低共熔溶剂在木质纤维素预处理促进酶水解效率的研究进展

低共熔溶剂作为一种环境友好的新型溶剂,可高效去除木质纤维素中的木质素,同时保留大部分纤维素。此外,低共熔溶剂具有制备简单、无毒性和可循环使用等特点,在木质纤维素生物炼制生产燃料和化学品方面具有较大的工业化应用潜力。本文详细介绍了低共熔溶剂的种类和性质,总结了低共熔溶剂种类和反应条件对纤维素、半纤维素和木质素三组分物理化学结构的影响,并讨论了其对酶水解反应的促进机制。最后根据低共熔溶剂预处理存在的问题,提出基于木质纤维素结构特征和相应的预处理目的,对低共熔溶剂进行理性设计和循环利用,以实现木质纤维素低成本预处理和全组分高值化利用的思路。     

生物质水解液中糖酸分离方法的研究进展

对生物质酸水解发酵制燃料乙醇过程中关键技术糖酸分离的方法进行了综述,对中和法、溶剂萃取法、离子排斥色谱法和双极性膜电渗析法的分离工艺过程以及优缺点进行了讨论。指出生物质浓酸水解制燃料乙醇工艺中使用离子排斥色谱法进行水解液中的糖酸分离以及酸回收是经济的;在生物质稀酸水解工艺中使用双极膜电渗析法分离水解液较使用离子排斥色谱法更为经济。同时,提出采用何种分离方法应根据所采用的水解条件和工艺要求进行选择才能达到经济实用的目的。     

纤维素燃料乙醇预处理技术研究进展

木质纤维素类生物质可经过预处理-酶水解-发酵等过程转化为纤维素燃料乙醇,其不仅是粮食乙醇的有益补充,还是未来生物燃料发展的主要方向。预处理是制备纤维素燃料乙醇的关键步骤,预处理可以破坏木质纤维素原料的致密结构,提高底物与纤维素酶之间的可及性,从而提高后续的酶解和发酵效率。目前,预处理技术主要包括物理法、生物法、化学法和物理化学法。文章主要对碱法、酸法等重要的化学预处理方法进行了论述,对近年来新开发的有机溶剂和离子液体溶剂体系预处理的研究进行了重点分析,其中有机溶剂体系具有对设备腐蚀较小的优点,离子液体溶剂体系具有热稳定性和化学稳定性高的优点。目前,二者是生物质预处理技术的研究热点。     

HZSM-5催化纤维素液化的研究

以微晶纤维素为研究对象,HZSM-5为催化剂,系统考察了原料/溶剂水质量比、反应温度、反应时间、催化剂用量、催化剂硅铝比等对催化液化效果的影响。结果表明:在纤维素/溶剂水的质量比为1/20、反应温度280℃、反应时间40min、HZSM-5催化剂(硅铝比为28)用量为原料质量分数的5%时,可以得到较好的催化液化效果,且HZSM-5催化剂可以多次重复使用。     

深度共熔溶剂预处理对木质纤维素生物质作用机制的研究进展

深度共熔溶剂（DES）是一类可再生、对环境友好的新型混合溶剂体系,用于预处理木质纤维素生物质可有效去除半纤维素及木质素组分,并可保留较为完整的纤维素组分。本文综述DES预处理对木质纤维素生物质作用机制的研究进展。通常情况下,大部分DES对纤维素溶解性较差,但可改变纤维素的外貌形态;一些酸性DES对半纤维素具有良好的溶解性能;碱性DES及部分酸性DES对木质素具有优异的溶解性能,在预处理过程中木质素的结构发生解聚或缩合反应;三元DES体系在木质素提取、分离及回收等方面均展现出更多优势。DES对木质素的去除效果及作用机制受DES的构成、摩尔比、生物质类型及预处理条件如温度等多种因素的影响。理解DES在木质纤维素生物质预处理中结构与功能的关系,研究DES在预处理过程中对木质素及半纤维素去除的作用机制,有助于合理设计新的DES体系并为实现生物质三大组分的高效分离及转化奠定理论基础与技术指导。     

