酸催化制备生物柴油的研究概况及发展

生物柴油生产过程中的催化剂是一个很关键的问题,目前实际生产中碱催化和酸催化应用较为广泛.相比之下酸催化应用受到了限制,然而酸催化制备生物柴油的优点也是显而易见的.本文简述了在酸催化作用下将高酸值原料油转化为生物柴油的原理,酸催化的主要工艺,重点介绍国外研究者从机理方面对酸催化剂的研究,涉及酯交换和酯化两个方面.对酸催化反应的影响因素以及存在解决的问题也稍加叙述.     

超临界二氧化碳中的不对称合成研究进展

主要介绍了超临界二氧化碳中的不对称合成反应,如不对称氢甲酰化反应、碳-碳双键的不对称催化氢化、亚胺不对称催化还原、烷基化反应、不对称D-A反应、醇醛缩合反应、不对称酶催化反应等的研究现状,同时对离子液体与超临界二氧化碳构成的混合介质中的不对称合成研究进展作了介绍,对这一领域中若干基本问题的研究发展趋势进行了分析讨论。     

Chain extending of lactic acid oligomers. 2. Increase of molecular weight with 1,6-hexamethylene diisocyanate and 2,2′-bis(2-oxazoline)

Lactic acid polymers were synthesised from oligomers by the addition of highly reactive 1,6-hexamethylene diisocyanate (HMDI) and 2,2′-bis(2-oxazoline) (BOX) as chain extenders. The effects were studied of adding the extenders simultaneously and sequentially and in different amounts. The reactions were followed and the polymers obtained were structurally characterised by size exclusion chromatography and spectroscopy (NMR and FTIR). High molecular weight poly(lactic acids) were obtained by both simultaneous and sequential addition. The mode of addition and the amounts of extenders had a considerable effect on the branching. The addition of HMDI before BOX in the sequential linking produced more highly branched polymers than did the simultaneous addition. Branching and crosslinking reactions were identified as side reactions of the chain extending reactions. The gel formation was attributed to the reactions of BOX and HMDI with urethane and amide but not with oxamide.     

Kinetic studies on the Reaction of Cyanuric Chloride with Amines

The individual steps in the reactions of cyanuric chloride with n-butyl amine in N-methyl pyrrolidone (NMP) and with morpholine in isopropanol (i-PrOH) were followed kinetically. The ratio of the exchange rates of the first, the second and the third chlorine atom was unexpectedly high in both cases. The reactions of n-butylamino dichlorotriazine with several amines were studied kinetically both in NMP and in i-PrOH. Linear free-energy relationships exist both between our values in NMP and in isopropanol and between our values and reaction rates of p-nitro fluorobenzene with the corresponding amines (in DMSO) determined by Suhr.     

Assessment of lipase- and chemically catalyzed lipid modification strategies for the production of structured lipids

The purpose of the present study was to devise a two-step reaction to produce partial glycerides, which would subsequently be used as substrates in both lipase-catalyzed and chemically catalyzed esterification reactions with caprylic acid. The yields and kinetics of these two-step reactions were compared to established lipase-catalyzed acidolysis and transesterification as well as to chemical transesterification reactions. Acyl migration did not occur during the hydrolysis or short-path distillation steps in the preparation of free fatty acid-free partial glycerides for esterification reactions. No significant differences in final yields (59.9% to 82.8% w/w of total triacylglycerols) of new structured lipids were detected among lipase-catalyzed (24 h) and chemically catalyzed (5 h) reactions; however, the yield of new structured triacylglycerols (TAG) after 2 h was lower for acidolysis than for the other lipase-catalyzed reactions (P≤0.05). Since no differences in final yields were detected among the reactions, chemical esterification using hydrolyzed oil could represent the best synthetic option, since it offers the advantage of positional distribution control associated with lipase-catalyzed reactions as well as rapid reaction times associated with chemically catalyzed reactions. Attempts to evaluate the positional distribution of caprylic acid using allyl magnesium bromide (Grignard reagent) were hampered by production of unknown species, which prevented accurate determination of the concentration of some key fatty acids.     

