1. By-product Formation in Respect of Operating Conditions on Conversion of Glycerol to Propylene Glycol Mona-Lisa Banks, Dr. Galen Suppes, Dr. Rusty Sutterlin, Ali Tekeei, Chuang-Wei (Roger) Chiu Missouri Soybean Merchandizing Council, Department of Chemical Engineering, University of Missouri Columbia, Lincoln University Louis Stokes Missouri Alliance for Minority Participation INTRODUCTION PROCEDURE RESULTS AND DISCUSSIONS CONCLUSION ABSTRACT Glycerol is a colorless odorless viscous by-product of biodiesel. Biodiesel is derived form vegetable oil and animal fat. For every 9 kilograms of biodiesel produced, about 1 kilogram of glycerol by-product is formed. Over the years biodiesel production has increased dramatically thus the production of the crude glycerol byproduct has also increased. This has resulted in decreased glycerol prices, causing the byproduct to be sometimes discarded as waste as it is costly to purify. Upgrading this crude glycerol could increase the profitability of biodiesel production thus reducing the cost of producing biodiesel. Propylene glycol is a product with a 4% growth in the market annually. Propylene glycol can be used in the manufacturing of antifreeze for cars, airplanes and boats. It is used to absorb extra water and maintain moisture in certain foods, cosmetics, and medicines. Other uses include the production of detergents, fragrances, and paints among others. The main focus of this research is to convert glycerol into propylene glycol. The processing of converting glycerol to propylene glycol uses metallic catalysts and hydrogen and is called hydrogenolysis. The chemical reaction of glycerol to propylene glycol is achieved by removing one molecule of water and then hydrogenating the process to make propylene glycol. Fig. 1 Reaction mechanism for conversion of glycerol to propylene glycol. The conversion reaction of glycerol to propylene glycol (PG) results in the yield of different products namely acetol, water, PG and it has also shown little selectivity toward ethylene glycol and other unknown by-products. In order to optimize the reaction process achieving maximum production PG seven of the most prominent unknowns have been chosen to carry out the study where the trends are studied in relation to propylene glycol and reaction conditions. The liquid samples were weighed and analyzed with a Hewlett-Packard 6890 (Wilmington, DE) gas chromatograph (GC) equipped with a flame ionization detector. Hewlett-Packard Chemstation software was used to collect and analyze the data. A Restek Corp (Bellefonte, PA) MXT® WAX 70624 GC column (30m x 250 µm x 0.5µm) was used for separation. For preparation of the GC samples, a solution of n-butanol with a known amount of internal standard (IS) was prepared a prior and used for analysis. The samples were prepared for analysis by adding 100 µL of product sample to 1000 µL of stock solution into a 2mL glass vial. Two micro liters of the sample was injected into the column. The oven temperature program consisted of: start at 45 °C (0 min), ramp at 0.2 °C /min to 46 °C (0 min), ramp at 30 °C /min to 220 °C (2.5 min). Chromatogram and area percentage data generated by the GC were used to prepare the graphs using Microsoft Excel. Unknowns were compared in the ratio of internal standards and PG peak areas. The conversion reaction of glycerol to propylene glycol (PG) results in the yield of different products namely acetol, water, PG and it has also shown little selectivity toward ethylene glycol and other unknown by-products. These unidentified compounds are consequently called “unknowns”. In order to maximize the production of propylene glycol these unknown by-products have to be reduced. To properly assess the unknowns, Gas Chromatograph (GC) testing is done on the finish product in order to create new methods to eradicate the unknowns. PG and seven of the most prominent unknowns were chosen to carry out the study where the trends are studied in relation to propylene glycol and reaction conditions. The seven unknowns are named as the retention time shown in the gas chromatogram 8.74, 8.78, 9.11 (Ethylene Glycol), 9.15, 9.28, 9.32, and 9.405. The impact of two independent reaction parameters were investigated—referred to as Parameter A (PA) and Parameter B (PB). At higher PA less unknown are produced during the reaction. The value of PB applied in this reaction is very critical as the higher values result in the production of more unknowns and less PG in the end product. Based on this analysis, the reaction should be conducted at higher value of PA and low PB. REFERENCES & ACKNOWLEDGEMENT The reaction of glycerol to PG indicated that PG increased as a result of increased PA and decreased with increased PB. Low PB and high PA shows a higher yield in PG. The unknowns studied increased in their amounts with increased PB and decreased with lower PA levels. The reaction of acetol to PG follows the trends as the reaction of glycerol to propylene glycol. The reaction of PG to acetol indicated that acetol increased as a result of increased PB and decreased with increased PA. The unknown EG was not observed in this reaction. The unknowns formed in this reaction increased in their amounts with increased PB and decreased with higher PA. This work was funded by the Missouri Soybean Merchandising Council. Dasari MA, Kiatsimkul P, Sutterlin WR, Suppes GJ. Low-pressure hydrogenolysis of glycerol to propylene glycol. Applied Catalysis A:General. 2005;281(1-2):225-231. Suppes GJ, Sutterlin WR, Dasari MA. Method of producing lower alcohols from glycerol. US Patent Application 20050244312., 2005. Chiu C-W, Dasari M.A., Sutterlin W.R., Suppes G.J. Dehydration of Glycerol to Acetol via Catalytic Reactive Distillation. AIChE Journal. (accepted) Reaction PG to acetol  The conversion indicated that acetol increased with increased PB and decreased with increased PA.  The unknown EG was not observed in this reaction—EG is a product from Glycerol reaction.  Greater amount of unknowns were produced with increased PB.  Less amount of unknowns were produced with increased PA. Reaction Glycerol to Propylene GlycolReaction Propylene Glycol to Acetol Reaction glycerol to PG  The conversion indicated that PG increased with increased PA levels.  PG decreased with increasing PB.  The unknown 9.11 was identified as Ethylene Glycol (EG) and was the only unknown studied that followed PG production. EG increased with increased PG production but was not observed to follow any obvious trend in relation to PA and PB.  Greater amount of unknowns were produced with increased PB.  Less amount of unknowns were produced with increased PA. Reaction acetol to PG  Trends of all unknowns in this reaction agreed with the trends of all unknowns observed in the reaction glycerol to RESULTS AND DISCUSSIONS cont’d PB Values of PA PB Values of PA