Selective separation of homogeneous catalysts using silicalite membranes

The recovery of a homogeneous catalysts can be performed effectively by means of a zeolite membrane, which in many cases has a crystalline structure with pores smaller than transition metal catalysts but larger than the products. This concept has been successfully applied to the Diels-Alder reaction between acroleine and cyclopentadiene, catalyzed by a cationic dinuclear Pd(II) complex. A reaction mixture containing 5-norbornene-2-carboxyaldehyde and the catalyst employed for its synthesis [Pd(μ-Cl)(Ph2P-(CH2)4-PPh2)](CF3SO3)2 shows close to 100% recovery of the metallic compound.