木屑浓硫酸水解的工艺条件研究

以木屑为研究对象,进行浓硫酸水解,得到产物单糖。整个水解工艺过程分为两个步骤,即木屑和浓硫酸的混合过程和稀释水浴加热过程,分别对两个步骤中几个影响水解的主要工艺条件进行了研究。实验结果表明:酸固比(纯硫酸和木屑的质量比)对水解的影响较大,在酸固比为2时,混合过程35℃,80%(W)硫酸,反应120min,水浴过程稀释至30%,95℃,反应45min的情况下,单糖收率可以达到90%以上。     

木屑水解残渣制燃料气研究

在常压和９７３－１１７３Ｋ下进行木屑水解残渣的水蒸气化研究。证明该过程可分为残渣的快速热解和热解生成的木焦与水蒸气反庆两个阶段，在第一阶段已可达到较高的总转化率，但只有在第二阶段才级肯人高的产气量，提高温度和延长时间有助于增加产气量，但生成气热值稍有下降，碱金属催化剂的应用对提高产气量也有一定作用。     

用木屑水解残渣制备活性碳的研究

提出了用木屑水解残渣制取活性碳的设想并加以实验。实验研究了炭化和活化过程中的诸多反应影响因素。在合适的工艺条件下（炭化温度：400℃，炭化时间：60min,活化温度800℃，活化时间：400min，以Ca(OH)2作为添加矿物质），可得到碘值高于620mg/g且得率高于25％的产品。     

高温稀酸条件下木屑降解动力学研究

在高温稀酸条件下,对木屑降解的动力学进行了研究.分别考察了温度(190、210、230℃)、硫酸质量浓度(1%、3%、5%)和反应时间(0～60min)对糖浓度和5-羟甲基糠醛(5-HMF)浓度的影响.通过假设提出了拟均相一阶动力学模型,并对动力学数据进行回归,结果表明模型能较好地描述木屑水解的动力学过程.进一步得到了生物质降解,糖降解和5-HMF降解的活化能和动力学参数,这些参数对理解木屑在高温稀酸条件下的水解过程提供了重要的信息.     

水解木质素对桉木屑成型特性的影响

以桉木屑为原料,考察了添加水解木质素对其成型特性的影响。在电子压力机上进行了单颗粒压缩成型试验,分析了水解木质素添加量、水分含量、压力、粒径对成型颗粒比能耗、松弛密度、Meyer强度的影响。结果表明,水解木质素的添加能够改善桉木屑的成型效果,添加20% ~ 30%为宜,在水分含量12% ~ 14%、压力6 000 ~ 7 000 N、粒径2 ~ 3 mm条件下的成型颗粒具有较好的品质。SEM结果显示,当添加量为20% ~ 30%时,水解木质素能够均匀地覆盖在粒子表面,在一定范围内提高压力和减小粒径能够使粒子间结合更加紧密。本研究可为桉木屑成型颗粒品质的改善提供一定理论指导。     

纤维素连续催化水解研究

以氯化铁和氯化亚铁为催化剂在流体连续流动的条件下研究了木屑在稀盐酸中的水解过程。考察了水解时间和温度,催化剂浓度和组成及液固比等对糖产率的影响。证明氧化亚 催化效果比氯化铁显著,在适当的水解条件下,木屑的转化率可达７１％以上。     

稻草秸秆多酶水解条件研究

研究了稻草秸秆经过稀酸预处理后的酶水解条件,得到用于生产燃料乙醇的还原糖。试验结果表明:稻草秸秆经1%(w/w)的稀硫酸浸润,液固比(v/w)为5∶1,在121℃条件下处理60min后,每克稻草秸秆的初始水解还原糖得率达到0.187g。预处理后,在45℃,pH4.8,120r/min,48h条件下,采用酶的添加量最优配比(每克秸秆添加木聚糖酶217IU,纤维素酶5.13FPU,果胶酶25μ,β-葡聚糖酶500μ,淀粉酶150μ)时,水解产生的还原糖浓度达到最大值84.22g/L,原料水解率为41.19%。在酶水解糖化过程中,当MgSO4,Tween80的添加量分别为0.0001,0.005g时对纤维素酶有激活作用。     

