Vapour phase synthesis of isobutyraldehyde from methanol and ethanol over mixed oxide supported vanadium oxide catalysts

The vapour phase synthesis of isobutyraldehyde from methanol and ethanol in one step was investigated over titania-silica, titania-alumina, titania-zirconia, titania-silica-zirconia, and magnesia supported vanadium oxide catalysts at 623 K and under normal atmospheric pressure. Among various catalysts the titania-silica binary oxide supported vanadia provided higher yields than the other single or mixed oxide supported catalysts. The high conversion and product selectivity of V₂O₅/TiO₂-SiO₂ catalyst (20 wt% V₂O₅) was related to the better dispersion of vanadium oxide over titania-silica mixed oxide support in addition to other acid-base and redox characteristics. A reaction path for the formation of isobutyraldehyde from methanol and ethanol mixtures over these catalysts was described.     

Cs-Fe-Co-Bi-Mn-Mo复合氧化物选择性催化氧化异丁烯

Mixed oxide catalyst Cs0.1 Fe2Co6BiMnMo12 Ox was prepared by the interprecipitation method, then the catalyst was calcined at different temperature. Selective oxidation of isobutene was carried out in a fixed-bed reactor. The results showed that the catalyst has high catalytic activity. Under the optimum reaction conditions ( n(-C4^= ) : n(O2) = 1:2-1:4, space velocity = 180h^-1, T = 360℃ ), the yield of methacmlein and methacrylic reached 80%, 8 %,respectively. The total yields of liquid products( methacrolein, methacrylic acid and acetic acid) reached about 90%.     

Vapor phase synthesis of N-butylaniline over copper-based catalysts

Cu-based catalysts, such as Cu/SiO2, Cu/γ-Al2O3 and Cu/SiO2-Al2O3, for the vapor phase synthesis of N-butylaniline from aniline and 1-butanol were investigated and the catalysts were characterized by BET, H2-TPR, XRD and NH3-TPD techniques. The results indicated that the dispersion of copper on support was greatly influenced by the interaction between Cu and the support. Copper-based catalyst with larger amounts of acidic sites did not favor the synthesis of N-butylaniline because more by-products were prod...     

Oxidation of isobutane over hydrothermally synthesized Mo-V-Te-Nb-O mixed oxide catalysts

MoV_0.3Te_0.17 and MoV_0.3Te_0.17Nb_0.12 catalysts were prepared by a hydrothermal synthesis route and tested for the oxidation of isobutane and isobutene. Characterization results showed that the structure and property of Mo-V-Te-based catalysts are relatively different depending on the presence of the Nb element. Catalytic tests showed that the selectivity of methacrolein can comparatively be improved by the addition of Nb into the MoV_0.3Te_0.17 catalyst for the selective oxidation of isobutane.     

Styrene synthesis over iron oxide catalysts: from single crystal model system to real catalysts

Surface science methods originating from analysis of noble metal catalysts are increasingly applied to metal oxides. These methods provide direct access to fundamental structural properties and phase equilibria governing the catalytic properties of metal oxide surfaces. However, no systematic way existed so far for transferring this knowledge to technical catalysts. The aim of this paper is to combine surface science with chemical engineering methods to bridge this gap. Styrene synthesis over pure and K-doped iron oxides is used as an example to develop and to explain the methodology. Single crystal films (SCF), grown epitaxially on a Pt-carrier are considered as ideal model surfaces. Comprehensive UHV analyses yield the structural properties of SCF as well as their interaction with relevant components of the reaction mixture. Their results are combined with conversion experiments to derive a mechanistic catalyst model along with quantitative information on the reaction rates. The activity of SCF as well as their phase transitions under reactive conditions can be described with a continuum model depending on the macroscopic properties of the system. This model forms the crucial link towards technical catalysts. It is shown that the behaviour of a powder catalyst can be described as a superposition of the above kinetic model and an appropriate porous model. In this paper we review the developed methodology and conclude with the evaluation of the concept.     

Highly selective synthesis of 3-methylindole from glycerol and aniline over Cu/NaY modified by K2O

The vapor-phase synthesis of 3-methylindole from glycerol and aniline over Cu/NaY modified by K2O was investigated. The catalysts were characterized by X-ray diffraction （XRD） and the temperature- programmed desorption of ammonia （NH3-TPD）. The effect of the reaction temperature on the activity and selectivity of Cu]NaY-K2O catalyst was also investigated. The results indicated that the addition of K2O to Cu/NaY increased the selectivity of the catalyst remarkably because the amount of middle-strong acid sites decreased clearly. The decrease of the reaction temperature was beneficial for the increase of 3- methylindole selectivity. Over Cu/NaY-K2O, the selectivity of 3-methylindole reached 75% and the yield of the target product was up to 47% at 220 ℃. A probable catalytic mechanism for the synthesis of 3- methylindole from glycerol and aniline was proposed.     

