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1.
A series of carboxylated long chain polyethylene glycols(abbreviated as PEGCOOH) has been synthesized and used to support chloroplatinic acid.These supported catalysts were then tested for their efficiency in the hydrosilylation of alkenes.The factors affecting their catalytic properties,e.g.relative molecular mass of polyethylene glycol,reaction temperature,platinum content,and type of alkenes,have been studied.It was found that the activity of the platinum catalyst decreased with increasing length of the polyethylene glycol chain,and increased with reaction temperature.Moreover,these catalysts could be reused several times without a noticeable decrease in activity or selectivity.The reaction pathway leading to excellent selectivity for the β-adduct of hydrosilylation of alkenes with triethoxysilane catalyzed by this catalysis system was discussed. 相似文献
2.
生物油中乙酸和乙醇共裂化获取汽油产物的研究简 总被引:1,自引:0,他引:1
Abstract Acetic acid was selected as the model compound representing the carboxylic acids present in bio-oil. This work focuses the co-cracking of acetic acid with ethanol for bio-gasoline production. The influences of reaction temperature and pressure on the conversion of reactants as well as the selectivity and Conaposition of the crudegasoline phase were investigated. It was found that increasing reaction temperature benefited the conversion of reactants and pressurized cracking produced a higher crude gasoline yield. At 400 ℃ and 1 MPa, the conversion of the reactants reached over 99% and the selectivity of the gasoline phase reached 42.79% (by mass). The gasoline phase shows outstanding quality, with a hydrocarbon content of 100%. 相似文献
3.
Caffeic acid phenethyl ester(CAPE) is a rare, naturally occurring phenolic food additive. This work systematically reported fundamental data on conversion of caffeic acid(CA), yield of CAPE, and reactive selectivity during the lipase-catalyzed esterification process of CA and phenylethanol(PE) in ionic liquids(ILs). Sixteen ILs were selected as the reaction media, and the relative lipase-catalyzed synthesis properties of CAPE were measured in an effort to enhance the yield of CAPE with high selectivity. The results indicated that ILs containing weakly coordinating anions and cations with adequate alkyl chain length improved the synthesis of CAPE. [Emim][Tf2 N] was selected as the optimal reaction media. The optimal parameters were as follows by response surface methodology(RSM): reaction temperature, 84.0 °C; mass ratio of Novozym 435 to CA, 14︰1; and molar ratio of PE to CA, 16 ︰ 1. The highest reactive selectivity of CAPE catalyzed by Novozym 435 in [Emim][Tf2 N] reached 64.55%(CA conversion 98.76% and CAPE yield 63.75%, respectively). Thus, lipase-catalyzed esterification in ILs is a promising method suitable for CAPE production. 相似文献
4.
Cu(II) and Mn(II) metals embedded on mesoporous SBA-15 were synthesized by co-precipitation technique.The support and catalysts were characterized by SEM–EDX,TEM,BET,XRD and ICP-AES methods.The catalytic activity of these catalysts was evaluated for styrene oxidation at various reaction conditions such as styrene to TBHP mole ratio,temperature,catalyst amount by using TBHP as an oxidizing agent.Major reaction products were styrene oxide and benzaldehyde and highest styrene conversion(97.3%) was observed at styrene to TBHP mole ratio of 1:4,temperature at 80 °C and 20 mg of catalyst.Further,the recyclability of the catalysts was observed and found that they can be recycled three times without major loss in their activity and selectivity. 相似文献
5.
To explore the feasibility of extracting aromatic acid products from oxidizing coal, two aromatic acids, trimellitic and [1,1′-biphenyl]-2,2′-dicarboxylic acid, were selected as the solutes, and the extraction equilibrium of the acids were studied with 1-octanol, 50% tributyl phosphate (TBP) in kerosene, and 10% trialkylphosphine oxide (TRPO) in kerosene. The results showed that the degree of extraction of [1,1′-biphenyl]-2,2′-dicarboxylic acid was larger than that of trimellitic acid for all of the solvent, and the extraction capacity with TRPO is more effective than the one with TBP. The extraction behavior of aromatic polyacid is different from that of carboxylic acid, and the reactive extraction function of aromatic acids with TBP and TRPO is not as effective as that of carboxylic acid. 1-octanol could be used to remove [1,1′-biphenyl]-2,2′-dicarboxylic acid from the mixture of trimellitic acid and [1,1′-biphenyl]-2,2′-dicarboxylic acid. Because the weak hydrogen bond association exists between -OH in 1-octanol and -COOH in aromatic acid, the extractive selectivity of [ 1, 1′-biphenyl]-2,2′-dicarboxylic to trimellitic acid depends on the stoichiometric ratio. 相似文献
6.
