Nowadays, the increasing energy demand, depletion of fossil fuels and global warming issues have motivated our society to look for alternative sources in order to produce energy, fuels and chemicals. In this sense, biomass is one of the most promising alternative carbon source which is renewable and potentially sustainable and thus a high research effort has been made for the conversion of cellulosic biomass towards platform chemicals. These kind of reactions are related to a high energy consumption and low selectivities to the desired products. Therefore, the design of selective and efficient catalysts for these purposes is a very important task. The combination of acidic properties and active metal sites in the same catalyst appears as a good alternative for the conversion of biomass into added valuable chemicals such as sorbitol. Sorbitol is an important feedstock for food and pharmaceutical industry and intermediate for the synthesis of isosorbide and 1,4-sorbitan. Moreover, in recent years the production of alkanes from sorbitol has been demonstrated by successive dehydration (on acidic sites) and hydrogenation reactions (on metallic sites).
The aim of this work consists on the study of the kinetics of the hydrolytic hydrogenation of cellobiose to sorbitol using a bifunctional Ru/Al-MCM48 (3.5 wt.% metal loading). Additionally, possible reaction pathways and key intermediate compounds of this reaction are discussed. In the kinetic study the effects of pressure, temperature and time on the hydrogenolysis reaction are evaluated and a kinetic model covering different reaction temperatures is developed (Figure 1). A maximum yield about 92 % of hexitols was achieved by catalytic hydrogenation of cellobiose over Ru/Al-MCM48 at 180 ºC, 5 MPa H2 and 7 min (82% Sorbitol, 8% Mannitol and 2% iditol). Cellobitol was the main intermediate of the reaction over Ru/Al-MCM48. Temperatures in the range of 140 – 180 ºC and pressures in the range of 30 – 50 MPa H2 were studied and it was concluded that higher temperatures and pressures had a positive effect in order to maximize the production of hexitols.
Alberto Romero – project E-47-2015-0062773 JCyL