有机-无机杂化材料负载钯催化苯酚氧化羰化合成碳酸二苯酯

 采用溶胶-凝胶法合成了有机-无机杂化材料(OIH),通过与PdCl2(PhCN)2反应,制备了固载化PdCl2/OIH非均相催化剂. 考察了此催化剂在苯酚直接氧化羰化合成碳酸二苯酯反应中的催化活性,并与均相PdCl2催化体系进行了比较. 结果表明,负载型催化剂的催化活性与均相体系相当. 当使用Cu2O和四氢呋喃分别作无机助剂和溶剂时,PdCl2/OIH催化剂重复使用5次后,碳酸二苯酯的产率基本保持不变,钯流失量仅为12.3%.     

高比表面SiC的合成及其在CO氧化反应中的应用

采用蔗糖为碳源, 正硅酸乙酯(TEOS)为硅源, 分别以草酸、硝酸铁、硝酸镍为催化剂, 用溶胶-凝胶法制备碳化硅前驱体, 考察了制备过程中催化剂的种类以及反应温度和时间对凝胶形成的影响. 发现以硝酸铁为催化剂最有利于凝胶的形成, 碳/硅物质的量比为4的前驱体在氩气气氛1350 ℃下加热10 h, 碳热还原反应趋于完成. 以该条件下合成的多孔碳化硅(比表面积133 m2·g-1)作为催化剂载体, 通过等量浸渍法获得Pt/SiC催化剂, 将其应用于一氧化碳氧化的模型反应中. 研究结果表明该催化剂有较好的催化活性和稳定性. 引入镍助剂的PtNi/SiC催化剂能进一步提高一氧化碳催化氧化反应的活性.     

Ni/SiO_2、Ni/TiO_2-SiO_2催化剂上顺酐液相选择加氢合成γ-丁内酯

通过溶胶-凝胶方法结合超临界干燥技术制备了SiO2和TiO2-SiO2复合氧化物气凝胶载体,采用等体积浸渍法制备了Ni/SiO2和Ni/TiO2-SiO2催化剂,运用BET、H2-TPR、XRD、TEM及FT-IR等手段对催化剂进行了表征,并考察了催化剂在顺酐液相选择加氢合成γ-丁内酯反应中的催化性能.结果表明,Ni/TiO2-SiO2催化剂中Ti-O-Si键的形成增强了NiO与载体的相互作用,促进了NiO在载体表面的分散,得到了晶粒较小的活性Ni0物种,表现出高的加氢活性,在H2压力5.0 MPa、反应温度240℃、反应时间6 h的条件下,顺酐转化率为100%,γ-丁内酯的选择性达94.7%.     

铁掺杂铈基复合氧化物CO催化还原NO的性能研究

采用浸渍法、水热法和微波加热法制备铁掺杂的铈基复合氧化物催化剂,研究温度、铈铁摩尔比、制备方法对铈基复合氧化物的催化还原性能的影响,并且使用BET, NO-TPD, H₂-TPR, XRD, Raman等对催化剂进行表征分析。结果表明：随着温度的升高,NO转化率是一个先不断增加后趋于稳定的过程;无论是浸渍法、水热法还是微波加热法,最佳铈铁摩尔比均为10∶2; 3种制备方法的催化活性顺序：微波加热法>水热法>浸渍法。微波加热法制备的铈基复合氧化物催化剂在500℃的脱硝率为76%,脱硝率在700℃达到99%。通过XRD和Raman表征说明Fe³⁺取代Ce⁹⁴⁺进入到CeO₂晶格中,改变CeO₂的萤石结构,增加氧空位,造成晶格畸变。     

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.     

非均相催化一步合成碳酸二苯酯的研究 I．载体制备方法对催化剂性能的影响

采用溶胶－凝胶法、共沉淀法和冷冻干燥法，制备了LaxMnyPbzO复合型氧化物载体，并以PbCl2或Na2PbCl4的水溶液为浸渍液，通过浸渍方法制固相催化剂，用于一步俣成碳酸二苯酯，用XRD，TEM及SEM对载体及催化剂进行了表征，结果表明，三种载体的主要物相皆为La0.3Mn0.5PbO，溶胶－凝胶法制得的载体及催化剂的粒径分布较好，空隙率较大，活性组分分散度较高；溶胶－凝胶法制得的催化剂的催化性能较好，碳酸二苯酯选择属于选择性可高于99．5％。     

