Enzymatic hydrolysis from carbohydrates of barley straw pretreated by ionic liquids

BACKGROUND: Lignocellulosic biomass offers many potential advantages in comparison with the traditionally used sugars or starchy biomass since it is very widely available and does not compete with food and feed production. The abundance and high carbohydrates content of barley straw make it a good candidate for bioethanol production in Europe. Since biomass must be pretreated before enzymatic hydrolysis to improve the digestibility of both the cellulose and the hemicellulose biomass, the use of ionic liquids (IL) has been proposed as an environment‐friendly pretreatment of biomass. RESULTS: Different pretreatment conditions were investigated to determine the effects of the experimental conditions (temperature and time) on the enzymatic digestibility of pretreated material. The pretreatment of barley straw with 1‐ethyl‐3‐methyl imidazolium acetate treatment resulted in up to a 9‐fold increase in the cellulose conversion and a 13‐fold increase in the xylan conversion when compared with the untreated barley straw. CONCLUSION: Ionic liquid pretreatment of barley straw at 110°C for 30 min, followed by enzymatic hydrolysis, leads to a sugar yield of 53.5 g per 100 g raw material. It is then ready available for conversion into ethanol and is equivalent to more than 86% from potential sugars. The increase in saccharification was possible due to rupture of the lignin–hemicellulose linkages by treatment with 1‐ethyl‐3‐methyl imidazolium acetate. © 2012 Society of Chemical Industry     

Comparison of alkali and steam (acid) pretreatments of lignocellulosic materials to increase enzymic susceptibility: Evaluation under optimised pretreatment conditions

The alkali pretreatment of sugar cane bagasse was optimised and compared with an optimised steam (acid) pretreatment. The optimised alkali pretreatment gave an overall sugar yield of 37.4 g sugars per 100 g bagasse accounting for 43.8% of the initial xylan and 64.5% of the glucan. Potential effluent problems were identified with the alkali treatment and several strategies were suggested to minimise them, with liquor recycling showing some promise. The optimised steam (acid) pretreatment gave an overall sugar yield of 55.7 g sugars per 100 g bagasse accounting for 76.5% of the xylan and 89.5% of the glucan. The superiority of the steam (acid) pretreatment over the alkali pretreatment depends on the ability to utilise the xylose produced.     

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。     

连续酸解在硫酸法钛白生产中的应用

硫酸法钛白生产会产生大量的废水、废酸和废气,给环境造成严重的污染。通过分析硫酸法钛白生产酸解的原理,对比连续酸解与间歇酸解主反应时产生的废气排放对比,续酸解与间歇酸解的经济对比,体现连续性酸解尾气处理的优越性。     

醋酸水解玉米芯中木聚糖的动力学

利用醋酸作为催化剂水解玉米芯中半纤维素来制备还原糖,测定了温度在160-200℃、固液质量比为1∶15、搅拌速度为500 r/min下,不同水解时间水解液中还原糖的收率以及副产物糠醛的收率.利用半纤维素高温液态水的Garrote模型拟合还原糖生成过程.实验表明,该模型能够较好地描述还原糖生成过程以及副产物糠醛的产生过程...     

Glucose production by hydrolysis of starch under hydrothermal conditions

Starch was converted into glucose by hydrolysis with water under hydrothermal conditions at 453–513 K in a small batch reactor. The major product was glucose; oligomers having various degrees of polymerization, maltose, fructose, 5‐hydroxymethylfurfural and furfural were also produced. The maximum yield of glucose obtained was 630 g kg^?1 on the carbon basis at 473 K and 30 min, where the quantity of carbon unrecovered was about 50 g kg^?1, and the production of char and gaseous products was negligible. Copyright © 2004 Society of Chemical Industry     

