8 mol.L?1) and temperature (333‐363 K) on the progress of the reaction were studied. The speed of stirring > 15 rps has no effect on the initial rate of reaction. Effects of various catalysts and solvents on the hydrogenation of m‐phenoxybenzaldehyde have been investigated. The reaction was found to be first order with respect to the hydrogen partial pressure, catalyst loading and m‐phenoxybenzaldehyde concentration. Several Langmuir‐Hinshelwood type models were considered and the experimental data fitted to the model involving surface reaction, between dissociatively adsorbed hydrogen and molecularly adsorbed m‐phenoxybenzaldehyde. 相似文献
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The kinetics of the liquid‐phase catalytic hydrogenation of p‐chlorobenzophenone have been investigated over a 5 % Pd/C catalyst. The effects of hydrogen partial pressure (800–2200 kPa), catalyst loading (0.4–1.6 gm dm–3), p‐chlorobenzophenone concentration (0.37–1.5 mol dm–3), and temperature (303–313 K) were studied. A stirring speed > 20 rps has no effect on the initial rate of reaction. Effects of various catalysts (Pd/C, Pd/BaSO4, Pd/CaCO3, Pt/C, Raney nickel) and solvents (2‐propanol, methanol, dimethylformamide, toluene, xylene, hexane) on the hydrogenation of p‐chlorobenzophenone were also investigated. The reaction was found to be first order with respect to hydrogen partial pressure and catalyst loading, and zero order with respect to p‐chlorobenzophenone concentration. Several Langmuir‐Hinshelwood type models were considered and the experimental data fitted to a model involving reaction between adsorbed p‐chlorobenzophenone and hydrogen in the liquid phase. 相似文献
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B Halligudi Surekha S Khaire 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2002,77(1):25-28
Hydrogenation of 4‐chloro‐2‐nitrophenol (CNP) was carried out at moderate hydrogen pressures, 7–28 atm, and temperatures in the range 298–313 K using Pt/carbon and Pd/γ‐Al2O3 as catalysts in a stirred pressure reactor. Hydrogenation of CNP under the above conditions gave 4‐chloro‐2‐aminophenol (CAP). Dechlorination to form 2‐aminophenol and 2‐nitrophenol is observed when hydrogenation of CNP is carried out above 338 K, particularly with Pd/γ‐Al2O3 catalyst. Among the catalysts tested, 1%Pt/C was found to be an effective catalyst for the hydrogenation of CNP to form CAP, exclusively. To confirm the absence of gas–liquid mass transfer effects on the reaction, the effect of stirring speed (200–1000 rpm) and catalyst loading (0.02–0.16 g) on the initial reaction rate at maximum temperature 310 K and substrate concentration (0.25 mole) were thoroughly studied. The kinetics of hydrogenation of CNP carried out using 1%Pt/C indicated that the initial rates of hydrogenation had first order dependence with respect to substrate, catalyst and hydrogen pressure in the range of concentrations varied. From the Arrhenius plot of ln rate vs 1000/T, an apparent activation energy of 22 kJ mol?1 was estimated. © 2001 Society of Chemical Industry 相似文献
4.
Yingxin Liu Zuojun Wei Shuguang Deng Jiyan Zhang 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2009,84(9):1381-1389
BACKGROUND: Liquid‐phase catalytic hydrogenation of m‐dinitrobenzene is an environmentally friendly routine for m‐phenylenediamine production. The key to increasing product yield is to develop catalysts with high catalytic performance. In this work, La2O3‐modified Ni/SiO2 catalysts were prepared and applied to the hydrogenation of m‐dinitrobenzene to m‐phenylenediamine. The effect of La2O3 loading on the properties of Ni/SiO2 was investigated. The reaction kinetic study was performed in ethanol over Ni/3%La2O3–SiO2 catalyst, in order to clarify the reaction mechanism of m‐dinitrobenzene hydrogenation. RESULTS: It was found that the activity of the silica supported nickel catalysts is obviously influenced by La2O3 loading. Ni/3%La2O3–SiO2 catalyst exhibits high activity owing to its well dispersed nickel species, with conversion of m‐dinitrobenzene and yield of m‐phenylenediamine up to 97.1% and 94%, respectively. The results also show that Ni/3%La2O3–SiO2 catalyst can be reused at least six times without significant loss of activity. CONCLUSION: La2O3 shows strong promotion of the effect of Ni/SiO2 catalyst for liquid‐phase hydrogenation of m‐dinitrobenzene. La2O3 loading can affect the properties of Ni/SiO2 catalyst. Based on the study of m‐dinitrobenzene hydrogenation kinetics over Ni/3%La2O3–SiO2 catalyst, a possible reaction mechanism is proposed. Copyright © 2009 Society of Chemical Industry 相似文献