Yaling Luo Changjun Liu Hairong Yue Siyang Tang Yingming Zhu Bin Liang 《中国化学工程学报》2019,27(8):1851-1856
The selective oxidation of cyclopentene by aqueous H_2O_2 using H_3PW_(12)O_(40) and tetrabutyl ammonium bromide(TBAB) as a phase transfer catalyst has been investigated. The results show that the presence of TBAB significantly improved the oxidation selectivity of cyclopentene. The effects of the reaction conditions on the conversion of cyclopentene were investigated in detail. The optimal reaction conditions are as follows: the H_3PW_(12)O_(40) to TBAB molar ratio, 1:1–1:3; H_3PW_(12)O_(40) to cyclopentene molar ratio,0.54:100–0.64:100; and molar ratio of H_2O_2 to cyclopentene, 1.6:1. The conversion reached to 59.8% in 4h at 35.0 °C, while the selectivity of glutaraldehyde was 38.0% and the selectivity of 1,2-cyclopentanediol was 55.6%. In addition, a route for oxidation of cyclopentene by aqueous H_2O_2 using a heteropoly acid and quaternary ammonium salt as a phase transfer catalyst was proposed. 相似文献
7.
Isooctane is a promising gasoline additive that could be produced by dimerization of isobutene (IB) with subse-quent hydrogenation. In this work, the dimerization of IB has been carried out in a batch reactor over a temper-ature range of 338–383 K in the presence of laboratory prepared Ni/Al2O3 as a catalyst and n-pentane as solvent. The influence of various parameters such as temperature, catalyst loading and initial concentration of IB was examined. A Langmuir–Hinshelwood kinetic model of IB dimerization was established and the parameters were estimated on the basis of the measured data. The feasibility of oligomerization of IB based on the reactive distil ation was simulated in ASPEN PLUS using the kinetics developed. The simulation results showed that the catalyst of Ni/Al2O3 had higher selectivity to diisobutene (DIB) and slightly lower conversion of IB than ion exchange resin in the absence of polar substances. 相似文献
8.
Wax esters were synthesized in a solvent free system catalyzed by immobilized lipase from Candida sp. 99-125, with oleic acid and cetyl alcohol. The effects of substrate molar ratio, lipase dosage and water removal were investigated in a 50 ml flask incubated in a thermostatic cultivation cabinet. The optimized conditions were: temperature 40 ℃, shaking at 170 r·min-1, acid/alcohol molar ratio 1:0.9, lipase dosage in 10% (by mass) of oleic acid, and open reaction for water removal. As a result, the conversion rate reached 98% for reaction of 8 h. The volume of reactor was scaled up to 1 L three-neck flask. The optimized parameters were: 200 r·min-1 agitation speed, 2.5% (by mass) lipase dosage, others were the same as the parameters described above. The conversion rate reached 95% for reaction of 24 h. The lipase retained 46% conversion rate after reuse for 6, 7 batches. The products were purified by removing remained cetyl alcohol and fatty acids with ethanol and saturated sodium carbonate so-lution, respectively. The purity of the wax ester, cetyl oleate, was 96%. The physical and chemical properties of cetyl oleate were tested and compared with those of jojoba oil. The results show that the product cetyl oleate has great potential to use as the substitute of natural jojoba oil. 相似文献
9.
Shape-selective catalysts for the disproportionation of toluene were prepared by the modification of the cylinder-shaped ZSM-5 zeolite extrudates with chemical liquid deposition with TEOS (tetraethyl orthosilicate).Various parameters for preparing catalysts were changed to investigate the suitable conditions.The resulting cata-lysts were tested in a pressured fixed bed reactor and characterized by SEM (scanning electron microscopy).The conversion of toluene and para-xylene selectivity were influenced remarkably by the n(SiO2)/n(Al2O3) ratio of ZSM-5 zeolite,the type and amount of deposition agent,acid and solvent used,and the time and cycle of deposition treatment.TEOS was proved to be a more efficient agent than the conventional polysiloxanes when the deposition amount was low.The catalyst prepared at the suitable conditions exhibited a high para-xylene selectivity of 91.1% with considerable high conversion of 25.6%.SEM analyses confirmed the formation of a layer of amorphous silica on the external surface of ZSM-5 zeolie crystals,which was responsible for the highly enhanced shape-selectivity. 相似文献
10.