Switchgrass pretreatment and hydrolysis using low concentrations of formic acid

BACKGROUND: Acid hydrolysis using organic acids is a promising approach for liquefying biomass without introducing any additional inorganic salt species into the reaction media. Formic acid may be a very useful acid catalyst for biomass pre‐treatment because (i) it is an effective, strong acid catalyst, (ii) it is no more corrosive than sulfuric acid, (iii) it is an organic acid, so it adds noinorganic salt species that might negatively impact downstream catalysis, and (iv) it can be produced from biomass, making ita green reagent. RESULTS: At pH_{25 °C} = 1.65, formic acid yielded high dissolution of switchgrass (52 wt%) at a high temperature (200 °C), comparable with the dissolution yield achieved using sulfuric acid. When treated 9/1 wt/wt with an 8 wt% aqueous solution of formic acid at 150 °C for 1 h, 44 wt% of switchgrass was dissolved, yielding 63 wt% of the carbohydrates from switchgrass. CONCLUSIONS: The efficiency of formic acid for the hydrolysis and dissolution of the carbohydrate fraction of switchgrass was proved and compared with other organic and mineral acids. The liquid product of pretreatment of switchgrass using formic acid at both 150 °C and 200 °C showed that 24 wt% and 28 wt%, respectively, of soluble monosaccharides after enzymatic hydrolysis consisted of glucose. Copyright © 2011 Society of Chemical Industry     

Characterization of potentially bioreactive soil organic carbon and nitrogen by acid hydrolysis

Studies determined the potential of acid hydrolysis for estimating the bioreactive fraction of organic carbon in soils (SOC). Three soils (clay loam, silt loam, and sandy loam) were hydrolyzed with 1 M or 6 M HCl under reflux for up to 24 h. Results showed that 1.7 to 3.2 % of SOC could be liberated as CO₂ from the acid hydrolysis of soil. This readily hydrolyzed fraction should be a part of the bioreactive SOC. Higher amounts of soluble SOC and N as well as CO₂ were released from all soils by 6 M HCl than by 1 M HCl. Soluble SOC and N contents in both 1 M HCl and 6 M HCl hydrolysates of all soils increased rapidly during the initial 2 hours of hydrolysis, and then increased very gradually. The amounts of CO₂-C evolved correlated with the amounts of NH₄-N released during the acid hydrolysis (r = > 0.88). The ratio of SOC to soluble N was lower in 6 M HCl hydrolysate than in 1 M HCl. Hydrolysis of soil by 1 M HCl for 4 h appeared to be a promising approach for estimating the more bioreactive pools of SOC and N. This revised version was published online in August 2006 with corrections to the Cover Date.     

甲酸催化玉米芯水解生成木糖的动力学

玉米芯是一种价格低廉、可再生的资源,其可以被用来生产高附加值的化工产品。本文主要研究在甲酸质量分数3%、液固比为10mL/g、反应温度（120～150℃）、反应时间（0～240min）条件下玉米芯中半纤维素水解过程。采用两相模型对玉米芯水解过程中木糖浓度进行拟合并得到反应过程的动力学参数。木糖降解反应的活化能大于其生成反应的活化能,这表明高温不利于木糖的生产。对得到动力学方程进行分析,获得最佳的反应条件：甲酸质量分数3%、液固比10mL/g、反应温度140℃、反应时间180min。最佳反应条件下得到的木糖浓度为26.9 g/L。     

Decrement of cellulose recalcitrance by treatment with ionic liquid (1‐ethyl‐3‐methylimidazolium acetate) as a strategy to enhance enzymatic hydrolysis

BACKGROUND: The high crystallinity of cellulose underlies the recalcitrance that this polymer presents in enzymatic degradation. Thus, a pre‐treatment step is applied in most bioconversion processes. Treatments with ionic liquids are considered an emerging pre‐treatment technology, owing to their high efficiency in solvating cellulose, over molecular solvent systems. RESULTS: Crystalline cellulose with and without ionic liquid (1‐ethyl‐3‐methylimidazolium acetate) treatment, both commercially available, were used as substrates in enzymatic hydrolysis reactions using the earlier evaluated cellulolytic system of Fusarium oxysporum. The in situ removal of the hydrolysate during reactions enhanced the reaction rate as well as the overall glucose production. Ionic liquid treatment significantly decreased cellulose crystallinity and enhanced bioconversion yields and rates. The effects of cellulose structural changes during treatment on hydrolysis rate were investigated and the recalcitrance constants were determined. CONCLUSION: The study showed that ionic liquid‐treated cellulose became more homogeneous and more easily degradable than the untreated cellulose, a conclusion that was expressed mathematically by the difference in the recalcitrance constants for the two substrates. It was concluded that glucose production from ionic liquid‐treated cellulose could achieve very high conversion yields in consolidated bioprocesses or during simultaneous saccharification and fermentation. Copyright © 2012 Society of Chemical Industry     

