SAO PAULO, Jan 7 (Reuters) - Brazilian state-run oil company Petrobras (PETR4.SA) said on Friday it expects to sell 100% of its preferred stake in petrochemical producer Braskem SA (BRKM5.SA) by February. The detailed timeframe came after Petrobras announced earlier in the day that the move was planned for the first quarter of 2022. Petroleo Brasileiro SA, as the company is formally known, also reiterated in a securities filing that the move will be conducted through a joint follow-on share offering with conglomerate Novonor. The oil giant has hired JPMorgan to manage the offer. Petrobras had repeatedly expressed its intention to sell its 36.1% stake in the petrochemical company. Novonor, formerly known as Odebrecht, holds a 38.3% stake in Braskem.