苯与双氧水在高效钼钒磷杂多酸催化剂上的羟基化 总被引:1,自引:0,他引:1
Keggin type molybdovanadophosphoric heteropoly acids, H3+nPMo12-nVnO40(n=1-3), were prepared by a novel environmentally benign method, and their catalytic performances were evaluated via hydroxylation of benzene to phenol with hydrogen peroxide as oxidant in a mixed solvent of glacial acetic acid and acetonitrile. Various reaction parameters, such as reaction time, reaction temperature, ratio of benzene to hydrogen peroxide, concentration of aqueous hydrogen peroxide, ratio of glacial acetic acid to acetonitrile in solvent and catalyst con- centration, were changed to obtain an optimal reaction conditions. H3+nPMo12-nVnO40(n=1-3) are revealed to be highly efficient catalyst for hydroxylation of benzene. In case of H5PMo10V2O40, a conversion of benzene of 34.5% with the selectivity of phenol of 100% can be obtained at the optimal reaction conditions. 相似文献
11.
R. T. Stamenova C. B. Tsvetanov K. G. Vassilev S. K. Tanielyan S. K. Ivanov 《应用聚合物科学杂志》1991,42(3):807-812
Polymer-supported molybdenum and vanadium catalysts were synthesized using gel-type crosslinked copolymers with microheterogeneous structure. The supports were composed of inert ethylene–propylene rubber and crosslinked high molecular weight poly(ethylene oxide) matrices and polymeric ligands grafted or forming interpenetrating networks: poly(acrylic acid), poly(methacrylic acid), poly(4-vinylpyridine), and polyvinyl alcohol. Catalytic activity and selectivity of some of these complexes were tested in epoxidation of styrene by ethylbenzene hydroperoxide. Molybdenyl cations are strongly coordinated with pyridine-containing copolymers giving catalysts of high activity and selectivity. They provide conversion and selectivity above 70%. Because of the microheterogeneous mosaic-like structure of the supports, better accessibility of the active sites is achieved. 相似文献
12.
Hans R. Kricheldorf Matthias Berghahn Nicolas Probst Mihai Gurau Gert Schwarz 《Reactive and Functional Polymers》1996,30(1-3):173-189
Several classes of cholesteric and photoreactive homo- and copolyesters were synthesized and characterized. Most of these polyesters were prepared in such a way that a chiral spacer (e.g. isosorbide) was polycondensed with a photoreactive dicarboxylic acid, such as 4-carboxycinnamic acid, benzene- 1,4-bisacrylic acid, 4-(4′-carboxyphthalimido)cinnamic acid. In several cases other dicarboxylic acids, such as naphthalene-2,6-dicarboxylic acid or 4-aminobenzoic acid trimellitimide were cocondensed to favor the formation of a Grandjean texture. When ‘sugar diols’ such as isosorbide or isomannide were used as chiral building blocks, suitable diphenols were required as comonomers to stabilize the LC phase. Most polyesters were capable of forming a selectively reflecting Grandjean texture, which can be fixed by crosslinking using UV light. An alternative synthetic strategy based on chiral, substituted terephthalic acids is discussed. 相似文献
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15.
New synthesis routes have been investigated for the production of dinitrotoluenes (DNTs) from toluene or an equimolar mixture of 2-nitrotoluene (2-NT) and 4-nitrotoluene (4-NT) and nitric acid using solid acids as heterogeneous catalysts. The main objective was the replacement of liquid sulphuric acid. A secondary goal was the increase of 4-NT and 2,4-DNT in the product mixture, which are more valuable products. Particular consideration was given to the feasibility of future large-scale process implementation. Continuous flow vapour phase reaction, and liquid phase reaction with simultaneous distillation were investigated. DNT formation in the vapour phase reaction was negligible with all solid acids tested. Preshaped silica impregnated with sulphuric acid was the most active catalyst but a continuous loss of sulphuric acid with time-on-stream was observed. Zeolite beta provided a higher 4-NT to 2-NT ratio than ZSM-5, ZSM-12 and mordenite, but deactivated after 5–10 h on-stream. Regeneration of beta was possible by thermal treatment. The para-selectivity of mordenite could be improved by the creation of a mesoporous system. In the reaction with simultaneous distillation, supported liquid acids exhibited true catalytic behaviour for the conversion of NT to DNT, but a loss of the impregnated acid was observed. Zeolite beta was about half as active as supported liquid acids and gave an exceptionally high 2,4-DNT selectivity of up to 94%, compared to 74–79% obtained with all other solid acids. 相似文献
16.
