Kinetics of the hydrogenation of co on an Fe/Al2O3 catalyst

A study was carried out on the effect of temperature and reaction mixture composition on the activity and selectivity of an Fe/Al₂O₃ CO hydrogenation catalyst relative to lower olefins at atmospheric pressure. An increase in the CO concentration was found to lead to increased selectivity relative to olefins not only due to a diminution in the hydrogenating capacity of the catalyst but also an increase in the rate of the reaction step yielding olefins.L. V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of Ukraine, 31 Nauka Prospekt, 252039 Kiev, Ukraine. Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 32, No. I, pp. 36–39, January–February, 1996. Original article submitted May 22, 1995.     

Effect of zinc added to the Co/Al2O3 catalyst on the formation of carbon nanofilaments from methane and butadiene-1,3

The dynamics of carbon nanofilament growth from methane and butadiene-1,3 on Co-Zn/Al₂O₃ catalysts have been studied in the temperature range 500–750°C. The rate-limiting step in the growth of nanofilaments from butadiene is carbon atom diffusion through the bulk of the metal particle. In the case of methane, the process is controlled by one of the stages of hydrocarbon decomposition on the metal particle. The structure and morphology of the nanofilaments (composites) forming by the carbide cycle mechanism on fine zinc-promoted cobalt particles have been studied by electron microscopy and X-ray diffraction. The morphology and crystallographic properties of the nanofilaments depend on the ratio of the hydrocarbon decomposition rate (which is determined by the nature of the hydrocarbon) to the rate at which carbon atoms diffuse from their formation sites to the nanofilament formation sites (which is determined by the nature of the metal particle and by the carbon diffusion coefficient in the particle bulk). The properties of the resulting carbon nanofilaments can be controlled by varying the nature of the hydrocarbon to be decomposed and the reaction temperature and by introducing another metal into the cobalt particles.     

Effect of surface melting on the formation and growth of nanocrystals in the Bi2O3-Fe2O3 system

Formation of nanocrystals in the Bi₂O₃-Fe₂O₃ system prepared by the co-precipitation of bismuth and iron hydroxides has been studied. The temperature of onset of the BiFeO₃ and Bi₂Fe₄O₉ nanocrystals formation is correlated with the melting point of the non-autonomous phases. The optimal temperature of BiFeO₃ and Bi₂Fe₄O₉ nanoparticles synthesis is 460–520 and 500–550°C, respectively.     

磷钨酸铝催化合成对甲氧基苯乙酮

以H3PW12O40和AlCl3·6H2O为原料合成AlPW12O40,以此为催化剂研究苯甲醚与乙酸酐的酰基化反应,其主要产物为对甲氧基苯乙酮.采用正交试验确定酰化反应的适宜条件为:苯甲醚0.1 mol,苯甲醚与乙酸酐物质的量比为1∶1.5,催化剂用量1 g,反应时间4h,反应温度100℃,在此条件下,产品收率达到69.80％.考察了不同反应底物及不同酰化试剂对反应的影响和不同磷钨酸盐的催化效果,比较了不同加热方式对催化反应的影响.结果表明,磷钨酸铝的催化活性最好,微波加热合成目标产物效果更好.     

ZrO2、Y2O3对CH4燃烧催化剂Fe2O3/γ-Al2O3的改性作用

γ-Ａｌ2Ｏ3作为催化剂载体具有较大的比表面积,机械强度高,孔结构适宜,但不耐高温。近年来,氧化锆载体以其耐高温等[1]独特性质引起多方面的关注[2-4],它能与所负载的金属产生强烈的电子相互作用,影响催化剂的吸附、氧化和还原性能。但是ＺｒＯ2比表面积较小,且随焙烧温度的升高急剧下降,如单独作为催化剂载体,其应用受到很大限制。若将ＺｒＯ2分散到γ-Ａｌ2Ｏ3表面上,可制得兼备两者优点的复合载体。当ＺｒＯ2中加入Ｙ2Ｏ3,能产生特殊的氧空穴[5],具有氧离子传导功能和导电性;与活性组分相结合能在很大程度上提高反应速度。我们用Ｙ…     

