高温液态水中甜高粱渣半纤维素水解及其机理

为了回收甜高粱渣中的半纤维素衍生糖并了解其水解机理,在自行设计的Flowthrough反应器中对甜高粱渣进行了高温液态水水解,分别考察了不同反应温度和反应液流量下水解液中产物的生成情况。研究表明,相对葡萄糖和阿拉伯糖而言,木糖的生成受反应温度和反应液流量影响更大。温度高于195 ℃时糖降解加剧,总木糖浓度不断降低;低流量（5 ml?min-1）条件下生成的木糖不能被及时排出而进一步降解。通过产物分析可知,甜高粱渣半纤维素中含有典型的O-乙酰基-4-O-甲基葡萄糖醛酸基阿拉伯糖基木聚糖结构,木糖、葡萄糖、阿拉伯糖、各种低聚糖、乙酸和葡萄糖醛酸等是半纤维素水解的直接产物,糠醛和5-羟甲基糠醛等是糖类的降解产物, 甲酸等小分子酸是它们的进一步降解产物。     

甘蔗渣在高温液态水中的超微结构与组分变化

木质纤维素类物质中天然纤维素与半纤维素、木质素等组分交联形成了坚固的细胞壁,对纤维素酶水解和微生物消化表现出一定的抗性,原料预处理可以克服细胞壁抗性,提高木质纤维多糖生化转化效率.从细胞壁超微结构层次入手,对甘蔗渣细胞壁在高温液态水预处理过程中的解构机理进行了深入研究.未处理甘蔗渣细胞壁分层现象明显,由外至内分别为胞间层(ML)、初生壁(P)及次生壁(S),高温液态水预处理后各层界线变得模糊.SEM-EDXA分析表明细胞壁各层木质素分布发生了迁移,水解液中的木聚糖和木质素衍生物在细胞壁表面凝集生成类木质素滴状沉淀物.拉曼光谱分析结果显示预处理后纤维素在细胞壁各层分布趋于均质化.     

离子及表面活性剂对甜高粱秆渣酶解的影响

为了提高纤维素酶水解经高温液态水处理后的甜高粱秆渣的效率,探讨了多种阴离子、阳离子以及吐温80(Tween 80)对纤维素酶活力的影响,并初步探讨了Tween 80影响甜高粱秆渣酶解的机制。酶激活试验表明,Br^-、I^-、NO₃^-、Ca²⁺、Mg²⁺和Co²⁺对纤维素酶有激活作用,但对甜高粱秆渣的水解效率提高不明显。添加Tween 80发现,随着浓度的增加,它对纤维素酶的抑制作用增强,而Tween 80添加量为0.175 ml·(g甜高粱秆渣)^-1时,甜高粱秆渣的酶解效率由16.6%提高到37.9%。吸附试验表明,甜高粱秆渣对纤维素酶和Tween 80的吸附达到一定限度后不再上升,Tween 80能显著降低甜高粱秆渣对纤维素酶的吸附。红外光谱分析发现,木质素对Tween 80的吸附要强于它对纤维素酶的吸附。     

有机酸对甜高粱渣亚临界水解产物的影响

半纤维素的高效转化是提高甜高粱渣原料全组分利用的关键技术之一。采用亚临界水热预处理方法,并将强度因子R₀引入研究过程,考察了不同温度（160~200℃）和反应时间（10~60 min）对甜高粱渣水解反应的影响。在这基础上,进一步考察了多种有机酸（乳酸、醋酸及乳酸+醋酸）对亚临界水解效果的影响。实验表明,当强度因子lgR₀=3.96（180℃,40 min）时,采用不外加酸的亚临界水热预处理工艺得到的最大木糖浓度为4.79 g·L^-1;有机酸的加入可强化水解反应,提高木糖浓度;与单一乳酸或醋酸处理方法相比,加入同浓度的乳酸+醋酸既可以促进半纤维素水解,又可以抑制副产物生成;在温度180℃,时间40 min,乳酸+醋酸（乳酸：醋酸=6：4）的浓度1%（质量）的条件下,木糖浓度为7.92 g·L^-1。     

Extraction of bioethanol from fermented sweet sorghum bagasse by batch distillation

