The influence of the process conditions of pulping of a trihybrid clone Paulownia on pulp properties in the soda-anthraquinone process has been investigated. A composite central experimental design and a multiple regression were used to find the relationship between independent process variables and pulp properties. The ash content (8.9 g kg−1) is lower and cellulose content (440 g kg−1) is higher than those found for other species of Pauwlonia and other energetic crops. The elemental composition has a low content in S and N (2.1 g kg−1) in comparation with poplar or willow. With a gross heating value of 20.3 MJ kg−1. This is somewhat higher than those for hardwood, slightly higher than those for Pinus pinaster and softwood, and much higher than those for residues of food plants and agricultural crops. This supports the use of the genus Paulownia as an energy crop. Fiber length (0.97 mm) is similar to hardwoods and suitable physical characteristics of paper sheets (tensile index) and acceptable chemical characteristics and yield pulping could be obtained by operating at low-intermediate temperature (163–171 °C) and alkali concentration (200 g kg−1) and high or medium values for operation time (120–150 min). The pulp obtained at these conditions has suitable chemical (pulp) and physical (paper sheets) characteristics: yield (470 g kg−1), ethanol-benzene extractives (22.2 g kg−1), holocellulose contents (960 g kg−1), α-cellulose contents (758 g kg−1), lignin contents (82.8 g kg−1), Shopper–Riegler degree (23.2 °SR), and tensile index (36.0 kN m kg−1)

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 °C 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 °C) 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

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, arabinan, 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 L. leucocephala K366 to obtain valuable liquor and a suitable solid phase to produce energy by combustion. Valuable liquor was obtained from the autohydrolysis of L. leucocephala 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) in comparison with other raw materials. The arabinan 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 autohydrolysis 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