Calorimetric study of the acidic character of V<Subscript>2</Subscript>O<Subscript>5</Subscript>–TiO<Subscript>2</Subscript>/SO<Subscript>4</Subscript><Superscript>2−</Superscript> catalysts used in methanol oxidation to dimethoxymethane

The surface acidic properties of sulfated vanadia–titania catalysts prepared by various methods were investigated by adsorption microcalorimetry, using ammonia as probe molecule. The acidic characteristics of the samples were shown to be strongly affected by the preparation method, calcination temperature, and sulfur content. The samples prepared by sol–gel and mechanical grinding exhibited higher acidity than co-precipitated samples. Moreover, increasing the calcination temperature of co-precipitated samples resulted in a decrease in surface area from 402 to 57 m² g⁻¹ and sulfur content from around 4 to 0.2 mass%, but up to a certain point generated a stronger acidity. The optimal calcination temperature appeared to be around 673 K.     

Synthesis and photocatalytic properties of materials based on bismuth silicates

The influence of the preparation technique of bismuth silicate-based catalysts on their formation, phase composition, absorption characteristics, and photocatalytic properties is investigated. Samples the with initial ratio of Bi: Si = 2: 1 are prepared via the hydrothermal method with varied temperature conditions in the hydrothermal aging and calcination stages. The synthesized catalysts demonstrate photocatalytic activity in the decomposition of the methanol equilibrium vapor and visible light-induced decolorization of a methylene blue (MB) aqueous solution.     

Promoter Effect of Potassium on an Iron Catalyst in the Carbon Dioxide Hydrogenation Reaction

Catalysts containing copper, zinc and aluminium oxides are used extensively in hydrogenation reactions, low temperature water-gas shift and low pressure methanol synthesis processes. In the present study, the effects of certain pertinent preparation parameters on catalysts' activity have been studied, applying the saturated fractional factorial experimental design method. The influence of time and temperature of calcination, aging time, the method of mixing of reactant solutions, the nature of the precipitant and the molar ratio of the latter to metal nitrates have been investigated. The catalysts prepared, using sodium carbonate showed higher activities relative to those synthesized by applying sodium hydrogen carbonate. Higher temperatures and longer time of calcination have profound effects on the activity of catalysts prepared, using sodium hydrogen carbonate. Shorter aging times and higher molar ratios of precipitant to metal nitrates promoted the activity of catalysts prepared by sodium carbonate. In case of catalysts synthesized, using sodium hydrogen carbonate as the precipitant, the aging time should be maintained as short as possible in order the catalysts to acquire higher activities.     

Effect of the Sulfate Sulfur Content and the Preparation Procedure on the Catalytic Properties of Sulfated Zirconium Oxide

The effects of the composition and the procedure of preparing sulfated zirconium oxides on their catalytic properties in the reactions of 1-butene isomerization to 2-butenes and isobutanol dehydration were studied. The activity was found to depend on the nature of parent zirconium oxide, the sulfate sulfur content, and the temperature of calcination. Catalysts prepared from a crystalline oxide exhibited the highest activity. Their activity depends on the sulfate sulfur content. The calcination of catalysts at temperatures higher than 400°C resulted in a detectable loss of sulfate. The activity of sulfated oxides prepared from an amorphous oxide was noticeably lower; it depended only slightly on the temperature of calcination and sulfate sulfur content. The catalytic behavior of the sulfated oxide in both of the reactions is indicative of the absence of superstrong proton sites. Based on the results, assumptions on the nature of formed surface compounds were made.     

Fischer-Tropsch Catalysts Based on Zr-Fe Intermetallides Encapsulated in an Al2O3/Al Matrix

ZrFe and ZrFe₂ intermetallides in an Al₂O₃/Al cermet matrix are reported as catalysts for the fixed-bed Fischer-Tropsch synthesis, and the effects of some preparation conditions on their texture, structural, mechanical, and catalytic properties are discussed. A nonmonotonic dependence of their catalytic activity on the size of interametallide particles is observed. The selectivity, activity, and mechanical strength of the composites depend on the calcination temperature and on the place of the hydriding step in the catalyst preparation procedure. In terms of volumetric efficiency, the catalysts prepared are comparable with bulk, unencapsulated intermetallides and are among the most efficient iron-containing catalysts known to date.     

