CHARACTERIZATION OF ZIRCONIA-BASED CATALYSTS PREPARED BY PRECIPITATION, CALCINATION, AND MODIFIED SOL-GEL METHODS

Zirconia-based catalysts were synthesized by various methods and were evaluated for the synthesis of isobutane and isobutene from CO hydroge nation. The methods of preparation included precipitation (ZrO2 (PPT)) , calcination of zirconyl salt (ZrO2 (H-0304)), and a modified sol-gel method (ZrO2 (sol-gel)). Acid-base properties of zirconia were affect ed by the method of preparation. The number of acidic sites on the sur face follows the order of ZrO2 (PPT) > ZrO2 (sol-gel) approximate to Z rO2 (H-0304), and the number of basic sites follows ZrO2 (PPT) > ZrO2 (sol-gel) > ZrO2 (H-0304). Furthermore, adding aluminum increased the numbers of acidic and basic sites, and adding silicon increased the nu mber of acidic sites but reduced the number of basic sites. The produc t distribution of CO hydrogenation depended on the acid-base propertie s of the catalyst, and the activity tests indicated that a large ratio of basic to acidic sites is a requirement for an active catalyst to p roduce isobutane and isobutene from CO hydrogenation.