Preparation And Oxidation-dehydration Catalytic Properties Of Synthetic Porous Functional Geopolymer Catalyst

Acidic, basic and oxidative catalysts are ubiquitously used in large-scale chemicals manufacturing. And the reaction usually includeds multi-steps. For example, glycerol only converted to high value chemicals acrylic acid included the acid-catalyzed dehydration and oxide-catalysed oxidation steps. But usually each catalyst only has one single type of catalytic active sites and thus for product involving acidic, basic and oxidative catalytic reactions. Consequently, multifunctional catalysts for integrated one-step processes is desired. To this end, researchers have studied multifunctional catalyst coexisting acidic and basic sites, such as an acidic layered clay combined with a basic layered clay for sequential reactions or immobilization some organic bases on acidic solid catalyst to establish difunctional catalyst in liquid phase. Zeolite-supported metal complexes and other supported type catalysts improve the relevant properties of catalyst in solution. However, Catalysts with coexisting acidic, basic and oxidative sites in liquid phase reactions are easy to result in the loss and dissolution of active component. Besides, the recycling and separation of the catalyst is difficult in liquid phase reaction. In a catalyst system, one can have adsorption/reaction sites with complementary chemical properties, truly bifunctional sites that would be very difficult to generate on the surface of a pure metal or alloy system. In addition to this, the solid phase trifunctional materials which can generate acidic, basic functions and with supported metal oxide have never succeeded.The following work describes a novel, alternative approach for preparing the solid phase geopolymer catalyst trifunctional with coexisting acidic, basic and oxiditive sites by a geopolymer system. Here geopolymer catalyst is prepared by using various kinds of LDHs which can work as basic catalyst for oxidation and montmorillonite disposed by acid which can work as acidic catalyst for dehydration. In such materials, coexisting sites and pores can control the observed selectivity, whereas all the materials are effectively nonporous particles.Finally the catalyst is used in the sequential reaction of glycerol oxidation-dehydration to acrylic acid,and the reaction selectivity, conversion rate are determined. The catalysts exhibited good performances in sequential oxidation-dehydration of glycerol to acrylic acid with a glycerol conversion around 90% and a 82.1% selectivity to acrylic acid,but only a 5% selectivity to acrylic acid. This geopolymer catalyst may serve as model systems to explore synthesis of bifunctional porous solid catalyst and applications for other oxidation-dehydration sequential reactions.