Rentech Inc, which processes wood fibre, said Blackstone Group LP's credit arm would invest $150 million in the company in return for two board seats.

Rentech shares rose as much as 19 percent to $2.15 in morning trade on Thursday. The company was valued at $411.8 million as of the stock's close of $1.81 on Wednesday.

The company said GSO Capital Partners LP, the credit investment unit of Blackstone, will invest $100 million through convertible preferred stock and a $50 million term loan.

Blackstone named GSO's co-founder Douglas Ostrover and former chief executive of Smurfit-Stone Container Corp Patrick Moore to Rentech's board.

Rentech, which also makes and sells nitrogen fertilizer, said the funds would be used to grow its wood fibre processing business.