锰铈混和氧化物气凝胶催化剂的研究

采用溶胶-凝胶法和超临界干燥技术制备出CeO2和Ce1-xMnxO2(x分别为0.05, 0.10, 0.15,0.20)气凝胶。以硝酸锰浸渍制得的氧化铈气凝胶Mn/CeO2,用TEM、BET、一氧化碳催化氧化活性评价和H2-TPR对所制备的催化剂进行了研究。TEM、BET的结果表明，随着锰含量的增加，氧化铈气凝胶的粒度减小，表面积增大。一氧化碳催化氧化活性评价显示,氧化铈中添加锰制得的催化剂的一氧化碳低温催化氧化的活性比未添加锰的氧化铈提高。且锰加入量为15 mol%时，气凝胶的催化活性最高。锰的引入方式不同，气凝胶的催化活性不同。浸渍方式负载锰所制备的Mn/CeO2气凝胶的一氧化碳催化氧化活性低于Ce1-xMnxO2(x分别为0，0.05, 0.10, 0.15,0.20)气凝胶。TPR实验发现，与氧化锰相同，氧化铈上负载的锰的还原也分三步进行。     

AuPd/SiO_2催化剂用于无溶剂条件下分子氧液相氧化甲苯

采用浸渍法和溶胶负载法制备了一系列Au-Pd双金属催化剂,用氮吸附法,X光粉末衍射(XRD)、程序升温还原(TPR),扫描电镜(SEM)和X射线光电子能谱(XPS)对催化剂进行了表征.以分子氧为氧化剂,在无任何其它溶剂存在的条件下,考察了催化剂制备方法、不同类型载体、Au/Pd原子比、浸渍顺序、活化温度、催化剂用量及反应时间等多种因素对甲苯选择氧化反应的影响.实验结果表明:对SiO_2载体,以共浸渍法制备的催化剂活性和选择性最好;TiO_2载体,以溶胶负载法制备的催化剂活性和选择性较好;Au Pd双金属催化剂比单金或者单钯催化剂具有更好的催化活性.其中Au Pd/SiO_2-I催化剂使甲苯转化率达到56.8%,苯甲酸苄酯的选择性为9 1.3%,TON值为3692.Au Pd/SiO_2-I催化剂中氧化态的钯和零价金更利于催化剂中的电子传递从而利于催化氧化反应的进行.     

草酸盐凝胶共沉淀法制备Ni-Ce-O甲烷催化燃烧催化剂

 采用草酸盐凝胶共沉淀法制备了系列Ni-Ce-O复合氧化物催化剂,考察了制备方法及催化剂组成对其催化甲烷燃烧性能的影响. 结果表明,草酸盐凝胶共沉淀法制备的Ni-Ce-O催化剂上甲烷的催化燃烧活性明显高于常规方法制备的Ni-Ce-O催化剂; Ni-Ce-O催化剂的组成显著影响其催化性能. 当镍/铈比值为4时,在406 ℃时即可使50%甲烷转化. Ni-Ce-O复合氧化物中NiO的晶格微应变是影响其催化甲烷燃烧性能的重要因素.     

V2O5/TiO2-ZrO2催化剂上甲醇选择氧化制甲缩醛

采用共沉淀法制备TiO2-ZrO2复合氧化物载体、等体积浸渍法制备V2O5/TiO2-ZrO2催化剂,对催化剂在温和条件下甲醇选择氧化生成甲缩醛(DMM)反应进行研究.结果表明,与单一氧化物载体TiO2或ZrO2负载的钒基催化剂相比,V2O5/TiO2-ZrO2对甲醇选择氧化具有较好的催化性能.XRD、NH3-TPD和...     

Effect of sepiolite fiber on the structure and properties of the sepiolite/silica aerogel composite

Sepiolite fiber-reinforced silica aerogel composites for thermal insulators were prepared by dispersing sepiolite fiber in silica sol, aging, solvent exchanging, and drying in supercritical fluid. The surface treated sepiolite fiber and sepiolite/silica aerogel composite were characterized by scanning electron microscope; transmission electron microscope and Fourier transform infrared spectroscopy. The influence of surface treated sepiolite fiber on the mechanical and thermal properties of the aerogel composite was studied. The results indicate the hydroxyl groups on silica sol particles surface able to condense with the hydroxyls of sepiolite fibers with forming Si–O–Si between sepiolite fibers and aerogel matrix in the sol–gel process, which achieves excellent interfacial interaction in the sepiolite/silica aerogel composite, so the mechanical properties of the aerogel composite have been improved effectively without sacrificing much thermal insulating performance.     

Physicochemical properties and hydrogenation activity of nickel-alumina aerogels

Nickel-alumina aerogel catalysts were prepared by three methods: (I) hydrolysis of a mixture of aerogel precursors, followed by cogelation of the sols obtained and drying under supercritical conditions; (II) impregnation of thermally treated alumina aerogels with nickel salt solutions followed by drying of the suspensions obtained under supercritical or (III) conventional conditions. Activity of the aerogel catalysts prepared was determined in cyclohexene hydrogenation.     