Protein hydrolysis under anaerobic,saline conditions in presence of acetic acid

The hydrolysis of soluble proteins in an anaerobic, saline (24 g dm^?3 NaCl) and mesophilic (37 °C) environment was studied. The inhibitory effect of a volatile fatty acid, acetic acid (HAc), on the hydrolysis rate and hydrolytic biomass activity for a model saline wastewater with a high protein load (total organic carbon, 1153 mg dm^?3 and 1572 mg dm^?3 proteins) was studied. Initial inhibitor concentrations were tested in the range of 0–2000 mg dm^?3 HAc. The microbiological characterization was performed using a total microorganism count by epifluorescence, and hydrolytic bacterial activity was determined by plate count. The protein hydrolysis was modeled according to first order kinetics. The effect of biomass on hydrolysis was analyzed by varying its concentration in the range of 42–210 mg dm^?3 volatile suspended solids. The following apparent hydrolysis kinetic constants (K_h) for proteins at 37 °C were obtained: 1.3, 0.8, 0.6, 0.2 and 0.1 d^?1 for initial concentrations of 250, 500, 750, 880, and 1000 mg dm^?3 HAc, respectively. At concentrations of HAc greater than 1000 mg dm^?3, total inhibition of hydrolysis was observed. The intrinsic hydrolysis constant ( ) at 37 °C, without inhibition, was 2.3 d^?1. The hydrolysis kinetic constant was not affected by the biomass concentration. The hydrolysis kinetics constant was filted to three models: Luong, Levenspiel and non‐competitive inhibition. The model that best represented the experimental data was Luong, obtaining an inhibition constant (K_I) of 1087 mg dm^?3 of HAc and the exponent γ = 0.54. The hydrolysis was inhibited by the presence of HAc, which corresponds to an intermediate compound of the anaerobic process. Copyright © 2004 Society of Chemical Industry     

树脂型固体酸催化水解稻草秸秆的新工艺研究

对利用树脂型固体酸催化剂催化水解稻草秸秆制备可溶性糖工艺进行了研究,单因素考察了固固比、固液比、反应温度、反应时间、秸秆目数对秸秆水解产率的影响。研究结果表明:秸秆粉碎至100目,常压下固液比(反应体系中固形物与液体质量比)为1∶10、固固比(树脂型固体酸与秸秆质量比)为1∶1、反应温度100℃、反应时间15 h为最适反应条件,在该条件下树脂型固体酸催化水解稻草秸秆反应的水解产率为32.5%。该新工艺为稻草秸秆的水解利用开辟了一条绿色环保的新途径。     

Reaction mechanisms and kinetics of xylo‐oligosaccharide hydrolysis by dicarboxylic acids

Hydrothermal pretreatment of lignocellulosic materials generates a liquid stream rich in pentose sugar oligomers. Cost‐effective hydrolysis and utilization of these soluble sugar oligomers is an integral process of biofuel production. We report integrated rate equations for hydrolysis of xylo‐oligomers derived from pretreated hardwood by dicarboxylic maleic and oxalic acids. The highest xylose yield observed with dicarboxylic acids was 96%, and compared to sulfuric acid, was 5–15% higher with less xylose degradation. Dicarboxylic acids showed an inverse correlation between xylose degradation rates and acid loadings unlike sulfuric acid for which less acid results in less xylose degradation to aldehydes and humic substances. A combination of high acid and low‐temperature leads to xylose yield improvement. Hydrolysis time course data at three different acid concentrations and three temperatures between 140 and 180°C were used to develop a reaction model for the hydrolysis of xylo‐oligosaccharides to xylose by dicarboxylic acids. © 2012 American Institute of Chemical Engineers AIChE J, 59: 188–199, 2013     

