Effects of Pressure on the Chemical Properties of Solid Surfaces. V. The Surface Acidity of the Compressed Aluminum Sulfate

Abstract

Abstract In order to clarify the mechanism of the acidity change due to compression, aluminum sulfate was compressed under various pressures ranging from 0 to 4200 kg/cm2 and at a temperature of 20, 65, or 80°C, and the surface acidity and the structure of these samples were measured. It was found that the acidity change due to compression was proportionate to the protonic acid. Lewis acid was made to appear only by heating the sample at temperatures higher than 90°C. Further, for the purpose of increasing the surface acidity, the compression of the sample at lower temperatures was found to be more effective than the compression at higher temperatures. In addition to the spectroscopic data, the results of DTA and TGA experiments supported the idea that the observed acidity change resulted from the distortion of the structural unit of aluminum sulfate.