草酸水解甜高粱秸秆渣的Saeman动力学模型

利用草酸作为催化剂水解甜高粱秸秆渣制备木糖,测定了不同温度下的木糖收率和副产物糠醛产量;依据半纤维素水解的Saeman模型,计算得到了木聚糖水解和木糖降解的动力学数据,其活化能分别为5.89×104,1.38×104J/mol。分析结果表明:木聚糖水解反应速度快,但是生成的木糖容易发生降解;模型最优化反应条件为125℃和77min,实验得到的木糖收率为52.11%。草酸作为一种有机酸,能够用于催化半纤维素水解制备木糖,副产物糠醛的产率较低。     

Pilot‐plant production of xylo‐oligosaccharides from corncob by steaming,enzymatic hydrolysis and nanofiltration

This paper reports a pilot‐plant production process for xylo‐oligosaccharides (mainly xylobiose and xylotriose) from corncob meal by steaming treatment followed by enzymatic hydrolysis and nanofiltration. The effects of corncob meal pretreatment, steaming temperature and time were investigated in order to obtain maximum extraction of xylan and to minimize the autohydrolysis of xylan into xylose. The enzymatic reaction was carried out using Aspergillus niger AN‐1.15 endo‐xylanase at 55 °C and the optimum enzymatic hydrolysis time was 5 h. The conventional downstream processing for purification of xylo‐oligosaccharides was incorporated with nanofiltration technology, giving benefits of energy saving and removal of monosaccharides. The final product from 40 kg of corncob meal was 10 dm³ of xylo‐oligosaccharide syrup (800 g dm^?3 total sugar), containing 74.5% xylobiose and xylotriose. Copyright © 2004 Society of Chemical Industry     

近临界水中鱼肉水解制备氨基酸的反应动力学

利用鱼肉蛋白制备氨基酸不但具有经济效益,而且为生物质资源高效利用提供技术支持。采用HL-F(0.2 L+1.5 MG)/30 MPa-IIA超临界水反应装置,在无催化剂、反应温度分别为220,240,260℃,反应时间为30 min条件下,对鱼肉蛋白在近临界水中水解为氨基酸的反应动力学进行了实验研究。用AAA-Direct氨基酸分析仪测定不同反应时间中氨基酸总产率,以酸水解鱼肉蛋白得到的氨基酸量为完全水解标准。在水过量的情况下,得到了鱼肉蛋白水解率宏观反应动力学方程。结果表明鱼肉蛋白水解动力学的级数为1.614 7,220,240,260℃下的反应速率常数分别为0.001 7,0.004 5,0.009 7,活化能为145.125 kJ/mol,前置因子A为9.475 7×109,为工业化生产提供了基础数据。     

Kinetic modeling of hemicellulose hydrolysis in the presence of homogeneous and heterogeneous catalysts

Kinetic models were developed for the hydrolysis of O‐acetyl‐galactoglucomannan (GGM), a hemicellulose appearing in coniferous trees. Homogeneous and heterogeneous acid catalysts hydrolyze GGM at about 90°C to the monomeric sugars galactose, glucose, and mannose. In the presence of homogeneous catalysts, such as HCl, H₂SO₄, oxalic acid, and trifluoroacetic acid, the hydrolysis process shows a regular kinetic behavior, while a prominent autocatalytic effect was observed in the presence of heterogeneous cation‐exchange catalysts, Amberlyst 15 and Smopex 101. The kinetic models proposed were based on the reactivities of the nonhydrolyzed sugar units and the increase of the rate constant (for heterogeneous catalysts) as the reaction progresses and the degree of polymerization decreases. General kinetic models were derived and special cases of them were considered in detail, by deriving analytical solutions for product distributions. The kinetic parameters, describing the autocatalytic effect were determined by nonlinear regression analysis. The kinetic model described very well the overall kinetics, as well as the product distribution in the hydrolysis of water soluble GGM by homogeneous and heterogeneous catalysts. The modelling principles developed in the work can be in principle applied to hydrolysis of similar hemicelluloses as well as starch and cellulose. © 2014 American Institute of Chemical Engineers AIChE J, 60: 1066–1077, 2014     

