In Rio there's the Imperial Palace (Paço Imperial):

Another Imperial Palace (Palácio Imperial) in Petrópolis:

The Cristal Palace, in Petrópolis (Palácio de Cristal), belonged to the Princess Isabel de Braganza and her husband, Count D'Eu:

The Grão-Pará's Palace (Palácio do Grão-Pará), home of a few members of the imperial family, in Petrópolis too:

Guanabara's Palace (Palácio de Guanabara), home of the Princess Isabel and her husband Count D'Eu:

Quinta da Boa Vista Palace, in Rio de Janeiro, home of D. João:

If I find more, I'll post.