Fly ash based Ni catalyst for conversion of sorbitol into glycols

Abstract

Hydrogenolysis of sorbitol into glycols and alcohols has been carried out in an aqueous medium using Ni (3, 6 and 10wt%) supported on fly ash, an ‘industrial waste’. The reaction was carried out in an aqueous medium using a 15wt% solution (40g) of sorbitol and 0.2g of the reduced catalyst in a stirred high pressure reactor at different temperatures and pressures in H2. The major products of the reaction at 60bars and 200°C were 1,2-propanediol, glycerol and ethylene glycol. Adding Ca(OH)2 (0.2g) to the reaction medium increased sorbitol conversion and selectivity for propanediol, and also appeared to prolong catalyst activity. Conversion increased with increasing amounts of Ni (3–10%), the increase in conversion being not so significant beyond 6% Ni. The 6% Ni catalyst was investigated in greater detail at different temperatures (160–220°C) and pressures (40–80bars). Ni(6%)/fly ash was reusable many times with only a minor activity loss.