New methods of heterogeneous catalysis for lignocellulosic biomass conversion to chemicals

This review deals with the use of solid catalysts for the enhancement of the efficiency and the development of a new generation of environmentally friendly, energy and resource efficient processes for the deep processing of lignocellulosic biomass to desired chemicals. The oxidative delignification of wood with hydrogen peroxide in the presence of the suspended TiO₂ catalyst, the oxidation of wood with molecular oxygen in the presence of copper catalysts, the acidcatalyzed conversion of cellulose to glucose and levulinic acid, and the thermal conversion of lignin to fuel additives on solid acid catalysts are analyzed. New integrated processes based on the heterogeneous catalytic oxidation are suitable for the complex processing of lignocellulosic biomass to produce valuable chemicals and engine fuel components without the use of toxic and corrosion-active reagents.     

Thermal characterization of lignocellulosic residue from different sugarcanes

Bagasse samples from four different sugarcane were directly collected as the residues of milling in a processing plant. The samples were dried at 105 °C, compressed to small granules and then their TG/DTA and DSC curves in synthetic air were recorded. Similar thermogravimetric curves were obtained for the different samples and they exhibited four mass loss steps. However, the analysis of the exotherm DSC peaks showed that the oxidation of the organic matter resulted different enthalpy values (ΔH/kJ g⁻¹).     

Co-pyrolysis of macroalgae and lignocellulosic biomass

Synergistic effect of co-pyrolysis of macroalgae [Enteromorpha prolifera (EP)] and lignocellulosic biomass [rice husk (RH)] in a fixed bed reactor for maximum and enhanced biofuels yield has been investigated. The main and interaction effects of three effective co-pyrolysis parameters (pyrolysis temperature, feedstock blending ratio, and heating rate) were also modeled and simulated to determine the yield rates of bio-oil and bio-char, respectively. Optimization studies were, then, performed to predict the optimal conditions for maximum yields using the central composite circumscribed experimental design in Design Expert^® software 8.0.6. Analysis of variance was carried out to determine whether the fit of the multiple regressions is significant for the second-order model. Normal pyrolysis oils from EP, RH, and co-pyrolysis oils obtained from different feedstock blending ratios were examined using the gas chromatography-mass spectrometry to identify their compositions. Some vital properties of oils and bio-chars such as the heating value, water content, elemental compositions, and specific gravity were also determined, which unveiled that synergistic effect exists between EP and RH during co-pyrolysis, and this led to increase in products’ yields and improved co-pyrolysis products’ quality.

     

Analytical determination of organic acids formed during hydrothermal and organosolv degradation of lignocellulosic biomass

Summary The present study deals with the isotachophoretic and the ion chromatographic analysis of organic acids found in hydrolysates of lignocellulosic biomass. The samples were pretreated by means of ultrafiltration to increase the reproducibility of the measurements. The qualitative and quantitative analysis of the fractions obtained during hydrothermal and organosolv degradations of wheat straw allowed a comparison of the rate and amount of organic acids formed (formic acid, glycolic acid, lactic acid, acetic acid). Isotachophoresis facilitates research on the reaction mechanisms underlying the hydrolysis of biomass.

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Analyse der durch Hydrothermolyse und Organosolv-Aufschluß von lignocellulosehaltiger Biomasse gebildeten organischen Säuren

     

Anaerobic digestion of lignocellulosic biomass and wastes

Anaerobic digestion represents one of several commercially viable processes to convert woody biomass, agricultural wastes, and municipal solid wastes to methane gas, a useful energy source. This process occurs in the absence of oxygen, and is substantially less energy intensive than aerobic biological processes designed for disposal purposes. The anaerobic conversion process is a result of the synergistic effects of various microorganisms, which serve as a consortium. The rate-limiting step of this conversion process has been identified as the hydrolysis of cellulose, the major polymeric component of most biomass and waste feedstocks. Improvements in process economics therefore rely on improving the kinetic and physicochemical characteristics of cellulose degrading enzymes. The most thoroughly studied cellulase enzymes are produced by aerobic fungi, namely Trichoderma reesei. However, the pH and temperature optima of fungal cellulases make them incompatible for use in anaerobic digestion systems, and the major populations of microorganisms involved in cellulase enzyme production under anaerobic digestion conditions are various bacterial producers. The current state of understanding of the major groups of bacterial cellulase producers is reviewed in this paper. Also addressed in this review are recently developed methods for the assessment of actual cellulase activity levels, reflective of the digester "hydrolytic potential," using a series of detergent extractive procedures.     

