In this study, a one-pot catalytic reaction process was studied for the production of biopolyols and polyurethane (PU) foam from crude glycerin – a byproduct of the biodiesel process. The goal of this study was to identify the workable ranges of critical parameters of the one-pot catalytic process that affect the properties of biopolyols and polyurethane foam. To fulfill this purpose, the specific project objectives were to: (1) study the effects of one-pot catalytic reaction operating parameters on properties of crude glycerin-based biopolyols and resulting PU foam, and (2) determine the effect of crude glycerin composition on the properties of biopolyols and PU foam.
Firstly, the effects of operating parameters of the one-pot catalytic reaction process, including reaction time (30-210 min), temperature (150-210°C) and sulfuric acid loading (0%-7.5%), on the properties of crude glycerin-based biopolyols and mechanical properties of rigid PU foam were studied. Reaction temperature, sulfuric acid loading, and reaction time substantially affected the properties of crude glycerin-based biopolyols and resulting PU foam. The acid number, hydroxyl number, and viscosity of the crude glycerin-based biopolyols ranged from 2 to 38 mg KOH/g, 546 to 795 mg KOH/g, and 337 to 13950 cP, respectively. The density and compressive strength of PU foam ranged from 31.0 to 65.4 kg/m3 and from 51 to 112 KPa, respectively. The highest compressive strength (112 KPa) of PU foam was obtained with biopolyols produced with 5% (w/w) sulfuric acid loading and reacted at 210°C for 60 min.
Secondly, the effects of crude glycerin components, including glycerin, soap, and fatty acid methyl ester (FAME), on the properties of biopolyols and rigid PU foam were tested. Increasing glycerin content led to increases in the hydroxyl number of biopolyols and the compressive strength of PU foam. However, increasing glycerin content increased the amount of isocyanate required for foam formulation and the density of PU foam. When the glycerin content was too high, the PU foam was too hard to be usable. Based on these results, it was concluded that the glycerin content should be around 40% by total weight for PU foam applications. Soap addition reduced the hydroxyl number of biopolyols due to esterification, which occurred between the soap and glycerin, and therefore decreased the compressive strength of PU foam. Soap addition decreased the amount of isocyanate required for foaming. However, when the soap content was 80% or higher by total weight, the resulting biopolyols could not be used to prepare PU foam. It was observed that FAME addition prolonged the rise time of PU foam. Moreover, when the FAME content exceeded 40% of total weight, the resulting biopolyols could not be used to produce PU foam.