Catalytic Hydrothermal Liquefaction Characteristics of Sewage Sludge under CO Atmosphere

Abstract

Hydrothermal liquefaction is one of the technologies that can realize the reasonable, clean and efficient utilization of sewage sludge.Thus, the effects of homogeneous catalysts (Na2CO3, NaOH, K2CO3 and KOH) and heterogeneous catalysts (JT-201and JT-203) on the hydrothermal liquefaction characteristics of sewage sludge under CO atmosphere were investigated,mainly focused on the distribution and physic-chemical properties of liquefaction products.Besides, non-catalytic hydrothermal liquefaction of sewage sludge was also investigated for comparison. The addition of catalysts can promote the hydrothermal liquefaction, and heterogeneous catalysts have a better catalytic effect than homogenous catalysts. The catalytic effect follow the order:  JT-203 >JT-201>Na2CO3> K2CO3 > NaOH > KOH.At the same time, catalysts can promote the consumption of COand generation of H2. YNHS was improved from 24.18% without catalyst to 30.46% (Na2CO3), while YLP achieved the highest 53.21% (JT-203). Catalysts can improve C content of NHS and TFS. The C element of n-hexane soluble (NHS) was improved from73.83 wt% without catalyst to 77.89 wt% (JT-203); O content of tetrahydrofuran soluble (TFS) dropped from 27.40 wt% without catalyst to 23.93 wt% (JT-203). GC-MS analysis for NHS and TFS show that nitrogenous compounds, alkanes and acidswere the main compounds of NHS. Tetrahydrofuran soluble contain nitrogenous compounds, esters, acids, phenols, ketones, alkanes and others. The main compounds of TFS are nitrogenous compounds (23.75-33.36%) and esters (20.83-47.02%).