Thiophene hydrodesulfurization on sulfided Ni, W and NiW/USY zeolite catalysts: effect of the preparation method

The effect of the preparation method and metal loading on the hydrodesulfur ization (HDS) of thiophene, and on the dispersion and location of Ni and/or W species in Ni, W and NiW sulfides supported on USY zeolite, was investig ated by temperature-programmed reduction (TPR), X-ray photoelectron spectro scopy, N-2 adsorption and acidity determination. The monometallic Ni cataly st prepared by ion exchange [Ni (int)] exhibited higher initial HDS activit y than those prepared by impregnation [Ni (imp)] and by ion exchange and su bsequent formation of small NiO clusters by NaOH treatment [Ni (clus)]. For the binary NiW catalyst series with different metal contents, the catalyst s prepared by impregnating W onto the Ni (int) one showed activities compar able to those of the catalysts prepared by impregnating Ni onto the W/USY s ample. These catalyst series showed much higher activities than those prepa red by impregnating W onto the Ni (clus). The characterization results reve aled that catalysts displayed significant differences in dispersion, locati on and sulfidation of the Ni and W phases dependent on the preparation meth od. However, none of these factors alone accounted for the activity trend. In general, it was found that a combination of high acidity and metal dispe rsion led to catalysts with high initial HDS activity. (C) 2000 Elsevier Sc ience B.V. All rights reserved.