Chloroacetoxylation of oleic acid—A kinetic study

The kinetics of the addition reaction of chloroacetic acid to oleic acid (chloroacetoxylation) in the presence of sulfuric acid as a catalyst were investigated. The reactions were carried out at the same concentration of both reactants at various temperatures and catalyst content. The reaction time ranged from 30 min up to 12 h, and the reaction course was observed by determining mainly iodine value, and chlorine content of the oil samples at 30-min intervals. The experimental data fitted the reversible second-first order rate equation for bimolecular-unimolecular type reactions. The reaction constants of the forward and reverse reactions were obtained at temperatures 70 and 80°C. The effect of sulfuric acid content on the reaction constant was investigated at 70 and 80°C.     

ZnHZSM-5催化活化烷烃的研究

1 前言我国的石油资源大多属于石腊基类型,含有大量链烷烃,现在主要是将它通过管式炉高温热裂解、深冷分离之后,生产乙烯、丙烯、副产芳烃;同时也联产不少低级烃类(如C_4、C_5等)。有效地利用这些资源,既可降低生产成本,又能提高经济效益。其关键在于催化活化这     

Chemistry of miscible polycarbonate–copolyester blends

Blends of polycarbonate and the copolyester based on 1,4-cyclohexanedimethanol and a mixture of terephthalic and isophthalic acids are known to be completely miscible. This study was concerned with various chemical events which may occur in this system, particularly during melt processing. Degradation reactions were studied by both TGA and dilute viscometry techniques, and some indications of component interaction were noted. The residual titanium catalyst from the copolyester formation was found to produce color formation by interaction with phenolic end groups in the polycarbonate and to promote interchange reactions. Both events could be suppressed by deactivation of the residual catalyst with appropriate additives. An indication of the extent of interchange reactions was obtained by following the crystallizability of the copolyester component using differential scanning calorimetry.     

Glycerolysis of Crude Methyl Esters with Crude Glycerol from Biodiesel Production

Glycerolysis of crude fatty acid methyl esters (FAME) with crude glycerol derived from biodiesel production was performed. The reaction was accomplished at temperatures ranging between 160 and 200 °C and molar ratios of FAME to glycerol ranging between 1.5 and 3.0. Increasing the temperature improved the formation rate of monoglycerides (MG) and diglycerides (DG). However, increasing both the temperature and the molar ratio of glycerol to FAME diminished the formation of MG. Best results (43 % MG and 26 % DG in 10 min) were obtained at 200 °C using the lowest concentration of glycerol. The effects of soap and NaOH present in crude glycerol were controlled by carrying out the reaction with pure glycerol. In comparison with NaOH-catalyzed reactions, soap-catalyzed reactions resulted in a slower formation rate of products. However, soap-catalyzed reactions were less prone to secondary reactions, affording maximum yields of MG and DG, which were higher than those obtained with NaOH-catalyzed reactions at 180 and 200 °C.     

Reactions of ethylbenzene in the presence of toluene over external surface passivated MFI zeolite

The reactions of ethylbenzene in the presence of toluene were studied over external surface passivated MFI zeolite. With increase in extent of external surface passivation the para selectivity of both transalkylation and disproportionation reactions enhanced. The effects of mole ratio of ethylbenzene to toluene, reaction temperature and WHSV on the performance of the modified zeolite are discussed. It was observed that the high para selectivity feature of the modified zeolite is not influenced by changes in reaction conditions.     

Ionic liquid as surfactant in microwave‐assisted emulsion polymerization

The aim of this work is to study the use of an ionic liquid (IL) as surfactant in emulsion polymerization reactions and to evaluate its effect when these reactions are heated under microwave irradiation. The IL 1‐n‐dodecyl‐3‐methylimidazolium chloride was chosen to replace the surfactant dodecyltrimethylammonium bromide (DTAB) in methyl methacrylate emulsion polymerizations. The conversion evolutions and the final average diameter of polymeric particles were quite similar for reactions using the surfactant DTAB or the IL, showing that the IL acted efficiently as surfactant in emulsion polymerizations. Comparing the polymerization reactions performed under microwave irradiation and conventional heating, reaction rate enhancements were obtained for both DTAB and IL. Using a pulsed scheme, under high‐power microwave irradiation, slightly higher reaction rates and molecular weights were obtained in reactions using IL, in comparison with surfactant DTAB, indicating the existence of some specific effects linked to IL–microwaves interaction. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

