Preparation of nanocrystalline γ-Al_2O_3 catalyst using different procedures for methanol dehydration to dimethyl ether

A series of nanocrystalline γ-alumina are synthesized by different procedures, namely, thermal decomposition method (sample A), precipita-tion method (sample B) and sol-gel method using sucrose and hexadecyltrimethyl ammonium bromide (CTAB) as templates (samples C and D, respectively). Textural and acidic properties of γ-alumina samples are characterized by XRD, N2 adsorption-desorption and NH3-TPD techniques. Vapor-phase dehydration of methanol into dimethyl ether is carried out over these samples. Among them, sample C shows the highest catalytic activity. NH3-TPD analysis reveals that the sample with smaller crystallite size possesses higher concentration of medium acidic sites and consequently higher catalytic activity. Thermal decomposition method leads to decrease in both surface area and moderate acidity, therefore it is the cause of lower catalytic activity.     

Effect of ultrasonic irradiation and /or halogenation on the catalytic performance of γ-Al2O3 for methanol dehydration to dimethyl ether

Dimethyl ether(DME) is amongst one of the most promising alternative,renewable and clean fuels being considered as a future energy carrier.In this study,the comparative catalytic performance of the halogenated γ-Al 2 O 3 prepared from two halogen precursors(ammonium chloride and ammonium fluoride) is presented.The impact of ultrasonic irradiation was evaluated in order to optimize both the halogen precursor for the production of DME from methanol in a fixed bed reactor.The catalysts were characterized by SEM,XRD,BET and NH 3-TPD.Under reaction conditions where the temperature ranged from 200 to 400 ℃ with a WHSV = 15.9 h-1was found that the halogenated catalysts showed higher activity at all reaction temperatures.However,the halogenated alumina catalysts prepared under the effect of ultrasonic irradiation showed higher performance of γ-Al 2 O 3 for DME formation.The chlorinated γ-Al 2 O 3 catalysts showed a higher activity and selectivity for DME production than fluorinated versions.     

A Novel Way to Prepare γ-Al2O3 Supported SO42-/ZrO2 Solid Superacid Catalysts for n-Butane Isomerization

Highly active solid superacid catalysts for n-butane isomerization, SZ/Al2O3-P, were prepared by supporting SO42-/ZrO2 (SZ) on γ-Al2O3 carrier using a precipitation method.The activities of some catalysts were enhanced significantly.The activity of the most active sample, 60%SZ/Al2O3-P, was even about 2 times more active than that of the SZ catalyst.     

Preparation and properties of magnetic alumina microspheres with a γ-Fe_2O_3/SiO_2 core and Al_2O_3 shell

Magnetic alumina composite microspheres with γ-Fe 2 O 3 core/Al 2 O 3 shell structure were prepared by the oil column method. A dense silica layer was deposited on the surface of γ-Fe 2 O 3 particles (denoted as γ-Fe 2 O 3 /SiO 2 ) with a desired thickness to protect the iron oxide core against acidic or high temperature conditions. γ-Fe 2 O 3 /SiO 2 /Al 2 O 3 particles with about 85 wt% Al 2 O 3 were obtained and showed to be suitable for practical applications as a magnetic catalyst or catalyst support due to their magnetic properties and pore structure. The products were characterized with scanning electron microscope (SEM) and transmission electron microscope (TEM), nitrogen adsorption-desorption, and vibrating sample magnetometer (VSM). The specific surface area and pore volume of the γ-Fe 2 O 3 /SiO 2 /Al 2 O 3 composite microspheres calcined at 500 ? C were 200 m 2 /g and 0.77 cm 3 /g, respectively.     

Environment-friendly synthesis of N-phenylpiperidine from aniline and 1,5-pentanediol over γ-Al2O3 catalyst

An efficient environment-friendly synthesis of N-phenylpiperidine was developed from aniline and 1,5-pentanediol over γ-Al2O3 catalyst under atmospheric pressure. The conversion of 1,5-pentanediol reached 97% and the selectivity for N-phenylpiperidine attained 94%. The structure of the catalyst was characterized by NH3-TPD and BET. The influences of calcination temperature of the catalyst and reaction temperature on activity and selectivity of the catalyst were investigated.     

