The reaction/method that does not give an alkane is Dehydrohalogenation of an alkyl halide.

Dehydrohalogenation of an alkyl halide:
Dehydrohalogenation is a chemical reaction in which a hydrogen halide is removed from an alkyl halide to form an alkene. It is a type of elimination reaction. In this reaction, the alkyl halide undergoes elimination of a hydrogen halide (H-X) to form an alkene.

Reaction mechanism:
The reaction proceeds via an E2 (bimolecular elimination) mechanism. In this mechanism, the base abstracts a proton from the carbon adjacent to the halogen atom (beta-carbon), and the leaving group (halide ion) leaves simultaneously, resulting in the formation of a double bond between the two adjacent carbon atoms.

Example:
For example, let's consider the dehydrohalogenation of 1-bromopropane:
CH3CH2CH2Br -> CH3CH=CH2 + HBr

Why dehydrohalogenation does not give an alkane:
Dehydrohalogenation does not give an alkane because it involves the elimination of a hydrogen halide (H-X) from an alkyl halide, resulting in the formation of an alkene. The removal of a hydrogen halide does not result in the formation of a saturated hydrocarbon (alkane). Instead, it forms an unsaturated hydrocarbon (alkene) due to the formation of a double bond between two adjacent carbon atoms.

Other options:
a) Catalytic hydrogenation of alkenes: Catalytic hydrogenation of alkenes involves the addition of hydrogen gas (H2) in the presence of a catalyst (such as platinum or palladium) to convert the alkene into an alkane. This reaction reduces the double bond and saturates the molecule, resulting in the formation of an alkane.

b) Wurtz reaction: The Wurtz reaction is a coupling reaction between two alkyl halides in the presence of sodium metal to form a higher molecular weight alkane. It involves the formation of a carbon-carbon bond by the reaction of alkyl halides.

c) Kolbe's electrolytic method: Kolbe's electrolytic method involves the electrolysis of a solution of alkali metal salts of carboxylic acids to produce alkane. It is a synthetic method for the preparation of alkanes.

In conclusion, the dehydrohalogenation of an alkyl halide does not give an alkane because it involves the elimination of a hydrogen halide (H-X) to form an alkene. The other options mentioned (catalytic hydrogenation of alkenes, Wurtz reaction, and Kolbe's electrolytic method) all involve the formation of alkanes.