Surface organometallic chemistry on zeolites. Synthesis and characterization of mordenites modified BU tetrabutyltin application to the C₈ cut isomerization

Modification of a H-mordenite (HM) has been achieved by the controlled reaction of bulky organometallic complexes such as dineopentylmagnesium and tetrabutyltin with the external surface. For both complexes, the first observed reaction is a reaction of solvolysis leading to the formation of a grafted alkyl complex, i.e.→ SI-O-MgNP and →Si-O-SnBu, respectively, and to the liberation of one mole of alkane per atom M (M=Sn, Mg). Full characterization of these surface alkyl complexes has been achieved by IR, ¹³C MAS NMR, analysis of the evolved gases, elemental analysis. Thermal decomposition at 350°C under vacuum leads to surface oxidized (Sn(II) or Sn(IV) well dispersed on the external surface of the mordenite. These grafted mordenites mixed with a 0.5% Pt/Al₂O₃, exhibit higher performance in the C₈ (orthoxylene+ethylbenzene) cut isomerization compared with non-modified mordenites. The activity is found to be higher and the dismutation yields have been strongly reduced, regeneration of grafted tetrabutyltin mordenite leads to additional reduction of dismutation.