木质纤维素生物质催化转化为高附加值产品的研究进展

从纤维素、半纤维素和木质素三种组分的角度,综述了木质纤维素生物质催化转化为高附加值产品的研究进展。对木质纤维素各组分可转化成的高附加值产品进行了简要的分类介绍,为木质纤维素的有效利用提供重要的可行性参考途径。重点归纳总结了糠醛、酯类、多元醇、烷烃等产品由木质纤维素催化转化而来的主要条件因素,并对各类催化剂的催化性能进行了简要的分析评价。最后对如何提高木质纤维素生物质催化转化为高附加值产品的效率提出了建议和思路。     

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。     

酸性助水溶剂制备木质纳米纤维素及功能应用研究进展

木质纳米纤维素因具有制备工艺简单、环境友好、成本效益高等特点而在各领域受到广泛关注,其制备与应用已成为相关领域的研究热点。然而,木质纤维组分间的聚集结构和复杂的化学键(醚健、酯键等)结合形成了抗解聚屏障,需要对其进行预处理破除屏障。酸性助水溶剂体系具有溶解选择性高、产物易分离、可循环利用等优点,是一种高效环保的绿色预处理工艺,是木质纳米纤维素制备及高值化利用的重要预处理方法。本文首先介绍了酸性助水溶剂的概念及作用机理,综述了酸性助水溶剂体系制备木质纳米纤维素的方法及性能,讨论了木质纳米纤维素的功能化应用进展,最后总结了酸性助水溶剂体系存在的不足,并对其今后的研究方向进行了展望。     

Hydrothermal conversion of carbohydrate biomass to lactic acid

We investigated the hydrothermal conversion of the carbohydrates including glucose, cellulose, and starch to lactic acid using NaOH and Ca(OH)₂ as alkaline catalysts. Both catalysts significantly promoted the lactic acid formation. The highest yield of lactic acid from glucose was 27% with 2.5 M NaOH and 20% with 0.32 M Ca(OH)₂ at 300°C for 60 s. The lactic acid yields from cellulose and starch were comparable with the yield from glucose with 0.32 M Ca(OH)₂ at 300°C, but the reaction time in the case of cellulose was 90 s. The mechanism of lactic acid formation from glucose was discussed by identifying the intermediate products. Lactic acid may be formed via the formation of aldoses of two to four carbons including aldose of three carbons, which are all formed by reverse aldol condensation and double bond rule of hexose. This implies that carbon–carbon cleavage occurs at not only C₃? C₄ but also at C₂? C₃. © 2010 American Institute of Chemical Engineers AIChE J, 2010     

Hydrothermal catalytic conversion of biomass for lactic acid production

The production of lactic acid has increased owing to growing polymer markets, increased demand in the chemical sector and many applications in the food industry. Biomass hydrothermal decomposition is potentially a method for lactic acid production. To obtain a higher yield of lactic acid, the influence of metal ions (Zn(II), Ni(II),Co(II) and Cr(III)) on biomass decomposition in sub‐critical water (T = 300 °C) was investigated and the catalyst function in the complex reaction network of biomass degradation was discussed. In comparison with a non‐catalytic process, the addition of 400 ppm Ni(II) catalyst increased the yield of lactic acid from 3.25% to 6.62% at 300 °C and 120 s for microcrystalline cellulose. The lactic acid yield for glucose was 9.51% for 400 ppm Co(II) catalyst at 300 °C and 120 s. In the case of Cr(III) and Ni(II), the conversion of maize straw, sawdust and rice husk first increased, and then decreased from 0 to 800 ppm. For catalyst Cr(III), Zn(II) and Ni(II), the conversion of wheat bran indicated a decreasing trend. Transition metal ions have a great influence on raw materials conversion to lactic acid. In the conversion of pyruvaldehyde to lactic acid, the ionic catalyzed Cannizzaro‐type reaction would take place. Copyright © 2007 Society of Chemical Industry     

Chemicals from biomass: synthesis of lactic acid by alkaline hydrothermal conversion of sorbitol

BACKGROUND: Currently, the ‘green chemistry’ philosophy is being increasingly adopted by the chemical industry and, therefore, new production procedures of valuable chemicals from biomass‐derived raw materials are being sought. In this work, the synthesis of lactic acid from sorbitol under alkaline hydrothermal conditions is investigated by analyzing the influence on conversions and yields of temperature, NaOH/sorbitol molar ratio (MR), initial sorbitol concentration (SC) and reaction time. RESULTS: A 100% sorbitol conversion and a maximum 39.5% yield of lactic acid on a carbon basis are obtained at 280 °C, 50 min, 1.0 mol L^?1 SC and 2.0 MR. Glyceraldehyde was the only identified intermediate while formic acid, acrylic acid, acetic acid, oxalic acid and sodium carbonate were identified as over‐oxidation products, all of them in very low yields with the exception of formic acid (16% yield at a MR of 4 and 280 °C). Several plausible conversion routes of sorbitol involving dehydrations, keto‐enol tautomerisms, reverse aldol condensations, aldol condensations, Cannizzaro reactions and oxidations are proposed. CONCLUSIONS: Considering the high number of parallel conversion routes as a consequence of high functionality of sorbitol, the 39.5% lactic acid yield obtained is a good result. Total carbon mass in all identified products only justifies, at most, 50% of that in sorbitol due to the coexistence of several conversion routes resulting in a large number of products other than lactic acid. Copyright © 2011 Society of Chemical Industry     

