超低马来酸水解纤维素的试验研究

以定量滤纸为纤维素模化物,在3种超低酸浓度和4种温度下进行了马来酸水解的多点取样实验,以还原糖收率为指标得到较佳工况,并进一步通过间歇实验确定酸浓度0.1%、液固比20:1、温度220℃、压力4MPa、搅拌速率500r/min、反应时间55min为较优工况,可得到还原糖收率、还原糖转化率和原料转化率分别为32%、66%和48%。硫酸水解的较佳工况比较,发现马来酸存在下还原糖降解较弱,糠醛类的相对含量比硫酸存在时减少24.57%(48.22%:72.79%)。马来酸水解纤维素产糖多为聚糖;残渣依然具有纤维素特性,但结晶度较原料降低17%,对后续的酶解及发酵有利。     

微波加热水解糠醛渣制备乙酰丙酸的优化研究

以SO_4~(2-)/TiO_2-ZrO_2新型固体酸作为催化剂,采用微波加热方法加压水解糠醛渣制备乙酰丙酸。利用响应面分析法对反应条件进行优化。确定最优水解工艺条件为200.8℃,催化剂用量4.8%,固液比15.17:1,反应时间62.7 min,在此条件下乙酰丙酸的计算产率为24.78%,实际产率为25.02%。     

生物质制备新型平台化合物乙酰丙酸

实验考查了利用玉米秸秆为原料,在高温稀酸的条件下制备乙酰丙酸的工艺。根据Box-Behnken实验设计方法,选取反应温度、硫酸浓度、液固比和反应时间为影响乙酰丙酸产率的4个主要因素,分别在三水平条件下进行了27次试验。在此基础上建立了二次方程的模型,R2=0.9145显示了模型具有较好的拟合度。进一步通过响应面分析得到了优化的工艺条件:温度206.20℃,硫酸浓度3.90%,液固比15.50,反应时间37.35min。在优化的工艺条件下,玉米秸秆经水解后,最终的乙酰丙酸产率为10.74%,与模型估计值接近。     

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.     

稀酸预处理玉米秸秆条件优化的试验研究

采用稀硫酸对玉米秸秆进行预处理,采用DNS法测定玉米秸秆水解液中还原糖的含量,对水解温度、水解时间、稀硫酸质量分数、固液质量比4个因素进行单因素试验分析,再通过正交试验对预处理条件进行优化.试验结果表明,最佳预处理条件:水解温度为121℃,水解时间为1 h,稀硫酸质量分数为0.6%,固液质量比为10%.     

生物质酸催化两步水解反应的研究

以松木木屑为原料,在自行设计的连续水解反应装置中进行稀硫酸催化连续水解的研究。通过正交试验法对木屑水解的反应条件进行优化,得到分别以木糖和葡萄糖为目标产物的较优工艺条件;以正交试验得到的工艺条件为基础,对木屑两步水解反应进行单因素分析,得到的最佳工艺分别为:反应温度170℃,反应时间5min,酸浓度1%,液固比7和反应温度190℃,反应时间7min,酸浓度3%,液固比9;通过分析半纤维素和纤维素的水解情况,探讨半纤维素水解对纤维素水解的促进作用机理。     

生物质稀酸连续水解的研究

以生物质为基础的酒精生产转化过程主要有两部分:木质纤维生物质中的纤维素被水解生成还原糖和用还原糖的发酵生产酒精.考察了影响稀硫酸连续水解的主要因素:温度、稀硫酸质量分数、停留时间.实验结果表明,温度对水解的影响最大,停留时间次之,稀硫酸质量分数影响较小.升高温度可有效地减少停留时间,得到较高的糖质量浓度.当温度为200℃、稀硫酸质量分数为1.0%、停留时间为6min、液固比为10L·kg-1时,可得到比较理想的水解效果.     