Theoretical and experimental study on formation and adsorption of enolic species on Ag-Pd/Al2O3 catalyst

The formation and adsorption of enolic species on a palladium promoted Ag/Al2O3 catalyst (denoted Ag-Pd/Al2O3) during the selective catalytic reduction (SCR) of NOx by C3H6 has been studied by means of DRIFTS and density functional calculations. The structure of the enolic species adsorbed on Ag-Pd/Al2O3 catalyst has been established based on the in situ DRIFTS spectra and simulated results. The reaction mechanism from C3H6 to enolic species on Ag-Pd/Al2O3 catalyst was proposed and the hypothesis about the Pd promotion was discussed.     

The use of SrFe12O19 magnetic nanoparticles as an efficient catalyst in the modified Niementowski reaction

Nanomagnetic SrFe₁₂O₁₉ was synthesized through a simple sol–gel auto‐combustion and then characterized by FT‐IR, XRD, EDXA, VSM, BET and SEM image. Moreover, it was used as catalyst for the first time in the modified Niementowski reaction to investigate its catalytic activity. According to the high yield of quinazolinone products obtained within short reaction times, it was found that SrFe₁₂O₁₉ can be used as an effective and green nanocatalyst in organic reactions. The nanomagnetic catalyst can be easily separated from the reaction mixture using an external magnet.     

Gamma-irradiation effects on the electrical conductivity of pure and Cu-doped Fe3O4 spinel

The electrical conductivity and IR-spectra of pure and Cu-doped Fe₃O₄ spinels were measured at 300–1000 K. Two breaks in the conductivity-temperature curves have been observed for all investigated pure and doped samples. One of these two breaks were found near the Curie point of the investigated spinel. The electrical conduction in -irradiated and non-irradiated pure and Cu-doped Fe₃O₄ occurred by a hopping mechanism due to a fast electron exchange between Fe²⁺ and Fe³⁺-ions present on octahedral sites. The Seebeck-voltage of the irradiated and non-irradiated pure and Cu-doped samples has been measured. The effect of -irradiation on the conductivity values //, activation energy and type of defects was discussed.     

A green solid acid catalyst 12-tungstophosphoric acid H3[PW12O40] supported on g-C3N4 for synthesis of quinoxalines

Research on Chemical Intermediates - A green Keggin-type heteropoly-12-tungstophosphoric acid, (H3[PW12O40].12H2O) supported on graphitic carbon nitride g-C3N4 (HPW/g-C3N4-40), was developed for...     

NiW/Al_2O_3催化剂酸性与加氢活性的调变及对重油加氢脱氮性能的影响

以Ni、W为催化剂的活性金属组分,采用等体积浸渍法制备了NiW/Al2O3加氢脱氮催化剂,考察了Al2O3载体表面经硼酸修饰后对催化剂酸性的影响,以及活性金属与柠檬酸络合后对催化剂加氢反应性能的影响。NH3-TPD、HRTEM、H2-TPR、XPS等表征结果表明,Al2O3载体表面硼酸修饰增加了催化剂表面的中强酸量,减少了强酸量,且削弱了金属与载体之间的强相互作用,但活性中心数目减少。金属与柠檬酸络合可以减小活性相晶粒长度、提高活性相分散性及硫化程度。催化剂的反应评价结果表明,硼酸修饰与柠檬酸络合共同作用可以增强催化剂的重油加氢处理能力,促进芳环与胶质的加氢饱和;具有适宜的氢解与加氢活性,兼顾碱性氮与非碱性氮的脱除,体现了催化剂良好的重油加氢脱氮性能。     

Thermochemical studies on Bi4Ge3O12 and Bi4Ti3O12 single crystals

The specific heat values of Bi₄Ge₃O₁₂ and Bi₄Ti₃O₁₂ single crystals have been studied using a DSC instrument in the temperature range from 323 to 1273 K. The temperature range at which the anomaly associated with transition from polarized to non-polarized phase in Bi₄Ti₃O₁₂ occurred, has been estimated using the shape of the Bi₄Ge₃O₁₂ heat capacity curve as a “normal” one. The heat effect and the entropy change of the transition were evaluated.     

