Preparation of γ-Al_2O_3 via Hydrothermal Synthesis Using ρ-Al_2O_3 as Raw Material for Propane Dehydrogenation

γ-Al_2O_3 was prepared by hydrothermal synthesis using ρ-Al_2O_3 and urea as raw materials.In this work,the effects of the molar ratio of CO(NH_2)_2/Al and reaction temperature were investigated,and a Pt-Sn-K/γ-Al_2O_3 catalyst was prepared.The ammonium aluminum carbonate hydroxide(AACH),γ-Al_2O_3,and Pt-Sn-K/γ-Al_2O_3 were characterized by X-ray diffraction,scanning electron microscopy,transmission electron microscopy,N_2 adsorption-desorption,thermogravimetry-differential thermal analysis,and NH3 temperature-programmed desorption techniques.The reactivity of Pt-Sn-K/γ-Al_2O_3 for propane dehydrogenation was tested in a micro-fixed-bed reactor.The results show that γ-Al_2O_3 with a specific surface area of 358.1 m~2/g and pore volume of 0.96 cm~3/g was obtained when the molar ratio of CO(NH_2)_2/Al was 3:1 and the reaction temperature was 140℃.The alumina obtained by calcination of AACH has a higher specific surface area and larger pore volume than the industrial pseudo-boehmite does.The catalyst prepared from AACH as precursor showed high selectivity and conversion,which can reach 96.1 % and 37.6%,respectively,for propane dehydrogenation.     

γ-Al_2O_3的制备

氧化铝是两性氧化物,它既溶于酸又溶于碱,但买来的氧化铝粉末是属α-Al_2O_3,它不溶于酸和碱,因此无法用实验来验证它的两性。只有γ-Al_2O_3它疏松能溶于酸和碱,能验证氧化铝的两性。现将γ-Al_2O_3制备方法介绍如下:     

Preparation of nanometer γ-Fe2O3 by electrochemical oxidation in non-aqueous medium

1IntroductionThe synthesis and characterization of nano-struc-tured materials are the subject of intense current re-search.Hyperfineγ-Fe2O3particle with good perfor-mance,such as magnetism,catalysis,gas-sensitivityand so on,are widely applied in various fields[1].It ishighly significant to research and develop the methodsfor synthesis of nanometerγ-Fe2O3.With the development of nano-science and nano-technology,the methods for preparation ofγ-Fe2O3have been greatly progressed,for example,…     

Preparation of γ-Al2O3 ultrafine particles and its application in hydrogen peroxide biosensor

In this article, we illustrated the preparation method of γ-Al₂O₃ ultrafine particles. The particle size and morphology were decided by a transmission electron microscopy (TEM) and crystal patterns were determined by an X-ray diffractometer (XRD). γ-Al₂O₃ ultrafine particles have ultra characters in physics and chemistry, and the hydrogen peroxide biosensors based on it display not only fast response and high sensitivity, but also good stability.     

Agglomeration Control of Ultrafine Y_2O_3-ZrO_2 and (MgO, Y_2O_3)-ZrO_2 Powders Synthesized by Coprecipitation Process

TheadventofstrongandtoughZrO2 basedce ramicshasgeneratedconsiderablescientificandtech nologicalinterestinthisclassofstructuralceram ics[1—3]. Nowfine grainedsinteredceramicscanbeproducedusingcommerciallyavailableultrafinepow ders,whichcanbesinteredtofulldensityatrelativelylowtemperatures. High qualityZrO2 powderisvitalforthesuccessfuldevelopmentofadvancedZrO2 ce ramics. Severalwetchemicalmethodshavebeende velopedforpreparationofsuchhigh purity, homoge neousandsinterableceramicspowders,…     

