Salen-Mn(Ⅲ)和Salen-Mo(Ⅳ)配合物在介孔硅胶上接枝及烯烃环氧化催化性能

通过肽键作用将Salen型金属配合物接枝到介孔硅胶孔道中生成固相催化剂,采用红外光谱、热重分析和元素分析等对制备的固相催化剂进行表征,结果证实,Salen型金属配合物成功接枝到介孔硅胶载体上。以环辛烯和环己烯为反应底物,叔丁基过氧化氢和过氧化氢为氧化剂,比较均相Salen型催化剂和多相Salen型催化剂的催化活性。制备的均相Salen型催化剂和利用肽键键合制备的固相催化剂均具有一定的催化性能,Mo-Salen催化活性更高,是因为叔丁基过氧化氢在Mo-Salen存在下易分解。固相催化剂活性≤75℃时稳定,在氧化剂叔丁基过氧化氢和过氧化氢作用下具有较好的稳定性能。重复实验中,金属离子流失量很小,催化活性和TOF值未降低,表明利用肽键制备的固相催化剂催化活性稳定,为固相催化剂的制备开辟新思路。     

Aluminum- and calcium-incorporated MCM-41-type silica as supports for the immobilization of titanium(IV) isopropoxide in ring-opening polymerization of l-lactide and ε-caprolactone

Aluminum- and calcium-incorporated MCM-41-type silica with various Al/Si and Ca/Si ratios were evaluated as catalytic supports for ring-opening polymerization (ROP) of l-lactide and ε-caprolactone. The catalytic centers were generated by grafting titanium(IV) isopropoxide onto the support. All prepared heterogeneous catalysts better restrained the ROP of lactide than the homogeneous analog, titanium(IV) isopropoxide. Compared to siliceous MCM-41, the incorporation of aluminum or calcium in MCM-41 framework improved the molecular weight of the polymers although it lessened the polymerization rate. The more acidic Al-MCM-41 support appeared to be more favorable than the more basic Ca-MCM-41 support for the ROP reactions.     

A new environmentally friendly method for the production of 2,3,5-trimethyl-p-benzoquinone

A new environmentally friendly method for the production of 2,3,5-trimethyl-1,4-benzoquinone (TMBQ, Vitamin E precursor) based on the oxidation of 2,3,6-trimethylphenol (TMP) with aqueous H₂O₂ over various Ti-containing mesoporous silicate materials is reported. Both well-organized Ti-containing mesoporous mesophase silicate (Ti-MMM), having hexagonal arrangement of uniform mesopores, and amorphous TiO₂–SiO₂ mixed oxides (aerogels and xerogels) produced TMBQ with good to high yield. All the materials studied have been proved to operate as truly heterogeneous catalysts. No titanium leaching occurred from the solid matrixes during the oxidation process. Titanium dispersion and its accessibility were found to be crucial factors determining the catalytic properties. For samples with similar titanium loading, both the catalytic activity and TMBQ yield appeared to fall in the order TiO₂–SiO₂ aerogel>Ti-MMM>TiO₂–SiO₂ xerogel and correlate with average mesopore diameter and mesopore volume. The best results (96–98% selectivity to TMBQ at 99–100% TMP conversion) were obtained with TiO₂–SiO₂ aerogels, containing 1.7–6.5 wt.% Ti.     

Preparation of silica-immobilized titanium-containing silsesquioxane catalysts and activity for the epoxidation of alkenes

Silsesquioxanes containing tetrapodal titanium species and alkenylsilyl groups were immobilized onto dimethylsilyl-functionalized silica having mesopores by chemical tethering via hydrosilylative reaction in the presence of a Pt catalyst. The immobilized catalysts showed higher activity than their corresponding homogeneous catalyst towards the epoxidation of cyclooctene by tert-butylhydroperoxide, probably because of the improvement of the micro-environment around the titanium center. The reaction was found to be truly heterogeneous, since no further reaction proceeded after the separation of the catalyst by filtration. These catalysts also showed excellent catalytic activity for the epoxidation using hydrogen peroxide as an oxidant, while the parent homogeneous catalysts did not show any activity at all.     