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The oxidation of benzyl alcohol by molecular oxygen in the liquid phase and catalyzed by Pt/ZrO2 using n‐heptane as the solvent was studied. Pt/ZrO2 was very active and 100 % selective for benzyl alcohol conversion to benzaldehyde. The catalyst can be separated by filtration and reused. No leaching of Pt or Zr into the solution was observed. Typical batch reactor kinetic data were obtained and fitted to the Langmuir‐Hinshelwood, Eley‐Rideal and Mars‐van Krevelen models of heterogeneously catalyzed reactions. The Langmuir‐Hinshelwood model was found to give a better fit. The rate‐determining step was proposed to involve direct interaction of an adsorbed oxidizing species with the adsorbed reactant or an intermediate product of the reactant. H2O2 was also proposed to be an intermediate product. n‐Heptane was found to be an appropriate solvent in this reaction system. 相似文献
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The hydrogenation of dienes such as 1,3‐butadiene, cyclooctadiene, and of acetylenic hydrocarbons on Pd catalysts shows high reaction rates and consequently, a strong influence of mass transfer on the selectivity of the intermediate alkene or cycloalkene product. 100 % selectivity towards (cyclo)‐alkene hydrogenation is achieved for the gas phase when the Thiele modulus is , where L is the thickness of the active layer and Deff is the effective diffusion coefficient of the diene. The interdependencies expressed by this formula were studied in detail using model catalysts with regular pores of uniform length and diameter and perpendicular to the surface. These catalysts were prepared by anodic oxidation of aluminium wires and immobilization of the active Pd. For the liquid phase procedure of selective hydrogenation, a reaction mass transfer model has been derived in order to compare the gas phase and liquid phase procedures, in particular with respect to the selectivity. The hydrogenation of 1,3‐cyclooctadiene and of 1,3‐butadiene were studied for both procedures employing the same catalyst. The rate of hydrogenation can be represented for both cases by the identical kinetic equation r1 = k1 cH2. This result is interpreted by assuming that the access of hydrogen to the surface through the dense layer of adsorbed diene is the rate determining step. 相似文献
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Liquid‐phase hydrogenation using a Pd/Al2O3 catalyst provides a potential technique for the reduction of cumene hydroperoxide (CHP) to α‐cumyl alcohol (CA). In this paper, CHP hydrogenation was carried out in a cocurrent downflow trickle‐bed reactor over a wide range of reaction conditions to study the reaction and deactivation kinetics. The proposed intrinsic rate expression for CHP hydrogenation is based on an Eley‐Rideal mechanism that accounts for an irreversible surface reaction between the absorbed CHP with nonabsorbed hydrogen molecules. During CHP hydrogenation, an exponential decay in activity of the Pd/Al2O3 catalyst and the presence of residual activity were observed. A kinetic deactivation model with residual activity was developed. Based on reaction and deactivation kinetics, catalyst deactivation was attributed to oxidation of the catalyst surface by CHP. The presence of residual activity was due to the partial reduction of oxidized catalyst surface by hydrogen. 相似文献
10.
Helen L. Ngo Robert O. Dunn Eunha Hoh 《European Journal of Lipid Science and Technology》2013,115(6):676-683
Iso‐oleic acid is a mixture of C18‐unsaturated branched‐chain fatty acid isomers with a methyl group on various positions of the alkyl chain, which is the product of the skeletal isomerization reaction of oleic acid and is the intermediate used to make isostearic acid (C18‐saturated branched‐chain fatty acid isomers). Methyl iso‐oleate, a mixture of C18‐unsaturated branched‐chain fatty acid methyl ester isomers, is obtained via acid catalyzed esterification of iso‐oleic acid with methanol. The branched‐chain materials are liquid at room temperature and their “oiliness” property makes them an attractive candidate for the lubricant industry. In this paper, we report characterization of these branched‐chain materials using comprehensive two‐dimensional GC with time‐of‐flight mass spectrometry (GC × GC/TOF‐MS) and their physical and lubricity properties using tribology measurements. 相似文献
11.
