A series of NiMo/A12O3 catalysts containing boron and phosphorus Part I.: Synthesis and characterization

In this work, a series of nickel-molybdenum, nickel-molybdenum-boron and one nickel-molybdenum-phosphorus catalysts were prepared by incipient wetness impregnation method. Calcination temperature, nickel, molybdenum and boron concentrations in gamma-Al2O3 were varied from 450 to 600degreesC, 1.8 to 3.1 wt.%, 10.6 to 13.2 wt.% and 0.5 to 1.7 wt.%, respectively. Nickel-molybdenum-phosphorus catalyst was prepared using 2.7 wt.% phosphorus. All catalysts were thoroughly characterized. The catalyst containing 10.6 wt.% Mo and 2.4 wt.% Ni in gamma-Al2O3 gave maximum BET area of 211 m(2)/g. In these catalysts, the molybdenum oxides were present predominantly as polymolybdate and tetrahedral form. Addition of boron to NiMo/Al2O3 caused an increase in weak acid centers, whereas phosphorus caused the formation of acid centers with intermediate strength. Also, addition of boron caused the formation of crystalline B2O3 and MoO3 on the catalyst surface, evident from both XRD and SEM analyses. Whereas addition of phosphorus caused the formation of irregular particle size and agglomeration on the catalyst surface, evident from SEM-EDS analysis. New Lewis and Bronsted acid sites on the catalyst surface were observed from FTIR analysis because of the addition of boron and phosphorus to NiMo/Al2O3. (C) 2003 Elsevier B.V. All rights reserved.