Catalytic Conversion Of Hemicellulose-Pentose Into Furfural By Ionic Liquid

As an important platform chemical and feedstock to produce various chemicals and liquid fuels,furfural(FF)can be produced by the conversion of biomass pentosan.Through further hydrogenation,oxidative dehydrogenation,esterification,halogenation,polymerization,hydrolysis and other chemical reactions,thousands kind of chemical products and produced directly or indirectly.Due to the lack of in-depth study on the efficient preparation of furfural by liquid-phase decomposition of biomass,the application of biomass liquefaction technology has been restricted to same extent.In the current commercial FF production process,mineral acids such as sulfuric acid and hydrochloric acid are used for catalytic,however not high yield,equipment corrosion and other issues prompt more and more researchers to develop a more efficient green catalyst reaction system.Supported by National Natural Science Foundation,we selected a range of ionic liquid as catalysts,a thorough and systematical research on the furfural preparation from liquid phase decomposition of biomass,especially hemicellulose-pentose has been carried out.Considering that xylose is the most abundant pentose in hemicellulose,we firstly discussed the transformation of xylose in the reaction system of Br(?)nsted acidic ionic-liquid and renewable GVL solvent.The results showed that the introduction of GVL improved the rate of reaction and promoted the conversion of xylose and the yield of FF compared with the pure water phase.With the increase of the reaction temperature,the yield of FF increased first and then decreased,FF yield of 78.12%was obtained at 140 ?.In addition,compared with four different types of sulfonated ionic-liquid catalytic effect,we found that more than 69%FF yield can be obtained,indicating that sulfonation of ionic-liquid is a good method to prepare FF.We also analyzed the transformation of arabinose and xylan in the system,which gained moderate FF yields.In order to reveal the preparation behavior of FF from xylose,the liquid-phase decomposition of xylose in Lewis acidic-ionic liquid was studied.The results showed that with the increase of GVL ratio in the solvent,the conversion of xylose was improved obviously.GVL:Water = 4:1,at 140 ? under 120 mins,the conversion rate reached 99.71%,FF yield was 79.81%,which was higher than 54.08%(GVL:Water=4:1).This is because too high content of GVL in the solution will lead to the insufficient hydrolysis of Al3+,which results in the decrease of catalytic effect of Lewis acid ionic liquid.However,with the increase of reaction time,the yield of FF obtained by hydrolysis was decreased to a certain extent due to the secondary reaction to form humin and other products.At the end of this thesis,arabinose-an important composition of the pentose in hemicellulose was studied in detail.With the same solvent system composed of GVL and water,Lewis acid-ionic liquid was also used as the catalyst.The experiment results were similar to xylose,but with lower conversion rate and FF yield.This is because the configuration of pentose affects the reactivity of sugar,arabinose is mainly a-pyran configuration,and this structure is more stable than xylose which is a ?-type pyranose when hydrolysis to produce FF.Compared with the conversion of arabinose under the conditions of Bronsted acidic ionic liquid as catalyst at the same reaction condition(140?,180min.),the results showed that Lewis acid was more favorable for the conversion of arabinose to FF(58.46%>24.46%).