微波辅助[Bmim]FeCl_3Br催化稻草秸秆纤维素水解为还原糖的研究

本文研究了稻草秸秆在微波辅助、离子液体Bmim]FeCl3Br中水解为还原糖的条件。在微波功率为240W,物料/催化剂比为5∶4g·g-1,微波处理时间为130min,物料/水比为1∶40g·mL-1的条件下,还原糖收率为28.06%。     

微波辅助[Bmim]FeC13Br 催化稻草秸秆纤维素水解为还原糖的研究

本文研究了稻草秸秆在微波辅助、离子液体Bmim]FeC13Br中水解为还原糖的条件。在微波功率为240W,物料,催化剂比为5：4g·g^-1,微波处理时间为130min,物料／水比为1：40g·mL^-1的条件下,还原糖收率为28．06％。     

微波辐射下盐酸催化纤维素水解研究

采用微波辐射与盐酸催化相结合对纤维素进行水解,探讨了微波功率、酸浓度和反应时间等工艺条件对纤维素水解过程的影响,在微波功率为500 W,盐酸浓度为20%的条件下,反应50 min水解液中还原糖浓度达到最大值36.7 g·L-1,比平行实验中常规水浴加热所得还原糖浓度提高了14.4 g·L-1.对微波条件和常规条件下水解残余物的红外分析表明,微波条件与常规条件下的水解残余物结构基本一致,保留了很好的纤维素特征.     

微波和超声波辅助下半纤维素柠檬酸酯的制备

为了制备环境友好型材料,研究了微波和超声波辅助条件下半纤维素柠檬酸酯的制备。结果表明,微波和超声波能够加快半纤维素改性的反应速率,微波功率为460 W,处理时间为3 min,柠檬酸为0.01 mol,DMAP为0.2 g时,产量达到最大值;超声波功率为25 W,处理时间为20 min,柠檬酸为0.01 mol,DMAP为0.2 g时,产量达到最大值。FTIR、1H NMR、DSC分析,表明半纤维素与柠檬酸酯化后的产物具有很高的粘性和韧性,采用其作膜材料和粘合剂具有很高的环境保护作用。     

微波条件下纤维素在磷酸中的快速水解

微波条件下磷酸快速水解纤维素得到葡萄糖,而葡萄糖可替代甲醛制备新型环保PF(酚醛树脂)。以微波功率、反应时间和反应温度为试验因素,以葡萄糖产率为考核指标,采用正交试验法优选出磷酸水解纤维素的最佳工艺条件。结果表明:各因素对磷酸水解纤维素的影响依次为反应温度>反应时间>微波功率;当微波功率为240 W、反应温度为100℃和反应时间为40 s时,水解液中葡萄糖含量为80.7%,葡萄糖浓度为40.35 g/L;超声波能加快纤维素在磷酸中的溶解速率,常温时纤维素完全溶解在磷酸中需要72 h,而微波条件下纤维素完全溶解在磷酸中只需2 h。     

超声波辅助纤维素酶水解制备纳米纤维素

以人纤浆为原料,利用超声波辅助纤维素酶水解制备纳米纤维素（NCC）,在单因素试验基础上,采用正交试验优化NCC的制备条件,并通过透射电镜（TEM）、X射线衍射（XRD）、红外光谱（FT-IR）、热重（TG）和Zeta电位测定对NCC的结构和性能进行了分析与表征。研究结果表明：NCC的最佳制备条件为酶用量为人纤浆质量的7%、50℃条件下酶解反应10 h,此时纳米纤维素的得率可达62.3%。TEM表征显示制备的纳米纤维素呈短棒状,纳米纤维素之间相互交织形成网络结构;XRD分析表明纳米纤维素的晶体结构并未发生改变,仍为纤维素Ⅰ型,结晶度由人纤浆的54.2%增大到73%;FT-IR分析显示纳米纤维素仍保持天然纤维素的化学结构;热重分析表明纳米纤维素的热稳定性较纤维素原料显著提高;Zeta电位测试结果表明纳米纤维素在水介质中具有良好的分散稳定性。     

稻草纤维素水解机理及工艺条件的研究

以稻草秸杆为纤维素原料,用2%氢氧化钠对其进行预处理,选用纤维素酶作为催化剂对纤维素进行酶法水解,采用DNS法测定纤维素水解液还原糖的含量,并计算其糖化率。探讨了纤维素酶水解稻草秸秆纤维素的反应机理,研究了纤维素酶的添加量、反应温度、pH、反应时间、振荡等因素对稻草纤维素酶水解的影响。实验结果表明,当固液比为1∶30、纤维素酶添加量为40 mg、50℃、pH 4.8、振荡反应12h,纤维素酶解液的糖化率可达40%。     

