Methanol dehydration to produce dimethyl ether over g-Al2O3

Summary The kinetic data of about 150 points for methanol dehydration were obtained at the temperature of 240~270^oC, the GHSV of 25,000~120,000 (mL/g_cat./h) and under atmospheric pressure. The data were fitted into six plausible equations. The kinetic equation derived from the molecular adsorption of methanol on two sites fit the kinetic data best, however, that from the dissociative adsorption of methanol could not be safely ruled out. The activation energy of 114.7 kJ/mol for methanol dehydration on γ-Al₂O₃ was obtained from the kinetic analysis.     

The Catalytic Dehydrogenation of c2h6 to c2h4 under non-Oxidative Conditions over the 6cr/g-al2o3Catalyst

In the present paper, the catalytic dehydrogenation of C₂H₆ to C₂H₄ under non-oxidative conditions was investigated in a fixed-bed micro-reactor under ambient pressure at 823 - 923 K. The 6Cr/g-Al₂O₃ catalyst was found to be the best catalyst among the g-Al₂O₃, SiO₂, MCM41, MgO and Si-2 supported chromium oxide catalysts. The features of the 6Cr/g-Al₂O₃ catalyst for the reaction could be listed as follows: (1) At 823 - 923 K, the C₂H₄ selectivity of 92.5-78.6% at a C₂H₆ conversion of 9.5-29.8% could be obtained. (2) The catalyst had the good regeneration performance, i.e., could be regenerated by air repeatedly. (3) The main products were C₂H₄, CH₄, H₂ and coke. No carbon oxides were identified.     

Direct synthesis of dimethyl carbonate ?from CH3OH AND CO2 by H3PW12O40/CexTi1-xO2 catalyst

Summary Ce_xTi_1-xO₂ and H₃PW₁₂O₄₀/Ce_xTi_1-xO₂ catalysts were prepared using a sol-gel method, and applied to the direct synthesis of dimethyl carbonate from methanol and carbon dioxide. H₃PW₁₂O₄₀/Ce_xTi_1-xO₂ showed a better catalytic performance than the corresponding Ce_xTi_1-xO₂, due to the bifunctional catalysis of Br?nsted acid sites (provided by H₃PW₁₂O₄₀) and base sites (provided by Ce_xTi_1-xO₂). H₃PW₁₂O₄₀/Ce_0.1Ti_0.9O₂ showed the highest catalytic performance among the H₃PW₁₂O₄₀/Ce_xTi_1-xO₂ catalysts.     

On the reduction kinetics of coprecipitated NiO-Al2O3 and NiO-La2O3-Al2O3 catalysts

Summary Reduction kinetic studies reveal qualitative and quantitative information about reducible NiO species co in the nano-size, coprecipitated NiO-Al₂O₃ and NiO-La₂O₃-Al₂O₃ mixed oxides.      

Selective catalytic reduction of nitric oxide with propane over Ni-Al2O3: effect of Ni loading

Summary The SCR of NO by propane in excess oxygen was studied on a Ni-Al₂O₃ catalyst prepared by a coprecipitation method. The effect of Ni loading on the catalytic performance was studied and the optimal Ni loading was found to be 4 % (wt.%). Based on characterization results, highly dispersed nickel species in surface aluminate phase was regarded as the active site for NO reduction by C₃H₈ and NiO phase was the active site for C₃H₈ oxidation by oxygen.     

