Kinetic analysis of vacuum residue hydrocracking in early reaction stages

Abstract

In this work, a lumped kinetic model for the hydrocracking of vacuum residue (VR) from Maya crude oil was developed. A preliminary kinetic analysis based on the conversion of VR was performed. Next, ten models with increasing level of complexity were proposed and solved sequentially using Matlab® software. All models included four lumps: products with boiling point >450°C (L+), products with boiling point <450°C (L−), gas and coke. Kinetic parameters were estimated from the experimental data obtained in a microbomb batch reactor at three temperatures (400, 425 and 450°C) and four holding times (10, 30, 60 and 90min). Two catalysts, NiMo/Al2O3 and NiMo/Al2O3–Cr (alumina doped with chromium), were tested. Kinetic results showed that gas was mainly produced from the decomposition of L− at low temperatures, whereas at 450°C gas is predominantly formed from cracking of L+. Moreover, coke was found to be exclusively produced from L+ at all temperatures. In general, NiMo/Al2O3 gave rise to higher yields of L− than NiMo/Al2O3-Cr. Nevertheless, NiMo/Al2O3-Cr was able to retain greater activity at higher temperatures.