The Effects of Space Time and Glycerin to Methanol Ratio Upon the Supercritical Water Reformation of a Crude Glycerin Solution for Hydrogen Production

Biodiesel is a renewable energy with great potential due to the fact it can be used in existing automobile engines. The transesterification of triglycerides used to produce biodiesel also produces a large amount of glycerin byproduct. Most biodiesel plants need to sell their excess glycerin to remain profitable. This poses a challenge because the crude glycerin solution must be purified of excess methanol reactant before it can be sold and the supply of glycerin greatly exceeds the demand.  An alternative to this is the supercritical water reformation of the crude glycerin solution into hydrogen for energy applications. This non-catalytic process utilizes the crude glycerol solution and removes the need for an energy intensive purification step.  Reformation of crude glycerin also increases the amount of usable transportation fuel that may be produced from triglycerides in biodiesel production. The effect of space time and glycerin to methanol ratio on the supercritical water reformation of a crude glycerol solution was evaluated in an experimental study. The experimental study was conducted using a 0.1 L Inconel 625 reactor at a constant pressure of 22.4 MPa with a water-to-carbon molar ratio of 8:3. The space time was varied between 50 and 150 seconds at temperatures of 500˚C and 600˚C using a crude glycerin solution of 70 wt% glycerin and 30 wt% methanol.  The crude glycerin solution was varied between 60 wt% glycerin and 40 wt% methanol to 80 wt% glycerin and 20 wt% methanol at a temperature of 600˚C and a space time of 100 seconds.