(662a) Techno-Environmental Analysis of Olefins Production from Syngas Via Sorption-Enhanced Synthesis

Nowadays, the most widely used method for producing olefins is from fossil fuels through the cracking process. A staggering 400 Mt of CO₂ are emitted by light olefin plants, accounting for 27% of all CO₂ emissions in the industry. In recent years, the transformation of methanol into olefins has been gaining popularity, due to the possibility of generating methanol from renewable feedstock. However, the conventional process still presents several challenges, including high energy consumption and significant direct CO₂ emissions. Moreover, the current dependence on fossil raw materials, such as coal and natural gas, transformed into syngas to produce methanol raises further environmental concerns. A promising solution to address these challenges is the re-optimization of the entire production chain, implementing a circular model, where waste and biomass are used as sustainable feedstock for a new process. Indeed, advanced thermochemical technologies (ATTs), like pyrolysis and gasification, have an important role in converting waste into valuable chemical feedstock, hence promoting the green energy transition.

This project focuses on a novel olefin synthesis process specifically tailored for operating with CO₂-rich feedstock, as in the case of syngas obtained from the gasification of waste and biomass. In particular, the sorption-enhanced olefin synthesis (SEOS) technology helps us to overcome thermodynamic limitations associated with methanol formation and subsequent dehydration, thus improving yields and selectivity towards light olefins, while reducing energy consumption and CO₂ by-products.

A preliminary experimental campaign has identified the best catalyst and water sorbent combination for performing SEOS from a simulated biomass syngas stream. This has demonstrated the feasibility of combining two different processes (i.e., methanol synthesis and methanol-to-olefins) into a single reacting system, thus significantly simplifying the process layout and integration potential.

A sophisticated set of models has been developed using Aspen Plus to simulate the performance of the fully integrated biomass-to-olefins system, as well as to produce the mass and energy balance of the full plant. Experimental data have been directly used to inform the product distribution of direct syngas-to-olefins in the presence or absence of water removal steps and validate the model results. An energetic optimization and a sensitivity analysis of different parameters were done to probe and increase the efficiency of the plant. Furthermore, a techno-economic analysis, of the proposed plant layout was conducted to understand the operating cost of this technology and the levelised cost of olefin products.

Finally, the optimised data, mass, and energy balances will be used to perform a comprehensive Life Cycle Assessment (LCA) analysis to unveil the sustainability performance but also the bottlenecks of the process, comparing with other olefin synthesis processes, and to analyze different impact categories, such as climate change, resource use, energy carriers, freshwater eutrophication, etc., using a cradle-to-gate approach.