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 polymer supported catalysts; ionic liquids as a catalyst or solvent for various organic transformations; hybrid organic-inorganic materials; preparation and characterisation of coated micro-channels for the selective catalytic reduction of NOx and emerging catalysts for wet air oxidation process.