中药渣制备微晶纤维素工艺优化及其结构表征

以中药渣为原料制备生物基材微晶纤维素(MCC),利用响应面法优化制备工艺参数并分析其结构特性.结果表明:中药渣制备MCC最优工艺参数为液固比20:1(mL/g)、时间1.5 h、盐酸浓度6.9％、温度71.5℃,此条件下制得的药渣MCC聚合度为220.58、纯度为94.32％、得率为34.88％、结晶度为68.32％....     

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。     

水热条件下催化还原CO_2生成甲酸的优化研究

采用金属Al为还原剂,金属Ni和Cu为催化剂,研究了水热条件下CO_2催化转化生成甲酸的特性.针对水热还原CO_2可能存在的4个反应途径进行热力学分析,计算表明,水热条件下反应途径HCO_3~-+2H HCOO~-+H2O在热力学上最易进行,还原氢的最佳存在形态为活性H原子.考察了铝镍和铝铜水热反应体系中Ni/Al摩尔比、Cu/Al摩尔比、Al/C摩尔比、反应时间和温度等对产物甲酸浓度和碳转化率的影响,实验表明,Cu催化剂水热转化CO_2生成甲酸的碳转化率优于Ni催化剂,当Al/Cu/Na HCO_3的3组分摩尔比为8∶8∶1、温度300,℃、反应120,min时,水热还原CO_2生成甲酸的碳转化率为29.1%,.     

稻壳与木屑气化制取富氢燃气的试验研究

采用单一流化床二步气化方法,以纯水蒸气为气化剂,在流化床中进行制取氢气的工艺试验。在对试验数据进行分析的基础上,探讨了一些主要参数[如反应器温度、水蒸气/生物质(S/B)、生物质化学成分]对氢产率的影响。分析结果表明:较高的反应温度、S/B以及纤维素和半纤维素含量比较有利于氢的产出。验证试验表明:在反应温度为1000~1050℃,S/B为2.0的条件下,纤维素和半纤维素含量为74.1%的木屑(干基)的氢产率最高,为61.67g/kg。     

无外加催化剂条件下甜高粱渣汽爆预处理研究

甜高粱茎秆压榨提汁后产生的残渣是生产纤维素乙醇的优良原料。预处理是纤维素乙醇生产过程的关键环节之一。文章对甜高粱压榨剩余残渣进行了无外加催化剂的汽爆预处理研究,通过比较不同反应条件下的预处理效果、发酵抑制物糠醛的生成,及残渣水解效果,确定了最佳预处理工艺:压力为2.4 MPa,时间为120 s,在此条件下,预处理后残渣中纤维素含量达到44.71%,纤维素水解率为82.72%,而在预处理过程中糠醛产生量为1.62 mg/g,对后期酵母发酵影响小。     

亚临界乙醇条件下的纤维素热化学液化研究

以甘油为液化促进剂,在酸性催化剂条件下对微晶纤维素的亚临界液化工艺进行考察。实验结果表明:浓硫酸是较好的酸性催化剂,在微晶纤维素、浓硫酸、甘油和乙醇的质量比为1∶0.025∶2.5∶5,反应温度250℃,反应时间1h的条件下,转化率可达95.7%。对液化产物的理化性能进行分析,粘度509.3mm2/s、酸值2.51mgKOH/g和羟值784.6mgKOH/g。通过红外光谱(IR)、GC-MS、1H NMR等技术手段对产物进行分析表征。结果表明,产物含有丰富的羟基基团,粘度适宜,适用于聚氨酯发泡体系。对液化机理进行探讨。     

TS对青贮玉米秸秆与牛粪混合消化产气特性影响

为优化筛选青贮玉米秸秆与牛粪混合消化时的总固体浓度(TS),在37℃中温条件下,系统研究TS分别为10%、12%和14%时的产沼气性能、发酵液性质以及秸秆消化前后的理化特征。结果表明:青贮玉米秸秆与牛粪在TS为12%时的混合发酵产气效果优于10%和14%时,该条件下秸秆中纤维素和半纤维素的降解率分别为17.05%和45.13%。秸秆发酵前后的微观形貌和纤维素结晶度分析发现,秸秆的木质纤维结构变化明显,纤维素结晶度减小,且TS为12%时秸秆消化降解最严重,结晶指数最小。总之,适宜青贮玉米秸秆与牛粪混合发酵的TS值为12%,且消化过程中半纤维素最易于分解,但木质素几乎不被降解。     

