共查询到20条相似文献,搜索用时 15 毫秒
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The direct oxidation of propylene to propylene oxide (PO) using molecular oxygen has many advantages over existing chlorohydrin and hydroperoxide process, which produce side products and require complex purification schemes. Recent advances in liquid-phase and gas-phase catalytic oxidation of propylene in the presence of only molecular oxygen as oxidant and in absence of reducing agents are summarized. Liquid-phase PO processes involving soluble or insoluble Mo, W, or V catalysts have been reported which provide moderate conversions and selectivities, but these likely involve autoxidation by homogeneous chain reactions. Gas-phase PO catalysts have been mostly Ag-, Cu-, or TiO2-based substances, although other compositions such as Au-, MoO3-, Bi-based catalysts and photocatalysts have also been suggested as possibilities. The Ag catalysts differ from those used for ethylene oxide production in having high Ag contents and numerous additives. The additives are solid-phase alkali metals, alkaline earth metals, and halogens, with the most common substances being NaCl and CaCO3. Nitrogen oxides in the form of gas-phase species or nitrates have also been found to be effective in enhancing PO production. Direct epoxidation by surface nitrates is a possibility. Titania catalysts supported on silicates have also been reported. These have higher PO selectivities at high conversion than silver catalysts. 相似文献
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Yu-Hang Yuan Xing-Gui Zhou Wei Wu Yi-Ran Zhang Wei-Kang Yuan Lingai Luo 《Catalysis Today》2005,105(3-4):544-2
Gas phase propylene epoxidation on gold catalysts has attracted wide attention from industry and academia due to its high selectivity. However, it suffers from low propylene conversion and rapid catalyst deactivation. Experiments showed that propylene conversion could be increased by raising H2, O2, or C3H6 concentration in the feed, but the feed compositions were within the explosion limit. It was also shown that the activity of the used catalyst could be fully recovered, but the regeneration temperature was 280 °C, much higher than that for reaction. Therefore a microchannel reactor was devised to suppress explosion and was constructed with Fecralloy, to raise the temperature rapidly for catalyst regeneration by electric heating. In two minutes the temperature of the reactor could be raised from 50 to 300 °C. Catalysts were coated on the alloy belt by dip coating, and the performance of the reactor was evaluated under different operating conditions. Results showed that in the microreactor the overall reaction rate was controlled mainly by the intrinsic reaction rate, and also influenced by film diffusion to a certain extent. The deactivated catalyst was regenerated in the microchannel reactor and the activity was fully recovered. 相似文献
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Chemical Fixation of Carbon Dioxide to Propylene Carbonate Using Smectite Catalysts with High Activity and Selectivity 总被引:1,自引:0,他引:1
Shin-ichiro Fujita Bhalchandra M. Bhanage Yutaka Ikushima Masayuki Shirai Kazuo Torii Masahiko Arai 《Catalysis Letters》2002,79(1-4):95-98
The reaction of propylene oxide and carbon dioxide to propylene carbonate was carried out using Mg-, Ni- and Mg-Ni-containing smectite catalysts which contain different amounts of alkali atoms such as sodium, potassium and lithium. These catalysts are highly active and selective for this reaction. The catalytic activity strongly depends on the elemental composition of the catalyst used. Particularly the amount of alkali atoms incorporated in the catalyst is the most important factor governing the catalytic performance. The most active catalyst among those prepared in the present study shows a turnover number of 105 mmol/g for the propylene carbonate formation, which is the highest turnover number compared with those reported so far (10 mmol/g) for the title reaction. 相似文献
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环氧丙烷与二氧化碳合成碳酸丙烯酯 总被引:1,自引:0,他引:1
介绍了PC的性质、应用情况和生产工艺。通过对影响合成PC的主要因素和机理的讨论,指出催化剂和溶剂是影响PC收率的重要因素,较高的压力对提高产品的选择性有利。 相似文献
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A synthesis of diethyl carbonate through transesterification of propylene carbonate and ethanol, coproducing useful propylene glycol, was carried out in the presence of sodium ethoxide as catalyst. The effects of reaction parameters such as catalyst concentration, mole ratio of ethanol to propylene carbonate and reaction temperature on the transesterfication reaction were investigated. The results showed that the reaction is reversible with a propylene carbonate equilibrium conversion of about 64 % at an ethanol to propylene carbonate mole ratio of 8.0 and a reaction temperature of 303 K. A kinetic model was proposed based on the reaction mechanism. The model parameters were estimated by the Runge‐Kutta method. The statistical test showed that the model calculation results were in good agreement with the experimental data. 相似文献
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氯丙醇减压皂化生产环氧丙烷*刘家祺孙广智刘禾(天津大学化工系,天津300072)(天津化工设计院,天津300193)氯丙醇减压皂化生产环氧丙烷*刘家祺孙广智刘禾(天津大学化工系,天津300072)(天津化工设计院,天津300193)关键词氯丙醇环氧丙... 相似文献
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Propylene aromatization reaction was performed on various MFI type zeolites containing Ga species. The Ga was introduced into
the zeolites by substitution (Ga-MFI), ion exchange (GIZ) and physical mixing (GPZ). A com-mercialized zeolite (PQZSM-5) was
also used for comparison. The catalysts prepared were characterized by using XRF, XPS, surface area measurement, NH3-TPD, and H2-TPR. Through the Ga substitution, the acidity of the modified catalysts was decreased, and dehydrogenation and aromatization
reactions occurred more easily. The lattice Ga did not react well with hydrogen contrary to the Ga located at the outside
of the lattice. It was also found that Ga-MFI catalysts facilitate alkylation reactions.