Intensifying chitin hydrolysis by adjunct treatments – an overview

Chitin is, after cellulose, the most abundant organic natural polysaccharide on Earth, being synthesized as a dominant component in the exoskeletons of crustaceans, among other sources. In the processing of seafood for human consumption, between 40 and 50% of the total raw material mass is wasted, causing a significant problem for the environment owing to its slow degradation. Efforts to find uses for chitin derivatives, particularly their oligomers, have intensified since these chemicals are highly functional and offer a wide range of applications, especially as antimicrobial agent. As a consequence, some adjunct treatments, either chemical or physical in nature, have been employed to assist acid and enzymatic hydrolysis. This work provides a detailed review of the methods employed to intensify the formation of chitin oligomers, particularly focusing on the adjunct treatments used (microwave, ultrasonication, steam explosion and gamma irradiation), and an evaluation of the yield and characteristics of the oligomers formed. Adjunct treatments are more suitable for enzymatic hydrolysis since these treatments modify the chitin structure, and enhance the hydrolysis rate and yield of the oligomers, under milder reaction conditions. For future research, it would be worth trying pre‐treatments like the application of high‐pressure to chitin in order to lower its crystallinity. © 2017 Society of Chemical Industry     

聚琥珀酰亚胺的水解动力学过程

合成聚天门冬氨酸阻垢剂时,都要经历中间产物聚琥珀酰亚胺(PSI)水解生成聚天冬氨酸钠盐这一步骤。研究探讨水解温度、反应时间、NaOH浓度和NaOH用量对聚琥珀酰亚胺水解产物聚天冬氨酸阻垢率的影响。通过正交试验,发现反应时间对水解产物聚天冬氨酸的阻垢率影响最大,水解温度影响较小;得到最佳水解条件为:水浴温度60℃,时间30 m in,NaOH浓度为2 mol/L,NaOH用量为20 mmol,即在此条件下制备的聚天冬氨酸阻垢率最高。根据实验数据,推测聚琥珀酰亚胺的水解动力学过程属于连串反应。     

醋酸甲酯水解的反应动力学

针对醋酸甲酯水解悬浮催化蒸馏工艺的要求,对杂多酸铵盐用作醋酸甲酯水解反应催化剂的反应动力学做了研究。研究表明,磷钨酸铵催化醋酸甲酯水解反应为二级可逆反应,采用拟均相模型回归了该水解反应的动力学方程,求得其活化能为E₊=52.02 kJ·mol^-1,E_-=44.7 kJ·mol^-1。使用磷钨酸铵在100 ℃下醋酸甲酯水解正反应速率常数k₊=12.84 L²·（mol·min·g）^-1,明显高于现有工业催化剂强酸性阳离子交换树脂在其最高使用温度下的速率常数值6.453 L²·（mol·min·g）^-1,有望开发成为悬浮催化蒸馏醋酸甲酯水解催化剂良好前景,为以后的工业试验提供了依据。     

Reaction kinetics and mechanism of catalyzed hydrolysis of waste PET using solid acid catalyst in supercritical CO2

Hydrolysis of waste poly(ethylene terphthalate) (PET) using solid acid catalyst in SCCO₂ is presented in this work for the first time. The mechanism of PET chains scission was proved to be a combination of chain end and random chain scission by Fourier transform ‐ infrared spectroscopy (FT‐IR) and titration analysis. A new reaction kinetics model of PET hydrolysis in SCCO₂ was setup by introducing the Arrhenius equation into an ordinary reaction rate equation, the frequency factor and apparent activation energy were expressed in terms of temperature and CO₂ pressure, respectively. With this reaction kinetics model, the effects of temperature, and pressure were investigated. An interesting mechanism was proposed to describe the reaction process that both water molecules and hydroniums were carried and penetrated into the amorphous regions of the swollen PET by SCCO₂, subsequently hydrolysis reaction preferentially took place in the amorphous regions of both surface and bulk of PET matrix. © 2014 American Institute of Chemical Engineers AIChE J, 61: 200–214, 2015     

