H_6P_2W_（18）O_（62）á18H_2O： A green and reusable catalyst for one-pot synthesis of pyrano[4,3-b]pyrans in water

A convenient,effcient and environmentally benign procedure has been developed for the synthesis of pyrano[4,3-b]pyran derivatives via a one-pot,three-component reaction of 4-hydroxy-6-methylpyran-2-one,aldehydes and malononitrile in water using H6P2W18O62á18H2O as catalyst.Reusability of the catalyst and reaction media,short reaction times and easy isolation of products are some added advantages of the present methodology.     

A new route to the synthesis of thieno[2,3-d]pyrimidin-4（3H）-one derivatives catalyzed by 12-tungstophosphoric acid （H3PW12040）

Heteropoly acid H3PW12040 （PW） has been used as an effective catalyst for the synthesis of thieno[2,3-d]pyrimidin-4（3H）-one derivatives. The present methodology offers several advantages, such as high yields, short reaction times, mild reaction condition and a recyclable catalyst with a very easy work up.     

Reaction Chemistry of W—Mn／SiO2 Catalyst for the Oxidative Coupling of Methane

Reaction chemistry of the OCM reaction on W-Mn/SiO2 catalyst has been reviewed in this account.Initial activity and selectivity,stability in a long-term reaction,reaction at elevated pressures and a modelling test in a stainless-steel fluidized-bed reactor show that W-Mn/SiO2 has promising performance for the development of an OCM process that directly produces ethylene from natural gas.A study on surface catalytic reaction kinetics and used cataly st structure characterization revealed a possible reason why C2 and COx selectivity changed during the long-term reaction.Further improvement of the catalyst composition and preparation metbod should be a future direction of study on OCM reaction over W-Mn/SiO2 catalyst.     

Partial oxidation of simulated hot coke oven gas to syngas over Ru-Ni/Mg（Al）O catalyst in a ceramic membrane reactor

Hydrogen amplification from simulated hot coke oven gas (HCOG) was investigated in a BaCo0.7Fe0.2Nb0.1O3−δ (BCFNO) membrane reactor combined with a Ru-Ni/Mg(Al)O catalyst by the partial oxidation of hydrocarbon compounds under atmospheric pressure. Under optimized reaction conditions, the dense oxygen permeable membrane had an oxygen permeation flux around 13.3 ml/(cm2·min). By reforming of the toluene and methane, the amount of H2 in the reaction effluent gas was about 2 times more than that of original H2 in simulated HCOG. The Ru-Ni/Mg(Al)O catalyst used in the membrane reactor possessed good catalytic activity and resistance to coking. After the activity test, a small amount of whisker carbon was observed on the used catalyst, and most of them could be removed in the hydrogen-rich atmosphere, implying that the carbon deposition formed on the catalyst might be a reversible process.     

固载Ru基催化剂上二氧化碳加氢合成甲酸Ⅱ反应条件对催化剂性能的影响

The synthesis of formic acid from carbon dioxide and hydrogen using a silica immobilized ruthenium catalyst as precursor has been studied in different reaction conditions. The results revealed that the TOF （turn over frequency） of HCOOH achieved 1481.5 h^-1 on immobilized ruthenium catalyst near the critical pressure point of CO2 with H2 pressure of 4.0 MPa, reaction temperature of 80℃ and PPh3/Ru molar ratio of 6：1. The reaction activity of immobilized catalyst was higher than that of homogeneous catalyst, and the immobilized catalyst also offered the practical advantages such as easy separation and reuse.     

CATALYTIC ESTERIFICATION OF CARBOXYLIC ACIDS WITH ALCOHOLS BY SULFO-POLYVINYL CHLORIDE

Polyuinyl Chloride reacted with chlorosulfonic acid to form a polymer catalyst PVC-SO3H. This polymer catalyst was found to have high activity for esterification reaction between carboxylic acids and alcohols. This paper deals with the conditions in synthesis of n-butylacetate catalyzed with PVC-SO3H. The PVC-SO3H was used as a catalyst for preparing 11 esters of acetic acid, propiofnic acid and butyric acid with the yields of 82-92%.     