高温液态水法水解稻秆的试验研究

以广州郊区的稻秆为原料,利用自行设计的小型反应器,以高温液态水的预处理方法,考查了反应时间、温度、压力、液固比、搅拌转速以及预热时间对稻秆水解的影响.实验结果发现:在200℃,压力为4.0MPa,液固比为20:1,搅拌转速500r/min,预热时间为40min时还原糖浓度达到最大值,还原糖转化率为51.85%,原料转化率达到48.18%.通过范氏分析及扫描电镜对此工况下的水解残渣进行了分析,发现半纤维素水解率达到88.90%,预处理后的原料疏松,孔隙增加,因而能够较大程度地提高后续纤维素酶水解的效率.     

木质纤维素酶水解分形动力学的研究进展

酶水解作为发酵法生产燃料乙醇的关键步骤之一,其高效的转化过程对后续糖发酵至关重要,酶水解动力学研究可为高效转化机理的研究提供理论支持。但纤维素酶水解是一个复杂的多相异质反应过程,很难用简单的动力学模型进行表征。由于酶分子表面具有分形特性,其与分形动力学具有局部相似性,因此,分形理论可为木质纤维素酶水解的复杂动力学研究提供理论基础。从纤维乙醇生产工艺出发,在分析木质纤维素酶水解机理及影响酶解效率主要因素的基础上,总结了国内外分形动力学目前用于木质纤维素类生物质酶水解过程的主要动力学模型研究进展,并对其发展趋势和应用前景进行了展望。     

稀碱法预处理对橡子壳酶水解效果的影响

首次将橡子壳作为原料,考察了碱法预处理对其化学组成变化以及纤维素酶水解得率的影响,并采用电子扫描电镜、X-射线衍射分析、红外光谱分析对橡子壳纤维结构特征进行了表征。结果表明:利用2%氢氧化钠溶液室温处理48 h时,半纤维素和木素去除率分别为29.9%和15.6%,纤维素含量达到47.0%,较处理前提高了36.2%;酶水解得率从42.8%增加至76.0%,提高了77.6%;总体葡萄糖产率达到73.5%,提高了71.7%。经过在121℃(0.15 MPa)下处理1 h,纤维素损失率较高,导致总体葡萄糖产率增幅不大。经过碱处理后,橡子壳纤维比表面积增大、表面孔洞增加,纤维结构的结晶度下降,有利于纤维素酶水解作用的进行。该试验为橡子壳酶水解工艺的进一步研究提供了依据。     

机械活化预处理对蔗渣酶解产糖影响的研究

采用机械活化方法对蔗渣进行预处理,研究其对蔗渣酶解产糖的影响。用红外光谱、X-射线衍射和扫描电镜测定预处理前后蔗渣结构及表面形态的变化,并分析其作用机理。研究结果表明,机械活化用于蔗渣预处理,可明显提高预处理后蔗渣的酶解产糖率。酶解时间为48 h时,蔗渣酶解产糖率从未处理时的19.86%提高到59.34%。蔗渣酶解产糖率的提高是由于机械活化处理使得蔗渣纤维素分子间部分氢键发生断裂、结晶度下降、表面有序结构被破坏的所致。     

稻草秸秆辐照酶解工艺优化

通过采用60Co-γ辐照处理稻草秸秆,提高稻草秸秆的酶解效果。采用离子色谱仪测定稻草秸秆酶解液中可发酵性糖的含量,对水解温度、加酶量、液固比、水解时间4个因素进行单因素试验分析,对稻草秸秆酶解条件进行优化,建立稻草秸秆辐照酶解新工艺。研究结果表明,稻草秸秆辐照剂量在0～2 000 kGy内,辐照预处理最佳剂量为1 200 kGy;得到稻草秸秆最优辐照酶解条件:预处理辐照剂量为1 200 kGy、水解温度为45℃、水解时间为36 h、液固比为60、加酶量为120 U/g。在此最佳条件下,稻草秸秆纤维素、半纤维素总转化率达71%。     

