Selective Hydrogenation of Acetylenes and Dienes

The removal of acetylenes and dienes from steam-cracked olefins is a critical step in purification. Selective hydrogenation processes and catalysts have become more important as worldwide olefin production has increased in 1999 to more than 90 million tormes of ethylene and almost 50 million tonnes of propylene. Demand for better catalysts with improved selectivity and longer operating cycles has grown as larger plants are built. Tighter product specifications have also been imposed now that more of the olefins produced are being converted to polyolefins. 

The urgent demand for better catalysts intensified in the late 1950s as polyethylene production was developed and new plants in Europe began to use naphtha feeds. Larger single-stream ethylene plants needed better reliabihty and selectivity from more active catalysts. In the short term, better acetylene conver- 

1931 Molybdenum disulfide supported on alumina. Acetylene hydrogenation in coke oven gas containing sulfur. 

1931 Nickel oxide/chromium oxide supported on alumina. Selective hydrogenation in ethylene and hydrogen mixtures. 

1940s Palladium supported on silica gel. Acetylene plant off-gas—lifetime eight months. 

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Reduction of nickel acetate with sodium hydride gave a nickel black catalyst that was active for the selective hydrogenation of acetylenes and dienes to the monoolefins. It was also capable of promoting the hydrogenation of carbonyl... 

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