* Kayan says partners to equally share costs
* Plant have capacity of 330,000 tonnes of n-Butanol
* To be online in H2 2014
KHOBAR, Saudi Arabia, Jan 29 (Reuters) - Saudi Kayan Petrochemicals (2350.SE) on Saturday signed a preliminary agreement with Saudi Acrylic Acid Co (SAAC) and a joint venture between U.S. Dow Chemical (DOW.N) (DOW.N) and Saudi Aramco to build a 1.8 billion-riyal ($480 million) n-Butanol plant in the kingdom.
Kayan said in a bourse statement that the three partners will each hold an equal stake of 33.3 percent in the plant and would share the costs of the project.
The plant, designed to have an annual capacity of 330,000 tonnes of n-Butanol, will be located in Jubail and operated by SAAC, Kayan said.
Production is due to start in the second half of 2014.
Kayan, an affiliate of petrochemicals major Saudi Basic Industries Corp (SABIC) (2010.SE) is expected to begin commercial production at its Jubail petrochemicals complex in the second half of the year.
Aramco and Dow plan to build a $20 billion mega petrochemical project in Jubail. (Reporting by Reem Shamseddine; Editing by Sami Aboudi and Catherine Evans)