水热条件下CO2催化棉纤维水解过程的研究

纤维素是地球上丰富的可再生资源之一,通过水解纤维素可以获得许多有价值的化合物.以脱脂棉为纤维素模型化合物,研究了水热条件下CO2催化脱脂棉的水解过程.试验结果表明:在水热条件下,CO2可以有效地催化脱脂棉进行水解反应.DSC分析表明:水解后棉纤维的软化点向高温区移动,即非晶态纤维减少;SEM图显示:在无CO2催化条件下,脱脂棉的水解反应主要是非晶态纤维的水解;在CO2催化条件下,晶态纤维素也可以被有效地水解.此外,还考察了温度、CO2压力和停留时间对棉纤维水解过程的影响.     

CaO/MgO复合固体碱预处理杂交狼尾草提高酶解率

以杂交狼尾草为原料,采用CaO/MgO复合固体碱为催化剂,通过水相环境下高温处理,研究反应条件对狼尾草酶解效率及总糖收率的影响。研究结果表明:在催化剂含量20%,温度110℃,时间80min,固液比1∶20的条件下预处理狼尾草,木质素去除率高达54.18%。加酶量为40FPU/g,酶解72h,葡聚糖收率从未处理时的41.23%增大到81.04%;CaO/MgO固体碱预处理可破坏杂交狼尾草原本的致密结构,暴露更多的纤维素,破坏纤维素中的分子内和分子间的化学基团。CaO/MgO固体碱循环使用4次后无明显失活。     

离子液体提取木质素及环氧树脂的合成

采用离子液体提取尾叶桉木木质素,以甲苯酚为酚化剂,浓硫酸为催化剂,对木质素进行酚化改性,再以NaOH为催化剂,将酚化木质素与环氧氯丙烷进行环氧化反应,合成木质素基环氧树脂。实验表明:当离子液体为[ChCl][Gly]、温度为90℃、时间为12 h、液固比为20∶1时,木质素的提取率达到93.73%,再生木质素纯度为96.3%;酚化木质素与环氧氯丙烷质量比为1∶2.5,NaOH质量分数为酚化木质素质量的20%,反应时间为3 h,反应温度为95℃,在此条件下,木质素环氧树脂的环氧值为0.364。     

Fractionating lignocellulose by formic acid: Characterization of major components

Treatment of corn (Zea mays L.) cob under mild reaction conditions (60 °C and atmospheric pressure) in 88% formic acid was an effective method for separating cellulose from hemicellulose and lignin components in lignocellulose. Most of the hemicellulose degradation and lignin removal occurred within the first 90 min. After 6 h treatment, the decomposition of hemicellulose and the recovery of lignin were over 85% and 70%, respectively. Multi-level structures of lignin and solid residues were further characterized by FTIR, XRD, TG/DTG, SEM and SEC. Peaks attributable to lignin or hemicellulose disappeared in FTIR spectra, indicating complete removal of these two components. The remaining solid residues had a higher crystalline index. The major pyrolysis temperature of corncob was increased after formic acid treatment; the molecular weight (MW) of cellulose in solid residues was higher than that in intact cobs, whereas the hemicellulose remaining in the pulp had a lower MW than the original. Lignin was extracted in an esterified form designated as formic acid lignin (FAL). FAL had two thermal decomposition temperatures (T_d) at 277 °C and 385 °C. The MW of lignin increased following formic acid treatment, which may make it a better starting material for chemical syntheses.     