Study of CO2 Hydrogenation to Methanol over Cu-V/γ-Al2O3 Catalyst

The effect of vanadium addition to CU/γ-Al2O3 catalyst used in the hydrogenation of CO2 to produce methanol was studied. It was found that the catalytic performance of the Cu-based catalyst improved after V addition. The influence of reaction temperature, space velocity and the molar ratio of H2 to CO2 on the performance of 12%Cu-6%V/γ-Al2O3 catalyst were also studied. The results indicated that the best conditions for reaction were as follows: 240℃, 3600 h-1 and a molar ratio of H2 to CO2 of 3:1. The results of XRD and TPR characterization demonstrated that the addition of V enhanced the dispersion of the supported CuO species, which resulted in the enhanced catalytic performance of CU-V/γ-Al2O3 binary catalyst.     

Study of a Ru-La/Zr02 Catalyst Prepared by Precipitation Method for Selective Hydrogenation of Benzene to Cyclohexene

A Ru-La/ZrO2 catalyst was prepared by the precipitation method, in which Ru was an active component, La was a promoter and ZrO2 was a dispersant. Comparing with the catalyst prepared by the chemical reduction method, the Ru-La/ZrO2 exhibited higher activity and better selectivity. At 140 ℃ and hydrogen pressure of 5 MPa, the C6H10 selectivity reached 70% at a C6H6 conversion of 35% for a reaction time was 5 min and the total La/Ru loading was 10%. Textural parameters of the catalyst were obtained by physical adsorption, BET surface area and specific pore volume measurements. The catalyst sample gave a BET area of 41 m2/g and a specific pore volume of 1.1 cm^3/g, and the most probable pore distribution was located at 5 to 10 nm. H2-TPR measurements showed that ruthenium oxide could be reduced to its metallic state at about 403 K. XRD determinations indicated that ruthenium and lanthanum were highly dispersed on the zirconia. A significant advantage of the Ru-La/ZrO2 catalyst is that it can be used directly in its unreduced state for the selective hydrogenation of benzene.     

STUDIES ON FISCHER TROPSCH SYNTHESIS OVER Fe-Cu-K CATALYST Ⅰ.CATALYTIC PERFORMANCE

The influence of reaction pressure, temperature, space velocity (GHSV), particle size of catalyst and H2/CO ratio of feed-gas on the steady-state product distribution, conversion of CO, H2 and syngas, olefin to paraffin ratio and CO2/ H2O ratio for FTS reaction were investigated using a coprecipitated copper- potassium promoted iron catalyst. The test was carried out in a fixed-bed reactor. Increasing the reaction temperature from 493. 2 to 5-13. 2 K shifted the hydrocarbon distribution toward the heavier hydrocarbons (C5-C23) and selectively increased CO conversion to CO2. The hydrocarbon distribution was found to be dependent on the H2/CO feed-gas ratio in the range from 1.23 to 2. 22. The CO2/H2O ratio in product decreased as the flow of feed-gas rate increased, which suggests that H2O is a primary product and its reaction with CO to form CO2 occurs via a secondary process. The CO conversion increased with the decrease of catalyst particle size from 10 to 60 mesh (2. 0- 0. 3 mm), while the CO convers     

肼分解催化剂表征及失活机理研究

Ir/ γ Al 2O 3 catalyst for hydrazine decomposition has been investigated by using XPS, SEM, H 2 TPD and H 2 isothermal adsorption. The results show that the iridium species enrich on the surface of the catalyst in more than one state, and that the metallic iridium is the active sites for the reaction. The iridium species were sintered seriously during the reaction, and the amount of H 2 adsorption on used sample was only a quarter of that on fresh sample. The concentration of Cl - species on the surface decreased quickly at the initial period of the reaction process and stayed at a certain low value. Obvious breakup of the surface structure of the used sample was found. In all, the sintering of metallic iridium and the damage of alumina surface structure are the reasons for deactivation of the catalyst, while the Cl - concentration has little effect on the reaction performance.     

