热扩散法制备MoO3/SiO2催化草酸二甲酯和苯酚酯交换反应

采用热扩散法（TS）和等体积浸渍法制备了MoO₃/SiO₂催化剂用于草酸二甲酯和苯酚酯交换反应.结果表明,热扩散法制备的10%MoO₃/SiO₂-TS催化剂较等体积浸渍法制备的10%MoO₃/SiO₂-C催化剂具有更好的催化性能.运用X射线衍射、Raman光谱、X射线光电子能谱分析、吡啶吸附红外光谱、NH₃程序升温脱附等手段对催化剂进行了表征,发现虽然两种方法制备的催化剂都只有弱Lewis酸中心,钼均以氧化钼单体形式存在,未形成解离和聚合,但是10%MoO₃/SiO₂-TS催化剂较10%MoO₃/SiO₂-C催化剂表面钼含量更高且MoO₃分散得更好.在苯酚用量为0.2mol,10%MoO₃/SiO₂-TS催化剂用量为1.2g,反应温度为180℃,草酸二甲酯与苯酚的摩尔比为2,反应时间为4h的优化条件下,苯酚转化率可达70.9%,甲基苯基草酸酯和草酸二苯酯的收率分别达63.1%和7.7%.     

有机钛催化草酸二甲酯与苯酚酯交换反应

研究了几种有机钛化合物对草酸二甲酯(DMO)与苯酚酯交换反应的催化性能,发现催化活性及选择性顺序依次为二氯二茂钛钛酸四苯酯钛酸丁酯乙酰丙酮氧钛钛酸乙酯钛酸异丙酯,表明二氯二茂钛是一种性能较好的酯交换催化剂.在n(Cp2TiCl2)=0.001 mol、n(DMO)=0.3 mol、n(Phenol)=0.2 mol、T=180℃、t=2 h优化工艺条件下,苯酚转化率可达44.0%,甲基苯基草酸酯(MPO)和草酸二苯酯(DPO)收率分别达37.8%和6.1%,酯交换总选择性为99.8%.     

有机钛催化草酸二甲酯与苯酚酯交换反应

研究了几种有机钛化合物对草酸二甲酯(DMO)与苯酚酯交换反应的催化性能,发现催化活性及选择性顺序依次为二氯二茂钛＞钛酸四苯酯＞钛酸丁酯＞乙酰丙酮氧钛＞钛酸乙酯＞钛酸异丙酯,表明二氯二茂钛是一种性能较好的酯交换催化剂。在n(Cp2TiCl2) = 0.001 mol、n (DMO) =0.3mol、n (Phenol) = 0.2mol、T=180癈、t=2h优化工艺条件下,苯酚转化率可达44.0%,甲基苯基草酸酯(MPO)和草酸二苯酯(DPO)收率分别达37.8%和6.1%,酯交换总选择性为99.8%。     

MoO3-TiO2/SiO2上光促表面催化甲烷和水合成甲醇和氢气

用分步等体积浸渍法制备了负载型复合半导体催化剂MoO3-TiO2/SiO2,通过XRD,BET,TPR,IR,UVDRS和TPD等手段对其进行了表征,结果表明,活性组分在载体表面高度分散,并具有量子尺寸效应,吸光阈值显著蓝移;TiO2在SiO2表面分散可增强MoO3与载体的相互作用,调变吸光性能,所形成的表面活性基元能够有效地吸附活化甲烷和水.在100℃下利用固定床环隙反应器借助紫外光的激发,通过“光-表面-热”协同作用,气相甲烷和水在MoO3-TiO2/SiO2表面生成了甲醇和氢,选择性达到85.6%.     

镍含量对NiO/SiO2气凝胶性能的影响

A series of NiO/SiO₂ aerogel catalysts were prepared by sol-gel method. The effects of the nickel content on the structure and existing forms of NiO/SiO₂ aerogel catalysts were investigated by using XRD, TPR and FT-IR. The results showed that there were interactions between NiO and SiO₂. But as nickel content increased, the in-teraction decreased. The nickel oxide in the catalysts appeared in different forms as nickel content was changed. When the content was less than 13%, Ni(Ⅱ) entered into the SiO₂ structure completely and it became clusters after calcining. If the content altered from 20% to 50%, NiO existed as both microcrystal and clusters, the later spices was dominating. However, when the content increased to 70%, microcrystal became the primary components.     