生物质高压液化制生物油研究进展

以生物质为原料进行高压液化制备生物油是目前生物质能领域研究的一个热点。纤维素在水中的降解是复杂的竞争和连串反应机理;在180℃以上,半纤维素就很容易水解,而且不管是酸还是碱都能催化半纤维素的水解反应;在水热条件下木质素会发生分解,生成多种苯酚、甲氧基苯酚等,这些产物可进一步被水解成甲氧基化合物。影响生物质液化产率及生物油组成的主要因素是温度、生物质类型和溶剂种类;次要因素包括停留时间、催化剂、还原性气体和供氢溶剂、加热速率、生物质颗粒大小、反应压力等。纤维素类生物质通过高压液化可以生产生物油,生物油经物理精制及化学加工可以制取车用燃料、生物气及化工产品等。生物油有轻油和重油之分,都是通过对生物质液化产物的分离精制而得到的。目前用来分析生物油的主要方法包括GC-MS(色-质联用)、EA(元素分析)、FTIR(傅里叶变换红外光谱)、HPLC(高效液相色谱)、NMR(核磁共振)、TOC(总有机碳测定)等。人们对生物质高压液化研究已经进行多年,并建立了几套工业试验示范装置。不过因为操作条件太苛刻,到目前为止还没有建立商业化装置。     

产纤维二糖芽孢梭菌的分离及其生理学性状研究

从以造纸(石灰法)废液作为甲烷发酵基质中分离出一株厌氧纤维素分解细菌。该菌琼脂表面菌落呈圆形、乳白色、边缘波状、不产生色素,在纤维素滚管琼脂培养基上培养5天后菌落直径达1.5—2.0毫米。细胞呈直或微弯杆状、0.8—0.5×3.2-4.5微米、周毛、形成末端球形芽孢。革兰氏阴性,最适生长pH7.0,最适生长温度35℃。发酵纤维素、葡萄糖产生氢、二氧化碳、醋酸及微量丙酸、乳酸。     

低共熔溶剂对甘草渣的预处理研究

以甘草渣为研究对象,9种氯化胆碱为氢键供体的低共熔溶剂（DES）作为溶剂,对甘草渣进行预处理,研究不同反应温度与反应时间对甘草渣理化特性的影响。醇类DES中,乙二醇/氯化胆碱的预处理效果最好,在150 ℃,1 h条件下最大木质素脱除率为38.33%。酸类DES中,乳酸/氯化胆碱在100 ℃,1 h处理条件下木质素脱除率最高为40.87%,纤维素保留率高达95.28%。碱类DES中,乙醇胺/氯化胆碱在4 h,150 ℃处理条件下木质素脱除率最大为73.02%。物理表征结果说明,DES可破坏纤维素分子内氢键,断开碳水化合物与木质素的酯键,使纤维素可及表面积增大,有利于后续利用。     

我国“膜”科学研究取得突破塑料制品的白色公害将被清除

我国“膜”科学研究取得突破塑料制品的白色公害将被清除北京有一个“膜”科学应用研究所，攻克了当今世界七大关键技术之一的能够降解的植物纤维膜。这种膜可以取代不能降解的聚乙烯塑料膜。从１９８８年起研究人员以麦秸、稻草、甘蔗渣、树枝子、芦苇和其它富含纤维素的...     

二醋酸纤维素脱盐膜制备及耐污染性能研究

膜法脱盐技术在电厂水处理中的广泛应用受到膜污染的限制。为此本研究选用二醋酸纤维素为制膜材料,采用相转化法制备脱盐膜,通过对溶剂的选择,优化膜的分离性能与耐污染性能。以蛋白质(BSA)、腐殖酸(HA)、十二烷基硫酸钠(SDS)、十二烷基三甲基溴化铵(DTAB)等为模型污染物,以水渗透通量回复率与脱盐率为指标,详细考察所制备脱盐膜的抗污染性能。研究发现以丙酮和N-甲基吡咯烷酮为混合溶剂时,二醋酸纤维素膜表现出较好的分离性能与耐污染性能,通量回复达到了95%左右,脱盐率几乎不受影响,具有缓解水处理过程中膜污染产生的潜力。     

