To say what Corribus: has said in another way, if you need an exothermic reaction, burning the required amount of fuel in air will generate heat. And if you have enough fuel, and concentrate the heat generated, you will raise the temperature of something else. If you need to get 100 grams of something from 0 to 100 °C, just get 200 grams of that something, heat it to 200 °C, and let them touch (excluding loss.)
Presumably, those plans won't work for your application, but you'll have to tell us why.