Polymers for the preparation of heterogeneous catalysts

Abstract

In this work it has been studied the effect different polymers (or also the same polymer with different properties) can make in the preparation of catalysts Ni-La/Al2O3 by the wet impregnation with excess of water. In order to do that, the catalysts were first prepared with the method “All in one”, a method that was developed in our laboratory group. This method consists on the preparation of aqueous suspensions with every component to obtain the final catalyst: the support, the precursor salt of the active material and the additives, were polymers are introduced. The method allows us to create the catalysts in suspensions that can be used directly for the structured substrates coating, or after drying and calcinating this suspensions, slurried catalysts in powder form can be obtained to use them for each characterization technique. After preparing the aqueous suspensions, they were characterised by viscosimetry in order to find out the changes on the viscosity made by the addition of the different polymers, and after drying and calcinating them, the obtained slurried catalysts were characterized by different techniques: N2 physisorption, CO chemisorption, temperature programmed reduction and X-ray diffraction. This characterization was made to study the effect of the added polymer in the catalyst, which was supposed to improve the effect on the Sabatier’s reaction. The results show that depending on the polymer added to the catalyst formulation, the utility of this would change, also that with the addition of the same polymer, modifying the molecular weight or the hydrolysis degree, the results obtained would be different, making some polymers more useful than others. On the other hand, it had been previously discovered that the use of polyvynil alcohol (PVA) and Ni content influences directly in the properties of catalysts obtained by the “All in one” method. PVA allows to control nickels particle size managing to have a higher dispersion and, as a consequence, the number of active centres is larger. In this work, PVA, polyvynilpyrrolidone (PVP) and polyethylene glycol (PEG) will be used to improve the dispersion and as a consequence, improve the active centres.