and/or support surfaces. This results in active site and/or pore blockage. Coking: the deposition of heavy, carbon-rich solids onto surfaces due to the decomposition of hydrocarbons Vapor-solid reactions: formation of an inactive surface layer and/or formation of a volatile compound that exits the reactor. This results in a loss of surface area and/or catalyst material. Solid-state transformation: solid-state diffusion of catalyst support atoms to the surface followed by a reaction that forms an inactive phase. This results in a loss of catalyst surface area. Erosion: continual attrition of catalyst material common in fluidized-bed reactors. This results in a loss of catalyst material. In industry, catalyst deactivation costs billions every year due to process shutdown and catalyst replacement. Industrial examples In industry, many design variables must be considered including reactor and catalyst design across multiple scales ranging from the subnanometer to tens of meters. The conventional heterogeneous catalysis reactors include batch, continuous, and fluidized-bed reactors, while more recent setups include fixed-bed, microchannel, and multi-functional reactors. Other variables to consider are reactor dimensions, surface area, catalyst type, catalyst support, as well as reactor operating conditions such as temperature, pressure, and reactant concentrations. Some large-scale industrial processes incorporating heterogeneous catalysts are listed below. Other examples Reduction of nitriles in the synthesis of phenethylamine with Raney nickel catalyst and hydrogen in ammonia: The cracking, isomerisation, and reformation of hydrocarbons to form appropriate and useful blends of petrol. In automobiles, catalytic converters are used to catalyze three main reactions: The oxidation of carbon monoxide to carbon dioxide: 2CO(g) + O2(g) → 2CO2(g) The reduction of nitrogen monoxide back to nitrogen: 2NO(g) + 2CO(g) → N2(g) + 2CO2(g) The oxidation of hydrocarbons to water and carbon dioxide: 2 C6H6 + 15 O2 → 12 CO2 + 6 H2O This process can occur with any of hydrocarbon, but most commonly is performed with petrol or diesel. Asymmetric heterogeneous catalysis facilitates the production of pure enantiomer compounds using chiral heterogeneous catalysts. The majority of heterogeneous catalysts are based on metals or metal oxides; however, some chemical reactions can be catalyzed by carbon-based materials, e.g., oxidative dehydrogenations or selective oxidations. Ethylbenzene + 1/2 O2 → Styrene + H2O Acrolein + 1/2 O2 → Acrylic acid Solid-Liquid and Liquid-Liquid Catalyzed Reactions Although the majority of heterogeneous catalysts are solids, there are a few variations which are of practical value. For two immiscible solutions (liquids), one carries the catalyst while the