PET synthesis in the presence of lanthanide catalysts

Syntheses of poly(ethylene terephthalate), PET, by transesterification of dimethyl terephthalate with ethylene glycol in the presence of well-known catalysts and various lanthanide compounds were performed. Lanthanide catalysts appeared to be much more efficient in the first stage of the process (transesterification in the presence of an excess of ethylene glycol), and less active in polycondensation. PET produced with lanthanides was found to possess enhanced thermal and hydrolytic stability as compared to PET synthesized with well-known catalysts and commercial PET. © 1995 John Wiley & Sons, Inc.     

甲烷制乙烯新型催化剂的制备

本文对微波法诱导甲烷与二氧化碳制乙烯研究进行了研究,得出合成的催化剂和其组成对此反应起着巨大的作用。从研究数据表明,微波法制乙烯所用催化剂降低了反应的温度,减少了碳化的生成。但甲烷转化率和乙烯选择率仍较低。所以,进一步提高催化剂的反应活性和选择性是实现沼气制取乙烯的工业化生产的关键。本文合成了四种新型催化剂,其具有巨大的研究意义。     

新型甲醇合成催化剂的研制

本文采用不同的制备方法制备铜基甲醇合成催化剂，利用XRD、TPR、BET、SEM、TEM等技术手段对所制备催化剂的物相组成、物相结构、活性比表面、表面形貌、粒子大小进行了研究；并进行了活性评价。研究结果表明，用硝酸盐共沉淀法制备的催化剂，其性能和结构均优于用蒸氨法制备的催化剂。     

PET缩聚催化剂乙二醇盐的合成与应用技术进展

介绍了聚对苯二甲酸乙二醇酯(PET)缩聚反应用催化剂乙二醇盐的合成与应用进展;详述了乙二醇锑、乙二醇钛、乙二醇铝催化剂的合成和应用,以及应用各种催化剂的优缺点;指出乙二醇锑催化剂活性高,但污染严重,乙二醇铝催化剂毒性低,催化活性也低。综合考虑,绿色环保的乙二醇钛及其复合催化剂将是聚酯的良好催化剂,将替代现有锑系催化剂,前景看好。     

Carbon gasification in the presence of metal catalysts

The development of new processes for the production of gaseous fuels from carbon-containing solids is essential in meeting the energy needs of the nation. In this paper, catalysed carbon gasification is examined. The change in the reactivity of the interface between gaseous reactant (hydrogen or steam) and solid carbon has been measured in the presence of various metal catalysts. With platinum it is found that over a range of temperatures the specific rate of methane production is of the same magnitude as the rate of hydrogen atomization. The catalytic effect is interpretable in terms of an enhanced rate of hydrogen dissociation on the metal surface, followed by surface diffusion across the metal/carbon interface and reaction with carbon. The gas formation rate during the interaction of water vapour with catalyst-activated carbons has been increased by more than an order of magnitude by depositing small weight fractions of active metal catalyst on the carbon surface. At the temperatures employed in this study (975–1175 K), carbon monoxide and hydrogen are the products of the catalysed reaction for each of the catalysts examined.     

Guaiacol hydrodeoxygenation in the presence of Ni-containing catalysts

A series of Ni-containing catalysts supported on different materials has been tested in the hydrodeoxygenation of guaiacol, a compound modeling the products of biomass fast pyrolysis. The reaction has been carried out in an autoclave at 320°C and a hydrogen pressure of 17 MPa. The main guaiacol hydrodeoxygenation products are cyclohexane, 1-methylcyclohexane-1,2-diol, and cyclohexanone (which result from aromatic ring reduction). A guaiacol conversion scheme explaining the formation of the main products is suggested. The highest activity is shown by the Ni-containing catalysts on SiO₂ and SiO₂-ZrO₂ supports prepared by the sol-gel method. According to X-ray diffraction and electron microscopic data, the high activity of these catalysts is due to the high concentration of dispersed nickel as reduced films on the surface of the silicate structures. The catalysts offer promise for refining the biomass fast pyrolysis products (bio-oil) into hydrocarbon fuel.     

