C0AI2O4, alumina-supported

The total surface areas determined by the N2 BET method for the calcined, supported catalysts are listed in Table II. The X-ray diffraction (XRD) results showed diffraction peaks from a cubic lattice with a unit cell distance of 6.1 A were present on all of the calcined catalysts. Both C03O4 and C0AI2O4 have structures consistent with that lattice spacing, making assignment of the type of crystalline cobalt species present on the alumina supports difficult. 

The situation for the oxidic form of HDS catalysts supported on alumina is still more complicated, as was shown very early [35, 39, 67] and confirmed later by a very large number of authors. The system contains or may contain, according to the situation free cobalt oxide cobalt pseudoaluminate or C0AI2O4 free M0O3 the Co -Mo,-0 bilayer possibly A MoO at high loading. 

It is also important to avoid the formation of compounds between the catalytic material and the support. In the case of oxides, this would be a major problem. For example, cobalt or copper oxides on alumina would form aluminate spinels, such as C0AI2O4, with significantly lower catalytic activity. The catalyst should also the resistant to poisoning by contaminants in the natural gas or the air, as mentioned in Section 3.2.2. 

Supported membrane concepts that were studied in the past 10 years include 5-p.m-thick dense Pd on supported y-alumina (Pacheco Tanaka et al., 2006), 10-p m-thick dense Lao.sSro.sCoOa.g for O2 purification (van der Haar, 2001), 60-nm thin amorphous silica for small gas molecule separation and water pervaporation (de Vos and Vetweij, 1998), >1 xm-thick MFI zeolite membranes for parajortho-xyicnc isomer separation (Caro et al., 2000), 0.4-2-p.m thick mesoporous y-alumina (Yu et al., 2006), and 4 p,m mesoporous C0AI2O4 for nanofiltration of liquids (Condom et al., 2006). 

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