Titanium Dioxide as a Catalyst Support in Heterogeneous Catalysis

Table 1

List of advantages and disadvantages of heterogeneous catalysis system.

Type of catalysis support	Advantages	Disadvantages
Organic polymer	(i) Easy and versatile functionalization, especially for the polymer containing aryl group; (ii) Hydrocarbon polymers are chemically inert-support does not interfere with catalytic groups; (iii) It can be prepared with a width range of physical properties (porosity, surface area, and solution characteristics)	(i) It has poor heat transfer ability; (ii) It has poor mechanical properties which prevent from the pulverization during stirring process in reactor; (iii) Commercial polymers are not always very defined and often contain unknown impurities; (iv) Physical properties vary widely depending on molecular weight and chemical nature
Metal	(i) It can induce some catalytic activity as homogeneous catalyst but more selectivity; (ii) It is easy to separate from the product; (iii) It gives rise to less corrosion; (iv) It can be used for long periods without sign of deterioration in properties	(i) Optimization of the reaction condition is more complex because there are more variables; (ii) leaching problem brought by the Van de Waals link between the catalyst
Carbon	(i) It has high surface area due to porous structure; (ii) It has relatively small amount of chemically bonded heteroatoms (mainly O2 and H2)	It could not be used for hydrogenation reaction >700 K or in the presence of O2 > 500 K because it may become gasified to yield methane and CO2, respectively
Dendrimer	(i) It coordinates strongly with metal catalyst; (ii) It leads to recyclable catalyst system and does not suffer from mass transfer limitation; (iii) It has well-defined macromolecular structure to precisely control catalyst support; (iv) Uniform distribution	(i) It suffers from diminished activity due to the reduction in accessibility accessibility; (ii) It depends on swelling properties influenced by catalytic performance