Synthesis, characterization of bimetallic Sn-Zn-MCM41 and its catalytic performance in the hydroxylation of phenol

A series of Sn-Zn modified-MCM41 has been synthesized by direct hydrothermal method and characterized using ICP, XRD, TG/DTA, FT-IR, HRTEM and N_2-adsorption techniques. Catalytic performances of the obtained materials were evaluated in the hydroxylation of phenol with H₂O₂. Results indicated that all the samples exhibited typical hexagonal arrangement of mesoporous structure with high surface area and the heteroatoms were probably incorporated into the framework of MCM41. Catalytic tests revealed that the bimetallic incorporated materials were effective catalysts in the hydroxylation of phenol. The conversion of phenol could be reach to 56.8% for the catalysts with Sn: Zn: Si = 2.69: 4.57: 100 (molar ratio) under the optimized reaction conditions. Moreover, the materials containing Sn and Zn exhibited higher catalytic activity than monometallic Sn and Zn modified MCM41.     

铁铝交联黏土催化剂的制备及其苯直接羟基化的催化性能

通过直接向稀释的黏土悬浮液中加入Fe-Al交联剂制备了不同物质的量比的铁铝交联黏土催化剂。研究了该催化剂在苯/H2O2直接羟基化制备苯酚反应中的催化性能。结果表明,铁铝交联黏土催化剂在苯直接羟基化反应中具有良好的催化活性,苯酚收率最高可达4.9%,选择性可高达73.5%。运用XRD、FT-IR、TG-DSC、SEM等手段对铁铝交联黏土催化剂进行了表征。     

Influence of preparation parameters on characteristics of zirconia-pillared clay using ultrasonic technique and its catalytic performance in phenol hydroxylation reaction

Ultrasonication method was employed for preparation of zirconia-pillared montmorillonite (Zr-PILC) by using polyhydroxy zirconium cation. The influences of various preparation parameters such as pH, concentration of pillaring agent, aging period on physico-chemical properties of Zr-PILCs are reported. The characterization was done by using different characterizing tools such as powder X-ray diffraction (XRD), thermal analysis (TG/DTA), Fourier transform infrared spectroscopy (FTIR), X-ray photo-electron spectroscopy (XPS), X-ray fluorescence spectroscopy (XRF) and surface area measurements. Effective pillaring was obtained in the pH range 2.0–2.8 at reduced preparation time by using ultrasonication. Ultrasonication, especially at higher pH and concentration of pillaring agent with no aging after ultrasonic agitation of the clay slurry was found to increase zirconium content and specific BET surface area leaving no scope for remarkable increase in d001 spacing. The presence of -OH groups attached to Zr has been revealed by pyridine-adsorbed FITR, TG/DTA and XPS techniques. The acidic character, ease of accessibility and good dispersion of active sites in Zr-PILC were found to be controlling factors for the challenging activity in hydroxylation reaction of phenol. Probably, this first report on the use of Zr-PILC in hydroxylation of phenol and its preparation by employing ultrasonication technique may attract great attention in the catalysis area of academic and industrial importance.     

The role of acidity in the catalytic hydroxylation of phenol by hydrogen peroxide

The heterogeneous acid catalysis of the hydroxylation of phenol by hydrogen peroxide was investigated over protonic faujasites containing various amounts of aluminium or partially neutralized. Over strong acids, such as dealuminated protonic faujasites, dihydroxybenzenes result, mainly from an acid catalysed electrophilic aromatic substitution. Over weaker acids, an induction period is observed, the length of which is related to the strength of the acid sites. In that case, the initiation of the reaction occurs by the products of the former acid mechanism, and it is demonstrated using protonated and unprotonated electron transfer agents, that the subsequent autocatalysis involving a redox mechanism, also needs acid catalysis.     

Selective hydroxylation of phenol employing Cu–MCM-41 catalysts

We studied the oxidation reaction of phenol in aqueous and acetonitrile media under mild conditions, employing Cu-modified MCM-41 mesoporous catalysts. The stability of the catalysts under reaction conditions was confirmed by XRD, UV–VIS and FTIR techniques. Results obtained indicate that the selective oxidation of phenol with H₂O₂ by a radical substitution mechanism produces three main reaction products: catechol, hydroqinone and benzoquinone.     