An analysis of complex gas-liquid reactions in an isothermal CSTR

A mathematical model was developed for complex gas-liquid reactions with general-order kinetics in a continuously stirred tank reactor. The model equations were solved by the method of orthogonal collocation from which component concentration profiles in both the bulk and film liquid were computed. A parametric study revealed several interesting relationships between the chemical and physical parameters describing the reaction system. Specifically, the effects of mass transfer on the formation of reaction intermediates were analyzed for the case of two consecutive gas-liquid reactions over a wide range of reactor conditions.     

The kinetics of producing sulfate-based complex coagulant from fly ash

This paper studies the kinetics of reactions between iron and aluminum oxides in fly ash and sulfuric acid for the production of a complex sulfate-based coagulant. The important part of this research was to monitor the change in the concentration of product during the reaction. The ratio of concentration of ferric sulfate to aluminum sulfate during reaction, and the linearity of plots of a derived concentration of function versus time at different temperatures show that reactions of both iron and aluminum oxides in fly ash with sulfuric acid are second-order with respect to sulfuric acid concentration. Furthermore, the ratio of the concentration of the ferric sulfate to that of aluminum sulfate and the slopes of the derived concentration function versus time were used to obtain the rate constants of reactions. Finally, based on the rate constants obtained at different temperatures, the empirical Arrhenius expressions of iron and aluminum extracting reactions were derived.     

From catalysis by metals to bifunctional photocatalysis

“Catalysis by metals”, was transposed to “Bifunctional Photocatalysis”, based on noble metals deposited on titania. Both, participation (i) of the photo-active oxidic support and (ii) of the deposited metal have been successfully analyzed, delimited and associated. For both reactions involving hydrogen (Cyclopentane-Deuterium Isotope Exchange (CDIE) and alcohol dehydrogenation), the respective roles of electrons and holes were clearly put in evidence. The photogenerated electrons were found to be spontaneously transferred to the metal nano-particles because of the alignment of the Fermi levels of both solid phases. They neutralize protons H⁺ (or deuterons D⁺) into atoms before their recombination and evolution of dihydrogen (or HD). Simultaneously, photogenerated holes h⁺ neutralize anionic species in oxidation reactions responsible for the activation of organic molecules. These two anionic species were OD⁻ deuteroxyl surface groups in CDIE and alcoholate anions RO⁻ in alcohol dehydrogenation, respectively. Both reactions exhibited a stoichiometric threshold which was exceeded several hundreds of times, clearly defining the real catalytic character of both reactions. The titania-deposited noble metals appeared as auxiliaries or co-catalysts working independently of UV-irradiation for making the reaction run catalytically. Eventually, the concepts of bifunctional photocatalysis were applied to account for interphasic photocatalytic processes such as hydrogen transfer, electron transfer, photosensitization in the visible via CdS addition.     

Polymeric reaction of acrylic polymer–monomer system irradiated by low-energy electron beam. II. Effect of ester structure of acrylic polymer

Polymeric reactions of polyacrylate–benzyl acrylate (BzA) systems induced by a low-energy electron beam were investigated by changing the species of polyacrylates added to the system. The gel fraction, the proportion of BzA units incorporated into gel by infrared (IR) analysis, and the molecular weight and its distribution curves by gel permeation chromatography (GPC) were examined to elucidate the reaction mechanism for the polymer–monomer system. The GPC curves were detected by both ultraviolet (UV) and refractive index (RI). As the UV-detected GPC curves represent the benzyl groups of graft polymers and homo polymers, the polymerization reactions can be followed by GPC. Ester structures of acrylic polymers were varied in order to examine how much the ester group affects such individual reactions as crosslinking, graft polymerizations, and homopolymerizations. In the case of both polyisobutylacrylate–BzA and poly(isoamyl acrylate)–BzA systems, the crosslinking and graft reactions predominated, while in the case of poly(t-butyl acrylate)–BzA systems, homopolymerization was the main reaction. These results can be explained by the structure and reactivity of polymer radicals and viscosity of the system.     

