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%.     

Effect of Mo loading on transesterification activities of MoO3/γ-Al2O3 catalysts prepared by conventional and slurry impregnation methods

Summary The effect of Mo loadings and preparation methods, slurry and conventional impregnation, on the performances of alumina-supported MoO₃ catalysts in transesterification of dimethyl oxalate (DMO) with phenol was investigated. Slurry prepared MoO₃/-Al₂O₃ catalyst exhibited higher activity and dispersion capacity than conventional one. Slurry MoO₃/water was used instead of an ammonium heptamolybdate solution. Highly dispersed amorphous Mo catalysts were obtained, closely related to the catalytic activities without calcination, waste solutions, and calcining nitrogenous gases.     

Preparation of MoO3/g-Al2O3 catalyst by the reaction of a-boehmite with MoO3/H2O slurry - dual role of MoO3 as active phase and texture stabilizer during calcination

Summary Catalyst MoO₃/g-Al₂O₃ was prepared by the reaction of a-boehmite with molybdic acid in slurry MoO₃/H₂O followed by calcination. The deposited MoO₃ functioned as thermal stabilizer and inhibited sintering of Al₂O₃ phase during calcination. After calcination at 550 and 650^oC the surface area of Al₂O₃ obtained from a-boehmite was 207 and 172 m² g^-1, respectively, and of MoO₃/Al₂O₃ obtained from MoO₃/a-boehmite was 323 and 285 m² g^-1, respectively. On the other hand, molybdic acid did not work as peptization agent and the mechanical strength of MoO₃/Al₂O₃ was not higher than of Al₂O₃. The catalyst was sulfided and its activity in thiophene hydrodesulfurization was tested; it exhibited about the same activity as reference industrial MoO₃/Al₂O₃ catalyst.     

Reducibility of Mo species in Pt/MoO3 and PtMo/Al2O3 catalysis

Recucibility of Mo species in Pt/MoO₃ and PtMo/Al₂O₃ has been investigated by temperature-programmed reduction (TPR), temperature-programmed desorption of hydrogen (H₂-TPD) and temperature programmed electronic conductivity (TPEC) techniques. In Pt/MoO₃ at H₂ atmosphere, it was found by TPEC and TPR that, a slight amount of Pt could activate the transfer of the species and H atoms between H₂ and MoO₃, and thus accelerate the reduction of MoO₃. In PtMo/Al₂O₃, TPR and H₂-TPD revealed that the reduction of surface Mo species could also be facilitated by Pt. Two kinds of hydrogen molybdenum species were proposed on the surface of the catalyst after prereduction.     

The support and characterization of C60 and MoO3 on Al2O3

A new type of catalyst from supporting C₆₀ on MoO₃ and Al₂O₃ has been prepared. The effect of different order of impregnation and calcination atmosphere on catalyst are investigated by the solution test in toluene, UV-VIS spectroscopy and temperature programmed reduction (TPR). The results show that when the catalyst was prepared by supporting MoO₃ on C₆₀/Al₂O₃ and calcined in N₂, there is a stronger interaction between C₆₀, MoO₃ and Al₂O₃, but when supporting C₆₀ on MoO₃/Al₂O₃, the interaction is relatively weak. We consider that in the former method a new complex, Mo–C₆₀–O–Al, is formed.     

Isothermal gravimetry and magnetic properties of CoOMoO3γAl2O3 catalysts

Isothermal gravimetry and magnetic susceptibility of MoO₃, MoAl₂O₃, CoAl₂O₃ and CoMoAl₂O₃ with/without Na⁺ ions have been studied in order to investigate the reducibility of the systems in H₂ H₂—hydrocarbons and H₂—hydro-carbon—thiophene. These studies have evidenced the formation of metallic cobalt during reduction of cobalt—moly catalysts containing Na⁺ ions in the Al₂O₃ support. This metallic cobalt accelerates the reduction of supported MoO₃. However, in the absence of sodium, cobalt exerts an inhibitory influence on the reduction of MoAl₂O₃. The inhibition is caused mainly due to retention of the water evolved during the process by well-dispersed Co²⁺ ions which are incapable of undergoing reduction. The presence of sulfur also kelps in suppressing the reduction to cobalt metal.     

