Mica montmorillonite clay activity

Recently, interest in clays as acidic catalysts has been quickened by the reported high catalytic activity of a synthetic mica-montmorillonite clay and its nickel-containing analogs. Wright et al. (247) have described the structure, thermal modification and surface acidity of the clay, which they designated SMM for synthetic mica-montmorillonite. 

From pyridine poisoning experiments and FT/IR measurements it can be concluded that this increased activity stems from the increased acidity of the resulting NiSMM (Ni-synthetic mica montmorillonite) clay, due to reduction of Ni. 

There has been renewed interest in catalytically active clays since the report by Swift and Black ( 1) to the effect that replacement of octahedrally coordinated aluminium ions by nickel or cobalt in synthetic smectite clays, as done by Granquist ( ), results in a new type of catalyst, called nickel- (or cobalt-) substituted mica montmorillonite (Ni(Co)SMM), which is very active in the isomerization and cracking of hydrocarbons. 

The presence of an organophilic clay increases the catalyst activity (10). Suitable clays include montmorillonite, hectorite, mica, etc. For example, Lucentite is a trioctylmonomethylammonium salt-treated synthetic hectorite. The clays are modified with quaternary ammonium compounds. The clays are heat treated prior to their use in the polymerization process. Further, the incorporated clay can improve the performance of the UHMWPE or function as filler. 

In order to determine the structural factors, concerning host clays, which improve on the catalytic efficiency of pillared clay by the fixation of cations, the following were chosen for comparison with TSM montmorillonite (as smectite, having less of a layer charge than TSM, but an octahedral vacancy like TSM) and taeniolite (as mica, having the same layer charge as TSM, but no octahedral vacancy, unlike TSM). Table 14-2 shows the catalytic activities for cumene... 

The three minerals - quartz, calcite and mica - tested by Von Moons, were ground to a very small particle size and the PI then determined on the fraction Imer than two microns. The activity of these minerals is low, as might be expected frxim their relatively simple crystal structure. Illite is probably the most widespread of all clay minerals but it usually occurs in conjunction with other minerals. The clay known as bentonite consists almost exclusively of the mineral montmorillonite. In its natural state bentonite is usually a sodium clay... 

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