Selective N-monomethylation of aniline with dimethyl carbonate over Y-zeolites

The methylation of aniline with dimethyl carbonate was studied and a very high selectivity for N-monomethylation was attained over alkali cation exchanged zeolites. Thus, a 93.5% selectivity for N-methylaniline was obtained at aniline conversion at 99.6% over KY at 453K.     

Selectivity to N-mono or dialkylation in the reaction of aniline with dimethyl carbonate on faujasite,EMT and beta alkaline zeolites

Zeolite K-EMT is as active and selective to N-mono methylation as K–Y in the alkylation of aniline with dimethyl carbonate at 408 or 453 K. No C-alkylation occurs in the temperature range studied. At 503 K, K-X and Cs-X are about 75% selective for dialkylation to N,N-dimethylaniline with about 97% conversion.     

Side chain alkylation of 2-picoline with formaldehyde over alkali modified zeolites

The catalytic side-chain alkylation of 2-picoline with formaldehyde (37 wt/v) was studied over alkali and alkaline earth metal ion modified zeolites in vapor phase conditions at atmospheric pressure, and at a reaction temperature of 300°C. A mixture of vinylpyridine and ethylpyridine were formed by the alkylation of the corresponding picoline over Li, Na, K, Rb, Cs, Mg, Ca, Sr and Ba metal ion modified zeolites. The catalytic activity of side-chain alkylation of 2-picoline was studied over various alkali modified zeolite molecular sieves like ZSM-5 (SiO₂/Al₂O₃ = 30), X, Y, Mordenite and MCM-41. Alkali modified ZSM-5 (30) catalyst was found more active in side-chain alkylation of 2-picoline when compared to other zeolites. Among all these catalysts studied K modified ZSM-5 (30) and K-Cs-ZSM-5 (30) gave best conversion of 2-picoline and selectivity to vinylpyridine. Cs-ZSM-5 (30) and K-ZSM-5 (30) were employed to study the reaction parameters like reaction temperature, weight hourly space velocity, molar ratio, and time on stream for 2-picoline independently. The effects of alkali metal ion content (K, Cs) and precursors of potassium ion on catalytic activity in side-chain alkylation was studied. An attempt has been made to correlate between the basicity with the activity of side-chain alkylation. The bifunctional catalyst is required containing medium or weak acidic centers and basic centers in the side-chain alkylation, which is understood through proposed reaction mechanism. The selectivities of 2-vinylpyridine were 81.7, 90.8, and 94.8% at 65.4, 62.1 and 57.2% conversions at 300°C from 2-picoline and formaldehyde over K-ZSM-5 (30), Rb-ZSM-5 (30) and K-Cs-ZSM-5 (30) respectively. Indian Institute of Chemical technology (IICT) communication no: 020707     

Selective alkylation of aniline with methanol over metallosilicates

The selective alkylation of aniline with methanol was investigated over various metallosilicates synthesized in two different media: alkaline medium (NaOH) and fluorine medium (NH₄F). Through the elemental analysis, XRD, and²⁹Si MAS NMR, it was thought that all the metallosilicates had MFI zeolite structure and the metals were incorporated in metallosilicate framework successfully. Temperature programmed desorption (TPD) of NH₃ and aniline alkylation suggested that the selectivity for N,N-dimethylaniline (NNDMA) is high when the metallosilicates have a large number of medium acid sites (567–673 K), which means that the medium acid sites play an important role in the production of NNDMA. It was also known that metallosilicates synthesized in fluorine medium have strong acid sites (> 773 K) and were deactivated more rapidly than those synthesized in alkaline medium.     

Selectivity engineering in the O‐ versus C‐alkylation of p‐cresol with cyclohexene over sulfated zirconia

Solid acids are more widely used as heterogeneous catalysts, because they are eco‐friendly. This paper reports the results for the Friedel‐Crafts alkylation of p‐cresol with cyclohexene using solid acids sulfated zirconia, 20% w/w dodecatungstophosphoric acid (DTP) supported on K10 clay and ZnCl₂/K10 (Clayzic). This reaction gave substantial amount of 1‐cyclohexyloxy‐4‐methyl benzene (O‐alkylated product) and 4‐cyclo‐hexyl‐4‐methyl phenol (C‐alkylated product). Both products are of commercial importance as perfume and insecticide respectively. Sulfated zirconia catalyst was shown to be better than others studied in terms of activity and selectivity to the O‐alkylated product. The kinetics were studied with sulfated zirconia as catalyst where the rate determining step was the surface reaction between chemisorbed cyclohexene and p‐cresol from the liquid phase within pores according to the Eley‐Rideal mechanism. The production of O‐alkylated p‐cresol is favoured at lower temperatures and C‐alkylated product at higher temperatures. The best operating temperature is 353 K. The activation energies for O‐ and C‐alkylation are 72.68 and 118.28 kj/mol, respectively.     