Extraction of bioethanol, a potential alternative to fossil fuel in the transport industry, from sweet sorghum stems [Sorghum bicolor (L.) Moench] using solid-state fermentation (SSF) technology has become a popular research topic worldwide. Because SSF technology can directly convert fermentable sugars into target products without juice squeezing and water input, this method can potentially reduce energy and water consumption. However, ethanol extraction from fermented sweet sorghum bagasse requires further investigation. We used batch solid-state distillation to investigate the optimal operating parameters in a distillation column (diameter, 400 mm) via a single-factor experiment. Results showed that the optimal steam flow rate and loading height were 8-10 kg·h^?1 and 700-1,000 mm, respectively. Under optimal conditions, an energy consumption of 3.82 tons of steam per ton of ethanol and distillate concentration of 60.9% (v/v) were obtained. The pseudo-first-order rate equation was used to describe the distillation kinetics, and good correlations were obtained. Therefore, solid-state distillation can be effectively used to extract ethanol from fermented sweet sorghum bagasse.     

Hydrolysis of sugarcane bagasse in subcritical water

In this work, a subcritical water process was used for the hydrolysis of sugarcane bagasse with the aim of producing fermentable sugars. Hydrolysis kinetics was determined using a semi-batch unit equipped with a 50 mL reactor. Different sample loads (2 and 11 g), flow-rates (11, 22, 33, 44 and 55 mL/min) and temperatures (213, 251 and 290 °C) were evaluated, while maintaining constant pressure (20 MPa). The liquefaction degree of the sugarcane bagasse was not affected by water flow rate and increased with temperature; the maximum liquefaction degree was 95% for hydrolysis at 251 °C and 33 mL/min. The total reducing sugars recovered increased with flow rate up to 23%. The hydrolysis process was completed faster at higher temperatures, requiring 16 min. Maximum monosaccharides + cellobiose + cellotriose yield was 5.6% at 213 °C and 33 mL/min. Approximately 60% of the sugars recovered were in the oligomeric form.     

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。     

Pretreatment of sweet sorghum bagasse by alkaline hydrogen peroxide for enhancing ethanol production

Effects of severe and mild alkaline hydrogen peroxide (AHP) pretreatment on ethanol production from sweet sorghum bagasse via pre-simultaneous saccharification fermentation, and the chemical structure changes of the substrates were investigated. The results showed that the bagasse pretreated by severe AHP could produce more ethanol than that of mild AHP. The maximum ethanol concentration of the bagasses from mild and severe AHP pretreatment with 8% bagasse loading was 7.642±0.140 g/L and 19.330±0.085 g/L, respectively. Moreover, the FTIR and NMR analysis illustrated that the molecule and surface structures of the pretreated bagasse were significantly changed compared with the control. The potential biomass energy production of the effluent from the pretreatment was also briefly discussed for future utilization of waste solution.The heat energy potentials of waste solution with severe and mild AHP pretreatment were 367.2 kJ/L _effluent and 327.6 kJ/L _effluent , respectively.     

热水预抽提后竹子的纤维素酶解

研究了热水预抽提后竹子的纤维素酶水解过程。经过热水预抽提的竹子,由于其结构较疏松,酶解生成葡萄糖的效率显著提高。当热水抽提H因子为1000和2000,酶解反应时间为24h时,生成的葡萄糖含量较未抽提的竹子分别提高了43%和215%,热水预抽提最优的H因子为2000。随着初始酶用量的增加,酶解生成的葡萄糖的含量也随之增加,但增加量并不与初始酶的增加量呈比例。双曲线模型可用于模拟不同初始酶用量、不同酶解时间下葡萄糖的生成规律。     

木质纤维素类生物质高温液态水预处理技术

木质纤维素燃料乙醇是可再生能源的重要组成部分,其中可发酵糖的制取技术是木质纤维素乙醇化的关键技术之一。原料经过预处理后再进行酶解被认为是最有前景的糖化方式。高温液态水预处理技术与其它方法相比显示了独特的优势,如不需添加化学试剂、降解产物少等。本文在总结了高温液态水性质的基础上,对它在生物质预处理过程中各组分(半纤维素和木质素)的水解过程及机理进行了较详细的综述和分析。最后对高温液态水预处理技术在木质纤维素糖化领域中的研究和应用前景进行了展望。     