In_2O_3 Ultrafine Powder Synthesis by Sol0Gel Method

1　Ｉｎｔｒｏｄｕｃｔｉｏｎ　Ｔｈｅｓｅｎｓｉｎｇｕｎｉｔｏｆｃａｒｂｏｎｍｏｎｏｘｉｄｅｉｓｃｒｉｔｉｃａｌｌｙｉｍｐｏｒｔａｎｔｆｏｒｓａｆｅｔｙｃｏｎｔｒｏｌｉｎ ｇａｓａｐｐｌｉｃａｔｉｏｎｓ ,ｂｅ ｃａｕｓｅｉｎｃｏｍｐｌｅｔｅｃｏｍｂｕｓｔｉｏｎｏｆｇａｓｅｓｃａｎｃａｕｓｅｓｅｒｉ ｏｕｓＣＯ ｐｏｓｏｎｉｎｇ .Ｄｅｖｅｌｏｐｍｅｎｔｏｆａｓｏｌｉｄ ｓｔａｔｅＣＯｓｅｎｓｏｒｉｓｔｈｅｒｅｆｏｒｅｄｅｓｉｒａｂｌｅｆｏｒｇａｓａｐｐｌｉｃａｔｉｏｎｓ .Ｉｎｉｎｃｏｍｐｌｅｔｅｃｏｍｂｕ…     

TiO_2调变对MoO_3/γ-Al_2O_3和CoO-MoO_3/γ-Al_2O_3表面结构及还原性能的影响

采用气相流动吸附法制ＴｉＯ２／γ－Ａｌ２Ｏ３复合载体,浸渍法担载一定量ＭｏＯ３或ＣｏＯ－ＭｏＯ３．用ＸＲＤ,ＬＲＳ和ＴＰＲ等技术考察了Ｍｏ或Ｃｏ－Ｍｏ催化剂的表面结构和还原性能．结果表明,覆盖在γ－Ａｌ２Ｏ３上的ＴｉＯ２能减弱ＭｏＯ３与γ－Ａｌ２Ｏ３之间的相互作用,明显改善Ｍｏ催化剂的表面结构,促进ＭｏＯ３的还原,适量ＣｏＯ助剂的加入能促进ＭｏＯ３在载体表面的分散．     

Morphology and Structure Analyses of SnO2 Thin Film Coated on Al2O3 Ultrafine Particles by Gas Phase Reaction in Fluidized Bed

１　Ｉｎｔｒｏｄｕｃｔｉｏｎ　Ｔｉｎｄｉｏｘｉｄｅｆｉｌｍｓｈａｖｅｂｅｅｎｗｉｄｅｌｙｕｓｅｄａｓｃｏｎｄｕｃｔｉｖｅｅｌｅｃｔｒｏｄｅｓ,ｔｒａｎｓｐａｒｅｎｔｃｏａｔｉｎｇｓ,ａｎｄｈｅｔｅｒｏｊｕｎｃｔｉｏｎｓｏｌａｒｃｅｌｌｓ．ＳｎＯ２ｆｉｌｍｓｗｉｔｈｄｉｆｆｅｒｅｎｔｓｔｒｕｃｔｕｒｅｓｃａｎｂｅｃｏｎｓｔｒｕｃｔｅｄｂｙｃｈｅｍｉｃａｌｖａｐｏｒｄｅｐｏｓｉｔｉｏｎｏｎｓｕｂｓｔｒａｔｅｓｏｆｄｉｆｆｅｒｅｎｔｔｅｍｐｅｒａｔｕｒｅｓ．ＡｂｏａｆａｎｄＭａｒｃｏｔｔｅ［１］ｐｒ…     

Research on Gelcasting Formation of SiC-Al_2O_3-Y_2O_3-La_2O_3 Systems

Siliconcarbide (SiC)ceramicmaterialsareusefulad vancedmaterialsinmanyfields,suchasmedicalbiomateri als ,hightemperaturesemiconductors ,synchrotronopticalel ementsandhighstrength /lightweightstructuralmaterials[1] .However,theactualapplicationisstilllimitedduetoitslowreliability ,highmachiningcosts[2 ] .Gelcastingprovidesane conomicalandfeasiblenet shape forminghomogeneousandflawlessgreenbodieswithcomplexgreenshapes.　　Gelcastingconsistsofin situpolymerizationthroughwhichamacromolecularnetwor…     