介孔氧化硅固载Yb(OTf)3的制备及催化葡萄糖生产乳酸

采用溶剂法和焙烧法制备了SBA-15和MCM-41两类介孔氧化硅,并以此为载体制备固载型三氟甲基磺酸镱(Yb(OTf)₃)催化剂。通过小角X射线衍射(SAXD)、氮气吸附/脱附、²⁹Si固体核磁共振光谱(NMR)、透射电子显微镜(TEM)及热重分析(TG)等方法对载体及催化剂进行表征,研究其在葡萄糖制备乳酸反应中的催化性能。结果表明：溶剂法制备的氧化硅表面羟基含量比焙烧法高,负载的磺酸基团和三氟甲基磺酸镱都更多,催化活性更高;SBA-15的平均孔径比MCM-41的大3 nm左右,这使得SBA-15具有更好的传质性能以及Yb(OTf)₂-SBA-15具有更好的催化性能。以Yb(OTf)₂-SBA-15-S为催化剂,在2 MPa N₂压力、190 ℃下反应60 min,乳酸的收率达到42.35%。     

SBA-15固载酸性离子液体催化酯化反应性能

为了减少离子液体用量及解决催化剂分离问题,采用键合法制备了以SBA-15为载体的固载化离子液体催化剂[C₃SO₃HCP]HSO₄/SBA-15,通过FT-IR、TG、XRD、BET和TEM分析了催化剂的结构和稳定性。并将其应用于催化丁二酸酐和乙醇的酯化反应。结果表明:[C₃SO₃HCP]HSO₄被成功固定在SBA-15上,且具有较高的热稳定性和催化活性,克服了非均相催化剂活性不高与均相催化剂难以分离的不足。在催化剂用量为反应物总质量的5%、n(C₄H₄O₃):n(C₂H₅OH)=1:3,反应温度80℃;反应时间4 h、带水剂用量为反应物总质量的30%的条件下,酯收率达93.7%,且该催化剂循环使用8次后,仍具有较高的催化活性。此外,还考察了以[C₃SO₃HCP]HSO₄/SBA-15为催化剂催化合成系列酯也获得了较高的酯收率,且易于与产物酯分离。     

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.     

Reactive separation of dilute ethylene by hydroformylation using slurried rhodium catalysts on phosphinated resins and silica

A series of slurried rhodium catalysts on phosphinated resins and silica were tested for the reactive separation of dilute ethylene by hydroformylation to propanal. The amount of rhodium leaching was determined for most of the systems investigated. Leaching ranged from <2 to 11% for catalytic runs for resin supported systems, but was found to be much more significant for the phosphinated silica system studied, 19%. The level of rhodium leaching correlated well with the loss in rate of propanal formation between repeated experiments using recycled catalysts for the resin based systems, but the loss in rate was much more significant for the silica based system. This level of leaching is very high for a commercial process for basic chemical synthesis, for which leaching is typically at the ppb level. Rates of propanal formation for resin supported catalyst systems correlated well with the cone angle of the free phosphine, with rates as high as 0.35 mol/l/h. However, while smaller cone angles were found to be directly proportional to rate, supported systems were less active than homogeneous counterparts.     

Synthesis of dimethyl carbonate from propylene carbonate and methanol using CaO–ZrO2 solid solutions as highly stable catalysts

CaO–ZrO₂ catalysts were prepared by coprecipitation and their catalytic performances were evaluated in the synthesis of dimethyl carbonate from propylene carbonate and methanol. The characterization by XRD, N₂ adsorption, XPS and CO₂–TPD indicated that Ca²⁺ ion substituted for Zr⁴⁺ ions in the host lattice to form homogeneous CaO–ZrO₂ solid solution when Ca/(Ca + Zr) ratio changed from 0.1 to 0.3, and CaO segregated at grain boundaries with Ca/(Ca + Zr) ratio from 0.4 to 0.5. As a result, the catalysts showed different activity and stability towards the transesterification of propylene carbonate and methanol into dimethyl carbonate. The activity of catalysts was improved with increase in Ca content, whereas high stability was shown with Ca/(Ca + Zr) ratio below 0.3. The formation of homogeneous CaO–ZrO₂ solid solution was responsible for the stability of catalysts.     

