M. Bao

Soda pulping of Miscanthus sinensis. Effects of operational variables on pulp yield and lignin solubilization

Abstract A simple system for the production of alkaline pulps from Miscanthus sinensis was studied. Miscanthus sinensis is a non-woody plant species of rapid growth with reported yields of up to 40 t ha−1 year−1. A first-order full-factorial design was used to analyse and evaluate the effects of variables on pulp yield and lignin solubilization. The variables studied and their respectives ranges of variation were as follows: liquid to solid ratio, 6–10; temperature, 80–100°C; time, 0–240 min; NaOH concentration, 1–2%. Good pulp yields (about 60%) and acceptable values of residual lignin (less than 10%) were obtained in the best conditions, which meant a percentage lignin solubilization close to 80%. This study also showed that selectivity of the system was independent of the working conditions and this could be summarized in the following formula: dissolved lignin/weight losses = 0·4.

Application of factorial design to the modelling of organosolv delignification of Miscanthus sinensis (elephant grass) with phenol and dilute acid solutions

Abstract The Battelle-Geneva method of fractionation of lignocellulosic materials was applied to the biomass of an annual cane-like plant, Miscanthus sinensis (elephant grass). A factorial second-order composite design was used to quantify the influences of three variables of the process (independent variables), (1) time, in the interval: 0.37–2.35 h; (2) phenol concentration, in the interval: 41.6–58.4% by weight; (3) hydrochloric acid charge, in the interval: 0.0098–0.0602 g HCl/g dry Miscanthus , on five dependent variables: (1) pulp yield, (2) residual lignin in pulps, (3) dissolved reducing sugars, (4) total polysaccharides in pulp, and (5) selectivity of the process, measured as the ratio pulp yield/residual lignin in pulp. Experimental results were fitted to second-order linear models by means of a multiple regression method. Expressions obtained showed R 2 values varying between 0.80 and 0.99, obtaining fittings from acceptable to good depending on each case. The model predicted a maximum in the selectivity for the following values of independent variables: time, 1 h 48 min: phenol concentration, 53.2%; acid charge, 0.0394 g HCl/g dry Miscanthus . With regard to the other responses variations shown were, in general, logical according to the increase or decrease of the independent variables.

Fractionating lignocellulose of Miscanthus sinensis with aqueous phenol in acidic medium.

An organosolv method of fractionation of lignocellulose (the Battele-Geneva method) has been applied toMiscanthus sinensis; a cane-like plant with a group of characteristics that makes it a promising species for its use as an energy crop.A factorial second-order composite design has been utilized to quantify the effects of independent variables (time, phenol concentration in the liquid mixture, and acid charge) on three dependent variables: Delignification efficiency, fractionation rate (or the percentage of mass losses due to prehydrolysis and delignification), and the prehydrolysis to delignification ratio. Experimental results were fitted, by non-linear regression, to second-order polinomical models, which take into account all the influences of independent variables —main, second order, and crossed interactions — on response functions. In all cases, the most influent variables are, in order of importance, acid charge, time, and phenol concentration. Quadratic terms achieve different levels of significance but, in general, the ones corresponding to acid charge are again the most important.ZusammenfassungEine Organosolv-Methode zur Fraktionierung von Lignocellulosen wurde aufMiscanthus sinensis angewandt, die als vielversprechende Spezies für Energieplantagen gilt. Eine multivektorielle Analyse zweiten Grades der Einfluß-Parameter (Zeit, Phenol-Konzentration und Säureeintrag) wurde verwendet, um die drei abhängigen Ziel-Parameter zu bestimmen, nämlich: Effizienz der Delignifizierung, Fraktionierungsgrad (oder Anteil der Masseverluste während Vorhydrolyse und Delignifizierung) und das Verhältnis von Vorhydrolyse zu Delignifizierung. Die experimentellen Ergebnisse werden durch ein Polynom zweiten Grades beschrieben, welches die Einflüsse der Ausgangsgrößen auf die Zielgrößen bestimmt (Einflüsse ersten und zweiten Grades sowie kombinierte Einflüsse). Als die wichtigsten Parameter erwiesen sich—in der Reihenfolge ihrer Gewichte—Säureeintrag, Zeit und Phenolkonzentration. Quadratische Terme haben unterschiedliche Signiftkanzen, doch auch hier waren die mit dem Säurreintrag verbundenen die wichtigsten

Fractionation of lignocellulose materials with phenol and dilute HCl

SummaryWe describe a way of fragmenting the lignocellulose material in furze (Ulex europæus) stems by chemical means. The process separates the three principal components in the stem: cellulose, hemicelluloses and lignin, by the joint action of a mixture of dilute hydrochloric acid to hydrolyse the hemicelluloses, and phenol, to dissolve the lignin. The effects of the process variables on the yield have been studied. The fractions obtained have been characterized and methods for their use are proposed.