A study on catalytic pyrolysis of biomass with Y-zeolite based FCC catalyst using response surface methodology

Abstract

A response surface methodology (RSM) was used to investigate the influence of temperature, weight hourly space velocity (WHSV) and vapor residence time on the catalytic pyrolysis of hybrid poplar wood using Y-zeolite based FCC catalyst in a 50mm bubbling fluidized bed reactor. The levels of the independent variables were: temperature (400–600°C), WHSV (1–3h−1), and vapor residence time (3–6s). The Box–Behnken experimental design was used and a total number of 15 experimental runs including 3 center runs were generated. The analysis of variance (ANOVA) at 95% confidence interval was performed with Minitab 16 software package and reduced models were generated for the prediction of the responses. It was found that higher levels of WHSV (>1h−1) with shorter vapor residence time and moderate temperatures (⩽500°C) favor higher yield of organic liquid fraction. Also, higher temperature (>500°C) and WHSV (>2h−1) reduces the formation of coke/char. The catalytic pyrolysis with the Y-zeolite based FCC catalysts at high temperatures (>500°C) and long residence time enhanced the cracking of the primary vapors and increased the formation of CO, H2 and CH4. The catalytic process at higher temperatures (>500°C) and lower WHSV (⩽2h−1) decreased the oxygen content and increased the viscosity of the bio-oil. The reaction temperature was the most significant independent variable on char/coke yield, concentration of non-condensable gases, carbon content, oxygen content, pH and viscosity of the bio-oils. The WHSV was found to be the most important significant independent variable that affected the yield of organic liquid and the formation of water. The models for the prediction of the responses with the exception of viscosity were adequate and statistically significant.