(ShareCast News) - Citigroup upgraded HSBC to 'buy' from 'neutral' and lifted the price target to 635p from 625p, noting that the stock is trading close to the low end of its valuation range over the past five and 10 years."Reflecting the improvement to capital ratios from upcoming divestments and also recent stock price weakness, we raise HSBC to buy," it said.Citi said HSBC may have a chairman change in 2016 and that failure to improve return on equity or the stock price will increase pressure on CEO Stuart Gulliver, who took office in 2011 at the same time as current chairman Douglas Flint."A new chairman could serve as a catalyst for acceleration of restructuring," the bank said.It said the announced Brazil and Turkey divestments may add up to around 90 basis points to HSBC core capital, which was last reported at 11.2%.It also said that US interest rates are likely to start rising from September 2015 and HSBC will at last begin to benefit from its attractive deposit base."In a simplified model, a 1ppt interest rate increase adds almost 20% to 2014 underlying profits," it said.At 0920 BST, HSBC shares were up 0.9% at 585.60p.