What conditions are used for cracking?

• A. Alumina (Al2O3) catalyst / Silica (SiO2) catalyst at 650ºC
• B. Platinum catalyst at 500ºC
• C. No catalyst at 700ºC
• D. Diamond catalyst at 1000ºC

Answer: (A)

Cracking is breaking long hydrocarbon chains into shorter ones, and doing it with a solid acid catalyst is the efficient way used in industry. Solid catalysts like alumina (Al2O3) or silica-alumina (SiO2 with Al2O3) provide acidic sites that help cleave C–C bonds on the surface. This lowers the activation energy, so cracking can occur at a practical temperature around 650°C, giving a good yield of gasoline-range products.

Using a platinum catalyst isn’t typical for cracking in this context because Pt favors other reactions (like hydrogenation or reforming) and isn’t the acid-site catalyst needed for breaking carbon chains. Cracking without a catalyst at higher temperatures (around 700°C) is possible (thermal cracking), but it’s less selective and energy-intensive compared with catalytic cracking at around 650°C.