Refined crystal structures of the scandium garnets Ca3Sc2Si3O12, Ca3Sc2Ge3O12, and Cd3Sc2Ge3O12

Journal of Structural Chemistry -     

Sm2O3改性对S2O2-8/ZrO2-SiO2固体超强酸催化剂性能的影响

硫酸促进型固体超强酸催化剂具有极强的酸性,制备简单,在酯化、烷基化、酰基化等有机反应中催化活性高,可重复使用,对设备腐蚀小,环境友好,是一类具有广阔应用前景的新型绿色催化材料,已成为固体超强酸研究的热点之一。然而,目前该类催化剂使用成本高、比表面小、含硫基团容易流失、稳定性差,阻碍了其在工业上的推广和应用。为了探索和改善其催化性能,近年来多组分氧化物的固体超强酸开始引起人们的关注。     

H型镁碱沸石负载对Cu-ZnO-Al2O3催化剂上CO加氢生成烃类的影响

采用三种不同方法制备了Cu-Zn-Al基甲醇催化剂,然后在水相悬浮液中与H型镁碱沸石混合分散,以制得负载型甲醇催化剂.运用X射线衍射、N2吸附-脱附、透射电镜、程序升温还原、NH3程序升温脱附、H2程序升温脱附和X射线光电子能谱对催化剂进行了表征.考察了催化剂催化CO加氢反应生成二甲醚和烃类的性能.该催化剂是在低和高过饱和度条件下采用共沉淀法和均匀沉淀法制得的.制备方法对前驱体的结构特性(如纯度、结晶度和催化剂颗粒粒径分布)有显著影响.低过饱和度的沉淀条件有利于Cu物种的高度分散,增加了催化剂中金属的比表面积,所得催化剂粒径分布均匀.这些效应进而会影响分子筛的性质,导致其微孔孔体积较小,分子筛酸性位被堵塞.通过Cu比表面积和CO转化速率之间的关联可考察甲醇催化剂的性能.     

Effect of coke formation on the transformations of butylenes on a high-silica zeolite catalyst

The transformations of butylenes on a high-silica zeolite catalyst (HHSZC) at 423–773 K were studied. Liquid reaction products formed above 443 K. The liquid phase of the reaction products mainly consisted of aliphatic hydrocarbons at 448–523 K and aromatic hydrocarbons at 623–723 K. The catalyst activity in the formation of liquid products did not show itself until 4–6% consolidation products (CPs) accumulated on its surface. DTA and gravimetric studies showed that CPs were nonuniform in composition. Some of the CPs were removed by decomposition under nitrogen, while others by oxidation with oxygen. It was inferred from ammonia adsorption data that the accumulation of CPs on the surface of HHSZC led to a decrease in the number of acid centers.     

Gamma radiolysis of 3-methylpentane. Effect of added olefins on the formation of C12-olefins

Contributions of congruent (parent derived) olefins to the formation of unsaturated heavy products (C₁₂H₂₄) are investigated. Effects of dose or of olefinic additives on the G yield values are studied by capillary gas chromatography. The dose dependence is explained by transfer of positive charge to congruent olefins (C₆H₁₂) even though their concentrations build up linearly with dose. γ Irradiation of 3-methylpentane containing pentenes or butenes (0.2–2 mol%) provides good examples of transfer of energy, however the results are unexpected. C-H scission in the radiolysis of solid 3-methylpentane is also reviewed.