碳基固体酸催化剂催化纤维素水解研究进展

随着能源需求增长和化石能源日渐枯竭,开发高效转化木质纤维素类可再生资源已成为国内外关注的热点。纤维素经水解可转化为多种重要能源物质和基础平台化合物,是整个生物质炼制过程的切入点。本文基于纤维素线性聚合结构,从碳基固体酸催化纤维素水解机理出发,介绍了碳基固体酸的碳源、比表面积活性官能团密度及反应介质对提高纤维素水解效率的影响,并对碳基固体酸降解纤维素的发展方向进行展望,以期为生物质水解催化转化过程所使用的碳基固体酸催化剂的设计提供参考。     

木质纤维素生物质水热液化的研究进展

对木质纤维素生物质的模型化合物(纤维素、半纤维素和木质素)的水热液化机理进行了剖析。纤维素和半纤维素降解路径主要是水解成单糖并进一步生成酸类、醛类、酮类等。木质素结构较复杂,液化产物中含有大量苯系化合物,具体木质纤维素生物质的水热液化反应更为复杂,不同的木质纤维素生物质原料水热液化产生的生物油含量不同;分析了原料种类、催化剂、反应温度、反应压力、对水热液化过程以及产品组成和收率的影响;对生物质水热液化制备生物油的研究进行了展望,认为发展木质纤维素生物质水热条件下降解的数学模型,开发新型反应器、研制催化剂,是今后生物质水热液化工程实验的发展方向。     

金属离子助催化稀酸水解纤维素工艺的研究

以小麦秸秆为原料,采用正交试验考察了硫酸浓度、Fe2+浓度、反应温度和反应时间等因素对稀酸水解纤维素的还原糖得率的影响,得到了优化的纤维素水解反应工艺组合:反应温度180℃,Fe2+浓度0.0375mol/L,硫酸质量分数1%,反应时间90min。研究了Fe2+、Ni2+、Na+、Mg2+四种金属离子对稀酸水解纤维素制备还原糖的影响,结果表明,金属离子能明显提高稀酸水解纤维素的转化率和还原糖得率,其助催化作用的大小依次为:Fe2+Na+Ni2+Mg2+,Fe2+对稀酸水解小麦秸秆制备还原糖的催化效果最佳,还原糖得率最高可达73.05%,纤维素转化率达到85.79%。     

Progress in the hydrolysis of lignocellulosic biomass for fuel-thanol production

以木质纤维素生产燃料乙醇具有原料可再生性和环境友好的优点而备受重视。本文介绍了国内外木质纤维素制取燃料乙醇中的水解工艺过程,包括浓酸水解、稀酸水解和酶水解工艺,分析了各工艺的技术特点,同时指出稀酸预处理-酶水解工艺将成为近几年国内外研究和开发的重点。     

木质纤维素水解制取燃料乙醇研究进展

以木质纤维素生产燃料乙醇具有原料可再生性和环境友好的优点而备受重视.本文介绍了国内外木质纤维素制取燃料乙醇中的水解工艺过程,包括浓酸水解、稀酸水解和酶水解工艺,分析了各工艺的技术特点,同时指出稀酸预处理-酶水解工艺将成为近几年国内外研究和开发的重点.     

Hydrolysis of sweet sorghum bagasse hemiceilulose with liquid hot water and its mechanism

引 言木质纤维素类生物质的生化转化过程包括预处理过程、水解液发酵过程和产物分离过程,而预处理过程是减少整个生化转化成本和提高生化转化效率的关键[1-3].与其他预处理方法相比,高温液态水处理(liquid hot water)(温度在170～250℃,压力高于饱和蒸气压)是一种绿色处理方法,它可以将木质纤维素类生物质中的半纤维素转化为木糖及其低聚糖,同时提高了残渣的纤维素酶解效率[4-7].该糖化工艺由于产生发酵毒性副产物少、不需要添加任何化学试剂、设备成本低等优点而受到广泛关注[8-12].就目前国内外相关报道来看,高温液态水预处理研究大都采用间歇(batch)搅拌反应器,该反应器的缺陷是反应中生成的糖类不能被及时排出从而被进一步降解.浙江大学吕秀阳等[13-16]主要针对葡萄糖、木糖、果糖和纤维素等在高温液态水中的水解动力学进行了深入研究,而针对真实生物质中的半纤维素水解机理报道比较少.     

