From biomass to styrene: Modelling and simulating a sustainable production pathway

As one of the largest consumers of fossil-based energy, the chemical sector highlights the urgent need to explore renewable energy alternatives given the ongoing depletion of fossil fuel reserves and the unprecedented release of greenhouse gas emissions. A cleaner and more sustainable pathway for the production of styrene, a key intermediate in the plastics industry, was investigated through process modelling and simulation. The proposed sustainable route consists of four steps: i) conversion of biomass to bio-ethanol, ii) conversion of bio-ethanol to bio-ethylene, iii) transformation of bio-ethylene into bio-ethylbenzene, and iv) conversion of bio-ethylbenzene to bio-styrene. The technical investigation demonstrates that 2.4 tons of lignocellulosic biomass are required to produce one ton of bio-based styrene with a purity of 99.96 %, thus meeting the polymer-grade purity requirement. The biomass-to-bio-ethanol conversion step is the largest thermal energy consumer, accounting for 9.40 MWh/t _bio-styrene of the total of 11.03 MWh/t _bio-styrene. To improve the overall efficiency and performance of the whole system, an azeotropic distillation using n-pentane as an entrainer was examined. The use of azeotropic distillation yielded superior results since 5.8 times less thermal power is required (i.e., from 9.40 MWh/t _bio-styrene to 1.61 MWh/t _bio-styrene). The ethylbenzene dehydrogenation process ranks second in terms of thermal power consumption, yet by recovering and utilizing the steam generated during this step, energy savings of 0.5 MWh/t _bio-styrene were achieved. The proposed method for bio-styrene production enhances thermal energy efficiency while reducing external energy demand, leveraging lignocellulosic biomass as a feedstock.