生物质稀酸水解动力学及其反应器的研究进展

木质纤维素类生物质经过稀酸水解可制取可发酵性糖,进而形成糖平台,生产纤维素乙醇等能源和化工产品。不同类型和结构的反应器中,原料的水解行为不同,被水解的效果也就不同。本文从稀酸水解反应器和反应动力学两方面入手,综述了近年提出的木质纤维素类生物质稀酸催化动力学模型和反应器。通过比较不同反应器的水解效果,推测出多步处理、逆流过程、动态反应是木质纤维素类生物质稀酸高效水解反应的发展趋势。     

Acidic and basic hydrolysis of poly(N‐vinylformamide)

Poly(N‐vinylformamide) (PNVF) was synthesized and hydrolyzed to poly(vinylamine) (PVAm) in both HCl and NaOH solutions. The hydrolysis kinetics and the equilibrium hydrolysis were examined experimentally at different temperatures, polymer concentrations, and acid‐ or base‐to‐amide molar ratios. The hydrolysis kinetics strongly depended on temperature, polymer, and HCl or NaOH concentrations, but showed little dependence on PNVF molecular weight. The acid hydrolysis of PNVF exhibited limited conversions because of the electrostatic repulsion among the cationic amine groups generated during hydrolysis and proton hydrates. In the basic hydrolysis, complete amide conversions were observed when the NaOH/amide molar ratios were greater than unity. The effects of temperature and PNVF concentration on the equilibrium amide conversion appeared to be negligible in both acidic and basic hydrolysis. The equilibrium conversions of base hydrolysis were higher than those of acidic hydrolysis under the same reaction conditions. At NaOH/amide ratios of less than unity, the equilibrium hydrolysis experiments revealed that one base molecule could induce the hydrolysis of more than one amide group. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3412–3419, 2002     

间戊二烯和顺酐反应动力学

C5和顺酐反应合成粗甲基四氢苯酐是生产甲基四氢苯酐及甲基六氢苯酐的关键步骤.为了研究C5中间戊二烯与顺酐反应动力学,选择合适溶剂并设计单因素多水平方案,考察了顺酐与间戊二烯摩尔比(0.4-1.1)、反应温度( 15-45℃)、溶剂(甲基四氢苯酐、甲苯和丙酮)等因素对反应的影响,测定了间戊二烯与顺酐反应的动力学数据.依据...     

Covalent immobilization of biological molecules to maleic anhydride and methyl vinyl ether copolymers—A physico‐chemical approach

The covalent grafting of biological molecules to copolymers of maleic anhydride and methyl vinyl ether (MAMVE) has been used in various applications in diagnostics. To tentatively elucidate the phenomena involved in the control of the immobilization of oligodeoxynucleotides and proteins, the physico‐chemical properties of MAMVE copolymers were investigated. Because the grafting mixture contains water, to allow dissolution of the biomolecules without loss of biological properties, the anhydride‐based copolymer evolves from a neutral to a negatively charged macromolecule due to hydrolysis of the anhydride moities. The properties of both hydrolyzed and nonhydrolyzed polymers were investigated. As demonstrated by light‐scattering measurements in batch, the copolymers showed some level of aggregation in DMF, DMSO, and aqueous DMSO. The presence of aggregates was confirmed by size‐exclusion chromatography in DMF. However, partial deaggregation occurred for the lowest molecular weight sample, on adding 1% w/v of LiBr. The nonhydrolyzed copolymers exhibited a rigid conformation in a 5% water/DMSO mixture, as well as their hydrolyzed counterpart at a low ionization degree. The rate of the hydrolysis reaction was shown to be dependent on the pH of the reaction medium and on temperature. The activation energy of the hydrolysis reaction was 14 kJ/mol, and the rate constant in the order of 10⁻⁴ s⁻¹. On the basis of these data, the effect on the grafting reaction of biomolecules of different parameters such as ionic strength and the nature of the solvent, along with some other results were interpreted in terms of interactions between the synthetic and bioactive macromolecules. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 927–936, 1999     

Genipin‐cross‐linked chitosan‐based hydrogels: Reaction kinetics and structure‐related characteristics

