Catalytic oxidation of propylene to acrolein on a multicomponent oxide catalyst

Rate equations have been found and reaction schemes for oxidation of propylene to acrolein and acrylic acid have been suggested.

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Kinetics of propylene oxidation to acrolein on an Fe?Sb oxide catalyst

The kinetics of propylene oxidation to acrolein and CO₂ on a Fe–Sb oxide catalyst have been studied in an integral reactor. A satisfactory rate equation has been derived with the assumption of a linear dependence of the activation energy and heats of adsorption of oxygen and water on the degree of reduction of the catalyst.

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CO₂ Fe–Sb . , .

     

Bond energy of surface oxygen in multicomponent oxide catalysts for propylene oxidation to acrolein

Bond energy of surface oxygen for the multicomponent oxide catalyst Mo₁₂Bi₁Ni_2.5Fe₃Co_4.5K_0.07P₁/SiO₂ has been measured in conditions of propylene oxidation and found to be 272 kJ/mol.

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Mo₁₂Bi₁Ni_2,5Fe₃Co_4,5K_0.07P₁/SiO₂, , 272 /.

     

丙烯环氧化制环氧丙烷Fe-Al-P-O催化剂的研究

用溶胶-凝胶法制得了Fe-Al-P-O催化剂，采用IR、XRD、TEM、BET、TPR和微反等技术研究了催化剂的物化性质和反应性能。实验结果表明，Fe1/2-Al1/2-PO4由10 nm左右 FePO4和AlPO4微晶组合而成，其晶格氧的活泼性大于单纯FePO4，AlPO4在Fe1/2-Al1/2-PO4中起到分散FePO4微晶的作用；Fe1/2-Al1/2-PO4的反应性能与原料气组成密切相关，丙烯与O2的选择氧化产物主要是丙烯醛，原料气中加入H2后，反应产物以环氧丙烷为主，同时还有部分丙烯醛，原料气中引入水蒸气后，可进一步增加环氧丙烷的选择性及减少丙烯醛的产率；在0.1 MPa、200 ℃、C3H6/O2/H2/H2O/N2=1∶1∶1∶1∶6（mol比）和空速1 200 h－1条件下，丙烯的转化率为8.9％，环氧丙烷的选择性为81.0％。     

Selective oxidation of light alkanes over Mo-based oxide catalysts

A highly reduced Keggin-type heteropolymolybdophosphate, H₃PMo₁₂O₄₀(Py), which was formed by the heat-treatment of pyridinium salt of H₃PMo₁₂O₄₀, can catalyze the propane oxidation to acrylic acid and acetic acid selectively. We propose a possible reaction mechanism for alkane oxidation, where protons and electrons on the reduced H₃PMo₁₂O₄₀ catalyst cooperate for activating molecular oxygen to form electrophilic oxygen species for alkane oxidation. It is also reported that Anderson-type heteropolycompounds linked with vanadyl cations VO²⁺ were able to be synthesized by hydrothermal reaction and showed good catalytic activity for the ethene oxidation to acetic acid.     

Influence of water vapor on propylene oxidation on VMo catalyst

The dependence of reaction rates for acetone and acetic acid formation on the concentration of water vapor is determined on the basis of the participation of surface hydroxy groups and Brönsted acid centers of the catalyst.

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Kinetics of oxidation of acrolein on a vanadium-molybdenum oxide catalyst

A kinetic study has shown that, in the range of low conversions, the reaction rate depends only on the partial pressure of oxygen. Comparison of the oxidation of acrolein and I-deuteroacrolein suggests that the splitting of the H–CO bond is not rate-limiting.

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, , , . 1- , H–CO .

     

Catalytic oxidation of isobutyraldehyde over a molybdenum-vanadium oxide catalyst

The effect of composition of reaction mixture on the gas-phase oxidation of isobutyraldehyde has been studied over a Mo–V oxide catalyst supported on Aerosil. It was found that oxygen, in contrast to water vapor, markedly changes the conversion of isobutyraldehyde and yields of acetone and methacrolein.     

High-throughput parallel reactor system for propylene oxidation catalyst investigation

A high-throughput reactor system was designed for catalyst testing, which includes two important sections: the gas flow splitters and the parallel reactor. Each gas flow splitter could split one gas stream to 64 streams (8 x 8). The current system has two gas splitters that could feed two kinds of gases (from mass flow controllers) to a 64-channel (8 x 8) parallel fixed-bed reactor. The reactor is composed of tube connectors, a reactor tube array, a heating block, a product collector, and a temperature controller. The reactor system could test 64 catalysts simultaneously and give results, which are comparable with a regular single-channel microreactor. For the purpose of verifying the validity of the reactor system, propylene oxidation to prepare acrolein was used as the probing reaction. In order to analyze the reaction products, a high-throughput colorimetric diffusion-reflection imaging method was developed for the analysis of acrolein. By comparing the results from colorimetric diffusion-reflection imaging analysis with that from the traditional gas chromatography spectrometer with thermal conductivity detectors, a colorimetric diffusion-reflection imaging method was confirmed to be reliable and accurate in acrolein analysis.     

