Theoretical Study of Peroxo- and Diperoxomolybdate Formation as Catalysts in the Oxidative Desulfurization of Diesel

The desulfurization is a very important process in the fuel production with less sulfur content, for this reason, several catalysts in different supports and conditions have been tested, however in the most of cases the reaction mechanism is not studied because it is very complicated. In the present work, the molybdate catalyst formation is studied by Density Functional Theory to demonstrate that this catalyst could be used in the oxidative desulfurization. As it is well-know, the solvent influence is very important in the reaction mechanism studies. There are several methodologies where the solvent effect could be considered. In this study the solvent was simulated by three ways: the first one by explicit n-water molecules (with n = 0, 1 and 2), the second one by PCM theory and the last by a combination of the two first. The results show that the structure called I01 is the most probable catalyst in the oxidative desulfurization reaction; additionally the effect of the water molecule surrounding this structure is fundamental to stabilize it. Finally this reactive structure could be formed in water and acetonitrile phases.     

A facile synthesis of 1,2-azidoalcohols by (TBA) 4PFeW11O39·3H2O-catalyzed azidolysis of epoxides with NaN3

The catalytic efficiency of transition metal substituted polyoxometalates in the azidolysis of 1,2-epoxides has been studied in acetonitrile/water, using NaN₃ as the source of the azido group. The reaction is regioselective and afforded the corresponding products in high to excellent yields under mild reaction conditions. Fe (III) substituted polyoxometalate was identified as the optimal catalyst.     

Manganese(II)-Induced Oxidation of Limonene by Dioxygen

Manganese(II) complexes {[Mn^II(bpy)₂ ²⁺]_MeCN} in acetonitrile activate dioxygen for the oxidation of limonene to produce mainly carvone, carveol, limonene oxide, and perillaldehyde. The reaction efficiencies after 24 h reaction time are approximately 5-times higher than those obtained for analogous iron(II) complexes. However, the 5 h long induction period is observed for the common conditions of the reaction. The simultaneous presence of the catalyst, dioxygen and the substrate is necessary for the active species to be formed. When t-BuOOH is present in the reaction mixture, the induction period does not appear. In contrast, the replacement of t-BuOOH by HOOH completely inhibits the reaction. We have proposed a putative mechanism in which a manganese(IV)–hydroperoxo adduct with incorporated substrate is formed during the induction period and it becomes an active catalyst for limonene oxidation.     

中低相对分子质量聚氧化乙烯合成用氨钙催化剂的研究

摘 要：对环氧乙烷开环聚合制备聚氧化乙烯反应的氨钙催化剂,采用正交设计的实验方法,考察了氨：钙质量比、乙腈:钙质量比、环氧丙烷:钙质量比、氨钙反应时间、改性剂反应时间等制备因素对聚氧化乙烯分子量和聚合收率的影响,得到乙腈和环氧乙烷添加量是主要影响因素,并优化得到可用于工业化应用的催化剂制备条件。工业化试验结果表明,聚氧化乙烯产品聚合收率高于98%,产品粘均相对分子量在20至80万间可调。     

中低相对分子质量聚氧化乙烯合成用氨钙催化剂的研究

摘 要：对环氧乙烷开环聚合制备聚氧化乙烯反应的氨钙催化剂,采用正交设计的实验方法,考察了氨：钙质量比、乙腈:钙质量比、环氧丙烷:钙质量比、氨钙反应时间、改性剂反应时间等制备因素对聚氧化乙烯分子量和聚合收率的影响,得到乙腈和环氧乙烷添加量是主要影响因素,并优化得到可用于工业化应用的催化剂制备条件。工业化试验结果表明,聚氧化乙烯产品聚合收率高于98%,产品粘均相对分子量在20至80万间可调。     

中低相对分子质量聚氧化乙烯合成用氨钙催化剂的研究

对环氧乙烷开环聚合制备聚氧化乙烯反应的氨钙催化剂进行研究。采用正交实验法,考察了m(氨)∶m(钙)、m(乙腈)∶m(钙)、m(环氧丙烷)∶m(钙)、氨钙反应时间、改性剂反应时间等制备因素对聚氧化乙烯相对分子质量(简称分子量,下同)和聚合收率的影响,得到乙腈和环氧乙烷添加量是主要影响因素,并优化得到可用于工业化应用的催化剂制备条件。工业化实验结果表明,聚氧化乙烯产品聚合收率高于98%,产品黏均分子量在2×105~8×105可调。     

The hydrogenation of cinnamaldehyde by supported aqueous phase (SAP) catalyst of RhCl(TPPTS)3: Selectivity, kinetic and mass transfer aspects

