共查询到20条相似文献,搜索用时 15 毫秒
1.
ShuFengZHANG QingLiQIAN PingLaiPAN YiCHEN GuoQingYUAN 《中国化学快报》2005,16(1):100-102
ANd promoted-Rh catalysts supported on polymer-derived carbon beads for vapor-phas emethanol carbonylation was developed. Rh-Nd bimetallic catalysts obviously have higher activity than that of supported Rh catalyst under similar reaction condition. The difference between the activity of above two catalyst systems is clearly caused by the intrinsic properties generated by the introduction of Nd. 相似文献
2.
钼催化剂上甲醇直接气相羰基化活性与吸附的关系 总被引:1,自引:0,他引:1
制备了一系列非负载的钼催化剂,考察了催化剂上甲醇直接气相\r\n羰化活性与反应物及产物吸附的关系.结果发现,催化剂的制备方法对\r\n甲醇直接气相羰化活性的影响很明显,以纯二硫化钼试剂制备的催化剂\r\n,甲醇转化率与羰化产物乙酸甲酯的选择性最低;以三氧化钼气相还原\r\n硫化制备的催化剂,其羰化活性较低;以钼酸铵溶液经硫化铵溶液或硫\r\n化氢气体硫化制得的催化剂,其性能明显优于前两种,尤以钼酸铵经硫\r\n化铵溶液硫化制得的催化剂的性能最佳.催化剂的羰化活性明显依赖于\r\n催化剂的吸附性能,羰化活性高的催化剂不仅吸附CO的量大,而且对甲\r\n醇和乙酸甲酯的吸附量也明显较大. 相似文献
3.
4.
乙醇直接气相羰基化新催化剂 总被引:1,自引:0,他引:1
醇的羰基化合成是极有工业价值的过程 ,也是绿色化学中提倡的原子经济性反应 [1] .甲醇均相羰基化合成醋酸是 Monsanto公司成功开发应用的典范 [2 ] ,而乙醇羰基化合成丙酸或丙酸乙酯的研究尤其重要 .前文对一种性能优良的负载型 Ni系催化剂用于乙醇常压气相羰基化合成丙酸及其酯作了报道 [3,4] ,与均相羰基化相比 ,该反应具有条件温和 ,不使用贵金属铑 ,催化剂与产物不存在分离上的困难等优点 ,但反应体系仍需使用卤化物作促进剂 .由于碘乙烷的存在 ,反应系统设备腐蚀严重 (有 HI生成 ) ,产物分离精制复杂 .目前 ,醇的均相羰基化及多相羰… 相似文献
5.
The alkylation of methanol by triethylamine to form ethyl methyl ether was studied in the temperature range 310-330°C using γ-alumina and silica-aluminas differing in their silica content. The effect of treating γ-alumina with hydrochloric and boric acid on the reaction rate was also investigated. The results obtained for ether formation over γ-alumina show that the reaction is first order for methanol and zero orde for triethylamine. Alumina-H3BO3 was found to be the most active catalyst whereas alumina-HCl is the least active towards ether formation. The activity of silica-alumina is proportional to its silica contents. 相似文献
6.
Golubina E. V. Lokteva E. S. Lazareva T. S. Kostyuk B. G. Lunin V. V. Simagina V. I. Stoyanova I. V. 《Kinetics and Catalysis》2004,45(2):183-188
The hydrodechlorination of CCl4 in the presence of Pd–Fe/Sibunit catalysts of different composition was studied. An optimum concentration of the metals (2.5% at the ratio Pd/Fe = 1 : 4) was determined, which corresponds to the highest stability of catalysts and selectivity of C2–C4 olefin and paraffin formation. With the use of TPR and magnetic measurements, it was found that the metals occurred in an oxidized state in the course of the reaction; it is likely that this resulted in the formation of C2–C4 hydrocarbons. 相似文献
7.
