ENVIRONMENTS OF GA IN MFI-TYPE GA-SILICATES AND THEIR CATALYTIC PERFORMANCES

MFI-Type Ga-silicates with various Si/Ga ratios were synthesized from gels prepared using two different preparation methods: an alkoxide met hod ((A)) and a Mobil method ((M)). Gallium-silicates(A) from an alkox ide method were compared with Ga-silicates(M) from a Mobil method in t erms of their physical properties and catalytic performances in C4H10 conversion-reaction. The line width of a peak assigned to tetrahedral GaO4 in the Ga-71-MASNMR spectrum of Ga-silicate(M) was broader than t hat of Ga-silicate(A), and the unit cell volume of Ga-silicates(M) was less than that of Ga-silicates(A) of high Ga content. It is considere d, therefore, that the tetrahedral GaO4 incorporated into Ga-silicates (M) might have a lower symmetry than that incorporated into Ga-silicat es(A). Further, the tetrahedral GaO4 with low symmetry might be easily eluted from the silicate framework, because the amount of Ga elution from Ga-silicate(M) by treatment with HCl solution was greater than th at from Ga-silicate(A) of high Ga content. Gallium-silicates(A) yielde d more aromatic hydrocarbons from C4H10 than Ga-silicates(M) of high G a content. It is concluded that the tetrahedral GaO4 with lower symmet ry might have a higher dehydrogenation activity.