旧瓦楞纸箱和桉木片稀硫酸水解糖化对比研究

利用稀H2SO4对旧瓦楞纸箱(OCC)和桉木片进行水解糖化对比研究,采用正交试验法对各影响因素进行了优化,得到OCC最佳水解工艺:硫酸质量分数为4%,水解温度为180℃,水解时间为40 min,液固比为12(mL/g),还原糖得率为36.70%;桉木片最佳水解工艺:硫酸质量分数为4%,水解温度为180℃,水解时间为60 min,液固比为12(mL/g),还原糖得率为33.81%。在同等条件下,水解OCC还原糖得率明显高于以桉木片为原料进行的水解。利用傅里叶变换红外光谱对水解前后的OCC和桉木片红外结晶指数以及基团结构变化进行了分析,发现水解前后OCC在3 400 cm-1吸收峰强度以及红外结晶指数(N.O’KI)都低于水解前后桉木片,说明再生植物纤维OCC比原生植物纤维更加有利于水解,这与试验结果相一致。     

亚铁离子催化棉纤维常压两段酸水解研究

以脱脂棉作为纤维素模型物,以总还原糖得率为考察指标,在纤维素常压两段酸水解的基础上,对FeSO4·7H2O助催化剂进行了研究,对浓硫酸质量分数、酸固比(ml/g,下同)、预处理温度、预处理时间、水固比(质量比,下同)、助催化剂添加量6个水解条件进行分析。单因素试验表明,当浓硫酸质量分数为60%、预处理温度为60℃、预处理时间为3h、酸固比为12∶1、水固比为180∶1、助催化剂添加量为0.23%时,水解效果较好,总还原糖得率可达15.18%。与未添加催化剂的常压两段酸水解相比,添加催化剂后,Fe2+能够在一定程度上促进纤维素的水解,并能有效抑制葡萄糖的降解,总还原糖得率可提高将近30%。     

草酸酪氨酸离子液体水解小麦秸秆制备还原糖的研究

以小麦秸秆为原料,考察草酸酪氨酸离子液体对小麦秸秆的低温高效水解性能。研究离子液体种类、离子液体用量、反应温度、反应时间4个因素对总转化率、葡萄糖收率、木糖收率等评价指标的影响。草酸酪氨酸离子液体水解秸秆的最佳工艺条件为:反应时间3 h,反应温度90℃,离子液体用量0.4 mmol,此条件下的总还原糖收率为86.3%。所制备的草酸酪氨酸离子液体具有良好的循环利用性能,在5次重复使用之后,其对小麦秸秆转化率仍较高。     

Genetic variability in Cynara cardunculus L. domestic and wild types for grain oil production and fatty acids composition

This paper aimed to study the genetic variability within different types of Cynara cardunculus L., domestic and wild types, for their grain oil amount and oil fatty acid composition.The grain oils were extracted from 8 domestic cardoons and 4 wild cardoons, by Soxhlet method, and obtained oils were characterized for palmitic, stearic, oleic and linoleic acids by gas chromatography.The oil amount, resulted on average of accessions 216 g kg⁻¹ DM with a good range of variability (CV = 11.7%). Unsaturated acids (oleic and linoleic) predominated over saturated ones (stearic and palmitic acids), the chemical characterization of extracted oil, showed the main compound (as % of analysed fatty acids), averaged for all populations, was linoleic acid (44.5%), followed by oleic acid (42.6%), palmitic acid (9.8%) and stearic acid (3.1%). In particular referring the oleic acid wild cardoon populations showed a mean value of 289 g kg⁻¹ oil, against a mean value of 472 g kg⁻¹ oil showed by domestic cardoon accessions. Three of the studied domestic cardoon (‘DC1’, ‘DC3’ and ‘DC7’) showed values higher than 795 g kg⁻¹ oil, while all the other accessions had concentration lower than 370 g kg⁻¹ oil.The three types of domestic cardoon ‘DC1’, ‘DC3’ and ‘DC7’ showed a fatty acids profile similar to genetic modified sunflower oil, representing new genetic material that potentially could be used for high quality biodiesel production, characterised by a low Iodine Number.     

Measurement methods of carbohydrates in dark fermentative hydrogen production- A review

The purpose of the present study is to review the methods of carbohydrates determination in the dark fermentative hydrogen production process. The measurement of carbohydrates in dark fermentation was carried out with techniques of chromatographic (high-performance liquid chromatography, ion chromatography, and gas chromatography), colorimetric (phenol-sulfuric acid, dinitrosalicylic acid, anthrone-sulfuric acid, l-tryptophan-sulfuric and boric acid, and P-hydroxyphenyl), enzymatic (GOD-PAP enzymatic or glucose oxidase method, and commercial assay kit), electrophoretic (capillary electrophoresis), iodometric (starch-iodide), and COD index. The method of carbohydrates measuring must be accurate, inexpensive, safe, and simple to use. The advantages and shortcomings of these techniques are presented and their application in dark fermentative hydrogen production is studied. Literature survey shows that the colorimetric assay followed by the chromatographic technique was extensively employed to determine the concentration of carbohydrates in dark fermentation.     

