Transesterification of dimethyl carbonate with phenol over a bimetallic molybdenum and copper catalyst

Mo-Cu bimetallic oxides were found to be efficient heterogeneous catalysts for the transesterification of dimethyl carbonate (DMC) with phenol. When the reaction was carried out between 150 and 180°C, with a molar of Mo/Cu of 1:1, molar ratio of phenol/DMC of 1:1, 4.8 wt.% of the catalyst, 9 h, the conversion of phenol was 49.9%, and the total yield of MPC and DPC was 45.4%. Catalyst reuse showed a gradual decline in the catalytic activity. The decrease in catalytic activity might be due to leaching out of Mo and Cu, and/or carbon deposition.     

Al-MCM-41介孔分子筛催化对甲酚叔丁基化反应的研究

2-叔丁基对甲酚是一种有机中间体,在有机合成领域中占有重要地位,被广泛应用于表面活性剂、高档酚类抗氧化剂2246和2246-S、紫外线吸收剂UV-326等的生产[1]。特别是近十年来,以抗热老化为特征的功能性高档酚类抗氧化剂在国内外相继问世,它们对于提高聚合物材料的成型加工性能、     

介孔催化剂上苯酚和二氧化碳直接合成碳酸二苯酯

采用等体积浸渍法制备了介孔分子筛SiMCM-41负载的ZnCl2、ZnO、FeCl3和Fe2O3催化剂,并用于苯酚与二氧化碳在CCl4溶液中合成碳酸二苯酯.采用29SiNMR、ICP、XRD和UV-Raman等技术对催化剂的结构性质、活性组分和载体间的相互作用以及反应前后催化剂结构变化等进行了研究.结果表明,载体SiMCM-41在反应过程中表现出较高的稳定性,ZnCl2、ZnO、FeCl3及Fe2O3负载到介孔SiMCM-41上,金属离子和载体表面硅羟基结合生成固载型活性中心,防止了金属离子在反应过程中从催化剂表面的流失.以二氧化碳、苯酚和碳酸钾为原料,在四氯化碳溶液中反应合成碳酸二苯酯(DPC)时,锌负载催化剂具有较高的催化活性和DPC选择性.     

自制Ti/W-MCM-41介孔分子筛催化制备乳酸戊酯

采用自制的介孔分子筛Ti/W-MCM-41催化乳酸与正戊醇的酯化反应,合成了乳酸正戊酯;利用红外光谱仪分析了催化剂的化学特征,考察了分子筛的WO3质量分数、催化剂用量、醇酸物质的量比、反应时间、催化剂重复使用性能等因素对目标产物酯化率的影响.结果表明,在nSi∶nTi=30∶1,WO3质量分数10%,550℃下焙烧6h条件下制得的催化剂具有良好的催化性能;其催化合成乳酸正戊酯适宜的反应条件为:0.2mol乳酸,催化剂用量0.5g,n(正戊醇)∶n(乳酸)=1.6∶1,反应时间100min,酯化率可达94.4%.该催化剂使用7次酯化率仍可达86.6%.     

Surface characterization and catalytic evaluation of copper-promoted Al-MCM-41 toward hydroxylation of phenol

The Mobil Composition of Matter No. 41 (MCM-41) containing Cu and Al with Si/Al ratios varying from 100 to 10 and 1 to 6 wt.% of Cu was synthesized under hydrothermal and impregnation conditions, respectively. The samples were characterized by nitrogen adsorption–desorption measurements, X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), UV–Vis diffuse reflectance spectroscopy (UV–Vis DRS), temperature-programmed reduction (TPR), temperature-programmed desorption (TPD), and ²⁹Si and ²⁷Al magic-angle spinning–nuclear magnetic resonance (MAS–NMR) spectra. X-ray diffraction patterns indicate that the modified materials retain the standard MCM-41 structure. TPR patterns show the two-step reduction of Cu species. TPD study shows that Cu-impregnated Al-MCM-41 samples are more acidic than Al-MCM-41. From the MAS–NMR it was confirmed that most of the Al atoms are present tetrahedrally within the framework and some are present octahedrally in extraframework position. Impregnation of Cu shifted Al to the extraframework position. The catalytic activity of the samples toward hydroxylation of phenol in aqueous medium was evaluated using H₂O₂ as the oxidant at 80 °C. The effects of reaction parameters such as temperature, catalyst amount, amount of H₂O₂, and solvent were also investigated. Sample containing 4 wt.% copper-loaded Al-MCM-41-100 showed high phenol conversion (78%) with 68% catechol and 32% hydroquinone selectivity.     

