Johnson Matthey rose 2.4% on Tuesday, topping the FTSE 100 leader board after Citigroup upgraded the stock to 'buy' from 'neutral' and raised the price target to 3,600p from 3,200p.Citi pointed out that 50% of the company's earnings before interest and tax is based on emission catalysts for light duty vehicles (LDV) and heavy duty diesel vehicles and said the bank's analysis suggests both these markets are likely to deliver high single-digit growth for the foreseeable future.In addition, the bank said Johnson Matthey is a key beneficiary of sector growth due to its favourable regional and product mix. It said the company's LDV catalyst business is likely to outperform the market by a compound 150 basis points over the next five years."We see current valuations of JMAT as an attractive entry point; it is trading near its long-term average price-to-earning despite solid earnings potential and a sweet spot cycle for its key business: emission catalysts," said Citigroup.It added that underlying growth prospects for the Process Technologies and Precious Metal Products divisions also remain solid in the medium term.