Catalysis 2023 Issue

A Pierre-Yves Le Goff, Pierre-Yves.LE-GOFF@axens.net, Global Market Manager Reforming/Isomerization, Axens Arnaud Cotte, Arnaud.cotte@axens.net, Aromatics Product Line Manager, Axens The most important building block molecules for the down- stream aromatics derivatives value chain are benzene (BZ) and paraxylene (PX). BZ is mainly used for styrene produc - tion, polyamide, and polycarbonate, while PX’s principal usage is for polyethylene terephthalate production. While BZ can also be produced by the naphtha steam cracker unit, the vast majority of PX is obtained from the conversion of naphtha catalytic reforming effluent, namely reformate. The reformate conversion plant is commonly called an aromatics complex and employs multiple cata- lytic upgrading processes, fractionation sections and puri- fication units, resulting in intense capital and operational costs. With market trends pushing for continuous effort in max- imising both profitability and reducing the carbon footprint of PX production, it is essential to deploy advanced molecu- lar and energy management supported by leading catalysts and processes. Particularly, there is a rising interest in combining liquid phase xylenes isomerisation (LPI) and gas phase ethylben - zene reforming xylenes isomerisation (EBR) in the xylenes final conversion block to unlock significant reduction of capital and operational expenditures on the aromatics com- plex. Feedstock requirements are drastically lowered, lead- ing to further substantial savings on upstream preparation units. This also improves profitability, increasing the yield of highly valuable molecules only: PX and BZ, especially PX. Finally, LPI units present an intrinsically lower carbon foot- print when compared with traditional vapour phase xylenes isomerisation units. The newest scheme involving LPI, which can be imple- mented in existing aromatic complexes, provides improved economics and reduced GHG emissions. To push further PX production selectivity from a given fossil feedstock while incorporating lower carbon footprint sourced methanol, an aromatics alkylation process can also be considered.

Second-generation renewable feedstocks derived from lignocellulosic biomass are often high in oxygen and water content. With high oxygen and water content, these feed- stocks by their nature will reduce the yields of saleable FCC products from the FCC. Additionally, water and oxygen can impact product quality and downstream processing, and these impacts have to be carefully considered when researching co-processing opportunities. Pilot plant test- ing with oxygen speciation analysis capabilities is a useful tool to predict the effects of both factors on yield structure, product quality, and ex Rx product processing. In summary, catalyst and technology providers should be consulted to evaluate the optimal strategy for co-pro- cessing second- and third-generation renewable feedstock components in the individual FCC unit. Once established in the plant, increasing the amount of renewable feedstock content should be reviewed by the respective partners as a higher proportion can create new challenges to catalyst, product quality, and operation. 1 European Parliament, EPRS, Advanced biofuels: Technologies and EU policy, Briefing, 8 June 2017. A Peter Andreas Nymann, Senior Solution Specialist, Topsoe, PAN@topsoe.com Like first-generation renewable feedstocks, second- and third-generation feedstocks also contain oxygen, leading to high H 2 consumption and temperature rises. Many of the same strategies therefore apply to these as well. Second and third may have different contaminant profiles that need to be dealt with by specialised grading material. Content of particulates from upstream processing and high acid- ity (like for the first generation) also needs to be managed in storage and equipment. Second- and third-generation renewable feedstocks that are triglyceride based may be treated in HydroFlex units by applying the same strategies as for first-generation feedstocks. However, in contrast to the first-generation renewable feedstocks, the second- and third-generation often come from solid-to-liquid conversion processes and, therefore, contain different hydrocarbons, not mainly triglycerides. These molecules include ring structures that need satura- tion and often ring opening. The requirement for hydro- cracking catalysts will, therefore, be more pronounced when processing second- and third-generation feed- stocks, and co-processing in hydrocrackers of these feeds will be more feasible than processing in medium-pressure hydrotreaters. Several projects and plants processing crude tall oil, pyrolysis oils from plastics or tyres or other second- and third-generation renewables are currently in operation or the late stages of implementation using Topsoe technologies. Q Considering the range of petrochemicals used cross- wise for preparing a wide range of marketable products, including textiles, detergents, adhesives, antifreeze, sol- vents, and pharmaceuticals, what state-of-the-art cata- lysts are emerging for production of petrochemicals such as styrene, polymers, and aromatics?

Ranate

Benzene Toluene

Benz/tol extraction

Benz/tol fractionation

Transalkylation

Paraxylene

Reformer

EB reforming isomeri s ation

Separation

Liquid phase isomeri s ation

HAR

Heavies

Figure 1 Aromatics derivatives value chain

Catalysis 2023