Influence of ammonia on propane oxidation over a gallium-antimony oxide catalyst

The influence of ammonia on propane oxidation over a Ga–Sb oxide catalyst has been studied. Acrylonitrile is formed upon the interaction of acrolein with partially dehydrogenated ammonia. Ammonia increases the rates of overall and selective oxidation of propane. This is assumed to be due to the formation of electron-donor sites promoting proton separation from the propane molecule.

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. , . . , , .

     

Effect of alumina in multicomponent bismuth phosphate catalyst supported on silica-alumina for propylene ammoxidation reaction

The effect of compositions of silica-alumina support on multicomponent bismuth phosphate catalyst (MBP) was investigated for the propylene ammoxidation. It is appears that small amounts of Al₂O₃ cause retardation of the ammoxidation reaction, which would be due to activation of the selective oxidation pathway. It is understood from such results that the catalytic action of the MBP is essentially different with that of the multicomponent bismuth molybdate catalyst (MBM), which is generally used as propylene ammoxidation catalyst. This revised version was published online in June 2006 with corrections to the Cover Date.     

Direct gas-phase epoxidation of propylene to propylene oxide using air as oxidant on supported gold catalyst

Gold catalysts supported on SiO2, TiO2, TiO2-SiO2, and ZrO2-SiO2 supports were prepared by impregnating each support with a basic solution of tetrachloroauric acid. X-ray diffraction （XRD）, transmission electron microscopy （TEM）, and X-ray photoelectron spectroscopy （XPS） techniques were used to characterize their structure and surface composition. The results indicated that the size of gold particles could be controlled to below 10 nm by this method of preparation. Washing gold catalysts with water could markedly enhance the dispersion of metallic gold particles on the surface, but it could not completely remove the chloride ions left on the surface. The catalytic performance of direct vapor-phase epoxidation of propylene using air as an oxidant over these catalysts was evaluated at atmospheric pressure. The selectivity to propylene oxide （PO） was found to vary with reaction time on the stream. At the reaction conditions of atmosphere pressure, temperature 325 ℃, feed gas ratio V（C3H6）/V（O2）= 1/2, and GHSV =6000h^-1, 17.9% PO selectivity with 0.9% propylene conversion were obtained at initial 10 min for Au/SiO2 catalyst. After reacting 60 min only 8.9% PO selectivity were detected, but the propylene conversion rises to 1.4% and the main product is transferred to acrolein （72% selectivity）. Washing Au/TiO2-SiO2 and Aa/ZrO2-SiO2 samples with magnesium citrate solution could markedly enhance the activity and PO selectivity because smaller gold particles were obtained.     

Changes in the phase composition of a multicomponent Co-Mo-Bi-Fe-Sb-K-O catalyst under conditions of the partial oxidation of isobutylene to methacrolein: A comparison with the oxidation of propylene to acrolein

The partial oxidation of isobutylene to methacrolein on a multicomponent multiphase Co-Mo-Bi-Fe-Sb-K-O catalyst and on catalysts from which some components were absent was studied. Activity and selectivity changes in the case of isobutylene oxidation were the same as in the oxidation of propylene; however, the rate of propylene oxidation was higher than that of isobutylene oxidation. The X-ray diffraction analysis of the catalysts before and after the reaction indicated the occurrence of a number of phases in the samples: α-CoMoO₄, β-CoMoO₄, Fe₂(MoO₄)₃, reduced bismuth molybdate species, MoO₃, and reduced MoO _x species. Under catalytic reaction conditions, redox phase transformations occurred. Iron molybdate and molybdenum oxide phases underwent the largest transformations. Of two molybdenum oxide phases, a β-Mo₄O₁₁ phase with a structure of a crystallographic shift is formed in the course of catalysis, whereas the second phase (MoO₃) almost does not participate in catalysis and occurs in an excess.     

