Enhanced Catalytic Pyrolysis of Biomass for High-Quality Biofuel Production
Time: Fri 2021-04-23 10.00
Doctoral student: Devy Kartika Ratnasari , Materialvetenskap
Opponent: Professor Tobias Richards, University of Borås
Supervisor: Docent Weihong Yang, Materialvetenskap, Tillämpad termodynamik och kylteknik; Professor Pär Jönsson, Processer
The rapid increase in energy demand, the extensive use of fossil fuels, and the urgent need to reduce carbon dioxide emissions have raised concerns in the transportation sector, since transportation has been primarily dependent on fossil fuels. Biofuel from biomass can make significant contributions to overcome the expected depletion of fossil fuels and reduce carbon emissions. The availability and wide diversity of biomass resources have made them an attractive and promising source of fuels. Biomass can be converted into biofuel by thermochemical pyrolysis process. Improvements on the pyrolysis process of biomass fuels are needed to obtain a high-quality of bio-oil. Pre-treatment by acid leaching prior to the pyrolysis process is considered to remove Alkali and Alkaline Earth Metal (AAEM) from the biomass, since AAEM adversely affect the catalytic pyrolysis process. Information about biomass pyrolysis kinetics is also important to evaluate biomass as a feedstock for fuel or chemical production as well as efficient design and control of thermochemical processes. Further, the use of H-ZSM-5 and Al-MCM-41 as a mesoporous and a microporous catalyst has been proved to improve the quality of bio-oil. The influence of a catalyst regeneration on the chemical composition of the upgraded oil is also one of the factors pertaining to the catalytic process.In this study, the catalytic pyrolysis kinetics of lignocellulose biomass with a mixed catalyst of H-ZSM-5 and Al-MCM-41 at different ratios for both, un-leached and leached biomass, is analyzed. The derived activation energies are determined based on the solid-state reaction mechanism. Bench-scale experiments have also been investigated to improve the quality of bio-oil, in terms of Organic Fraction (OF), water content, acidity, favorable fractions, as well as gasoline-range chemicals. The effect of a mixed-catalysts and staged-catalysts consisting of H-ZSM-5 and Al-MCM-41 at different ratios in a lignocellulose biomass pyrolysis has been compared. The ratio of H-ZSM-5 and Al-MCM-41 in the catalyst mixtures for lignocellulose biomass catalytic pyrolysis has also been optimized. Further, the effect of sequential catalyst regenerations of H-ZSM-5 and Al-MCM-41 catalyst mixtures on the obtained catalytic pyrolysis products has been analysed.The bench-scale experiments of lignocellulosic biomass pyrolysis and catalytic pyrolysis were performed using a fixed bed reactor equipped with oil condensers and a gas collection sample bag. The quality of bio-oil produced from the thermal pyrolysis of lignocellulosic biomass, catalytic pyrolysis with single catalyst, catalytic pyrolysis with staged catalyst system, as well as catalytic pyrolysis with mixed catalyst system were studied. Later, the catalyst was regenerated several times and the regenerated catalyst was reloaded in the reactor to proceed with the next run. The composition of the derived upgraded pyrolysis oils in relation to the catalyst regeneration was determined.The results from the acid leaching treatment showed that the optimum leaching process was set to 30 minutes, 30°C and 5 wt.% acetic acid in the leaching liquid. This resulted in 59%, 95%, 99%, and 96% reduction degree of Calcium (Ca), Magnesium (Mg), Potassium or Kalium (K), and Natrium (Na), respectively. The use of the acid leaching process as a treatment prior to catalytic pyrolysis is positive, since it resulted in high devolatilization and reaction rate. For the kinetic studies, the second order (F2) mechanism was able to illustrate the catalytic pyrolysis process, proven by the result that the coefficient of determination (R2) was higher than 0.99, which was high compared to other mechanisms.The bench-scale experiments show that that Al-MCM-41 with H-ZSM-5 in the staged catalyst system enhanced the production of favorable compounds: hydrocarbons, phenols, furans, and alcohols. The favorable compounds yield that boosted 5.25-6.43% of that with single H-ZSM-5 catalyst was produced with H-ZSM-5:Al-MCM-41 mass ratio of 3:1 and 7:1. The pyrolysis and catalysis temperature of 500°C with H-ZSM-5:Al-MCM-41 ratio of 3:1 obtained the optimum quality of bio-oil with 11.08 wt.% of Organic Fraction (OF), 76.20% of favorable fractions, 41.97 wt.% of water content, low TAN of 43.01 mg-KOH/g, high deoxygenation, as well as high gasoline-range production of 97.89%.The catalyst mixture of H-ZSM-5 and Al-MCM-41 with a ratio of 7:1 resulted in a 65.75% deoxygenation degree. An organic-rich bio-oil was obtained with 74.90 wt.% of carbon content, 8 wt.% of hydrogen content, 15 wt.% oxygen content, a 0.39 wt.% water content, and a high heating value of 34.15 MJ/kg. The highest amount of favorable compounds among the studied catalytic experiments was obtained with a value of 95.89%. The significant improvement in the quality of bio-oil with the utilisation of H-ZSM-5 and Al-MCM-41 catalyst mixtures was the rise of favorable compounds in bio-oil.The experiments of sequential catalyst regenerations of H-ZSM-5 and Al-MCM-41 catalyst mixtures show that the catalytic activity decreased as the number of reaction cycles increased, albeit an increase yield of Organic Fraction (OF) and a decrease in water as well as coke yields. The HHV of bio-oils decreased. However, the minimum value of HHV (22.42 MJ/kg) after 6 sequential usage was still higher than the value for the non-catalytic experiment (19.55 MJ/kg). The favorable compounds yield, which includes hydrocarbons, phenols, furans, and alcohol, decreased. The dominant components contributed to the yield of favorable compounds were hydrocarbon aromatics and phenols.