Diastereoselective synthesis of propargylamines catalyzed by Cu-MCM-41

In this work, a rapid, efficient and protecting group free diastereoselective synthesis of propargylamines through a multicomponent coupling reaction between (S)-prolinol, phenylacetylene and commercially available aldehydes catalyzed by Cu-MCM-41 in heterogeneous phase is reported. The reactions were carried out under solvent free conditions with good yields and moderate reaction times. In all the cases, catalyst was recovered and reused up to five cycles. Recyclability of the catalyst, low catalyst loading, solvent and protecting group free conditions, and the use of inexpensive catalyst are the key features that provide green aspects to this synthetic protocol.     

MCM-41/SBA-15中孔分子筛对生物质热解油的催化裂解研究

以中孔MCM 41/SBA 15分子筛作催化剂,对不同条件下快速热解得到的木屑热解蒸气进行催化裂解,采用元素分析、凝胶色谱(s.e.c.)和气质联用（GC MS）等手段表征。结果表明,同未加催化剂比较,分子筛MCM 41/SBA 15的存在可使热解液体中氧的质量分数降低,长链化合物所占比例明显减小,其中SBA 15作催化剂比MCM 41作催化剂对热解蒸气裂解更容易得到接近柴油和汽油分子量的热解油,但芳香类化合物的质量分数明显增加。热解油中Pentadecane、Hexadecane、Dimethyjbenzene、Naphthalene等质量分数增加,而含氧类物质Methyl Phenol、2 Methoxy 4 Methyl Phenol、2 Methoxy 4 Propyl Phenol 等质量分数减少。     

奎宁-杂多酸杂化催化剂催化H2O2为氧源的苯羟基化反应

将奎宁与Keggin结构磷钼钒杂多酸结合制备出一种新颖的多相苯羟基化杂化催化剂, 采用傅里叶变换红外光谱、紫外-可见光谱、X射线衍射、扫描电镜、热重、N₂吸附-脱附和CHN元素分析等表征手段对催化剂进行了分析. 结果表明, 该催化剂是一种具有较高比表面积和孔体积的半无定形有机杂多酸盐. 在H₂O₂为氧源的苯羟基化反应中, 杂化催化剂引导了液-固两相催化体系, 表现出较高催化活性和重复使用稳定性. 催化剂中奎宁与杂多阴离子间的氢键和电子相互作用赋予了其高熔点和难溶性, 而高比表面积和因奎宁而改善的杂多阴离子的氧化还原性是其获得优异催化性能的主要原因. 这为多相苯羟基化反应提供了一种新的且制备便捷的基于多金属氧酸盐的高效催化剂.     

Zr-MCM-41的合成及其表征

以Zr(NO3)4·3H2O为锆源，通过直接合成法得到了Zr-MCM-41介孔材料，考察了不同Zr/Si摩尔比对样品的影响，其中Zr/Si的摩尔比最大为0.25。随着Zr/Si的摩尔比的增加，2θ=2°附近的100晶面的衍射峰强度逐渐降低，当Zr/Si摩尔比大于0.25后得不到介孔Zr-MCM-41材料。对所得样品采用XRD、TG-DTA、N2吸附 脱附几种分析方法进行了表征。     

TiO~2修饰的介孔分子筛MCM-41的合成、表征及光 催化性研究

首次以三种不同的含钛有机物为氧化钛的前驱体,合成了三种TiO~2呈单层分散状态的TiO~2修饰的介孔分子筛MCM-41,并以XRD,FT-IR,液氮温度下N~2吸附-脱附曲线,固体UV-vis漫反射等表征手段对其结构特征和氧化钛分散状态进行了研究。TiO~2在介孔分子筛MCM-41孔道中分散,MCM-41仍能保持骨架结构,没有晶相TiO~2生成;TiO~2与MCM-41孔道表面的≡Si－OH以化学键连接,生成Si－O－Ti键;TiO~2在MCM-41内孔壁呈均匀单层分散状态;TiO~2粒子的减小使其对紫外光的吸收发生明显的蓝移现象。并以苯酚降解反应为模型检验合成的具有光催化性的TiO~2修饰的MCM-41的光催化活性。     

Supported bimetallic polymers of porphyrins as new heterogeneous catalyst

New heterogeneous catalytic systems of mono and bimetallic polymeric porphyrinic structures confined to Au surface are described. The solid materials were characterized by AFM, SEM and EDS/EDX techniques. The polymeric films have been deposited by consecutive voltammetric cycles. The appearance of a peak at 380 mV (vs. Ag/AgCl), is only observed in the first cathodic scan of the bimetallic structures and was attributed to Cu(III)/Cu(II) reduction in polyFeCuPP. In all the cases studied, the bimetallic structures were up to 3.5 times more efficient catalyst than the corresponding monometallic.