Enzymatic saccharification of industrial and agricultural lignocellulosic wastes

Applied Biochemistry and Biotechnology - Cellolignin, an industrial residue obtained during the production of furfural from wood and corn cobs, when pretreated by diluted H2SO4 at elevated...     

Enhanced deconstruction and dissolution of lignocellulosic biomass in ionic liquid at high water content by lithium chloride

Fabricating an aqueous ionic liquid (IL) for deconstruction and dissolution of lignocellulose is attractive because addition of water could reduce the cost and viscosity of the solvent and improve the biomass processing, but the solvating power of the IL is usually depressed in the presence of water. In the present study, an aqueous IL consisting of 1-butyl-3-methylimidazolium chloride (BmimCl), water, and lithium chloride was fabricated for efficient deconstruction and dissolution of lignocellulose (bamboo). The dissolution of cell wall components (cellulose, lignin, and hemicelluloses) in the aqueous IL was investigated. The results indicated that the presence of water significantly reduced the solvating power of BmimCl; For example, 11.5 % water decreased the dissolution of bamboo in BmimCl from ~97 to ~53 %. Dissolution of cellulose and lignin was specifically depressed. However, addition of lithium chloride was able to improve the tolerance of BmimCl to water and enhance the deconstruction and dissolution of biomass in BmimCl with high water content. It was found that approximately 80 % bamboo could be dissolved in solvent consisting of 45 wt% BmimCl and 55 wt% LiCl·2H₂O (25 wt% overall water content in the solvent). In particular, lignin and hemicelluloses were selectively dissolved by 96 and 92 %, respectively. The undissolved residue was predominantly composed of cellulose (~86 %) with a small amount of lignin (<5 %). BmimCl-LiCl-H₂O is a promising and effective solvent system with low cost and viscosity for biomass processing.     

Alkaline and peracetic acid pretreatments of biomass for ethanol production

Prehydrolysis with dilute acid and steam explosion constitute the most promising methods for improving enzymatic digestibility of biomass for ethanol production. Despite world wide acceptance, these methods of pretreatment are quite expensive considering costs for the reactor, energy, and fractionation. Using peracetic acid is a lignin-oxidation pretreatment with low-energy input by which biomass can be treated in a silo-type system without need for expensive capitalization. Experimentally, ground hybrid poplar and sugar cane bagasse are placed in plastic bags and a peracetic acid solution is added to the biomass in different concentrations based on ovendried biomass. The ratio of solution to biomass is 6∶1 and a 7-d storage period at ambient temperature (20°C) has been used. As an auxiliary method, a series of pre-pretreatments using stoichiometri camounts of sodium hydroxide and ammonium hydroxide based on 4-methyl-glucuronic acid and acetyl content in the biomass are performed before addition of peracetic acid. The basic solutions are added to the biomass in a ratio of 14∶1 solution to biomass, and mixed for 24 h at the same ambient temperature. Biomass is filtered and washed to a neutral pH before peracetic acid addition. The aforementioned procedures give high xylan content substrates as a function of the selectivity of peracetic acid for lignin oxidation and the mild conditions of the process. Consequently, xylanase/β-glucosidase combinations were more effective than cellulase preparations in hydrolyzing these materials. The pretreatment efficiency was evaluated through enzymatic hydrolysis and simultaneous saccharification and cofermentation (SSCF) tests. Peracetic ac treatment improves enzymatic digestibility of hybrid poplar and sugar cane bagasse with no need of high temperatures. Alkaline treatments are helpful in reducing peracetic acid requirements in the pretreatment.     

Role of pretreatment and conditioning processes on toxicity of lignocellulosic biomass hydrolysates

The Department of Energy’s Office of the Biomass Program has set goals of making ethanol cost competitive by 2012 and replacing 30% of 2004 transportation supply with biofuels by 2030. Both goals require improvements in conversions of cellulosic biomass to sugars as well as improvements in fermentation rates and yields. Current best pretreatment processes are reasonably efficient at making the cellulose/hemicellulose/lignin matrix amenable to enzymatic hydrolysis and fermentation, but they release a number of toxic compounds into the hydrolysate which inhibit the growth and ethanol productivity of fermentation organisms. Conditioning methods designed to reduce the toxicity of hydrolysates are effective, but add to process costs and tend to reduce sugar yields, thus adding significantly to the final cost of production. Reducing the cost of cellulosic ethanol production will likely require enhanced understanding of the source and mode of action of hydrolysate toxic compounds, the means by which some organisms resist the actions of these compounds, and the methodology and mechanisms for conditioning hydrolysate to reduce toxicity. This review will provide an update on the state of knowledge in these areas and can provide insights useful for the crafting of hypotheses for improvements in pretreatment, conditioning, and fermentation organisms.     

