Catalytic Cracking of Crude Oil: Mini Review of Catalyst Formulations for Enhanced Selectivity to Light Olefins

The direct conversion of crude oil to light olefins is considered one the cheapest and most reliable sources of petrochemical primary feedstocks. Unlike in the past when refineries operated to produce mainly transportation fuels, such as gasoline and diesel, many refineries worldwide are considering tandem production of both fuels and chemicals (particularly, light olefins). To achieve this, refining technology, process optimization, and catalyst formulations may have to be reconfigured. Developing active and selective catalysts for crude oil cracking that fit into the current refinery system will go a long way in saving cost and time. In this review, catalyst formulations for the conversion of crude oil to light olefins have been discussed under the classifications: zeolite components, tuning of zeolite porosity, and matrix materials. USY has been the common zeolite that is used in the cracking of hydrocarbons to gasoline fractions, and ZSM-5 has the desired shape selectivity for cracking of paraffins in gasoline fractions to light olefins. At the same time, its low hydrogen transfer activity does not consume a large amount of generated light olefin, resulting in improvement of light olefin production. Various modifications of ZSM-5 composition have shown improvement in the light olefin yield. The wide range of hydrocarbons in crude oil makes pore size tuning of the zeolite especially important. Matrix materials generally increase the attrition resistance, hydrothermal and chemical stability, metal entrapment ability, coke resistivity, and fluidizable catalyst formation. However, they can also affect (positively or negatively) catalyst arrangement and active site properties, which makes careful selection very important.