Catalytic use of zeolites in the Prins reaction of arylalkenes 总被引:1,自引:0,他引:1
María A. Aramendía Victoriano Borau César Jiménez José M. Marinas Francisco J. Romero Francisco J. Urbano 《Catalysis Letters》2001,73(2-4):203-206
The Prins reaction of various arylalkenes with paraformaldehyde on different zeolites as solid acid catalysts was studied. The main product of the reaction under the experimental conditions used was found to be the corresponding 1,3-dioxane. Of the catalysts tested, beta (75) zeolite proved the most active and selective in the Prins reaction of styrene, with a selectivity of 41.4% and a conversion of 95%. Other zeolites such as USY and, especially, ZSM-5, provided much lower yields. The reactions of other arylalkenes were found to be strongly influenced by the substituents on the double bond. 相似文献
17.
Abbas Afkhami Davood Nematollahi Tayyebeh Madrakian Lida Khalafi 《Electrochimica acta》2005,50(28):5633-5640
Electrochemical oxidation of some catecholamines such as dopamine (1), l-dopa (2) and methyldopa (3) has been studied in the presence of 4-aminobenzoic acid (4). Some electrochemical techniques such as cyclic voltammetry using diagnostic criteria derived by Nicholson and Shain for various electrode mechanisms and controlled-potential coulometry were used. Variation in cathodic peaks due to the competition between intramolecular and intermolecular Michael addition reaction was studied in various pH values, and the best conditions for reaction with 4-aminobenzoic acid was obtained. The results indicate an ECE mechanism. The observed homogeneous rate constant (kobs) for Michael addition reaction was estimated by comparing the experimental cyclic voltammetric responses with the digital simulated results. Also, the Michael addition reaction rate constants (km) were calculated using microscopic acidic dissociation constant of ammonium groups in 4-aminobenzoic acid. The chemical oxidation reaction of catecholamines with periodate in the presence of 4-aminobenzoic acid was also studied spectrophotometrically. 相似文献
18.
Poly(3-methoxy-4-hydroxy styrene) (MHS) was prepared as a biodegradable polymer; it offers a simplified model of naturally biodegradable polymers related to softwood lignin, having pendant guaiacyl groups. This polymer was decomposed by microorganisms in soil, and four intermediates were identified in the degradation pathway. Judging from the identified intermediates, vanillic acid seems to be the first biodegradation product of polyMHS in the pathway. The ring cleavage of vanillic acid gives rise to monomethyl ester of β-carboxymuconic acid, discovered as an intermediate in the degradation pathway. Monomethyl ester of β-carboxymuconic acid, which was isolated and characterized, is decomposed to maleic and oxalic acids by microorganisms which are essential for utilization of guaiacyl group. Elucidation of the degradation pathway of polyMHS revealed that the step reactions responsible for the conversion of this compound to maleic and oxalic acids are somewhat similar to the step reactions responsible for the degradation of lignin by microorganisms. 相似文献
19.
Epoxidation of styrene with t-butyl hydroperoxide (TBHP) as an oxidizing agent has been conducted under liquid phase reaction conditions over Zr–Mn-MCM-41 with different nSi/(nZr + nMn) ratios and Mn-MCM-41(31) catalysts for selective synthesis of styrene oxide. The influences of various reaction parameters such as temperature, time, oxidants, and solvents, styrene to TBHP mmol ratios and acetonitrile (MeCN) to N,N-dimethylformamide (DMF) volume ratios on the conversion of styrene and the selectivity of styrene oxide have also been studied. With the decrease of the nSi/(nZr + nMn) ratios of Zr–Mn-MCM-41 catalysts from 327 to 49, the conversion of styrene as well as the yield and selectivity of styrene oxide increase due to the increase of the number of Lewis acid sites on the surface of catalysts. Moreover, the conversion and selectivity in Zr–Mn-MCM-41(49) is higher as compared to that of Mn-MCM-41(31). The Zr–Mn-MCM-41(49) is found to be reusable for the epoxidation of styrene with TBHP for selective synthesis of styrene oxide. 相似文献