Hydrogenation of Flax Shives in Ethanol over a Ni/C Catalyst

Abstract

Hydrogenation of flax shives in ethanol over bifunctional Ni/C catalysts at 225 °C has been studied. It has been shown that the 10% Ni/C catalyst enhances the yield of monomeric products from 1.1 to 9.7 wt %, decreases the solid product content from 45 to 35 wt %, and increases the degree of delignification to 91%. The main monomeric compounds obtained during hydrogenation are propyl guaiacol and propenyl guaiacol. It has been established that an increase in the mass transfer intensity via increasing the stirring rate or decreasing the catalyst grain size leads to an increase in the total yield of monomeric compounds and the propanol guaiacol yield. Alkaline and acid pretreatment increases the cellulose content in the solid product from 42 to 73 wt %. The proposed sequential scheme of the transformation and formation of monomeric products over the bifunctional nickel catalyst is lignin—coniferyl alcohol—4-propanol guaiacol—4-propenyl guaiacol—4-propyl guaiacol.