Temperature-programmed desorption/pulse surface reaction (tpd/tpsr) studies of CH4, C2H6, C2H4, and CO over a cobalt/MWNTs catalyst

Summary Temperature-programmed desorption (TPD) of CH₄, C₂H₆, C₂H₄, and CO and temperature-programmed pulse surface reactions (TPSR) of CH₄, C₂H₆, C₂H₄, CO, and CO/H₂ over a Co/MWNTs catalyst have been investigated. The TPD results indicated that CH₄ and C₂H₆ mainly exist as physisorbed species on the Co/MWNTs catalyst surface, whilst C₂H₄ and CO exist as both physisorbed and chemisorbed species. The TPSR results indicated that CH₄ and C₂H₆ do not undergo reaction between room temperature and 450^oC. Pulsed C₂H₄ can be transformed into CH₄ at 400 ^oC whilst pulsed CO can be transformed into CO₂ at 100 or 150^oC. In gaseous mixtures of CO and H₂ containing excess CO, the products of pulsed reaction were CH₃CHO and CH₃OH. When the ratio of CO and H₂ was 1:2, pulsed CO and H₂ were transformed into CH₃CHO, CH₃OH and CH₄. In H₂ gas flow, pulsed CO was transformed into a mixture of CH₃CHO and CH₄ between 200 and 250^oC and was transformed into CH₄ only above 250^oC.     

Carvone epoxidation by system “hydrogen peroxide-[Mn2L2O3][PF6]2 (L = 1,4,7-trimethyl-1,4,7-triazacyclononane)-carboxylic acid”: a combinatorial approach to the process optimization?

Summary Epoxidation of natural terpene (+)-carvone by the system consisting of a catalyst, oxalic acid (co-catalyst) and H₂O₂ (70% aqueous solution; oxidant) was studied and factorial design methods were applied for the optimization of this reaction. A dinuclear manganese(IV) complex [LMn(O)₃MnL](PF₆)₂ (L = 1,4,7-trimethyl-1,4,7-triazacyclononane) was used as a catalyst, and acetonitrile was employed as a solvent. An analysis by methods of the complete 2⁴ factorial design showed that an increase in the catalyst concentration gives a strong positive effect on the carvone conversion and selectivity. Hydrogen peroxide has a smaller positive effect on the conversion, but at high concentration, H₂O₂ leads to some decrease in the selectivity. An increase in the oxalic acid concentration has a beneficial effect on the conversion, but does not affect the selectivity.     

Study of CuO/Ce0.8Zr0.2O2 catalysts for low-temperature CO oxidation

Summary Copper oxide catalysts supported on Ce_0.8Zr_0.2O₂ were prepared via an impregnation method and characterized by XRD and H₂-TPR techniques. The catalytic activity of the samples for low-temperature CO oxidation was investigated by means of a microreactor-GC system. The influence of calcination temperature, calcination time and different CuO content on the catalytic activity was studied. TPR analysis indicated that well-dispersed CuO was responsible for the low-temperature CO oxidation. The results of the investigation showed that the calcination temperature and CuO loadings had larger influence than the calcination time.     

A facile synthetic route for the preparation of the Au/Mox/Al2O3 catalysts towards CO oxidation

Summary A new facile single-step synthetic route is reported for the preparation of Au/MO_x/Al₂O₃ catalysts. The preparation method has the merit of facility but leads to not only the simultaneous load of both gold source and MO_x precursor on Al₂O₃ support, but also the formation of Au/MO_x/Al₂O₃ with high gold loading ratio, high dispersion and high activity for CO oxidation.     

Oxidative dehydrogenation of crotonaldehyde overK2HPMo12O40catalyst

Summary The oxidative dehydrogenation of crotonaldehyde to furan and maleic anhydride was carried out over K₂HPMo₁₂O₄₀catalyst. A positive effect of water vapor on furan formation is explained by ability of the catalyst to isomerize 2E- to 2Z-crotonaldehyde.</o:p>     

Tmperature programmed techniques study on the nature of the oxidant in/on V2O5catalyst ?