PolyCoCuPP is intrinsically weaker than polyFeCuPP. Nevertheless, the mass deposited is significantly higher (80%). For this reason, polyCoCuPP is considered the best catalyst under practical considerations.

The use of a solid catalyst with a small amount of H₂O₂, in aqueous solution, makes this oxidation an environmentally benign chemical process.     

Zirconia-supported phosphotungstic acid as catalyst for alkylation of phenol with benzyl alcohol

The liquid-phase alkylation of phenol with benzyl alcohol was carried out using zirconia-supported phosphotungstic acid (PTA) as catalyst. The catalysts with different PTA loadings (5–20 wt.% calcined at 750 °C) and calcination temperature (15 wt.% calcined from 650 to 850 °C) were prepared and characterized by ³¹P MAS NMR and FT-IR pyridine adsorption spectroscopy. The catalyst with optimum PTA loading (15%) and calcination temperature (750 °C) was prepared in different solvents. ³¹P MAS NMR spectra of the catalysts showed two types of phosphorous species, one is the Keggin unit and the other is the decomposition product of PTA and the relative amount of each depends on PTA loading, calcination temperature and the solvent used for the catalyst preparation. The catalysts with 15% PTA on zirconia calcined at 750 °C showed the highest Brönsted acidity. At 130 °C and phenol/benzyl alcohol molar ratio of 2 (time, 1 h), the most active catalyst, 15% PTA calcined at 750 °C gave 98% benzyl alcohol conversion with 83% benzyl phenol selectivity.     

Effect of tetrabutylammonium bromide on enzymatic polymerization of phenol catalyzed by horseradish peroxidase

In this article tetrabutylammonium bromide （TBAB） was first added in buffer to compose a convenient and environmentally friendly system, and enzymatic polymerization of phenol catalyzed by horseradish peroxidase （HRP） could proceed efficiently in this system. When TBAB was added, the most conversion of phenol could reach 99.1%. The phenol polymer was considered to consist of a mixture of phenylene （Ph） and oxyphenylene （Ox） units by IR analysis, and the ratio of phenylene to oxyphenylene units （Ph/Ox） was measured by titration. Moreover, the effects of the dosage of horseradish peroxidase （HRP） and pH value on the conversion of phenol were investigated. The reaction performed very effectively in this novel system when the addition of HRP was only 0.2 mg. In all cases, the weight-average molecular weight calculated by GPC-SLS was in a range from 12000 Da to 30000 Da. The phenol polymer prepared in the present research possessed good thermal stability shown by TG analysis.     

In situ ethylation of organolead,organotin and organomercury species by bromomagnesium tetraethylborate prior to GC‐ICP‐MS analysis

An analytical method for simultaneous in situ ethylation, of organolead, organotin and organomercury compounds in aqueous samples was developed using a new derivatisation agent, bromomagnesium tetraethylborate (BrMgEt₄B). The determination of lead, tin and mercury compounds was done by species‐specific isotope dilution, derivatisation and GC–inductively coupled plasma MS (GC‐ICP‐MS) or by GC‐MS. The recovery and accuracy of the derivatisation were evaluated. The effect of pH and the relative quantity of derivatisation agent were studied.     

Synthesis, characterization, and catalytic properties of stable mesoporous molecular sieve MCM-41 prepared from zeolite mordenite

Mesoporous molecular sieves (denoted as M-MCM-41) with ordered hexagonal structure have been successfully synthesized from the assembly of precursors from preformed zeolite Mordenite with CTAB surfactant micelle in alkaline media. The samples were characterized by XRD, N₂ adsorption, IR and DTG. The materials exhibit highly hydrothermal stability, as compared with conventional MCM-41. Characterization results indicate that the mesoporous walls of M-MCM-41 contain the secondary building units similar to those in microporous crystal of zeolite Mordenite. In catalytic dealkylation of C10⁺ aromatic hydrocarbon, M-MCM-41 shows higher activities in comparison with Mordenite and MCM-41, which would be ascribed to the combination of advantages of both MCM-41 (large pores) and Mordenite (strong acidity). Furthermore, this synthesis strategy could be used as a new general method for the preparation of hydrothermally stable mesoporous aluminosilicate materials under alkaline conditions.     