Selectivity control in substituted fatty amines synthesis from esters or nitriles in the presence of bifunctional catalysts

Copper chromite-type catalysts, supported by alumina or graphite and promoted with barium, were used for the onestep synthesis of tertiary fatty amines [R₂NCH₃ or RN(CH₃)₂] from ester, acid or nitrile and ammonia, methanol and hydrogen. The surface composition of the catalysts, studied by X-ray photoelectron spectroscopy and by adsorption experiments, showed that there was a correlation between selectivity and the presence of a well-dispersed CuCrO₂ phase, stabilized with barium. Moreover, the elements influencing the stability of the copper catalysts were also studied, and the promoter or/and the support increased the copper surface area and the stability of the catalyst in the presence of water or ammonia.     

Selectivity effects of a new aluminum species in strongly dealuminated USY containing FCC catalysts

We have hydrothermally prepared and characterized a catalytically active tetrahedral aluminum species in faujasite distinct from the normal framework aluminum. The new tetrahedral species is formed after a severe steam dealummation at 830°C and is characterized by a²⁷A1 MASNMR shift of about 53 ppm compared to the 60 ppm shift observed for framework tetrahedral aluminum. DRIFTS experiments show that the 53 ppm species is associated with a Lewis rather than a protonic site. This species is associated with strong acidity and poor cracking selectivity compared to a conventional dealuminated faujasite at the same unit cell size. This site is very active and makes large amounts of gas and coke with poor gasoline selectivity compared to typical commercial FCC catalysts. After an appropriate sequence of hydrothermal dealumination and controlled pH washing steps, the 53 ppm species is the only species observed by NMR.     

The synthesis of poly-/p-phenylene sulphide/from thiophenol in the presence of various acidic catalysts

Summary In the present work the synthesis of poly-/p-phenylene sulphide/ from thiophenol in the presence of various acidic catalysts has been investigated. Structural similarity of the obtained polymers to the polymer produced by Phillips Petroleum Co. was studied.     

CH4和CO2在临氧条件下多相催化合成乙酸

在总结国内外CH₄-CO₂直接合成乙酸和CH₄、CO₂在临氧条件下活化转化的研究进展基础上，论证了在CH₄-CO₂体系引入氧改善热力学和在多相催化作用下直接合成乙酸的可行性。     

Reaction of N-phenylhydroxylamine in the presence of clay catalysts

The condensation reaction of N-phenylhydroxylamine in the presence of clay catalysts was studied. The main products of this reaction are azoxybenzene, aniline and nitrosobenzene. In contrast with the previously published results, p-nitrosodiphenylamine is not formed during the condensation reaction. This revised version was published online in July 2006 with corrections to the Cover Date.     

Hydrogenation of model compounds in the presence of iron-containing catalysts

A method for the preparation of a composite iron oxide catalyst on a carbon support is described in this work. The hydrogenation of model polyaromatic compounds in the presence of iron-containing catalysts was studied.     

Synthesis of mullite in the presence of nanodisperse aluminum powder

Synthesis of mullite from a mixture of -Al₂O₃ + -SiO₂ and native kaolin-based materials in the presence of nanodisperse aluminum is reported. In both cases, addition of nanodisperse Al increases the yield of mullite and stabilizes its structure.__________Translated from Novye Ogneupory, No. 11, pp. 28 – 33, November, 2004.For previous communications, see Novye Ogneupory, Nos. 7 – 10, 2004.     

环己基苯的合成及其催化剂研究进展

环己基苯经过氧化反应可生产苯酚和环己酮,还可以用作锂离子电池电解液的添加剂,也可用作柴油的十六烷值调和组分,是一种高附加值、有市场潜力的精细化学品。本文介绍了国内外通过苯与环己烯烷基化合成环己基苯及所用催化剂的研究进展,总结了苯加氢烷基化反应机理和反应路径的研究成果,包括加氢烷基化活性的来源、中间产物和碳正离子中间体的推断以及各反应产物的形成。通过对加氢烷基化机理的认识,回顾了加氢烷基化催化剂的设计思路和发展历程。最后指出可开发用于苯与环己烯烷基化的B酸型、B-L酸型以及固载化离子液体等新型催化剂。提出可借助最新的碳正离子研究手段对加氢烷基化机理进行补充完善,并认为可利用多级孔沸石作为加氢烷基化催化剂的酸性载体。     

