This book presents current research in the study of the principles, types and applications of catalysis. Topics discussed in this compilation include macroporous materials; a new kind of eco-compatible hybrid biocatalyst for selective reactions; new research in poylmer supported catalysts; ionic liquids as a catalyst or solvent for various organic transformations; polyoxometalates as effective catalyst for selective delignification of cellulosic pulps by ozone; hybrid organic-inorganic materials; preparation and characterization of coated microchannels for the selective catalytic reduction of NOx and emerging catalysts for wet air oxidation process.