Kinetics Study on Catalytic Degradation of Corn cob using CaO/γ Al2O3 Catalyst

Abstract

Biomass is the promising renewable energy sources which can be converted into liquid and gaseous fuels through various technologies. Thermochemical conversion of biomass is a common technology for the conversion of biomass into fuels .In this work, a thermo gravimetric analysis of Corn cob in the presence of CaO/ γ-Al2O3 catalyst is conducted. Pyrolysis experiments of corn cob with CaO/γ-Al2O3 catalyst with the main aim of development of the kinetic modeling for the catalytic decomposition process. The kinetics study of catalytic cracking of corn cob using CaO/γ Al2O3 catalyst was investigated over temperature range 25-800°C. The catalyst was prepared from Aluminum nitrate nonahydrate, urea, and CaCO3 using impregnation method followed by activation at 700°C for 4:30hr in the furnace. The catalyst was characterized with X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and Thermo gravimetric analysis (TGA) and Scanning electron microscopy (SEM). Thermal analysis was carried out for all samples using TGA in order to study the catalytic performance of all CaO/γ-Al2O3 on decomposition of corn cob in the process of pyrolysis. The obtained results were shown on TG and DTG graphs. The decomposition of all samples containing 0, 10, 20, 30, 40 and 50 wt% CaO/γ Al2O3 catalysts were compared to each other and to the reference sample (corn cob). The results showed best decomposition rate was observed when 10 wt% CaO loaded on γ-Al2O3 used as a catalyst. Kinetic models were investigated based on weight loss dependence to temperature in the pyrolysis process of corn cob with 10wt% CaO/γ-Al2O3 containing sample. The decomposition stage was divided into two different zones to attain the well-fitted reaction model with high coefficient of determination (R 2 ) using linear regressions. The activation energy (Ea) and correlation coefficient (R 2 ) profiles revealed that the kinetic parameters calculated using the Flynn–Wall–Ozawa and Kissinger–Akahira–Sunose method. The values from the Flynn–Wall– Ozawa methods were comparable, although gave higher R 2 values. The Eα values gradually reduced from 165.87kJ/mol to 129.186kJ/mol and 177.18 to 96.7kJ/mol with an increase in from 0.3 to 0.5 and 0.51 to 0.8 respectively. The model-fitting method of Coats–Redfern was used to predict the possible reaction mechanism, for which the F6.5 and F4 model resulted in comparable Eα values to those obtained from the Flynn–Wall– Ozawa method. The pre-exponential factors (lnA) were calculated based on the F6.5 and F4 reaction model and the Flynn–Wall–Ozawa method, and fell in the range of 17.6–13.26 min-1 and 17.63-8.95 min-1 with α increasing from 0.3 to 0.5 and 0.51-0.9 respectively. The study of the kinetic compensation effect confirmed that a compensation effect existed between Ea and lnA during the corn cob pyrolysis. Results obtained in this thesis may be the base for wide range of scientific studies in the future to examine the catalytic degradation nature of 10 wt% CaO/γ-Al2O3 and further analysis of catalysts obtained in this work in the synthesis of bio-oil from corn cob and different biomass feedstock