Research On Light-olefins-rich Syngas Preparation Via Cellulose Catalytic Pyrolysis

The high-speed-growing consumption of aviation fuel and external dependency are forcing China to find renewable solutions to safeguard the sustainable development of energy and strategic security. The vast greenhouse gas emission also puts China under the great international pressure. In China there are abundant reserves of lignocellulosic biomass, which is the only renewable resource that can be directly converted to hydrocarbon liquid fuels. Research and development of light olefins preparation via catalytic pyrolysis of lignocellulosic biomass coupled with olefins polymerization to synthetize aviation biofuel could be of great strategic significance to the establishment of a diversified energy system, to solve the energy structure restricting bottleneck, as well as to achieve the emission reducing targets in 2020 and the industrialized utilization of high-grade biomass energy.Relying on the Special Funds for Major State Basic Research Project of China (2013CB228100), a series of researches were conducted based on the technique route by which lignocellulosic biomass being catalytic pyrolyzed into light olefins. Cellulose was catalytically pyrolyzed to produce syngas rich in light olefins with a fixed bed reactor. The main researches and conclusions of this paper include:(1) Influence of reaction conditions on cellulose catalytic pyrolysis was investigated. Comprehensive experiments were carried out on a fixed bed reactor to investigate the impact of reaction parameters on the production yields of gases, liquids, solids, as well as light olefins yields and olefins distribution. The operating parameters included reaction temperature, carrier gas flow rate and mass ratio of catalysts to cellulose. The most light olefins mass yield was 5.5 wt.% and the corresponding carbon yield was 10.5 C-mol%, which was achieved at the optimal condition that reaction temperature was 650 ℃; nitrogen flow rate was 30 ml/min; and the mass ratio of catalysts to cellulose was 4.(2) Influence of catalyst characteristics on cellulose catalytic pyrolysis was researched. The HZSM-5 catalysts of various Si/Al ratio, as well as different amounts of Ce addition, were utilized to catalyze cellulose pyrolysis at the optimal reaction condition mentioned previously. The most light olefins mass yield was 6.8 wt.%, which was performed with the 3 wt.%Ce/HZSM-5 (Si/Al=25) and the corresponding carbon yield was 13.1 C-mol%.(3) Catalysts were characterized via the XRD, BET, NH3-TPD, and Py-FTIR methods. Loading Ce on the HZSM-5 catalysts could modify acid strength, acid sites distribution and shape selectivity, which would promote light olefins yields. The excessive loading Ce would cover on the catalyst acid sites, reducing olefins selectivly.(4) Mass and energy balances of light olefins preparation route via biomass catalysis pyrolysis were obtained. The evaluation results were compared with the current commercial product lines as well as emerging technologies for light olefins production. The mechanism of biomass catalytic pyrolysis for light olefins preparation was analysed, resulting into some reasonable advices for further enhancing the light olefins production.