Promoting effect of an aluminum emulsion on catalytic performance of Cu-based catalysts for methanol synthesis from syngas

Copper-based catalysts modified with aluminum precursors having different morphologies for methanol synthesis were prepared and the effect of the addition of aluminum emulsion on the characteristics of the catalyst was studied by using X-ray diffraction (XRD), temperature-programmed reduction (TPR) and differential thermal gravity (DTG). The experiment results show that the copper-based catalyst prepared by mixing a Cu-Zn precipitate with an amorphous aluminum emulsion prepared in advance by precipitating an aluminum salt with ammonia exhibits higher specific surface area and catalytic performance for methanol synthesis from synthesis gas. The catalysts thus prepared were found to have more (Cu,Zn)₂CO₃(OH)₂ phase, from which more Cu/Zn sosoloid was produced during calcination. More sosoloid phase produced and stronger synergy between Cu and ZnO were verified to enhance the activity of the catalyst for methanol synthesis.     

Pyrolysis of biomass in the presence of Al-MCM-41 type catalysts

Al-MCM-41 type mesoporous catalysts were used for converting the pyrolysis vapours of spruce wood in order to obtain better bio-oil properties. Four Al-MCM-41 type catalysts with a Si/Al ratio of 20 were tested. The catalytic properties of Al-MCM-41 catalyst were modified by pore enlargement that allows the processing of larger molecules and by introduction of Cu cations into the structure.Spruce wood pyrolysis at 500 °C was performed and the products were analysed with the help of on-line pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). In addition, thermogravimetry/mass spectrometry (TG/MS) experiments were applied for monitoring the product evolution under slow heating conditions (20 °C/min) from 50 to 800 °C.Levoglucosan is completely eliminated, while acetic acid, furfural and furanes become quite important among cellulose pyrolysis products over the unmodified Al-MCM-41 catalyst. The dominance of phenolic compounds of higher molecular mass is strongly cut back among the lignin products. Both the increase of the yield of acetic acid and furan and the decrease of large methoxyphenols are repressed to some extent over catalysts with enlarged pores. The Cu modified catalyst performed similarly to the catalyst with enlarged pore size in converting the pyrolysis vapours of wood, although its pore size was similar to the unmodified Al-MCM-41.     

Oxidative degradation properties of Co-based catalysts in the presence of ozone

Four series of cobalt-based catalysts, such as bare Co₃O₄ and CoO, CoO_x–CeO₂ mixed oxides, CoO_x supported over alumina and alumina–baria and CoMgAl and CoNiAl hydrotalcites have been synthesized and investigated for the oxidative degradation of phenol in the presence of ozone. Characterizations were obtained by several techniques in order to investigate the nature of cobalt species and their morphological properties, depending on the system. Analyses by XRD, BET, TPR, UV–visible diffuse reflectance spectroscopy and TG/DT were performed.

The CoNiAl hydrotalcite exhibits, after 4 h of reaction, the highest phenol ozonation activity followed by Co(3 wt%)/Al₂O₃–BaO and CoMgAl. The samples Co(1 wt%)/Al₂O₃–BaO and Co(1 and 3 wt%)/Al₂O₃ show a comparable medium activity, while the oxidation properties of bare oxides Co₃O₄, CoO and CoO_x–CeO₂ are really low. Leaching of cobalt ions in the water solution was detected during the reaction, the amount varied depending on the nature of catalysts. A massive release was observed for the CoMgAl and CoNiAl hydrotalcites, while cobalt catalysts over alumina and alumina–baria look much more stable. The recycle of CoO_x/Al₂O₃ and CoO_x/Al₂O₃–BaO was studied by performing three consecutive cycles in the phenol oxidation. Because of the potential interest of the cobalt-supported catalysts in the ozonation process, the oxidative degradation of naphtol blue black was also investigated.

On the basis of TPR and UV–visible results it appears that highly dispersed Co²⁺ ions especially present over Co(3 wt%)/Al₂O₃–BaO are the main active sites for phenol and naphtol blue black oxidative degradation by ozone.