Study On Catalyzed Conversion Of Lignocellulosic Biomass Into Polyols On Supported Metal Catalyst

Biomass resource has become an ideal substitute for fossil energy since the abundance and renewability,and it is expected to alleviate the environmental problem resulting from overuse and abuse the fossil fuels.In recent years,catalytic conversion of lignocellulose to high added-value chemical and liquid fuels is efficient for the utilization of biomass resources.In this study,the supported bimetallic catalysts with high activity and selectivity were prepared to promote the effective utilization of conversion lignocellulose into polyols.It was to investigate the catalytic activities of different metal components and synergism between active metal and support,which provides guidance for exploring the process and developing new system of catalyzed hydrolysis of cellulose.Specially,the main research contents are given as follows:(1)The supported non-noble metal catalysts were synthesized by using impregnation method on MCM-41 and applied to the catalytic conversion of cellulose.It was found that the catalytic activity of metal tungsten was higher among the mono-metal catalysts.One-pot conversion of cellulose obtained a 32.68 wt%polyols yield on W/MCM-41.Introducing Fe,Co and Ni,the bimetallic catalysts were prepared.W-Ni catalyst showed excellent performance on conversion of cellulose,and W-Ni/MCM-41 obtained 50.58%of polyols yield which increased by 17.9 wt%as compared with the single tungsten catalyst.(2)Molecular sieve(MCM-41 and ZSM-5)and carbon materials(Graphene and Expanded Graphite)were used as supports.The supported metal catalysts were prepared for catalytic conversion of cellulose to investigate the effect of metal and supports.It is indicated that the catalytic interface was excellent between metal components and MCM-41.W-Ni metal components showed excellent catalytic capability on different supports,which followed in sequence by W-Ni/MCM-41>W-Ni/ZSM-5>W-Ni/Expanded Graphite>W-Ni/Graphene.Catalytic conversion of cellulose obtained the diols yields(including ethylene glycol and 1,2-propylene)were 46.35 wt%,36.53 wt%,31.32 wt%and 30.83 wt%,respectively.It is clear that mesoporous molecular sieve with large surface area and uniform pore size could improve the calalytic activity of metal components and selectivity of catalytic hydrogenation of cellulose.(3)Mesoporous silica microsphere(MSM)was selected as support and 15%W-5%Ni/MSM catalyst with highly dispersed metal sites was obtained.Catalytic conversion of cellulose obtained an 85.24 wt%diols yield attaching a 67.0%selectivity of EG as the synergistic effect of Ni and W and the unique structure of MSM which was favorable for the mass-transfer and metal-load.15%W-5%Ni/MSM catalyst was also applied to the pretreated corn stalk samples,affording a superior performance with a maximum of 62.6 wt%owing the pretreatment of acid and alkali could remove part of lignin and hemicellulose and increase the component of cellulose.The catalytic process mainly involves three reactions:cellulose hydrolysis,C-C cleavage and hydrogenation.(4)Designing the new reaction system of 15%W-5%Ni/MCM-41 combined with HZSM-5 to promote the conversion of cellulose to polyols.When the mass of HZSM-5-(100)increased from 0 g to 0.05 g,the diols yields increased from 63.18 wt%to 78.41 wt%and selectivity of EG reached 70.3%.It was also found that the number of Browsteric acid,pore volume and pore size incrased with increasing molar ratio of SiO2/Al2O3,which could conduce to enhance the activity and selectivity of catalyzed hydrolysis of cellulose.