Au基MOFs双功能催化剂的制备及其催化CO2与苯胺/H2反应性能

以UiO-66(Zr)、MIL-100(Fe)、MIL-100(Cr)、MIL-101(Cr)、NH 2-MIL-101(Al)为载体,Au为活性组分,制备Au/UiO-66(Zr)、Au/MIL-100(Fe)、Au/MIL-100(Cr)、Au/MIL-101(Cr)、Au/NH 2-MIL-101(Al)双功能催化剂。采用XRD、BET、NH 3-TPD、HRTEM等表征催化剂的结构,在釜式反应器中评价催化剂对CO 2与苯胺/H 2反应生成N-甲基苯胺与N,N-二甲基苯胺的N-甲基化反应性能,考察反应条件对催化剂催化性能的影响。结果表明,催化剂的XRD特征衍射峰与相应MOFs的模拟特征峰基本一致;负载Au后催化剂仍具有高的比表面积和大的孔容、孔径;不同MOFs负载Au的催化剂具有不同的酸强度和酸量;Au纳米粒子的分散性很好,粒径为(3~7)nm。制备的催化剂均具有催化CO2与苯胺/H2的N-甲基化反应性能,其中质量分数2%Au/MIL-101(Cr)催化剂催化性能最好,苯胺转化率为45.26%,N-甲基苯胺和N,N-二甲基苯胺选择性分别为73.50%和26.50%,重复使用性能优异。     

N-Ethylation of aniline with ethanol or diethyl carbonate over alkali and alkaline zeolites Y and β

Vapour phase ethylation of aniline was carried out over alkali and alkaline earth exchanged zeolites Y and β. Reaction conditions were optimised for N-alkylation by varying reaction parameters like temperature, WHSV, mole ratio and time on stream. Over all zeolites, N-alkylation is much higher than C-alkylation. Diethyl carbonate is a better N-alkylating agent than ethanol. Among the catalysts studied, Kβ is a good N-monoalkylating catalyst with 41% aniline conversion and 100% selectivity at 473 K, WHSV 19.8 h⁻¹ and diethyl carbonate/aniline ratio 2.     

Vapour phase O‐methylation of 2‐naphthol over the solid bases alkali‐loaded silica and Cs‐loaded MCM‐41

O‐alkylation of 2‐naphthol has been investigated in the vapour phase over alkali‐loaded fumed silica and Cs‐MCM‐41. Both SiO₂ and MCM‐41 had low C‐alkylation activities and no O‐alkylation activity. The introduction of alkali ions considerably increases 2‐naphthol conversion with 2‐methoxynaphthalene being the major product. The activity of the catalysts increases with alkali loading and the basicity of the metal (Cs > K > Na > Li). Very high conversion (∼99%) of 2‐naphthol and selectivity (>95%) for 2‐methoxynaphthalene are obtained over Cs‐loaded fumed silica and MCM‐41. A small amount of 1‐methyl‐2‐hydroxynaphthalene is also formed over the Li‐, Na‐ and K‐loaded silica. This revised version was published online in July 2006 with corrections to the Cover Date.     

苯胺在超临界水中氧化反应动力学的研究

对苯胺在超临界水中的氧化反应进行了研究。发现随温度升高和停留时间延长,苯胺去除率和COD去除率增大,并且只有在温度高于898.15K条件下,苯胺氧化的COD去除率才有可能达到90％以上。在873.15K～898.15K范围内,温度对苯胺氧化的COD去除率有较显著的影响。在673.15K～748.15K、25.0MPa、300％过氧量、2.351×10-4mol(L-1苯胺浓度条件下,苯胺反应级数为1.554,反应的活化能为2.96(104J(mol-1,频率因子为6.69×103。     

Volatility and phase stability of petrol blends with ethanol

Blending ethanol in to petrol can be associated with problems related to volatility and phase stability of the blends. Ethanol up to 20 vol% in petrol forms an azeotropic mixture with hydrocarbons. Ethanol has affinity to water and air humidity and it increases the water solubility in ethanol-petrol blends. In this work, the influence of ethanol up to 10 vol%, ETBE up to 10 vol% and hydrocarbon composition over volatility, distillation characteristics and miscibility of ethanol-petrol blends with water was studied. It was found that higher content of saturated hydrocarbons in petrol increased the vapour pressure of azeotropic ethanol blend. Aromatics and alkenes influenced the azeotrope vapour pressure, phase separation temperature and ethanol extraction in a positive way. The results showed that the ETBE can soften effects of the ethanol blending to petrol. ETBE decreased the vapour pressure and the phase separation temperature of the ethanol-petrol blends.     

