Catalytic Conversion of Glycerol to Value-Added Chemical Products

Rapid expansion of biodiesel industry has generated a huge amount of crude glycerol. This thesis aimed to explore utilization of glycerol for the production of solketal as an oxygenated fuel additive and 1, 2-propanediol as a pre-polymer via catalytic conversion. The thesis work may be divided into two major parts. In the first part, the thermodynamics and kinetics of the glycerol ketalization for the synthesis of solketal were investigated in a batch reactor. From this information, a continuous-flow process was designed, developed and optimized using pure glycerol. Crude glycerol (13 wt% purity) was successfully upgraded into a purified crude glycerol product (\u3e 96 wt% purity) and was used as feedstock in a modified reactor for the synthesis of solketal whose economical feasibility was demonstrated. In the second part, B2O3 promoted Cu/Al2O3 catalysts were used for selective hydrogenolysis of glycerol to 1, 2-propanediol in a flow reactor. Surface properties, acidity, crystallinity, and reducibility of the catalysts were measured using N2 adsorption, NH3-temperature programmed desorption (TPD), X-ray diffraction (XRD), and H2-temperature programmed reduction (TPR), respectively. The fuels/chemicals products obtained were analyzed by GC-MS/FID and Fourier-transformation infrared spectroscopy (FTIR). The ketalization reaction equilibrium constants were determined experimentally in the temperature range of 293-323 K. The activation energy of the overall reaction was determined to be 55.6 ± 3.1 kJ mol-1. Langmuir-Hinshelwood equation was used to model the rate law. The activity of all catalysts tested in the flow reactor follows the order: Amberlyst wet » Zeolite » Amberlyst dry \u3e Zirconium Sulfate \u3e Montmorillonite \u3e Polymax. At optimum conditions (25 ˚C, 500 psi, acetone-to-glycerol molar ratio of 4 and 2 h-1 WHSV), the maximum solketal yield from pure glycerol was 94±2% over Amberlyst wet. Ketalization of purified crude glycerol over Amberlyst wet, led to 93± 3% glycerol conversion with 92 ±2% solketal yield at the optimum conditions. In the glycerol hydrogenolysis process with 10 wt% aqueous solution of glycerol as the feed, 5Cu-B/Al2O3 catalyst demonstrated a very high activity, yielding 98 ±1% glycerol conversion and 98±1% 1,2-propanediol selectivity at the optimum conditions (250 ˚C, 6 MPa H2, and 0.1h-1 WHSV)