Evaluation of a Ti–Base Alloy as Steam Cracking Reactor Material

Low-coking reactor material technologies are key for improving the performance and sustainability of steam crackers. In an attempt to appraise the coking performance of an alternative Ti−base alloy during ethane steam cracking, an experimental study was performed in a jet stirred reactor under industrially relevant conditions using thermogravimetry (T gasphase = 1173 K, P tot = 0.1 MPa, X C2H6 = 70%, and dilution δ = 0.33 kg H2O /kg HC ). Initially, a typical pretreatment used for Fe−Ni−Cr alloys was utilized and compared with a pretreatment at increased temperature, aiming at better surface oxidation and thus suppressing coke formation. The results revealed a decrease in coking rates upon high temperature pretreatment of the Ti−base alloy, however, its coking performance was significantly worse compared to the typically used Fe−Ni−Cr alloys, and carbon oxides formation increased by a factor of 30 or more. Moreover, the analyzed coupons showed crack propagation after coking/decoking and cooling down to ambient temperature. Scanning electron microscopy combined with energy-dispersive X-ray spectroscopy indicated that the prompt and unsystematic oxidation of the surface and bulk caused observable crack initiation and propagation due to alloy brittleness. Hence, the tested Ti−base alloy cannot be considered an industrially noteworthy steam cracking reactor alloy.