Diesel steam reforming: Comparison of two nickel aluminate catalysts prepared by wet-impregnation and co-precipitation

gamma-Al2O3 supported Ni-Al spinel catalysts, prepared by co-precipitation and wet impregnation, were produced, analysed and tested on commercial diesel steam reforming. The study of the preparation method's effect on the catalytic activity, builds on a previously patented Ni-Al spinel (NiAl2O4) catalyst supported on alumina (Al2O3) and yttria-stabilized zirconia (YSZ). This non-noble metal-based NiAl2O4/Al2O3-YSZ catalyst demonstrated high activity for commercial diesel and biodiesel steam reforming.Diesel steam reforming experiments were performed in a fixed-bed reactor setup, with a proprietary diesel-water emulsion mixture at 760 degrees C. The two tested catalytic formulations yielded the same overall conversion while the products obtained were significantly different. Thus, the catalyst produced via the co-precipitation method (Copr) (a) suffered rapid deactivation from carbon deposition; (b) produced 5 times more methane than the catalyst produced via the wet impregnation method (Impr) and (c) showed a decreasing hydrogen production. The Impr catalyst exhibited a higher stability for diesel steam reforming with no signs of carbon formation or activity loss. The difference between Impr and Copr catalyst activities is related to the Ni-aluminates dispersion: located on the surface for the Impr catalyst, whereas located in the bulk of the Copr catalyst.In order to correlate their activities to their physicochemical properties, both new catalytic formulations presented in this work were characterized before and after steam reforming tests, using scanning electron microscopy (SEM), X-ray diffraction (XRD) as well as temperature programmed reduction (TPR). (C) 2012 Elsevier B. V. All rights reserved.

通过共沉淀法和湿法浸渍法制备了γ - Al₂O₃负载的Ni - Al尖晶石催化剂，并对其进行了制备、分析以及在商业柴油蒸汽重整反应中的测试。对制备方法对催化活性影响的研究是建立在先前已获专利的负载于氧化铝（Al₂O₃）和氧化钇稳定的氧化锆（YSZ）上的Ni - Al尖晶石（NiAl₂O₄）催化剂的基础之上。这种基于非贵金属的NiAl₂O₄/Al₂O₃ - YSZ催化剂在商业柴油和生物柴油蒸汽重整反应中表现出高活性。柴油蒸汽重整实验是在固定床反应器装置中进行的，采用一种专有的柴油 - 水乳化混合物，温度为760℃。两种经过测试的催化剂配方总体转化率相同，但所得产物却有显著差异。因此，通过共沉淀法（Copr）制备的催化剂（a）因积碳而迅速失活；（b）产生的甲烷量是通过湿法浸渍法（Impr）制备的催化剂的5倍；（c）氢气产量下降。Impr催化剂在柴油蒸汽重整反应中表现出更高的稳定性，没有积碳或活性损失的迹象。Impr和Copr催化剂活性的差异与镍铝酸盐的分散有关：Impr催化剂的镍铝酸盐位于表面，而Copr催化剂的镍铝酸盐位于体相。为了将它们的活性与其物理化学性质相关联，本研究中提出的两种新型催化剂配方在蒸汽重整测试前后均使用扫描电子显微镜（SEM）、X射线衍射（XRD）以及程序升温还原（TPR）进行了表征。（C）2012爱思唯尔B.V. 保留所有权利。