Effects of phosphotungstic acid on performance of phosphoric acid doped polyethersulfone-polyvinylpyrrolidone membranes for high temperature fuel cells

Heteropoly acids have been employed to increase the proton conductivity of phosphoric acid (PA) doped polymer membranes for high temperature polymer electrolyte membrane fuel cells (HT-PEMFCs). In this work, we develop a new composite membrane based on phosphotungstic acid (PWA) doped polyethersulfone-polyvinylpyrrolidone (PES-PVP) matrix, forming PWA/PES-PVP composite membrane for HT-PEMFCs. The homogeneous distribution of PWA on the PES-PVP membrane enhances its mechanical strength. In addition, there is a strong interaction between PWA and PA that is confirmed experimentally by the attenuated total reflectance Fourier Transform Infrared spectroscopy and semi-empirical quantum mechanics calculation. This enhances not only the PA uptake but also the proton conductivity of the PWA/PES-PVP composite membrane. ¹H nuclear magnetic resonance spectroscopy results elucidate that the high proton conductivity of the PA doped PWA/PES-PVP membranes is due to their higher proton content and mobility compared to the pristine PA doped PES-PVP membrane. The best results are observed on the PES-PVP composite membrane with addition of 5 wt% PWA, reaching proton conductivity of 1.44 × 10^?1 S cm^?1 and a peak power density of 416 mW cm^?2 at 160 °C and anhydrous conditions. PWA additives increase the proton conductivity and cell performance, demonstrating significantly positive effects on the acid-base composite membranes for high temperature polymer electrolyte membrane fuel cell applications.     

Effects of concentrations of NaCl and organic acid on generation of hydrogen from magnesium metal scrap

The study systematically investigates a catalyst-free method of producing H₂ by mixing low-grade Mg scraps (LGMS) in aqueous organic acids. A concave downward relationship exists between the hydrogen yield and the citric acid concentration in seawater. The H₂ yield was highest when the seawater contained 30 wt% citric acid. Activation energy for the H₂ generation in citric acid-added seawater was calculated. H⁺ mobility and H⁺ concentration in citric acid aqueous affect the total H₂ yield, causing that the highest yield occurred at some intermediate citric acid concentration. A concave downward relationship existed between the H₂ yield and NaCl concentration in citric acid solution. NaCl concentration had strong effect on H₂ yield in citric acid solution but did not have the effect on the H₂ yield in acetic acid solution. The H₂ generation rate from the Mg scraps in 15 wt% acetic acid solution evidently exceeded that in 15 wt% citric acid solution although the two solutions each had approximately equal moles of dissociable hydrogen atoms.     

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。     

Investigating how biomass hydrolysis derivatives inhibit H2 production by an isolated Clostridium beijerinckii

This study evaluates how fermentation inhibitors derived from biomass, namely 5-hydroxymethylfurfural (HMF), levulinic acid (LA), and formic acid (FA), affect H2 production by a Clostridium beijerinckii strain. The specific fermentative H2 production rate (μH2), bacterial cell growth rate (μ), and substrate (glucose) consumption rate (μS) during fermentation helped to estimate which HMF, LA, and FA concentrations inhibited 50% of the rates (IC50). IC50 for μ was 2.4, 2.7, and 1.4 g/L for HMF, LA, and FA, respectively. HMF inhibited H2 production the most potently and favored the lactate and ethanol pathways. Butyric acid was the only metabolite to be detected in the presence of LA or FA, which attested that these inhibitors completely inhibited the acetate pathway. The glucose consumption rate was the least affected by the inhibitors, and FA was more potent than HMF and LA. This information should be useful for more appropriate biomass feedstock application in fermentative H2 production.     

