Nayara Energy, backed by Russian oil major Rosneft, on Tuesday announced an investment of $850 million for its expansion into petrochemicals. The company said it is planning to set up a 4,50,000-tonne-a-year Polypropylene plant. Nayara added it has licensed technology from American chemicals firm WR Grace to produce a range of phthalate-free products at its refinery complex in Gujarat's Vadinar.