Direct liquefaction of paulownia in hot compressed water: Influence of catalysts

The liquefaction of paulownia in hot compressed water with and without the presence of catalysts such as Fe and Na2CO3 was studied to investigate the catalyst’s effects on the biomass liquefaction process. Experiments were conducted in a 1000 ml stainless steel autoclave in the conditions of temperature range of 280–360 °C for 10 min under vacuum, with 60 g biomass and 360 g water, respectively. All the catalysts tested, i.e., Na2CO3 and Fe, were found effective for enhancing the formation of heavy oil products, while they significantly promoted the formation of gas. The experimental results showed that the maximum heavy oil yield rate was 36.34% with Fe catalyst and the minimum solid residue yield was obtained when Na2CO3 was employed as catalyst. The heavy oils from with and without catalyst were characterized by GC–MS and FTIR. The results showed that the oils mainly contained phenol derivatives, ketones, carboxylic acid/ester, benzene derivatives and long-chain alkanes, aldehydes and its derivatives and that employing different catalysts could change the distribution and relative abundance of produced compounds.