Methanation of carbon dioxide on Ni/ZrO2-Al2O3 catalysts:Effects of ZrO2 promoter and preparation method of novel ZrO2-Al2O3 carrier

The novel nickel-based catalysts with a nickel content of 12 wt% were prepared with the zirconia-alumina composite as the supports. The new carriers, ZrO2 improved alumina, were synthesized by three methods, i.e., impregnation-precipitation, co-precipitation, and impregnation method. The catalytic properties of these catalysts were investigated in the methanation of carbon dioxide, and the samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscope (XPS), temperature-programmed reduction (TPR) and temperature-programmed desorption (TPD) techniques. The new catalysts showed higher catalytic activity and better stability than Ni/γ-Al2O3. Furthermore, as a support for new nickel catalyst, the ZrO2-Al2O3 composite prepared by the impregnation-precipitation method was more efficient than the other supports in the methanation of carbon dioxide. The highly dispersed zirconium oxide on the surface of γ-Al2O3 inhibited the formation of nickel aluminate-like phase, which was responsible for the better dispersion of Ni species and easier reduction of NiO species, leading to the enhanced catalytic performance of corresponding catalyst.     

Ni-based xero- and aerogels as catalysts for nitroxidation processes

Porous nanocomposites made out of nickel dispersed on silica or alumina matrices were prepared as prospective catalysts for the nitroxidation of hydrocarbons in the form of aerogel or xerogel by adopting either a supercritical or a conventional gel drying procedure. The structural and textural features of the materials were investigated by X-ray diffraction, transmission electron microscopy and N₂ physisorption and combined to the acid/base and reducibility data as deduced by adsorption microcalorimetry and temperature programmed reduction (TPR) profiles. The alumina-based samples are made out of nanocrystalline nickel aluminate and are mesoporous, although the aerogel has larger pore volumes and surface area than the xerogel. On the other hand, in the silica-based samples nickel oxide nanocrystals are dispersed on amorphous silica, the size of the nanocrystals being around 5 nm in the microporous xerogel and 14 nm in the mainly mesoporous aerogel. TPR data point out that the alumina-based samples have similar reducibility, whereas significant differences were observed in the silica-supported composites, the NiO–SiO₂ aerogel exhibiting improved reducibility at low temperature. The NO-catalyst interaction was monitored by temperature programmed NO reaction coupled to mass spectrometry and preliminary tests on the use of the NiO–SiO₂ xerogel and aerogel nanocomposites for the catalytic nitroxidation of 1-methyl-naphthalene to 1-naphthonitrile were obtained in a fixed-bed continuous-flow reactor. The data indicate that the aerogel exhibits larger selectivity than the corresponding xerogel, pointing out the importance of tuning the sol–gel parameters in the design of porous composite materials for catalytic applications.     

Preparation of SiO2-TiO2 Aerogels Using Supercritical Impregnation

The preparation of SiO₂-TiO₂ aerogels by supercritical impregnation of titanium alkoxides into silica alcogels was investigated. A mixture of CO₂ and 2-propanol with dissolved titanium tetraisopropoxide modified with acetylacetone was used as the impregnation medium. Prior to the experiments, the supercritical behaviour of the impregnation solution was investigated. The microstructure and properties of aerogels prepared by the supercritical impregnation method were almost identical to those generated by the liquid impregnation. However, the time for impregnation was substantially decreased and the homogeneity of the impregnated titanium distribution on the aerogel increased.     

Pillaring effects in macroporous carrageenan-silica composite microspheres

The impregnation of a carrageenan gel by a silica sol is an efficient method to form a composite material which can be conveniently activated by CO2 supercritical drying. The textural properties of the solids have been characterized by nitrogen adsorption-desorption at 77 K and their composition by thermogravimetric analysis and EDX microprobe. Morphology was examined by SEM. The silica-carrageenan composites present an open macroporous structure. Silica particles retained inside the gel behaved as pillars between the polysaccharide fibrils and form a stick-and-ball network. The stiffening of the carrageenan gel by silica prevented its shrinkage upon drying. The nature of the alkali cations affected the retention of silica particles inside the gel. In the absence of silica, carrageenan fibrils rearrange under supercritical drying and form an aerogel with cavities in the mesopore range.     