纤维素酶水解纤维素还原糖的测定

对不同类菌种在不同培养基中的酶活性进行比较,测定了其底物得糖率,最高达８．５９％,可对纤维素酶的进一步研究提供实验参照。     

微波辅助稻草预处理提取纤维素实验条件研究

以稻草秸秆作为纤维素原料,将微波加热应用于稻草秸秆的预处理过程中,考察了微波功率和作用时间对实验结果的影响。结果表明,用10g/L NaOH溶液预处理并在微波中火辅助加热的条件下,当3%H₂O₂溶液、0.5%NaOH溶液和0.5%H₂SO₄溶液处理40 min后,纤维素收率最高,达60.39%。     

利用同步冷却强化微波驱动纤维素水解成糖效率

利用带有同步冷却微波驱动对经预处理的纤维素进行了水解成糖,详细探讨了微波功率、水解时间、纤维素用量及催化助剂对水解成糖效率的影响.结果 表明,该法能有效强化微波驱动作用,促进纤维素水解成糖效率提升.此外,通过延长反应时间、减少纤维素含量及使用催化助剂等方式均能提升对微波的利用能力,利用氧化锆实现最佳的水解成糖效果,反应...     

生物质碳磺酸的制备及其催化水解纤维素性能

对炭化温度、磺化条件以及不同碳源等因素对生物质碳磺酸的酸量、表面结构及催化纤维素水解活性的影响进行了系统研究,并采用XRD、BET、 FT-IR和SEM等对碳磺酸的微观特征进行了分析,发现合适的炭化温度和炭化程度是制备高酸量碳磺酸的关键,在相同的炭化和磺化条件下,用不同生物质碳源制备得到碳磺酸的酸量接近,微观结构不同对纤维素水解催化活性有一定影响。在本文研究的几种碳磺酸中,具有蜂窝大孔结构的竹炭碳磺酸呈现比较突出的催化活性。将竹粉在400℃炭化3 h,然后在180℃下磺化8 h,得到竹炭碳磺酸的总酸量和磺酸量分别可达5.34和1.25 mmol·g^-1。     

Kinetic study of cellulose hydrolysis with tungsten-based acid catalysts

Tungsten plays an important role in transforming cellulose to C2 C3 polyols. In previous reports, the research focus was mainly on the C C cleavage reactions of cellulose catalyzed by various tungsten-containing catalysts, but less on its catalytic role in cellulose hydrolysis although it is usually considered as the rate-determining step in cellulose conversion. In this article, the method of determining kinetics parameters for hydrolyzing cellulose into glucose was developed. The effects of reaction temperature, different tungsten-based acid catalysts, and H⁺ concentration on reaction rate of hydrolyzing cellulose into glucose were quantitatively addressed. The relevant reaction rate equations with using H₃O₄₀PW₁₂, H₄O₄₀SiW₁₂, and H₂WO₄ as tungsten acid catalysts were obtained in developed batch continuous stirred tank reactors and validated by experimental data. The simulating analysis indicates that the reaction mechanism of cellulose hydrolysis can change with the temperature. H₃O₄₀PW₁₂ is the best candidate catalyst for obtaining the maximum glucose concentration.     

Acid hydrolysis behaviour of microbial cellulose II

A mutant strain of Acetobacter xylinum produces cellulose of anomalous band-like form (‘native band’), and this material has been found to be cellulose II, presumably having a folded-chain structure (according to recent work by Kuga et al.). In addition to the previous results of electron diffraction, X-ray analysis showed that this band material was composed of virtually pure cellulose II. We have studied the acid hydrolysis behaviour of this material to obtain additional evidence for the proposed structure. When hydrolysed with 1 N hydrochloric acid at 100°C, the degree of polymerization (DP) of the material decreased rapidly from 322 ( ) to 18.3 ( ). The latter value (levelling-off DP) corresponds to the observed width (10 nm) of strand-like constituents of the band material. The sample dissolved in and regenerated from 8.75% aqueous sodium hydroxide lost its original characteristic morphology and became irregular-shaped agglomerates. The leveling-off DP of this regenerated sample was 55.2 ( ), a typical value for common regenerated celluloses. These findings as a whole strongly suggest that the cellulose molecules in the native band are selectively cleaved at sharply folded parts by acid, producing fragments of the length of folding periodicity.     

