The Creighton process involves the hydrogenation

Hydrogenation

Hydrogenation, to treat with hydrogen, also a form of chemical reduction, is a chemical reaction between molecular hydrogen and another compound or element, usually in the presence of a catalyst. The process is commonly employed to reduce or saturate organic compounds. Hydrogenation typically...

 of a 6 carbon chain alcohol. The reactant is 2,3,4,5,6-pentahydroxyhexanal (an aldehyde

Aldehyde

An aldehyde is an organic compound containing a formyl group. This functional group, with the structure R-CHO, consists of a carbonyl center bonded to hydrogen and an R group....

. The product is 1,2,3,4,5,6-hexanehexol (an alcohol

Alcohol

In chemistry, an alcohol is an organic compound in which the hydroxy functional group is bound to a carbon atom. In particular, this carbon center should be saturated, having single bonds to three other atoms....

; compare with ethylene glycol

Ethylene glycol

Ethylene glycol is an organic compound widely used as an automotive antifreeze and a precursor to polymers. In its pure form, it is an odorless, colorless, syrupy, sweet-tasting liquid...

 and glycerol

Glycerol

Glycerol is a simple polyol compound. It is a colorless, odorless, viscous liquid that is widely used in pharmaceutical formulations. Glycerol has three hydroxyl groups that are responsible for its solubility in water and its hygroscopic nature. The glycerol backbone is central to all lipids...

. The product has two more hydrogen atoms than the reactant: -CHO is replaced by -CH₂OH.
The Creighton process was patented in the 1920s. For details, please see the external link.