Catalytic Conversion From Cellulose To Polyols

In view of the diminishing oil resources and the ongoing climate change, the use of efficient and environmentally technologies for the utilization of biomass, especially lignocellulose, has become indispensible. Cellulose has attracted intensive attention due to the abundance of cellulose?35-50% in biomass?. The catalytic conversion of cellulose to value-added polyols is an efficient way to utilize biomass. The conversion includes two consecutive reaction steps:hydrolysis of cellulose to sugars and the subsequent hydrogenation/hydrogenolysis of the intermediate sugars to polyols. However, there are many fundamental obstacles to its future development, such as the and the development of catalysts with high stability and activity.In this work, carbon nanotubes?CNTs? with high thermal and hydrothermal stability are taken as the supports for Pt and Pd-Fe. The influences of nano-particle size, surface acid functional groups on CNTs and bimetallic metal electronic effect on the distribution of the polyol products have been investigated.Pt nanoparticles supported on carbon nanotubes?CNTs? were synthesized and evaluated for the catalytic conversion of cellulose to polyols under low H₂ pressure. The results show that CNTs with acid functional groups improve the hydrolysis of cellulose Besides, highly dispersed Pt nano-particles are beneficial to the formation of ethylene glycol?EG? and 1,2-propylene glycol?1,2-PG?. By using 1% Pt/CNTs as the catalyst, highest yields for EG and 1,2-PG?34.3% and37.1%? are obtained. This shows that the formation reaction of EG and 1,2-PG are structure-sensitive reaction. The recycle experimental results showed that the decrease of EG yield mainly results from the agglomeration of Pt nano-particles.A series of carbon nanotube?CNTs? supported catalysts Pd-Fe/CNTs were synthesized and used in the catalytic conversion of cellulose into polyols. It was found that the cellulose were converted to hexitol, EG, 1, 2-PG and glycero?Gly? effectively. Notedly, the introduction of Fe improved the formation of hexitol. The highest yield of hexitol?21%? was obtained by Pd-Fe/CNTs?1:1?. This also shows that the introduction of Fe changed the electronic environment of Pt, which had an effect on the activation of the reaction substrates. Finally the distribution of product polyols was changed. The recycle experimental results showed that the bimetallic catalysts deactivate rapidly and the yield of hexitol decreased dramatically, owing to the leach of Fe.