Still, I doubt that folks actually had made any isopropyl until perhaps pretty close to 1900. If I had to bet on a window, I'd say it happened sometime between 1890 and 1920. I'm almost positive that by the 1920s, the folks at GM and Du Pont had extracted from the hydrolysis of cellulose, every alcohol that had potential as a fuel.

All I did was google "isopropyl alcohol inventor".