Catalysis 2026 Issue

Fundamentally, however, refiners are limited in their ability to drive a true structural shift toward polyolefins. The polyolefins market already carries significant sunk capi - tal in purpose-built assets, particularly propane dehydro- genation (PDH) units, which provide ample supplies of propylene. In addition, mixed butenes production is already sufficient to meet current mar - ket demand. While operational adjust- ments, such as naphtha recycle to the FCC riser, are

Step 1

Step 2

Fuel Gas LPG LCO HCO Coke Gasoline

C2= C3= C4=

FCC feed

Zeolite-Y FCC b ase catalyst: p rimary reactions

ZSM-5, Zeolite ZSM-5 (olefins additive): s econdary reactions

High conversion to olefins precursors (light naphtha) Maximum b ottoms upgrading (optimised z eolite/ m atrix) High surface area to minimise activity dilution by ZSM-5 Coke selectivity and metals passivation functionalities for residue processing

Maximum olens Minimum base catalyst activity dilution Chemical and mechanical stability Good unit retention

Figure 1 Basic representation of an FCC catalytic system to shift gasoline to light olefins

u Conversion of feed molecules into light olefins precur - sors, mainly light naphtha-range molecules : This step is catalysed by zeolite-Y-based catalysts (also called base cata- lyst), the characteristics of which will depend on the specific feed properties, other unit targets, and process conditions. v Conversion of light naphtha precursors into light ole - fins : This step is catalysed by the ZSM-5 zeolite in the olefin additive. The concentration of this secondary catalyst in the unit inventory can range from 5 to 25%, typically depend- ing on the desired level of light olefins maximisation or on already existing limitations in the downstream units. Hydrogen transfer in the base catalyst is also a key factor to consider in light olefins maximisation. Directionally speak - ing, a base catalyst with lower hydrogen transfer is better to produce olefinic intermediates for ZSM-5 cracking, as well as to preserve light olefins already created. Other factors to consider when shifting fuels to light olefins in an FCC unit are the following: • Feed properties : Lighter feeds favour light olefins produc - tion over gasoline. • Unit severity : Increased reactor outlet temperature and catalyst-to-oil-ratio. • Hydrocarbon partial pressure : Reducing hydrocarbon partial pressure by injecting steam in the reaction environ- ment also contributes to increasing light olefins production at expense of gasoline. • Unit design : Contact time, type of reactor, presence or not of a secondary riser for naphtha, among other design features. By applying these bespoke concepts, a refiner can easily shift the fuel production, in this case shifting from gasoline to polyolefins building blocks, mainly propylene. The degree of shifting will depend on the specific unit limitations down - stream from the FCC reactor, as well as the level of Capex investment to adapt the FCC unit and downstream facilities to accommodate higher production of light olefins. A Mel Larson, Advisor, Becht, mlarson@becht.com From a refinery perspective, the only unit capable of produc - ing polyolefin precursors in a cost-effective manner is the FCC unit. FCC technology can generate propylene and light olefins as secondary products while still fulfilling its primary role in fuels production.

technically feasible and practised in regions such as India and the Asia-Pacific, these strategies do not materially change the overall supply-demand balance. Incremental increases in olefin production from refineries risk oversupplying an already well-served market. As a result, refiners can only play a marginal, opportunistic role rather than leading a structural shift. FCC-based olefins production can complement petrochemical supply when economics align. However, it does not represent a scalable or transformative pathway for refiners to pivot away from fuels toward polyolefins in a cost-effective manner. A Danny Verboekend, Chief Scientific Officer, Zeopore Technologies, danny.verboekend@zeopore.com The refiner’s shift to produce polyolefins instead of fuels involves the synthesis of chemical building blocks, typically of ethylene or propylene The synthesis of such small ole- fins is ideally done with the highest efficiency and the least amount of steps. Hence, the nature of the refinery feedstock will dictate the most cost-effective route. For fossil oil-based refineries, small olefin yields may be boosted by using olefin-targeted FCC or, perhaps even bet - ter, more specific crude-to-chemical technologies, both being largely based on zeolite-catalysed cracking. Also, for larger circular biomass-derived hydrocarbon feedstocks, such as oils and waxes (and related hydroprocessed esters and fatty acids [HEFA]), such catalytic processes may be used. In contrast, circular C 1 carbon streams (syngas, methane, or methanol) may be grown to C 2 and C 3 olefins. In the latter scenario, the conversion of alcohols to olefins plays a cen - tral role and can be achieved using established processes such as methanol-to-olefins and methanol-to-propylene). Importantly, in addition to catalytic cracking, zeolites also play a pivotal role in these applications to attain a high yield of olefins. For zeolite-catalysed downsizing or growing of hydro- carbons, a large potential to increase the cost-effectiveness has been established over the last decade. It has been (aca- demically) proven that, for virtually any reaction involving a hydrocarbon, the narrow zeolitic micropores offer a plethora of benefits catalytically; however, they also offer access and transport limitations, hampering their catalytic performance.

Catalysis 2026