CO hydrogenation to light alkenes over Mn/Fe catalysts prepared by coprecipitation and sol-gel methods

CO hydrogenation to light alkenes was carried out on manganese promoted iron catalysts prepared by coprecipitation and sol-gel techniques. Addition of manganese in the range of 1-4 mol.% by means of coprecipitation could improve notably the percentage of C-2 (=) similar to C-4 (=) in the products, but it was not so efficient when the sol-gel method was employed. XRD and H-2-TPR measurements showed that the catalyst samples giving high C-2 (=) similar to C-4 (=) yields possessed ultra. ne particles in the form of pure alpha-(Fe1-xMnx)(2)O-3, and high quality in lowering the reduction temperature of the iron oxide. Furthermore, these samples displayed deep extent of carburization and different surface procedures to the others in the tests of Temperature Programmed Surface Carburization (TPSC). The different surface procedures of these samples were considered to have close relationship with the evolving of surface oxygen. It was also suggested that for the catalysts with high C-2 (=) similar to C-4 (=) yields, the turnover rate of the active site could be kept at a relatively high level due to the improved reducing and carburizing capabilities. Consequently, there would be a large number of sites for CO adsorption/dissociation and an enhanced carburization environment on the catalyst surface, so that the process of hydrogenation could be suppressed relatively to a low level. As a result, the percentage of the light alkenes in the products could be raised.

Gasoline-range hydrocarbon synthesis over cobalt-based Fischer-Tropsch catalysts supported onSiO2/HZSM-5

Two types of SiO2 with different mesopore size and HZSM-5 zeolite were used to prepare hybrid supported cobalt-based catalysts. The textual and structural properties of the catalysts were studied using N-2 physisorption, X-ray diffraction (XRD), and H-2 temperature-programmed reduction (TPR) techniques. Fischer-Tropsch synthesis (FTS) performances of the catalysts were carried out in a fixed-bed reactor. The combination effects of the meso- and micropores of the supports as well as the interaction between supports and cobalt particles on FTS activity are discussed. The results indicate that the catalyst supported on the tailor-made SiO2 and HZSM-5 hybrid maintained both meso- and micropore pores during the preparation process without HZSM-5 particles agglomerating. The mesopores provided quick mass transfer channels, while the micropores contributed to high metal dispersion and accelerated hydrocracking/hydroisomerization reaction rate. High CO conversion of 83.9% and selectivity to gasoline-range hydrocarbons (C-5-C-12) of 55%, including more than 10% isoparaffins, were achieved simultaneously on this type of catalyst.

Upgrading of liquid fuel from the vacuum pyrolysis of biomass over the Mo-Ni/gamma-Al2O3 catalysts

High amounts of acid compounds in bio-oil not only lead to the deleterious properties such as corrosiveness and high acidity, but also set up many obstacles to its wide applications. By hydrotreating the bio-oil under mild conditions, some carboxylic acid compounds could be converted to alcohols which would esterify with the unconverted acids in the bio-oil to produce esters. The properties of the bio-oil could be improved by this method. In the paper, the raw bio-oil was produced by vacuum pyrolysis of pine sawdust. The optimal production conditions were investigated. A series of nickel-based catalysts were prepared. Their catalytic activities were evaluated by upgrading of model compound (glacial acetic acid). Results showed that the reduced Mo-10Ni/gamma-Al2O3 catalyst had the highest activity with the acetic acid conversion of 33.2%. Upgrading of the raw bio-oil was investigated over reduced Mo-10Ni/gamma-Al2O3 catalyst. After the upgrading process, the pH value of the bio-oil increased from 2.16 to 2.84. The water content increased from 46.2 wt.% to 58.99 wt.%. The H element content in the bio-oil increased from 6.61 wt.% to 6.93 wt.%. The dynamic viscosity decreased a little. The results of GC-MS spectrometry analysis showed that the ester compounds in the upgraded bio-oil increased by 3 times. it is possible to improve the properties of bio-oil by hydrotreating and esterifying carboxyl group compounds in the bio-oil.