苯酚和草酸二甲酯在不同分子筛催化下的酯交换反应

研究了以TS－1、H－ZSM－5、Hβ和H－丝光沸石等不同分子筛为催化剂，苯酚和草酸二甲酯酯交换合成草酸二苯酯反应。通过对催化剂进行吸附吡啶的红外光谱和NH3－TPD表征，考察了不同分子筛催化剂的酸性和酸强度对草酸二苯酯合成反应的影响，确定了催化剂上的弱酸中心是催化苯酚和草酸二甲酯酯交换合成草酸二苯酯反应的活性位，且催化剂的酸性中心越多，酸量越大，催化活性越好。催化剂上的强酸中心促进了副产物苯甲醚的生成。     

溶胶凝胶法制备Nd2O3改性钛酸钡陶瓷的研究

The technological condition for the preparation of BaTiO₃ ceramics doped with Nd₂O₃ by Sol-Gel was deter-mined through orthogonal experiment. When n_Ba(Ac)2∶n_Ti(OC4H9)4∶n_Nd2O3∶n_{CH3(CH2)2CH2OH}∶n_H2O=1.00∶1.00∶0.003∶7.30∶37.04, pH=3.5,T=25℃,the light-yellow-transparent-stable solution and thorough transparent gel was generat-ed, the transforming time of solution to gel was 25h. The crystal structure and particle size of BaTiO₃ ceramics doped with Nd₂O₃ were studied by SEM and X-ray respectively, the type of the crystal was tetragonal, the particle size was about 24.7nm. The dielectric constant (ε) and dielectric loss (tanδ) of BaTiO₃ ceramics doped with Nd₂O₃ were determined between 10⁴～10⁶Hz, and the results showed that the dielectric constant was increased obviously, the dielectric loss was decreased clear and the resistivity (ρ_V) was also decreased noticeably.     

溶胶-凝胶法制备Li3V2(PO4)3及其性能研究

0引言具有类NASICON结构的Li3V2(PO4)3是继过渡金属氧化物LMO后的一种新型的锂离子二次电池正极材料。与目前市场上应用最为广泛的正极材料LiCoO2相比,Li3V2(PO4)3具有超常的稳定性,即使在脱出的Li 与过渡金属原子的物质的量之比大于1的时候仍然具有超乎寻常的稳定性,而通常情况下1mol LiCoO2在脱出0.5mol Li 就会变得不稳定。并且Co是一种战略物资,全球储量十分有限;Co也是一种有毒金属,对于环境污染较为严重。LiNiO2因其合成较为困难而使应用受限,尖晶石LiMn2O4虽然属于环境友好型化合物,但其理论比容量仅为148mAh·g-1,且…     

溶胶-凝胶法制备LiCoO2薄膜的研究

以LiNO3和Co(NO3)2为主要原料、采用溶胶-凝胶旋涂法在(111)单晶硅片上制备了LiCoO2薄膜.X射线衍射结果表明,涂液中Li+离子和Co2+离子的总浓度与配比可影响薄膜的成分.薄膜的最佳烧结温度与最佳烧结时间分别为600～700℃和30～60min.涂液中柠檬酸、聚乙烯乙二醇、去离子水的含量与热处理时的升温速率对薄膜的形貌有很大影响.     

溶胶-凝胶法制备纳米WO3气致变色材料

本文主要阐述了纳米WO₃气致变色材料的溶胶-凝胶制备方法、气致变色机理及其应用的研究新进展,重点评述了溶胶-凝胶法中各种制备条件诸如掺杂、模板剂、溶剂、热处理温度等对这种材料的结构和性能的影响,最后展望了纳米WO₃气致变色材料的研究和应用前景。我们认为,在未来的溶胶-凝胶法制备纳米WO₃气致变色材料领域,如何进行最优化的掺杂设计和选择高效模板剂、如何降低气体检测温度、以及气致变色机理等将是该项研究的重点。     

TS-1分子筛催化苯酚和草酸二甲酯合成草酸二苯酯

碳酸二苯酯;酯交换;TS-1分子筛催化苯酚和草酸二甲酯合成草酸二苯酯     

TiO2／SiO2催化苯酚和草酸二甲酯酯交换合成草酸二苯酯

Diphenylcarbonate (DPC)isabasicmaterialfornon phosgene productionof polycarbonates .Severalalternativenon phosgenemethodsforDPCsynthesishavealsobeenproposed ,oneofthemisthetranses terificationofdimethyloxalate (DMO)withphenoltodiphenyloxalate (DPO)andthedecarbonylationofDPOtoDPC .Inthisprocess ,thesynthesisofDPOfolloweda 2 stepreactionmoduleoftransesterifi cationofDMOwithphenoltomethylphenyloxalate(MPO)andthedisproportionationofMPOtoDPOandDMO[1] .UbeIndustriesreportedthatconven…     

苯酚和草酸二甲酯酯交换合成碳酸二苯酯反应产物的气相色谱-质谱分析

采用气相色谱-质谱联用、程序升温方法对苯酚和草酸二甲酯酯交换合成碳酸二苯酯反应产物进行了分析。实现了对钛酸四丁酯催化苯酚和草酸二甲酯二甲酯酯交换合成草酸二苯酯反应的主产物草酸二苯酯、中间产物甲基苯基草酸酯、副产物丁基苯基草酸酯、2-甲基丁醛、正丁醚及草酸二苯酯脱羰基生成碳酸二苯酯反应产物的定性，验证了苯酚和草酸二甲酯酯交换合成碳酸二苯酯反应分三步进行的反应模式。     