NiO在γ-Al_2O_3及 TiO_2/γ-Al_2O_3载体上的表面存在状态

本文采用 LRS, XRD, UV-DRS, TPR考查了γ-Al2O3上 TiO2的分散容量,分散态 Ti4＋离子的配位环境; NiO在经 TiO2改性后的γ-Al2O3载体上的分散容量。结果表明：（ 1） TiO2在γ-Al2O3表面的分散容量约为 0.62 mmol/100m2γ-Al2O3,当 TiO2含量低于该分散容量时 Ti4＋在γ-Al2O3载体表面以嵌入形式呈离子态分布;而含量高于分散容量时还有结晶态的 TiO2出现。（ 2） NiO在 TiO2/γ-Al2O3载体表面的分散容量约为 1.1 mmol/100m2γ-Al2O3,比之在γ-Al2O3载体表面的分散容量 (1.5mmol/100m2γ-Al2O3)要低,这是由于γ-Al2O3表面上部分空位被 Ti4＋离子占据。用表面相互作用的“嵌入模型” (Incorporation Model）讨论了这些结果。     

Enhanced catalytic performance for direct synthesis of dimethyl ether from syngas over a La2O3 modified Cu-ZrO2/γ-Al2O3 hybrid catalyst

A series of hybrid catalysts were made by physically mixing Cu-ZrO 2 and γ-Al 2 O 3,for former it was modified with different loadings of La 2 O 3 prepared by co-precipitation method.The catalysts were characterized by BET,XRD,N 2 O-adsorption,EXAFS,H 2-TPR,NH 3-TPD techniques and evaluated in the synthesis of dimethyl ether from syngas.The results show that La 2 O 3 promoted catalysts displayed a significantly better catalytic performance compared with Cu-ZrO 2 /γ-Al 2 O 3 catalyst in CO conversion and DME selectivity,and the optimum catalytic activity was obtained when the content of La 2 O 3 was 12 wt%.The characterizations reveal that high copper dispersion,facile reducibility of copper particles and appropriate amount of acidic sites are responsible for the superior catalytic performance.     

Metathesis of Butylene-2 and Ethylene to Propylene over 3.0Mo/(Hβ+ γ-Al203) Catalysts with Different γ-Al203 Contents

A series of 3. 0Mo/(Hβ γ-Al2O3) samples with γ-Al2O3 contents in the range of 0-100% (mass fraction) was studied by means of XRD, NH3-TPD, TPR and BET determinations for characterizing their structures. The Hβ zeolite structure in the 3. 0Mo/Hβ sample can be effectively stabilized by adding some γ-Al2O3to Hβ zeolite. γ-Al2O3 mainly favors the formation of polymolybdate or multilayered Mo oxide, while Hβmainly forms the Al2(MoO4)3 species, as evaluated by the TPR technique. When used as the catalyst for the metathesis of butylene-2 and ethylene to propylene, there exists a close correlation between the specific surface area and stability of the catalyst. The specific surface area of the catalyst shows the maximum when (Hβ γ-Al2O3) contains 30%γ-Al2O3, which is in agreement with that of the time needed for the reaction stablization. In the case of maximum surface area, the rate of coke deposition is the minimum.     

Metathesis of Butylene-2 and Ethylene to Propylene over 3.0Mo／（Hβ＋γ-Al2O3） Catalysts with Different γ-Al2O3 Contents

A series of 3. OMo/(Hβ γ-Al2O3) samples with γ-Al2O3 contents in the range of 0-100% (mass fraction) was studied by means of XRD, NH3-TPD, TPR and BET determinations for characterizing their structures. The Hβ zeolite structure in the 3.0Mo/Hβ sample can be effectively stabilized by adding some γ-Al2O3 to Hβ zeolite. γ-Al2O3 mainly favors the formation of polymolybdate or multilayered Mo oxide, while Hβ mainly forms the Al2(MoO4)3 species, as evaluated by the TPR technique. When used as the catalyst for the metathesis of butylene-2 and ethylene to propylene, there exists a close correlation between the specific surface area and stability of the catalyst. The specific surface area of the catalyst shows the maximum when (Hβ γ-Al2O3) contains 30%γ-Al2O3, which is in agreement with that of the time needed for the reaction stablization. In the case of maximum surface area, the rate of coke deposition is the minimum.     

