Speciality chemicals group Johnson Matthey reported higher sales and profits and hiked its dividend but warned that changes in a deal with Anglo American Platinum (AAP) and currency movements would cancel out growth this year.Johnson, which makes catalytic converters for cars, said pre-tax profit in the year to the end of March rose 17% to £406.6m on a 4% increase in revenue to £11.1bn.The group said a good performance by its emission control technology division drove the rise, with an improved product mix in its European light duty vehicle catalyst business, continued growth in Asia and a good performance in heavy duty diesel catalysts in Europe as new rules came in.But it said a change in the company's contracts with AAP, lower average precious metal prices and weakness in some manufacturing operations hit its precious metal products sales, which stayed the same as last year.Chief Executive Neil Carson, who is stepping down after 10 years in the role, said the adverse impact of the loss of commission revenue from AAP and the effect of foreign currency translation would offset growth in 2014/15."Consequently, we currently expect that the group's performance in 2014/15 will be broadly in line with 2013/14," he said.The group proposed a final dividend of 45.5p, resulting in the full-year dividend rising 10% to 62.5p.PW