Hydrolysis of pentosans in bagasse pith

Work has been conducted on the hydrolysis of pentosans in bagasse pith as the first part of a study of the chemistry of bagasse processing aimed at establishing an integrated industry. Bagasse pith is the fine part screened out and discarded as waste during the preparation of raw material for bagasse pulping plant. By using dilute sulphuric acid at a concentration less than 2% by weight and at a temperature lower than 165°C, pith is hydrolysed to pentoses in a yield of 80–90% based on potential pentoses in pith. Hydrolysis of pentosans in pith, within the scope of experiment, seems to be a first order reaction. However, the semi-logarithmic time plot for the hydrolysis of potential pentoses in the residue consists of two straight lines of different slope. This may be explained on the assumption that bagasse pith contains two major fractions of pentosans that are hydrolysed at different rates. Saeman's equation for hydrolysis of wood with sulphuric acid may be adapted to represent dependence of rate constant K on acid concentration C and reaction temperature T in hydrolysis of the two major parts of pentosans in bagasse pith.      

Hydrolysis of pentosans in bagasse pith

Work has been conducted on the hydrolysis of pentosans in bagasse pith as the first part of a study of the chemistry of bagasse processing aimed at establishing an integrated industry. Bagasse pith is the fine part screened out and discarded as waste during the preparation of raw material for bagasse pulping plant. By using dilute sulphuric acid at a concentration less than 2% by weight and at a temperature lower than 165°C, pith is hydrolysed to pentoses in a yield of 80–90% based on potential pentoses in pith. Hydrolysis of pentosans in pith, within the scope of experiment, seems to be a first order reaction. However, the semi-logarithmic time plot for the hydrolysis of potential pentoses in the residue consists of two straight lines of different slope. This may be explained on the assumption that bagasse pith contains two major fractions of pentosans that are hydrolysed at different rates. Saeman's equation for hydrolysis of wood with sulphuric acid may be adapted to represent dependence of rate constant K on acid concentration C and reaction temperature T in hydrolysis of the two major parts of pentosans in bagasse pith. K₁ = 6.4 × 10⁵C^1.02 exp (?6378/T) K₂ = 10.7C^0.363 exp (- 2826/T)     

亚临界水中离子液体催化蔗渣液化残渣分析

分别采用FT-IR、SEM对亚临界水中酸性功能化离子液体催化蔗渣液化残余物的主要成分及其表面形貌进行系统的分析,并对其与酸性离子液体催化剂的酸强度、反应温度、反应时间等工艺条件之间的关联规律进行了详细探讨。结果表明,蔗渣液化后的残渣主要是由木质素、难降解或部分降解的芳香类化合物组成;酸性越强、反应温度越高,蔗渣的液化程度越高,结构破坏得越彻底,液化残渣表面越粗糙。     

Hydrolysis kinetics and mechanism of adipamide in high temperature water

Adipamide (ADAM) served as a model to investigate the hydrolysis kinetics and mechanism of diamides in high temperature water. The major reaction products resulting from the hydrolysis of ADAM, primarily including adipamic acid and adipic acid, were detected. Effects of temperature, time, pressure, and pH on ADAM hydrolysis reaction kinetics have been investigated. The hydrolysis reaction is first order in ADAM at the temperature ranges investigated. The conversion is pH dependent, and three distinct regions of pH dependence exist. At low and high pH, the conversion increased rapidly with added acid and base, respectively. At near-neutral pH, however, the rate was essentially insensitive to changes in pH. The high content of adipamic acid in the reaction products at the initial hydrolysis reaction stage suggested that only one amide group was attacked at one time and then followed by transformation to a carboxyl. The reaction rate constants, average apparent activation energy and pre-exponential factor were evaluated according to the Arrhenius equation. Based on the experimental results, hydrolysis reaction scheme and mechanism were proposed.     

甜高粱乙醇产业生态系统优化与效益分析

非粮生物乙醇是我国可再生能源的发展方向.建立了包括种植、粗乙醇、精乙醇生产等环节在内的分布集中式甜高粱燃料乙醇产业生态系统,优化了不同种植集中度下粗乙醇和精乙醇企业的最优规模.系统优化结果表明:精乙醇的最优规模为5万t/a的系统,每年可减排C02超过15万t.可取得显著的经济、环境和社会效益.     

