Catalytic steam reforming of toluene: study of reaction parameters, reforming atmosphere and catalyst deactivation
File(s)
Author(s)
Zhu, Hualun
Type
Thesis
Abstract
Lignocellulosic biomass is widely recognized as an effective energy carrier capable of fulfilling the growing demand of clean and everlasting energy source for the sustainable development of the world. Biomass gasification is one of the most promising routes for conversion of biomass into gaseous fuel with tar issue. Among different tar removal methods, catalytic steam reforming is widely considered as one of the most promising and effective techniques for tar elimination in gasification. The main objectives of this work are to obtain a good understanding of the influence of main reforming parameters, reforming atmosphere and catalyst stability of catalytic toluene steam reforming.
A laboratory scale continuous fixed-bed reactor has been used in this project to study the reforming parameters including reforming temperature, steam to carbon (S/C) mole ratio, residence time, and simulated syngas atmosphere (CO, H2, CO2, CH4). Toluene was selected as a tar model compound due to its high content in tar, and it represents a stable aromatic structure. Biomass ash was introduced to the Ni/Al2O3 catalytic bed to improve its resistance to deactivation.
The main findings include: (1) 800 °C, gas hourly space velocity (GHSV) 61200 h-1 and S/C ratio 3 provide favourable operating conditions for steam reforming of toluene in order to get high toluene conversion (~92%) and hydrogen yield; (2) H2, even a small amount of CH4 present in the syngas could deactivate Ni/Al2O3 over time by increasing coke deposition; (3) H2, CO and CO2 content in the syngas have a strong influence on the selectivity of CO/CO2. (4) The introduction of biomass ash improved the stability and coke resistance of Ni/Al2O3 by acting as a mixture and a guard layer, two-layer biomass ash and Ni/Al2O3 catalytic system shows good carbon conversion (~90%) in different atmospheres in 5 hours.
A laboratory scale continuous fixed-bed reactor has been used in this project to study the reforming parameters including reforming temperature, steam to carbon (S/C) mole ratio, residence time, and simulated syngas atmosphere (CO, H2, CO2, CH4). Toluene was selected as a tar model compound due to its high content in tar, and it represents a stable aromatic structure. Biomass ash was introduced to the Ni/Al2O3 catalytic bed to improve its resistance to deactivation.
The main findings include: (1) 800 °C, gas hourly space velocity (GHSV) 61200 h-1 and S/C ratio 3 provide favourable operating conditions for steam reforming of toluene in order to get high toluene conversion (~92%) and hydrogen yield; (2) H2, even a small amount of CH4 present in the syngas could deactivate Ni/Al2O3 over time by increasing coke deposition; (3) H2, CO and CO2 content in the syngas have a strong influence on the selectivity of CO/CO2. (4) The introduction of biomass ash improved the stability and coke resistance of Ni/Al2O3 by acting as a mixture and a guard layer, two-layer biomass ash and Ni/Al2O3 catalytic system shows good carbon conversion (~90%) in different atmospheres in 5 hours.
Version
Open Access
Date Issued
2021-06
Date Awarded
2021-08
Copyright Statement
Creative Commons Attribution NonCommercial Licence
License URL
Advisor
Millan-Agorio, Marcos
Publisher Department
Chemical Engineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)