Deactivation of Ni–Mo/Al2O3 catalysts aged in a commercial reactor during the hydrotreating of deasphalted vacuum residuum

Abstract

A series of Ni-Mo/Al 2 O 3 catalysts for the hydrotreating of deasphalted vacuum bottoms has been investigated as fresh catalysts and after aging in an industrial reactor during a typical commercial run. Several structural parameters have been varied in the catalyst series. In particular, pore size, surface area, active metal loading and pellet size were changed to investigate the role of kinetic and diffusional phenomena present in this process. The samples were placed in different locations along the industrial reactor allowing for a comparative analysis of the different samples under varying environments, since along the reactor, quality, temperature, and H 2 partial pressure continuously change.Fresh and aged samples were analyzed by a variety of techniques, which include atomic adsorption, scanning electron microscopy, X-ray microanalysis, BET, thermogravimetry and temperature-programmed oxidation. In addition, a laboratory trickle-bed reactor was used to compare the catalytic activity of fresh samples with the residual activity retained by the aged samples after the commercial run.These catalysts deactivate by accumulation of metals and, to a lesser extent, coke deposition. These effects are governed by a competition of kinetic and diffusional phenomena. The kinetic phenomena, which involve adsorption and decomposition of metal-bearing compounds are mainly related to the active metal content and overall surface area of the catalyst, while the diffusion of the molecules inside the pellet are controlled by pore size distribution and pellet size. The current contribution shows how this type of comparative study can be used to identify the most appropriate catalyst configuration for a given set of reaction conditions and feedstock quality.

Catalyst deactivation pattern along a residue hydrotreating bench-scale reactor

“…Metal and coke deposition show contrary trends; while the former is high at the beginning and then it decays, the latter starts low and then it rises, consistently with profiles previously reported [1,2,29,31,32,34]. Both hard and soft coke amounts also increase toward the bed outlet, although the soft/hard ratio seems constant through the entire bed.…”

“…Several studies on deactivation by metals and coke in hydroprocessing catalysts have been reported [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28]. Nonetheless, only few studies on deactivation pattern along residue hydrotreating bench-scale reactor have been published [29][30][31][32]. In this paper, the catalyst deactivation of the first stage of a hydrotreating bench-scale reactor is analyzed.…”

Effect of pore size distribution (PSD) of Ni-Mo/Al2O3 catalysts on the Saudi Arabia vacuum residuum hydrodemetallization (HDM)

“…Pore volume loss data in Table 3 indicate that the volume of pore in <10 nm size and pores in 10-20 nm size are easily affected while the macro pore volume changes little [37][38][39], resulting in a larger average pore diameter of spent catalysts compared to the fresh ones [23,40]. Isaza et al reported that small pores were blocked and some of large pores were partially blocked under the reaction conditions [15]. The PSD of regenerated catalyst A0 and A7 in Fig.…”

“…Referring to the parameters that impact on the HDM activity, many factors may be considered such as the chemical characteristics of the feed, the pore structure, active metal loading, surface area and pellet size of the catalyst, as well as the position along the packed-bed reactor [15]. In our study, we use the same feedstock, the same active metal loading on different catalysts and the same pellet size of catalysts.…”

“…Recently, residuum hydrotreating becomes an efficient way to process the heavy oil. However, the costs of residuum hydroprocessing necessarily increase due to the higher H 2 pressures required and the more rapidly deactivated catalyst [8][9][10][11][12][13], especially the HDM catalyst which is plugged by the coke deposition and the accumulation of metals [14][15][16][17]. Several methods have been suggested for alleviating the short catalyst life and high operating cost expected * Corresponding author.…”