Low pressure hydrogenolysis of glycerin to propylene gycol [abstract]
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Hydrogenolysis of glycerin to propylene glycol using a copper-chromite catalyst was performed on both a lab scale and pilot scale system. Temperature, pressure, hydrogen flow, residence time in catalyst beds, and amount of catalyst were evaluated. System parameter control and management were essential to scale up success in industrial application, and were closely monitored and controlled using Labview 7.1 software. Highest yield and selectivity of propylene glycol were observed at temperatures of 220˚C to 235˚C and pressures less than 1 atm. Over-reaction of the glycerin due to relatively long residence time in catalyst beds led to decreased propylene glycol selectivity and higher “junk peak” observance on the Gas Chromatogram results. Under-reaction of the glycerin due to high flow rates of glycerin and hydrogen and relatively short residence periods in the catalyst bed resulted in low propylene glycol yield and low glycerin conversion. Upon one distillation after water removal, the raw product yielded 98.5% to 99.5% pure propylene glycol. This process, being highly innovative in its low pressure design of the reaction, shows potential for a very economical method of industrial production.