Catalytic Co-Pyrolysis of Food Waste Digestate and Corn Husk with CaO Catalyst For Upgrading Bio-Oil

Abstract

The catalytic co-pyrolysis behavior of food waste digestate (FD) and corn husk (CH) with CaO catalyst for upgrading bio-oil was studied. Two kinds of CaO catalysts derived from calcining calcium hydroxide (CH-CaO) and calcium acetate monohydrate (CA-CaO) were used in this work. The char yield decreased while the bio-oil and non-condensable gas yields increased with the CH/FD mass ratio increased. Gas chromatography/mass spectrometry results showed that bio-oil from food waste digestate pyrolysis was rich in nitrogen-containing compounds (NCCs), resulting in the pH of bio-oil exhibited weak alkaline. The acid compounds in bio-oil could adjust the pH to be neutral or weakly acidic with the addition of CH. For catalytic co-pyrolysis, the relative contents of acids and esters in bio-oil decreased while the phenols increased. The contents of NCCs especially the nitrogen-containing heterocyclic compounds (pyridines, pyrroles and indoles) showed an increased trend. Ulteriorly, a reaction pathway of main NCCs during co-pyrolysis process of FD and CH was proposed in this study. Additionally, the use of CaO catalysts reduced the content of CO2 and increased the contents of H2, CO and CH4 in non-condensable gas. Compared to CH-CaO, CA-CaO exhibited better catalytic performance for upgrading bio-oil.