Electrochemical hydrogen production from biomass

Thermodynamic data indicate that the oxidation of oxygenated organic species originating from biomass instead of water at the anode of an electrolysis cell should allow decreasing the cell voltage below 1.23 V. Biosourced alcohols, polyols, sugars, lignocellulosic compounds, and their derivatives are then electroreformed to produce clean hydrogen at the cathode and compounds at the anode of electrolysis cells. The reported studies highlight the main challenges to make electroreforming a future industrial process: higher reaction kinetics and hydrogen evolution rate; better selectivity of anode catalysts toward the formation of CO₂ or added-value compounds; and utilization of nonstrategical metals. An attractive solution to decrease hydrogen production costs and to make bankable other economic activities consists in directly valuing wastes from agriculture/forestry (lignocellulosic raw materials) and/or wastes from biofuel industries.     

A photocatalyst-enzyme coupled artificial photosynthesis system for solar energy in production of formic acid from CO2

The photocatalyst-enzyme coupled system for artificial photosynthesis process is one of the most promising methods of solar energy conversion for the synthesis of organic chemicals or fuel. Here we report the synthesis of a novel graphene-based visible light active photocatalyst which covalently bonded the chromophore, such as multianthraquinone substituted porphyrin with the chemically converted graphene as a photocatalyst of the artificial photosynthesis system for an efficient photosynthetic production of formic acid from CO(2). The results not only show a benchmark example of the graphene-based material used as a photocatalyst in general artificial photosynthesis but also the benchmark example of the selective production system of solar chemicals/solar fuel directly from CO(2).     

Periodic and chaotic behavior of substrate-inhibited enzymatic reactions with hydrogen ions production

A two-compartment model of an enzyme system with substrate inhibition kinetics and hydrogen ion production is investigated. The model is used to study the bifurcation, instability, and chaotic behavior of the system. The investigation, although in a restricted region of the parameters’ space, has uncovered a good part of the rich dynamic characteristics of this system, including: period doubling sequences leading to chaos, banded chaos, fully developed chaos, interior crisis, tangent bifurcation leading to intermittency, periodic windows interrupting chaotic regions, and alternating periodic chaotic sequences. The results relate to the phenomena occurring in physiological experiments, such as the periodic stimulation of neural cells and the voltagegated ion channel dynamics.     

Ethanol production in immobilized-cell bioreactors from mixed sugar syrups and enzymatic hydrolysates of steam-exploded biomass

We investigated ethanol production from mixed sugar syrups. Hydrolysates were prepared from enzymatic saccharification of steam-pretreated aspen chips. Syrups containing 45 g/L of glucose and 12 g/L of xylose were detoxified through two ion-exchange resins and then fermented with Pichia stipitis and Saccharomyces cerevisiae immobilized in Ca-alginate gel beads. Combinations of different gel fractions in the fermentation volume, amount of yeast cells, and ratios of P. stipitis vs S. cerevisiae within each bead were compared. In the best conditions, by using a total beads volume corresponding to 25% of the working volume, we obtained a yield of 0.39 g_ethanol/g_{initial sugars}. This amount of gel entrapped an initial cell concentration of 6×10¹²cells/L with ratio of S. cerevisiae/P. stipitis of 0.25 g/g. Modified stirredtank reactors were obtained either by adding marbles or by inserting a perforated metal cylinder, which reduced considerably the rupture of beads while visibly improving oxygenation of the medium.     

Interfacial properties of cellulose nanoparticles obtained from acid and enzymatic hydrolysis of cellulose

Rod-shaped cellulose nanocrystals obtained by acid hydrolysis of eucalyptus fibers (CNCa) presented high aspect ratio (estimated length and width of 180 and 5 nm, respectively) and zeta potential of ?(17 ± 1) mV at pH 6. This typical morphology of cellulose nanocrystals was in contrast to nanoparticles obtained upon enzymatic hydrolysis of bacterial cellulose (CNCe), which were asymmetric and irregular due to surface-bound cellulases and presented a distinctive surface roughness. Interestingly, CNCe also displayed axial grooves, to yield a C-shape cross section that has not been reported before. The effect of the characteristic shape and surface chemistry of CNCa and of grooved CNCe was studied at oil/water interfaces and solid surfaces. Emulsions (20 % v/v oil) prepared with the CNCa were more stable than those prepared with CNCe, owing to their characteristic shape and surface chemistry. Hydrophilic (silica surfaces cationized by pre-adsorbed polycation) and hydrophobic (polystyrene films) solid surfaces were used as substrates for the adsorption of CNCe and CNCa for each type of surface. The ellipsometric data and AFM images indicated larger affinity of CNCe than CNCa for the hydrophobic surface. On the other hand, CNCa formed homogeneous monolayer on hydrophilic surfaces, whereas CNCe formed discontinuous films. Sequential adsorption behavior of CNCa on CNCe layers (or vice versa) suggested that the interaction between them is controlled by the orientation of enzymes bound to CNCe.     