Sn改性TS－1分子筛催化苯酚和草酸二甲酯合成草酸二苯酯

 使用Sn改性的TS－1分子筛催化苯酚和草酸二甲酯的酯交换反应合成草酸二苯酯，深入研究了不同Sn负载量TS－1分子筛的结构及催化性能．实验结果表明，由于Sn和以Ti－O－SiO3为中心的弱Lewis酸的协同催化作用，与未改性的TS－1分子筛催化剂相比，改性后的催化剂虽 然Lewis酸量有明显下降，但催化剂的催化性能明显提高．当Sn的负载量为2％时，草酸二甲酯的转化率达到50．3％，目的产物的选择性为99．2％．利用X射线衍射、X射线光电子能谱和X射线能量分散谱考察了Sn在TS－1分子筛表面的结构和分散状态及其与酯交换反应催化性能的关系．结果表明，当Sn的负载量低于2％时，SnO2以非晶态形式分散在TS－1表面；而当Sn负载量高于2％时，SnO2以微晶的形式存在，此时Sn原子与Ti原子的协同作用已经不明显，催化剂的催化性能反而下降．     

Sn改性TS-1分子筛催化草酸二甲酯和苯酚酯交换合成草酸二苯酯

 研究了Sn改性TS-1催化剂催化苯酚和草酸二甲酯（DMO）酯交换合成草酸二苯酯(DPO)反应。以Sn改性TS-1为催化剂时，Sn活性中心和Lewis酸中心协同作用催化苯酚和DMO酯交换合成DPO反应。因为Sn的加入，在保持MPO和DPO高选择性的同时，DMO转化率显著提高。而且Sn活性中心有利于MPO歧化反应生成DPO，从而大大提高了DPO的选择性。但是，当Sn负载量大于2％时，SnO2由均匀分布在TS-1表面改变为以晶体状态存在，从而导致DMO转化率的大幅降低。     

催化剂对碳酸二甲酯与苯酚酯交换反应的影响

甲基苯基碳酸酯;碳酸二苯酯;催化剂对碳酸二甲酯与苯酚酯交换反应的影响     

Thermal Stability of Pt/Al2O3 Catalysts Prepared by Sol-Gel

A series of Pt/Al₂O₃ catalysts were prepared using a sol-gel method. The influence of several parameters used in the synthesis including: metal content, identity of the metal precursor, and the water/alkoxide ratio on the structural properties of the fresh (dried) and calcined samples were studied. It was found that the BET surface area decreased with an increase in the platinum content. A surface area of 500 m²/g was obtained following calcination at 773 K. The structure of fresh samples as determined by FTIR corresponded to that of a pseudoboehmite structure. Samples prepared using a water/alkoxide ratio (H₂O/ATB) of 9 showed a well-defined, uniform pore size distribution following calcination at 773 K. Metal dispersions comparable to those obtained using impregnation methods were obtained. Aging studies (calcination at 873 K for 24 h) performed on these catalysts, exhibited sintering behavior which were similar to Pt/Al₂O₃ catalysts prepared by other methods. The sample prepared using a H₂O/ATB ratio of 9 had the highest surface area and was more thermally resistant towards metal sintering. A bimodal metal particle size distribution was observed: some particles exhibited sintering while others of similar size showed a greater thermal stability to sintering. The sample having the largest surface area and the highest thermal stability following thermal treatment was a consequence of a more condensed structure and a higher pore roughness obtained after drying the gel. This enabled the formation of an alumina structure which was more amorphous and limited aggregation of platinum particles due to surface diffusion within the pore structure.     

Effect of Mo content in MoO3/g-Al2O3 on the catalytic activity for transesterification of dimethyl oxalate with phenol

The influence of molybdenum content on the catalytic performance in the transesterification of dimethyl oxalate (DMO) with phenol to methyl phenyl oxalate (MPO) and diphenyl oxalate (DPO) was investigated. The results indicated that the MoO₃/Al₂O₃ catalyst with 14 wt% Mo content gave maximal DPO yield with 6.1% and 75.1% DMO conversion. The component, structure and phase of MoO₃/Al₂O₃ catalysts were characterized by means of X-ray diffraction (XRD), BET specific surface area, temperature-programmed desorption of ammonia (NH₃-TPD), and FTIR analysis of adsorbed pyridine. This revised version was published online in June 2006 with corrections to the Cover Date.     

Cu/SiO2催化剂制备方法对其草酸二甲酯催化氢解性能的影响

以化学吸附水解法、蒸氨法和浸渍法制备了Cu/SiO2催化剂, 并用于草酸二甲酯氢解制备乙二醇的反应. 发现用化学吸附水解法制备的催化剂具有最高的催化活性和乙二醇选择性, 乙二醇得率可达92.6%. 对还原前后不同方法制备的催化剂进行表征发现, 浸渍法制备的催化剂中Cu物种不能很好地得到分散, 因此活性较差. 蒸氨法和化学吸附水解法能较好地分散Cu物种. 由于化学吸附水解法制备的催化剂的Cu0表面积较蒸氨法的大, 且Cu＋表面积相当, 故活性高于蒸氨法制备的催化剂.