Asphaltene and resid pyrolysis. 2. The effect of reaction environment on pathways and selectivities

Pyrolysis experiments with resids and isolated asphaltenes from Arabian Lig ht and Arabian Heavy feedstocks were compared with previous experiments wit h Hondo and Maya feeds to determine the effect of reaction environment on r eaction paths, kinetics, and mechanisms. The experiments were at temperatur es of 400, 425, and 450 degreesC for holding times ranging from 20 to 180 m in in microbatch reactors. Reaction products were recovered as gas, maltene , asphaltene, and coke lumps. The maltene, asphaltene, and coke product fra ctions were collected by a solvent extraction sequence where heptane-solubl e material was defined as maltene, toluene-soluble material as asphaltene, and toluene-insoluble material as coke. Gas chromatography revealed the pre sence of C-1-C-5 paraffins, C-2-C-5 olefins, isoparaffins, H2S, and CO2. Re sults were summarized by a lumped reaction network that allowed for quantit ative kinetics analysis. Comparison of relative kinetics and apparent activ ation energies yielded insight into thermal reaction pathways, feedstock ef fects, and-asphaltene environment effects. At 400 and 425 degreesC, isolate d asphaltene reacted selectively to maltene. At 450 degreesC, asphaltene re acted predominately to coke. Isolated maltene pyrolysis indicated that asph altene and coke formed in series, i.e., maltene --> asphaltene --> coke.