Preparation of bimetallic CoO-MoO3/γ-Al2O3 and NiO-MoO3/γ-Al2O3 hydrodesulfurization catalysts by deposition of Co, Ni and Mo onto α-AlOOH during paste processing

CoO-MoO₃/γ-Al₂O₃ and NiO-MoO₃/γ-Al₂O₃ catalysts were prepared by the reaction of α-boehmite (α-AlOOH) with MoO₃ in an aqueous paste, followed by the reaction of the MoO₃/α-AlOOH catalyst with Co(OH)₂·CoCO₃ or 2NiCO₃·3Ni(OH)₂·4H₂O in an aqueous paste, and by subsequent drying and/or calcination. The deposited MoO₃ functioned as a thermal stabilizer inhibiting the sintering of the Al₂O₃ phase during calcination. The deposited Co and Ni were efficient activity promoters in benzothiophene hydrodesulfurization.     

TPR studies on steam reforming of 2-propanol on Rh/Al2O3, Ru/Al2O3 and Pd/Al2O3

Reaction pathways for steam reforming of 2-propanol (isopropyl alcohol, IPA) on Rh/Al₂O₃, Ru/Al₂O₃ and Pd/Al₂O₃ have been studied by temperature-programmed reactions (TPRs) of IPA and acetone in the presence of steam. The results of TPRs suggest that that of IPA on Rh/Al₂O₃ and Ru/Al₂O₃ proceeds via acetone, while the steam reforming of IPA on Pd/Al₂O₃ takes place via propene from acetone. This revised version was published online in August 2006 with corrections to the Cover Date.     

MoO3-C3N4复合光催化剂的可见光下高效催化降解甲基橙

以钼酸铵和C₃N₄为前驱体,利用浸渍法成功制备了高性能MoO₃-C₃N₄复合光催化剂,利用X射线衍射（XRD）、傅里叶红外（FT-IR）、高分辨电镜（HRTEM）及N₂吸附-脱附曲线等测试手段对所得MoO₃-C₃N₄光催化剂进行了结构和形貌表征。以可见光下光催化降解甲基橙反应表征MoO₃-C₃N₄的光催化活性。实验结果表明,MoO₃-C₃N₄光催化剂具有非常好的光催化降解性能,且MoO₃含量对反应活性产生显著影响。当MoO₃含量为1.6%（w/w）时光催化活性最好,其速率常数达到C₃N₄的50倍。通过研究发现该复合催化剂的高活性来自于其Z型光生载流子传输过程,抑制了光生电子空穴对的复合并延长了引入MoO₃产生的载流子的寿命。     

Cu修饰的Fe2O3/Al2O3氧载体的循环反应稳定性研究

采用冷冻干燥法制备了经Cu修饰（10%）的Fe₂O₃/Al₂O₃氧载体。利用热重分析仪分别在850、900和950 ℃等温环境下,使氧载体交替接触还原气体和氧化气体,来模拟氧载体在化学链燃烧中的循环过程。结果表明,经Cu修饰的Fe₂O₃/Al₂O₃氧载体在850和900 ℃下的等温循环过程中反应性能都很稳定,在950 ℃时的循环反应前期有微量烧结,但在循环后期反应性能也很稳定。随着反应温度的升高,氧载体氧化速率增大,还原速率和载氧率先减小后增大。与未经修饰的Fe₂O₃/Al₂O₃氧载体相比较,在900 ℃下作等温循环实验,经Cu修饰的Fe₂O₃/Al₂O₃氧载体具有较高的载氧能力和还原速率,但氧化速率较低;两者都具有较好的循环稳定性。     

Subsolidus phase equilibrium in Cs2MoO4-Al2(MoO4)3-Zr(MoO4)2 system and crystal structure of new ternary molybdate Cs(AlZr0.5)(MoO4)3

