Petroleum resins: Separation, character, and role in petroleum

In petroleum science, the term resin generally implies material that has be en eluted from various solid adsorbents, whereas the term maltenes (or petr olenes) indicates a mixture of the resins and oils obtained as filtrates fr om the asphaltene precipitation. Thus, after the asphaltenes are precipitat ed, adsorbents are added to the n-pentane solutions of the resins and oils, by which process the resins are adsorbed and subsequently recovered by the use of a more polar solvent, and the oils remain in solution. The resin fr action plays an important role in the stability of petroleum and prevents s eparation of the asphaltene constituents as a separate phase. Indeed, the a bsence of the resin fraction (produced by a variety of methods) from the ma ltenes influences the ability of the de-resined maltenes to accommodate the asphaltenes either in solution or as a stable part of a colloidal system. In spite of the fact that the resin fraction is extremely important to the stability of petroleum, there is surprisingly little work reported on the c haracteristics of the resins. This article summarizes the work that has bee n carried out in determining the character and properties of the resin cons tituents. Suggestions are also made regarding current thoughts of the role of these constituents on the structure and stability of petroleum.