GAS-PHASE NON-CATALYTIC EPOXIDATION OF HEXAFLUOROPROPENE IN A TUBULAR REACTOR: OPTIMAL REACTION CONDITIONS

Abstract

The non-catalytic high-temperature oxidation of hexafluoropropene (HFP) by gaseous oxygen was carried out isothermally in a long tubular reactor (114.3 m length, ¹/₈-inch nominal diameter). The process was investigated at a total pressure of 450 kPa and over the temperature range of 453 to 503 K. Feed mixtures comprising 20 to 67% HFP in oxygen were used at total flow rates between 150 and 550 cm³ · min⁻¹, resulting in space-times from 80 to 160 s. 2,2,3-Trifluoro-3-(trifluoromethyl)-oxirane (hexafluoropropene oxide; HFPO), trifluoroacetyl fluoride, and carbonyl fluoride were identified as major oxidation products. In addition, tetrafluoroethene and hexafluorocyclopropane were found in the exit gas as well. The reactor operating conditions were optimized independently for HFPO selectivity and yield using a quadratic response surface technique. A maximum HFPO selectivity of 55.81% was found at conditions of 478.2 K, a HFP/O₂ molar feed ratio of 1.34 mol · mol⁻¹, and a space-time of 113 s. An optimum HFPO yield of 40.1% was identified at conditions of 483.2 K, a HFP/O₂ molar feed ratio of 1.16 mol · mol⁻¹, and a space-time of 121 s. Using a multi-response optimization technique, a combined optimum HFPO selectivity and yield of 56% and 40%, respectively, was obtained at conditions of 480 K, a HFP/O₂ molar feed ratio of 1.21 mol · mol⁻¹, and a space-time of 118 s. This represented the best trade-off between these two performance criteria. A parallel scaleup strategy was suggested for increasing throughput for industrial application.

Keywords:

• Epoxidation
• Gas-phase
• Hexafluoropropene
• Optimization

Notes

^a F = orthogonal factorial design points, S = axial design points, C = center points.

^b −1 = low value, 0 = center point value, +1 = high value, –α = low axial value, +α = high axial value.

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