(544t) Corncob Residue As a Valuable Resource for the Production of Aromatics

The utilization of lignocellulose as a raw material for the production of renewable fuels and chemicals is growing rapidly. Model compounds and wood lignin have been investigated widely. In this work, we study the conversion of enzymatic hydrolysis corncob residue using NiMo/γ-Al₂O₃ catalyst in supercritical ethanol system at 320 ^oC. The effects of reaction parameters such as hydrogen pressure, reaction time, temperature and solvent are investigated. The liquid products are analyzed with GC-MS and GC. The results show that the NiMo/γ-Al₂O₃ catalyst give a higher overall aromatics yield, 124.7 mg/g enzymatic hydrolysis corncob residue, while the NiMo catalyst supported on activated carbon exhibits much lower overall yield. Meanwhile, almost all enzymatic hydrolysis corncob residues are liquefied, and 70.0% of the aromatics are phenolic monomers, among which 4-ethylphenol is the dominating product with a high selectivity of 23.3%. Notably, no tar or char is formed.

We find that γ-Al₂O₃ plays a key role in the conversion of corncob residue. At the same time, the Ni⁰ and Mo species are responsible for hydrogenolysis and deoxygenation activity. γ-Al₂O₃ is very effective in alkylation of lignin monomers in a supercritical system, which is in accordance with the high selectivity of alkylphenol. Lignin experiences a noncatalytic ethanolysis step and forms medium fragment, which are completely depolymerized through the dissociative Mo active species. Subsequently the Ni⁰ species also plays an important role in the ether bond cleavage, while γ-Al₂O₃ catalyze the alkylation of reactive intermediates, which makes monomers more stable to avoid re-polymerization.