Catalytic decomposition of methylene chloride by sulfated oxide catalysts

Catalytic decomposition of methylene chloride in air with a concentration of 959 ppm and temperature ranges from 160 to 275°C were studied. Three different sulfated oxide catalysts, TiO₂(SO₄), ZrO₂(SO₄), CeO₂(SO₄) were prepared and their activities and selectivities were measured. The catalytic activity decreased in the order: TiO₂(SO₄) > ZrO₂(SO₄) > CeO₂(SO₄). Complete catalytic decomposition of methylene chloride was achieved at low temperature (275°C) over a sulfated titanium dioxide catalyst. The oxygen adsorption (pick-up) and the acidity values of three catalysts showed the same trend as their activities. The presence of water (2% in volume) in the feed stream reduced the activities remarkably and raised the activation energies for the decomposition reaction. The selectivities among all three catalysts were similar, with HCl, CO and CO₂ being the products. A bifunctional catalyst comprising sulfated titanium dioxide with copper oxide was developed to improve the selectivity of catalytic oxidation of methylene chloride towards carbon dioxide.     

Acylation of sulfonamines using silica grafted 1-butyl-3-(3-triethoxysilylpropyl)-4,5-dihydroimidazolium ionic liquids as catalysts

Heterogeneous immobilized ionic liquid catalysts were prepared via grafting of 1,3-dimethyl-3-(3-triethoxysilylpropyl)-imidazolium tetrafluoroborate or bis{(trifluoromethyl)sulfonyl} imide ([NTf₂]⁻) on silica supports with different surfaces and pore size. In addition to the adsorption–desorption isotherms of nitrogen at −196 °C, the catalysts were characterized by TG-DTA, XPS, DRIFTS, DR-UV–vis, NMR, and XRD techniques. The catalytic behavior was checked in the acylation of three different sulfonamines: benzenesulfonamine, p-nitrobenzenesulfonamine, and p-methoxybenzene-sulfonamine with acetic acid, acetic anhydride and maleic anhydride. These tests confirmed the acid Lewis properties of these catalysts.     

Catalytic wall reactor: Catalytic coatings of stainless steel by VOx/TiO2 and Co/SiO2 catalysts

Catalytic wall (structured) reactors and structured supports are suitable to study the catalytic properties of nanosized materials. The coating of metallic (aluminum and stainless steel) plates by thin layers of active phase is presented in two cases, VO_x/TiO₂ and Co/SiO₂, catalysts used in the oxidative dehydrogenation (ODH) of propane and in Fischer–Tropsch synthesis (FTS) of clean fuels, respectively. The preparation of coated plates and their characterisation by various methods of physicochemical analysis are described. Both chemical and physical methods were used for coating. VO_x/TiO₂ layers were obtained by grafting of Ti (on Al or stainless-steel plates) and V (on TiO₂) alkoxides and use of sol–gel media or suspension. A silica primer was deposited (on stainless-steel plate) by plasma-assisted chemical vapour deposition (PACVD) onto which Co oxide and silica were coprecipitated from sol–gel. The catalytic experiments in the respective reactions were carried out in special plate reactors and compared with those of catalytic powders. The study shows that the coating of a metallic substrate by a catalyst is not straightforward and requires specific studies dealing with both chemistry (chemical affinity between substrate and catalytic layers) and catalytic engineering (catalytic performance in taylor-made reactors).     

助剂二氧化硅对CO2加氢制备甲醇CuO-ZnO-Al2O3-ZrO2催化剂性能的影响

采用共沉淀法制备了一系列CuO-ZnO-Al₂O₃-ZrO₂(CZAZ)催化剂,用于二氧化碳加氢合成甲醇。通过加入少量的助剂二氧化硅得到了一系列CZAZ/SiO₂改性催化剂。采用XRD、BET、H₂-TPR、NH₃-TPD以及CO₂-TPD等技术进行表征,研究了助剂二氧化硅含量对催化剂的物理化学性质以及组织结构的影响。结果表明,助剂二氧化硅的含量对催化剂的组织结构具有较大的影响。同时评价了该组催化剂参与二氧化碳加氢合成甲醇反应的催化性能。测试结果表明,采用助剂二氧化硅质量分数为4%的改性催化剂,表现出较为优良的催化活性。助剂二氧化硅促进了活性组分氧化铜的分散,并且经过二氧化硅改性的CZAZ催化剂具有更大的比表面积,这些因素都对该催化剂在二氧化碳加氢合成甲醇方面的良好表现起到重要作用。     