Ce-基催化剂上CH_4低温催化燃烧的研究

Ce-基催化剂在汽车尾气净化，工业废气处理，烃类重整，烃类选择加氢等方面均有广泛的应用。近几十年来关于如何制备高活性、高稳定性的非贵金属复合氧化物催化剂一直是催化研究的重要课题之一。Ce-基催化剂主要都是通过其它金属氧化物M掺杂到CeO_2中形成Ce_(1-x)M_xO（M为掺杂物）固溶体。本文选用CeO_2作为主要研究对象，用柠檬酸法有目的的引入化学特性、离子半径不同的另一组分，用x值表示各元素间的化学计量比，优化催化剂的组成、结构，来调节所合成固溶体氧化物的物理化学性质。分别以碱土金属Ca、稀土金属La以及过渡金属Ni和Mn为掺杂物制备出含其它不同离子的Ce-基催化剂；将具有较高活性的Ni_(0.7)Ce_(0.3)O负载在ZrO_2上，以CH_4燃烧为模型反应，考察催化剂活性和氧化还原性的关系。1．Ce-Ca-La-O体系单独Ca或La分别加入到CeO_2中后催化剂的活性比单独的CeO_2的活性要高出很多，完全转化温度要下降近100℃，而且它们的H_2-TPR实验也证实了其氧化还原能力有很大的提高。将Ca和La同时引入到CeO_2的复合氧化物Ce-La-Ca-O材料，其活性比无La的Ce-Ca-O的活性没有明显的提高，而且反而要比Ce-La-O的活性低，且其HZ一TPR实验也显示出和复合氧化物Ce-Ca-O的轮廓一样。2．Ce-Ni-Mn-O体系对NiO、MnO_x、CeO_2三种金属氧化物，在优化两种金属氧化物最佳配比（组成）后，在复合氧化物中掺杂第三种金属氧化物以考察第三种金属对其甲烷燃烧活性的影响。（l）CeO_2-MnO_x体系中，在Ce_(0.8)Mn_(0.2)O掺杂NiO后，发现当Ni的摩尔量为-10％时，活性提高幅度的很大，完全燃烧的温度下降了近50℃，可在550℃将CH_4完全氧化到CO_2。（2）CeO_2-NiO体系中，Ce_(0.3)Ni_(0.7)O可在530℃将CH_4完全氧化到CO_2。向其中掺杂Mn后，复合氧化物的活性反而下降，要在550oC才能将CH4完全氧化到C02。这可能是阴离子缺陷减少所致。（3）NIO一Mnox体系中，Nio，IMn090掺杂Ce后，催化活性有大幅度提高，特别是Nio．ICeyMno90（0．3三y生0．8）中催化剂的活性更高，可在530oC体系中，其中y＝0．5时更突出。3．Ni-Ce-O／ZrOZ体系（1）Ni1-x一Cex一O体系中，独立的CeOZ相促进了NIO的还原和表面积增加。（2）少量的CeOZ的掺杂明显改善了NIO对cH4完全氧化反应的活性。继续增加Ce的量催化活性弱有增加，然后下降。在Ce的掺杂量为30％时，即Nio7Ceo3O，催化活性最佳，此时甲烷完全转化的温度为530oC。（3）催化剂Ni07Ceo3O具有很好的稳定性，900oC下焙烧，还能在540oC将CH4完全氧化到COZ。（4）催化剂Pd／Ni07Ceo30的催化活性与Pd／A12O3的活性相当。（5）催化剂Ni07Ce03O负载在不同的载体上，发现ZrOZ作载体效果最佳，其次为5102，这可能是ZrOZ、5102对NIO、CeOZ相对惰性有关；而MgO、A1203虽表面积较大，但作为载体效果却不好，可能其易与NIO、CeOZ发生反应有关。（6）Nio7Ceo3O负载在ZrOZ上，提高了表面积同时促进了Nio7Ceo3O还原性，以负载量为50％时活性最好。结构分析发现有两个新相生成，Ni4Zro和CeZO3。（7）通过对比发现Nio7Ceo3O（50％）／ZrOZ体系高活性除了ZrOZ作为载体提高表面积外，Zr02和Ce在这里还起到助催化剂的作用。4．还探讨了Pr掺杂到CeO2，以及YSZ作为载体负载过渡金属氧化物在甲烷催化燃烧反应种的作用。

Fischer-Tropsch reaction over cobalt catalysts supported on zirconia-modified activated carbon

An attractive Fischer-Tropsch catalyst was prepared using an activated carbon as carrier to support cobalt based catalysts. Zr promoted Co/AC catalysts remarkably enhanced the activity and the selectivity toward diesel distillates and lower the methane selectivity. This modification may be attributed to specific behavior of activated carbon with high surface area and the weak interaction between metallic cobalt active sites and activated carbon. It was emphasized that the pore size of activated carbon played a very important role in restricting the growth of carbon chain to wax.

Reduction of NO by CH4 with microwave heating

The reduction of NO by CH4 in the presence of excess O-2 over Co/HZSM-5, Ni/HZSM-5 and Mn/HZSM-5 catalysts with microwave heating was studied. By comparing the activities of the catalysts in the microwave heating mode with that in the conventional reaction mode, it was demonstrated that microwave heating could greatly reduce the reaction temperature, and could clearly expand the temperature window of the catalysts. Especially for the Co/HZSM-5 catalyst, the maximum conversion of NO to N-2 in the conventional reaction mode was consistent with that in the microwave heating mode. However, the temperature window for the maximum conversion in the microwave heating mode was from 260 to 360degreesC instead of a temperature of 420degreesC in the conventional reaction mode. The results suggest that microwave heating has a novel effect in the reduction of NO.

