| Para xylene is a valuable aromatic compound, because of the demand for oxidation to form tetraphthalic acid, a feed stock for polyester resin and fibers. A relatively high cost is associated with obtaining it in 99+% purity. Purification of para xylene requires separation from three close boiling C8 aromatics i.e. m-xylene, o-xylene, and ethylbenzene and subsequent isomerization of the remaining ortho and meta xylene isomers to an equilibrium mixture. The removal of ethylbenzene is another source of complication.;To study the effect of acid sites in pentasil-type catalyst on the toluene alkylation, and para xylene selectivity, four catalysts with different cations in the frame work were synthesized. These catalyst were synthesized to have a SiO;The effect of temperature, residence time, and feed composition on alkylation of toluene with methanol over these catalysts were studied. The AlZSM-5 produced a xylene composition comparable to the equilibrium composition. Alkylation of toluene with methanol over BZSM-5, FeZSM-5, and LaZSM-5 produce xylene composition different than the equilibrium one. The LaZSM-5 catalyst produced the highest para xylene selectivity. The para xylene composition in the xylene isomers was as high as 92%. The p-xylene isomerization over AlZSM-5, and LaZSM catalysts, indicate that the minimization of the isomerization reaction is the cause of the high para selectivity.;All of the catalysts used in this investigation showed relatively rapid deactivation. The cause of the catalyst deactivation is the coke formation inside of the catalyst pores. |
