Abstract
Pyrolysis gasoline upgrading by hydrogenation and ring opening was investigated over highly loaded Ni catalysts supported on amorphous silica–alumina and incorporating promoters as Pd, seeking a higher aromatic reduction of this feedstock in order to meet stringent fuel regulations. The effect of Ni loading and Pd component on the activity of those systems was evaluated in a fixed bed reactor under the following operating conditions:
T
=
573 and 673
K, H
2:PyGas molar ratio
=
10,
P
=
5.0
MPa, WHSV
=
4
h
−1. The catalyst properties, measured by several characterization techniques (ICP-AES, XRD, N
2 adsorption–desorption isotherms, TPR, H
2-TPD, CO chemisorption, XPS, FTIR spectroscopy of adsorbed pyridine and NH
3-TPD), were related to their catalytic activity and selectivity. Interestingly, the increase in Ni loading from 24.4 to 33.2 Ni wt.% has a negative effect on both hydrogenation and ring opening activities, as it causes a drop in the BET surface area and a decrease in metal-support interaction, with a negative bearing on catalyst stability. On the other hand, the addition of Pd has a positive effect for hydrogenation, linked with the higher electronegativity of Pd
0 species compared to those of Ni
0, as well as with a greater stability of Pd-promoted catalysts during on-stream conditions. A linear correlation has been found between the total amount of desorbed H
2, as determined from H
2-TPD experiments on freshly reduced catalysts, and the initial turnover frequency.