Unipec, the largest oil trader in China and the trading unit of state-held refiner Sinopec, has purchased 9 million barrels of Abu Dhabi’s Upper Zakum crude grade for March loadings, traders told Bloomberg, in what could be a sign that Chinese oil demand will pick up pace in the second quarter. 18 cargoes of Upper Zakum crude is above the typical purchases of Unipec, according to the traders. Still, traders aren’t sure whether the buying spree for Abu Dhabi’s crude is directly linked with expectations of a surge in demand. It…