Three‐Phase Nitrobenzene Hydrogenation over Supported Glass Fiber Catalysts: Reaction Kinetics Study

The catalytic properties of Pd and Pt supported on woven glass fibers (GF) were investigated in the three‐phase hydrogenation of nitrobenzene (NB). Over all catalysts, a 100 % yield of aniline was attained. The catalytic activity for the best catalysts was two times higher than the activity of commercial Pt/C catalyst traditionally used for liquid–phase hydrogenation. The intrinsic reaction kinetics were studied and a reaction scheme is suggested. The direct formation of aniline from NB was observed over Pd/GF with traces of intermediates. Four intermediate products were detected during aniline formation over Pt/GF: nitrosobenzene, phenylhydroxylamine, azoxybenzene, and azobenzene. The Eley‐Rideal kinetic model fits the experimental data well. The parameters of the model were determined as a function of initial NB concentration and hydrogen pressure. Pt and Pd supported on GF in woven fabrics are suggested as suitable materials for reactors with a structured catalytic bed in multi‐phase reactor performance.     

Alkylation of benzene with isopropanol over SAPO‐5: A kinetic study

The kinetics of benzene alkylation with isopropanol has been studied in vapour phase over SAPO‐5 catalyst. On the basis of the product distribution pattern obtained over this large pore molecular sieve, a reaction mechanism has been proposed. Based on this reaction network, suitable phenomenological models have been derived and fitted to the kinetic data. A Langmuir‐Hinshelwood model with surface reaction involving single site mechanism fitted the data better than the other models. The deactivation kinetics has also been investigated in the low temperature chosen. The activation energy for the deactivation reaction in this range is found to be lower than that for the main reaction.     

丙烯与苯液相烷基化合成异丙苯中副产物正丙苯生成的研究

进行了Y沸石改性催化剂液相烷基化工艺条件对副产物正丙苯生成影响的实验,考察了液相烷基化中副产物正丙苯生成途径。结果表明,液相烷基化反应产物中总的正丙苯生成量,除了丙烯与液相苯烷基化反应直接生成外,一半以上是由于多异丙苯烷基转移反应生成的。通过正丙苯生成动力学的研究,得到了463-478K温度下液相烷基化过程总的正丙苯生成的速率方程和其中烷基转移生成正丙苯的速率方程。     

H3PW12O40 Supported on AlMCM-41 molecular sieves: An effectual catalyst for t-butylation of anisole

Mesoporous AlMCM-41 (Si/Al = 25) molecular sieves was synthesized and impregnated with different loadings (10, 20 and 30 wt% H₃PW₁₂O₄₀) of phosphotungstic acid. Their catalytic performance was examined in the vapour phase alkylation of anisole with tert-butanol. The major products were found to be 2-tert-butyl anisole (2-TBA), 4-tert-butyl anisole (4-TBA), 2,4-di-tert-butyl anisole (2,4-DTBA). 4-TBA was the major product formed with high selectivity. The influence of temperature, feed ratio, WHSV was studied and the results are discussed.     

催化剂制备与研究 石墨烯/聚苯胺复合材料的制备及其光催化性能

以苯胺和氧化石墨烯溶液为原料,采用乳液聚合法,根据m(氧化石墨烯)∶m(苯胺)为0∶10、1∶20和1∶10合成不同石墨烯/聚苯胺复合材料。采用紫外可见分光光度计、SEM、XRD及FT-IR对复合材料进行表征。XDR和FT-IR表明,乳液聚合合成了石墨烯/聚苯胺复合材料。SEM表明,聚苯胺以氧化石墨烯为载体,分散在其表面。光催化结果表明,石墨烯/聚苯胺复合材料的光催化性能较纯聚苯胺明显提高,m(氧化石墨烯)∶m(苯胺)=1∶20的石墨烯/聚苯胺复合材料的光催化性能高于m(氧化石墨烯)∶m(苯胺)=1∶10,原因可能在于微观结构的不同。     

Performance of potassium 12-tungstophosphoric salts as catalysts for isobutane/butene alkylation in subcritical and supercritical phases

Potassium salts of H₃PW₁₂O₄₀ heteropolyacid have been synthesised with different K contents and studied for their acid and catalytic properties in liquid phase isobutane alkylation by but-2-ene or but-1-ene. Subcritical and supercritical conditions have been chosen for comparison in a batch reactor.