NiO-MoO_3/γ-Al_2O_3还原性能及动力学研究

用热重分析法研究了NiO-MoO3／γ-Al2O3的恒温和变温还原性能,求出了还原反应动力学参数,得到了还原反应动力学方程     

超声辅助SiO_2-Al_2O_3催化合成乙酰水杨酸工艺研究

以水杨酸和乙酸酐为原料,环己烷为溶剂,SiO_2-Al_2O_3为催化剂合成乙酰水杨酸.最佳实验条件为:水杨酸与乙酸酐摩尔比为1∶3.5,SiO_2-Al_2O_3用量为水杨酸摩尔分数的8.4%,反应时间20 min,反应温度75℃,溶剂用量为水杨酸摩尔分数的14.9%,超声功率为90 W,乙酰水杨酸收率可达93.9%.催化剂重复使用5次后仍有较高催化活性.该法较传统方法催化效果更好,无腐酸排放,不腐蚀设备,后处理工艺简单,催化剂重复利用率高、易再生,是一种绿色高效合成乙酰水杨酸的方法 .     

TiO_2调变对催化剂MoO_3/γ-Al_2O_3催化性能的影响

采用气相流动吸附法制ＴｉＯ２／γ－Ａｌ２Ｏ３复合载体，浸渍法担载一定量ＭｏＯ３．用ＸＲＤ，ＴＰＲ方法考察了ＭｏＯ３的分散状态，中压固定床反应装置测定催化剂的噻吩加氢脱硫和环己烯加氢活性．结果表明，ＴｉＯ２的加入能减弱ＭｏＯ３与γ－Ａｌ２Ｏ３间的相互作用，促进ＭｏＯ３的还原，提高催化剂的加氢脱硫活性．     

Preparation of Vitamin E Intermediate from an Inexpensive Substrate by Selective Oxidation of Pseudocumene in HCOOH–H_2O_2 System

In this paper, 2,3,5-trimethyl-1,4-benzoquinone(TMBQ) was synthesized through the direct oxidation of1,2,4-trimethylbenzene(pseudocumene, TMB) in the HCOOH–H_2O_2 system. The influence ofthree active species was studied, including performic acid(PFA) generated in formic acid, peracetic acid(PAA) generated in acetic acid, and trifluoroperacetic(TFPA) acid generated in trifluoroacetic acid. The effects ofsulfuric acid and sodium formate addition were investigated, the overoxidation ofTMB was discussed, and the main reason for the decreasing selectivity was revealed. The oxidation ofTMB can be controlled and improved through adjusting the reaction temperature, mole ratio ofoxidant to substrate, and reactant concentration. The TMBQ yield of28% was achieved with a TMB concentration of0.2 mol/L, H_2O_2/TMB mole ratio of6:1, and reaction temperature 37 °C. The selectivity of72% was obtained with a TMB concentration of0.2 mol/L, H_2O_2/TMB mole ratio of5:1, and reaction temperature of27 °C. The reaction mechanisms were proposed and discussed based on the gas chromatography–flame ionization detection(GC–FID) and gas chromatography–mass spectrometer(GC–MS) results.     

Mn-Fe/γ-Al_2O_3的制备与NO催化氧化性能

以锰铁为活性中心,γ-Al2O3为载体,采用等体积浸渍法合成了Mn-Fe/γ-Al2O3催化剂,考察了负载量、锰铁比及碱中和等对NO催化氧化活性的影响。结果发现,当反应温度为300℃、入口NO浓度为300 mmol/L、O2浓度为5%及空速为12 000 h-1时,以负载量为20%,Mn/Fe=1及(CH3)4NOH进行碱中和所制得的催化剂转化率最高,为66%,而其他制备条件所获得的催化剂都低于此值。通过对催化剂进行XRD、SEM表征,考察了负载量及碱中和对催化剂物相结构及表面形貌的影响。结果表明,随着负载量的增加,样品晶相不断分离,Fe2O3及MnO2的衍射峰逐渐尖锐,即活性组分进入载体孔道内部。另外,浸渍过程的碱中和操作有利于提高颗粒表面的分散度及形成无定形态。     