Simultaneous removal of ethanol, acetaldehyde and nitrogen oxides over V-Pd/γ-Al_2O_3-TiO_2 catalyst

V-Pd/γ-Al2O3-TiO2 catalysts with different vanadium contents were prepared by a combined sol-gel and impregnation method. X-ray diffraction (XRD), N2 adsorption-desorption (BET), X-ray photoelectron spectroscopy (XPS) and catalytic removal of ethanol, acetaldehyde and nitrogen oxides at low temperature (<300 ?C) were used to assess the properties of the catalysts. The results showed that the sample with 1wt% vanadium exhibited an excellent catalytic performance for simultaneous removal of ethanol, acetaldehyde and nitrogen oxides. The conversions of ethanol, acetaldehyde and nitrogen oxides at 250 ?C were 100%, 74.4% and 98.7%, respectively. V-Pd/γ-Al2O3-TiO2 catalyst with 1 wt% vanadium showed the largest surface area and higher dispersion of vanadium oxide on the catalyst surface, and possessed a larger mole fraction of V4+ species and unique PdO species on the surface, which can be attributed to the strong synergistic effect among palladium, vanadium and the carriers. The higher activity of V-Pd/γ-Al2O3-TiO2 catalyst is related to the V4+ and Pd2+ species on the surface, which might be favorable for the formation of active sites.     

Pd/γ-Al_2O_3催化剂催化氧化邻-二甲苯

利用纳米γ-Al_2O_3(10 nm)和普通γ-Al_2O_3(200-300 nm),采用浸渍法制备了1%(w)Pd/γ-Al_2O_3催化剂,考察了其催化氧化邻-二甲苯的性能以及催化剂的活性在氢气还原前后的区别。实验结果发现1%(w)Pd/γ-Al_2O_3(nano)在H_2还原后催化氧化邻-二甲苯的活性最高,T_(90)为150℃。利用X射线衍射(XRD)、比表面积(BET)、透射电镜(TEM)、X射线光电子能谱(XPS)等表征手段,研究了1%(w)Pd/γ-Al_2O_3催化剂物性结构与催化性能之间的构效关系。结果表明,还原态Pd是H_2还原后催化剂催化氧化邻-二甲苯的活性物种;Pd的颗粒大小与催化剂活性有显著的关系,小粒径有利于催化剂活性提高;纳米γ-Al_2O_3载体与Pd之间的相互作用强,有利于Pd的粒径控制和分散,从而提高1%(w)Pd/γ-Al_2O_3(nano)催化剂的活性。     

ESR Characterization and Activity of V_2O_5/γ-Al_2O_3 Catalysts for Dehydrogenation of Isobutane

IntroductionIsobutene is the raw material for theproduction of many important chemicals.Thedehydrogenation of isobutane to isobutene oncatalysts Cr2 O3/γ- Al2 O3and Pt/γ- Al2 O3have beenextensively studied and successfully applied inindustry[1,2 ] .The dehydrogenation of isobutane to isobuteneis an endothermic reaction and is limited by thechemical equilibrium.Coke is easy formed on thecatalyst surface and the catalyst is frequentlyregenerated in the running.The oxidativedehydrogenation …     

FRACTAL ANALYSIS OF CATALYST NiO/α-Al_2O_3

We found that the Freundlich formula H=kC~(ln)can be used todescribe the isothermal adsorption curve of support α-Al_2O_3 with fractalstructures in nickel nitrate solutions.where n is relative to the surface fractaldimension D of α-Al_2O_3.     

助剂对WN_x/TiO_2-γ-Al_2O_3催化剂物化性质及加氢脱硫性能影响

在H2和N2混合气中,采用程序升温还原氮化反应的方法,合成了分别含有助剂Ni,Co,P或V的WNx/TiO2-γ-Al2O3催化剂.通过低温氮物理吸附、氨程序升温脱附、TG-DTA和X光电子能谱技术对所合成的催化剂进行了表征.实验结果表明,4种助剂的引入分别使WNx/TiO2-γ-Al2O3催化剂前驱体更易于还原氮化以...     