CeO2 promoting allyl alcohol synthesis from glycerol direct conversion over MoFe/CeO2 oxide catalysts: morphology and particle sizes dependent

Research on Chemical Intermediates - MoFe-N, MoFe/c–CeO2, MoFe/p1–CeO2, and MoFe/p2–CeO2 (where N, c, and p stand for non-supported, nanocube, and nanoparticle) oxide catalysts...     

Zn-La复合氧化物催化剂用于甲醇与碳酸乙烯酯酯交换反应的研究

ZnO、La₂O₃和Zn-La复合氧化物催化剂用于甲醇与碳酸乙烯酯反应制备碳酸二甲酯和乙二醇。催化剂采用共沉淀法进行制备,并用BET、XRD、TG-DSC、CO₂-TPD和Hammett滴定等对催化剂进行表征。考察了Zn-La物质的量比、焙烧温度,反应条件（反应温度、反应时间、催化剂用量等）对催化剂活性的影响。结果表明,ZnLa复合氧化物物质的量比为2：1,焙烧温度为500℃时,催化剂表现了较好的催化效果。催化剂的活性与催化剂表面的碱性强度和碱量有关,碱量越多催化剂的活性越好。     

Pb-Pt/AC催化甘油一步法制备丙酮酸

生物质能具有绿色环保、可再生、来源广泛和安全性高等优点,成为当前的研究热点.作为生物柴油的主要副产物,甘油是一种重要的生物质平台化合物.甘油的高效利用,不仅能够获得重要的精细化学品及聚合物,也可以延长生物柴油的产业链,降低其生产成本,增加其市场竞争力.丙酮酸是一种弱有机酸,为生物体内葡萄糖分解代谢的中间产物,在生物能量代谢和物质代谢过程中起着重要的枢纽作用.同时,由于它同时含有羧基和酮羰基,具有很强的反应性,可参与多种化学反应,在化学工业中有广泛应用.目前,工业上主要采用酒石酸脱水脱羧法生产丙酮酸,丙酮酸收率可达50–55%,但生产过程需要消耗大量的KHSO4粉末,生产成本高,且高耗能高污染,不符合可持续发展的要求.因此,利用可再生资源甘油在温和条件下生产丙酮酸显现出良好的应用前景.目前,由甘油一步法获得丙酮酸仅可通过发酵法实现,但是其规模化生产存在效率低、废弃物污染等问题.因此,研究化学方法由甘油一步制备丙酮酸可行也十分必要.本课题组以Pt/AC或Cu-Pt/AC为催化剂进行甘油氧化制备乳酸的研究,所得产物中几乎未检出丙酮酸;当以Pb-Pt/C为催化剂进行乳酸脱氢氧化制备丙酮酸,可获得较高选择性的丙酮酸.因此,本文通过向Pt/AC催化剂中引入Pb助剂,以期调变甘油氧化的产物分布,从而获得相对高的丙酮酸选择性.通过浸渍-沉积沉淀法(Im-DP)制备了一系列不同Pb载量(1–7.0 wt%)的xPb-5Pt/AC-Im-DP催化剂,并采用不同方法制备了一系列5Pb-5Pt/AC催化剂,用于在温和条件下甘油选择性氧化制备丙酮酸反应中.结果表明,Pb载量和催化剂制备方法都对其催化活性有显著影响.当xPb-5Pt/AC-Im-DP催化剂中Pb载量为1%时,甘油转化率和丙酮酸选择性均较单金属5Pt/AC催化剂高,但当Pb载量继续升高至3%及以上时,甘油转化率明显下降.我们推测这与Pb3(CO3)2(OH)2物种的形成有关.采用该方法制备催化剂时,Pb载量宜为5.0 wt%.保持Pt和Pb载量均为5.0 wt%,采用共沉积沉淀(Co-DP)、共浸渍(Co-Im)、以及对催化剂进行500oC氩气焙烧等,制备了具有Pb3(CO3)2(OH)2物种、铂铅合金物种(PtPb和PtxPb)和两物种均没有的5Pb-5Pt/AC催化剂.通过评价它们的催化性能,进一步探究了Pb3(CO3)2(OH)2物种、铂铅合金物种、表面金属价态与催化剂活性的关系.实验表明,Pb3(CO3)2(OH)2和表面Pb0物种不利于甘油的转化,铂铅合金对甘油转化有一定的促进作用,对丙酮酸生成显现出明显促进作用.通过对Co-DP、Im-DP催化剂进行500oC氩气焙烧,能够除去Pb3(CO3)2(OH)2物种,同时形成铂铅合金.综上,本文在温和条件下,采用Pb-Pt/AC催化剂进行甘油选择性氧化制备丙酮酸反应.采用优化的方法制备的5Pb-5Pt/AC催化剂在90oC条件下反应10 h,丙酮酸收率可达18.4%,这是目前甘油一步法氧化制备丙酮酸的最高值.进一步优化反应条件、催化剂组成与结构,探索反应机理仍十分必要.     

