Adsorption of Aliphatic Alcohols on Yttria-Stabilized Zirconia

Abstract

Yttria-stabilized zirconia powders with 3, 5, 8 and 10 mol% yttria added (Z3Y, Z5Y, Z8Y and Z10Y, respectively) were prepared. XRD studies indicated that the Z3Y and Z5Y samples were tetragonal whereas Z8Y and Z10Y were found to be cubic in shape. The specific surface areas of the various samples were obtained from nitrogen adsorption isotherms. These showed that as the mol% Y2O3 increased in the samples, an initial increase in surface area occurred up to 5 mol% Y2O3 but thereafter started to decrease. The microporosity of the powders was calculated by applying the Dubinin—Radushkevich (D—R) equation to the data obtained from the nitrogen adsorption studies. D—R plots were found to be linear over the low relative pressure region, followed by an upward deviation at higher relative pressures for all five systems examined. This deviation from linearity corresponded to the existence of a heterogeneous system of micropores, capillary condensation in the transitional pores or multilayer formation on the macropore walls. The adsorption of methanol (MeOH), ethanol (EtOH), n-propanol (PrOH) and n-butanol (BuOH) on pure and yttria-stabilized zirconia was undertaken at temperatures between 273 K and 303 K. The corresponding isotherms obtained were all of type II in the BDDT classification. Specific surface areas were calculated from these isotherms using the Langmuir and BET adsorption isotherm equations and found to be a maximum for the Z5Y powder.