Of course it is OK to reuse published data associated with proper citation. If the authors are still around, they will probably even gladly share the source data with you.

If they are no longer available to ask, you can redigitalize their plot, e.g. with Automeris Web Plot Digitizer, and include it in your figure. If you want to play it at maximum safety level, you can use Rightslink; most journals have a "Get Rights and Permission" button directly on the article website and give out rights for reusage of their figures, even with editing privileges, for free. Along with that, they will usually provide an instruction how to cite properly, it's normally just the phrase "reproduced from [Ref.] with permission by [publisher]".

Thank you, Jürgen Weippert !

Yes, @alanaycardo, it is acceptable to use previously published TGA data together with newly generated data, provided that you clearly cite the source and make it explicit which results are from the literature and which are from your own experiments. This practice is quite common when addressing a new research objective, for example, when using published results as a reference, for comparison, or as supporting data.

Thank you Carla Goncalves de Oliveira Sarmento !

Yes, you can do that @alanaycardo, provided you give proper citation. For example, if you are testing your new biomass under pyrolysis conditions similar to those reported in the literature as you stated, it is valid to present your TGA curve alongside published data for comparable biomass. This type of comparison helps to highlight similarities or deviations and adds robustness to your analysis. Likewise, you can also combine multiple published sources (with proper citation) to identify general trends and is widely accepted and it often strengthens the credibility of your work.