The partial hydrogenation of benzene by a Pt nano‐cluster/N‐n‐propyl chitosan hybrid membrane was investigated in this article. Monodispersed Pt nano‐clusters were prepared by the reduction of H2PtCl6 with ethylene glycol under microwave conditions. TEM, FTIR, XRD, 1H‐NMR, and XPS were used to characterize the structure of Pt nano‐particles, N‐n‐propyl chitosan and Pt/N‐n‐propyl chitosan hybrid membrane, respectively. Experimental results showed that Pt/N‐n‐propyl chitosan hybrid membrane catalyst gave a high selectivity for cyclohexene of 85.2% in the liquid phase hydrogenation of benzene, while the selectivity of cyclohexene was only 58.2% over the Pt/chitosan hybrid membrane catalyst. It was worth noting that there was no cyclohexene in the product when the catalyst was only Pt nano‐particles without chitosan hybrid membrane. So the chitosan or modified‐chitosan membranes played an important role in the controlling to the hydrogenation of benzene, and the relationship of the swelling degree and the catalytic activity was discussed in detail. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 相似文献
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A homogeneous RuCl2(PPh3)3 catalyst was prepared for the hydrogenation of bio‐oil to improve its stability and fuel quality. Experiments were first performed on three model aldehydes of acetaldehyde, furfural and vanillin selected to represent the linear aldehydes, oxygen heterocyclic aldehydes and aromatic aldehydes in bio‐oil. The results demonstrated the high hydrogenation capability of this homogeneous catalyst under mild conditions (55–90 °C, 1.3–3.3 MPa). The highest conversion of the three model aldehydes was over 90 %. Furfural and acetaldehyde were singly converted to furfuryl alcohol and ethanol after hydrogenation, while vanillin was mainly converted to vanillin alcohol, together with a small amount of 2‐methoxy‐4‐methylphenol and 2‐methoxyphenol. Further experiments were conducted on a bio‐oil fraction extracted by ethyl acetate and on the whole bio‐oil at 70 °C and 3.3 MPa. Most of the aldehydes were transformed to the corresponding alcohols, and some ketones and compounds with C–C double bond were converted to more stable compounds. 相似文献
14.
Karuppan Muthukumar Balakrishnan Naveen Prasad Manickam Velan 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2004,79(12):1376-1380
In the present investigation the effects of the addition of organic additives (propanol, benzoic acid, iso‐amyl alcohol and carboxymethyl cellulose) on the critical gas velocity, (Usg)c, in an internal airlift loop reactor with low‐density particles (Nylon‐6 and polystyrene) were reported. Whereas the (Usg)c was reduced by adding the above additives, it increased with solids loading and density of the particles. The draft tube‐to‐reactor diameter ratio (DE/D) in the range of 0.5–0.6 gave minimum (Usg)c values. The proposed dimensionless correlation predicted the experimental data well. Copyright © 2004 Society of Chemical Industry 相似文献
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The ternary neodymium versatate (NdV3)‐based catalyst system, NdV3/SiCl4/Al(iso‐Bu)2H, for the stereospecific polymerization of 1,3‐butadiene (Bd) has been studied at a catalyst concentration of 0.11 mmol Nd per 100 g Bd. The effects of the concentration of SiCl4 following in situ activation, preformed at 20 °C in the presence and absence of isoprene and the substitution of Al(iso‐Bu)2H with AlEt3 as alkylating agent, were established and compared to the performance of NdV3‐based catalyst systems incorporating ethylaluminium sesquichloride (EASC), diethylaluminium chloride (DEAC) and t‐butyl chloride (t‐BuCl) as chloride sources. Comparable catalytic activity between the control catalysts based on EASC, DEAC and t‐BuCl and the studied NdV3/SiCl4/Al(iso‐Bu)2H system was achieved once the optimum concentration ratios of NdV3/SiCl4/Al(iso‐Bu)2H = 1:1:25 were applied in conjunction with preforming the catalyst components in the presence of isoprene for 72 h at 20 °C. Polybutadiene cis‐1,4 contents were consistently high (about 97 %) for all polymerizations. © 2000 Society of Chemical Industry 相似文献
16.
Zhiming Zhou Tianying Zeng Zhenmin Cheng Weikang Yuan 《American Institute of Chemical Engineers》2011,57(8):2198-2206
A novel Pd/Al2O3 catalyst with the hierarchically macro‐mesoporous structure was prepared and applied to the selective hydrogenation of pyrolysis gasoline. The alumina support possessed a unique structure of hierarchical mesopores and macropores. The as‐prepared and calcined alumina were characterized by X‐ray diffraction, N2 adsorption‐desorption, and scanning electron microscopy. It showed that the hierarchically porous structure of the alumina was well preserved after calcination at 1073 K, indicating high thermal stability. The 1073 K calcined alumina was impregnated with palladium metal and compared with a commercial catalyst without macrochannels. Both the catalytic activity and the hydrogenation selectivity of the novel Pd/Al2O3 catalyst were higher than those of the commercial Pd/Al2O3 catalyst. In addition, apparent reaction activation energies obtained with the novel catalyst for model pyrolysis gasoline were 46–81% higher than those with the commercial catalyst. The results adequately demonstrated the enhanced mass transfer characteristics of the novel macro‐mesostructured catalyst. © 2010 American Institute of Chemical Engineers AIChE J, 2011 相似文献
17.