Bioethanol from cellulose with supercritical water treatment followed by enzymatic hydrolysis

The water-soluble portion and precipitates obtained by supercritical (SC) water treatment of microcrystalline cellulose (Avicel) were enzymatically hydrolyzed. Glucose could be produced easily from both substrates, compared with the Avicel. Therefore, SC water treatment was found to be effective for enhancing the productivity of glucose from cellulose by the enzymatic hydrolysis. It is also found that alkaline treatment or wood charcoal treatment reduced inhibitory effects by various decomposed compounds of cellulose on the enzymatic hydrolysis to achieve higher glucose yields. Furthermore, glucose obtained by SC water treatment followed by the enzymatic hydrolysis of cellulose could be converted to ethanol by fermentation without any inhibition.     

Microfibrillated cellulose and cellulose nanopaper from Miscanthus biogas production residue

The feasibility of the isolation of microfibrillated cellulose (MFC) from the fibrous residue of the production of biogas from Miscanthus straw was investigated. Studying two variants of continuous anaerobic fermentation carried out at mesophilic and thermophilic conditions, respectively, MFC was obtained after extensive extraction of non-cellulosic compounds and mechanical fibrillation. MFC crystallinity and molar mass were drastically decreased in biogas residue with increasing temperature in processing. Nonetheless, nanopaper produced from all variants showed acceptable mechanical performance considering its significantly degraded structure. High failure strain at low density is of particular interest for the thermophilic variant. Infrared spectroscopy indicates changes in surface chemistry of the thermophilic variant, which may explain its peculiar tensile properties. Production of fibrillated cellulose from biogas residue is suggested as highly interesting route for the generation of additional value from bioenergy processes.     

Solar hydrogen production with semiconductor metal oxides: new directions in experiment and theory

An overview of a collaborative experimental and theoretical effort toward efficient hydrogen production via photoelectrochemical splitting of water into di-hydrogen and di-oxygen is presented here. We present state-of-the-art experimental studies using hematite and TiO(2) functionalized with gold nanoparticles as photoanode materials, and theoretical studies on electro and photo-catalysis of water on a range of metal oxide semiconductor materials, including recently developed implementation of self-interaction corrected energy functionals.     

Grafting with acrylonitrile with the redox system cellulose xanthogenate–hydrogen peroxide

The possibility of obtaining modified cellulose products by reacting cellulose xanthogenate in solutions containing oxidizers and acrylonitrile was studied. The ability of the cellulose xanthogenate–hydrogen peroxide redox system to initiate graft copolymerization of acrylonitrile on the cellulose was demonstrated. The influence of various factors on the processes was investigated. An attempt was made to clarify the nature of the reactions involved.     

Activity of Ni catalysts for hydrogen production via biomass pyrolysis

Ni catalysts were tested in the catalytic pyrolysis of biomass. The influence of Ni loading and various catalytic supports (ZrO₂, Al₂O₃, ZrO₂ + Al₂O₃, CeO₂, SiO₂) was studied. Although the gas phase was the main object of this study, solid and liquid residues were tested as well (mainly by TOC and GC-MS methods). Activity tests were performed in a batch reactor with mechanical stirring, equipped with on-line GC. Reaction was conducted at 700°C, with ??-cellulose as a biomass model and with waste paper as an example of raw lignocellulosic material. Reactions in the presence of a catalyst gave a higher hydrogen yield. The most promising results were obtained with Ni/ZrO₂.     

Influence of ionic-liquid incubation temperature on changes in cellulose structure,biomass composition,and enzymatic digestibility

Varying ionic liquid, 1-ethyl 3-methyl imidazolium acetate, pretreatment incubation temperature on lignocellulosic biomass substrates, corn stover, switchgrass and poplar, can have dramatic effects on the enzymatic digestibility of the resultant regenerated biomass. In order to delineate the chemical and physical changes resulting from the pretreatment process and correlate changes with enzymatic digestibility, X-ray powder and fiber diffraction, ¹³C cross polarization/magic angle spinning nuclear magnetic resonance spectroscopy, and compositional analysis was completed on poplar, corn stover and switchgrass samples. Optimal pretreatment incubation temperatures were most closely associated with the retention of amorphous substrates upon drying of regenerated biomass. Maximal glucan to glucose conversion for 24 h enzyme hydrolysis was observed for corn stover, switchgrass and poplar at ionic liquid incubation temperatures of 100, 110 and 120 °C, respectively. We hypothesize that effective pretreatment temperatures must attain lignin redistribution and retention of xylan for optimal enzyme digestibility.     