This paper is dedicated to Professor Wha Young Lee on the occasion of his retirement from Seoul National University 相似文献
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V. A. Sadykov S. N. Pavlova N. F. Saputina I. A. Zolotarskii N. A. Pakhomov E. M. Moroz V. A. Kuzmin A. V. Kalinkin 《Catalysis Today》2000,61(1-4):93-99
A specially designed tubular microreactor with independent control of feed preheat as well as catalyst temperature and allowing to rapidly quench reaction products was used to test performance of supported Pt-based monolithic catalysts in the reaction of propane oxidative dehydrogenation at short contact times. To minimize the impact of undesired homogeneous reactions capable of decreasing propylene selectivity, proprietary straight-channel thin-wall high cell density corundum micromonoliths were chosen as supports. Catalytic properties of supported platinum were modified by using promoters known as dehydrogenation catalysts (tin, zinc aluminate spinel, transition metal pyrophosphates) as well as by tuning reaction mixture composition (propane/oxygen ratio, water and hydrogen content). In the operation temperature range up to 900°C with contact times 0.03–0.1 s, ethylene/propylene selectivities were found to strongly depend upon the chemical composition of the active component and type of feed. The results thus obtained demonstrate that for Pt-based catalysts, propylene yield can be substantially improved by suppressing secondary reactions of deep oxidation and cracking. 相似文献
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介绍了催化脱氢、氧化脱氢、膜反应器脱氢等几种丙烷脱氢制丙烯技术,综述了丙烷催化脱氢制丙烯催化剂的研究现状,虽然丙烷催化脱氢生产丙烯已实现了工业化,但其催化剂的性能需进一步提高;对丙烷氧化脱氢制丙烯反应催化剂的研究现状及膜反应器在丙烷脱氢反应上所具有的优越性进行了描述,认为研发具有高稳定性和高透氢性能的氢分离膜,将有望能大幅度提高丙烯的收率。 相似文献
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负载型碳酸钾催化剂上二氧化碳与1,2-丙二醇合成碳酸丙烯酯反应研究 总被引:1,自引:0,他引:1
在负载型碳酸钾催化剂上对二氧化碳与1,2-丙二醇(PG)合成碳酸丙烯酯(PC)反应进行了研究.结果表明,负载型碳酸钾催化剂的最佳制备条件为:活性炭为载体,碳酸钾负载量为15%(wt),焙烧温度423.15 K.在反应温度443.15 K、催化剂用量为2.0%(wt)、溶剂(乙腈)/PG/二氧化碳(摩尔比)为19.2:3:4、二氧化碳初始压力为2.0 MPa、反应时间12 h的条件下,PG的转化率为12.9%,PC的收率为9.6%,选择性为74.4%.对活性炭负载碳酸钾催化剂进行了XRD分析,发现存在K2CO3和K2O两种晶相.BET分析结果表明,载体的比表面积对负载型碳酸钾催化剂的催化活性有较大影响.与均相碳酸钾催化剂相比,负载型碳酸钾催化剂上PC的选择性提高了40.3%. 相似文献
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Silver modified HZSM-5 (AgHZ) zeolite catalysts were prepared by ion exchange method and their catalytic properties in the 1-butene cracking reaction were measured. The catalysts were characterized by infrared spec-troscopy with pyridine adsorption (Py-IR), N2 adsorption and X-ray diffraction (XRD). The effects of Ag loading and steaming treatment on catalytic performances were studied. It is found that the activity of HZSM-5 (HZ) cat-alyst significantly decreases with the steaming time, whereas AgHZ catalysts show stable activity in the steaming time of 24–48 h and their activities increase with the Ag loading. When the steaming time is 24–48 h, the yield of propylene over HZ catalyst significantly decreases, whereas it is stable over AgHZ catalysts. The AgHZ catalysts with Ag loadings of 0.28%–0.43%(by mass) show similar propylene yields (~30%), which are higher than that over the AgHZ catalyst with a Ag loading of 0.55%(by mass). These results indicate that the steam-treated AgHZ catalysts with optimum Ag loadings have higher yield of propylene and are more stable than the steam-treated HZ catalyst. The regeneration stability measurement in butene cracking also shows that the AgHZ catalyst steam-treated under a suitable condition has better stability than the HZ catalyst. 相似文献
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Fong-Chang Sheu Cheng-Tsung Hong Wen-Long Hwang Cheng-Jec Shih Jung-Chung Wu Chuin-Tih Yeh 《Catalysis Letters》1992,14(3-4):297-304
A series of alumina aluminum borate (AAB) with various Al/B molar ratios were prepared by the coprecipitation method. The supported rhenium oxide catalysts with various contents of Re2O7 were also prepared by the impregnation method with perrhenic acid. The catalytic activity and stability of Re2O7/AAB catalysts for the reaction of propylene metathesis were tested in a fixed-bed microreactor. It was found that Re2O7/AAB is more active, stable and regenerable than Re2O7/Al2O3 for propylene metathesis. The optimum Al/B molar ratio was found to be in the range of 4–10. 相似文献