Hi Hassna Belhaj

You may have poor heat transfer from the hot plate to the aluminum bottle (depends a lot on the shape of the bottom of the bottle). The bottle should be immersed at least part-way into a heating medium that has a minimal vapor pressure, such as aluminum balls, a molten salt or a very low vapor pressure oil. That's if you feel you must work inside the glove box. Alternatively - and I would prefer this - you can wrap the bottle in an insulated electrical heating tape with voltage control; but you may want to do a similar experiment outside the glove box with a similar aluminum bottle to see if you reach the right temperature range.

If you're confident the bottle is hermetically closed, you may be able to do the heating outside the glove box, using an oil bath or even (gasp!) a water bath.