The vapor phase oxidation of 2-ethylhexanal over oxide catalysts

The vapor phase oxidation of 2-ethylhexanal over a series of oxide catalysts has been studied at 373–623 K. Monolayer vanadia supported on SiO₂ and TiO₂, molybdena and tungstenia supported on SiO₂, and SnO₂ were used as the catalysts. In contrast to the liquid phase process, resulting in 2-ethylhexanoic acid, the main observed reaction was reactant combustion. The partial oxidation products were 3-heptanone, 3-heptyl formate, and heptene. No traces of 2-ethylhexanoic acid were detected in any of the transformations performed.     

Products distribution of glycerol hydrogenolysis over supported co catalysts in a liquid phase

The products distribution of glycerol hydrogenolysis over supported Co catalysts was evaluated in a liquid phase system. The effects of support type, temperature, pressure and reaction time on the conversion of glycerol as well as yield of desired products were investigated. The preliminary results indicated that various added compounds were generated in the presence of supported Co catalysts. The type of support and the reaction temperature, pressure and time significantly affected either the glycerol conversion or the product yield. The acidity of catalyst played a more important role in the glycerol hydrogenolysis over supported Co catalysts than the specific surface and pore volume. Among the utilized supported Co catalysts, Co/γ-Al₂O₃ exhibited the highest acrolein yield of about 31.1% at 70.5% conversion at 200°C, 8 MPa H₂ pressure and 6 h reaction time.     

Selective oxidation of propane to acrylic acid over mixed metal oxide catalysts

The effects of metal atomic ratio, water content, oxygen content, and calcination temperature on the catalytic performances of MoVTeNbO mixed oxide catalyst system for the selective oxidation of propane to acrylic acid have been investigated and discussed. Among the catalysts studied, it was found that the MoVTeNbO catalyst calcined at a temperature of 600 ℃ showed the best performance in terms of propane conversion and selectivity for acrylic acid under an atmosphere of nitrogen. An effective MoVTeNbO oxide catalyst for propane selective oxidation to acrylic acid was obtained with a combination of a preferred metal atomic ratio （Mo1V0.31Te0.23Nb0.12）. The optimum reaction condition for the selective oxidation of propane was the molar ratio of C3H8 ：O2 ： H2O ： N2 = 4.4： 12.8 ： 15.3 ： 36.9. Under such conditions, the conversion of propane and the maximum yield of acrylic acid reached about 50% and 21%, respectively.     

Correction to: CeO2 promoting allyl alcohol synthesis from glycerol direct conversion over MoFe/CeO2 oxide catalysts: morphology and particle sizes dependent

Research on Chemical Intermediates - In the original publication of the article, the chemical compounds “enthanal” and “propanal” were incorrectly published as...     

Selective oxidation of isobutane over Mo-V-Te mixed oxide catalysts with different tellurium contents

A series of MoV_0.3Te_x (x = 0−0.3) mixed oxides were prepared and investigated for the selective oxidation of isobutane. Among them, MoV_0.3Te_0.23 showed the best methacrolein and methacrylic acid selectivity (as high as 17% and 16%, respectively), and the yield to methacrolein and methacrylic acid reached 3.6% and 3.5%, respectively, at 21.3% isobutane conversion at 440°C.     

Catalytic ketonisation over oxide catalysts

Activity of pure Al₂O₃ has been studied in cycloketonisation of various dialkyl alkanodiates of general formula (CH₂)_n(COOR)₂, where n = 4, 5, 6, 7, 8 and 10 and R = Et, s-Bu and t-Bu at the temperature range 598-723 K in a flow system. The yields of cycloalkanones strongly depend on the size of the ring formed, the structure of alkyl group in ester molecule and on the reaction temperature. Cyclopentanone, cyclohexanone and cycloheptanone were obtained with yields 50-60% from the appropriate diethyl esters. The only low yields (<8%) of cyclooctanone, cyclononane and cycloundecanone were achieved. An increase in the order of the ester alkyl group leads in some cases to higher yields of ketones - di t-butyl hexanodiate yielded 88% of cyclopentanone. This revised version was published online in August 2006 with corrections to the Cover Date.     

