Catalytic Mechanisms in Acetylene Hydration and Dimerization

The hydration of acetylene and its dimerization represent two cornerstone transformations in alkyne chemistry, underpinning the manufacture of key intermediates such as acetaldehyde, acetone and monovinylacetylene (MVA). Hydration typically proceeds via a metal-catalysed Markovnikov addition of water across the carbon–carbon triple bond, involving the formation of a vinyl cation or metal–acetylene π complex, followed by nucleophilic attack and protolysis. Historically reliant on mercury-based catalysts, recent efforts have shifted towards heterogeneous transition-metal oxides and mixed-metal systems to minimise toxicity and improve stability. In parallel, acetylene dimerization exploits copper(I) centres in acidic media to couple two acetylene molecules into MVA. The active cycle involves coordination of acetylene to Cu+, migratory insertion to form a vinyl–copper intermediate, and protonolysis to release the dimer. Catalyst deactivation via oxidation of Cu+ to Cu2+ and side reactions leading to polymerisation remain key challenges. Advances in ligand modification, bimetallic additives and zeolitic supports have begun to address selectivity, activity and longevity, broadening the scope of sustainable feedstocks for olefin production under industrially relevant conditions.

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Catalytic Mechanisms in Acetylene Hydration and Dimerization publication trend

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Technical terms

Markovnikov addition: Regioselective addition of a protic reagent to the more substituted carbon of an unsymmetrical alkene or alkyne.

Vinyl cation: A positively charged intermediate formed by protonation or metal-mediated activation of an alkyne.

Nieuwland catalyst: A homogeneous CuCl/HCl catalytic system traditionally used for acetylene dimerization to monovinylacetylene.

Protolysis: Cleavage of a metal–carbon bond by a proton, releasing the organic product.

Zeolite support: A crystalline aluminosilicate framework used to disperse and stabilise metal active sites in heterogeneous catalysis.

References

1. Dimerization of Acetylene to Monovinylacetylene (MVA) by Bimetallic Zr/Cu Catalyst in Nieuwland Catalytic System. Molecules (2022).
2. Catalytic synthesis of acetone by direct hydration of acetylene. E3S Web of Conferences (2023).
3. Light Olefins from Acetylene under Pressurized Conditions. Industrial & Engineering Chemistry Research (2023).