乙醇在新型Mo/C催化剂上的气相羰基化反应 总被引:1,自引:0,他引:1
The carbonylation of alcohol to acid or ester is an important process in the chemical industry. The Monsanto process for acetic acid via the homoge neous carbonylation of methanol is an example of the largest scale commercial application of this route[1].Recently, ethanol carbonylation for manufacturing propionic acid and ethyl propionate became an at tractive approach, and many research efforts were made for an appropriate catalyst to carry out the va por phase carbonylation under atmospheric pres sure[2~4]. Although an iodide-promoted Ni/C cata lyst is found to exhibit satisfactory activity and se lectivity for the vapor phase carbonylation of ethanol, it is affected by the disadvantages associat ed with a highly corrosive reaction medium and dif ficult product separation owing to the use of ethyl iodide as promoter. There has been little success in finding heterogeneous or homogeneous catalyst that can operate effectively without a halide promoter[5]. 相似文献
8.
PENG Feng 《高等学校化学研究》2000,16(2):188-190
IntroductionThe carbonylation of alcohols via homogenous catalysis is important in manufacturingacetic acid and higher carboxylic acids and their esters[1 ,2 ] . The main route to produce aceticacid is to make methanol carbonylated by means of the Monsanto and BP process in which ahomogeneous rhodium catalystis used.Although the homogeneous carbonylation ofmethanolis a highly selective process,itisaffected by the disadvantagesassociated with a highly corro-sive reaction medium due to the use … 相似文献
9.
10.
Steam-reforming reactions of methanol over NiO/Al2O3 and CuO/ZnO have been investigated. Over the nickel catalyst, the reaction rate is of zero kinetic order with respect to either methanol or steam, and the activation energy is 12.4 kJmol?1, whereas with copper catalyst, the rate is expressed according to the literature as kPa/(1 + KaPa + Kb+Pb) in which “a” and “b” are methanol and steam, respectively. The rate-controlling step of the reaction is assigned to the dissociation of O-H bond with dehydrogenation of C-H bond proceed rapidly to form carbon oxides. With copper catalyst the intrinsic participation of a water molecule during the dehydrogenation of C-H bond leads to the formation of carbon dioxide. With nickel catalyst, the dehydrogenation proceed more rapidly than the migration of a water molecule from an alumina site to a nickel site and causes almost exclusively the formation of carbon monoxide and hydrogen at a lower reaction temperature. 相似文献
11.
The partial pressure of sodium nitrite in the system NaNO2-KNO3 was measured at 798, 823, and 848 K. The dependence of the logarithm of the NaNO2 pressure on inverse temperature is presented. Coefficients A and B of the Clausius-Clapeyron equation and the partial molar heats of vaporization are calculated. The activity and activity coefficient of sodium nitrite are determined. The dependences of ac- tivity and activity coefficient of sodium nitrite and potassium nitrate are presented as functions of composition of the NaNO2-KNO3 system. The consistency of the activity coefficients is verified using the Redlich-Kister integral. 相似文献
12.
由于催化活性与立体选择性高,Pd催化剂广泛应用于Heck型交叉偶联反应,其催化机理通常依次包括Pd(0)氧化加成、加成、β-H消除、还原性消除等四步。对于无机非金属、有机高分子及有机-无机复合材料负载型Pd催化剂,Pd浓度的升高增大了催化表面积,Pd-载体吸附作用的加强、载体尺寸的减小及表面结构性的增加提高了Pd的分散度; Pd不饱和配位活性位的增多促进了其与反应物形成配位中间体,溶剂对载体溶胀度的增高扩大了Pd与反应物的有效接触面积,而碱的碱性与用量的增加加速了Pd在催化循环中的再生,这些均提高了Pd的催化活性。然而,随着反应温度的升高,Pd的催化活性一般先升高,至某一适中温度时达到最高值,之后因Pd的热聚集过于显著转而降低。研发催化机理明确、催化活性高、立体选择性强、可重复使用性好的负载型Pd催化剂为Heck反应研究的发展趋势之一。 相似文献
13.
