Furfural Production Using Hydrolysate From Eucalypt Woodchips Pre-hydrolysis

During traditiona dissolving pulp production, the most of the hemicellulose in the rawmaterials is directly discharged into the pulping effluent, which not only pollutes theenvironment but also wastes biomass resources. It is well-known that the hemicellulose can beproduced various biomass fuels and biomass chemicals, such as ethanol, furfural, xylitol and soon. If these hemicllulose resources are effectively utilized, they can make additional benefits.Therefore, how to use these abandoned hemicllulose resources of pulping process will havevery important meanings both on the full use of resources, environmental protection andsustainable development of pulp and paper mills under the financial crisis.The paper mainly focused on pre-hydrolysate of eucalypt woodchips dissolving pulpprocess. Firstly hemicellulose was extracted by high-temperature water hydrolysis and then thehemicellulose hydrolysate was separated from the digester system. With sulfuric acid as acatalyst, furfural was produced in a high pressure reactor, while the eucalypt woodchips afterprehydrolysis was used to prepared the produce dissolving pulp. Main research contents andresults were summarized as follows:(1)Process optimization for hemicellulose extraction from eucalypt woodchips in hightemperature water. It was found that when the process was temperature of170°C, holding timeof60min and the liquid-solid ratio of5:1, the extraction rate of the hemicellulose wasmaximum, with48.75%.(2)The main sugar content analysis of pre-hydrolysate. Iion chromatography resultsshowed that the main surgar of pre-hydrolysate was xylose and xylo-oligosaccharides (averagedegree of polymerization2~6), and that pre-hydrolysate had a small amount of cellobiose andcellotriose. Moreover, water extraction conditions made the content of various sugar different.(3)Process optimization of furfural preparation from pre-hydrolysate. The effect ofconditions were studied one by one and then orthogonal experiment was designed to get thebest preparation process for furfural. It could be found that the yield of furfural reached amaximum of71.89%when temperature was180°C, H2SO4concentration was0.25%and gasproduction rate was15ml/min. (4)The purity of furfural in the preparation liquid. GC/MS results showed that the relativecontent of furfural was93.32%,that the main byproduct was5-methylfurfural with the relativecontent of5.31%and that the content of other byproducts was little, such as2-acetylfuran ando-methoxyphenol.(5)The reason for coking phenomenon during the furfural preparation. It was found thatcoking phenomenon was due to the charring of the sugar and the existence of lignincomposition and some polysaccharide in pre-hydrolysate.(6) Dehydration kinetics using sulfuric acid was studied. The results show that thedehydration is a first order reaction of intrinsic kinetics.