硫酸法钛白酸解尾渣工艺矿物学特性分析

采用激光粒度仪、XRD、XRF、ICP-AES、SEM-EDS、比重法、筛分法等对硫酸法钛白生产过程中酸解尾渣进行系统的工艺矿物学特性分析,旨在为回收钛资源提供理论指导。研究表明,酸解尾渣表面潮湿,液相约占45%,其中易水解的可溶钛为4.06%(以TiO₂质量分数计);固相中不溶TiO₂干基含量为17.14%,固相颗粒粒径主要分布于1～100 mm,密度为3.21 g·cm^-3,颗粒大小、形状不一,有块状、锥状及团聚絮状。通过筛分实验得知钛矿与其他杂质颗粒的粒径、密度有明显差异,少量120 mm以上颗粒含有石膏,密度约3.41 g·cm^-3;18～75 mm主要为钛铁矿,密度大于3.54 g·cm^-3,钛品位可达26%;18 mm以下颗粒主要为硅泥,密度约2.90 g·cm^-3,易团聚,与水形成黏稠物,难分离。     

Continuous production of 1,2‐propanediol by the selective hydrogenolysis of solvent‐free glycerol under mild conditions

BACKGROUND: The conversion of glycerol to value‐added derivatives is now critical, owing to the large surplus of glycerol from biodiesel production. The main objective of this work is to develop a novel process for converting solvent‐free glycerol to 1,2‐propanediol. RESULTS: Several catalysts were screened for aqueous‐phase hydrogenolysis of glycerol in an autoclave. The most effective catalysts (Ni/Al₂O₃, Cu/ZnO/Al₂O₃) were further tested for vapor phase hydrogenolysis in a fixed‐bed. Ni/Al₂O₃ did not prove as effective for the production of 1,2‐propanediol because of the high selectivity to CH₄ and CO. Over Cu/ZnO/Al₂O₃, glycerol was mainly converted to the desired 1,2‐propanediol and the reaction intermediate acetol. The production of 1,2‐propanediol was favoured at higher hydrogen pressure. At 190 °C and 0.64 MPa, near complete conversion of glycerol was achieved with 1,2‐propanediol selectivity up to 92%. In addition, a higher concentration (between 43.4% and 0.8%) of acetol was detected and an approximately stoichiometric relationship was found between acetol and 1,2‐propanediol. CONCLUSION: 1,2‐propanediol can be produced with high yields via the vapor phase hydrogenolysis of glycerol over Cu/ZnO/Al₂O₃. Furthermore, the mechanism of 1,2‐propanediol formation is suggested to proceed mainly through an acetol route over Cu/ZnO/Al₂O₃. Copyright © 2008 Society of Chemical Industry     

Influence of synthesis conditions on the production of molecularly imprinted polymers for the selective recovery of isovaleric acid from anaerobic effluents

Two molecularly imprinted polymers (MIPs) – poly(methacrylic acid‐co‐TRIM) (TRIM, trimethylolpropanetrimethacrylate) and poly(acylamide‐co‐TRIM) – were synthesized in different solvents for the selective recovery of isovaleric acid (template) generated during the anaerobic digestion process. The chemical and structural characterizations of the synthetic adsorbent were carried out by Fourier transform infrared spectroscopy, TGA and porosimetry through N₂ adsorption–desorption isotherms. The selective and adsorptive performances of the imprinted polymers were evaluated by kinetic, isothermal, thermodynamic and selectivity studies and by adsorbent reuse experiments. The poly(methacrylic acid‐co‐TRIM) synthesized with dimethyl sulfoxide:chloroform presented higher selectivity and adsorption capacity for isovaleric acid in the presence of six volatile fatty acids. The kinetic results were well adjusted to the pseudo‐nth order and intraparticle diffusion models, leading to k values of 10^?4 and 6 × 10^?5 for the best synthesis of MIPs and not‐imprinted polymers, respectively. Moreover, the Sips model best described the adsorption isotherm and generated a maximum adsorption capacity of ca 209 mg g^?1 (at 25 °C). Cycles of MIP use–desorption–reuse indicated that the selective adsorbent performed better than commercial adsorbents, losing less than 3% of adsorption capacity after three cycles. © 2018 Society of Chemical Industry