Aromatization of methane over different Mo-supported catalysts in the absence of oxygen

Both acidity and structure of the support are important factors in converting methane to aromatics. Lower SiO₂/Al₂O₃ ratio seems to favor the aromatization of methane over the Mo/HZSM-5 catalyst. When Pt is added as a modifier the activity of Mo/HZSM-5 catalyst will decrease slightly, but coke formation will enhanced.     

New Advances in Catalytic Systems for Conversion of CH_4 and CO_2

One of the main goals for developing the C1 chemical industry is the direct conversion of methane and carbon dioxide to useful products. To realize this goal, researches on new catalytic systems are being globally focused. The exploration has been evolved from traditional heterogeneous catalysis into homogeneous catalysis. Coordinate complexes, biochemical and bionics, and photo- and electrochemical catalysis have been extensively studied in recent years. Tests in laboratories have verified for the direct conversion of CH4 to CH3OH that single-pass converstion of CH4 can reach over 70% in both Hg(II) salt and Pt(II) complex systems. The main problem of these systems is the obstacles involving reaction kinetics, so they must be solved before moving to pilot tests. Other catalytic systems discussed in the present article include explorations in the early stage. Among them, features of photo and enzymatic catalyst systems, such as mild reaction conditions, better selectivity and environmentally friendliness     

Water／Oil Biphasic Hydroformylation of Higher Olefins over a TPPTS-Rh／SiO2 Catalyst

A novel TPPTS-Rh/SiO2 catalyst, prepared by directly modifying a heterogeneous high-surface-area Rh/SiO2 catalyst with water-soluble TPPTS ligands, could decrease the resistance of masstransfer in water/oil biphasic media for the hydroformylation of higher olefins. The catalytic performancefor hydroformylation on this biphasic TPPTS-Rh/SiO2 catalyst system was higher than those of thetraditional biphasic HRhCO(TPPTS)3 systems, owing to the chemical bonds between the highly dispersedRh metal particles and the TPPTS ligands. The catalyst system is applicable for hydroformylation ofhigher olefins such as 1-dodecene.     

Eigenmobilities in background electrolytes for capillary zone electrophoresis: III. Linear theory of electromigration

A mathematical model of capillary zone electrophoresis (CZE) based on the conception of eigenmobilities, which are the eigenvalues of a matrix M tied to the linearized governing equations is presented. The model considers CZE systems, where constituents, either analytes or components of the background electrolyte (BGE), are weak electrolytes--acids, bases, or ampholytes. There is no restriction on the number of components nor on the valence of the constituents nor on pH of the BGE. An electrophoretic system with N constituents has N eigenmobilities. In most BGEs one or two eigenmobilities are very close to zero so their corresponding eigenzones move very slowly. However, there are BGEs where no eigenmobility is close to zero. The mathematical model further provides: the transfer ratio, the molar conductivity detection response, and the relative velocity slope. This allows the assessment of the indirect detection, conductivity detection and peak broadening (distortion) due to electromigration dispersion. Also, we present a spectral decomposition of the matrix M to matrices allowing the assessment of the amplitudes of system eigenpeaks (system peaks). Our model predicted the existence of BGEs having no stationary injection zone (or water zone, gap, peak, dip). A common practice of using the injection zone as a marker of the electroosmotic flow must fail in such electrolytes.     

Effect of Drying Methods on the Structure and Combustion Activity of Mn—Substituted Hexaaluminate Catalysts

Conventional oven drying (COD) and supercritical drying (SCD) methods were applied to the preparation of Mn-substituted hexaaluminate (BaMnA111O19-α) catalysts. The effect of drying methods on phase composition, specific surface area, pore structure, reduction behavior of Mn^3 ions, and combus-tion activity of the samples was investigated. The homogenous mixing of the components in the sol-gel process could be maintained by SCD, and the hexaaluminate phase was almost the only phase of the resulting materials after calcination. H2-TPR revealed that the Mn^3 ions in the sample obtained by SCD were easier to be reduced than that by COD. Moreover, the samples obtained by SCD have higher surface area, narrower pore size distribution, and higher combustion activity than those obtained by COD.     

A New Saponin Transformed from Ginsenoside Rh1 by Bacillus subtilis

A novel saponin was isolated from the transformed products of ginsenoside Rh1 by Bacillus subtilis. It‘s structure was determined to be 3-O-β-D-glucopyranosyl-6-O-β-D-glucopyranosyl-20 (S)-protopanaxatriol on the basis of the spectral data.     

FT-IR evidence for the participation of protonic sites in the heterolytic cleavage of C?H bonds of methane over HZSM-5 zeolite

It has been observed by FT-IR spectroscopy that both kinds of Brönsted acid protons present in HZSM-5 zeolite may be involved in the adsorption of methane at low temperature (173 K) and exchange with CH₄ or CD₄ at high temperature (>500°C). The sites which can adsorb methane at low temperature are the active sites for methane conversion at high temperature. Over HZSM-5 zeolite, the activation of methane is suggested to occur via a heterolytic cleavage of C–H bond with the assistance of protons.     

Comparison of 6Mo/MCM-22 and 6Mo/ZSM-5 in the MDA process

A comparison of methane dehydroaromatization (MDA) on 6Mo/MCM-22 and 6Mo/ZSM-5 was carried out using a gas mixture of 90%CH₄, 2%CO₂ and 8%Ar as the feed. The results indicate that the stability of 6Mo/MCM-22 is better than that of 6Mo/ZSM-5. A detailed study reveals that the ability for coke accommodation and the retention of the shape selectivity for aromatics formation is responsible for the stability of a MDA catalyst. This revised version was published online in August 2006 with corrections to the Cover Date.     

Mo/HZSM-5催化剂上甲烷无氧芳构化反应——HZSM-5分子筛脱铝的影响

采用两种不同的脱铝方法对HZSM-5分子筛进行了预处理,并利用MAS NMR和吸附吡啶的FT-IR对分子筛的结构和酸性质进行了表征,考察了分子筛的脱铝程度对Mo基催化剂上甲烷芳构化反应性能的影响.结果表明,HZSM-5分子筛的酸性过强或B酸量不足,均会导致催化剂严重积炭,但积炭成因不同.母体HZSM-5分子筛上的强B酸中心的存在可促使催化剂上反应中间物种深度脱氢,造成催化剂在反应过程中严重积炭.经水热处理的HZSM-5分子筛,骨架铝脱出严重,造成B酸活性中心不足以及部分微孔阻塞,不利于C2中间物种芳构化,导致芳烃选择性显著降低.经高温N2处理的HZSM-5分子筛,骨架铝脱出相对缓和,在消除母体分子筛上强B酸中心的同时,保留了较多的弱B酸中心,既可满足C2中间物种芳构化反应的需要,又可有效抑制催化剂积炭,导致甲烷芳构化反应性能显著改善.     

Fe—Silicalite—2催化剂表面CO2加氢反应性能的研究

研究了Ｆｅ／Ｓｉｌｉｃａｌｉｔｅ－２催化剂ＣＯ２加氢低碳烯烃反应性能，利用ＣＯ２－ＴＰＤ，ＣＯ２／Ｈ２－ＴＰＳＲ和ＣＯ／Ｈ２－ＴＰＳＲ表征手段，考察了铁含量及ＭｎＯ助剂对Ｆｅ／Ｓｉｌｉｃａｌｉｔｅ－２催化剂ＣＯ２吸附脱附及加氢反应性能的影响，表明随铁含量增加可提高催化剂对ＣＯ２的吸附能力，有利于提高ＣＯ２加氢反应的转化率。