Study of the reaction between urea and formaldehyde by dsc and 13C NMR spectroscopy

The reactions of urea with formaldehyde were studied by means of ¹³C NMR spectroscopy and differential scanning calorimetry (DSC) in acid and neutral medium, the temperature range being between 290 and 390 K. At higher pH the peak of the DSC curve splits into two peaks one of which belongs to the addition of formaldehyde to urea and the second to the subsequent condensation of the latter. For both reactions, the activation energy, heat of polymerization, reaction order and temperature maximum have been determined. The usefulness of DSC to study the kinetics of more complex polycondensation reactions was established.     

Use of Genetic Algorithm to Determine the Kinetic Model of Solid-State Reactions

Solid-state reactions take place by different rate-controlling heterogeneous processes. To find the appropriate kinetic model for a particular solid-state reaction, a genetic algorithm-based simulation technique was carried out using DTA data with a fitness function, and a computer program was developed for the same. The process was applied to the decomposition reactions of limestone and magnesite samples. It was observed that both the decomposition reactions mostly followed the Avrami–Erofeev kinetics model.     

Degradation kinetics of ascorbic acid during ohmic heating with stainless steel electrodes

Ascorbic acid degradation experiments were performed in buffer solution at pH 3.5 using a batch ohmic heater with uncoated stainless steel electrodes. The electrical conductivity of the buffer solution was adjusted using sodium chloride. The concentration of ascorbic acid was found using an HPLC technique. Kinetics of degradation can be described adequately by a first order model for both conventional and ohmic treatments, but unlike conventional heating, the temperature dependence of degradation for some ohmic treatments cannot be represented by the Arrhenius relation. During ohmic heating, power, temperature and NaCl content affect the degradation rate. A number of reactions, including electrode reactions, electrolysis of the solution, as well as reactions between electrode materials and electrolysis products may influence the reaction mechanism as well as kinetic parameters. At the highest power and salt content, citrate complexation and a significant loss of buffering capacity were noted, resulting in an increase in pH. The results underline the importance of inert electrode coatings, or the use of high frequency power for control of electrochemical reactions.     

Catalytic Production of 1-Octadecanol from Octadecanoic Acid by Hydrotreating in a Plug Flow Reactor

1-Octadecanol (stearic alcohol) has uses ranging from lubricants to perfumes. The production of 1-octadecanol from octadecanoic acid (stearic acid) was investigated in a liquid-phase trickle-bed reactor by hydrogenating octadecanoic acid using a Ni/Co/Mo sulfide catalyst. The primary reactions occurring in the reactor were the desired conversion of octadecanoic acid to 1-octadecanol and the subsequent undesired conversion of 1-octadecanol to octadecane. A model was developed to predict these two reactions. The model found to be most useful for this system was a series–parallel reaction first order in octadecanoic acid and 1-octadecanol and pseudo-zero order in hydrogen for both reactions. The activation energies of the first and second reactions were 63.7.8 and 45.6 kJ/mol, respectively. From these values, the conversion of octadecanoic acid and the selectivity to the desired product as functions of temperature, space velocity, and inlet octadecanoic acid concentration were estimated. The model predicts the maximum productivity of 1-octadecanol occurs at higher temperatures with short residence times. Parametric plots show productivity to be ≥0.48 g 1-octadecanol/g octadecanoic acid at 566 °F and a 0.1 h residence time.     

活性炭固载杂多酸催化剂的研究现状

杂多酸是一类同时具有酸催化特性和氧化一还原能力的催化剂，有着广泛的应用前景。杂多酸固载化后，能够在液相氧化和酸催化反应中把催化剂从反应介质中很方便地分离出来，且能使这类均相催化反应多相化。本文介绍了以活性炭为载体的固载型杂多酸催化剂的研究状况，包括制备方法、影响负载量的因素及负载量对催化性能的影响，文章同时阐述了有关活性炭固载杂多酸的机理分析，总结了近年来活性炭固载杂多酸催化剂的应用研究及进展。