Liquefaction of sugar cane bagasse with formate and water

Sugar cane bagasse is available in large quantities in Brazil. Its liquefaction with $\text{formate}\text{inert}$ gas and $\text{base}\text{CO}$ in water is studied. The $\text{formate}\text{inert}$ gas system is the most effective under certain conditions, resulting in higher conversion and better yields of heavy oils. However, the heavy oils are highly oxygenated and solidify on standing in air. As a byproduct, considerable amounts of water-soluble, unextractable carboxylic acids are formed. Systematic studies are carried out with the $\text{formate}\text{inert}$ gas system to determine the reaction conditions appropriate for a future semi-continuous bench-scale reactor. A possible mechanism for the conversion reaction with formate is discussed.     

Stability of functionalized activated carbon in hot liquid water

Acidity and stability of activated carbon-based solid acid catalysts for aqueous-phase reactions are investigated. Carbon is acidified with liquid and gas phase methods, using nitric and sulfuric acid, hydrogen peroxide and calcination in air at 300 and 400 °C. Modified carbons are characterized by nitrogen physisorption, scanning electron microscopy (SEM), point of zero charge (PZC) measurements, Boehm titration, temperature-programmed desorption–mass spectrometry (TPD–MS), and X-ray photoelectron spectroscopy (XPS). Stability of acid functional groups under typical reaction conditions for biomass conversion is investigated by exposing carbons to hydrothermal treatment (i.e. hot liquid water). Special attention was devoted to elucidating the effect of the temperature (150–225 °C) and time of exposure (0–24 h) on the hydrothermal stability of different surface functional groups. Carbon modification by sulfuric acid generates strong acid sites in higher concentration, compared to carbon modified by nitric acid, calcination and hydrogen peroxide. In contrast to the other treatments, calcination at 400 °C increases carbon basicity. Although the concentrations of all surface acid sites decrease upon the hydrothermal treatment, this effect is not uniform. Stability of acid sites with different strengths and their chemical nature are dependent on the modification method. Strong acid sites formed by sulfuric acid treatment show a much higher stability than those formed by the other acidification procedures. The H₂SO₄-treated material retains ca. 40% of strong acid sites even after exposure to hot liquid water at 200 °C for more than 4 h. Only such strong acid sites remain on the carbon surface after exposure to hot liquid water at 225 °C.     

絮凝法处理甘蔗渣蒸煮黑液

在碱性条件下吸附絮凝处理甘蔗渣蒸煮黑液。通过实验获得适宜吸附絮凝条件为：膨润土用量120 g/L,双氰胺-甲醛絮凝剂用量6 mL/L,反应温度40 ℃,快速搅拌时间2 min,澄清时间25 h。分析表明:吸附絮凝沉淀物中除含大量木质素外,还含有氮、钾等营养元素,为制备固体有机肥料创造了条件;上层清液可作为工艺水循环使用。     

Hydrolysis of sugar cane bagasse with hydrochloric acid,promoted by metallic cations

Lithium chloride, in combination with commercial grade hydrochloric acid, is very effective in the hydrolysis of prehydrolysed sugar cane bagasse. After 10 min at 50°C the holocellulosic portion is completely dissolved and after 20 min most of the sugar oligomers are hydrolysed to monomers, making the time-and energy-consuming post-hydrolysis unnecessary. With longer reaction times the sugars start to reoligomerise and decompose. Zinc chloride is a milder promoter, requiring post-hydrolysis even after reaction for 30 min at 50°C. On the other hand, it does not decompose the sugars giving the highest sugar yields after prolonged reaction time and post-hydrolysis. Ferric chloride is mostly ineffective in the hydrolysis of cellulose but is a good promoter of the hydrolysis of the sugar oligomers, under the reaction conditions.     

高温液态水法水解木聚糖的实验研究

在自行设计的小型固定床反应器上,进行了高温液态水法水解木聚糖的实验并分析了产物.在所选温度范围内,较佳工况为160℃、70min,得到了69.26%的还原糖转化率;产物分析发现液体产物中的糖类,木三糖、木二糖和木糖居多,产物中还包含有酸类、醛类、酮类以及醇类等极性小分子产物;温度的升高导致残渣形状细碎且有发泡和烧结成球的现象.