Palladium-containing zeolites and zeolite-like materials as multifunctional catalysts for hydrocondensation of butyric aldehyde with hydrogen

Various aspects of the preparation, formation, and catalytic action of Pd-c ontaining zeolites and zeolite-like materials VPI-5, AlPO4-8, AlPO4-5, SAPO (4)-5, and KX in the hydrocondensation of butyric aldehyde (BA) with hydrog en were studied. It was found that the main product of the reaction of BA w ith H-2 over the ion-exchanged catalyst Pd/KNaX is 2-ethylhexanal (process selectivity greater than or equal to 90%) under all of the examined catalys t pretreatment (activation) conditions. In the presence of systems based on microporous crystalline aluminophosphates and silicoaluminophosphates, the side reactions of BA hydrogenation yielding butanol, dehydration of butano l to dibutyl ether, decarbonylation of BA and produced Cs aldehydes, etc., occur along with the BA hydrocondensation, so that the selectivity of BA co nversion into 2-ethyl-hexanal is <50%. Using the Hz sorption-desorption tec hnique, the state of palladium in different catalysts was studied. It was f ound that Pd-0 particles formed upon hydrogen treatment of samples at 200 a nd 400 degrees C are of a nanometer size. The size is not uniform; there ar e bath rather large Pd-0 particles and small Pd-0 clusters. It was assumed that certain Pd-0 clusters can interact with Lewis acid sites of aluminopho sphates, transferring to the Pddelta+ state in which palladium exhibits cat alytic activity in aldehyde decarbonylation reactions. The Pd/KNaX catalyst lacks such sites and, hence, does not catalyze the decarbonylation of RCOH , thus ultimately resulting in high selectivity of the faujasite catalyst i n the hydrocondensation of butyric aldehyde with H-2 yielding 2-ethylhexana l.