Abstract
La2O3 promoted Ni/gamma-Al2O3 fluidizable catalysts are studied for the steam gasification of a cellulose surrogate (glucose) and a lignin surrogate (2-methoxy-4-methylphenol) in a CREC Riser Simulator. Two gamma-Al2O3 are considered as the support for an active and stable Ni catalyst. La2O3 modified supports and catalysts are characterized using BET specific surface area, XRD, TPR, TPO, and H-2-pulse chemisorption. Pyridine FTIR, NH3-TPD and CO2-TPD are employed to establish the effect of La2O3 on the aciditiy-basicity of the alumina used. It is shown that increasing the La2O3 up to 5 wt% improves the BET surface area and the CO2 adsorption capacity, as well as reduces support acidity. XRD results revealed the formation of undesirable LaAlO3 on the Ni catalyst containing 10 wt% La2O3. The 10 wt% La2O3 also favors the formation of larger Ni crystallites which are susceptible to coking. In agreement with this, the catalyst containing 10 wt% La2O3 gives lower dry gas yields and carbon conversions, as well as yields higher coking than the catalyst supported on alumina with 5 wt% La2O3. On the other hand, catalysts supported on Sasol gamma-Al2O3 display higher surface area, Ni reducibility and dispersion, and CO2 adsorption capacity than the Alcan gamma-Al2O3 supported catalysts. The addition of 5 wt% La2O3 further enhances both the structural properties and the reactivity of Ni/Sasol gamma-Al2O3 catalyst. In particular, catalytic gasification using 20% Ni on a 5% La2O3-Sasol gamma-Al2O3 catalyst shows promising glucose and 2-methoxy-4-methylphenol conversions to a high-quality synthesis gas at only 650 degrees C. This catalyst yields a 95% carbon conversion of glucose to permanent gases with no tar formation and negligible coke deposition; whereas a 81% carbon conversion with only 10.5 wt% tars is achieved from 2-methoxy-4-methylphenol gasification. (C) 2014 Elsevier B.V. All rights reserved.