The hydrogenation of trans-cinnamaldehyde catalysed by a supported aqueous phase catalyst of RhCl(TPPTS)₃ [TPPTS: trisodium salt of tris(m-sulfophenyl)phosphine] on silica was investigated in terms of the product selectivity, reaction kinetics and mass transfer characteristics. The hydrogenation is selective at the CC bonds in cinnamaldehyde giving hydrocinnamaldehyde as the main product. To achieve high selectivity (99.9%), it is necessary to employ a low initial concentration of cinnamaldehyde (0.076 M). The selectivity also depended on the reaction operating conditions (pressure, temperature, catalyst loading) and the water content property of the SAP catalyst. Optimum water content of the SAP catalyst giving maximum activity was obtained when the pore volume of the supports was completely filled with water. The overall order of reaction was first-order and therefore the conventional three-phase slurry model was applied to the SAP system for the mass transfer analysis. The gas-liquid mass transfer and the reaction resistances were the controlling steps of comparable significance, while liquid-solid mass transfer resistance was negligible in this system. Under similar conditions, the SAP catalyst gave a lower reaction rate than the analogous biphasic catalyst.     

Catalytic oxidation of isophorone to ketoisophorone over ruthenium supported MgAl-hydrotalcite

Selective oxidation of α-isophorone to ketoisophorone was carried out over Ruthenium supported MgAl-hydrotalcite in the temperature range 40–100 °C using acetonitrile as a solvent and tert-butyl hydroperoxide as an oxidant. The influence of various reaction parameters, such as reaction temperature, reaction time, substrate: catalyst mass ratio, substrate:oxidant mole ratio, and nature of solvent was studied. A maximum conversion of 60% KIP with 100% selectivity in 48 h was observed with a substrate: catalyst mass ratio of 10:1 at 60 °C.     

Optimization of the Synthesis of 2,4,6,8,10,12‐Hexaallyl‐ 2,4,6,8,10,12‐Hexaazaisowurtzitane

2,4,6,8,10,12‐Hexaallyl‐2,4,6,8,10,12‐hexaazaisowurtzitane (HALLIW) was obtained in a condensation reaction of glyoxal with allylamine in the presence of a protonic acid as a catalyst. Optimization of the synthesis was accomplished by means of a mathematical experiment planning theory with the steepest descent method. The effect of the following parameters was examined: process temperature, amount of the catalyst, amount of the solvent, glyoxal addition time, reaction time, and the ratio of the substrates. As a result of the study an improved yield was achieved from 20 to 66.5%. The highest yield for the reaction was found for the conditions (mole ratios relative to glyoxal): catalyst (formic acid) 0.1 : 1; solvents: acetonitrile 9.35 : 1, water 0.18 : 1; allylamine 2.2 : 1; temperature 15 °C; glyoxal addition time 15 min, reaction time 60 min. The studies were conducted on a small laboratory scale where the yield and purity of the product obtained were examined. A method was developed for purification of HALLIW. NMR, IR spectroscopy, DSC, and TG analyses were employed in the study and their results are reported.     

A highly efficient synthesis of N-glycosyl-1,2,3-triazoles using a recyclable cellulose-copper(0) catalyst in water

Cellulose supported copper(0) was used as a highly active heterogeneous catalyst to synthesize N-glycosyl-1,2,3-triazoles from glycosyl azides and alkynes. Cellulose-Cu(0) catalysed the cycloaddition reaction to produce the corresponding products in good to excellent yields in water. This heterogeneous catalyst has the advantages of high catalytic reactivity and low copper leaching. The separation and reuse of the catalyst are easy and efficient.     

氰酸钠法合成磺酰脲类除草剂苄嘧磺隆

研究了以邻甲酸甲酯苄基磺酰氯、2-氨基-4,6-二甲氧基嘧啶和氰酸钠为原料,乙腈为溶剂,在吡啶催化下合成除草剂苄嘧磺隆的新方法。考察了溶剂种类、催化剂用量、氰酸钠用量、反应时间、反应温度等因素对反应的影响。结果表明:邻甲氧羰基苄基磺酰氯、2-氨基-4,6-二甲氧基嘧啶、吡啶和氰酸钠摩尔比为1∶1∶1∶1.2,乙腈为溶剂,在40°C下搅拌反应3 h,产品收率67.8%,纯度97.0%(HPLC)。该方法避免了剧毒光气,简化了工艺路线,是一个对环境友好的磺酰脲除草剂的合成方法。     

Selective Catalytic Dehydration of Tetrahydro-2-furanylmethanol Dehydration to 5-Methyl-2,3-dihydrofuran Over Large-pore Zeolites

