Selective hydrogenation of 1,3-butadiene in the presence of 1-butene under liquid phase conditions using structured catalysts

Different aluminium structured substrates (monoliths of 350 and 1100 cpsi; foams of 10, 20 and 40 ppi) have been loaded with NiPd/(CeO₂-Al₂O₃) catalyst by washcoating. To improve the adherence between catalyst particles and metallic surface, aluminium substrates were previously anodized to produce a rough (cracked) surface. Catalytic layers of different thickness have been deposited onto aluminium substrates. The catalytic coatings were characterized measuring their textural properties, adhesion and morphology. These structured catalysts have been tested in the selective hydrogenation of 1,3-butadiene in presence of 1-butene under liquid-phase conditions. The effects of some design parameters over the catalytic performance were studied: catalyst loading (125, 250 or 500 mg), geometry of the structured substrate (monoliths or foams), and porosity (cpsi or ppi). The catalytic results show that foams present better activity than the monoliths. This can be related to better mass and heat transfer in the case of foams. In addition, the catalytic coating thickness influence directly the reaction selectivity; thicker layers produce undesired products (BA and isomers) due to diffusion limitations. However, it seems that the mass transfer of reactants to the surface of the catalyst layer plays a major role than the diffusion of reactants inside the catalyst layer.