Study On Catalytic Liquefaction Transfer Of Hydrogen Peroxide In Supercritical Methanol

The rapid development of the world economy leads to the rapid growth of energy consumption. More and more people are concerned with the development and utilization of clean, renewable energy because of finite reserves and unrenewable nature of fossil fuel and environmental pollution caused by it. Biomass energy is the only carbon-fixed energy among all the renewable energy on the earth and gets a great potential of exploitation and utilization with large reserves and wide distribution. The researches and fundamental data of cellulose liquefaction have a significant meaning in the development and utilization of biomass as cellulose is the main component of biomass.This paper introduces one-pot conversion and transfer hydrogenation of cellulose to alcohols with CuO/MgO/Al2O3catalyst in supercritical methanol.Copper-based catalyst was chosen in the experiment of catalyst preparation.A series of CuO/MgO/AkOs based catalysts were prepared by calcination of the CuO/MgO/AbOs hydrotalcite precursor which was synthesized by the co-precipitation method with the same Cu/Mg/Al molar ratio of15:60:25at various temperatures. The catalysts were characterized by XRD、TG/DTG、BET、H2-TPR and FT-IR to explore the effect of calcination temperature on the transfer hydrogenation liquefaction of cellulose over CuO/MgO/Al2O3catalysts. The results showed that CuO/MgO/Al2O3hydrotalcite was almost completely decomposed at450℃. It has a better stability because of the proper force between CuO and MgO and a better catalytic activity because of the uniformity of CuO at such a temperature.Direct liquefaction of cellulose over CuO/MgO/Al2O3catalyst has been carried out in an reaction vessel. A series of experiments have been conducted to investigate the influence of reaction temperature, reaction time, catalyst amount, ratio of cellulose to methanol on liquefaction of cellulose. The optimum conditions and best economic conditions have been achieved through orthogonal tests. The results showed that the optimal conditions are reaction temperature320℃, reaction time3h, cellulose-methanol ratio with1:50g/ml, the catalyst amount of75%. Under these conditions, the liquefaction conversion rate reaches99.83%. The best economic condition are reaction temperature320℃, reaction time3h, cellulose-methanol ratio with1:40g/ml, the catalyst amount of25%. Under these conditions, the liquefaction conversion rate reaches99.83%. The liquefaction mechanism has been studied preliminarily by the means of GC-MS. The results showed that glucosides and levoglucosan are the main liquid products of cellulose without catalyst in supercritical methanol, while C3-C7alcohols are the main products of cellulose with CuO/MgO/AbOa catalyst. CuO/MgO/AlaO3catalyst could both promote methanol stream reforming and hydrogenation of carbohydrates. Cellulose decomposes into reactive intermediates CnH2n+2-x(OR)x (R-H,CH3) with the cracking of C-O, C-C, hydrogen bond and hydroxyl under the conditions of high temperatures and high pressures in supercritical methanol. A large amount of active H was generated through the hydrogen transfer reaction of methanol with the effect of catalyst, then added to the carbon oxygen double bonds of intermediates, which further convert to higher alcohols.On the basis of above experiments, liquefaction kinetics of cellulose with catalyst in supercritical methanol were investigated by model fit method. The first order reaction kinetics model calculation indicates that the apparent activation energy of cellulose liquefaction over CuO/MgO/Al2O3catalyst is115.066kJ/mol, and the pre-exponential factor is20.20. The reaction rate has been greatly improved compared with that without catalyst.