Hydrogenation of hydrocarbons

Of the unsaturated hydrocarbons, only the aromatics are present in petroleum crudes and, even more so, in coal liquids. The other unsaturated compounds - olefins, diolefins and acetylenics - are produced during the thermal or catalytic transformations used in refining and petrochemical processes. Viscoreduction and coking of petroleum residues, steam cracking of liquefied natural gases, gas condensates or naphtha, and coal pyrolysis are the main thermal processes that generate unsaturated molecules. Dehydrogenation of light kerosenes, catalytic reforming of gasolines and catalytic cracking of vacuum distillates are the most widespread catalytic processes generating unsaturated molecules.

Partial, selective or total hydrogenation of unsaturated hydrocarbons is an essential reaction in petroleum refining operations and in the production of major petrochemical intermediates. Indeed, it is necessary to remove the most unsaturated hydrocarbons (alkynes, diolefins) from light olefinic petroleum cuts to enable their use in petrochemicals or in the polymer industry, where very high olefin purities are required. Similarly, these unsaturated compounds, precursors of gums, must also be eliminated from petrol cuts to ensure their stability.

Selective hydrogenation to produce olefins without additional hydrogenation leading to the formation of alkanes and/or hydrogenation of the aromatic ring of the various compounds in the petrol cut, are reactions of interest because they enable maximum recovery of the petrol cut processed.

The characteristics of these hydrogenation reactions are presented in this dossier: thermodynamics, kinetics, catalysts and processes. Hydrogenation processes specific to the purification of different petroleum cuts are then described according to their type (selective, partial or total).

As is customary in the industry, the compositions given are mass values, unless otherwise indicated.