Microcrystalline-cellulose hydrolysis with concentrated sulphuric acid

The effects of temperature (25–40°C), H₂SO₄ concentration (31–70% (w/v)) and the acid/substrate relationship (1–5 cm³ of H₂SO₄ per g⁻¹ of cellulose) on the solubilization rate of microcrystalline cellulose and on the glucose production rate have been analysed. The solubilization process was by determining reducing groups present in solution. For acid/substrate relationships of more than 1 cm³ g⁻¹ and H₂SO₄ concentrations of greater than 62% (w/v), the acid promoted the total solubilization of the cellulose in the form of chains with a low degree of polymerization within 4 h. The solubilization demonstrated zero-order kinetics in which the specific rate and time of total solubilization are a function of the variables in operation. Glucose was produced according to a mechanism of two consecutive first-order pseudo-homogeneous reactions. The values of the kinetic constants k₁ and k₂ have been correlated with temperature, the H₂SO₄ concentration and the acid/substrate relationship.     

微波辅助棉花秸秆稀酸水解糖化工艺研究

采用微波辅助稀酸法对棉花秸秆进行水解糖化。探索了微波辐射温度、微波辐射时间、料液比及硫酸浓度对秸秆水解糖化效果的影响。结果表明,微波辅助棉花秸秆稀酸水解糖化的最佳糖化工艺条件为:微波辐射温度80℃,微波辐射时间50min,料液比1∶16g/mL,硫酸浓度3.0%。各影响因素对还原糖收率的影响顺序为:料液比微波辐射温度硫酸浓度微波辐射时间。在最佳糖化工艺条件下,还原糖收率为3.17%。     

Microwave-assisted catalyst-free hydrolysis of fibrous cellulose for deriving sugars and biochemicals

Microwave (MW) assisted catalyst-free hydrolysis of fibrous cellulose (FC, cellulolysis) at 200°C promoted a cellulose conversion of ca. 37.2% and quantitative production of valuable C5/C6 sugars (e.g., glucose) and the according platform biochemicals (e.g., 5-hydroxymethylfurfural), corresponding to an overall selectivity of 96.5%. Conversely, conventional hydrothermal cellulolysis under similar conditions was not effective, even after 24 h, carbonising the FC. Based on the systematic study of MW-assisted cellulolysis, the specific interaction between water molecules and macroscopic FC under the MW irradiation was proposed, accounting for the interpretation of the experimental observation. The kinetic energy of water molecules under the MW irradiation facilitated the C–C (in the non-hindered surface –CH₂OH groups) and C–O–C bond breaking (inside the cellulose cavities) in FC, producing primary cellulolysis products of xylose, glucose and cellobiose.     

玉米秸秆衍生碳基固体酸的制备及其催化纤维素水解糖化

以玉米秸秆为原料,通过碳化-磺化法制备了碳基固体酸（CSA）,采用XRD、FTIR、XPS、SEM、阳离子交换与返滴定法等手段对其结构形貌进行表征,并考察了制备条件对固体酸表面活性基团含量与催化活性的影响。以NaOH/尿素冻融预处理后的纤维素为底物,研究了CSA催化纤维素水解糖化的效果与条件。结果表明：NaOH/尿素冻融预处理能够有效辅助固体酸催化纤维素水解,在350℃碳化2h、100℃磺化5h条件下制备的CSA催化性能最好,其酸量达3.94mmol/g,其中磺酸基、羧基、酚羟基含量分别为1.09mmol/g、1.36mmol/g、1.49mmol/g。在m(CSA)∶m(纤维素)=3∶1、水解温度200℃、水解时间为0.5h的条件下,纤维素水解还原糖得率与转化率分别为47.1%和63%。CSA循环利用3次催化活性下降不大。本研究可为废弃生物质原料制备的固体酸催化纤维素水解转化利用提供科学参考。     

纤维素的酶水解糖化

纤维素为自然界存在最多的再生有机资源，能水解成葡萄糖，加工成食品、燃料、化工产品等。酸和酶都能催化水解，但酶法效果好，所得水解液的纯度高。多年来对于纤维素的酶法水解研究工作很多，但还有若干问题有待解决，尚未发展成适于工业生产应用的好工艺。本文扼要地综述纤维素的酶水解机理和纤维素物料的应用工艺。纤维素酶系内切葡聚糖酶、外切葡聚糖酶和β-葡萄糖甙酶的混合物，这三种酶协同起水解作用。纤维素物料不纯，还有伴生物半纤维素和木质素共同存在，需要预先处理，破坏纤维素的结晶性，提高水解效能，分离开半纤维素和木质素，加以好的利用，提高经济效益。