Optimizing thermomechanical pretreatment conditions to enhance enzymatic hydrolysis of wheat straw by response surface methodology

Wheat straw was pretreated with a thermomechanical process developed in our laboratory to improve the enzymatic hydrolysis extent of potentially fermentable sugars. This process involves subjecting the lignocellulosic biomass for a short time to saturated steam pressure, followed by an instantaneous decompression to vacuum at 5 kPa. Increasing of the heat induced by saturated steam result in intensive vapour formation in the capillary porous structure of the plant material and the subsequent release of the pressure to vacuum allows fixing the expanded structure. Response surface methodology (RSM) based on central composite design was used to optimize three independent variables of the pretreatment process: processing pressure (300-700 kPa), initial moisture contents of wheat straw (10-40%) and processing time (3-62 min). The process was optimised for hydrolysis yield and initial hydrolysis rate obtained by enzymatic hydrolysis on the pretreated solids by Celluclast (1.5 L). The analysis of variance (ANOVA) revealed that, among the process variables, processing pressure and processing time have the most significant effect on the hydrolysis yield and on initial rate of hydrolysis whereas initial moisture content observed significantly lower effect on the two responses. The predicted hydrolysis yield and in a lesser extent the predicted initial rate of hydrolysis agreed satisfactorily with the experimental values with R² of 96% and 86% respectively.     

Reinforced acid-pretreatment of Triarrhena lutarioriparia to accelerate its enzymatic hydrolysis

In this study, physical method reinforced chemical pretreatments of Triarrhena lutarioriparia (TL) were compared to explore the higher reducing sugar yield in subsequent enzymatic hydrolysis. Four different pretreatments, namely hydrothermal pretreatment (HTP), dilute acid pretreatment (HCl-P), ultrasound assisted acid pretreatment (HCl + U) and microwave assisted acid pretreatment (HCl + M) were conducted on TL. The structural features of TL after different pretreatments were investigated by Scanning electron microscopy (SEM), X-ray powder diffraction (XRD) and Fourier transformed infrared (FT-IR) techniques. The fractal-like theory was introduced to study the enzymatic hydrolysis kinetics of TL. Results showed that the reducing sugar yield of HCl-P reached 100.14 mg/g, showing 1.34 times higher than that of the raw. Due to the hemicellulose and lignin removal and lignocellulosic structure destruction, ultrasound and microwave irradiation strengthened the HCl-P, leading to a great enhancement of enzymatic hydrolysis of TL, especially the microwave irradiation. Moreover, the fractal-like theory was confirmed to be satisfactory for studying the enzymatic hydrolysis kinetics of lignocellulosic biomass.     

微波辅助NaOH预处理提高油菜秸秆酶解效率的研究

为提高油菜秸秆的酶解效率,试验借助于常压微波加热技术辅助NaOH预处理,并对处理条件进行了优化。结果表明,与未处理比较,经微波预处理的油菜秸秆致密结构明显破坏,利于被纤维素酶水解。微波辅助预处理的最优化条件:微波功率600 W,时间5 min,NaOH 0.1 mol/L,温度80℃,经预处理后的油菜秸秆酶解率可达28.09%,较未处理前增加2.75倍,显著提高了酶解效果。     

麦草碱性沸石催化制浆及其酶水解

采用过氧化氢进行预浸渍,以固体沸石A和B为催化剂,研究麦草氧碱法制浆对其酶水解的影响。结果表明,当制浆黑液中乙酰丙酸和甲酸的浓度分别达5.1442,6.7096mg/ml时,采用固体沸石A和B蒸煮成浆的水解得率分别为18.38%和23.16%。AMF分析表明,与表面物理结构相比,成浆纤维化学结构的改变对酶水解的影响更大。     