The subsolidus area of Cs₂MoO₄-Al₂(MoO₄)₃-Zr(MoO₄)₂ system was studied by X-ray powder diffraction. Two new molybdates with component molar ratios of 1: 1: 1 (S₁) and 5:1:2 (S₂) were synthesized for the first time. The crystallographic parameters of the 5:1:2 compound were determined. Solution- melt crystallization and spontaneous nucleation yielded crystals of new 1:1:1 cesium aluminum zirconium molybdate Cs(AlZr_0.5)(MoO₄)₃. Its formula unit and crystal structure were refined by X-ray diffraction (1592 reflections, R=0.0249). Trigonal crystals: a=12.9441(2) ?, c=12.0457(4) ?, V=1747.86(7) ?³, Z = 6, space group R $ \bar 3 $ \bar 3 . The three-dimensional combined framework of this structure is formed by MoO₄ tetrahedrons linked through common vertices to (Al,Zr)O₆ octahedrons. Cesium atoms occupy large cavities of the framework. Crystallographic position M(1) is occupied by randomly distributed Al³⁺ and Zr⁴⁺ cations.     

ZrO4/SiO2-Al2O3催化肉桂醛MPV转移加氢性能

以九水合硝酸铝（Al（NO₃）₃·9H₂O）与正硅酸乙酯（TEOS）为前驱盐,采用溶胶-凝胶法制备一系列不同Al₂O₃含量的SiO₂-Al₂O₃复合氧化物,并通过浸渍硝酸氧锆引入ZrO₂,制备ZrO₂/SiO₂-Al₂O₃复合氧化物催化剂,考察催化剂在肉桂醛（CAL）MPV转移加氢中的催化性能,并结合N₂物理吸附、X射线粉末衍射（XRD）、傅里叶变换红外光谱（FTIR）、NH₃-程度升温脱附（NH₃-TPD）、Py-原位红外（Py-IR）等技术,研究催化剂结构、织构以及表面性质与其催化性能间的构效关系.研究表明,所制备的催化剂均以L酸为主,并含有少量B酸中心,这使得加氢产物以肉桂醇（COL）为主,并含有少量1-苯丙烯-2-丙基醚（CPE）.Al₂O₃含量不仅影响催化剂表面的酸中心数量,而且对催化剂的织构参数有较大影响.随Al₂O₃含量的增加,催化剂表面L酸与B酸中心均有所增加,而孔径则持续变小,这使得催化反应呈现CAL转化率先增加后减少、目标产物COL选择性先稍有减小后有所增加的趋势.在Si/Al比为2时,催化剂具有最优的催化性能,优化反应条件下,CAL转化率达96%,目标产物COL选择性达90%.     

MoO3和SiO2掺杂对Ce0.8Nd0.2O1.9固体电解质结构和导电性能的影响

采用溶胶-凝胶法合成高纯(<50 mg·kg-1 SiO2)Ce0.8Nd0.2O1.9(NDC)和SiO2含量为500 mg·kg-1的Ce0.8Nd0.2O1.9(NDCSi)体系,将1mol%MoO3分别加入到NDC和NDCSi体系,比较研究MoO3掺杂对体系微观结构和电性能的影响。通过X射线衍射(XRD)和场发射扫描电子显微镜(FE-SEM)对材料进行表征,交流阻抗(AC)分析仪测试材料的电阻。结果表明:MoO3和SiO2的加入均没有破坏体系的立方莹石结构;MoO3掺杂能提高NDC和NDCSi陶瓷材料的致密度,提高其晶界电导率和总电导率;MoO3掺入NDC体系具有烧结助剂的作用,掺入NDCSi体系既具有烧结助剂的作用,又具有晶界改善剂的作用。     

过渡金属修饰Fe2O3/Al2O3氧载体的Redox性能研究

采用冷冻干燥法分别制备了经Cu、Co、Mn、Ni修饰的Fe₂O₃/Al₂O₃氧载体。利用化学吸附仪,通过程序升温还原(H₂-TPR)和程序升温氧化(TPO)来研究经不同过渡金属修饰的Fe₂O₃/Al₂O₃与H₂和O₂的反应性能。实验发现,在Fe₂O₃/Al₂O₃中加入Cu、Co、Ni以后,氧载体与H₂的反应性都有提高,但是当在Fe₂O₃/Al₂O₃中加入Mn以后,氧载体的反应性和载氧能力反而下降。经Cu修饰的Fe₂O₃/Al₂O₃与H₂的反应性最高,且具有很好的反应稳定性,适合用于化学链燃烧。     