钯催化气相氧化羰基化合成碳酸二甲酯 总被引:5,自引:0,他引:5
通过催化剂反应性能和反应前后XPS谱图对比,分析了负载型钯催化剂在甲醇气相氧化羰基化合成碳酸二甲酯过程中的失活原因,研究了HCl在维持催化剂活性及失活催化剂再生中的作用.结果表明,氯离子的流失是负载型钯碳催化剂失活的主要原因.由于氯离子的流失,对于PdCl2/AC催化剂,钯很容易从二价变为零价:对于PdCl2-CuCl2/AC催化剂,CuCl2发生变化,失去使钯保持二价氯化物状态的功能.在反应过程中补充HCl可以延长催化剂的寿命,也可以利用HCl对失活催化剂进行再生,但采用HCl不能从根本上解决催化剂失活的问题. 相似文献
14.
Nobuhiro Iwasa Masao Terashita Masahiko Arai Nobutsune Takezawa 《Reaction Kinetics and Catalysis Letters》2001,74(1):93-98
The catalytic performance of supported Pd and Pt catalysts for the title reaction was greatly improved upon the formation
of Pd and Pt alloys. Over Pd and Pt alloys, methyl formate was selectively hydrogenolyzed to methanol, while over metallic
Pd and Pt, it was decarbonylated to methanol and carbon monoxide.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
15.
The Diels-Alder reaction of cyclopentadiene with methyl acrylate catalyzed by AlCl3 has been theoretically investigated. M06-2X level DFT calculations have shown that the formation of two C−C bonds is asynchronous in the cycloaddition both in the endo path and in the exo path, thus making a good contrast to the well-known concept of [4+2] reactions based on the orbital symmetry arguments. It was found that the catalyst facilitates the cycloaddition and brings a higher endo selectivity in the highly asynchronous process, as compared with the reaction of the diene and the dienophile without the catalyst. 相似文献
16.
17.
18.
《Analytical letters》2012,45(4):217-222
Abstract The standard technique of vapor phase osmometry has been modified to permit easier measurements on compounds with high vapor pressures (up to at least 5 torr). Wicks are used to create a continuous flow of Liquids onto the thermistors, thereby creating a steady-state concentration in the solvent-saturated atmosphere. Measurements with both aqueous and nonaqueous solvents are possible. In addition, the steady-state method applied to nonvolatile solutes was easier, faster, and more reproducible than the drop method. 相似文献
19.
Belyaev A. V. Emel'yanov V. A. Khranenko S. P. Fedotov M. A. 《Russian Journal of Coordination Chemistry》2001,27(3):184-194
Reactions of nitrite complexes of Pd, Ru, and Rh with sulfamic acid were studied by the 14, 15N, and 17O NMR method. Chemical shifts were assigned, and the predominant forms of the complexes were established. The reaction products at room temperature are cis-nitroaqua complexes. Coordination of the sulfamate ion upon storage for a long time or on heating was detected. 相似文献
20.
Chariklia Sotiriou-Leventis Xiaojiang Wang Sudhir Mulik Arumugam Thangavel Nicholas Leventis 《合成通讯》2013,43(14):2285-2298
Immobilization of catalysts on solid supports is a promising approach to combine the advantages of heterogeneous and homogeneous catalysts. Pd(PPh3)2Cl2, known as an extremely active homogeneous catalyst for the Sonogashira coupling reaction, has been immobilized on high-surface-area MCF (mesocellular foams)–type mesoporous silica powder modified with 3-aminopropyltriethoxysilane and subsequently with diphenylphosphine. The functionalized MCF-type silica and supported catalysts have been characterized by x-ray photoelectron spectroscopy (XPS), fourier transform infrared spectroscopy (FTIR), elemental analysis, nitrogen sorption porosimetry, and scanning electron microscopy (SEM). Such supported Pd catalysts have proven to be useful recyclable reagents for copper- and amine-free Sonogashira coupling reactions of haloaromatic compounds with terminal alkynes. 相似文献