Ti-MCM-41分子筛催化剂的合成、表征及催化性能

以正硅酸四甲酯为硅源,钛酸四异丙酯为钛源,在异丙醇和水的混合溶液中室温下合成了Ti-MCM-41介孔分子筛,采用TEM、N 2吸附-脱附、XRD、UV-Vis和Raman等研究了分子筛的结构特性。并以过氧化氢异丙苯为氧化剂,考察了硅烷化处理后的Ti-MCM-41分子筛催化剂在丙烯环氧化反应中的催化性能。结果表明,与骨架外六配位钛物种相比,骨架内四配位钛物种活化有机过氧化物的能力更强,速率更快;四配位钛物种是环氧丙烷生成的活性物种,而六配位钛物种的存在则会导致反应副产物的生成。合成时添加适量的异丁醇可有效促进钛物种进入分子筛骨架中,并增大比表面积和孔体积,进而改善Ti-MCM-41催化剂的丙烯环氧化催化性能。性能最佳的催化剂上过氧化氢异丙苯转化率可达94.7%,环氧丙烷选择性可达95.8%。     

Synthesis of Fe-MCM-48 and its catalytic performance in phenol hydroxylation

Highly ordered Fe-MCM-48 was synthesized by a mixed templation method under low molar ratio (0.17:1) of mixed surfactants to silica and characterized by XRD, ²⁹Si-MAS NMR, ESR, and UV-Visible. Its catalytic activity and selectivity was studied for phenol hydroxylation using H₂O₂ (30%). The substituting element (Fe³⁺) is partially incorporated into the framework position forming a new type of active site which raises the phenol conversion to 43.6% and the diphenol (the mixture of catechol (CAT) and hydroquinone (HQ)) selectivity to 97.7%.     

镧、钒取代MCM-41分子筛的结构表征及其在苯酚羟基化反应中的催化性能

采用水热法合成了双金属镧(La)和钒(V)取代MCM-41分子筛催化剂,使用X射线衍射、N2吸附、傅里叶变换红外光谱、紫外-可见漫反射光谱以及热重等表征技术研究了催化剂的结构。结果表明,该材料具有高度有序的二维六方结构,金属La和V以高度分散的四配位状态存在于分子筛的骨架中。在苯酚过氧化氢羟基化反应中La-V-MCM-41分子筛表现出比TS-1催化剂更好的催化活性和选择性,金属La和V协同作用,在提高H2O2有效利用率的同时,增加了目标产物苯二酚中对苯二酚的含量。La-V-MCM-41催化剂可以通过焙烧活化的方法进行再生使用。     

酸性中心对复合氧化物催化苯酚羟基化反应的影响

铁基复合氧化物催化苯酚羟基化反应具有明显的诱导期,适当引入酸性中心,在氧化还原活性位的共同存在下,可以迅速缩短羟基化反应的诱导期;酸性中心弱或没有采用酸改性的复合氧化物催化剂,对苯酚羟基化反应催化作用活性低,催化剂用量大,反应诱导期不稳定。乙酸、乙酸酐等有机弱酸可以直接加入羟基化反应体系。对复合氧化物催化剂进行后处理改性,引入适当的酸性中心,有助于提高催化剂的活性,缩短甚至消除羟基化反应诱导期,避免由于未反应过氧化氢的积累增加反应器运行的风险,提高过氧化氢有效利用率和目标产物选择性。将5.3g苯酚、0.051g催化剂、过氧化氢与苯酚的物质的量比为0.33,在65℃下,于10.6g溶剂水中反应,时间为30min,反应诱导期仅5min,苯酚转化率达21.2%,苯二酚选择性为92.9%,过氧化氢有效利用率为59.6%。分析了直接加入酸性中心和对复合氧化物催化剂进行酸改性所带来的问题,推测了苯酚羟基化反应的机理。     

Cu-HMS的合成和催化苯酚羟基化反应研究

分别以CuCl₂、CuAc₂和Cu(NH₃)⁺₄为铜源,正硅酸乙酯为硅源,十二胺为模板剂,在室温下合成了Cu-HMS系列介孔分子筛催化剂。XRD、FT-IR、孔容测定和元素分析结果表明,铜原子嵌入到介孔HMS骨架中将使HMS的晶胞发生扩张,孔容增大;使用Cu(NH₃)⁺₄合成的Cu-HMS-3样品其结晶有序度好、骨架铜含量高。在催化苯酚羟基化反应中,Cu-HMS-3催化剂显示出最佳的催化性能。在优化的反应条件下,可获得35%的苯酚转化率和90%以上的二酚选择性。     

Vanadium-containing ordered mesoporous silicas: Synthesis, characterization and catalytic activity in the hydroxylation of biphenyl

