The board of directors of Indian Oil Corporation(IOC) has approved doubling of capacity at the Panipat refinery from six million tonne to 12 million tonner per annum. The company board, which met here yesterday, also gave its nod to prepare a feasibility report for a Rs 500-crore project for upgradation of motor spirit being produced at its Haldia and Barauni refineries to meet Euro-IV norms.The plan is expected to brought down benzene content in motor spirit to less than one per cent.