基于γ-Al_2O_3-ZrO_2-ThO_2的Pd基催化剂载体制备及应用

设计了一种用于负载型Pd基催化剂的γ-Al_2O_3-ZrO_2-ThO_2纳米管阵列载体。原位生长法制备的纳米孔Al_2O_3陶瓷模板经化学沉积形成γ-Al_2O_3-ZrO_2-ThO_2纳米载体,并以此纳米载体作为活性组分制备了具有高催化氧化活性的Pd催化剂。电镜结果表明,催化剂组分Pd能够均匀分散于纳米载体中。实验表明采用以γ-Al_2O_3-ZrO_2-ThO_2纳米材料为Pd基催化剂载体的CH4传感器具有较好的线性度和快速响应特性。     

Effect of Ultrafine Particles on Flow Field and Transport Properties near the Interface Around a Moving Bubble

Laser Doppler Anemometer has been used to measure the flow field characteristics near the interface around a moving bubble in the presence of ultrafine particles. In order to model a moving bubble, the bubble was fixed into the counter-flow liquid by a metal mesh. Experimental materials are air and water, and the particles are complex oxidate powder. Experiments were carried out under the operating conditions: the liquid flow velocity u0 is 12.6cm/s, the equivalent diameter de is 0.6cm, the mass concentration of particle is 0.2%,the average particle diameter is about 10nm and the density is 2g/cm^3. The velocity profiles of beth frontal and tail-vortex areas were measured respectively. The experimental results show that the velocity fields are obviously changed in the existence of particles. In the frontal area of the bubble, beth tangential and normal velocities decrease due to the presence of particles, but in tail vortex area, the tangential velocities increase remarkably,and normal velocities rise gradually from the center towards the fringe in the opposite tendency to that of no partitles. The influences of flow field change in the presence of particles on gas-liquid mass transfer are analyzed and discussed.     

Ce_(0.6)Zr_(0.4)O_2/γ-Al_2O_3复合粉体的制备及其结构研究

以氯氧化锆、硝酸铈、硝酸铝为原料,采用化学沉淀法在经过扩孔处理的γ-Al2O3基载体上制备出Ce0.6Zr0.4O2/γ-Al2O3复合粉体。为有效去除水分,减少粉体团聚,采用正丁醇与粉体共沸蒸馏。采用XRD技术对所得粉体的晶型及相结构进行了表征。结果表明:Ce0.6Zr0.4O2/γ-Al2O3复合粉体中CeO2为立方晶型,随着焙烧温度的升高,样品的衍射峰依次变强,半高宽变窄,说明晶粒变大,晶体的完整性变好。     

Preparation of Long Afterglow Photoluminescent Material SrAl_2O_4:Eu~(2+), Dy~(3+) and Its Luminescent Property

Thelongafterglowphotoluminescentmaterialshavebeenstudiedforalongtime.Thephotoluminescentmaterialscouldbeusedinmanyfields,forexample,asluminouspaintsinhighway,railway ,airport,ferry,andonthefacadeofbuildings.ZnS basedmaterialsdopedwithCuorMnwerefirstpreparedandappliedtovariousfields.However,theywerenotstableenoughformanyapplicationsandcouldonlymaintaintheirphosphores cenceforafewhours.Comparedwithsulfidephospho rescentphosphors,aluminates based phosphorsshowedexcellentphotoresistanceandchemic…     

Y-TZP/α-Al_2O_3复相陶瓷凝胶注模成型工艺的研究

研究了Y-TZP/α-Al2O3复相陶瓷,在低粘度高固相体积分数浓悬浮体时的凝胶注模成型制备工艺.利用自制分散剂PA对Y-TZP、α-Al2O3进行表面吸附修饰改性,通过PA对两种颗粒的电空间稳定机制,在pH=9.5及最佳分散剂用量条件下制得低粘度高固相量的Y—TZP/α—Al2O3复相陶瓷悬浮体.