Catalytic performance of supported KNO3 solid bases for methylation of cyclopentadiene

The catalytic performance of a series of supported KNO3 solid bases for the synthesis of methylcyclopentadiene via cyclopentadiene methylation with methanol was investigated. X-ray diffraction and N-2 adsorption were applied to study the characteristics of different supports and the decomposition of KNO3 on them. The base strength of samples was measured using Hammett indicator. Significant difference in base strength of different oxides-supported KNO3 was observed. A base strength (H-) of 27.0 was detected in KNO3 supported on ZrO2, gamma-Al2O3, hydrotalcite (HT), and MgO, which showed the characteristics of solid superbases; while a base strength ( H-) of only 9.3 was examined in SiO2 - and TiO2 - supported KNO3. Such difference in base strength could be ascribed to the differences in surface nature of supports. A suitable basicity was necessary for catalyzing the methylation of cyclopentadiene with methanol, since only small amounts of cyclopentadiene molecules were converted over catalysts with low basicity, such as KNO3/SiO2 and KNO3/TiO2 as well as most oxide supports. However, the acidity and surface area of catalysts also had certain effects on the reaction. The conversion of cyclopentadiene and selectivity for methylcyclopentadiene were around 32% and 86%, respectively, over KNO3/gamma-Al2O3 and KNO3/HT at 450 degrees C. Such catalytic activity was higher than that on MgO.