Catalytic conversion of glycerol to value added liquid products

Catalytic conversion of glycerol was performed for production of value-added liquid chemicals. In this work, a systematic study has been conducted to evaluate the effects of operating conditions such as glycerol conversion to liquid chemical products in the presence of acid catalysts. Experiments were performed in a fixed-bed reactor using HZSM-5, HY, silica-alumina and γ-alumina catalysts. The temperature, carrier gas flow rate and weight hourly space velocity (WHSV) were maintained in the range of 350–500 °C, 20–50 mL/min and 5.40–21.60 h −1, respectively. The main liquid chemicals detected in liquid product were acetaldehyde, acrolein, formaldehyde and hydroxyacetone. Under all experimental conditions complete glycerol conversion was obtained over silica-alumina and γ-alumina. A maximum liquid product yield of approximately 83 g/100 g feed was obtained with these two catalysts when the operating conditions were maintained at 380 °C, 26 mL/min and 8.68 h −1. Maximum glycerol conversions of 100 wt% and 78.8 wt% were obtained in the presence of HY and HZSM-5 at temperature, carrier gas flow rate and WHSV of 470 °C, 26 mL/min and 8.68 h −1. HY and HZSM-5 produced maximum liquid product of 80.9 and 59.0 g/100 g feed at temperature of 425 and 470 °C, respectively. Silica-alumina produced the maximum acetaldehyde (∼24.5 g/100 g feed) whereas γ-alumina produced the maximum acrolein (∼25 g/100 g feed). Also, silica-alumina produced highest formaldehyde yield of 9 g/100 g feed whereas HY produced highest acetol yield of 14.7 g/100 g feed. The effect of pore size of these catalysts was studied on optimum glycerol conversion and liquid product yield. The optimum operating conditions to obtain the maximum glycerol conversion over HZSM-5 (78.8 wt%) and HY (100 wt%) were 470 °C, 26 mL/min and WHSV of 8.68 h −1. Optimum conversion increased from 80 to 100 wt% and optimum liquid product increased from 59 to 83.3 g/100 g feed when the pore size of catalyst was increased from 0.54 in case of HZSM-5 to 0.74 nm in case of HY; beyond which the effect pore of size was minimal.