Methacrylonitrile is an indispensable chemical intermediate in aerospace and wind energy material manufacturing. Currently, the one-step isobutene ammoxidation process is the industrial mainstream for its production, but its drawbacks of high reaction temperature, many byproducts, and high purification energy consumption have prompted researchers to explore alternatives. Although the two-step ammoxidation process has theoretical advantages, it is still in the experimental stage, with its economic and environmental benefits not systematically evaluated.
In a study published in ENG. Chem. Eng., researchers at China University of Petroleum and Ocean University of China conducted a systematic comparison of the two processes via techno-economic analysis and life cycle assessment under unified conditions of 99.5 % product purity and 1 t·h⁻¹ isobutene feed. Process simulations were performed using Aspen Plus V14.0 with the NRTL thermodynamic model, and core data were sourced from public patents and literature.
The results show that the two-step process achieves a higher yield of 82.4 % compared with 77.3 % for the one-step process, and produces no highly toxic byproduct HCN. However, the two-step process consumes 20.3 % more oxygen and 16.9 % more ammonia, and requires butyl acetate as a solvent with a circulation rate of 4.800 t·h⁻¹ and a supplementary dosage of 0.634 t·h⁻¹, whereas the one-step process operates solvent-free.
In terms of economic performance, the one-step process has a unit production cost of 1.90 USD·kgMAN⁻¹ compared with 2.23 USD·kgMAN⁻¹ for the two-step process, representing a 14.8 % cost advantage. The total annual cost of the one-step process is 1.40 × 10⁷ USD·a⁻¹ versus 1.76 × 10⁷ USD·a⁻¹ for the two-step process. The net present value of the one-step process is 5.83 × 10⁶ USD with an internal rate of return of 37.80 %, far exceeding the 20.85 % of the two-step process.
Environmental assessment shows that the one-step process has life cycle carbon emissions of 7.42 tCO₂-eq·tMAN⁻¹, while the two-step process emits 9.10 tCO₂-eq·tMAN⁻¹, a 22.55 % increase. Non-renewable energy consumption is 148.6 GJ·tMAN⁻¹ for the one-step process versus 211.2 GJ·tMAN⁻¹ for the two-step process, a 42.17 % increase. Raw material acquisition and transportation dominate greenhouse gas emissions, accounting for 81.23 % and 85.64 % of the total for the one-step and two-step processes, respectively.
Sensitivity analysis reveals that yield is the key lever for the two-step process. Each 1 % increase in yield reduces cost by 0.07 USD·kgMAN⁻¹ and emissions by 0.37 tCO₂-eq·tMAN⁻¹. When yield reaches 86.9 %, the economic and environmental performance of the two-step process becomes comparable to the one-step process. Even a 20 % reduction in medium-pressure steam consumption only lowers cost by 0.08 USD·kgMAN⁻¹, which is insufficient to close the gap. Similarly, a 30 % price drop in isobutene and butyl acetate cannot enable the two-step process to surpass the one-step process.
This work provides quantitative targets for catalyst development and a scientific basis for process selection and sustainability assessment.
DOI
10.1007/s11705-026-2702-3