Conversion of Butanes and Butenes from Industrial Feedstock over Zn-HZSM-5(acetate) Catalyst

The activity and selectivity of Zn/HZSM-5 (wt% 0, 77 ZnO) catalyst prepared by ion exchange with solution of zinc acetate in the aromatization of C-4/C-4(=) hydrocarbons was investigated. The experimental results showed that the conversion of C-4/C-4(=) hydrocarbons on the bifunctional Zn-HZSM-5 (acetate) catalyst and the selectivity to aromatics BTX are higher than that on monofunctional HZSM-5, but lower than on Zn/HZSM-5 (nitrate). On HZSM-5, protons (Bronsted acid sites) and on Zn-HZSM-5, both Zn cations and protons are responsible to alkanes dehydrogenation and further in dehydrocycloaromatization reactions that form C-6-C-8 aromatics. In the liquid product, on HZSM-5 catalyst at 450 degrees C and 8 atm., after 24h time on stream the aromatics represented an average of 30 wt%, with more xylenes and toluene. On Zn/HZSM-5 (acetate) catalyst, at 450 degrees C and 4 atm., after 176h time on stream, the aromatics represented more than 46 wt% with more toluene and aromatics C-8. The aromatization process is accompanied by the oligomerization of C-4/C-4(=) hydrocarbons (more C-9-C-10 and >C-10 aliphatic hydrocarbons) especially on HZSM-5 catalyst.