Jens Theuerkauf Giancarlo Franci Walter Leitner 《Advanced Synthesis \u0026amp; Catalysis》2013,355(1):209-219
A continuous‐flow process for the asymmetric hydrogenation of methyl propionylacetate as a prototypical β‐keto ester in a biphasic system of ionic liquid and supercritical carbon dioxide (scCO2) is presented. An established ruthenium/2,2′‐bis(diphenylphosphino)‐1,1′‐binaphthyl (BINAP) catalyst was immobilised in an imidazolium‐based ionic liquid while scCO2 was used as mobile phase transporting reactants in and products out of the reactor. The use of acidic additives led to significantly higher reaction rates and enhanced catalyst stability albeit at slightly reduced enantioselectivity. High single pass conversions (>90%) and good enantioselectivity (80–82% ee) were achieved in the first 80 h. The initial catalyst activity was retained to 91% after 100 h and to 69% after 150 h time‐on‐stream, whereas the enantioselectivity remained practically constant during the entire process. A total turnover number of ∼21,000 and an averaged space‐time yield (STYav) of 149 g L−1 h−1 were reached in a long‐term experiment. No ruthenium and phosphorus contaminants could be detected via inductively coupled plasma optical emission spectrometry (ICP‐OES) in the product stream and almost quantitative retention by the analysis of the stationary phase was confirmed. A comparison between batch‐wise and continuous‐flow operation on the basis of these data is provided. 相似文献
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Maryam Takht Ravanchi Saeed Sahebdelfar Maryam Rahimi Fard Siavash Fadaeerayeni Peyman Bigdeli 《化学工程与技术》2016,39(2):301-310
The selective hydrogenation of acetylene to ethylene over Pd‐Ag/α‐Al2O3 catalysts prepared by different impregnation/reduction methods was studied. The best catalytic performance was achieved with the sample prepared by sequential impregnation. A kinetic model based on first order in acetylene and 0.5th order in hydrogen for the main reaction and second‐order independent decay law for catalyst deactivation was used to fit the conversion time data and to obtain quantitative assessment of catalyst performances. Fair fits were observed from which the reaction and deactivation rate constants were evaluated. Coke deposition amounts showed a good correlation with catalyst deactivation rate constants, indicating that coke formation should be the main cause of catalyst deactivation. 相似文献
19.
Nuray Oktar Krali Mürtezaolu Gülen Dou lknur Gnderten Timur Dou 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1999,74(2):155-161
Etherification of C5 reactive olefins available in light fluidized catalytic cracking (FCC) gasoline is an attractive way to decrease the olefins and to increase the octane number. The reactivities of 2‐methyl‐1‐butene (2M1B) and 2‐methyl‐2‐butene (2M2B) in the etherification reaction with ethanol catalysed by a strongly acidic macroreticular resin catalyst were investigated in a temperature range of 333–360 K using a liquid phase differential flow reactor. In the presence of excess alcohol, the apparent reaction orders of etherification reactions of isoamylenes were found to be 0.93 and 0.69 with respect to 2M1B and 2M2B concentrations, respectively. 2M1B was shown to be more reactive than 2M2B and its activation energy is also lower in the etherification reaction. It was also shown that diffusion resistances, especially in the macropores of the catalyst, may play an important role on the observed rates. © 1999 Society of Chemical Industry 相似文献
20.
In the present study, a model is established to describe the propylene polymerization kinetics catalyzed by the typical catalysts with single‐/multi‐active site type in a liquid phase stirred‐tank reactor using the Monte Carlo simulation method, regardless of the mass and heat diffusion effects within the polymer particles. Many kinetic data, including polypropylene yield, concentration transformation of catalyst active sites, number–average molecular weight, etc., are obtained by the model. The simulated kinetic results are found to be in agreement with the reference ones obtained in a population balance model. Furthermore, the comparisons of the kinetic data between the polymerization catalyzed by the catalyst with single‐active site type (typically silica‐supported metallocene) and the catalyst with multi‐active site type (typically MgCl2‐supported Ziegler‐Natta catalyst) have been studied using the model. Especially, the effects of hydrogen on the polymerization are studied using the model. The studied results show that the theory of catalyst active site can be used to explain the different propylene polymerization kinetics catalyzed by the typical catalyst with single‐/multi‐active site type. In addition, the role of hydrogen in the propylene polymerization needs to be emphasized. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献