The influence of the protonic site density has been studied. High acid density was observed to be detrimental for akylation reaction which was explained by increased olefin dimerisation, the main side reaction responsible of catalyst poisoning. A K_2.6H_0.4P sample was tested in a batch reactor in liquid subcritical, near supercritical and in low and high density supercritical isobutane/butene mixture (418 K, P=4–9 MPa). An increase in the quality of the alkylate with the density of the supercritical phase was observed which almost counterbalanced the negative effect of the high temperature necessary to reach supercritical isobutane conditions.

In the presence of porous alkaline salts of 12-tungstophosphoric acid, alkylation to oligomerisation ratio is significantly improved over solids with a low density of strong Brønsted sites and by the use of high density supercritical isobutane conditions, the latter preserving hydride transfer and trimethyl pentane (TMP) formation.     

广州大学城水体中硝基苯和苯胺的含量情况调查

建立了HPLC法直接分析水样中硝基苯和苯胺含量的方法,并调查了广州大学城水体中硝基苯和苯胺的含量。液相条件：进样量10μL;色谱柱：Kromasil C18色谱柱（5μm,250 mm×4.6 mm）;流速1 mL/min,乙腈-水梯度洗脱;硝基苯检测波长：262nm,苯胺检测波长231 nm。硝基苯和苯胺标准曲线均线性良好（r〉0.999）,其RSD分别为0.57%和1.25%。方法回收率在90%～110%之间。仪器对硝基苯和苯胺的检测线分别为：24.1μg/L和18μg/L。经检测广州大学城水体中基本没有检出硝基苯和苯胺。     

Side-chain alkylation of 2,6-lutidine to 2,6-divinylpyridine over basic zeolites

Synthesis of 2,6-divinylpyridine (2,6-DVP) and 2-methyl-6-vinylpyridine (2M6VP) was achieved for the first time by side-chain alkylation of 2,6-lutidine using formaldehyde (37 wt/v) as alkylating agent in heterogeneous conditions at atmospheric pressure, and at a reaction temperature of 300 °C over alkali and alkaline metal ion modified zeolites. A mixture of 2,6-divinylpyridine and 2-methyl,6-vinylpyridine were formed by the alkylation of the 2,6-lutidine over Li, Na, K, Rb, Cs, Mg, Ca, Sr and Ba metal ion modified zeolites. The catalytic activity of 2,6-lutidine was studied over various potassium metal ion modified zeolite molecular sieves like ZSM-5 (30), X, Y, mordenite and MCM-41. Alkali modified ZSM-5 (30) catalyst was found more active in side-chain alkylation of 2,6-lutidine when compared to other zeolites. Among all these catalysts studied K modified ZSM-5 (30) gave best conversion of 2,6-lutidine and selectivity to 2-methyl,6-vinylpyridine. K-ZSM-5 (30) catalyst was employed to study the reaction parameters like reaction temperature, weight hourly space velocity, molar ratio, and time on stream for 2,6-lutidine. The effect of potassium metal ion content and precursors of potassium ion on catalytic activity in side-chain alkylation of 2,6-lutidine was studied. The bifunctional catalyst is required containing medium or weak acidic centers and basic centers in the side-chain alkylation, which is understood through proposed mechanism. The selectivities of 2,6-DVP were 45.2, 40.0, and 30.7% at 73.4, 66.0 and 60.5% conversion at 300 °C from 2,6-lutidine and formaldehyde over K-ZSM-5 (30), Rb-ZSM-5 (30) and Cs-K-ZSM-5 (30), respectively.     

Spinel-Type Cobalt Chromites as Novel and Highly Ortho-selective Catalysts for Phenol Alkylation

The gas phase catalytic alkylation of phenol with methanol was investigated over a series of spinel-type cobalt chromite catalysts. The molar ratio of Co/Cr and the calcination temperature have considerable effect on the catalytic performance of the samples. Among them, the Co/Cr=0.8 sample calcined at 723 K shows the highest activity (97.3% phenol conversion) with a total 94.8% ortho-selectivity to o-cresol and 2,6-xylenol at the reaction temperature of 693 K.