Tin(II) Chloride Dihydrate Catalyzed Groebke Condensation: An Efficient Protocol for the Synthesis of 3-Aminoimidazo[1,2-a]pyridines

The ability of tin(II) chloride dihydrate as a catalyst to promote the three-component condensation reaction from a diversity of aromatic aldehydes, 2-aminopyridines and isonitriles at room temperature is described. This methodology affords a number of 3-aminoimidazo[1,2-a]pyridines in the presence of tin(II) chloride dihydrate as a new and mild Lewis acid catalyst in the multi-component reaction in reasonable yields and short reaction time without any significant optimization of the reaction conditions.     

Synthesis of Diethyl Oxalate by a Coupling-Regeneration Reaction of Carbon Monoxide

This article describes a process for the synthesis of diethyl oxalate by a coupling reaction of carbon monoxide, catalyzed by palladium in the presence of ethyl nitrite. The kinetics and mechanism of the coupling and regeneration reaction are also discussed. This paper presents the results of a scale-up test of the catalyst and the process based on an a priori computer simulation.     

Synthesis of silica/metatitanic acid nanocomposite and evaluation of its catalytic performance for aquathermolysis reaction of extra-heavy crude oil

A lipophilic silica/metatitantic acid(denoted as Si O2/H2 TiO 3) nanocomposite was synthesized by hydrothermal reaction with surface-modified Si O2 as the lipophilic carrier. As-synthesized Si O2/H2 TiO 3nanocomposite was used as a catalyst to promote the aquathermolysis reaction of extra-heavy crude oil thereby facilitating the recovering from the deep reservoirs at lowered temperature. The catalytic performance of the as-synthesized Si O2/H2 TiO 3catalyst for the aquathermolysis reaction of the heavy oil at a moderate temperature of 150 °C was evaluated in relation to the structural characterizations by TEM,FTIR,XRD and FESEM as well as the determination of the specific surface area by N2adsorption–desorption method. Findings indicate that as-synthesized Si O2/H2 TiO 3nanocomposite exhibits an average size of about 20 nm as well as good lipophilicity and dispersibility in various organic solvents; and it shows good catalytic performance for the aquathermolysis reaction of the extra-heavy oil extracted from Shengli Oilfield of China. Namely,the assynthesized Si O2/H2 TiO 3catalyst is capable of significantly reducing the viscosity of the tested heavy oil from58,000 c P to 16,000 c P(referring to a viscosity reduction rate of 72.41%) at a mass fraction of 0.5%,a reaction temperature of 150 °C and a reaction time of 36 h,showing potential application in downhole upgrading heavy crude oils.     

Effect of Dimethyl Ether Co-feed on Catalytic Performance of Methane Dehydroaromatization over Mo／HZSM-5 Catalyst

The effect of dimethyl ether (DME) co-feed on the catalytic performance of methane dehydroaxomatization (MDA) over 6Mo/HZSM-5 catalyst was investigated as a function of DME concentration under reaction conditions of T=1023 K, p=101 kPa and SV=1500 ml/(g.h). A high benzene yield wasobtained and the stability of the catalyst was improved by adding 1.5%DME to the CH4 feed. The C6H6 yield was as high as ca. 10% even after reaction for 6 h. The stability of the catalyst was further improved when DME concentration in the co-feed gas was increased to an appropriate value. TGA and TPO results of the used 6Mo/HZSM-5 catalyst showed that the amount of coke on the used catalyst was reduced and the chemical nature of the coke was changed. When 1.5%DME was added to the CH4 feed, the coke formed on the catalyst could be burned off more easily than that when only CH4 was used as reactant. It is supposed that the oxygen in DME may play a role in preventing the coke burnt off at lower temperature from transforming into the coke burnt off at higher temperature, which results in the improvement of the stability of the catalyst.     