Catalytic hydrodeoxygenation and hydrocracking of Alcell® lignin in alcohol/formic acid mixtures using a Ru/C catalyst

The catalytic conversion of Alcell^® lignin in iso-propanol/formic acid mixtures (1:1 mass ratio) was explored in a batch set-up using Ru/C as the catalyst (673 K, 4 h, 28% mass lignin intake on solvent). Lignin oils were obtained in good yields (71% mass yields on lignin input) and shown to consist of a mixture of mainly aromatics (10.5% mass yields on lignin input), alkylphenolics (6% mass yields on lignin input), catechols (8.7% mass yields on lignin input), guaiacols (1.3% mass yields on lignin input), and alkanes (5.2% mass yields on lignin input), the remainder being soluble higher molecular weight compounds (GCxGC-FID and GPC). The results for the catalytic experiments using formic acid were compared with those of a non-catalysed experiment and a catalytic hydrotreatment with molecular hydrogen and Ru/C in the absence of a solvent. Distinct differences in product yields and compositions were observed, and highest lignin oil yields were obtained by catalytic solvolysis (71% mass yields on lignin input) versus 18% mass yields on lignin input for non-catalytic solvolysis and 63% mass yields on lignin input for catalytic hydrotreatment. The effect of reaction time on oil yields and product composition was established and a reaction network involving depolymerisation, and hydro(-deoxy)genation pathways is proposed to explain the product yields and composition. Besides iso-isopropanol, the use of ethanol and methanol in combination with formic acid was also explored for catalytic solvolysis. Best results were obtained in methanol (4 h, 673 K) leading to a lignin oil (68% mass yields on lignin input) containing 11% mass yields on lignin input of alkylphenolics and 19% mass yields on lignin input of aromatics.     

氧化生物质制备甲酸过程中木质素结构变化的表征

表征生物质酸性氧化制备甲酸过程中木质素结构变化是木质素高值化利用的关键之一。以O₂为氧化剂,对松木粉在NaVO₃-DMSO-H₂SO₄体系中氧化生成甲酸进行研究,考察反应时间、催化剂和固液比对木质素结构变化的影响。采用高效液相色谱（HPLC）、傅里叶变换红外光谱（FT-IR）、凝胶渗透色谱（GPC）、气相色谱（GC）和二维异核单量子相干核磁光谱（2D-HSQC）对固体残渣和已溶解的木质素碎片进行分析。结果显示,在H₂SO₄浓度为0.7wt.%的NaVO₃-DMSO-H₂SO₄体系中,当固液比为1∶50时,甲酸的碳摩尔收率为75.1%。在氧化解聚过程中,木质素通过断裂C—O键被降解形成125 ~ 900 g/mol之间的碎片,而且木质素碎片中的芳环结构被氧化成醌类结构。     

Enhanced degradation of lignin in corn stalk by combined method of Aspergillus oryzae solid state fermentation and H2O2 treatment

To shorten the time of corn stalk pretreatment and increase the degradation of lignin, solid state fermentation (SSF) with Aspegillus oryzae CGMCC5992 in the presence of H₂O₂ was carried out to degrade lignin in stalk. In this study, the conditions for lignin hydrolysis catalyzed by enzymes produced in SSF for 10 days were optimized by mono-factor-at-a-time design and response surface method (RSM). The removal rate of lignin increased from 30% (before hydrolysis) to 80.3% (after hydrolysis) under the temperature of 55 ^°C, pH 6.0, water/stalk ratio of 40, and the concentration of H₂O₂ at 4% (w/w). In comparison, the removal rate of lignin after 50 days of SSF only reached 57.8%. Proteomic analysis provided support for the increased lignin hydrolysis. Fermentation with A. oryzae CGMCC5992 in the presence of H₂O₂ increased the amount of peroxidase and intracellular catalase and decreased the amount of extracellular catalase. Therefore, the method introduced in this study can significantly shorten the time of SSF and increase the removal rate of lignin.     

Synthesis and properties of lignin-highly branched poly (ester-amine) polymeric systems

Combined characteristics of hydrogen bonded/cross-linked polymer networks based on lignin motifs have been developed. This new type of polymeric material was prepared from an industrial lignin and a highly branched poly(ester-amine) (HBPEA) obtained by melt polycondensation of 1,1,1-triethanolamine (TEA) and adipic acid (AA). The lignin-HBPEA polymers were shown to be insoluble in common organic solvents and were characterized by FTIR and NMR spectroscopies. Thermo-mechanical measurements showed that melt mixing HBPEA with 40% lignin results in a flexible and tough material (T_g; 7.7 °C and E′ 3.5 GPa). The hydrogen bonding recognition was based on various hydroxyl groups in lignin and aliphatic ester groups from HBPEA. The extent of interactions could be controlled by varying the amount of lignin added. These networks were thermally reversible and have highly tunable mechanical properties that were controlled by the extent of interactions. High level of mechanical properties could be achieved through the addition of lignin-poly(ester-amine) covalent cross-links. This study shows that the poly(ester-amine) structure plays an important role in the thermo-mechanical properties. By varying the spacer length between lignin and tertiary amine unit, materials with various thermo-mechanical properties were also obtained from the same parent polymer backbone.     

