Non-catalytic hydropyrolysis of microalgae to produce liquid biofuels

Non-catalytic hydropyrolysis of Chlorella pyrenoidosa was studied by using a stainless-steel batch reactor at different temperature (150–450 °C), time (5–120 min) and initial hydrogen pressure (1 atm–8 MPa), aiming to find how these parameters affect the product (oil, gas and solid) yields and properties of the hydropyrolysis oil (HPO). Temperature was the most influential factor to the relative amount of each product and properties of the HPOs. The hydrogen favored the stabilization of the active intermediates but cannot guarantee to produce HPOs in higher hydrogen at its higher initial pressure. The HPO, which showed much difference in component strongly depending on the reaction conditions, mainly consisted of aromatics and straight-chain hydrocarbons, amides, amines, nitriles and carboxylic acids at moderate temperatures. The main gas products detected during the hydropyrolysis were unreacted H2, CO2, CO and CH4. About 85% of energy originally present in the microalgae was recovered as oil under the optimal conditions.