A Model of Catalytic Cracking: Catalyst Deactivation Induced by Feedstock and Process Variables

Abstract

Changes in the quality of the feedstocks generated by involving various petroleum fractions in catalytic cracking significantly affect catalyst deactivation, which stems from coke formed on the catalyst surface. By conducting experimental studies on feedstocks and catalysts, as well as using industrial data, we studied how the content of saturates, aromatics and resins (SAR) in feedstock and the main process variables, including temperature, consumptions of the feedstock, catalyst and slops, influence the formation of catalytic coke. We also determined catalyst deactivation patterns using TG-DTA, N2 adsorption and TPD, which were further used as a basis for a kinetic model of catalytic cracking. This model helps predict the changes in reactions rates caused by coke formation and, also, evaluates quantitatively how group characteristics of the feedstock, the catalyst-to-oil ratio and slop flow influence the coke content on the catalyst and the degree of catalyst deactivation. We defined that a total loss of acidity changes from 8.6 to 30.4 wt% for spent catalysts, and this depends on SAR content in feedstock and process variables. The results show that despite enriching the feedstock by saturates, the highest coke yields (4.6–5.2 wt%) may be produced due to the high content of resins (2.1–3.5 wt%).

Hydrocracking of crude palm oil to a biofuel using zirconium nitride and zirconium phosphide-modified bentonite

“…Likewise, the bentonite-ZrP revealed a decrease in the catalyst activity up to 1.12%, which produced 84.93% conversion and moderately decreased to 84.02% at four consecutive runs. The decrease in the conversion at four consecutive runs was presumably due to the deactivation of the catalyst through the undesired coke formation 84 The catalyst's surface was covered by coke and clogged the catalyst's active site. 85 Under these conditions, the reactant and catalyst sites had limited accessibility, which inhibited the hydrocracking reaction's effectiveness, 86 thereby reducing the CPO conversion.…”

Hydrocracking optimization of palm oil to bio-gasoline and bio-aviation fuels using molybdenum nitride-bentonite catalyst

“…Similar trend was also reported by other reports. 92 The formation of coke was undesired since it could inhibit the hydrocracking process. 71 Coke had the capability of covering the catalyst surface and clogging the acid sites of the catalyst.…”

Experience in Processing Alternative Crude Oils to Replace Design Oil in the Refinery

“…To improve profitability, refineries are trying to process blends resembling in their properties the design crude, which contain one or more cheaper crudes (opportunity crudes) [11]. The processing of petroleum mixtures can be accompanied by operational problems related to accelerated fouling [12][13][14], corrosion [15][16][17][18][19][20], equipment failure [21], catalyst deactivation [22][23][24], etc. Thus, the assumption that a refinery can refine economically favourable, environmentally friendly, and reliable petroleum crude blends whose characteristics are not too far away from the designed crude may be misleading [25].…”