PTQ Q1 2023 Issue

Lewis acid

Micropores

Y -z eolite High acidity

Moderate acid

Modied ZSM-5

Macropores

Feed

LCO

LPG

Figure 3 Sequential cracking of hydrocarbon feed to light olefins using proprietary catalyst * formulation using strong acid sites, and the gasoline range olefins are converted to light olefins (LPG olefins) through modified shape-selective ZSM-5 with a pore size of 5-6 A o . The cat - alyst must have the proper pore size distribution to enable large feed molecules to enter, crack into lighter products, and diffuse out before being over-cracked to coke and gas. Therefore, it is essential to design a catalyst with optimal porosity for effective kinetic conversion. The catalyst archi - tecture and sequential cracking are shown in Figures 2 and 3 . The modified ZSM-5 of the formulation incorporates a metal function to increase light olefins. The catalytic cracking of alkanes occurs via bimolecular and monomolecular reaction mechanisms. If the monomo - lecular mechanism is dominant, the yield of light olefins (such as ethylene and propylene) is more. Bimolecular reactions are hydrogen transfer reactions, which will satu- rate the olefins. Hydrogen transfer in FCC is a well-known large feed molecules to enter, crack into lighter products, and diffuse out before being over-cracked to coke and gas The catalyst must have the proper pore size distribution to enable

Mesopores

Figure 2 Hierarchical catalyst architecture

system has cracking functionality to crack feed molecules to gasoline by use of hierarchical macro-mesoporous and micro-porous functions and increase light olefins by modi - fied shape-selective pentasil zeolite. There is an upgrada - tion of larger molecules by physical transport in macropores (Lewis acid sites) and primary cracking mesoporous sites (medium acid sites) of alumina, which is surface-modified to change the strength of the acid sites. The upgraded mol - ecule diffuses into zeolite pores yielding gasoline, which further cracks to light olefins in the presence of modified shape-selective ZSM-5 additive incorporated in the cata - lyst * formulation. The large molecules in the feed prefer to be precracked on the alumina surface. The feed molecules are 370+ boiling range consisting of saturates (C 14 -C 34 ) and heavy aromat - ics (C 14 -C 60 ) in the ranges of 40-60% and 35-45%, with a pore diameter of 12-20 A o and 12-30 A o . These hydro - carbon molecules are too large to fit into the zeolite pores. The macropores provide a free path for these molecules to transport and crack on mesopores of active alumina with a pore size of 12-100 A o . The upgraded molecules viz: LCO range come in contact with Y-zeolite pores with a pore size of 7-8 A o and convert to gasoline range molecules

RE-USY/ M-ZSM-5

Proprietary catalyst

Modied a lumina

Clay

Binder

Figure 4 Catalyst synthesis

PTQ Q1 2023