The first example of selective synthesis 5-methyl-2,3-dihydrofuran (MDHF) via dehydration of tetrahydro-2-furanylmethanol (THFM) is described. This synthesis is accomplished in a single-step reaction and uses readily available catalysts consisting of sodium-exchanged faujasite zeolites (Na-X and Na-USY). The mechanism is hypothesized to involve a hydride shift in reactant THFM, which leads to MDHF. This is fundamentally different from the known ring-expansion pathway for hydrolysis, which synthesizes 3,4-dihydro-2H-pyran (DHP). The activity and selectivity of the catalysts to MDHF was observed to increase with time on stream, and decrease upon increasing reaction temperature. Upon increasing either the initial water content of the catalyst or water partial pressure during reaction, an increase in the MDHF/DHP ratio was observed. This last observation helps correlate the above-mentioned trends in the catalyst activity and selectivity with increased time on stream, since the dehydration reaction synthesizes water.     

Slurry-Phase Fischer–Tropsch Synthesis Using Co/γ-Al2O3, Co/SiO2 and Co/TiO2: Effect of Support on Catalyst Aggregation

The catalytic performance of Co/γ-Al₂O₃, Co/SiO₂ and Co/TiO₂ catalysts has been investigated in a slurry-phase Fischer–Tropsch Synthesis (FTS). Although Co/SiO₂ catalyst shows higher CO conversion than the other catalysts, the intrinsic activity is much higher on Co/TiO₂ due to large pore size and low deactivation of large cobalt particles by reoxidation mechanism. Co/γ-Al₂O₃ catalyst confirms low formation rate of oxygenates and C₅₊ selectivity because of deactivation of catalyst due to catalyst aggregation and reoxidation by the in situ generated water during the FTS reaction. Long-chain hydrocarbons such as wax formed during FTS reaction generally contains water and trace amount of oxygenate which are conducive to the formation of a macro-emulsion of wax products. Formation of such macro-emulsion on the catalyst suggests that the presence of proper amount of alcohol content derived FTS reaction on large pore of catalyst inhibits the catalyst aggregation. The intrinsic activity (turn-over frequency; TOF) of cobalt-based catalysts, in a slurry-phase FTS reaction, is affected by the average pore size of catalyst, cobalt particle size, degree of reduction of cobalt species and possible reoxidation by in situ generated water.     

水处理提高MOF-199催化苯羟基化反应性能

以一水合乙酸铜和均苯三酸为原料,采用常温搅拌法合成金属有机框架化合物MOF-199,用XRD、IR、BET对其表征.将MOF-199用水处理后作为催化剂用于苯羟基化反应,考察了催化剂的用量、反应温度、反应时间、双氧水添加量对催化反应的影响.较优反应条件为:MOF-199(140mg,0.23mmol)、乙腈4mL、苯1.1mL、H₂O₂3.3mL,在60℃的水浴中反应30min,所得苯的氧化物的产率为23.3%,苯酚的选择性为53.1%,转化频率(TOF值)为25.0h^-1.水处理显著提高了MOF-199的催化活性,并形成了一种新的氧化模式,在一定程度上保护了MOF-199的框架结构.     

Cesium-saponites as excellent environmental-friendly catalysts for the synthesis of N-alkyl pyrazoles

An easy and efficient procedure for the synthesis of N-alkyl pyrazoles is reported. The reaction is carried out by alkylation of pyrazole with three different alkyl bromides using acetonitrile or dimethylformamide as solvents and different pillared saponites impregnated with cesium as catalysts. The best experimental condition was the use of DMF at 80 °C, the pillared saponite impregnated with cesium carbonate being the most active catalyst. N-Alkyl pyrazoles, which are key intermediates in the synthesis of pharmacologically active compounds, are obtained in almost quantitative yield at very short reaction times. The loading of cesium slightly affected the conversion values.     

Kinetic studies of liquid phase ethyl tert-butyl ether (ETBE) synthesis using macroporous and gelular ion exchange resin catalysts

Ethyl tert-butyl ether (ETBE) synthesis from ethanol (EtOH) and tert-butyl alcohol (TBA) was studied with different macroporous and gelular ion exchange resin catalysts. Purolite^® (CT-124, CT-145H, CT-151, CT-175 and CT-275) and Amberlyst^® (15 and 35) ion exchange resins were used for the present work. Effect of various parameters such as catalyst type, temperature, reactants feed molar ratio and catalyst loading were studied for the optimisation of reaction condition. Among the catalysts studied, Purolite CT-124 gave the best results for TBA conversion and selectivity towards ETBE. Kinetic modelling was performed with this catalyst and activation energy and water inhibition coefficient were determined. Heterogeneous kinetic models [e.g., Eley-Rideal (ER), Langmuir-Hinshelwood-Hougen-Watson (LHHW)] were unable to predict the behaviour of this etherification reaction, whilst the quasi-homogeneous (QH) model represented the system very well over wide range of reaction conditions.     