Synthesis, molecular structures, and norbornene addition polymerization activity of the neutral nickel catalysts supported by beta-diketiminato [N, N], ketiminato [N, O], and Schiff-Base [N, O] ligands

A series of neutral nickel complexes [Ni(Ph)(PPh3)(N, O)] with Schiff-base ligands (N, O) [N, O = 5-Me-3-tert-Bu-(Ar-N=CH)C6H2O (1, Ar = 2,6-Me2C6H3; 2, Ar = 2,6-i-Pr2C6H3)], [Ni(Ph)(PPh3)(N,O)1, with beta-ketiminato ligands (N, O) [N, O = CH3COCHC=(CH3)N-Ar (3, Ar = 2,6-Me2C6H3; 4, Ar = 2,6-i-Pr2C6H3)] and [Ni(N, N)(PPh3)], and with beta-diketiminato ligands (N, N) [5, N, N = [2,6-i-Pr-2(C6H3)N=C(CH3)](2)CH] have been synthesized and characterized. The molecular structures of complexes 1, 4, and 5 have been confirmed by X-ray single-crystal analyses. Although their ligands have similar structures, complex 4 possesses a structure similar to that of four-coordination nickel with complex 1, while complex 5 reveals a rare three-coordination nickel geometry. These compounds show high catalytic activities of up to 3.16 x 10(7) g PNB mol(-1) Ni h(-1) for the addition polymerization of norbornene in the presence of modified methylaluminoxane (MMAO) as cocatalyst. Catalytic activities, polymer yield, molecular weights, and molecular weight distributions of polyborbornene have been investigated under various reaction conditions.

铁的添加方式对Cu-Mn/ZrO2合成低碳醇催化剂的影响

中国科学院山西煤炭化学研究所

The effect of chromium on sulfur resistance of Pd/HY-Al2O3 catalysts for aromatic hydrogenation

Sulfur is a major poison to noble metal catalysts for deep aromatic hydrogenation in the petroleum refining industry. In order to study the sulfur resistance of Pd-based catalysts, a series of Pd, Cr, and PdCr catalysts supported on HY-Al2O3 were studied by NH3-TPD, pyridine-adsorption IR, TPR, IR spectra of adsorbed CO, and toluene hydrogenation in the presence of 3000 ppm sulfur as thiophene under the following conditions: 533-573 K, 4.2 MPa, and WHSV 4.0 h(-1). Cr has no influence on the acidity of the catalysts. TPR patterns and in situ IR spectra of adsorbed CO revealed a strong interaction between Cr and Pd, and the frequency shift of linear bonded CO on Pd indicates that the electron density of Pd decreases with the increase of the Cr/Pd atomic ratio. The catalytic performance of Pd, Cr, and PdCr catalysts shows that the sulfur resistance of Pd is strongly enhanced by Cr, and the activity reaches its maximum when the Cr/Pd atomic ratio equals 8. The active phase model "Pd particles decorated by Cr2O3" is postulated to explain the behavior of PdCr catalysts. (C) 2001 Academic Press.

Heterogeneous enantioselective epoxidation catalyzed by Mn(salen) complexes grafted onto mesoporous materials by phenoxy group

Three chiral Mn(salen) complexes were immobilized into different mesoporous material via phenoxy group by a simplified method and they show high activity and enantioselectivity for asymmetric epoxidation of various substituted unfunctional olefins. The heterogeneous Mn(salen) catalysts show comparable ee values for asymmetric epoxidation of styrene and 6-cyano-2,2-dimethylchromene and much higher ee values for epoxidation of a-methylstyrene (heterogeneous 79.7% ee versus homogeneous 26.4% ee) and cis-beta-methylstyrene (heterogeneous 94.9% ee versus homogeneous 25.3% ee for cis-epoxide) than the homogeneous catalysts. These heterogeneous catalysts also remarkably alter the cis/trans ratio of epoxides for asymmetric epoxidation of cis-beta-methylstyrene (heterogeneous 21 versus homogeneous 0.38). The axial tether group does not make a big effect on ee values and the increase in ee value and change in cis/trans ratio are mainly attributed to the axial immobilization mode and the support effect of heterogeneous catalysts. The catalysts keep constant ee values for the recycle tests of eight times for asymmetric epoxidation of a-methylstyrene. And several possibilities were proposed to elucidate the difference in ee values of heterogeneous catalysts from homogeneous catalysts. (c) 2005 Elsevier B.V. All rights reserved.