Subcritical and Supercritical Water Liquefaction of Rice Husk for Production of Heavy Oil and SiO_2 Gel

摘要

Liquefaction of rice husk in sub/supercritical water was investigated with and without Na_2CO_3 catalyst. Experiments were conducted in a 150 ml high-pressure autoclave reactor at temperatures ranging of 280-380 D for 10-90 min. The influence of temperature, reaction time and mass ratio of rice-to-water on products distribution was discussed in present work. The optimization of experimental operations was confirmed at 300°C for 10 min with the R/W ratio of 0.2. The maximum of heavy oil yield was found to be 29.8 wt%, which was obtained under optimum operations with 12 wt% Na_2CO_3. The heavy oils from with and without catalyst were identified using FTIR and GC-MS. The results showed that the heavy oil from without catalyst mainly contained phenolic compounds, ketones and carboxyl acids, while that from with Na_2CO_3 mainly consisted of phenol derivatives, esters, long-chain hydrocarbons, ketones and alcohols. Silicon dioxide gel was obtained by treatments of solid residue from subcritical water liquefaction of rice husk. The particle size of silica gel was found to be in the range of 50-100nm by means of SEM.