In this work, Leucaena leucocephala K366 was characterized chemical and energy terms, and assessed its potential as a lignocellulosic raw material and energetic and industrial crop specie, and its integral fractionation by autohydrolysis by evaluating its calorific value, holocellulose, glucan, xylan, araban, lignin and oligomers and monomers contents in autohydrolysis liquor and solid phase. Also, this paper will consider the influence of the temperature and time of autohydrolysis process from Leucaena leucocephala K366 to obtain a valuable liquor and a suitable solid phase to produce energy by combustion. A valuable liquor was obtained from the autohydrolysis of Leucaena leucocephala K366 by simultaneously using operating temperatures and times in the medium-high ranges studied, namely: 172--30 min. The optimum processing conditions provided an acceptable yield (16-26%), and high xylose and xylo-oligomer contents in the liquor (10.0 and 58.6%, respectively, of the amounts present in the starting raw mate fraction was extracted virtually completely ─only 8.3% remained in the solid fraction─, and the acetyl group fraction was recovered in full. In addition, these conditions reduced the glucose content of the liquor to 2.9% of the amount present in the raw material while largely preserving the integrity of cellulose fibers.Klason lignin was scarcely dissolved under the operating conditions of the auto¬hydrolysis process. This increased the calorific value of the solid phase by 9% (under the most drastic operating conditions) with respect to the starting raw material. AbstractIn this work, Leucaena leucocephala K366 was characterized chemical and energy terms, and assessed its potential as a lignocellulosic raw material and energetic and industrial crop specie, and its integral fractionation by autohydrolysis by evaluating its calorific value, holocellulose, glucan, xylan, araban, lignin and oligomers and monomers contents in autohydrolysis liquor and solid phase. Also, this paper will consider the influence of the temperature and time of autohydrolysis process fromLeucaena leucocephala K366 to obtain a valuable liquor and a suitable solid phase to produce energy by combustion.A valuable liquor was obtained from the autohydrolysis of Leucaena leucocephala K366 by simultaneously using operating temperatures and times in the medium-high ranges studied, namely:172-184 C and 15-30 min. The optimum processing conditions provided an acceptable yield (16-26%), and high xylose and xylo-oligomer contents in the liquor (10.0 and 58.6%, respectively, of the amounts present in the starting raw material when operating at 184 C for 30 min). The araban fraction was extracted virtually completely ─only 8.3% remained in the solid fraction─, and the acetyl group fraction was recovered in full. In addition, these conditions reduced the glucose content of the liquor to 2.9% of the amount present in the raw material while largely preserving the integrity of cellulose fibers.Klason lignin was scarcely dissolved under the o...

A method for the selective extraction of hemicellulose from wheat straw involving cold alkaline extraction and subsequent separation by precipitation with ethanol is proposed. Wheat straw affords selective separation of the hemicellulose fraction from the cellulose and lignin fractions with the proposed method. The hemicellulose yield was optimized by using a 2n factor design to examine the influence of temperatures (temperature was designed between 20 and 40 ◦C), operation times (operation time was designed between 30 and 60 min) and alkali concentrations (alkali concentration was designed between 80 and 120 g L−1). These conditions allowed 56.1% of all hemicellulose initially present in the raw material, and 59.1% of the lignin, to be extracted. Subsequent separation of hemicellulose in the liquid phase from the cold alkaline extraction by precipitation with ethanol provided a fraction containing 39.4% of all hemicellulose (45.2% hemicellulose in extract/total extract) and only 12% of all lignin in the raw material.The authors are grateful for the FPU grant from the Spanish Ministry of Education. Also they thank to Spanish Ministry of Economy and Competitiveness (former Ministry of Science and Innovation) contracts. The authors acknowledge financial support for this investigation has been provided by CDTI (CENIT-E-CDTI-BioSos-CEN-2009-1040) and supported by Ministry of Economy and Competitiveness, "Local Investment fund for employment". Government of Spain, Junta de Andalucia, CICYT-FEDER (Science and Technology Inter Ministerial Commission, Spanish Government - European Regional Development Fund), project number AGL2009-13113 and the business group ACCIONA INFRAESTRUCTURAS, S.A

