Thermochemical conversion of crude glycerol to biopolyols for the production of polyurethane foams

•High-quality biopolyols were produced from a sole feedstock of crude glycerol.•Properties of biopolyols depend on H2SO4 loading, reaction temperature and time.•Polyurethane foam with satisfied performance was produced from the biopolyols.•The biopolyols were mainly composed of glycerol, monoglycerides, and diglycerides.•Eesterification, transesterifaction and dehydration are major reactions. This study aimed to produce biopolyols from crude glycerol via a novel thermochemical conversion process. The effect of operational parameters, including sulfuric acid loading and reaction temperature and time, on the properties of the produced biopolyols was investigated. Biopolyols produced under preferred reaction conditions of 200°C, 90min, and 3% sulfuric acid loading showed a hydroxyl number of around 481mg KOH/g, an acid number of around 5mg KOH/g, and a viscosity of around 25.0Pas. The resulting polyurethane (PU) foams showed a compressive strength of around 184.5kPa and a density of around 43.0kg/m3, comparable to those of some petroleum-based analogs. Characterization of the biopolyols via pyrolysis-gas chromatography–mass spectrometry (Py-GC–MS), gas chromatography (GC), and thermogravimetrical analysis (TGA) showed that the major reactions of this process were the formation of monoglycerides and diglycerides through the esterification and transesterification of different components in crude glycerol.