EFFECT OF ALKALINE-EARTH ADDED TO PLATINUM-SUPPORTING OXIDES ON PLATINUM DISPERSION AND DEHYDROGENATION ACTIVITY

Alkaline earth modification of silica gel, silicalite, and H-ZSM-5 imp roved the dispersion and the catalytic activity of the platinum suppor ted on them. More specifically, modification by adding alkaline earth (AE) resulted in an increase in platinum dispersion, which caused an i ncrease in the dehydrogenation activity of the alkaline earth-added ca talysts. The zero points of charge (ZPC) of the parent supports and th at of the supports modified by adding Mg2+, Ca2+, Sr2+, and Ba2+ were measured to study the effect of these alkaline earths on the dispersio n of the platinum. The modification by adding these alkaline earths ma de the ZPC values shift to the basic region, that is, from pH 1.7 to 1 1.1 for silicalite, from pH 1.7 to 9.9 for silica gel, and from pH 1.2 to 9.7 for H-ZSM-5 zeolite (Si/Al = 48). The surface charge of the su pports, measured in ZPC, appears to be a controlling factor for highly dispersed platinum particles.