DANBURY, Conn. (AP) â¿¿ Industrial gas supplier Praxair Inc. said Friday that it elected a senior executive from international metals company Rio Tinto Ltd. to its board of directors to help Praxair expand its global operations. Praxair said Bret Clayton's election to the board was effective Tuesday. Clayton is currently group executive of business support and operations at Rio Tinto, a position he has held since 2009. Prior to joining Rio Tinto, Clayton worked for the accounting firm PricewaterhouseCoopers for nine years, Praxair is the largest industrial gas company in the Americas, with 2011 sales of $11 billion. Praxair shares rose $1.14 to a record close of $116.47. The stock is up 9 percent since the start of the year.