Ammonia TPD is a method to measure the acidic property of solid.
On widely various solid acid catalysts, it was clarified that the desorption was controlled by the equilibrium between the gaseous and adsorbed ammonia under usually utilized experimental conditions. A theoretical analysis method -- Curve-Fitting Method -- was proposed based on the theory expressing the desorption process. An IRMS-TPD method has been established by combining the infrared (IR) and mass (MS) spectroscopies. By these new methods, one can precisely determine the numbers, strengths and their distributions of Brønsted and Lewis acid sites individually on almost all of his/her solid samples. [Recent Review]

Acidic Property and Catalysis of Zeolite

The TPD method clarified that the Brønsted acid strength of SiOHAl unit in a zeolite framework was enhanced by the suppression from the both ends of the SiOHAl unit. The principle governing the zeolite acidity has been clarified for the first time.

Acidic Property and Catalysis of Surface Thin Layer of Oxide

The loading of tungsten and sulfur oxide on zirconia generates the activity for skeletal isomerization of alkane, and some people have believed that the catalytic activity is due to the superacidity. However, the surface structure and acidity of this binary-oxide have not been clear.
A method of benzaldehyde-ammonia titration (BAT) showed that the impregnated sulfate and tungsta formed a mono-atomic layer to cover the zirconia surface almost completely. The improved ammonia TPD method and the derived theory to calculate the H₀ function demonstrated that superacid site responsible to Friedel-Crafts alkylation was generated on the sub-monolayer of sulfate loaded on zirconia, but this was inactive for skeletal isomerization of alkane. For the latter reaction the relatively weak acid site with high density and Bronsted nature generated on excess sulfate was active, and the this kind of acid site was observed on the monolayer of tungstate.

Catalysis of Solid Acids for Synthesis and Conversion of Amines

Gallium-loaded MFI type silicate exhibited quite high catalytic activity and long life for vapor phase reaction of phenol and ammonia into aniline. Aluminum-loaded MCM-41 type mesoporous silicate showed high activity and selectivity for liquid phase synthesis of carbamate from dimethyl corbonate and aniline. This catalyst was insoluble to the solution, and therefore easiliy separated to enable the recycle use of catalyst.

Molecular-Sieving Silica Overlayer Prepared by Chemical Vapor Deposition Using Organic Template Molecule

After the preadsorption of such an organic compound as benzaldehyde, the CVD of Si(OCH₃)₄ and following removal of the organics forms a silica overlayer with the pores (vacancies) whose shape has precisely been controlled by the organic template. This novel material loaded on tin oxide is investigated as a gas sensor, and that loaded on alumina is as a solid acid catalyst. [An animation] The sensor is applied to the selective detection of a pollutant in semiconductor industry.

Silica Monolayer Solid Acid Catalyst Prepared by Chemical Vapor Deposition Method

By chemical vapor deposition (CVD) of Si(OCH₃)₄ formed a silica monolayer on such a basic metal oxide as alumina, titania and zirconia to cover the surface almost completely. The silica monolayer has both weak Broensted acidity and thermal stability. Surface concentration of hydroxyl groups on the alumina-loaded silica monolayer is quite low, and this gives the thermal stability. The silica monolayer loaded on alumina is a novel heat-resisting acid catalyst showing the acidity after calcination at 1493 K.

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