Prereforming of n-tetradecane over Ce-promoted 50 wt% Ni/MgO-Al₂O₃ catalyst with high coke resistance

The effect of Ce-promotion on 50 wt% Ni-based catalysts during the prereforming of n-tetradecane and its optimum content were investigated. The Ni catalyst was synthesized by deposition-precipitation method. Next, various amounts of Ce (0-13 wt%) were loaded on the Ni catalyst by impregnation. The characteristics of the prepared catalysts were analyzed by XRD, H₂-TPR, BET, BJH, and H₂-chemisorption analyses. The prepared catalysts were tested under the prereforming conditions (temperature = 400 °C, GHSV = 3000 h^-1, and S/C = 3 and 4). The Ni catalyst was easily deactivated under the following conditions: temperature = 400 °C, GHSV = 3000 h^-1, and S/C = 4. The stability of all Ce-promoted Ni catalysts was improved as compared to that of the Ni catalyst. Among the Ce-promoted catalysts, 5 wt% Ce/50 wt% Ni/MgO-Al₂O₃ catalyst showed excellent stability even under the severe condition of S/C = 3. SEM, TEM, and TG analyses were performed in order to identify the main factor responsible for the rapid deactivation of the Ni catalyst. In the case of 0Ce/50Ni, Ni particles were encapsulated by many folds of coke and it was related to the rapid catalyst deactivation. However, after Ce promoted on the Ni catalyst, the thickness of the coke layers and the number of encapsulated Ni particles decreased and the deposited amount of coke on the catalyst also decreased.