A series of vanadium-containing ordered mesoporous MCM-41 materials (V-OMS) have been synthesized by direct hydrothermal (V-MCM-41) and grafting (V/MCM-41) methods using hexadecyl trimethyl ammonium bromide (HDTMABr) as the structure-directing agent. The physico-chemical properties of the vanadium-containing materials were characterized in detail by ICP-OES, XRD, FT-IR, N₂ adsorption–desorption, DRUV-VIS, TPR, XPS and SEM techniques. The redox performances of the vanadium-modified mesoporous materials were tested in the hydroxylation of biphenyl using aqueous H₂O₂ (30 wt.%) as oxidant. For a better exploitation of the catalytic activity, the reaction parameters are optimized in terms of temperature, solvent, oxidant, etc. A comparison between the catalytic activity values of the vanadium-containing mesoporous materials prepared by the two routes shows that vanadium-substituted (V-MCM-41) materials had increased activity and improved selectivity for mono hydroxyl products in the hydroxylation reaction of biphenyl compared to the V/MCM-41 catalysts. The heterogenity of the catalysts was verified by a series of leaching studies. Both the catalysts enhance the leaching of active vanadia species during the reaction; among them, V/MCM-41 shows the least heterogenity.     

Synthesis, structural characterization and photocatalytic activity of Ti-MCM-41 mesoporous molecular sieves

This paper reports the applicability of hydrothermal synthesis in alkaline medium for preparation of Ti-containing mesoporous MCM-41 materials. The influence of different parameters was investigated, such as the Ti source, the molar ratio between Si and Ti and also the synthesis temperature. Structural analysis shows that the high specific surface area, large pore size and well ordered mesostructure, are partially retained in the titania containing materials. Modifying synthesis temperature, it was shown that MCM-41 isotherms are different for temperatures above or under 140°C. UV-VisDR spectroscopy was used to investigate the local environment of Ti sites. The obtained materials were evaluated for the photocatalytic degradation of Rhodamine 6G in aqueous medium. The best photocatalytic activity was found for the sample prepared at higher ageing temperature of 160°C, at which anatase particles were formed.     

Synthesis, characterization and catalytic application for wet oxidation of phenol of iron-containing clays

High-surface-area pillared clays (PILC) were prepared from naturally occurring montmorillonites by exchanging interlayer ions to polyoxocations containing (i) aluminum (Al₁₃-PILC), (ii) iron adsorpted onto Al₁₃-PILC, and (iii) iron and aluminum located within the same complex (Fe_0.8Al_12.2-PILC). The obtained Fe_0.8Al_12.2-PILCs were characterized by DR–UV–vis and IR spectroscopy, XRD, ESR, scanning electron microscopy and low temperature N₂ adsorption measurements. Important factors affecting catalyst activity and phenol removal efficiencies have been studied, i.e. the effect of pH, temperature, catalyst concentration and stability of the catalyst.     

ZrO2/Ti-MCM-41的制备、表征及催化裂解聚丙烯反应的性能

采用水热合成法制备了中孔分子筛ZrO2/Ti-MCM-41,通过XRD、N2吸附-脱附、FT-IR、UV-Vis对其进行表征,表明其具有中孔结构,并且随着ZrO2含量的增加,ZrO2/Ti-MCM-41孔道的长程有序性和结晶度有所减弱,直至失去中孔结构。将其应用于聚丙烯(PP)的催化裂解反应,通过考察硅钛比、负载量、反应温度、催化剂用量和反应时间,对ZrO2/Ti-MCM-41催化裂解PP反应的规律进行了研究。结果表明,n(Si):n(Ti)=40,ZrO2负载质量分数为18%的ZrO2/Ti-MCM-41,在反应温度400℃,m(ZrO2/Ti-MCM-41):m(PP)=0.02,反应时间30 min的条件下,PP的转化率可达91.2%,液体产物的收率为83.6%,该结果优于热裂解及传统的HZSM-5小孔分子筛催化剂的催化裂解结果。     