The aim of this study was to optimize the production of furfural by hydrolysis with dilute acid of Eucalyptus globulus wood in two stages, using a factorial experimental design and multiple regression models to maximize furfural yields. The two-stage process could provide a solid phase with less degraded cellulose and older applications that the solid phase of a conventional acid hydrolysis. The selectivity for furfural of the process was increased by effect of the glucan and lignin fractions being efficiently removed after the first acid hydrolysis stage.The operational ranges are especially suitable for the extraction of xylose, which was virtually quantitative at 170 ºC and virtually independent of the operation time. It is therefore advisable to use non-isothermal conditions or short times. This is quite important if one considers the low acid concentration used. The liquid phase obtained after autohydrolysis of the raw material under the optimum conditions contained 2.3% glucose, 9.8% xylose, 2.5% xylo-oligomers, 0.6% arabinose, 1.1% furfural and 0.1% 5-OH methyl furfural.After the residual solid from the first hydrolysis stage is removed, the acid concentration is the most influential variable on the conversion of xylo-oligomers or xylose into furfural. Conversions to furfural were quite substantial (greater than 10 g/L). Hemicelluloses in the raw material were extracted by 32-57.7% and xylan by 40.5-84%. The highest conversions to furfural were obtained by using a medium operation time (15 min) and low temperature (170 ºC) and pH=2.The process additionally provides hemicellulose derivatives that are scarcely contaminated with cellulose derivatives. The concentrations of gluco-oligomers were very low and those of glucose in the region of 3% of the raw material.Response to Reviewers: Optimization of furfural production by acid hydrolysis of Eucalyptus globulus in two stages. Ms. Ref. No.: CEJ-D-13-02942 LIST OF CHANGES Reviewers' comments:REVIEWER 1: The manuscript dealed with the furfural production from woody biomass. If the manuscript just focused on the optimization of two stage of furfural production, the novelty seems not enough. The authors were suggested to provide some evidences for advantages of two stage process as compared with single stage. In many parts, the writing hard to be understood. RESPONSE TO REVIEWER COMMENT:(*) The use of lignocellulosic biomass as a sustainable, renewable raw material for the production of chemicals and energy is steadily gaining interest. Despite the difficulties, especially as regards the need to fractionate its components in order to make the process cost-effective, there is increasing experimental evidence of its viability. For example, research has shown the possibility of obtaining ethanol as main product, but also that other structural components such as hemicelluloses and polyphenols (lignin) can be useful to obtain foods, pharmaceuticals, plastics, paper and basic chemicals, among others, by using a series of process known as "Biorefining". An ...

Lignocellulosic material from Leucaena leucocephala was subjected to a two-stage fractionation process to obtain a valorized effluent containing hemicellulose derivatives and a solid phase for producing cellulose pulp by conventional soda-anthraquinone delignifi¬cation. The first autohydrolysis stage allows up to 46.6% of the initial hemicellulose in the raw material to be extracted as xylooligomers, xylose and furfural into the liquid phase. Alkaline cooking of the solid residue from this stage with NaOH-AQ allows the production of cellulose pulp and paper sheets (161-177 ºC, 17-25 %, 60-120 min) with properties on a par with those obtained without a prior autohydrolysis stage (169-185 ºC, 21-29 %, 90-150 min) and by using milder delignification conditions; also, it provides a hemicellulose-containing liquid phase with added value.

A selection of the best wood raw materials for cellulose pulp and papermaking from five varieties of the Leucaena has been made (Leucaena diversifolia, Leucaena colinsii and three varieties of Leucaena leucocepha) with growth periods of one, two and three years. In accordance with biomass production and the features of the raw materials and cellulose pulp obtained, Leucaena diversifolia in its second year of growth was selected as the most suitable material for pulp and papermaking. Pulping of L. diversifolia by soda-ethanol was studied using an experimental design in order to investigate the effects of cooking variables: temperature, time, soda concentration, ethanol concentration and washdisintegrate temperature on the chemical composition of the obtained pulps (yield, kappa number, viscosity, solubles substances, lignin, holocellulose and α-cellulose contents) and the physico-chemical characteristics of paper sheets (tensile index). The results were evaluated using the response surface methodology. The optimum pulping conditions were established for this lignocellulosic material, using the model predictions. The pulp obtained at these conditions has suitable chemical (pulp) and physical (paper sheets) characteristics: yield (46.5%), 1%NaOH solubles (3.04%), hot water solubles (0.63%), ethanol-benzene extractives (0.44%), holocellulose contents (96.7%), α-cellulose contents (75.8%), lignin contents (0.85%), viscosity (1367) kappa number (15.2) and tensile index (19.2 kN m/kg).