The role of contact time and input amount of 1,1,1,2-tetrafluoroethane (HFC-134a) on the catalyst lifetime and product selectivity in catalytic pyrolysis

Abstract

During catalytic pyrolysis of HFC-134a over gamma-alumina, the formation of HF and coke causes catalyst deactivation. Catalyst deactivation and product selectivity depend on the contact time during catalytic pyrolysis of HFC-134a as reported in this paper. gamma-Alumina calcined at 650 C-o was used as the catalyst due to its higher quantity of acidic sites and larger surface area, which are crucial for catalytic pyrolysis. X-ray diffraction (XRD), scanning electron microscope-energy dispersive X-ray spectroscopy (SEM-EDS), and thermogravimetric analysis (TGA) of the catalysts were performed to determine the influence of contact time and flow rate of HFC-134a. 2 mL/min of HFC-134a balanced with nitrogen to 25, 50, 100, and 200 mL/min total flow rates was studied at 600 C-o. 200 mL/min showed a 9.4 h catalyst lifetime with a small number of by-products. Shorter contact time between HFC-134a and HF with the catalyst was found to be the key to the longer lifetime of the catalyst. The catalyst lifetime was decreased with an increase in the HFC-134a input amount. Among 2, 4, and 6 mL/min input of HFC-134a, 2 mL/min showed the longest catalytic activity followed by 4 and 6 mL/min, respectively. Conversion of gamma-alumina into AlF3 and deposition of coke were responsible for the deactivation.