Published September 2000
This review evaluates a process for the direct ammoxidation of propane to acrylonitrile, a process that uses a catalyst of unusually high activity. The process and the performance of the catalyst are disclosed in patent US 5907052 (K. Hamada, et al., to Asahi Kasei Kogyo Kabushiki Kaisha, Osaka, Japan, May 25, 1999). The driver for such technology is the price differential between the conventional propylene feedstock and propane, which has averaged 10.5¢/lb over the last decade. The catalyst operates at 430°C (806°F) and achieves a per-pass propane conversion of 87% at 60% selectivity to acrylonitrile (52 mol% yield).
The previously best reported result (Sohio patents) was 40 mol% at 500°C (932°F). A key aspect of the invention is a method for maintaining the performance over long periods by adding so-called activators to the fluidized bed at intervals. The catalyst is a mixture of Mo, Te, V, and Nb oxides combined with silica. The activators are telluric and molybdic acids, which apparently make up for the fugitive loss of the corresponding oxides from the catalyst surface. Capital and production cost estimates for a 400 million lb/yr (181,000 t/yr) plant were developed for the process based on a conceptual flow scheme and design data generated in a process simulation (AspenPlus). Results are compared to the conventional propylene-based process.
