Hydrodenitrogenation of vacuum residue with a large-pore catalyst

Abstract

The improved conversion (e.g. nitrogen conversion) achieved with laboratory-prepared macropore (MAP) catalysts could be attributed to either geometrical effects (diffusion or access to surface area) or chemical effects (surface acidity or more effective reaction sites). The MAP catalysts had much larger macropores than a commercial reference catalyst. Because these pores provided access to the catalysts' interior, the 15% MAP catalyst had a larger surface area than the commercial catalyst, when the catalysts were in their working conditions. Infrared spectroscopic measurements of ammonia and pyridine adsorption were made on several of the catalysts to determine whether or not the acidic properties of the MAP alumina were different from those of γ-alumina. A unimodal catalyst containing fluoride ions that enhanced its surface acidity and thereby enhanced conversions was compared with the MAP catalyst. Both the F-containing catalyst and the MAP catalyst produced greater nitrogen conversions than the unimodal catalyst that did not contain F ions. When the infrared spectra of the MAP catalyst were compared with those of the F catalyst, it was seen that at 400°C the F catalyst retained Brönsted acidity that was not observed in the MAP catalyst. Therefore, Brönsted acidity was not considered to be the cause of the conversion enhancement achieved with the MAP catalyst. On this basis, the enhanced conversion by the MAP catalysts was attributed to geometrical effects (pore diffusion).