The main aim of this work is the synthesis and characterization of cross‐linked chitosan systems. Chitosan hydrogels can be prepared by physical or chemical cross‐linking of polymer chains. Chemical cross‐linking, leading to the creation of hydrogel networks possessing improved mechanical properties and chemical stability, can be achieved using either synthetic agents or natural‐based agents. In this work, the cross‐linker Genipin, a naturally derived compound, was selected because of the lower acute toxicity compared to many other commonly used synthetic cross‐linking reagents. In particular, the chemical stabilization of chitosan through genipin cross‐linking molecules was performed and characterized by calorimetric analyses (differential scanning calorimetry), swelling measurements in different pHs, and ionic strength. The reaction kinetics was carried out by means of rheological measurements, and both the activation energy (E_a) and the reaction order (m) were calculated. The hydrogel analyses were carried out at different concentrations of genipin (GN1 and GN2). The results were used to evaluate the possibility to use the chemical cross‐linked chitosan–genipin hydrogel for biomedical applications. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42256.     

Water‐soluble cellulose oligomer production by chemical and enzymatic synthesis: a mini‐review

This mini‐review focuses on the production of water‐soluble cellulose oligomers. They are easier to handle than cellulose while still having some very interesting cellulose features. Their production is not trivial and they are thus seldom commercially available or are available at high prices and only in small quantities (100 mg or less). The goal of this mini‐review is to describe various routes to obtain these cellulose oligomers. Several examples of chemical or enzymatic synthesis and enzymatic or acidic depolymerization are presented. All the pathways considered are then compared according to several criteria: polymerization degree, yield, availability and cost of reagents, reaction time, etc. As most of the pathways produce a mixture of cellulose oligomers, techniques to separate them according to their length are also discussed. © 2017 Society of Chemical Industry     

NKC-9离子交换树脂催化醋酸甲酯水解动力学研究

用间歇搅拌釜式反应器对醋酸甲酯在离子交换树脂NKC-9上的水解动力学进行了实验测定,考察了反应温度、水酯物质的量比和催化剂用量对醋酸甲酯水解率的影响。在消除内外扩散影响的条件下,得到了拟均相反应条件下的醋酸甲酯水解动力学方程。     

Gold‐catalyzed synthesis of dicarboxylic and monocarboxylic acids

Vicinal dihydroxy derivatives of oleic acid, methyl oleate, and erucic acid were converted by oxidative cleavage to the respective di‐ and monocarboxylic acids according to an environmentally benign process carried out in the presence of supported gold catalysts and molecular oxygen as oxidant in an aqueous‐basic medium. Au(0) nanoparticles with particle sizes between 0.5 and 4.1 nm were deposited as catalytically active species on different oxidic supports. The influence of the catalyst composition and morphology as well as of the reaction conditions on conversion of dihydroxy fatty acids and yields of products were investigated. Thus, the reaction of 9,10‐dihydroxystearic acid catalyzed by Au/Al₂O₃ leads to azelaic acid (86% yield) and pelargonic acid (99% yield).     

Kinetics and simulation of the imidization of poly(styrene‐co‐maleic anhydride) with amines

The imidization of poly(styrene‐co‐maleic anhydride) with amines may improve some of its end‐use properties. The objective of this study was to examine the mechanism and kinetics with aniline (ANL) as an amine of the preparation of poly(styrene‐co‐N‐phenyl maleimide). The reaction was carried out in a tetrahydrofuran solution at 25–55°C and in an ethylbenzene solution at 85–120°C. The extent of the reaction was determined by conductance titration, a new and simple method. Two consecutive reactions were involved in the imidization: ring opening to produce an acido‐amide group and ring closing to form a corresponding imide group. The imidization rate was greatly influenced by the reaction temperature and the molar ratio of ANL to the anhydride. A model for the imidization kinetics over a wide range of reaction temperatures and concentration ranges was developed and validated. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2744–2749, 2006     

TGH-3Q型羰基硫常低温水解催化剂及应用

研究了太原理工大学开发的TGH－3Q型COS水解催化剂上的动力学行为。实验表明,这种改进型催化剂在温度40～180℃范围显示很高的催化活性和抗氧中毒能力。该催化剂已成功用于氨厂和甲醇厂的气体净化,使用寿命超过三年。根据用无梯度微型反应器和色谱仪获得的结果,其水解反应的本征速率可表达为：对于大颗粒催化剂,宏观速率可表示为该催化剂的耐毒害能力与其上沉积的硫／硫酸盐沉积学密切相关。在所提出的机理的基础上给出了催化剂因氧毒害而失活的动力学模型。