木质纤维素制取燃料乙醇水解工艺技术进展

以木质纤维素生产燃料酒精因为具有原料可再生性和环境友好的优点而备受重视。本文介绍了木质纤维素制取燃料乙醇中的水解工艺过程,包括浓酸水解、稀酸水解和生物酶水解,讨论了各个工艺的关键技术问题。     

木质纤维素类生物质制取燃料及化学品的研究进展

木质纤维素类生物质含有丰富的纤维素和半纤维素多糖,通过微生物发酵将它们转化为能源及高附加值的化学品,对于缓解全球能源危机带来的压力和解决环境污染问题具有重要意义。介绍了木质纤维素类生物质的结构特征;评述了预处理方法,包括稀酸、高温液态水蒸气爆破、CO2爆破、氨爆、碱法、有机溶剂法、生物处理法;重点介绍由生物质生产乙醇、丁醇及生物柴油的研究现状。指出开发高效环保的预处理方法、构建耐毒高产菌株和应用连续发酵或补料批式发酵方式等是加快木质纤维素类生物质发酵利用工业化进程的关键所在。     

秸秆中木质素对其超低酸水解过程的影响

以湖北稻草秸秆为研究对象,研究了超低酸水解木质纤维素的适宜条件,测定了适宜条件下的超低酸法水解15种不同种类秸秆的纤维素及半纤维素的转化率、还原糖得率及结晶度的变化。实验结果表明:秸秆投料量3 g、硫酸投料量45 mL(硫酸质量分数0.05%)、搅拌转速500 r/min、反应温度210 ℃、反应时间10 min为适宜的水解条件。对15种不同种类秸秆的水解结果统计得到,随着秸秆中木质素含量的增大,纤维素和半纤维素的转化率都逐渐降低,还原糖得率逐渐降低;通过SEM和X衍射分析水解前后的木质纤维素结构,得到了木质素影响水解过程的方式:1)木质素含量越大,纤维素的结晶度越大,纤维素的非晶化越困难,从而影响了纤维素的水解;2)原木质素不溶于反应体系且在酸性条件下相对稳定,富木质素层的木质素阻碍反应物与产物扩散,使富木质素层内的纤维素、半纤维素水解速率降低;3)木质素含量越高,木质纤维素的富木质素层越厚、强度越大,水解时难以从颗粒表面脱落,进一步降低水解速率。     

木质纤维素预处理技术研究现状与展望

木质纤维素是自然界中最丰富的可再生资源,可用于生产燃料乙醇、生物柴油等能源产品,也是制备化学品和造纸的主要原料。木质纤维素主要由纤维素、半纤维素和木质素组成,复杂的化学结构限制了其高效利用,故必须对其进行预处理,去除木质素、半纤维素等不可溶物质,从而使其更易被酶水解成可发酵的糖,进而提高木质纤维素的降解转化率。预处理技术可以改变木质纤维原料的内部结构和表面性质,为后续的酶解糖化创造良好条件。从物理、化学、生物、联合处理等4个方面全面综述了不同木质纤维素预处理技术的研究现状,总结了其预处理效果和优缺点,并展望了其未来的研究方向,旨在为木质纤维素生物质降解利用研究提供参考。     

CONCENTRATED ACID CONVERSION OF PINE SAWDUST TO SUGARS. PART II: HIGH-TEMPERATURE BATCH REACTOR KINETICS OF PRETREATED PINE SAWDUST

A study of high-temperature, concentrated-acid hydrolysis kinetics was undertaken for pretreated pine utilizing a corotating twin-screw extruder reactor. Five different acid concentrations were prepared ranging from 5 to 30 wt.% acid. These solutions were subjected to high-temperature acid hydrolysis at 110°, 120°, and 130°C using a custom-fabricated zirconium batch reactor. A number of nonlinear and linear regression analyses were undertaken so that the concentration of less resistant cellulose, resistant cellulose, glucose, and decomposition products could be obtained as a function of time, temperature, and acid concentration. Application of the kinetic rate constants obtained from the static batch reactor hydrolysis studies demonstrates that more than 50% of the theoretical glucose available in the pine sawdust can be obtained in roughly 25 minutes and 41% of the theoretical glucose available can be achieved in as little as 3 minutes. Further analysis highlights the importance of the pretreatment technique in achieving significant quantities of theoretical glucose in a short high-temperature reaction time.     