Summary The nature of the oxidising species in/on a vanadium pentoxide (V₂O₅) catalyst has been studied using a combination of transient techniques: (i) Temperature programmed desorption (TPD), (ii) Temperature programmed reduction (TPR), (iii) Temperature programmed oxidation (TPO) and (iv) Temperature programmed reaction (TPRn). Chemisorbed oxygen was found not to exist on a fully oxidised V₂O₅ catalyst by TPD. The TPR in CO over V₂O₅ catalyst gave three peak maxima at 930, 982 and 1043 K, indicating that three types of kinetically different oxygen states exist in/on the catalyst. Reoxidation of the CO reduced V₂O₅ catalyst by N₂O resulted in the quantitative replacement of the lattice oxygen. A further reduction of the N₂O reoxidised catalyst gave a significantly different TPR profile compared to the original material suggesting that a less crystalline material had formed. The presence of phosphorus in (VO)₂P₂O₇ was found to labilise the lattice oxygen.     

Preparation and crystal structure of [Bi3I(C4H8O3H2)2(C4H8O3H)5]2Bi8I30 containing the novel polynuclear [Bi8I30] anion

Preparation and crystal structure of the novel compound [Bi₃I(C₄H₈O₃H₂)₂(C₄H₈O₃H)₅]₂Bi₈I₃₀ are reported. The title compound is prepared by heating of BiI₃ and diethylene glycol at 413 K in a sealed quartz glass tube filled with argon. Deep red single crystals are grown and applied to perform X-ray powder diffraction and X-ray single-crystal diffraction measurements. The compound crystallizes triclinic with space group P-1: Z=2, a=13.217(1) Å, b=15.277(1) Å, c=22.498(1) Å, α=84.33(1), β=73.18(1), γ=67.48(1). [Bi₃I(C₄H₈O₃H₂)₂(C₄H₈O₃H)₅]₂Bi₈I₃₀ comprises the novel polynuclear [Bi₈I₃₀]⁶⁻ anion and [Bi₃I(C₄H₈O₃H₂)₂(C₄H₈O₃H)₅]³⁺ as the cation. Cation as well as the anion can be assumed to represent intermediates between solid BiI₃ and BiI₃ completely dissolved in diethylene glycol.     

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.     

Supramolecular Systems Based on Ca2+, [Mo3O2S2Cl6(H2O)3]2s-, [Mo3S4Cl6.75Br0.25(H2O)2]3s- and Cucurbit[6]uril

Adducts of cucurbit[6]uril with Ca²⁺ and trinuclear cluster chloroaquacomplexes (H₉O₄)₂(H₇O₃)₂[(Ca(H₂O)₅)2(C₃₆H₃₆N₂₄O₁₂)]Cl₈·0.67H₂O (1) and [(Ca(H₂O)₅)₂(C₃₆H₃₆N₂₄O₁₂)]× [Mo₃O₂S₂Cl₆(H₂O)₃]₂·13H₂O (2) are obtained and structurally characterized. The structures of both compounds contain polymeric [Ca(H₂O) _n ]₂² CB[6]∞ cations that form infinite columns; the space between them is filled with Cl^s- (1) and [Mo₃O₂S₂Cl₆(H₂O)₃]^2s- (2). A new (H₇O₃)₂(H₅O₂)× [Mo₃S₄Cl_6.25Br_0.25(H₂O)₂](C₃₆H₃₆N₂₄O₁₂)·CH₂Cl₂·6H₂O complex (3) is also obtained and structurally characterized.     

Surface of Ru/Fe2O3 catalysts used in water-gas shift reaction studied by auger electron spectrometry

Summary Carbon deposits on the surface ofRu/Fe₂O₃ catalysts used in the water-gas shift reaction have been investigated by Auger Electron Spectrometry. A correlation has been found between the thickness of the carbon deposit and the catalytic activity in WGSR. The carbon deposit covers the metallic active centers and blocks their contact with reagents. The dotting of the iron oxide support with sodium has been found to reduce the amount of carbon deposit. .      