反应气中水对钼基甲烷化催化剂性能的影响

在反应温度550 ℃、空速5 500 h^-1、H₂S体积分数1.2%下对所研制的钼基催化剂进行了耐硫甲烷化活性评价,考察了反应气中添加H₂O对Mo基催化剂耐硫甲烷化活性的影响。结果表明,反应气中添加水对Al₂O₃负载的Mo基催化剂可造成不可逆失活,而添加Co助剂及采用铈铝复合载体的催化剂其稳定性、活性得到了改善和提高。Co的添加能保护Mo基催化剂上的活性组分MoS₂,抑制添加水导致的不可逆失活。当反应气中加入水时,催化剂上主要发生水汽变换反应,且随着水含量升高,水汽变换反应速率增大,会严重影响甲烷化反应的进行。此外,随着水含量的增加,其对催化剂的耐硫甲烷化活性和稳定性的影响程度变大。     

On the mechanism of propylene oxidation over gallium-molybdenum oxide catalysts

The products of selective oxidation are shown to be formed via a stepwise mechanism with participation of surface allylic complexes. A successive transformation of -allyl to -allyl and further to acrolein is possible. The products of complete oxidation may be formed through surface carbonate-carboxylate complexes via either a stepwise mechanism involving the catalyst's oxygen, or a concerted mechanism with the participation of molecular oxygen.

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, . - -, . - , .

     

Double metal cyano catalyst for ring opening polymerization of propylene oxide

A double metal cyano (DMC) catalyst is very effective for ring opening polymerization of propylene oxide (PO). The characteristics of the DMC complex were studied by Fourier transform infrared spectroscopy (FTIR) and thermogravimetry (TG). DMC complex generally result in a significant reduction of monols in the polyol production process. DMC catalyst is characterized by an approximately 1000 times higher activity compared to the conventional KOH catalyst. Disadvantages of the conventional KOH process are long reaction times, costly work-up procedures to remove the base catalyst and the formation of undesired unsaturated by-products (so called “monols”) especially in the preparation of long chain polyether polyols.     

A highly active, isospecific cobalt catalyst for propylene oxide polymerization

A highly active cobalt complex ((salph)CoOAc; salph = N,N'-bis(3,5-di-tert-butylsalicylidine-1,2-benzenediamine)) was discovered for the isospecific polymerization of rac-propylene oxide.     

稀土三元催化剂作用下正辛酸缩水甘油酯-二氧化碳-环氧丙烷的三元共聚合研究

本工作研究了稀土三元催化剂(三氯乙酸稀土配合物/二乙基锌/甘油)催化下的正辛酸缩水甘油酯、二氧化碳和环氧丙烷三元共聚合。红外光谱、核磁共振和差示扫描结果表明所获得的聚合物是一种新型的三元共聚物。随着反应单体中正辛酸缩水甘油酯比例的增加,所得聚合物在20℃下的断裂伸长率由二氧化碳－环氧丙烷共聚物的31.0%增大到二氧化碳－正辛酸缩水甘油酯共聚物的983.9%,相应的玻璃化转变温度由39.6℃降低至-12.3℃。所得三元共聚物中长碳链侧基单元含量为5.6%时,其断裂伸长率就已经达到481.1％,而拉伸强度仍然维持在24.9MPa的较高水平。     

Copolymerization of carbon dioxide and propylene oxide under inorganic oxide supported rare earth ternary catalyst

Recently, rare earth ternary coordination catalyst represented as Y(CCl₃OO)₃‐Glycerin‐ZnEt₂ has been used for producing poly(propylene carbonate) (PPC, an alternating copolymer of carbon dioxide and propylene oxide) in industry scale, but its catalytic activity needs further improvement. One reason for the relatively low catalytic activity lied in that only 11.7% of active center was efficient due to possible embedding of active center in the heterogeneous catalyst. In this report, supporting strategy was developed, where Y(CCl₃OO)₃‐Glycerin‐ZnEt₂ was supported on various inorganic oxides. Two supporting methods were carried out. One way was to mix Y(CCl₃OO)₃‐Glycerin with inorganic oxide first and then ZnEt₂ was dropped to form the supported catalyst, and the other was to make Y(CCl₃OO)₃‐Glycerin‐ZnEt₂ at first and then mixing with inorganic oxides. The former showed decreasing catalytic activity compared with corresponding unsupported rare earth ternary catalyst, while an improvement of 16–36% in catalytic activity was realized in the latter. PPC with an average number molecular weight (M_n) of over 100 kg/mol and carbonate unit (CU) content of higher than 96% was prepared by both supported catalysts. The catalytic activity of the supported catalyst depended significantly on the supports, which increased in the following order: α‐Al₂O₃ < MgO < ZnO ≈ SiO₂ <γ‐Al₂O₃. γ‐Al₂O₃ was the best support for rare earth ternary catalyst, which showed a remarkable 36% increase in catalytic activity, corresponding to the utilization of 17% of active center. Although MgO supported catalyst gave only an 8% increase in catalytic activity, the M_n and CU content of PPC were raised to about 143 kg/mol and 99%, whereas the PPC from common rare earth ternary catalyst was about 108 kg/mol and 97%, respectively. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011