Liquid-Vapor Phase Equilibria in Binary and Ternary Subsystems Constituted by Pyrocondensate Components from the Pyrolysis of Straight-Run Naphtha

Abstract

Liquid3vapor equilibrium in the binary subsystems of the ethylbenzene3o-xylene3a-methylstyrene3p-vinyltoluene3dicyclopentadiene3indene system was predicted using UNIFAC group model and studied experimentally. To assess the reliability of parameters, the liquid3vapor equilibrium was studied experimentally in the ternary systems and compared with the calculated data.Petroleum polymeric resins (PPRs) are widely used as a rosin substitute and in production of paintwork materials, wooden fiberboards, adhesive solutions, and anticorrosive coatings. Waste and side products of petroleum-chemical production, and, first of all, liquid products of hydrocarbon pyrolysis are the raw materials for PPR production [1].Unsaturated reactive hydrocarbons are the resinforming components. Their content in the raw material should be no less than 30%. In addition, it may contain admixtures decreasing the quality of the polymers synthesized, which makes necessary appropriate pretreatment of the raw material.The requirements to the raw material are determined by the properties of PPR formed, polymerization conditions, and catalytic systems used, which allows selection of the method of the raw material preparation. As a rule, distillation is used to separate pyrocondensate components.Ethylene and propylene monomers are gaseous products of the pyrolysis of hydrocarbon raw material, in particular, straight-run naphtha. The residual (after ethylene or propylene separation) pyrocondensate contains a lot of components with unsaturated bonds, namely, styrene, a-and b-methylstyrenes, vinyltoluenes, allylbenzene, dicyclopentadiene, indene, and indan in a mixture with such solvents as toluene, xylene, ethylbenzene, propylbenzene, and cumene. High-molecular-weight resinous products can also be present. This pyrocondensate can be used to prepare PPRs (which are the components of varnishes and paints) after removal of solvents, dicyclopentadiene (DCPD), and tars.Although DCPD is unsaturated hydrocarbon and hence a resin-forming component, its presence in the raw-material is undesirable. The point is that powdered aluminum chloride used as a catalytic system polymerizes DCPD to form insoluble in PPR cross-linked polymers, which is inadmissible. High content of DCPD favors formation of the intensely colored polymerizate, which is also undesirable.With regard to the above facts, the raw material preparation includes distillation of highly resinous liquid products of the pyrolysis of straight-run naphtha with high content of oligomers and monomers.To develop the process for distillation separation of the pyrocondensate, we have analyzed the known properties of substances comprising PPR [2, 3]. Many components of the mixture to be separated have close boiling point, which makes it impossible to solve the task by the elementary distillation. The mixture contains thermolabile components, capable of polymerization, which requires addition of polymerization inhibitors and reduced pressure in the distillation column.Preliminarily, we reduced the dimension of t...