Catalytic Hydrogenation

P. Shanmugam

Department of Chemical Engineering

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Steam reforming

Petroleum Hydrogenation.

• Hydrogenation processes for the conversion of petroleum oils and petroleum products may be classified as
• destructive
• non-destructive.

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• Destructive hydrogenation (hydrogenolysis or hydro cracking) is characterized by the cleavage of carbon-to-carbon link-ages accompanied by hydrogen saturation of the fragments to produce lower boiling products.
• Such treatment requires severe processing conditions and the use of high hydrogen pressures to minimize polymerization and condensations leading to coke formation.
• Many other reactions such as isomerization, dehydrogenation, and cyclization occur under the drastic conditions employed.
• Processing under these severe conditions is generally referred to as "catalytic reforming." Many commercial reforming processes are in operation under such names as Hydroforming, Catforming, Houdriforming, Hyperforming, Platforming, UItraforming, Powerforming,

• Nondestructive or simple hydrogenation is generally used for the purpose of improving product quality without appreciable alteration of boiling range. Mild processing conditions are employed so that only the more unstable materials are attacked.
• Treatment under such mild conditions is generally called "hydrotreating" or "hydrofining." Commercial processes for hydro-treating are Hydrofining, Unifining, Hydropretreating, Hydrodesulfuriza-tion, Hydrotreating, Gulfining, etc
• Hydrotreating is being employed extensively in the petroleum industry for processing a variety of feedstoeks.
• Both straight-run and cracked petroleum products such as naphthas, kerosenes, middle distillates, gas oils (atmospheric and heavy vacuum types), cycle stocks, residues, asphalts, crudes, and shale oils may be so treated. The process primarily is employed as a "pretreat" previous to catalytic reforming or catalytic cracking.

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• Hydrotreating of feeds intended for further processing is desirable to the extent that the principal contributors to poor product quality or refin-ing characteristics are eliminated; this assures protection of the expen-sive catalysts employed in reforming and cracking reactions.
• Undesirable effects produced by certain types of contaminates are itemized below:
• Unsaturates: poor fuel stability, color degradation, lower catalytic cracking efficiency.
• Sulfur: poor odor, decreased tetraethyllead susceptibility in gasoline, corrosion of processing equipment, deactivation of catalysts.
• Oxygen: poor fuel-storage stability.
• Nitrogen: lower catalytic cracking efficiency, poor odor, color degradation, corrosion of processing equipment.
• MetaIs: deactivation of catalysts.
• Hydrotreating is carried out by charging the feed to the reactor together with a portion or all of the hydrogen produced in the catalytic reformer.
• Catalysts suitable are tungsten-nickel sulfide, cobalt-molybdenum-alumina, nickel oxide-silica-alumina, and platinum-alumina.