ASPHALT FLOCCULATION AND DEPOSITION .1. THE ONSET OF PRECIPITATION

Formation of asphalt aggregates and their deposition on the pore surfa ces of a porous medium, which alter the structure of the medium and it s effective properties, is a critical problem to catalytic and oil rec overy and refinery processes. Extensive new experimental data for the amount of precipitated asphalt formed with crude oil and various solve nts are presented. Results indicate that, contrary to the previous ass umptions asphalt formation is at best partially reversible. A thermody namic model based on the Flory - Huggins theory of polymer solutions i s used together with the Soave equation of state, to pr edict the data . Critical evaluation of the model shows that its predictions do not a gree well with our data. As an alternative, we propose a new model tha t employs a scaling equation, somewhat similar to those encountered in aggregation and gelation phenomena. The scaling function takes on a v ery simple form, and its predictions are in very good agreement with t he data. It also predicts that the onset of precipitation may obey a s imple universal equation.