Solvent fractionation of renewable woody feedstocks: Organosolv generation of biorefinery process streams for the production of biobased chemicals

A new organosolv biomass fractionation process (Clean Fractionation, CF) for the separation of lignocellulosic raw material into cellulose, hemicellulose and lignin has been developed. The lignocellulosic material is separated with a ternary mixture of methyl isobutyl ketone, ethanol and water in the presence of an acid promoter, which selectively dissolves lignin and hemicellulose, leaving cellulose as an undissolved solid. The resulting single phase liquor is treated with water giving an organic phase containing lignin and an aqueous phase containing hemicellulose. For woody feedstocks, the yield of the cellulose fraction across all separations averaged 47.7 wt% (±1.1). Representative separations gave cellulose fractions with average Klason lignin contents of 2.0% at acid concentrations of 0.1 M H₂SO₄ or greater. Little or no galactose, mannose or arabinose is observed in the cellulose, and at an acid concentration of 0.2 M, average xylose contents as low as 0.22% were observed. Average glucan contents for representative cellulose samples of 92.7% were observed, and rose as high as 98.2% for separations using 0.2 M H₂SO₄. Glucan contents as high as 97% were also observed if the cellulose was bleached using either a QPD or QPDE sequence. The average yield of the lignin fraction was 18.3 wt%. Representative lignin samples gave an average Klason lignin value of 91% with selected lignin samples exhibiting residual sugar levels of <0.5%. The aqueous hemicellulose fraction contains a higher level of non-sugar components, but can be purified by ion exchange chromatography.     

Incorporation of thermally labile additives in polyimide carbon membrane for hydrogen separation

In this study, three thermally labile additives microcrystalline cellulose (MCC), nanocrystalline cellulose (NCC), and polyvinylpyrrolidone (PVP) were introduced to the P84-copolyimide (PI) solution. PI-based carbon tubular membranes were fabricated using dip-coating method, followed by sample characterizations in order to determine their structural morphologies, thermal stability and gas permeation performance. NCC was added as the membrane pore former for the hydrogen gas (H₂) separation. While tests involving pure H₂ and N₂ permeation were carried out at room temperature, carbon membranes were carbonized at a final temperature of 800 °C, with the heating rate of 3 °C/min under the Ar flow. Excellent result of H₂/N₂ selectivity was obtained with value of 430.06 ± 4.16. Addition of NCC has significantly increased the number of pore channels in the membrane, hence, contributing to high gas permeance and selectivity. NCC has shown potential as a good additive for an enhanced hydrogen separation performance.     

Impact of stabilization environment and heating rates on P84 co-polyimide/nanocrystaline cellulose carbon membrane for hydrogen enrichment

These past few decades, the separation of various gas mixtures problems in order to obtain high purity gases can be overcome by the introduction of membrane-based technology. This current research was focusing on the development of tubular carbon membranes (TCMs) from polymeric precursors for the separation of hydrogen and nitrogen. The fabrication of TCMs involved the dip coating technique and was using P84 co-polyimide as the main precursor by blending of nanocrystaline cellulose (NCC) as an additive. It was believed a slight adjustment on time, temperature, or environment of the carbonization protocol for the commercially available PI/NCC membranes can alter the final properties of the carbons produced. The modifications on the carbonization parameters such as stabilization conditions and heating rates during fabrication of PI/NCC-based carbon membranes could also affect their gas separation performance. A large variety of TCMs for gas separation have been developed by simple carbonization of a PI/NCC deposited on a ceramic tubular support. Herein, in this study, the effect of different heating rates (1, 3, 5, and 7 °C/min) and stabilization environment (Argon, Nitrogen, and Helium) were investigated for all resultant TCMs. As a result, it was observed that stabilization under Argon environment with heating rate of 3 °C/min produced carbon membranes with the best H₂/N₂ separation and the highest selectivity of 434.68 ± 1.39, respectively.     