Hydrogenolysis of glycerol over HY zeolite supported Ru catalysts

An enhanced active and selective catalyst consisting of ruthenium supported on dealuminated HY zeolite has been prepared by a wet impregnation method. It was found that BET surface area of Ru/HY catalysts significantly increases after HCl treatment. This treatment also increases the concentration of strong acid sites in the catalyst. The hydrogenolysis of glycerol over 5 wt% Ru/HY catalyst was investigated at 190-220 ℃, an initial H2pressure of 3-6 MPa, and in 20 wt% glycerol aqueous solution. The results indicate that HCl treated Ru/HY catalyst shows higher activity compared with the untreated Ru/HY catalyst, and that the glycerol hydrogenolysis efficiency is influenced by the porosity and acidity of the support. A selectivity to 1,2-PDO of 81.3% at a glycerol conversion of 60.1% under 3 MPa H2pressure and 220 ℃ for 10 h was achieved over the modified Ru/HY catalyst with a 1.0 mol/L HCl treatment. It has also been shown that a longer reaction time, a higher temperature and a higher H2pressure have the positive effects on the glycerol hydrogenolysis efficiency of the enhanced Ru/HY.     

Synthesis of glycerol carbonate from glycerol and urea with gold-based catalysts

The reaction of glycerol with urea to form glycerol carbonate is mostly reported in the patent literature and to date there have been very few fundamental studies of the reaction mechanism. Furthermore, most previous studies have involved homogeneous catalysts whereas the identification of heterogeneous catalysts for this reaction would be highly beneficial. This is a very attractive reaction that utilises two inexpensive and readily available raw materials in a chemical cycle that overall, results in the chemical fixation of CO(2). This reaction also provides a route to up-grade waste glycerol produced in large quantities during the production of biodiesel. Previous reports are largely based on the utilisation of high concentrations of metal sulfates or oxides, which suffer from low intrinsic activity and selectivity. We have identified heterogeneous catalysts based on gallium, zinc, and gold supported on a range of oxides and the zeolite ZSM-5, which facilitate this reaction. The addition of each component to ZSM-5 leads to an increase in the reaction yield towards glycerol carbonate, but supported gold catalysts display the highest activity. For gold-based catalysts, MgO is the support of choice. Catalysts have been characterised by XRD, TEM, STEM and XPS, and the reaction has been studied with time-on-line analysis of products via a combination of FT-IR spectroscopy, HPLC, (13)C NMR and GC-MS analysis to evaluate the reaction pathway. Our proposed mechanism suggests that glycerol carbonate forms via the cyclization of a 2,3-dihydroxypropyl carbamate and that a subsequent reaction of glycerol carbonate with urea yields the carbamate of glycerol carbonate. Stability and reactivity studies indicate that consecutive reactions of glycerol carbonate can limit the selectivity achieved and reaction conditions can be selected to avoid this. The effect of the catalyst in the proposed mechanism is discussed.     

Decarbonylation of furfural over oxide catalysts

Gas chromatography has been used to investigate the products accompanying tetrahydrofuran prepared by hydrogenation of furan, without isolating the latter pure from the gas mixture obtained by decarbonylating furfural over oxide catalysts. A number of unknown impurities accompanying tetrahydrofuran and furan, are identified. It is found that tetrahydrofuran contains isopropanol, along with furan,-methylfuran, and-methyltetrahydrofuran. Furan itself contains-methylfuran, and a number of unknown impurities, among them acetone. Ethane is found among the gaseous products of decarbonylation. Thus over Zn and Mn oxide catalysts there is joint hydrogenolysis of the furan ring, and ring opening at positions 1–5 and 3–4.     

Vapour phase oxidation of 4-methylanisole to anisaldehyde over V2O5 /MgO-Al2O3 catalysts

The vapour phase selective oxidation of 4-methylanisole to anisaldehyde was investigated over different V₂O₅ /MgO-Al₂O₃ catalysts at 673 K and normal atmospheric pressure. Among various catalysts investigated the 16 wt% V₂O₅ /MgO-Al₂O₃ catalyst provided good conversion and product selectivity. The MgO-Al₂O₃ mixed oxide was obtained by a co-precipitation method and V₂O₅ was impregnated from ammonium metavanadate. The MgO-Al₂O₃ support and various V₂O₅ /MgO-Al₂O₃ catalysts were characterized by means of X-ray diffraction, FT-infrared, electron spin resonance, scanning electron microscopy, ammonia and carbon dioxide chemisorption methods. The characterization results suggest that vanadia does not form layer structures on the support surface, instead interacts very strongly with the support, in particular with MgO, and forms amorphous compounds. The NH₃ and CO₂ uptake results provide an interesting information on the acid-base characteristics of these catalysts and correlate with their catalytic properties.     

Alcohol synthesis over bulk aluminium-nickel-copper based catalysts from syngas

The catalytic performance of bulk aluminium-nickel-copper based catalyst was investigated with regard to alcohol synthesis. It was shown that, in spite of forming methanol as the main product, these catalysts are promising for the production of higher alcohols. Higher activation temperature increased the production of higher alcohols. The change of the salt concentration decreased the selectivity, while the pH had basically no effect on the selectivity.