Two-stage catalytic system of Sn/Al2O3 and Pt/Al2O3for NO reduction by propene in lean conditions

The Pt/Al₂O₃, Sn/Al₂O₃catalysts were prepared by the single sol-gel method. The two-stage Sn/Al₂O₃and Pt/Al₂O₃catalyst in series for NO reduction with propene were investigated. The coexistance of water vapor enhanced the activity at medium temperature of 300-400^oC, and the NO conversion was above 50% at 225 to 500^oC even in the presence of water vapor and SO₂. This revised version was published online in August 2006 with corrections to the Cover Date.     

NO reduction with C3H8 on Co/Al2O3 catalyst. effect of O2 concentration

The selective catalytic reduction (SCR) of NO by propane in excess oxygen-containing gas mixture was studied on Co/Al₂O₃ catalyst. The oxygen concentration is very important for the reaction. The NO conversion to N₂ without oxygen is 3% at 800 K and when the O₂ concentration is raised up to 8% the NO conversion reaches its maximum value of 60% at 800 K. Characterization results by TPR and UV-Vis spectroscopy show that in the catalyst, species strongly interacting with tetrahedral and octahedral Co²⁺ ions in the support are present. This revised version was published online in June 2006 with corrections to the Cover Date.     

Alkylation of phenol with dimethyl carbonate over AlPO4, Al2O3 and AlPO4-Al2O3 catalysts

The vapor-phase catalytic alkylation of phenol with dimethyl carbonate over different AlPO₄ (Al/P=1), Al₂O₃ and AlPO₄-Al₂O₃ (5–25 wt.% Al₂O₃) catalysts produces anisole (O-alkylation) as the major reaction product althougho-cresol (C-alkylation) and methylanisoles were also found. The reaction is first order in phenol while O-and C-alkylation follow parallel processes. As compared with methanol, DMC is far more effective as a methylating agent, and the methylation proceeds at a lower temperature and with higher O-alkylation selectivity.     

Preparation, morphology and properties of nano-sized Al2O3/polyimide hybrid films

Nano-sized Al₂O₃/polyimide (PI) hybrid films based on 4,4′-oxydianiline (ODA) and pyromellitic dianhydride (PMDA) were prepared by incorporation with different content of nano-sized Al₂O₃ via in situ polymerization. The TEM and SEM micrographs indicated that the Al₂O₃ particles were homogenously dispersed in the polyimide matrix by means of the ultrasonic treatment and the addition of coupling agent. The mechanical properties and thermal stability of the pure PI film can be improved by adequate addition of Al₂O₃. The PI hybrid film was strengthened and toughened simultaneously by the introduction of the well-dispersed Al₂O₃ particles. The PI hybrid films showed improved electrical aging performance as compared with pure PI film. Especially, the PI hybrid films with 10 wt.% of Al₂O₃ content exhibited obviously enhanced electrical aging performance with the time to failure of 3.4 times longer than that of pure PI film. The improved electrical aging performance of the hybrid film was attributed to the nano-sized Al₂O₃ particles highly dispersed in the hybrid film, which confirmed by the investigation of the morphology and the surface composition of PI hybrid film before and after electrical aging.     

系列硅铝比纳米薄层ZSM-5分子筛的合成和表征

以自制不对称双子季铵盐表面活性剂为模板, 在水热合成体系中控制合成系列硅铝比纳米薄层ZSM-5分子筛.采用X射线衍射(XRD)、N₂吸附-脱附、X射线荧光光谱(XRF)、扫描电镜(SEM)和²⁷Al魔角旋转核磁共振(²⁷Al MAS-NMR)对合成的样品进行了表征. 详细研究了晶化温度、晶化时间、结构导向剂(SDA)用量、碱度等对合成的影响和纳米薄层ZSM-5分子筛的形成过程. 结果表明: 分子筛硅铝比越高, 结构导向剂用量越大, 所需的晶化时间越短; 晶化温度越高, 晶化时间越短; 且不同硅铝比纳米薄层ZSM-5分子筛的形貌规整度、比表面积和介孔/微孔孔容比例随着硅铝比而变化.     

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…