Theoretical studies of adsorption property on Ir_4/MgO and Ir_4/γ-Al_2O_3

The adsorption properties of atomic and molecular species on Ir4/MgO and Ir4/γ-Al2O3 have been systematically studied by means of planewave density functional theory(DFT)calculations using the periodic boundary conditions.The binding energies of these species were ordered as follows:H2O相似文献   

微量吸附量热法测定负载型固体碱催化剂K_2O/γ-Al_2O_3的表面碱性

以 CO2 作探针分子 ,采用微量吸附量热法测定负载型固体碱 K2 O/γ- Al2 O3 的表面碱性。试验结果表明 ,样品表现了很强的碱性 ,起始 CO2 微分吸附热为 1 60 k J· mol-1,饱和 CO2 覆盖度为 550μmol· g-1,碱性强于纯 Mg O。     

TiO_2-Al_2O_3复合载体的制备及Co-Mo/TiO_2-Al_2O_3催化剂加氢脱硫性能的研究

通过改进的溶胶-凝胶法(SG)、共沉淀法(CP)、表面沉淀法(PR)及混捏法(ME)制备TiO_2-Al_2O_3复合载体,考察了不同制备方法对复合载体物理性质的影响。采用浸渍法制备Co-Mo/TiO_2-Al_2O_3-X加氢脱硫催化剂,研究了Co-Mo/TiO_2-Al_2O_3-X加氢脱硫催化剂的脱硫性能。利用XRD、BET、SEM等表征手段对复合载体及催化剂进行表征分析。结果表明,SG法制备的复合载体粒径均一,具有较大的比表面积、孔径和孔体积;CP法制备复合载体时TiO_2以单层或亚单层的分散状态高度分散于γ-Al_2O_3中。在氢气压力3.0 MPa、反应温度280℃、反应时间4 h、液时空速1.4 h-1和氢油比600的条件下,SG法制备的Co-Mo/TiO_2-Al_2O_3催化剂具有较高加氢脱硫活性,噻吩转化率达到96.6%。     

Surface Acidity/Basicity and Catalytic Reactivity of CeO2/7-Al2O3 Catalysts for the Oxidative Dehydrogenation of Ethane with Carbon Dioxide to Ethylene

Dehydrogenation of ethane to ethylene in CO2 was investigated over CeO2/γ-Al2O3 catalysts at 700℃ in a conventional flow reactor operating at atmospheric pressure. XRD, BET and microcalori-metric adsorption techniques were used to characterize the structure and surface acidity/basicity of the CeO2/γ-Al2O3 catalysts. The results show that the surface acidity decreased while the surface basicity increased after the addition of CeO2 to γ-A12O3. Accordingly, the activity of the hydrogenation reaction of CO2 increased, which might be responsible for the enhanced conversion in the dehydrogenation of ethane to ethylene. The highest ethane conversion obtained was about 15% for the 25%CeO2/γ-Al2O3. The selectivity to ethylene was high for all the CeO2,γ-A12O3 and CeO2/γ-Al2O3 catalysts.     

CH_4、CO_2与O_2制合成气用Ni-Ce/γ-Al_2O_3催化剂的制备与催化活性的关系

利用 DTA-TGA、TPR、XRD和 XPS等表征手段 ,对用不同方法制备的催化剂进行表征 ,并结合催化剂的活性评价结果 ,研究 Ni-Ce/γ-Al2 O3催化剂的制备方法与催化活性的关系 .结果表明 ,无论浸渍法或共沉淀法制备的催化剂 ,都具有较高的 CH4转化活性 .这说明在反应过程中甲烷的活化仅与催化剂表面存在Ni物种相关 ,而与催化剂上 Ni Al2 O4的还原程度关系不大 .但对于 CO2 的活化 ,共沉淀法制备的催化剂 ,在高温还原预处理和反应过程中 ,晶型不完整的 Ni Al2 O4所还原生成的新鲜态的、低价 Ni物种 ,具有较强的活化能力 .因此共沉淀法制备的催化剂较浸渍法制备的催化剂具有更高的 CO2 的转化率和 CO的收率     

Fe_2(SO_4)_3/γ-Al_2O_3固体超强酸的Mssbauer谱研究

采用浸渍法制备了一系列Fe2SO43/γAl2O3型固体超强酸样品用Mssbauer谱和XRD研究了不同温度处理对样品中铁组分的存在状态及稳定性的影响结果表明随Fe2SO43含量的变化铁组分可以在γAl2O3表面以单层分散和无定形形式存在当温度≥600℃时无定形状态的Fe2SO43又生成晶态的Fe2SO43而形成的晶态Fe2SO43即使在700℃时也不分解。