On The Simulation Of Thermally Coupled Catalytic Distillation Process For C₃Alkyne Selective Hydrogenation

Propylene, as a kind of basic material in modern petrochemical industry, plays animportant role in the national economy. Thermal cracking of hydrocarbons is themajor source of propylene production. The C3-cut stream typically containsmethylacetylene (MA) and propadiene (PD), which have to be removed. Selectivehydrogenation of the C3-cut is the established route for this. In this paper, theconfiguration of catalytic distillation column for C3selective hydrogenation wasproposed. While completing separation of C2and C3in dethanizer, MAPD containedin the C3-cut were hydrogenated selectively. This process had two advantages: theselectivity could be raised effectively in the distillation column; the liquid could usethe heat of hydrogenation for vaporization, then the duty of reboiler could be reduced.Simulation of this process was performed by using Aspen Plus software. As a result,the selectivity increased by13.8%. At the same time, duty of the reboiler was savedby9.91%. Another catalytic distillation coupling process, putting the catalyst into thepropylene column, was proposed. MAPD were separated from propylene in thepropylene column, and was converted into propylene at the same time by catalytichydrogenation. The simulation results showed that the selectivity of hydrogenationincreased by another34%.The conventional way in ethylene plant to separate cracking feedstock forobtaining propylene needs energy-and capital-intensive distillation process toseparate different cuts of different carbon numbers sequentially, so energy-saving isan important subject. By using the thermally coupled distillation configuration, thereversibility of the distillation process can be improved, and the energy consumptioncan be reduced. So a combination of a hydrogenation reactor and a separation unit inthe thermally coupled distillation (side rectifier) was proposed. Compared with theconventional process including dethanizer, hydrogenation reactor and propylenecolumn, propylene yield increased by0.74%, and the annual cost for refrigeration wassaved by2.44%.Then another process, the fully thermally coupled catalytic distillation for C3selective hydrogenation, was proposed. Compared with the conventional process including dethanizer, hydrogenation reactor and propylene column, propylene yieldincreased by0.46%, and the annual cost for refrigeration was saved by14.6%.