Recovery and Recycling of Ti Supported Bimodal Mesoporous Catalysts Prepared via Ship-in-a-bottle Method in the Epoxidation of Cyclohexene

Ti/BMMs (Ti supported bimodal mesoporous silica) catalysts have been prepared via self-assembly route com-bined with ship-in-a-bottle method. The recovery and recycling performances of Ti/BMMs were inv...     

硅羟基对二氧化硅固载有机锡酯交换催化性能的影响

采用新方法制备了二氧化硅固载有机锡。以无机SnCl₄为锡源,在合成有机锡的同时制备有机锡硅烷试剂,再将其固载到二氧化硅上,用于碳酸二甲酯与苯酚酯交换合成碳酸二苯酯的反应。通过不同的制备方法和处理方法,制得不同硅羟基含量的二氧化硅载体;研究硅羟基对锡固载量及固载有机锡催化性能的影响。TG与ICP表征显示,锡固载量与二氧化硅载体的硅羟基含量正相关。²⁹Si MAS NMR表征发现,制备的固载有机锡中含有较多的T²和T³物种,利于有机锡的稳定固载。二氧化硅硅羟基含量越高,催化剂的锡固载量越高,活性越好。介孔二氧化硅为载体制备的Sn-MSiO₂表现出最好的催化活性：用量1.0 g,在150～180℃反应9 h,苯酚转化率达50.4%,酯交换选择性高于99.9%;用0.5 g考察重复使用性能,重复使用5次,苯酚转化率由41.2%降低到35.0%。锡流失是活性下降的主要原因。     

One Step Preparation of Sulfonated Solid Catalyst and Its Effect in Esterification Reaction

A carbon-based sulfonated catalyst was prepared by direct sulfonation and carbonization （in moderate conditions：200 ＆#176;C, 12 h） of red liquor solids, a by-product of paper-making process. The prepared sulfonated cata-lyst （SC） had aromatic structure, composed of carbon enriched inner core, and oxygen-containing （SO3H, COOH, OH） groups enriched surface. The SO3H, COOH, OH groups amounted to 0.74 mmol·g^-1, 0.78 mmol·g^-1, 2.18 mmol·g^-1, respectively. The fresh SC showed much higher catalytic activity than that of the traditional solid acid catalysts （strong^-acid 732 cation exchange resin, hydrogen type zeolite socony mobile-five （HZSM-5）, sulfated zir-conia） in esterification of oleic acid. SC was deactivated during the reactions, through the mechanisms of leaching of sulfonated species and formation of sulfonate esters. Two regeneration methods were developed, and the catalytic activity can be mostly regenerated by regeneration Method 1 and be fully regenerated by regeneration Method 2, respectively.     

Synthesis, characterization and catalytic properties of NiMo/Al2O3–MCM-41 catalyst for dibenzothiophene hydrodesulfurization

Ni–Mo/Al₂O₃–MCM-41 supported catalysts have been investigated for modification of MCM-41 by using sol–gel alumina incorporation method. Different catalysts were synthesized with variation of Si/Al molar ratios of 10, 50, 100 and 200. High specific surface area ordered meso-porous solid (MCM-41) was synthesized by using organic template method. In order to modify the low acidity of silica solid, the surface of MCM-41 was modified by incorporation of alumina. The surface acidity of solids modified significantly with variation of alumina content in the supports. The sol–gel method of alumina incorporation was used, which does not modify extensively the pore characteristics of MCM-41 material during the preparation of Al₂O₃–MCM-41. The X-ray diffraction intensities indicated that alumina as well as MCM-41 were present in the synthesized supports. Additionally, the hydrothermal stability of the Al₂O₃–MCM-41 materials was maintained up to 873 K using sever conditions like 100% water vapor stream. The catalytic activity of the catalysts was tested in the hydrodesulfurization (HDS) of dibenzothiophene (DBT). Selectivity was oriented mainly to the production of biphenyl (BP) and for high Si/Al ratios toward cyclohexylbenzene (CHB) and showed a higher conversion and better selectivity to hydrogenation (cyclohexylbenzene).     