Ni／MgO／Al2O3催化剂中Ni前体对甲烷—二氧化碳重整反应活性的影响

考察了以硝酸镍、氯化镍、硫酸镍、醋酸镍及硝酸六氨合镍5种Ni盐制备的Ni/MgO/Al2O3催化剂在CO2与CH4重整制合成气反应中的催化活性,发现Ni前体对活性有明显的影响,以硝酸镍、醋酸镍、硝酸六氨合镍为前体制备的Ni催化剂,反应性较高;以硫酸镍为前体制备的Ni催化剂,可能由于硫中毒等原因而显示出很低的活性;以氯化镍为前体制备的 Ni催化剂,其活性与制备方法有关,未经烧而直接还原的催化剂显示出较好的活性,X－射线粉末衍射（XRD）、BET比表面积及反应后的积量测定结果表明,以硝酸镍、醋酸镍、硝酸六氨合镍为前体制备的Ni催化剂,表面分散性好,比表面积大,积炭量少。     

在铜铁、铜钴复合氧化物上利用CO低温催化还原NO

Copper iron composite oxides (CuO/Fe2O3) and copper cobalt composite oxides (CuO/Co3O4) for the catalytic reduction of NO with CO at low temperature were prepared by co-precipitation. The catalytic activity and thermal stability of the catalysts were evaluated by a microreactor-GC system. The 100% conversion temperatures of NO are 80 oC for CuO/Fe2O3 and 90 oC for CuO/Co3O4. The catalysts possess high catalytic activity and favorable thermal stability for NO reduction with CO in a wide temperature range and long time range. A systematic study of the molar ratios of the reactants, the volume of NaOH, aging time, and calcination temperature/time was carried out to investigate the influence preparation conditions on the catalytic activity of the catalysts.     

Silica - Titania Support for HVOC's Combustion Catalysts

Preparation of support series for catalysts of combustion of halogenated volatile organic compounds (H-VOC's) was carried out. It was stated that all they allow preparing active catalysts however their main drawback is the lack of hardness against products of H-VOC's combustion e.g. hydrogen chloride and chlorine. Laboratory tests showed that titania and silica - titania supports were characterized by the highest hardness against chlorine derivatives. In comparison to the titania supports, low content (ca. 10 wt.%) silica-containing supports have better mechanical properties, i.e. mechanical strength and attrition resistance. In this paper the method of preparation, composition and physicochemical properties of silica - titania support are presented. This revised version was published online in June 2006 with corrections to the Cover Date.     

Evaluation of titania as an ion-exchanger and as a ligand-exchanger in HPLC

Summary The chromatographic properties of titania have been compared with those of zirconia and alumina, by comparison of their relative Lewis acidities whenp-substituted benzoic acids were chromatographed with aqueous mobile phases. The retention behavior ofp-substituted benzoic acids on titania was found to be similar to that on zirconia; the slopes of plots of retention factors against solute pK _a were approximately parallel for all pH values and the slopes obtained were similar to the average slope for zirconia. The shapes of solute peaks on titania were more symmetrical than on alumina and zirconia. The effect of calcination temperature on the chromatographic properties of titania was examined by use of titania prepared at different temperatures. The results obtained clearly showed that the preparation temperature affected the chromatographic properties of titania. It seemed, for example, that titania dried at 40°C behaved as a cation-exchanger, titania heated at 200°C behaved as an amphoteric exchanger, and titania calcined at 600°C behaved as an anion-exchanger in the pH range 4.1–6.5 It was found that the control of the preparation temperature enabled us to make effective use of titania.     

多酸结构对纳米钛硅TS-1沸石催化氧化脱硫性能的影响

采用浸渍法合成了纳米钛硅TS-1沸石负载的钼系列多金属氧酸盐(POM)复合催化剂,采用扫描电子显微镜(SEM)、傅里叶红外光谱(FT-IR)、固体紫外漫反射(UV-Vis)、X-ray粉末衍射(XRD)、氮气吸附脱附(BET)、³¹P和²⁹Si魔角核磁共振(MAS-NMR)等对催化剂的结构进行表征。 研究结果表明,在低温焙烧或烘干条件下,负载后催化剂多酸的结构保持,钼酸铵高温(550 ℃)焙烧后转变为三氧化钼。 以有机硫化物噻吩(TH)、苯并噻吩(BT)和二苯并噻吩(DBT)的正辛烷溶液为模拟油品评价了催化剂的氧化脱硫性能。 实验结果表明,纳米TS-1沸石载体上不同结构多酸作为脱硫催化剂对硫化物的脱除活性顺序为:Keggin型Mo-POM＞Anderson型Mo-POM＞Dawson型Mo-POM＞Mo-金属氧化物。以上述负载的多酸为催化剂,在反应条件为:V(模拟油)=V(乙醇)=10.0 mL,m(催化剂)=0.2 g,n(H₂O₂)∶n(S)=10∶1,温度60 ℃,硫化物按照由易到难的脱除顺序为TH＞DBT＞BT,与常规的TS-1沸石或者多酸催化剂的脱除顺序存在明显差异。 这是纳米TS-1沸石对于有机硫分子氧化反应的择形效应和POM催化氧化脱硫的电子云密度影响综合作用的结果。 Keggin型Mo-POM催化剂具有良好的循环使用性能,是一类制备方法简单、催化活性高且稳定性好的绿色环保型催化剂。     

