Reactivity of Cold Lake asphaltenes

Experimental evidence have been presented which supports the concept that Cold Lake asphaltenes have somewhat large, hydrogen-deficient core structures to which are attached alkyl side chains and highly substituted aromatic groups. Sulfur tends to be relatively evenly distributed between the core structure and the peripheral groups and nitrogen is concentrated predominantly in the core. The overall picture of asphaltene reactivity that has emerged from this is shown schematically in Figure 10. During mild hydroconversion, weaker linkages are thermally broken resulting in the formation of maltenes having a higher (H/C) and reacted asphaltenes having a lower (H/C). Some alkyl side chains are also lost predominantly by ..beta..-scission. In the absence of effective hydrogen transfer, some of these reaction fragments can recombine to form coke. With improved hydrogen transfer the coking reactions can be significantly delayed. Total conversion of asphaltenes to maltenes would at this point seem to be an improbable goal; however, more research is needed in order to see how far the structural concepts developed here for Cold Lake asphaltenes can be generalized to others.