Catalytic conversion of lignocellulosic biomass to fine chemicals and fuels

Lignocellulosic biomass is the most abundant and bio-renewable resource with great potential for sustainable production of chemicals and fuels. This critical review provides insights into the state-of the-art accomplishments in the chemocatalytic technologies to generate fuels and value-added chemicals from lignocellulosic biomass, with an emphasis on its major component, cellulose. Catalytic hydrolysis, solvolysis, liquefaction, pyrolysis, gasification, hydrogenolysis and hydrogenation are the major processes presently studied. Regarding catalytic hydrolysis, the acid catalysts cover inorganic or organic acids and various solid acids such as sulfonated carbon, zeolites, heteropolyacids and oxides. Liquefaction and fast pyrolysis of cellulose are primarily conducted over catalysts with proper acidity/basicity. Gasification is typically conducted over supported noble metal catalysts. Reaction conditions, solvents and catalysts are the prime factors that affect the yield and composition of the target products. Most of processes yield a complex mixture, leading to problematic upgrading and separation. An emerging technique is to integrate hydrolysis, liquefaction or pyrolysis with hydrogenation over multifunctional solid catalysts to convert lignocellulosic biomass to value-added fine chemicals and bio-hydrocarbon fuels. And the promising catalysts might be supported transition metal catalysts and zeolite-related materials. There still exist technological barriers that need to be overcome (229 references).     

Preparation and characterization of pyrolytic chars from different biomass samples

In the present work four different biomass samples (pine cone, soybean cake, corn stalk and peanut shell) were pyrolyzed to 550 °C in an inert gas atmosphere and a comparison between the properties of chars produced has been performed. Characterization of biomass samples was carried out with FT-IR, ¹³C NMR, SEM and EDX. The influence of the parent material on char quality was investigated. The chars were characterized by their proximate and ultimate analysis and surface areas by N₂ adsorption at 77 K using BET equation. The morphological changes in carbonaceous solids were observed by scanning electron microscopy (SEM), and FT-IR spectra were obtained to evaluate the functional groups. The results obtained from the different techniques were combined to give an overview of the chemical and physical properties of the biomass char samples.     

The effect of different variables on the accelerated and natural weathering of agricultural films

Lifetimes required for greenhouse cover films depend heavily on the country, especially the tradition in the country. They vary from one agricultural season (i.e. 6-9 months) to several years and are strongly dependent on the use of pesticides which destroy the photostabilisers (HALS and nickel quenchers) and on other geographic and climatic factors (solar irradiation, temperature, winds, etc.).In this work, we have measured the duration of four real agricultural films using the European Standard EN 13206:2001 conditions for the accelerated weathering test and the results have been compared to their duration under accelerated weathering using more aggressive conditions (pesticide spraying, different chamber temperatures) and under natural weathering. We have also explored the effect of the backing material in the artificial weathering test and of the starting date in the natural weathering. The final goal of this study is to obtain good correlations between accelerated weathering, natural weathering at defined, controlled conditions and weathering in real-use conditions for agricultural films.     

Chemical characterization of agricultural supplies applied to organic tomato cultivation

The agricultural supplies used in the organic system to control pests and diseases as well as to fertilize soil are claimed to be beneficial to plants and innocuous to human health and to the environment. The chemical composition of six agricultural supplies commonly used in the organic tomato culture, was evaluated by instrumental neutron activation analysis (INAA). Results were compared to the maximum limits established by the Environment Control Agency of the São Paulo State (CETESB) and the Guidelines for Organic Quality Standard of Instituto Biodinâmico (IBD). Concentrations above reference values were found for Co, Cr and Zn in compost, Cr and Zn in cattle manure and Zn in rice bran.     

Physico-chemical and anatomical characterization of residual lignocellulosic fibers

