Sinopec Corp, Asia's largest refiner, posted a 36 per cent rise in second-quarter profit that beat forecasts as an improvement at its refining and marketing businesses more than offset a weakening chemicals division.Net profit was 18.44 billion yuan ($3.0 billion) for the April-June period versus 13.58 billion a year earlier, under international accounting standards, it said in a filing with the Shanghai bourse. The result topped with an average forecast of 16.03 billion yuan by six analysts polled by Thomson Reuters.The gross margin of its refining segment reached 2.9 per cent in the first half, up 1.5 per centage points from a year earlier, it said. Refining throughput edged up 0.32 per cent on year to 115.81 million tonnes.China implemented a more flexible fuel pricing mechanism in March 2013, the first major revamp in four years, to help avoid fuel shortages and tame consumption. However, refiners still cannot fully pass on higher crude costs to consumers because Beijing controls oil prices to help curb inflation.Sinopec's fuel marketing and distribution division registered a gross margin of 6.1 per cent, up 0.6 percentage points year on year. The state-run oil company unveiled a plan early this year to sell up to 30 per cent of the marketing and distribution arm, which includes a wholesale business, more than 30,000 petrol stations, over 23,000 convenience stores, as well as oil-products pipelines and storage facilities.