微粉体の生成と生成粉体の特性 Ｉ 塩基性炭酸マグネシウムの熱分解と熱分解生成物の検討

Abstract

The pyrolysis and pyrolysis products of basic magnesium carbonate were investigated by means of the infrared spectra, X-ray diffraction pattern, adsorption of argon at 77°K, scanning electron microscope (SEM) and the catalytic activity on the pyrolysis of isopropanol. The followings were found; (1) The formation of H2O from OH- and CO2 from CO32-proceeds separately in pyrolysis of basic Mg carbonate and the former proceeds at lower temperature. (2) The dehydrated sample including the partly decomposed products of carbonate showed to be amorphous in X-ray diffraction pattern. (3) The sample after pyrolysis at 450°C in which the pyrolysis of basic Mg carbonate performed showed the highest surface area such as 460 m2/g and the presence of MgO crystallite was recognized by X-ray diffractometry. (4) The samples after pyrolysis at higher temperature were identified to be MgO by X-ray diffractometry whereas the SEM photographs of these samples were observed to be the same shape as that of the original basic Mg carbonate. (5) The absorption band due to CO32-at 1450 cm-1 splits into two at 1410 cm-1 and 1510 cm-1 because of the degenerate symmetric streching vibration of CO32-due to perturbation with OH-in infrared spectra of basic Mg carbonate nevertheless these bands showed the degenerate with each other due to recovery of symmetry of CO32- accompanying with the dehydration of original basic carbonate. (6) The followings were produced by pyrolysis of basic Mg carbonate in various temperature range; 4MgCO3⋅Mg(OH)2⋅4H2O after heating at 30-150°C, mixture of 4MgCO3⋅Mg(OH)2⋅4H2O and MgO⋅MgCO3 after heating at 200-350°C, mixture of MgC⋅MgCO3 after heating at 350-450°C and MgO after heating at above 450°C. (7) MgO produced by the pyrolysis of basic Mg carbonate proceeds selectively the dehydrogenation in pyrolysis of isopropanol. It was remarkable that the smaller crystallite of MgO showed the high catalytic activity in the pyrolysis of isopropanol.