纤维素基生物质多孔炭的制备及其超级电容器性能研究

以棉纤维素为原料,采用硝酸盐、尿素、纤维素共混后热裂解的方法制备分级多孔炭HPC样品,通过改变煅烧温度和KOH活化处理对多孔炭比表面积及孔结构进行调控。对比三个不同温度煅烧活化处理后样品的循环伏安曲线、恒电流充放电曲线、比容量等电化学参数,结果表明,4AC@HPC800样品作为超级电容器工作电极具有优良的电化学性能,其比表面积高达2433.8 m²·g^-1,在1 A·g^-1的电流密度下比容量高达234.7 F·g^-1,在大电流密度10 A·g^-1时依然有207.6 F·g^-1的比容量,具有良好的倍率性能;电极在2 A·g^-1的电流密度下循环10000次后依然有196.1 F·g^-1的比容量,表明其具有长时工作的特性。     

纤维素基生物质多孔炭的制备及其超级电容器性能研究

以棉纤维素为原料,采用硝酸盐、尿素、纤维素共混后热裂解的方法制备分级多孔炭HPC样品,通过改变煅烧温度和KOH活化处理对多孔炭比表面积及孔结构进行调控。对比三个不同温度煅烧活化处理后样品的循环伏安曲线、恒电流充放电曲线、比容量等电化学参数,结果表明,4AC@HPC800样品作为超级电容器工作电极具有优良的电化学性能,其比表面积高达2433.8 m²·g^-1,在1 A·g^-1的电流密度下比容量高达234.7 F·g^-1,在大电流密度10 A·g^-1时依然有207.6 F·g^-1的比容量,具有良好的倍率性能;电极在2 A·g^-1的电流密度下循环10000次后依然有196.1 F·g^-1的比容量,表明其具有长时工作的特性。     

影响烧结碳素管过滤器运行周期的因素

阐述了一次盐水质量、反洗与预涂质量、主体给料量、α－ 纤维素质量、安装质量和盐水流量及ＣｌＯ－ 对碳素管过滤器运行周期的影响及改进措施。     

A life cycle inventory of carbon dioxide as a solvent and additive for industry and in products

Life cycle inventories of four industrial carbon dioxide production processes are reported. The inventory data were calculated using design‐based methodology. Energy consumptions and critical emissions of the four processes are compared. Quasi‐microscopic allocation was applied to processes with multiple products. The inventory data of this study are transparent and can be used in other life cycle studies. Copyright © 2007 Society of Chemical Industry     

Aspen Plus在生物质快速热解制取燃料油中的应用进展

介绍了国内外Aspen Plus在生物质热解及后续加氢研究方向的利用情况,将其分为反应研究和工艺流程研究两部分。其中关于反应的研究较少,但证明了Aspen Plus可以模拟生物质快速热解和热解油加氢反应;研究多集中在整体工艺流程的模拟,并在质能平衡基础上对流程做了经济、环境、能耗的分析。最后总结了Aspen Plus在生物质热解加氢方向的不足和今后可以深入的研究方向。     

一步快速活化法制备生物质活性炭及其对乙酸乙酯的吸附再生

活性炭吸附法因技术成熟、简单易行、吸附效率高等优点而被广泛应用于挥发性有机化合物（VOCs）的处理中。本文以山林废弃物的野山桃核为原料,烟道废气及硝酸铁为活化剂,制备了一系列生物质活性炭,并利用固定床吸附装置对其吸附、再生性能进行了研究。利用二氧化碳和水蒸气模拟烟气,在固定流量的烟气活化氛围中进行活化,并探讨了不同硝酸铁的量对活性炭的孔隙结构及其吸附再生性能的影响。利用N₂ 吸附-脱附实验、扫描电镜、拉曼光谱和红外光谱等技术研究了活性炭详细特征。结果表明：当硝酸铁的质量分数为0.2% 时,所制备的活性炭AC-3具有最大的比表面积和平均孔径,分别为923m2/g及2.57nm。其对乙酸乙酯的饱和吸附量也最大,为973.04mg/g。利用烟气对AC-3活性炭进行活化再生处理,经过3次重复吸附-解吸再生实验,其饱和吸附能力仍可达91.5％以上,实现了废弃烟气资源化利用及活性炭的循环回收,从而达到废气治理的目标。     

不同热转化气氛下纤维素焦中有机钾的迁移特性

生物质热转化过程中钾（K）的释放会造成换热面积灰、结渣、腐蚀等技术问题。有机钾是生物质焦中K的重要赋存形式。本文研究了在Ar热解气氛和O₂反应气氛下纤维素焦中有机K的迁移行为。Ar热解气氛下,在800～1000℃都有明显的有机K释放,释放速率随温度增加明显增加,但最终都有部分有机K稳定地留在固相中。O₂反应气氛下,800℃时纤维素焦中只有少量K发生释放;随着温度的增加,K的释放比例明显增加。在900℃和1000℃ K的释放比例随时间先缓慢增加后快速增加,当纤维素焦完全氧化后,灰分中仍有明显的K释放。结合对灰分的XRD分析发现,随着纤维素焦的消耗,其中稳定存在的有机K主要转化为K₂CO₃,然后在900℃以上发生明显的气相释放。