LISBON, March 18 (Reuters) - Portugal's pulp producer Altri said on Thursday it had hired financial advisers Lazard to prepare a stock market listing of its renewable unit Greenvolt on the Lisbon bourse, as it aims to shift from biomass to solar and wind energy.

Altri also picked former chief executive of EDP Renovaveis , Joao Manso Neto, to be the CEO of Greenvolt, it added.

Greenvolt has five thermoelectric plants producing energy from forest biomass, with about 97 MW of installed capacity.

"Greenvolt has an ambitious national and international expansion project. Under the leadership of Manso Neto ... Greenvolt intends to consolidate its leadership position in the national market and assert itself as a reference player at the international level," Altri said in a statement.

Biomass will remain its core business, but Greenvolt also seeks to expand "through innovative models, of solar and wind energy", it said.

Altri also mandated Portuguese law firm Vieira de Almeida & Associados to study the Initial Public Offering at Euronext Lisbon. Altri did not give further details, nor did it say when the IPO could take place.

In July, a Lisbon judge ordered the suspension of the chief executive of EDP-Energias de Portugal and Manso Neto, who was then CEO of subsidiary EDP Renovaveis, as part of a corruption investigation. EDP and the two former CEOs denied any wrongdoing.

(Reporting by Sergio Goncalves; editing by Andrei Khalip and Aurora Ellis)