制备条件对异丁烯选择性氧化催化剂性能的影响

通过正交实验设计，改变钼酸铵溶液的质量分数、pH值和催化剂焙烧温度，利用共沉淀法制备了一系列Mo-Bi-Co-Fe-Ce-Cs-K复合氧化物催化剂。借助于BET、TG-DSC、XRD等分析方法对催化剂的物理化学性质进行了表征。在常压连续流动固定床反应器中，系统地考察了上述三种制备条件对复合氧化物催化剂催化异丁烯选择性氧化生成甲基丙烯醛反应性能的影响。结果表明，大比表面积的催化剂具有较高的活性，而平均孔径小的催化剂选择性较差。 催化剂的最佳制备条件为： 钼酸铵溶液的质量分数10%、 pH值2～3、 焙烧温度500 ℃。在异丁烯∶空气=6∶94（体积比）、GHSV=3 600 h－1和360 ℃条件下，异丁烯转化率87.2％，甲基丙烯醛选择性72.0％，甲基丙烯醛收率62.7％。     

Ca/Al固体碱催化菜籽油制备生物柴油

采用共沉淀法制备了Ca/Al复合氧化物固体碱催化剂,考察了沉淀剂种类、Ca/Al摩尔比、沉淀温度、溶液pH值、老化时间和焙烧温度等制备条件对其催化剂活性的影响。采用正交实验方法得到制备Ca/Al复合固体碱催化剂前躯体的最佳制备条件为,沉淀剂NaOH,Ca/Al摩尔比为3,沉淀温度为60 ℃,沉淀过程中pH值保持在10,在90 ℃老化18 h。在该最优条件下制备的催化剂前驱体主要以Ca₄Al₂O₆(NO₃)₂·10H₂O晶相存在,在N₂气保护下300 ℃焙烧2 h后,催化剂形成高分散钙铝复合氧化物,且碱性强度达到26.5以上。在催化菜籽油和甲醇的酯交换反应中,菜籽油的转化率达到95%,脂肪酸甲酯的质量分数为95.9%。     

Preparation of ordered mesoporous TiO2 thin film and its application in methanol catalytic combustion

Ordered mesoporous titania thin films were synthesized by evaporation induced self‐assembly process in the presence of Pluronic block copolymers P123 (EO₂₀‐PO₇₀‐EO₂₀). The influence of several experimental parameters, including aging humidity, aging temperature, substrate properties and methods for organic templates removal, on the mesostructure of titania thin films was investigated in details. The mesoporous titania thin film supported Pt catalyst was prepared, and its methanol catalytic combustion performance was studied. The results showed that mesoporous titania thin film is an active support for catalyst. Mesoporous titania thin film supported platinum catalysts yields 70% methanol conversion at room temperature and 100% conversion at 100 °C. Copyright © 2013 John Wiley & Sons, Ltd.     

WP/γ-Al2O3催化剂负载方式对噻吩加氢脱硫性能的影响

以γ-Al2O3为载体，分别采用机械混合法、共浸渍法、分步浸渍法和程序升温、高纯氢气还原无定型磷钨酸盐的方法，制备了活性组分为磷化钨，负载量为20%的WP/γ-Al2O3催化剂。考察了不同方法制备的催化剂对噻吩加氢脱硫（HDS）反应的催化活性。结果表明：不同负载方式对催化剂结构有一定影响，对噻吩加氢脱硫性能的影响在低温时较明显。采用机械混合方式，先混合后还原方法制备的催化剂其HDS活性比先还原后混合方法制备的催化剂高；采用共浸渍和分步浸渍方式，通过焙烧所形成的催化剂其HDS活性分别比不经焙烧所形成的催化剂高或接近；浸渍焙烧所形成的催化剂其HDS活性远远高于机械混合法制备的催化剂。     

Preparation and characterization of vanadium oxide deposited on thermally stable mesoporous titania

