Catalytic conversion of heavy naphtha to reformate over the phosphorus-ZSM-5 catalyst at a lower reforming temperature

Naphtha reforming to aromatics, naphthenes, and iso-paraffins is an essential process to increase the octane number of gasoline through the utilization of middle naphtha (whole). A ZSM-5 zeolite catalyst with modified medium pores was developed to comprehend the existing limitation of catalytic reforming to the unutilized refinery feedstock of heavy naphtha. The study applied a lower reforming conversion temperature (350 degrees C) than a conventional reformer without noble metal addition in an effort to lower the carbon footprint of the process and catalyst cost. The modified zeolite catalyst was impregnated with phosphorus oxide and spray-dried, followed by a hydrothermal treatment with steam. The parent and modified catalysts were characterized by NH3-TPD, SEM, XRD, NMR, FTIR, and N-2 physisorption. Steam treatment was conducted to reduce the original zeolite acidity, mainly in the form of Bronsted acid sites, which resulted in the formation of phosphorus-aluminum species in the framework. The modified catalyst consisting of 40% ZSM-5 and 60% binder delivered high conversion of dodecane, and the reforming reaction selectivity favored the formation of carbonium ions through beta-scission. Therefore, monomolecular cracking took place, resulting in the production of olefins and paraffin alongside iso-paraffins, aromatics, and naphthenes, which are associated with the bimolecular pathway. The reforming of heavy naphtha was different; the free radicals from beta-scission were affected by the surrounding molecules of feedstock, and the bimolecular reactions were more dominant through zeolite pores. The study demonstrated that the addition of 10% steam during the reaction of heavy naphtha suppressed coke formation. Furthermore, high conversion and steady selectivity were maintained during the reaction, which resulted in gasoline reformate with a high research octane number (RON).

Automated summary

The study focuses on reforming heavy naphtha to increase gasoline octane number. A modified ZSM-5 zeolite catalyst with steam treatment was developed to improve the conversion and selectivity of the reaction. The addition of steam reduced coke formation and resulted in a gasoline reformate with high research octane number (RON). The modified catalyst showed high conversion and favored the production of olefins, paraffin, and iso-paraffins, along with aromatics and naphthenes.