Development of new supported catalysts for the continuous alkylation of amines with alcohols

Objectives. The work set out to develop catalysts based on nickel and copper obtained by active phase chemical reduction and investigate their activity including the influence of the type of supports on the course of alkylation of amines with primary or secondary alcohols in a plug-flow reactor with a fixed catalyst bed.

Methods. The reactions were carried out in a continuous mode on a fixed bed of an appropriate catalyst in a plug flow microcatalytic apparatus at 160–240°C. NaX zeolite, magnesium oxide, and γ-Al₂O₃ were used as supports. After preparing the catalysts by impregnation from an excess solution of metal salts, the active metal phase was reduced with a sodium tetrahydridoborate aqueous solution. The composition of the resulting products was analyzed by gas–liquid chromatography, while their structure was confirmed by gas chromatography-mass spectrometry. The alkylating agents were ethanol, 2-propanol, 1-butanol, 1-pentanol, benzyl alcohol, and 1-octanol; alkylated amines were 1-butylamine, 1-hexylamine, 1-octylamine, aniline, morpholine, piperidine, and hexamethyleneimine.

Results. The alkylation of amines with alcohols catalyzed by metal (nickel and copper) nanoparticles supported on NaX zeolite, magnesium oxide MgO, and γ-Al₂O₃ in a plug-flow reactor with a fixed catalyst bed at atmospheric hydrogen pressure and 160–240°C leads to the formation of predominantly mono-N-alkylated products with yields up to 99%.

Conclusions. Nickel (or nickel and copper) nanoparticles supported on various supports are effective catalysts for the synthesis of secondary or tertiary amines in the plug-flow reactor.

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