This Book presents the ability of zirconia and modified zirconia coated on cordierite honeycomb monolith as heterogeneous solid acid-base catalysts in selected liquid/vapour phase organic reactions. The catalyst coated on cordierite honeycomb monolith has advantages over powder form catalyst with high active surface area. A very thin layer of the catalysts loaded on monolith is highly effective and gives high active surface area, safe to store and long life time, and environmentally safe disposal, easy separation and complete recovery from the reaction mixture and active over a wide range of temperature. However, catalyst coated cordierite honeycomb monoliths is also an interesting initiative step in the field of liquid phase/vapour phase organic synthesis. Organic reactions were studied generally under conventional heating, microwave heating and comparison between the two. The influence of deviation of surface characteristics and acidity on the selectivity and activity of catalyst samples to various organic reactions were studied.For this purpose, pure zirconia can be modified by incorporating anion (SO42-) or cations (Al3+, Ca2+, Mg2+, Mo6+, W6+, etc.).