The steam explosion pretreatment and enzymatic hydrolysis of wheat bran

This article focused on the saccharification of wheat bran with steam explosion pretreatment and enzymatic hydrolysis. Wheat bran was pretreated with steam explosion to improve saccharification with enzymatic hydrolysis, and a maximum reducing sugar yield reached 194.6 mg/g (dry), which was about 63% higher than that of the wheat bran without pretreatment. Electronic microscope scanning and infrared spectroscopy showed that steam explosion with low pressure destroyed the structure and promoted the enzymatic hydrolysis of wheat bran effectively. Further, higher pressure produced harmful substances to hinder the saccharification and subsequent fermentation rather than increase saccharification ability of blasting bran.     

Effects of operation conditions on enzymatic hydrolysis of high-solid rice straw

In the present work, the performances of high-solids enzymatic hydrolysis of rice straw were experimentally studied. Moreover, the heat flow and weight loss of the pre- and post-hydrolysis of rice straw were measured by the simultaneous thermogravimetric analyzer. It is found that the output and yield of reducing sugar initially increased and then reduced with an increase of supplied water, hydrolysis temperature and substrate mesh, while the cellulose content in residual substrate had an opposite trends. Furthermore, a high enzyme loading resulted in a constant saccharification efficiency of cellulose. The output and yield of the sugar, 77.7 mg/(g substrate) and 0.44 g/g, were respectively achieved under the optimal conditions of the supplied water of 1.0 ml/(g substrate), enzymolysis temperature of 50 °C, rice straw of 60 mesh and the cellulase dosage of 2.0 mg/(g substrate). Simultaneous thermogravimetric analysis on the rice straw indicates that the chemical compositions of rice straw changed after enzymolysis.     

Batch-based enzymatic saccharification of sweet sorghum bagasse

To improve enzymatic digestibility and sugar concentration, sweet sorghum bagasse was pretreated with alkali and liquid hot water, and then subjected to fed-batch enzymatic hydrolysis. Scanning electron microscopy assay suggested that different pretreatment methods resulted in different composition and structure of residues; these changes had a significant influence on cellulose hydrolysis. Fresh substrate was pretreated and then added at different amounts during the first 48 h to yield a final dry matter content of 30% (w/v). For liquid hot water pretreatment, a maximal glucose concentration of 95.71 g/L, corresponding to 52.85% xylan removal, was obtained with the sweet sorghum bagasse pretreated at 184°C for 18 min. NaOH soaking at ambient conditions removed lignin up to 60%, and the subsequent hydrolysis with cellulase loading of less than 10 FPU/g DM, and substrate supplementation every few hours yield the high glucose and xylose concentrations of 114.89L and 29.93 g/L, respectively after 144 h.     

The mechanism of fiber cutting during enzymatic hydrolysis of wood biomass

The relationship between fiber dislocations and fiber cutting during the enzymatic hydrolysis of lignin-free fibers was investigated. Dislocations are morphological changes in the microfibril direction of cellulose. It was hypothesized that enzymatic activity is concentrated at dislocation sites, resulting in fiber cutting. Bleached softwood kraft pulp was analyzed during enzymatic hydrolysis (Novozynme 188 and Celluclast 1.5L) to confirm fiber cutting and explore its relationship with dislocation sites via microscopy, fiber length, and sugar determination. Results reveal that fibers were quickly cut through during enzymatic hydrolysis, resulting in shorter fiber fragments during the initial 60% of hydrolysis. Polarized light microscopy images show a relationship between dislocations and fiber cutting during enzymatic hydrolysis. Images show fibers partially cut at dislocation sites, and that there are no dislocations on cut fibers after 6 h hydrolysis. PLM and FQA data revealed that there were about seven major dislocations per fiber and each fiber was cut through about 6, and 10 times after 4 and 6 h of enzymatic hydrolysis, respectively. In combination, this data strongly implicates dislocation sites as the location of fiber cutting.