Desulphurisation of petrol is done in a

ANS:B - rotating disc extractor

Desulfurization of petrol is typically done using a packed extraction column. In this process, the petrol (or liquid hydrocarbon feedstock) is brought into contact with a solvent that selectively removes sulfur compounds from the feedstock. The packed extraction column provides a large interfacial area for mass transfer between the liquid hydrocarbon and the solvent. The sulfur-containing compounds are transferred from the liquid hydrocarbon phase into the solvent phase, resulting in desulfurized petrol. While other extraction equipment such as rotating disc extractors or plate type extraction columns can also be used for desulfurization processes, packed extraction columns are commonly employed due to their efficiency in providing contact between the phases and their scalability for industrial applications.