Novel one-stage process for manufacturing 1,3-butadiene from ethanol

This paper proposes a novel process for manufacturing 1,3-butadiene from renewable bioethanol, and re-evaluates two alternative processes: one-stage (Lebedev) and two-stages (Ostromislensky). The work presents an innovative design of the one-stage process employing Hf(IV)/Zn(II) catalyst and a consistent comparison of the above processes. The analysis is based on detailed reaction kinetics and systematic process synthesis. This work is distinct from previous studies by its use of inert gas in the reactor design in order to reproduce laboratory conditions, namely low ethanol partial pressure. Methane is proposed instead of the less-efficient nitrogen. The innovative reaction system involves adiabatic radial-flow reactors hosting catalyst particles of 2 mm that ensure high efficiency and reduced pressure drop. Cryogenic distillation and DMF absorption are assessed as alternatives for butadiene separation. Original methods are developed for removing by-products and impurities. Hence, the proposed flowsheet is generic for one-stage processes. Economic analysis reveals that the compression of inert-gas rich mixtures contributes substantially to the increase in capital and operation costs. Therefore, with today's available catalysts, the two-stage process appears more efficient than the one-stage process. To reduce this gap, a performant one-stage catalyst should show high butadiene selectivity by employing a small or no amount of inert gas.