Royal Dutch Shell may build a multibillion-dollar chemical complex on the site of what is now a zinc plant about 30 miles (48 kilometers) north of Pittsburgh.

The move is part of a manufacturing shift to cheap natural gas from fracking, in which chemical-laced water and sand are blasted deep below ground.

The selection of the site, in Monaca, Pa., is a boost to Pennsylvania politicians, who had aggressively wooed Shell with promises of tax abatements.

Shell did not disclose any tax deals when it announced the site, but Pennsylvania legislators had proposed slashing corporate income and other taxes for 15 years for manufacturers investing at least $1 billion in the state.

Shell signed an option agreement to buy the site of Horsehead Holding Corp.'s current zinc production facility on the Ohio River. Horsehead is building a new plant in North Carolina.

Shell's chemical complex would turn ethane from natural gas into ethylene. Shell would then turn the ethylene into the lucrative chemical polyethylene, used to make packaging, cushions and clothing.