无机物负载体的制备和表征及其催化苯酚羟基化的研究

研究了低硅铝比沸石分子筛及天然矿土硅铝酸盐负载无机盐或氧化物为催化剂,催化氧化苯酚制取邻、对位二元酚。用化学常量法分析了负载离子的含量,采用XRD、IR、DRS、Mossbauer谱等手段,对催化剂进行表征。研究了不同金属离子无机盐的各种载体催化剂的催化活性,证明了热稳定性差的沸石及矿土负载改性为六配位非骨架杂原子的无孔道致密相,对苯酚羟化反应有较好的催化活性,n沸石1作催化剂,溶剂用水,苯酚与H2O2摩尔比为3：1,pH值为1．5(Fe改性),4(Cu改性),温度为60℃(Fe改性)、80℃(Cu改性),时间为1h,催化剂的量为苯酚的1／10,催化剂有一定再生能力,重复3次使用效果较好。     

阳离子单体及其聚合物的合成表征

合成了阳离子单体甲基丙烯酰氧乙基二甲基丁基溴化铵(DMB),将DMB与丙烯酰胺(AM)共聚制备了阳离子聚丙烯酰胺,并用IR,NMR对其结构进行了表征。     

Ni and Mo interaction with Al-containing MCM-41 support and its effect on the catalytic behavior in DBT hydrodesulfurization

A series of Mo and NiMo catalysts supported on Al-containing MCM-41 was prepared and characterized by N₂ physisorption, XRD, ammonia TPD, temperature programmed reduction (TPR), UV-Vis diffuse reflectance spectroscopy (DRS) and ²⁷Al MAS-NMR. It was shown that the incorporation of Al atoms into the siliceous MCM-41 framework causes a deterioration of the textural characteristics and some loss in the periodicity of the MCM-41 pore structure. However, the acidity of the Al-containing MCM-41 is substantially higher. The dispersion of Mo and Ni oxidic species increases with the incorporation of aluminum in the MCM-41 support due to the strong interaction of Mo and Ni oxidic species with aluminum atoms of the support. However, the strong interaction of metal species with the Al-containing MCM-41 supports, up to the formation of Al₂(MoO₄)₃ in the case of unpromoted Mo catalysts, produces an increase in the proportion of Ni and Mo species difficult to reduce. When Ni and Mo are impregnated simultaneously the formation of Al₂(MoO₄)₃ is prevented because of the competitive interaction of both, Ni and Mo species, with Al atoms of the support. For both, Mo and NiMo catalysts, maximum catalytic activity in dibenzothiophene (DBT) hydrodesulfurization is observed for the catalysts supported on Al-MCM-41 with SiO₂/Al₂O₃ molar ratio of 30. When Al-containing MCM-41 is used as a support for NiMo catalyst, some cracking of the main reaction products (biphenyl (BiP), cyclohexylbenzene (CHB) and dicyclohexyl (DCH)) is observed.     

双酚A改性甲阶酚醛树脂的合成和表征

利用双酚A、苯酚、甲醛水溶液为原料,在KOH的催化下,合成了一种含有羟甲基的双酚A改性甲阶酚醛树脂,研究了反应温度、反应物配比、催化剂用量、反应时间对合成的影响,并用红外光谱分析了产品的结构。结果表明,在反应温度为80℃,反应时间为3 h条件下,各反应物物质的量比的适宜范围:n(甲醛):n(苯酚)为(3.0～3.5):1,n(氢氧化钾):n(苯酚)为(0.085～0.15):1;n(双酚A):n(苯酚)为(0.1～0.35):1。     

PO_4~(3-)/Si-MCM-41介孔分子筛合成与表征

采用十六烷基三甲基溴化铵作为模板剂,正硅酸乙酯为硅源,用水热晶化法在乙二胺为碱性介质中合成了Si-MCM-41介孔分子筛,并用磷酸浸渍法制备PO3-4/Si-MCM-41。通过氮气吸附-脱附、红外光谱、Hammett指示剂胺滴定等方法对所合成样品进行了表征。结果表明,合成的分子筛具有典型的介孔结构特征,孔径分布较窄,具有较大的比表面积和较强的酸性。     

Mo-MCM-41催化环戊烯烯丙型氧化的研究

研究了负载钼MCM-41和MCM-48分子筛对环戊烯烯丙型氧化的催化性能。两种介孔材料中,2-环戊烯-1-酮均为主要产物,副产物是少量的环戊烯氧化物和1,2-环戊二醇。实验显示钼MCM-48由于含钼量较高,表现出比钼MCM-41更高的反应活性,使用极性溶剂(如N,N-二甲基甲酰胺和甲醇)2-环戊烯-1-酮选择性降低,极性溶剂诱发双键氧化,生成较多的环戊烯氧化物。钼基固体催化剂,MCM-41和MCM-48再循环使用,对2-环戊烯-1-酮的选择性几乎没有改变。