Copper ferrite superparamagnetic nanoparticles as a heterogeneous catalyst for directed phenol/formamide coupling

The copper ferrite-catalyzed, directed coupling of ortho-arylated phenols and dialkylformamides in the presence of a peroxide oxidant is described. Acyclic and cyclic amides were compatible with the reaction conditions. The copper ferrite catalyst is heterogeneous since substantial leaching was not detected and re-use of the catalyst for 9 consecutive reactions proceeded without a significant decrease in yield. To the best of our knowledge, this transformation has not been previously performed under heterogeneous catalysis conditions.     

Dehydrogenation of ethylbenzene with CO2 over Cr-MCM-41 catalyst

M-MCM-41 catalysts (M: V, Cr, Fe, and Ga) prepared by direct hydrothermal synthesis (DHT) have been tested for dehydrogenation of ethylbenzene with CO₂. The synthesized materials were characterized by X-ray diffraction (XRD), N₂ adsorption (77 K), and diffuse reflectance UV–vis spectroscopic measurements. Cr-MCM-41 showed the highest activity among M-MCM-41 catalysts tested, resulting in the production of styrene with the conversion of 65% and the selectivity above 90%. The rate of styrene formation increased with increasing Cr loading up to 1.7 wt.%. It is suggested that Cr(VI)O₄ in tetrahedral coordination is formed as an active monochromate species and reduced to Cr(III)O₆ in octahedral coordination as a less active polychromate species during the reaction. Deactivated catalyst was regenerated by a treatment with gaseous oxygen or CO₂, during which redistribution as well as reoxidation of polymeric Cr(III)O₆ octahedra to monomeric Cr(VI)O₄ tetrahedra was observed. The rate of CO formation increased together with that of styrene formation, while the rate of H₂ formation decreased, with increasing partial pressure of CO₂. It was confirmed that reverse water-gas shift reaction took place over Cr-MCM-41 by a separate experiment. The rate of CO formation during the dehydrogenation of ethylbenzene with CO₂ over Cr-MCM-41 was well accounted for by assuming parallel occurrence of two reactions, i.e., direct oxidative dehydrogenation of ethylbenzene with CO₂ and simple dehydrogenation of ethylbenzene thermodynamically assisted by reverse water-gas shift reaction.     

铁改性的HMS分子筛催化苯酚羟基化反应合成二酚

邻苯二酚和对苯二酚是重要的精细化工中间体,在各个行业中具有广泛的应用。苯酚与过氧化氢反应合成苯二酚是一条反应条件温和、环境友好的合成路线,该合成路线的关键是催化剂的选择和反应条件的优化。本文以铁改性的HMS分子筛为催化剂,研究了金属负载量、催化剂使用量、反应温度、反应时间等因素对催化性能的影响,优化了反应条件。以水为溶剂,n(Fe)∶n(Si)=0.04,n(苯酚)∶n(H2O2)=2∶1,反应温度50℃,催化剂用量0.1g,反应4h,苯酚的转化率达45.5%,苯二酚选择性为94.9%。N2吸附-脱附结果表明,Fe/HMS具有良好的介孔结构,铁进入HMS材料的骨架中,并且催化剂具有良好的稳定性,循环使用后骨架保持完整。     

Epoxidation of cyclohexene on modified Ti-containing mesoporous MCM-41

Ti-MCM-41, B-Ti-MCM-41 and Ti-grafted MCM-41 were synthesized, characterized and studied in the epoxidation of cyclohexene. The synthetic methods and the effect of water in the oxidant are discussed.     

One-pot synthesis of phenol and cyclohexanone from cyclohexylbenzene catalyzed by N-hydroxyphthalimide (NHPI)

Synthesis of phenol and cyclohexanone in one pot was examined by means of the NHPI-catalyzed aerobic oxidation of cyclohexylbenzene. The aerobic oxidation of cyclohexylbenzene catalyzed by NHPI followed by treatment with sulfuric acid afforded phenol and cyclohexanone in good selectivities. Thus, the reaction of cyclohexylbenzene under atmospheric dioxygen (1 atm) by NHPI at 100 °C for 3 h followed by treatment with 0.3 M sulfuric acid at room temperature for 2 h resulted in phenol and cyclohexanone in 96 and 91% selectivity, respectively, at 25% conversion. This method was successfully extended to the one-pot synthesis of 4-hydroxyacetophenone and cyclohexanone.