Biomass‐Derived Renewable Aromatics: Selective Routes and Outlook for p‐Xylene Commercialisation

Abstract

Methylbenzenes are among the most important organic chemicals today and, among them, p-xylene deserves particular attention because of its production volume and its application in the manufacture of polyethylene terephthalate (PET). There is great interest in producing this commodity chemical more sustainably from biomass sources, particularly driven by manufacturers willing to produce more sustainable synthetic fibres and PET bottles for beverages. A renewable source for p-xylene would allow achieving this goal with minimal disruption to existing processes for PET production. Despite the fact that recently some routes to renewable p-xylene have been identified, there is no clear consensus on their feasibility or implications. We have critically reviewed the current state-of-the-art with focus on catalytic routes and possible outlook for commercialisation. Pathways to obtain p-xylene from a biomass-derived route include methanol-to-aromatics (MTA), ethanol dehydration, ethylene dimerization, furan cycloaddition or catalytic fast pyrolysis and hydrotreating of lignin. Some of the processes identified suggest near-future possibilities, but also more speculative or longer-term sources for synthesis of p-xylene are highlighted.

Selective conversion of furans to p‐xylene with surface‐modified zeolites

“…Industrially, PX is mostly obtained from the refining of petroleum‐derived gasoline followed by a separation process, though disproportionation and isomerization technologies have also been employed for its production . Owing to the growing consumption of oil and the negative environmental impacts, the production of PX from renewable biomass resources has gained significant attention recently …”

Surface‐Passivated Hierarchically Structured ZSM5 Zeolites: High‐Performance Shape‐Selective Catalysts for para‐Xylene Production

“…Because these three isomers have similar boiling points and molecular size, the product purification is rather difficult and energy‐intensive . Thus, selective production of p ‐X through disproportionation, alkylation, and isomerization are of great significance and gaining more and more attention . To increase selectivity towards para ‐isomer, catalysts with excellent shape‐selectivity are indispensable.…”

Production of bio‐based p‐xylene via catalytic pyrolysis of biomass over metal oxide‐modified HZSM‐5 zeolites

“…p ‐Xylene can be produced from various subsequent catalytic transformations such as aromatic disproportionation, alkylation and isomerization processes . With the growing consumption of oil and its negative environmental impacts, there is considerable interest in producing commodity chemicals using renewable biomass resources …”

“…Biomass has been considered as a promising source to produce high‐value chemicals and bio‐fuels . Among various routes for producing bio‐based chemicals, fast pyrolysis and catalytic pyrolysis of biomass based on thermochemical conversion technology has received considerable interest .…”