丹麦生物质发电的现状和研究发展趋势

丹麦是世界上利用秸秆生物质燃烧发电技术开发、运行最好的国家，其经验值得中国借鉴。根据作者在丹麦对生物质燃烧发电的研究经历，系统地介绍了丹麦在秸秆生物质发电的经验、遇到的问题及相应的研究和今后的发展方向。     

水参与制氢的Cu-P体系研究

研究了水参与的Cu-P氧化还原体系制氢过程。考察了Cu/P物质的量比、反应温度、酸度、外加Cu单质等对氢气产率的影响,设计了Cu的循环利用和P的转化利用过程,实现了Cu-P体系的绿色化过程。结果表明,通过调控Cu/P物质的量比和反应温度等因素可以控制反应过程中生成的氢原子转化为氢气的量,在以0.20 g五水硫酸铜为基准物的Cu2+/H2PO-2物质的量比为0.05和95℃反应条件下可获得大于反应计量比的18.6 mL氢气;酸性条件下H2O2氧化单质Cu可以实现Cu的10次循环利用;制氢过程生成的亚磷酸氢根可以用Ca(OH)2处理转化为新型防锈剂CaHPO3·H2O,该防锈剂用红外光谱(FT-IR)和X射线衍射(XRD)得到了表征。     

Biotechnological production of acrylic acid from biomass

Applied Biochemistry and Biotechnology - The quantitative conversion of lactic acid to acrylic acid would open a new market for renewable resources within the chemical industry. This paper focuses...     

Photocatalytic hydrogen production from acidic aqueous solution in BODIPY-cobaloxime-ascorbic acid homogeneous system

For the first time, iodinated BODIPY dyes with phenylamine or 8-hydroxylquinoline moiety at the meso-position on the BODIPY core were tested for the light-driven production of H₂ from the acidic aqueous solutions.     

Nanoscale photosynthesis: photocatalytic production of hydrogen by platinized photosystem I reaction centers.

A study of the photocatalytic production of molecular hydrogen from platinized photosystem I (PSI) reaction centers is reported. At pH 7 and room temperature metallic platinum was photoprecipitated at the reducing end of PSI according to the reaction, [PtCl6]2- + 4e- + hv-->Pt decreases + 6Cl-, where it interacted with photogenerated PSI electrons and catalyzed the evolution of molecular hydrogen. The reaction mixture included purified spinach PSI reaction centers, sodium ascorbate and spinach plastocyanin. Experimental data on real-time catalytic platinum formation as measured by the onset and rates of hydrogen photoevolution as a function of time are presented. The key objective of the experiments was demonstration of functional nanoscale surface metalization at the reducing end of isolated PSI by substituting negatively charged [PtCl6]2- for negatively charged ferredoxin, the naturally occurring water-soluble electron carrier in photosynthesis. The data are interpreted in terms of electrostatic interactions between [PtCl6]2- and the positively charged surface of psaD, the ferredoxin docking site situated at the stromal interface of the photosynthetic membrane and which is presumably retained in our PSI preparation. A discussion of the rates of hydrogen evolution in terms of the structural components of the various PSI preparations as well as of those of the intact thylakoid membranes is presented.     

Biohydrogenation from biomass sugar mediated by in vitro synthetic enzymatic pathways

Different from NAD(P)H regeneration approaches mediated by a single enzyme or a whole-cell microorganism, we demonstrate high-yield generation of NAD(P)H from a renewable biomass sugar--cellobiose through in vitro synthetic enzymatic pathways consisting of 12 purified enzymes and coenzymes. When the NAD(P)H generation system was coupled with its consumption reaction mediated by xylose reductase, the NADPH yield was as high as 11.4 mol NADPH per cellobiose (i.e., 95% of theoretical yield--12 NADPH per glucose unit) in a batch reaction. Consolidation of endothermic reactions and exothermic reactions in one pot results in a very high energy-retaining efficiency of 99.6% from xylose and cellobiose to xylitol. The combination of this high-yield and projected low-cost biohydrogenation and aqueous phase reforming may be important for the production of sulfur-free liquid jet fuel in the future.     

Effects of hemicellulose and lignin on enzymatic hydrolysis of cellulose from dairy manure

This study focused on the effect of hemicellulose and lignin on enzymatic hydrolysis of dairy manure and hydrolysis process optimization to improve sugar yield. It was found that hemicellulose and lignin in dairy manure, similar to their role in other lignocellulosic material, were major resistive factors to enzymatic hydrolysis and that the removal of either of them, or for best performance, both of them, improved the enzymatic hydrolysis of manure cellulose. This result combined with scanning electron microscope (SEM) pictures further proved that the accessibility of cellulose to cellulase was the most important feature to the hydrolysis. Quantitatively, fed-batch enzymatic hydrolysis of fiber without lignin and hemicellulose had a high glucose yield of 52% with respect to the glucose concentration of 17 g/L at a total enzyme loading of 1300 FPU/L and reaction time of 160 h, which was better than corresponding batch enzymatic hydrolysis.