Vanadium oxide was deposited on mesoporous titania by the molecular designed dispersion method to investigate the potential properties of these catalysts. Mesoporous titania was synthesized following the evaporation-induced self-assembly (EISA) method with a subsequent treatment with ammonia to increase the thermal stability. As a result, the mesoporous titania obtained shows a high surface area (approximately 350 m2/g) and high stability. Vanadium oxide was deposited by the MDD method using a vanadyl acetylacetonate complex that was transformed into VOx after a controlled calcination in air flow at 300 degrees C. The mesostructure and porosity characteristics of titania remain even until the maximum V-loading was reached (0.4 mmol/g), as it was shown by N2 sorption measurements at -196 degrees C. The catalysts were characterized by chemical analysis, Fourier transform infrared-photoacoustic spectroscopy (FTIR-PAS), UV-vis diffuse reflectance (DR), and Fourier transform Raman spectroscopy. Raman spectra showed isolated V species for the different V-containing catalysts. Furthermore, UV-vis-DR revealed a higher contribution of polymeric species as the V loading increases. The VOx/mesoporous titania catalysts were highly active in the selective catalytic reduction of NOx. A high activity in the NO conversion was observed, which increases with increasing metal loading.     

Synthesis and activity measurement of some water-gas shift reaction catalysts

The effect of calcination temperature on the activity and some properties of low temperature water gas shift reaction catalysts has been investigated. The activities of catalysts have been determined using a fixed bed catalytic reactor. The following results may be deduced from the present study. 1. The catalysts' total surface area decreased with increasing calcination temperature, presumably due to the partial sintering of the catalysts particles. 2. The presence of an amorphous CuO phase within the structure of some catalysts may be related to the desirable conditions prevailing during synthesis of the latter. 3. Observation of a similar trend between the increase in copper crystallite particle size and enhancement of catalyst activities with increasing calcination temperature demonstrates the important contribution made by the copper crystallite phase to the overall activities of water gas shift reaction catalysts. This revised version was published online in June 2006 with corrections to the Cover Date.     

二氧化钛负载氧化物催化剂上CO的氧化反应

对浸渍法和共沉淀法制备以的各种ＴｉＯ２负载氧化物催化剂进行了活性组分的筛选,结果发现,两种方法得到的ＣｕＯ催化剂均具有优良的ＣＯ氧化催化性能。在此基础上,考察不同ＴｉＯ２载体,活性组分含量以及催化剂焙烧温度对其催化能力的影响。结果表明,具有高比表面、大孔体积的ＴｉＯ２载体负功的ＣｕＯ催化剂具有较好的催化性能,活性组分ＣｕＯ的最佳含量范围在１０％～１５％之间,催化剂最佳焙烧温度为４００℃。     

A laser Raman spectroscopy study of molybdenum oxide supported on alumina and titania

Molybdenum oxide supported on alumina and titania prepared by three different methods (impregnation, calcination and hydrothermal treatment of mechanical mixtures), have been studied by laser Raman spectroscopy. Different oxomolybdenum species have been detected depending on the method of preparation and on the calcination conditions. Heptamolybdate and polymolybdate species were found in the impregnated and in the uncalcined, hydrothermally treated samples supported on alumina and titania, respectively, whereas polymolybdate species were formed on the surface of alumina when the mechanical mixtures and the hydrothermally treated samples were calcined in the presence of water vapour. However, two kinds of species, polymolybdate and mono-oxomolybdenum, were found in the case of the mechanical mixtures and the hydrothermally treated samples calcined in the presence of water vapour when supported on titania.     

磷酸根改性的二氧化钛固体酸催化合成草酸二异戊酯

通过沉淀、老化、过滤、洗涤、干燥、浸渍和焙烧等过程,从TiCl4和H3PO4制备了磷酸根助催化的二氧化钛固体酸催化剂,用Hammett指示剂法、正丁胺滴定法、XRD和N2-吸附进行了表征,研究了(PO43-)的质量分数和焙烧温度对酸性、结构和催化性能的影响.XRD结果表明(PO43-)抑制晶粒长大.Hammett指示剂...     

制备高碳醇Cu-Fe系催化剂的比表面积、孔结构和孔径分布

用ＡＳＡＰ－２０００型物理吸附仪,研究了制备高碳醇Ｃｕ－Ｆｅ系催化剂的比表面积、孔结构、孔容积和孔径分布等．结果表明,随着焙烧温度的提高,比表面积下降;在相同的焙烧温度下,组成和沉淀过程的ｐＨ值也影响其表面积大小．催化剂的活性与反应可利用的表面积相关．根据吸附－脱附等温线,确定了催化剂的孔结构及孔径分布的变化规律．数据表明,孔径分布和孔容积对催化剂的活性至关重要,平均孔径（４Ｖ／Ａ,根据ＢＥＴ）可作为衡量Ｃｕ－Ｆｅ系催化剂活性高低的一个参数．焙烧温度的选择是使催化剂具有适宜的孔径分布和较大的孔容积,因而具有较高活性的重要条件