Process optimization of preparation of ZnO-porous carbon composite from spent catalysts using one step activation.

ABSTRACT

The process parameters of one step preparation of ZnO/Activated Carbon (AC) composite materials, from vinyl acetate synthesis spent catalyst were optimized using response surface methodology (RSM) and the central composite rotatable design (CCD). Regeneration temperature, time and flow rate of CO2 were the process variables, while the iodine number and the yield were the response variables. All the three process variables were found to significantly influence the yield of the regenerated carbon, while only the regeneration temperature and CO2 flow rate were found to significantly affect the iodine number. The optimized process conditions that maximize the yield and iodine adsorption capacity were identified to be a regeneration temperature of 950 degrees C, time of 120 min and flow rate of CO2 of 600 ml/min, with the corresponding yield and iodine number to be in excess of 50% and 1100 mg/g. The BET surface area of the regenerated composite was estimated to be 1263 m2/g, with micropore to mesopore ratio of 0.75. The pore volume was found to have increased 6 times as compared to the spent catalyst. The composite material (AC/ZnO) with high surface area and pore volume coupled with high yield augur economic feasibility of the process. EDS and XRD spectrum indicate presence of ZnO in the regenerated samples.