Hβ沸石修饰的复合氧化物对苯酚羟基化反应的催化作用

采用不同硅铝比的Hβ沸石对铁基复合金属氧化物催化剂进行了修饰,发现复合氧化物催化体系中掺入适量具有特定结构的Hβ沸石,可以提高催化剂的活性,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。但过多的Hβ沸石导致苯酚和苯二酚缩合生成不溶于水的焦油,降低了羟基化反应的目标产物选择性。比较合适的修饰用Hβ沸石包括Hβ-80、Hβ-63和Hβ-48。比较好的Hβ-80沸石掺入质量分数为7%,以7% Hβ沸石修饰的Fe-Cu-Sn-Zn-O/γ-Al2O3复合氧化物作催化剂,反应温度65 ℃、反应时间30 min、苯酚5.3 g、溶剂水10.0 g、m(苯酚)∶m(催化剂)=294、n(过氧化氢)∶n(苯酚)=0.33时,反应诱导期不到1 min,苯酚转化率22.3%,苯二酚选择性91.9%,过氧化氢有效利用率62.1%。     

一种高性能的苯酚羟基化用复合氧化物催化剂

用Hβ沸石对复合氧化物进行修饰和改性,制得一种高性能苯酚羟基化用复合氧化物催化剂Fe Hβ80〔w(Hβ) =7%〕。以Fe Hβ80做催化剂,对羟基化反应工艺条件进行了优化,优化的反应工艺条件为:反应温度65~70℃,反应时间0 25~0 5h,m(苯酚) /m(催化剂) =294~883,n(苯酚) /n(H2O2 ) =3 00~5 78,m(苯酚) /m(水) =0 43~0 91。以Fe Hβ80作催化剂,去离子水为溶剂,反应温度65℃,反应时间30min,苯酚5 3g,m(苯酚) /m(催化剂) =294,n(苯酚) /n(H2O2 ) =3 00,溶剂水10 0g,反应结果表明,羟基化反应诱导期不到1min,苯酚转化率22 3%,苯二酚选择性91 9%,过氧化氢有效利用率62 1%。与Fe Cu Sn Zn O/γAl2O3、Fe Mg O/γAl2O3 和TS分子筛等典型苯酚羟基化用催化剂相比较,由于Hβ沸石能为复合氧化物催化剂提供合适的酸性中心,从而缩短了苯酚羟基化反应诱导期,提高了催化活性和目标产物选择性,降低了过氧化氢在反应器中积累所带来的风险。Fe Hβ80催化剂用量仅为TS分子筛的1 /29 4(质量比), 但羟基化反应诱导期仅1min(TS分子筛为120min),证明Fe Hβ80是一种高性能的苯酚羟基化用催化剂。     

苯酚羟基化反应催化剂研究进展

对近年来苯酚双氧水羟基化反应的催化剂进行了综述。目前研制开发的性能优良的催化剂主要有:复合金属氧化物、杂原子取代的分子筛及杂多酸盐等,详细介绍了这些催化剂的性能及特点。     

苯酚双氧水羟基化反应催化剂研究进展

综述了双氧水氧化苯酚制备苯二酚所用催化剂研究的近期进展。目前研制开发的新颖、性能优良的催化剂有：杂原子分子筛,复合金属氧化物及其负载型催化剂和金属络合物及其负载型催化剂等３种。讨论了它们的制备、性能和应用前景。     

无机物负载催化苯酚羟基化反应研究

选用成本低、热稳定性差的沸石分子筛,用浸渍法负载金属组份,制成催化剂,用于催化苯酚差基化,深入研究了基催化反应条件,得到了较好效果。     

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。     

含铁催化剂催化苯直接羟基化制备苯酚的研究进展

催化苯直接羟基化是开发绿色苯酚生产新技术的高原子经济性的挑战性课题,但该工艺存在芳香C-H键难活化、产物酚的选择性较低等问题,其中高效催化剂的研制是核心问题之一。根据含铁催化剂独特的化学结构和催化性能,本文从配合物均相催化剂、仿生催化剂、负载型非均相催化剂等方面综述了含铁催化剂催化苯直接羟基化制备苯酚的研究进展,并着重介绍了Fenton体系和仿生催化体系的反应机理。分析表明,以氧化物及天然矿物作为载体的含铁催化剂合成简单,活性高,有较大的研究及工业开发价值。此外,研究催化机理对设计合成高效苯羟基化的催化剂具有指导意义。     

苯和苯酚直接催化羟基化反应研究新进展

叙述了苯直接催化羟基化反应制苯酚、苯酚直接催化羟基化反应制苯二酚的研究 开发的最新进展,介绍了不同氧化剂的试验情况,评述了各类多相催化剂的研究开发成 果。H2O2作为苯及苯酚羟基化反应的氧化剂,具有反应条件温和,产物选择性高,对环境 无害等特点,成为工业催化领域中由苯直接羟基化反应制苯酚、苯酚直接羟基化反应制 苯二酚的主导氧化剂,开发高效的多相催化剂是该绿色合成技术的技术关键。     

