Filtrol catalysts structure

The crystal structures of synthetic silica-magnesia and Filtrol SR catalyst have not been published. However, it has been reported that silica-magnesia is converted to a crystalline nonporous magnesium silicate when heated to about 1400°F. (354). 

Several zeolites in the II-form, two activated clays, a silica-alumina, a sulfonic acid resin and a silica-occluded heteropoly acid were tested in the reaction of cyclohcxcne and toluene (excess) at 110 °C [64]. The ortho / meta / para ratio of the mixtures strongly depends on the structure of the catalysts involved. With zeolite H-USY and Filtrol-24 as active catalysts the meta / para ratio is found to be about 2 1, in agreement with the thermodynamic equilibrium, and the ortho-isomer is essentially absent.By contrast 11-Bcta and H-mordenite gave a meta /para ratio of 1 4.5. As H-USY appeared to be a good isomerization catalyst for the cyclohexyltoluenes, the mechanism may involve ortho / para-alkylation followed by isomerization. Researchers of UOP (Dcs Plaines, USA) found a separation method for meta / para cyclohexyltoluenc (undisclosed technique). Altogether the results open a new low-waste route to 3-methylbiphenyl. 

Preferred bentonite clays are those whose chief constituent is mont-morillonite, a mineral of the composition corresponding to the empirical formula, 4Si02-Al203 H20. The principal sources of raw clay for the manufacture of the presently most widely used natural catalyst (Filtrol Corporation) are deposits in Arizona and Mississippi. The clay from these deposits contains appreciable amounts of impurities, principally CaO, MgO, and Fe203, which replace part of the A1203 in the ideal montmorillonite structure. The catalyst is prepared by leaching the raw clay with dilute sulfuric acid until about half of the alumina and associated impurities is removed. The resulting product is then washed, partially dried, and extruded into pellets, after which it is activated by calcination. A typical analysis of the finished catalyst is as follows (Mills, 12). 

Operationally, the basic difference between the Type X and Type Y structures was largely a matter of thermal stability, although acid strength-related differences in selectivity were also found. While the Type Y zeolite was much more stable, it was also much more expensive. Davison initially marketed their XZ-15 catalyst, containing steam-stabilized Y zeolite admixed with low-alumina silica-alumina, at a price of 800 per ton. This was quite a high price at the time, but despite that, about 15 refiners tried it. At the same time, Filtrol introduced their Grade 800 catalyst, and although they didn t officially claim that it contained molecular sieves, the product distributions clearly pointed to their presence (67). 

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