Bioenergy potential of duckweed (Lemna gibba L.) biomass

This work illustrates the bioenergy potential of Lemna gibba cultivated on urban wastewater. A reactor (25 L) was established and changes in wastewater and duckweed characteristics were estimated at the end. The reactor showed relative growth rates (RGRs) of 7.47 g/m²d, 10.6 g/m²d, and 13.63 g/m²d after the 1st, 2nd, and 3rd weeks with chemical yield rate (g/m² d) of starch, protein, and lipid of 4.96, 7.68, and 1.90, respectively. The proximate analysis showed 10.03% moisture, 13.23% ash content, 63.96% volatile matter, and 14.73% fixed carbon. The elemental composition (%) of biomass was as follows: C = 41.67, H = 3.57, N = 3.67, S = 0.83, and O = 32.83. The dried biomass showed a high content (%) of energy molecules: total sugar (38.0), starch (24.5), and lipid (9.3). Gas chromatography of the extracted lipid presented high contents of C16:0-palmitic acid (37.68%), C18:2-linoleic acid (18.11%), and C18:3-linolenic acid (33.76%) in duckweed. Results suggested the potential of Lemna as feedstock for renewable energy operations.     

Whey waste as potential feedstock for biohydrogen production

In-house isolate Clostridium sp. IODB-O3 was exploited for biohydrogen production using cheese whey waste in batch fermentation. Analysis of cheese whey shows, it is enriched with lactose, lactic acid and protein components which were observed most favourable for biohydrogen production. Biohydrogen yield by IODB-O3 was compared with the cultures naturally occurring in waste solely or in combinations, and found that Clostridium sp. IODB-O3 was the best producer. The maximum biohydrogen yield obtained was 6.35 ± 0.2 mol-H₂/mol-lactose. The cumulative H₂ production (ml/L), 3330 ± 50, H₂ production rate (ml/L/h), 139 ± 5, and specific H₂ production (ml/g/h), 694 ± 10 were obtained. Clostridium sp. IODB-O3 exhibited better H₂ yield from cheese whey than the reported values in literature. Importantly, the enhancement of biohydrogen yield was observed possibly due to absence of inhibitory compounds, presence of essential nutrients, protein and lactic acid fractions which supported better cell growth than that of the lactose and glucose media. Carbon balance was carried out for the process which provided more insights in IODB-O3 metabolic pathway for biohydrogen production. This study may help for effective utilization of whey wastes for economic large scale biohydrogen production.     

The effect of the concentration of hydrochloric acid and acetic acid aqueous solution for fast hydrogen production from methanol solution of NaBH4

The semi-methanolysis reactions with hydrochloric acid and acetic acid were used for the hydrogen production from sodium borohydride (NaBH₄). The effects of the NaBH₄ concentration, hydrochloric acid and, acetic acid concentration, and temperature on the reactions were investigated. The maximum hydrogen production rates in the semi-methanolysis with 1 M hydrochloric acid and acetic acid were 4875 and 3960 ml min^?1, respectively. At the same time, the semi-methanolysis reactions with the acids are completed within 4 and 5 s, respectively. The power law kinetic model is performed for kinetic studies. Activation energies for the semi-methanolysis reactions of NaBH₄ in the presence of hydrochloric acid and acetic acid were found as 5.84 and 2.81 kJ mol^?1, respectively.     

Enhanced bio-hydrogenesis by co-culturing photosynthetic bacteria with acidogenic process: Augmented dark-photo fermentative hybrid system to regulate volatile fatty acid inhibition

To overcome induced fatty acid inhibition during dark-fermentative hydrogen (H₂) production process, a hybrid strategy was designed and evaluated by co-culturing photosynthetic bacteria with acidogenic microflora. Augmented dark-photo fermentation system (ADPFS) illustrated 40% increment in cumulative H₂ production (CHP, 250 ml) compared to dark-fermentation system (DFS) along with 10% enhancement in COD removal efficiency. Co-culturing helped to reduce VFA accumulation by 40% which supports the functional role of photosynthetic organisms in reducing the fatty acid concentration in association to additional H₂ production. Relatively higher reduction in individual fatty acids viz., acetic acid (43%), butyric acid (57%) and propionic acid (65%) was observed with AD-PFS operation. Increment in bacteriochlorophyll (Bchl) after augmentation corroborated well with results. At lower pH, pheophytinization was observed which hindered H₂ production. Voltammograms illustrated dominant oxidation behavior during hybrid AD-PFS operation and provides viable option for enhancing performance by regulating system buffering microenvironment.