Tronox has agreed to sell its soda ash business to the hydrocarbon firm Genesis Energy for $1.3 billion. Tronox will use the proceeds from the transaction to pay for its acquisition of titanium dioxide rival Cristal, which it agreed to purchase in February for $1.7 billion in cash, plus stock. Tronox bought the soda ash unit from FMC in 2015 for $1.6 billion. The soda ash business is the largest natural soda ash producer in the world, with a 28% share of production. At its mine in Green River, Wyo., it has the capacity to produce about 4 million metric tons of soda ash. The business had operating income of $84 million on $784 million in sales in 2016. Genesis, which specializes in energy services and transportation, says the purchase will give it greater diversification.