Effect of conversion of NO2 into no on the catalytic reduction of NO2 with C3H6 in excess O2

During the reduction of NO₂ by C₃H₆ in O₂ over alumina-supported Au, Rh and Pt it was found that three parallel reactions take place,i.e., reduction of NO₂ to N₂ and N₂O, partial decomposition of NO₂ to NO and oxidation of C₃H₆ to CO and CO₂. In the absence of C₃H₆, the NO₂→NO+O₂ reaction reaches a fast equilibrium on Rh and Pt but not on Au and γ-Al₂O₃. Addition of C₃H₆ to the NO₂+O₂ mixture leads to the formation of NO above equilibrium conversion levels.     

Ru/g-al2o3 as reusable catalyst for dehydrogenation of alcohols without hydrogen acceptor

Summary Ru/g-Al₂O₃ catalyzed the dehydrogenation of alcohols to carbonyl compounds without employing hydrogen acceptor. The catalyst was readily recovered from the reaction mixture and could be reused.     

Preparation and catalytic oxidation performance andOF Pr2-xSrxCoO4+λwithK2NiF4structure

Summary A series of Pr_2-xSr_xCoO_4+λmixed oxides were prepared and used successfully for oxidation of CO and C₃H₈. The results show that Pr_2-xSr_xCoO_4+λdisplay K₂NiF₄-type structure and their catalytic activities are closely correlated with the concentration of Co³⁺, mobile lattice oxygen and oxygen vacancy.</o:p>     

Eu(C10H9N2O4)(C10H8N2O4)(H2O)3]•0.5bipy•3H2O配合物的合成、晶体结构及荧光性质

在水-乙醇混合体系中, 以2-羰基丙酸水杨酰腙(C₁₀H₁₀N₂O₄)、2,2-联吡啶(C₁₀H₈N₂, 简写bipy)与Eu(NO₃)₃•4H₂O反应, 首次培养出黄色单晶[Eu(C₁₀H₉N₂O₄)(C₁₀H₈N₂O₄)(H₂O)₃]•0.5bipy•3H₂O. 该晶体属三斜晶系, 空间群为P-1, 晶胞参数a＝0.93392(16) nm, b＝1.3100(2) nm, c＝1.3895(2) nm, α＝97.205(3)°, β＝105.411(2)°, γ＝106.364(2)°, V＝15.35(2) nm³, Z＝2, μ＝2.118 mm^－1, D_c＝1.686 Mg/m³, F(000)＝786, R＝0.0116, wR＝0.0507, GOF＝0.995. 晶体测试结果表明, 该单晶结构为铕的9配位配合物, 两个2-羰基丙酸水杨酰腙分别以负一价和负二价酮式和三个水分子同时参与配位; 每个2-羰基丙酸水杨酰腙中的羧基氧、酰胺基中的羰基氧和C＝N中的氮与Eu^3＋配位, 形成两个共边的稳定五元环, 另三个配位原子则分别来自三个水分子中的氧原子, 该配合物在空间呈扭曲的单帽四方反棱柱, 而在不对称单位中还有游离的一个2,2-联吡啶分子和三个水分子, 这些游离分子与配位分子之间存在大量分子内和分子间氢键, 整个分子在空间呈三维网状结构. 发光性能测试表明该配合物具有很好的荧光性质.     

Vapor phase hydrofluorination of acetylene to vinyl fluoride over La2O3-Al2O3 catalysts

A series of La-doped Al₂O₃ catalysts were prepared and tested for the vapor phase hydrofluorination of C₂H₂ to vinyl fluoride (CH₂CHF, VF). It was found that the La-doped catalyst gave a stable catalytic performance and a higher selectivity to the desired VF and a lower selectivity to coke deposition compared with the pure Al₂O₃ catalyst. The enhancement in VF selectivity on the La-doped catalyst was due to the elimination of acidic sites on the Al₂O₃ surface by the addition of La₂O₃, evidenced by NH₃-TPD results, which could also explain the declined selectivity to coke deposition on the catalyst. Raman result indicated there were two different vibration forms of CH distortion and CC expansion for the coke deposition.