Try
QuickReport1:=TQuickReport1.Create(self);
QuickReport1.ADOQuery1.SQL.Text:= 'Select * from cliente where frc = :s';
QuickReport1.ADOQuery1.Parameters[0].Value:= QuotedStr(txt_rfc.text);
QuickReport1.ADOQuery1.Open;
QuickReport1.Preview;
finally
QuickReport1.Free;