C₂ tail end catalysts: Present and future of selective C₂-hydrogenation

A discussion covers the contributions of Südchemie AG to the development of C₂ hydrogenation in terms of a focus on C₂ tail end catalyst portfolio; promoted catalysts: G-58 series; the meaning of high selectivity with respect to ethylene hydrogenation; the typical selectivity for the main G-58 types (G-58D, G-58C, G-58E); the CO-free operation with the commercial experience with the G-58C catalyst; the cycle length of G-58C vs. G-58B from Arak Petrochemical Co commercial experience; the selectivity of G-58C vs. G-58B, also from Arak Petrochemical Co commercial experience; Süd Chemie new C₂ catalysts, the G-58C TH catalyst; the new C₂ FE catalyst; and conclusion. Süd Chemie has over 150 plant references and 40 yr of experience in C₂ tail end catalyst technology. Eight of the company's commercial catalysts have been used. The three main types now offered are the G-58C, G-58D, and G-58E. The G-58 series of catalysts are palladium on special Al₂O₃ carriers with Ag promoter, successfully used since 1987. The total market share is 88% in more than 150 world-scale ethylene plants, 132 of which use the catalysts with Ag promotion. The G-58D catalyst is selective in CO-free use such as in ethane crackers. The G-58C is the leading catalyst in Europe and the Middle and Far East. It is the most flexible catalyst (naphtha and gas cracker). The G-58E catalyst is often the best solution if significant amounts of deactivating poisons such as As, P, Hg, hydrogen sulfide, and COS are expected. High selectivity means higher ethylene production; possibility of increased throughput (major saving at full capacity); and reduced energy requirements (lower production cost per kilogram of ethylene). Typical average selectivity for the three main G-58 catalyst types are G-58D, 60-70%; G-58C, 50-60%; and G-58E, 30-40%. Twelve out of 80 plants have used G-58C without any CO. The new C₂ TE catalyst offers reduced pressure of 50-60% vs. spherical catalysts, slightly higher selectivity, and significantly higher space velocity. The G-58C TH was installed in a commercial unit in February 2003. The new C₂ FE catalyst is Ag/Pd promoted. Now in scale-up, it has a higher selectivity than G-83C. It seems to be highly stable for de-ethanizer feeds, suitable for cleanup reactor for de-propanizer feeds, and for use in various processes.