- 2011. 3
In Katada Laboratory, we are studying catalysis of solid acids, especially zeolites, and metal catalysts supported on these materials, in order to open a way to design solid catalysts.
As stated here, catalysts (especially, solid acid catalysts) have supported the society through the petroleum cracking. However, resources of petroleum have decreased, and the fraction of large molecules has become high. Innovations are demanded in the fields of utilization of this kind of heavy fraction and cracking of oil sand and oil shale into gasoline. These will overcome not only the energy crisis but also the CO2 problem as follows. The humankind must consume the oil sand and oil shale even if the utilization efficiency is low. Control of CO2 production should be dependent on the efficiency of gasoline production from these resources. Furthermore, it is demanded to develop catalysts which can decompose cellulose and lignin due to plants. It will strongly extend the potential of utilization of solar energy.
For these purposes, the demanded ability is the decomposition of a large molecule. Key for realizing such ability is the construction of acid site on an open space. The energy problem will be solved with an excellent solid acid catalyst.
Zeolite is a material like sand consisting of SiO2 and Al2O3. Substitution of Si4+ by Al3+ generates H+ with Brønsted acidity. Bond angles and lengths around the acid site control the acid strength and catalytic performance. Something in an atomic scale creates the fantastic function of zeolite. It is believed that we can develop an extremely useful catalyst by clarifying its principle. However, even analysis of acidic property has been difficult in the field of solid acid catalyst. The humankind has experimentally found some catalysts, but many secrets in solid acid catalysis have not been solved. We have developed a method of ammonia TPD (temperature-programmed desorption), and have analyzed physicochemical properties as well as the controlling factor of acidic properties of many kinds of solid acid catalysts (mainly zeolites). We have been a top runner in this field. It will be soon to realize a dream by designing an excellent catalyst.
Based on the micropores with about 0.5 nm of diameter, zeolite has also molecular-sieving property and shape selectivity with which large molecules cannot diffuse but only small molecules can react or be formed. Prof. Niwa developed a method of chemical vapor deposition (CVD) of silica to control the pore-opening size of zeolite, and found a process for selective production of para-xylene, a raw material of PET (polyethylene terephthalate). We will continue this study to develop processes where only desired molecules are produced with no excess raw materials and no by-products.
Also we have prepared an extremely active catalyst for Suzuki-Miyaura reaction based on atomically dispersed Pd particles hold by the zeolite acid sites. In this study, observations of microstructure of Pd by EXAFS in SPring 8 were very important. With ultrananotechnology, finer and newer than old nanotechnology, we aim to open a way to rational design of catalyst and to contribute to the protection of environment and resources..
In Katada Lab., we will study and dispatch knowledge for humankind from Tottori based on solid catalysts.