github.com/fishjerky/phalcon-mssql is your answer. But I had the same issue with this adapter.
So I changed from
"{$descriptor['pdoType']}:host={$descriptor['host']};dbname={$descriptor['dbname']}"
to
"{$descriptor['pdoType']}:server={$descriptor['host']};database={$descriptor['dbname']}"
Also you need to make sure 'sqlsrv' is set for $config->database->pdoType.
Hope it helps.