Assessing methods for the production of renewable benzene

Abstract

Benzene is a widely used chemical feedstock without an alternative in polymer and high energy density liquid fuel production. Produced from fossil carbon, benzene consumption contributes to rising atmospheric CO2 levels at the end of life. Several low maturity routes to produce fossil carbon- free, renewable benzene are being developed, each with merits and shortfalls. However, analysis is lacking to evaluate how these routes compare and assess which show the most potential in a sustainability context. Here, nine diverse approaches to renewable benzene production are evaluated using a multi-step Multi-Criteria Decision Analysis (MCDA) technique across indicators in three sustainability categories: ‘People’, ‘Profit’, and ‘Planet’ (3Ps). Three example scenarios are presented to elucidate how stakeholder preference may inform weighting choices and hence outcome. In all cases, the use of Fe/Fe3O4 nanoparticle catalysts with CO2/H2 feed consistently ranked highest with HZSM-5 catalyst converting lignin feed ranked second. Notably, these routes are exemplified by the simplicity of their respective processes. However, due to the emerging nature of all routes, assessment rankings are likely to change with developmental research and subsequent scale-up. It is probable that any deployed technology would combine a variety of attributes rather than utilise any single route assessed here. Hence, positive and negative hotspots are identified. For example, Zn-ZrO2 nanoparticles on HZSM-5 exhibit exceptional catalyst lifetime, while many locations may lack the infrastructure to produce nanocatalysts, restricting choice of route. Therefore, an open-access model included with this work allows new routes to be added, process data to be updated and priorities altered. This enables practitioners to continue to assess new routes and improvements. Ultimately, the route decision will depend highly on geographic location, local availability of a given feedstock and compatibility with an effective catalyst.