四氢糠醇-稀酸体系预处理杂交狼尾草的试验研究

以杂交狼尾草为研究对象,采用四氢糠醇-硫酸体系在常压较低温度下进行预处理研究,优化该预处理体系得到最佳预处理条件为0.1 mol/L硫酸、反应温度120℃、反应时间2 h、固液比为1∶12,在此条件下残渣中纤维素、半纤维素的保留率分别为86.17%、9.01%,木质素脱除率为98.16%;对预处理残渣进行酶解,72 h时酶解率可达99.01%,比未处理原料的酶解率高2.6倍。通过使用扫描电镜、X射线衍射、红外光谱、热重分析等方法对预处理后残渣及原料的组成及结构进行分析测试,表明四氢糠醇-硫酸预处理能有效脱除木质素及半纤维素,破坏平整的原料表面结构,提高原料的酶解率。     

Effect of temperature on the fast pyrolysis of organic-acid leached pinewood; the potential of low temperature pyrolysis

In this paper, we have evaluated the potential of organic acid (mixture of acetic, formic and propionic acid) leaching of biomass and subsequent fast pyrolysis to increase the organic oil, sugars and phenols yield by varying the fluidized bed temperature between 360 °C and 580 °C (360 °C, 430 °C, 480 °C, 530 °C, and 580 °C). The pyrolysis of acid leached pinewood resulted in more organic oil and less water and residue compared to untreated pinewood over the whole temperature range. Below 500 °C the difference was most profound; for acid leached pinewood at 360 °C the organic oil was already 650 g kg⁻¹ pine with a sugar yield of 230 g kg⁻¹ pine. At this low pyrolysis temperature no bed agglomeration was observed for acid leached pine whereas at the higher temperatures tested agglomerates were found, which were identified to be clusters of fluidization sand glued together by sticky pyrolysis products (melt). Low reactor temperatures also favored the production of monomeric phenols, though their absolute yields remained low for both untreated and leached pine (maximum: 23 g kg⁻¹ pine, 80 g kg⁻¹ lignin). GPC, GC/MS and UV-fluorescence spectroscopy showed that acid leaching did not influence significantly the yield and molecular size of the aromatic fraction in the produced pyrolysis oils. Back impregnation of the removed AAEMs into leached biomass revealed that the effects of the applied acid leaching, both with respect to the product yields and bed agglomeration, can be mainly assigned to the removal of AAEMs.     

A novel staggered hybrid SSF approach for efficient conversion of cellulose/hemicellulosic fractions of corncob into ethanol

The following study reports bioconversion of corncob into ethanol using hybrid approach for co-utilization of dilute acid hydrolysate (pentose rich stream) and hexose rich stream obtained by enzymatic saccharification employing commercial cellulase Cellic CTec2 as well as in-house cellulase preparations derived from Malbranchea cinnamomea, Scytalidium thermophilium and a recombinant Aspergillus strain. Acid hydrolysis (1% H₂SO₄) of corncob at 1:15 solid liquid ratio led to removal of 80.5% of hemicellulosic fraction. The solid glucan rich fraction (63.5% glucan, 8.3% pentosans and 27.9% lignin) was hydrolysed at 10% substrate loading rate with different enzymes for 72 h at 50 °C resulting in release of 732 and 535 (mg/g substrate) total sugars by Cellic CTec2 and M. cinnamomea derived enzymes, respectively. The fermentation of enzyme hydrolysate with co-culture of Saccharomyces cerevisiae and Pichia stipitis added in sequential manner resulted in 3.42 and 2.50% (v/v) ethanol in hydrolysate obtained from commercial Cellic CTec2 and M. cinnamomea, respectively. Employing a hybrid approach, where dilute acid hydrolysate stream was added to solid residue along with enzyme Cellic CTec2 during staggered simultaneous saccharification and fermentation at substrate loading rate of 15% resulted in 252 g ethanol/kg corncob.