CONCENTRATED ACID CONVERSION OF PINE SAWDUST TO SUGARS. PART II: HIGH-TEMPERATURE BATCH REACTOR KINETICS OF PRETREATED PINE SAWDUST

A study of high-temperature, concentrated-acid hydrolysis kinetics was undertaken for pretreated pine utilizing a corotating twin-screw extruder reactor. Five different acid concentrations were prepared ranging from 5 to 30 wt.% acid. These solutions were subjected to high-temperature acid hydrolysis at 110°, 120°, and 130°C using a custom-fabricated zirconium batch reactor. A number of nonlinear and linear regression analyses were undertaken so that the concentration of less resistant cellulose, resistant cellulose, glucose, and decomposition products could be obtained as a function of time, temperature, and acid concentration. Application of the kinetic rate constants obtained from the static batch reactor hydrolysis studies demonstrates that more than 50% of the theoretical glucose available in the pine sawdust can be obtained in roughly 25 minutes and 41% of the theoretical glucose available can be achieved in as little as 3 minutes. Further analysis highlights the importance of the pretreatment technique in achieving significant quantities of theoretical glucose in a short high-temperature reaction time.     

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。     

高温液态水中2,6-二氟苯腈水解反应动力学

为了开发2,6-二氟苯甲酰胺的绿色制备工艺以及探讨高温液态水中腈类物质的水解规律,研究了高温液态水中2,6-二氟苯睛无催化水解反应动力学.系统地研究了不同初始浓度、不同温度下2,6-二氟苯腈、2,6-二氟苯甲酰胺的水解反应动力学以及2,6-二氟苯甲酸的脱羧反应动力学.采用一级串联反应动力学方程拟合2,6-二氟苯腈的水解...     

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     

Cleavable Surfactants: A Comparison between Ester,Amide, and Carbonate as the Weak Bond

Cleavable surfactants, i.e., surfactants in which a weak bond has deliberately been inserted into the molecule, are of interest when remaining surface-active material at a surface can cause problems. Ester and amide bonds are established as week linkages in surfactants but these generate an acid when they hydrolyze. For some applications, acidic degradation products are unwanted. Surfactants with a carbonate bond between the polar headgroup and the hydrophobic tail are of interest for such purposes. In this article, we compare the physical–chemical properties of nonionic carbonate surfactants with those of the corresponding ester and amide surfactants. The half-lives of the different cleavable surfactants are also compared and it was found that a carbonate bond is slightly more stable to alkaline hydrolysis than an ester bond when present in otherwise identical structures. A nonionic Gemini surfactant with a carbonate bond in the spacer, which on hydrolysis decomposes into two identical single-tailed nonionic amphiphiles, is also presented. The hydrolysis kinetics for this surfactant was studied in some detail and it was found that it degrades much faster at low temperature than at higher temperature. This anti-Arrhenius type of hydrolysis kinetics is proposed to be due to the reverse solubility versus temperature behavior of ethoxylated surfactants.     

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。     

Hydrolysis of aromatic sulphonic acids in industrial effluents. II. Hydrolysis of amido-J-acid

The kinetics of the acid-catalysed hydrolysis of 6-amino-1,3-naphthalenedisulphonic acid (amido-J-acid) were measured at temperatures of 533–573 K. The only product of the reaction is 2-naphthol, the amino group being hydrolysed much faster than both sulpho groups. The hydrolysis can be described kinetically as a two-step consecutive reaction. Rate constants and activation parameters were determined.     

PTA法易水解聚酯的合成及水解性能

用精对苯二甲酸法合成了一系列易水解聚酯(EHDPET)，重点考察了共聚酯的化学结构和碱水解过程中各工艺条件对其水解性能的影响，并对EHDPET的碱水解动力学进行了初步探讨。结果表明，提高间苯二甲酸乙二酯—5—磺酸钠、第四单体等各组分含量及添加助剂可提高减量率；加大碱浓度、提高温度及延长水解时间均可加快碱水解速率。     

魔芋葡甘聚糖酶解历程反应-扩散动力学

引 言 近年来,天然多糖的酶促水解在生物能源炼制、油气开采、药物缓释、功能保健中得到广泛应用,涉及能源、资源、医药、食品等国计民生行业,其研究引起了众多学者的极大兴趣,成为各国科技战略的重要组成部分.