Environmentally friendly, heterogeneous acid and base catalysis for the methylation of catechol: Chances for the control of chemo-selectivity

The properties of catalysts with (i) Brønsted-type acidity (H-mordenite and Al/P mixed oxide), (ii) Lewis-type acidity (Al trifluoride) or (iii) basic characteristics (Mg/Fe mixed oxide) were investigated in the gas-phase methylation of catechol. When methanol was used as the methylating agent, H-mordenite and AlF₃ gave high selectivities to guaiacol (the product of O-methylation) under mild reaction conditions, that is at very low catechol conversions. An increase in temperature led to the transformation of guaiacol to phenol and cresols, and to considerable catalyst deactivation. The basic catalyst Mg/Fe/O also favored an extensive degradation of guaiacol to phenol. On the mildly acidic catalyst Al/P mixed oxide a stable catalytic performance and a high selectivity to guaiacol at 40% catechol conversion were obtained. When methylformate, a more reactive methylating agent, was used with AlF₃ and Mg/Fe mixed oxide as catalysts, higher catechol conversions and slower deactivation rates could be achieved under mild reaction conditions, with a low extent of guaiacol degradation. However, methylformate rapidly decomposed when temperatures above 350 °C were used. Finally, tests were made by reacting catechol and diethoxymethane with acid catalysts, with the aim of synthesizing methylenedioxybenzene. The latter product was obtained with high selectivity, but with very low yield, due to both catalyst deactivation and decomposition of diethoxymethane.     

离子液体催化C_5馏分中二烯烃的聚合反应

合成了多种基于1-丁基-3-甲基咪唑阳离子的离子液体,并作为裂解C5馏分中混合二烯烃聚合反应的介质。考察了离子液体种类、反应温度、反应时间和添加Lew is酸对混合二烯烃聚合反应的影响。实验结果表明,以硝酸根为阴离子的离子液体对混合二烯烃的聚合反应具有一定的阻聚作用;以六氟磷酸根为阴离子的离子液体能明显促进混合二烯烃的聚合反应,提高二聚物的含量;添加Lew is酸(质量分数为1%的ZnCl2)的离子液体对混合二烯烃的聚合反应具有更明显的促进作用,其效果仅次于酸性氯铝酸类离子液体,反应温度以30℃以下为宜,温度过高将促使二聚物进一步聚合,形成三聚物乃至多聚物,降低二聚物的含量。     

Heterogeneous Enzyme Mimics Based on Zeolites and Layered Hydroxides

Careful combination of a metal compound,a ligand and an inorganic support material leads to supramolecular catalysts that mimic the structural, organizational and functional aspects of enzyme activity.After discussing essential features of metalloenzyme-catalyzed reactions and coordination chemistry in inorganic hosts, we present examples of supramolecular materials selected from our own work that eventually resulted in useful catalysts for organic transformations in the liquid phase.     

Trifluoromethanesulphonic acid catalysed transalkylation between tetrabromobisphenol-a and toluene for the production of 2,6-dibromophenol

The preparation of 2,6-dibromophenol is described. This compound, useful as raw material for brominated poly(phenyleneoxide) and pyrogallol or derived pharmaceuticals/pesticides, was prepared in 80% (isolated) yield by a transalkylation reaction between tetrabromobisphenol-A and toluene. The catalyst, trifluoromethanesulphonic acid, can be simply recovered and recycled. Perfluorinated resin sulphonic acid (NAFION-H®, DuPont) did not effectively catalyse this transalkylation.     

以对硝基氯苯为原料合成对氨基苯甲醚

以对硝基氯为原料，利用相转移催化反应，先制备对硝基苯甲醚，然后用铁屑粉还原对硝基苯甲醚合成氨基苯甲醚。第一步反应在70-80℃下回流5h，对硝基苯甲醚的收率可达97%，第二步反应在102℃下回流2h，对氨基苯甲醚的收率为82%，纯度为99%。     

树状大分子/金属纳米复合物的制备与催化作用

综述了一类新的有机/无机杂化纳米材料———树状大分子/金属纳米复合物的制备及其催化作用。树状大分子/金属纳米复合物是以树状大分子为模板或稳定剂,通过还原树状大分子内或树状大分子间螯合金属离子制备。讨论了树状大分子/金属纳米复合物在水、有机溶剂、氟/有机两相溶剂和超临界CO2中的催化作用。     

Vanadium species in new catalysts for the selective oxidation of methane to formaldehyde: Activation of the catalytic sites

New vanadium oxide supported on mesoporous silica catalysts for the oxidation of methane to formaldehyde were investigated by infrared and Raman spectroscopies to identify and characterize the molecular structure of the most active and selective catalytic sites. In situ and operando experiments have been conducted in order to understand the redox and hydroxylation/dehydroxylation processes of the vanadium species. (SiO)₂VO(OH) species were identified in these catalysts in reaction conditions and shown to undergo a deprotonation at 580 °C under vacuum, leading to a site giving a photoluminescence band at 550 nm attributed to reverse radiative decay from the excited triplet state:

(V⁴⁺–O⁻)^*  (V⁵⁺O²⁻). An activation mechanism of vanadium monomeric species with electrophilic oxygen species is proposed.     

微波辐射活性炭脱硫技术的实验研究

针对我国SO2污染的现状进行了微波脱硫实验研究。利用微波装置和活性炭模拟烟气微波诱导催化还原法(ICR-MW)脱硫,通过正交实验确定了影响脱硫效率的主要因素,在此基础上通过条件实验精确确定了脱硫效率与温度的关系,确认550℃时脱硫效率达到最大值。