A Novel Non-phosgene Process for the Synthesis of Methyl N-Phenyl Carbamate from Methanol and Phenylurea： Effect of Solvent and Catalyst

A novel environmentally benign process for the synthesis of methyl N-phenyl carbamate (MPC) from methanol and phenylurea was studied. Effect of solvent and catalyst on the reaction behavior was investigated. The IR spectra of methanol and phenylurea dissolved in different solvents were also recorded. Compared with use of methanol as both a reactant and a solvent, phenylurea conversion and selectivity to MPC increased by using toluene, benzene or anisole as a solvent, while phenylurea conversion decreased slightly by using n-octane as a solvent. The phenylurea conversion declined nearly 50% when dimethyl sulfoxide (DMSO) was used as a reaction media, and MPC selectivity decreased as well. The catalytic reaction tests showed that a basic catalyst enhanced the selectivity to MPC while an acidic catalyst promoted the formation of methyl carbamate and aniline. Moderate degree of basicity showed the best catalytic performance in the cases studied.     

Mathematical Simulation and Design of Three-Phase Bubble Column Reactor for Direct Synthesis of Dimethyl Ether from Syngas

A three-phase reactor mathematical model was set up to simulate and design a three-phase bubble column reactor for direct synthesis of dimethyl ether (DME) from syngas, considering both the influence of part inert carrier backmixing on transfer and the influence of catalyst grain sedimentation on reaction. On the basis of this model, the influences of the size and reaction conditions of a 100000 t/a DME reactor on capacity were investigated. The optimized size of the 10000 t/a DME synthesis reactor was proposed as follows: diameter 3.2 m, height 20 m, built-in 400 tube heat exchanger (φ38×2 mm), and inert heat carrier paraffin oil 68 t and catalyst 34.46 t. Reaction temperature and pressure were important factors influencing the reaction conversion for different size reactors. Under the condition of uniform catalyst concentration distribution, higher pressure and temperature were proposed to achieve a higher production capacity of DME. The best ratio of fresh syngas for DME synthesis was 2.04.     

Synthesis of Diethyl Oxalate by a Coupling—Regeneration Reaction of Carbon Monoxide

This article describes a process for the synthesis of diethyl oxalate by a copling reaction of carbon monoxide,catalyzed by palladium in the presence of ethyl nitrite ,The kinetics and mechanism of the coupling and regeneration reaction are also discussed ,This paper presents the results of a scale-up test of the catalyst and the process based on an a priori computer simulation.     

Study on the alkylation reaction of guanine and N-acetylguanine and the synthesis of 1''''-C alkylated carba-DHPG analogues

The alkylation reaction of guanine and N-acetylguanine with model compounds such as isopropyl bromide or 4-heptyl tosylate were studied. The reaction conditions such as temperature, solvent, base, and catalyst were examined for their effects on the reaction rate, and the yield and regioselectivity of the coupling reaction. The highest yield was obtained by using DMSO as the solvent. The reaction proceeded in a homogenous manner to give higher yield of 9-N and 7-N substituted product in a mole ratio of 1:1. The ratio could be raised to 2:1 if dibenzo-18-crown-6 was used as a catalyst. Using the above procedure, three carba-DHPG analogues bearing different 1'-C alkyl side chains were synthesized.     

Adaptation of Cu/ZnO/Al_2O_3 to Temperature Change in Methanol Synthesis from CO_2 Hydrogenation

The induction behavior in CO2 hydrogenation was studied by varying the reaction temperature to investigate the adaptation of the Cu/ZnO/Al2O3 catalyst to the temperature change. The results indicated that a used catalyst had a tendency to keep the last running state in new reaction conditions for MeOH formation, and that this tendency was related to the difference in Cu/Cun+ ratio caused by CO2 and CO produced at different reaction temperatures. However, the reverse water-gas shift reaction (RWGS) induced at four temperatures was completely different from that of methanol synthesis. It implied that the two so-called competitive reactions in CO2+H2, RWGS and methanol synthesis, have different active centers.     

Highly efficient synthesis of 2,3-dihydroquinazolin-4(1H)-ones catalyzed by heteropoly acids in water

<正>Heteropoly acids efficiently catalyzed the cyclocondensation reaction of anthranilamide with aldehydes in water at ambient temperature and afforded the corresponding 2,3-dihydro-4(1H)-quinazolinones compounds in good to excellent yields.This method provides mild reaction conditions and clean reaction profiles,using a small quantity of catalyst and a simple workup procedure.