Synthesis of isoalkanes over Fe–Zn–Zr/HY composite catalyst through carbon dioxide hydrogenation

The reaction path of isoalkanes formation via CO₂ hydrogenation was studied over the Fe–Zn–Zr/HY composite catalyst, which gives high selectivity to isoalkanes. The results indicate that the reverse water–gas shift reaction is not the indispensable step for the synthesis of hydrocarbons. And i-C₄ (iso-butane) is formed from propylene and methanol through MTG (methanol to gasoline) reaction and i-C₅ (iso-pentane) obtained from the reaction of C₂ and C₃ through the additive dimerization. A part of C₁, C₄ is formed on the sole Fe–Zn–Zr catalyst from methanol for the CO₂ hydrogenation over Fe–Zn–Zr/HY composite catalyst.     

The synthesis of (N1E,N4E)-N1,N4-bis(pyridine-2-YL) ethylene benzene-1,4-diamine and investigation of its efficiency as new binuclear catalyst complex in copper-based ATRP

(N¹E,N⁴E)-N¹,N⁴-bis(pyridin-2-yl) ethylene benzene-1,4-diamine (BPEBD) was synthesized by condensation of 2-acetyl pyridine and 1,4-diaminobenzene and its efficiency as a catalyst in Cu-based atom transfer radical polymerizations (ATRP) of methyl methacrylate (MMA) and styrene (S) was investigated. Linear first-order kinetic plots were obtained. However, there were induction periods. The apparent rate constant values of ATRP of MMA with CuCl/BPEBD catalyst system in toluene were found to be between 2.10 × 10^?5 and 9.83 × 10^?5 s^?1, while they were between 6.67 × 10^?6 and 3.30 × 10^?5 s^?1 in the case of acetonitrile, indicating the presence of a low radical concentration throughout the polymerizations. Low apparent rate constant values denote a good control over ATRP in general. Apparent rate constant vs [ligand]/[catalyst] ratio plots showed a maximum at the [ligand]/[catalyst] ratio of 1. In the ATRP of MMA in toluene, M _n,GPC values increased linearly with conversion and these molecular weight values were close to M _n,th in comparison to that of in acetonitrile. In the polymerization of S, the control of molecular weights was not good, although the reactions were first-order kinetics. Cyclic voltammetry measurements confirmed that CuCl/BPEBD complex in acetonitrile gives quasi-reversible redox couples, and copper (I) centers in CuCl/BPEBD binuclear catalyst complexes are readily oxidized and it potentially suits to facile ATRP.     

New molybdenum(VI) complex with ONS-donor thiosemicarbazone ligand: Preparation,structural characterization,and catalytic applications in olefin epoxidation

New dioxomolybdenum(VI) complex was prepared by reacting 1-(2,4-dihydroxybenzylidene)-N-methyl-N-phenylthiosemicarbazone (H₂L) as ligand and [MoO₂(acac)₂] in acetonitrile solution. The doubly deprotonated ligand is coordinated to molybdenum through sulfur atom, hydrazinic nitrogen atom and phenolic oxygen atom. The resulting complex with the formula [MoO₂L(CH₃CN)] which contains an acetonitrile molecule in sixth site of coordination, was characterized by elemental analyses, ¹H NMR, IR and electronic spectroscopic studies and single crystal X-ray diffraction analysis. This complex was tested as a catalyst for the homogeneous epoxidation of olefins using tert-butyl hydrogen peroxide (TBHP) as an oxidant. The catalyst shows efficient reactivity in the olefins epoxidation reactions giving high yield and selectivity under atmospheric conditions, in most cases.     

2-(4,6-二甲氧基)嘧啶乙腈的合成研究

由4,6-二甲氧基-2-氯嘧啶与氰乙酸叔丁酯反应制备了2-氰基-2-(4,6-二甲氧基嘧啶基)乙酸叔丁酯,而后在对甲苯磺酸催化作用下,由2-氰基-2-(4,6-二甲氧基嘧啶基)乙酸叔丁酯脱羧制备了标题化合物。着重考察了不同反应时间、反应温度及物质的量比对目标产物产率的影响。较佳的合成条件为:n(对甲苯磺酸)∶n[2-氰基-2-(4,6-二甲氧基嘧啶基)乙酸叔丁酯]=0.08∶1,反应时间2 h,反应温度100℃,产物收率可达90%以上。化合物结构经IR1、HNMR1、3CNMR、MS进行了表征。