Catalytic wet oxidation of p-coumaric acid: Partial oxidation intermediates, reaction pathways and catalyst leaching

The catalytic oxidation of p-coumaric acid, a compound representative of the polyphenolic fraction typically found in olive processing and wine-distillery wastewaters, has been investigated using various homogeneous and heterogeneous catalysts. Experiments have been performed with homogeneous Fe²⁺, Cu²⁺, Zn²⁺ and Co²⁺ ions at pH = 1, and with metal oxide catalysts in suspension at pH 3.5, 7 and 12. Additional uncatalyzed experiments have been performed and the results are compared to those of the catalyzed runs. The temperature was 403 K and the oxygen partial pressure was 2.8 MPa in all runs. The distribution of the reaction intermediates was determined, using HPLC and GCMS as the main analytical techniques, and reaction pathways are speculated. It was found that the use of catalysts could increase the rate of destruction of p-coumaric acid compared to the uncatalyzed reaction, while the distribution of the intermediate compounds was strongly dependent on the pH of the solution. A CuO·ZnOAl₂O₃ heterogeneous catalyst was found to be effective for the oxidation of p-coumaric acid although leaching of dissolved metals to the solution was found to occur. The stability of the heterogeneous catalysts was investigated by measuring the extent of metal leaching into the solution. The results are discussed with respect to the impact of various conditions (catalyst, pH) on the oxidation of p-coumaric acid and compared to those of the uncatalyzed reaction, studied in previous work.     

生物炭基催化剂制备对其催化降解Ni-EDTA性能影响

以胶原蛋白、木质素和硝酸铜为原料,采用共混热解法制备新型生物炭基铜系催化剂,通过多种表征手段考察制备方法和参数对催化湿式过氧化氢氧化（CWPO）处理Ni-EDTA模拟废液效果的影响,并阐述氧化降解过程中生物炭基铜系催化剂的失活机制。结果表明,相比溶液浸渍法,共混热解法有利于提高催化剂的催化活性,控制活性组分的均质分布和溶出释放,表现为Ni和TOC去除率分别增加13.05%和16.63%,Cu²⁺溶出量降低93.54%;在焙烧温度为800℃,Cu掺量为10%,胶原蛋白与木质素质量比例为1：3条件下,1000 mg·L^-1 Ni-EDTA模拟废液经60 min催化氧化后Ni和TOC去除率分别达到65.41%和34.85%,Cu²⁺溶出量仅为1.7 mg·L^-1。氧化降解过程中羧酸类中间降解产物的形成、活性组分反应性溶出和价态转变是致使催化剂失活的主要原因。     

Well-defined group IV supported catalysts: An efficient way to increase activities in the deperoxidation of cyclohexyl hydroperoxide with environmentally systems

Silica-supported (SiO)₃MOR (M=Ti, Zr, Hf; R=H, ^tBu) organometallic complexes of group 4, uniform in composition and in distribution, were synthesized via a molecular engineering approach of the construction of active sites. These catalysts were fully characterized by various methods including solid-state NMR, infrared spectroscopy and microanalysis. In the goal to develop environmentally friendly processes,these solids were used as catalysts for the deperoxidation of cyclohexyl hydroperoxide, an important step in the synthesis of adipic acid, a precursor of nylon 6-6.

The best metal is titanium and its performances are far above those of calcined supported titanium catalysts previously reported in the patent litterature. The influence on the catalytic activity of the nature of the coordination sphere and more specifically the number of covalent bonds between titanium and the silica support were studied. The catalysis is mainly heterogeneous as shown by various experiments. A non-negligible amount of titanium is leached during the first stages of the reaction but after some recycles the reaction rate remains constant allowing to suggest that this catalyst should be a good candidate for heterogeneous deperoxidation of cyclohexyl hydroperoxide.