流化床反应器中不同Ni/Al2O3催化剂上CH4-CO2重整反应性能的比较研究

采用浸渍法、溶胶 凝胶过程与普通干燥、超临界干燥过程相结合的方法制备了三种20%的NiO-Al2O3体系催化剂，利用BET、XRD、H2 TPR、H2-TPD等方法对各催化剂样品物化性质进行了表征，并考察了催化剂在流化床反应器中CH4-CO2重整反应的催化性能。研究结果表明，经923K焙烧后气凝胶催化剂中镍与载体间作用力最强，主要为固定NiO和尖晶石NiAl2O4结构，而浸渍型催化剂和干凝胶催化剂中镍与载体间作用力较弱。三种催化剂中，气凝胶催化剂具有比表面积较大、堆密度较低、Ni还原度及分散度较高的特点。它在流化床反应器中所形成的聚团流态化状态具有较高的床层膨胀率，大量多孔疏松状的纳米颗粒聚团在床内的循环运动有效地提高了传质效率，能使得生成的沉积炭快速得到气化，从而抑制了催化剂失活；对于浸渍型催化剂和干凝胶催化剂，流化床反应器中床层膨胀率较低、颗粒循环量较少、传质效率较低，易于造成催化剂表面积炭失活。经用TG和XRD等方法对反应后催化剂分析表征，证明催化剂表面石墨碳的沉积是导致浸渍型催化剂和干凝胶催化剂失活的主要原因。     

溶胶—凝胶法制备NiO／SiO2催化剂研究

分别以正硅酸乙酯、硝酸镍为硅源和镍源,采用溶胶－凝胶法,经超临界流体干燥和普通干燥制备了NiO-A-SiO2、NiO-G-SiO2催化剂;以气凝胶和干凝胶为载体,采用浸渍法制备了NiO/A-SiO2、NiO/G-SiO2催化剂。并用XRD、TEM、BET、TPR等手段,研究了制备方法对催化剂织构、结构和Ni物种存在形态的影响,发现NiO-A-SiO2和NiO-G-SiO2催化剂上高度分散的NiO簇团与SiO2之间有较强的相互作用,其顺酐液相选择加氢转化率低于10％;NiO/G-SiO2催化剂上,以单一物种形态存在的NiO与SiO2相互作用弱,顺酐转化率为42％;NiO/A-SiO2催化剂上,以多种形态存在的微量NiO与SiO2间的相互作用较复杂,其顺酐液相选择加氢的转化率和丁二酸酐的选择性分别可达100％和98％。     

DMF及热处理对常压制备Cu掺杂SiO2纳米复合气凝胶的影响

以正硅酸乙酯(TEOS)为硅源, 硝酸铜(Cu(NO3)2·3H2O)为铜源, 通过在复合溶胶体系中引入干燥控制化学添加剂(DCCA)N,N-二甲基甲酰胺(DMF)进行原位共溶胶-凝胶, 结合常压干燥工艺, 制备出具有高比表面积(560 m2·g-1)的Cu-SiO2纳米复合气凝胶(含铜质量分数为5%). 研究了DMF对凝胶时间、干燥过程和复合气凝胶形态结构的影响, 利用N2物理吸附, 全自动X射线衍射(XRD)仪, 傅立叶变换红外(FT-IR)光谱仪, 透射电子显微镜(TEM)等对样品的形貌结构进行了表征. 实验结果表明, DMF能有效防止凝胶的开裂, 抑制颗粒团簇的产生, 使所得复合气凝胶的粒径减小, 比表面积增加, 微观结构更趋完善. 高温热处理后, Cu-SiO2中的铜物种仍高度分散于骨架网络中, 复合气凝胶显示出良好的热稳定性.     

勃姆石纤维增强二氧化硅气凝胶的制备及性能

以六水合氯化铝为铝源, 通过水热法制备勃姆石纤维; 以甲基三甲氧基硅烷和正硅酸乙酯为硅源共前驱体, 采用溶胶-凝胶法进而常压干燥制备了勃姆石纤维掺杂的二氧化硅复合气凝胶; 探究了勃姆石纤维的掺杂量对复合气凝胶性能的影响. 当勃姆石纤维的掺杂量(质量分数)为1%时, 气凝胶的机械性能最好, 能够承受17.1%的压缩应变, 最大压缩强度为1.12 MPa, 压缩模量高达2.57 MPa, 复合气凝胶在150 ℃仍然具有较低的导热系数(0.0670 W·m^?1·K^?1). 勃姆石纤维能够一定程度地抑制二氧化硅颗粒在高温下的烧结和相转变, 对二氧化硅气凝胶的耐高温性能有显著的提升作用, 复合气凝胶在1100 ℃高温热处理后, 仍能保持良好的隔热性能和较高的机械强度.