ABSTRACT
Developing optimum treatment and separation procedures for hemicellulose components of lignocellulosic biomass could be useful in ethanol fermentation processes and obtaining pure hemicelluloses as biopolymers. Sugarcane bagasse analyses indicate that xylose is the major hemicellulose component constituting 17.7% of dry bagasse weight. In this study the effects of treatment conditions such as time, temperature and pressure on the yields of extracted hemicelluloses were studied. The optimum conditions were achieved at 180 °C for 30 min and 1 MPa pressure, with the yield of xylose reaching to 85% and the concentrations of sugar degradation products such as HMF and furfural remaining minimal at 0.95 and 0.07 g/L, respectively. Further, isolation of hemicelluloses from extracted hemicelluloses solutions was performed using Alfa Laval M20 membrane filtration system in two steps: (1) concentration of high molar mass hemicelluloses by ultrafiltration; and (2) separation of low molar mass hemicelluloses and oligomeric sugars by nanofiltration. The isolated hemicelluloses with the optimum pretreatment conditions were characterized by FT-IR and (13)C NMR techniques, resulting in agreement with typical spectra of xylan-type hemicelluloses.
Subject(s)
Cellulose/chemistry , Chemistry Techniques, Analytical/methods , Hot Temperature , Polysaccharides/chemistry , Polysaccharides/isolation & purification , Water/chemistry , Membranes, Artificial , Saccharum/chemistry , UltrafiltrationABSTRACT
The pretreatment of biomass prior to the fast pyrolysis process has been shown to alter the structure and chemical composition of biomass feed stocks leading to a change in the mechanism of biomass thermal decomposition. Pretreatment of feed stocks prior to fast pyrolysis provides an opportunity to produce bio-oils with varied chemical composition and physical properties. This provides the potential to vary bio-oil chemical and physical properties for specific applications. To determine the influence of biomass pretreatments on bio-oil produced during fast pyrolysis, we applied six chemical pretreatments: dilute phosphoric acid, dilute sulfuric acid, sodium hydroxide, calcium hydroxide, ammonium hydroxide, and hydrogen peroxide. Bio-oils were produced from untreated and pretreated 10-year old pine wood feed stocks in an auger reactor at 450 degrees C. The bio-oils' physical properties of pH, water content, acid value, density, viscosity, and heating value were measured. Mean molecular weights and polydispersity were determined by gel permeation chromatography. Chemical characteristics of the bio-oils were determined by gas chromatography-mass spectrometry and Fourier transform infrared techniques. Results showed that the physical and chemical characteristics of the bio-oils produced from pretreated pine wood feed stocks were influenced by the biomass pretreatments applied. These physical and chemical changes are compared and discussed in detail in the paper.