Anatomical and physico-chemical properties of residual natural fibers (sugarcane bagasse, coconut fibers and peanut hulls) were characterized in order to evaluate their potential for use in the production of particleboard. The bulk density was determined by helium pycnometer and the chemical characteristics by using an electronic pH meter (for pH determination) on fibers dissolved in acidic and neutral detergents (to determine the levels of cellulose, hemicellulose and lignin). The anatomical characteristics were established using scanning electron microscopy coupled with an X-ray detector system, as well as energy dispersive X-ray spectroscopy. Results indicated similarities and differences between physico-chemical and anatomical characteristics of the residual lignocellulosic fibers when compared with the Pinus sp. wood commercially employed in particleboard production. Bulk density and pH for residual lignocellulosic fibers and Pinus sp. wood presented analogous values. Similar amounts of cellulose and lignin were identified between waste fibers and Pinus sp. wood. The presence of silica was identified in coconut fiber, peanut hull and sugarcane bagasse waste fibers, and may affect the mechanical characteristics of panels. Coconut and sugarcane bagasse fibers show surface pores with diameters ranging from 1.2 to 2.1 μm, below the 5 μm identified for Pinus sp. wood. Both fibers present pores distributed over their entire surface, whereas peanut hull fibers have no pores on their surface. This characteristic contributes to resin dispersion among particles, reflecting positively on the physical–mechanical properties of the panels. Particleboards produced with residual lignocellulosic fibers present similar physical–mechanical properties to those of Pinus sp. wood panels.     

Electrochemical and spectroscopic characterization of organic compound uptake in silica core-shell nanocapsules

Oil-filled silica nanocapsules consisting of a hydrophobic liquid core and a silicate shell have been shown to efficiently extract hydrophobic compounds from aqueous media. With a view toward quantifying the selectivity of these systems, a series of electrochemical and spectroscopic measurements was performed. Uptake and kinetics experiments were carried out through electrochemical measurements by using solutions of lipophilic electroactive molecules of different sizes and with different affinities for silica. Other solutions with fluorescent probes were used for spectrophotometry measurements. In this work we report the environment where the lipophilic compounds studied end up after absorption and the kinetics of their uptake by the oil-filled silica nanocapsules with different shell thicknesses.     

The characterisation and determination of nitrogenous organic bases in mixtures with ammonium reineckate

The reaction between nitrogenous organic bases and ammonium reineckate was studied and was found to depend on the basicity of the bases and the pH of the reaction media. An expression is given which relates the dissociation constant pK_b of a base and the pH of the reaction ; when the pK_b of a base is known the pH required for the complex formation can be calculated. The conditions for the formation of reineckates of very weak bases together with the formation of mono and di-reineckates of dibasic substances are given. The separation of bases whose pK_b values are sufficiently far apart and the determination of mixtures of mono- and dibasic substances were effected by pH adjustment of the reaction media. The isolation of strychnine from putrified human livers is also described.     

Liquid chromatography-mass spectrometry-based quantification of steroidal glycoalkaloids from Solanum xanthocarpum and effect of different extraction methods on their content

A new liquid chromatography-mass spectrometry (LC-MS)-based method coupled with pressurized liquid extraction (PLE) as an efficient sample preparation technique has been developed for the quantification and fingerprint analysis of Solanum xanthocarpum. Optimum separations of the samples were achieved on a Waters MSC-18 XTerra column, using 0.5% (v/v) formic acid in water (A) and acetonitrile (ACN):2-propanol:formic acid (94.5:5:0.5, v/v/v) (B) as mobile phase. The separation was carried out using linear gradient elution with a flow rate of 1.0mL/min. The gradient was: 0min, 20% B; 14min, 30% B; 20min, 30% B; 27min, 60% B and the column was re-equilibrated to the initial condition (20% B) for 10min prior to next injection. The steroidal glycoalkaloids (SGAs) which are the major active constituents were isolated as pure compounds from the crude methanolic extract of S. xanthocarpum by preparative LC-MS and after characterization were used as external standards for the development and validation of the method. Extracts prepared by conventional Soxhlet extraction, PLE and ultrasonication were used for analysis. The method was validated for repeatability, precision (intra- and inter-day variation), accuracy (recovery) and sensitivity (limit of detection and limit of quantitation). The purpose of the work was to develop a validated method, which can be used for the quantification of SGAs in commercialized S. xanthocarpum products and the fingerprint analysis for their routine quality control.     

Effect of moisture content on the interaction between lignocellulosic materials and ozone

The kinetics of ozonolysis for a number of plant materials (aspen and pine sawdust, wheat straw, flax chaff, and sunflower husks) is comparatively studied, and the dependences of the rate of ozone absorption on the water content in lignocellulosic samples are obtained. The kinetic curves of water absorption by different plant materials in a saturated water vapor atmosphere at room temperature are constructed, and the equilibrium values of water content are determined. It is shown that straw is characterized by a higher affinity for water than wood. The range of the moisture contents of lignocellulosic materials that ensures the maximum rate of their reaction with ozone is found. No appreciable effect of the nature of plant material on the rate of ozone absorption was detected, since the process is controlled by the diffusion of ozone in the pores of materials.