Catalysis 2026 Issue

Pyrolysis vapours

Product vapours

Lights and naphtha

Synthetic or natural polymers

Crude oil

Non- condensable gas

Condensation section

Feedstock

Aromatisation

C+ aromatics

Fluidisation gas

Liquid product

Ethylbenzene isomerisation

C+ Trans- alkylation

Figure 2 Illustration of the ICCP process from BioBTX2

Benzene

Toluene

Xylenes

Whereas naphtha cracking is mostly thermal, the con- version of crude oil to aromatics and polymers is best con- verted catalytically. In these processes, the most common catalysts are zeolite-based, typically ZSM-5 zeolites com- plemented with a metal, such as zinc or gallium (Ga), to add a dehydrogenation function. Also, after the aromatisation process, several catalytic conversions are present to max- imise the eventual BTX yield, all of which are best executed using mesoporous, accessible zeolite catalysts.5 Integrated Cascading Catalytic Pyrolysis The ICCP technology is developed with the goal of making full carbon circularity possible.6 Using a cascaded process design featuring two distinct steps (pyrolysis followed by catalytic upgrading of the pyrolysis vapours) enables energy input optimisation and maximisation of BTX yields.2 At the same time, the exposure of the catalysts to contaminants is strategically controlled to maximise catalyst lifetime. In this contribution, advanced zeolite catalysts are deployed in the sector targeted to upgrade the pyrolysis vapours (i.e., R2 in Figure 2 ). Superior accessible zeolites and metal mesoporisation In the mid-1980s, the catalytic potential of increasing the access to the active sites in zeolites was first conceived.7 Shortly after, significant industrial and academic efforts focused on decreasing the crystal size, giving rise to the family of nano-zeolites, featuring crystal sizes ideally below 100 nm. Later, other methods were developed to increase access to the active sites: by increasing micropore size and dimensionality and/or by making additional large mesopores in standard-sized crystals.8 The latter can be achieved by either growing zeolites around templates or by post-synthetically treating standard zeolites. Importantly, despite the synthetic variations, they all achieved the same

MX + OX to PX Isomerisation

derived from it. These have the advantage that contami- nants can be more easily separated from the catalysts, and they build on the relatively high technology readiness level of thermal pyrolysis of waste plastics. Yet even though the oil or vapours derived from the pyrol- ysis process are relatively free from contaminants, it remains significantly different from fossil-derived oil, such as vacuum gas oil (VGO). For example, the relatively high instability of the plastic-based pyoils in storage complicates straightfor- ward processing of such feedstocks within existing refinery assets. Accordingly, in fluidised bed catalytic cracking, boost - ing the co-feeding rate of the plastic-based with traditional VGO streams above approximately 10 wt% is challenging. Perhaps the most advantageous manner remains the catalytic upgrading of pyoil vapours. In this pathway, the vapours from pyrolysis are directly converted into stable base chemicals, such as BTX, avoiding the majority of cat- alyst deactivation complications and directly exploiting the reactivity of pyrolysis products. Aromatisation Independent of the nature of the feedstock, aromatisa- tion reactions remain relevant for providing the building block for the chemical, fine, and pharmaceutical indus - tries. Traditionally, aromatics are derived from naphtha or light cracking. Yet developments are also ongoing to yield aromatics from crude oil (crude-to-chemicals) and, more recently from natural (biomass) or synthetic (plastic) poly- mer waste streams (see Figure 1 ). Figure 1 Overview of the production and refining of fos - sil-based and circular aromatics4

Zeopore

Shaping

Figure 3 Schematic summary of the metal mesoporisation process of Zeopore9

Catalysis 2026