转炉钢渣磁选过程含铁矿物的分离特征

采用磁选提铁的方法探讨了钢渣中含铁物相的分离特征,对比了分离出的精矿、尾矿微观结构和成分的变化规律,结果表明:转炉钢渣中铁的赋存状态主要是纯的铁氧化物和RO相为主.9.6 × 104 A/m磁场强度下,磁选产物主要为金属铁颗粒和铁的氧化物.9.6 × 105 A/m强磁场条件下,RO相被大量分离提取.磁选处理后,转炉渣...     

浑水进口位置对分离鳃的水沙分离效率的影响

为探明浑水进口位置对分离鳃水沙分离效率的影响,对分离鳃和普通管开展动水循环条件下7种不同浑水进口位置的水沙分离试验。研究结果表明,分离鳃的水沙分离效率均比普通管高,不同浑水进口位置的水沙分离效率是普通管的1.23～3.87倍;当浑水进口位置距离分离鳃底部480、580、760mm时,水沙分离效率随时间的变化规律包括缓慢增大、快速增大及缓慢增大三个阶段,而其他工况下仅有缓慢增大阶段;浑水进口位置距离分离鳃底部为760mm时,水沙分离效率最高,其值为34.12%。     

Behavior of Fe and P during reduction magnetic roasting-separation of phosphorus-rich oolitic hematite

Fe–P separation and the behaviors of Fe and P in separation process of high-phosphorus oolitic hematite ore from western Hubei province in China were studied. Various parameters, including reducing temperature and time, dosage of the pulverized coal, grinding fineness of magnetic separation feed, magnetic field intensity and grinding fineness of flotation feed were investigated. Experimental results show that the iron concentrate with total iron grade of 61.78% and phosphorus content of 0.23% was obtained from an oolitic hematite ore containing 47.71% iron and 0.874% phosphorus by magnetization roasting-magnetic separation-reverse flotation separation process under the proper conditions. In the magnetization roasting process, the Fe and P grade was rising by 1.30% and 11.49%, respectively; the forms of Fe and P are oolite hematite (magnetite) and collophanite which mainly distributed inside oolite structure and a small portion being distributed in other shapes. In the magnetic separation process, the Fe is from 48.33% to 58.52%, and P grade was slipped to 0.70% from 0.97%, however, the forms of Fe and P have no change compared with the roasted ore. In the reverse flotation separation process, Fe is from 58.52% to 61.78%, phosphorus is from 0.70% to 0.23%, the flotation concentrate mainly contained fine iron mineral and phosphorus is finely disseminated inside the iron mineral.     

生物油溶剂萃取以及萃取-柱层析分离法的研究进展

对生物油的分离与分析能更好的了解生物油的组成结构以及特性,为其综合利用提供理论依据和指导。本文综述了近年来国内外在溶剂萃取以及萃取-柱层析相结合分离生物油方面的研究进展,认为萃取-柱层析结合的方法分离生物油能取得较好的分离效果,对生物油的实际应用具有重要的意义。     

食品工业中固液分离技术节能问题

叙述了食品工业中有关固液分离技术的特点与能耗情况,提出了食品工业中固液分离技术的节能对策。     

两种新型分离鳃沉淀池沉淀试验及沉降效果研究

采用试验方法分别对封闭式与敞开式分离鳃沉淀池进行静水和动水的水沙分离沉降试验,发现两种沉淀池在静水沉淀时出水浊度随时间变化可分为浊度迅速减小阶段和浊度缓慢减小阶段;在动水沉降时,水力负荷对浊度变化有很大的影响,水力负荷愈小出水浊度值愈小,当水力负荷达到一定值时两种沉淀池里的分离鳃将失去作用,与普通沉淀池处理效果相同;但总体上封闭式分离鳃沉淀池的净水效果优于敞开式分离鳃沉淀池。