(Updates with securities filing confirming deal)

SAO PAULO, Nov 17 (Reuters) - Brazil's Petroleo Brasileiro SA has approved the sale of its liquefied petroleum gas unit to Ultrapar Participações SA, as Brazil's state-controlled firm disposes of assets to reduce the largest debt burden among global oil producers.

In a securities filing on Thursday, Petrobras said its board approved the sale of Liquigás Distribuidora SA to Ultrapar subsidiary Cia Ultragaz SA for 2.8 billion reais ($819 million).

Analysts said the high price tag for Liquigás, which was estimated over 10 times operational earnings, was due to Ultrapar's need to add Liquigás to grow in effort to expand margins.

"In our view, rich valuations are explained by the strong strategic logic for Ultrapar," said Rodolfo Angele, an analyst with JPMorgan Securities in São Paulo.

Preferred shares of Petrobras, the company's most widely traded class of stock, closed down 3.2 percent, after gaining as much as 3 percent during the day.

Chief Executive Officer Pedro Parente said this week in New York that Petrobras remains committed to meeting a two-year $15.1 billion asset sale target for year-end.

The Liquigás deal is part of that asset-sale program, aimed at trimming Petrobras' massive $130 billion of debt.

Analysts at Banco BTG Pactual and Banco Brasil Plural said the deal will be subject to tough scrutiny by Brazil's antitrust watchdog Cade.

Ultragaz has a 23 percent share of the Brazilian market, which would rise to 46 percent after the Liquigás acquisition, according to a Brasil Plural note to clients.

Ultragaz said in a filing that Banco Bradesco SA will finance the deal.

($1 = 3.42 reais) (Reporting by Tatiana Bautzer, Paula Laier and Bruno Federowski in Sao Paulo; Editing by Bernadette Baum, Meredith Mazzilli and Chris Reese)