V-Cu氧化物催化碳酸二甲酯与苯酚酯交换反应

研究了一系列钒-金属复合氧化物对碳酸二甲酯(DMC)和苯酚酯交换合成碳酸二苯酯(DPC)的催化性能,实验结果表明,钒-铜复合氧化物是较好的酯交换合成DPC的催化剂。考察了V/Cu摩尔比,催化剂用量,DMC用量和反应时间对酯交换反应的影响,得到较佳的反应条件： n(V):n(Cu) = 4:1,苯酚用量0.16 mol,V-Cu复合氧化物催化剂的用量为苯酚用量的3.1%（质量比）, n(DMC) : n(苯酚) = 1.5 :1,反应时间9～15 h。在此条件下反应9 h,苯酚的转化率为41.9%,甲基苯基碳酸酯(MPC)及DPC的总收率为40.3%。催化剂重复使用4次后苯酚转化率从41.9%降到29.1%,多次重复使用后的催化剂在空气氛中焙烧即可再生,再生催化剂的催化性能几乎和新鲜催化剂相当,苯酚转化率达到39.8%。     

过氧化氢氧化苯制苯酚的催化剂研究进展

综述了过氧化氢直接氧化苯制苯酚过程中相关催化剂的研究进展,重点介绍了含钛、钒、铁、铜的催化剂,同时给出了各种催化剂所达到的收率和选择性及其工业化前景。     

Comparison of catalytic decomposition of hydrogen peroxide and catalytic degradation of phenol by immobilized iron oxides

Immobilized iron oxides on silica matrixes in fluidized bed reactors, including SiG1, SiG2, C1, and the commercial catalyst FeOOH, were used in the catalytic decomposition of H₂O₂ and the catalytic degradation of phenol. They were characterized using XRD, SEM, N₂-sorption, and elucidation of the kinetics of dissolved iron by oxalic acid in dark surroundings. XRD patterns reveal that SiG1, SiG2, and C1 exhibit amorphous structures, and FeOOH exhibits the poor crystallinity of goethite. The SEM images reveal that the surfaces of all the iron oxides are smooth and that the iron oxides are aggregated by the iron oxide floc. The N₂-sorption isotherm indicates that SiG1 and SiG2 are non-porous materials, and that C1 and FeOOH are typical type II and typical type IV materials, respectively. A kinetic model for iron dissolved by oxalic acid is established. The order of apparent first-order dissolution rate constants (k_c) is SiG1 > SiG2 > FeOOH  C1. The immobilized iron oxides, SiG1 and SiG2, are weakly bonded to the support (silica sand) in the presence of oxalic acid. The decomposition of H₂O₂ follows pseudo-first-order kinetics. The number of active sites for the decomposition of H₂O₂ is similar among all iron oxides at a particular k_app (1.8 × 10⁻³ min⁻¹). There are no interactions between phenol and iron oxides in the absence of hydrogen peroxide at pH 4. SiG1 and SiG2 exhibit much higher catalytic activities in phenol degradation than either C1 or FeOOH. The reactivity of iron oxides in catalyzing the phenol degradation by H₂O₂ relates to the tendency of iron to be dissolved by oxalic acid. The intermediates of phenol degradation, such as catechol and oxalic acid, promote the dissolution of iron from SiG1 and SiG2 by reductive and non-reductive pathways and lower the pH values. The catalyses of SiG1 and SiG2 involve heterogeneous and homogeneous reactions.     

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.     

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.     

Effects of pore structure of post-treated TS-1 on phenol hydroxylation

The present study reports the effects of crystal size of TS-1 (micrometer sized umTS1 and nanometer sized nmTS1) and the post-treatment (TPAOH and NaOH treatment) on the porous structure and the catalytic performances of TS-1 in phenol hydroxylation. TPAOH post-treatment generates hollow crystal and increases the surface area of umTS1 without changing its pore structure. In contrast, NaOH treatment selectively dissolves framework silica to form mesopore and modify microporous structure through which hierarchical material is constructed with agglomerated crystals. The umTS1 sample gives a much lower conversion and lower selectivity of dihydroxylbenzenes (DHB) than the nmTS1 sample. Its activity can be greatly improved by TPAOH post-treatment exhibiting a comparable catalytic activity and DHB selectivity with the nmTS1 sample. Furthermore, successive post-treatment by TPAOH following with NaOH can generate micropores larger than the pore size of TS-1. The higher titanium content and faster diffusivity associated with the successive post-treatment significantly improve the catalytic performance of TS-1.     

Photocatalytic degradation of phenol on MWNT and titania composite catalysts prepared by a modified sol–gel method

Multi-walled carbon nanotubes (MWNT) and nanocrystalline titania composite catalysts were prepared by a modified sol–gel method. Thermogravimetric analysis, N₂ adsorption–desorption isotherm measurements, powder X-ray diffraction, scanning electron microscopy, energy dispersive X-ray analysis, transmission electron microscopy and UV–vis spectra were carried out to characterize the composite catalysts with different MWNT contents. The results suggest that the presence of MWNT embedding in the composite catalysts matrix prevents TiO₂ particle agglomeration. Additionally, a correlation exists between the MWNT content and the changes in the UV–vis absorption properties. The photocatalytic degradation of phenol was chosen as a model reaction to evaluate the photocatalytic activities of the composite catalysts. An optimum of the synergetic effect was found for a weight ratio MWNT/TiO₂ equal to 20%. The effects induced by MWNT on the composite catalysts may be explained in terms of a strong interphase interaction between MWNT and TiO₂ in the composite catalysts.