Aromatization of industrial feedstock mainly with butanes and butenes over HZSM-5 and Zn/HZSM-5 catalysts

The activity and selectivity in the aromatization of C4/C4 = hydrocarbons on Zn/HZSM-5 (wt% 1.39 Zn) prepared by ion exchange compared with that on HZSM-5 was investigated. The experimental results show that the conversion of hydrocarbons and the selectivity to aromatics BTX on the bifunctional Zn/HZSM- 5 catalyst are higher than that on monofunctional HZSM-5. On HZSM-5, protons (Bronsted acid sites) and on Zn/HZSM-5, both Zn cations and protons intervene in alkane dehydrogenation and further in dehydrocyclooligomerization reactions that form C6-C9 aromatics. In the liquid product, the aromatics represent an average value of 30 wt%, with more xylenes, on HZSM-5 catalyst after 24 h time on stream at 450 oC and 8 atm, and 70 wt% with more toluene, on Zn/HZSM-5 catalyst, after 52 h time on stream at 450 oC and atmospheric pressure. The aromatization process is accompanied by oligomerization (more C9-C10 and >C10 aliphatic hydrocarbons) especially on HZSM-5 catalyst.