NEW POSSIBILITIES OF LOW-TEMPERATURE GENERATION OF ACTIVE CENTERS DURING HETEROGENEOUS-HOMOGENEOUS ACTIVATION OF PROPANE ON SILICA GEL SURFACE, MODIFIED WITH ZnO BY THE SOL-GEL AND CHEMICAL TRANSPORT REACTION METHODS. Proceedings of the YSU B: Chemical and Biological Sciences, v. 55, n. 1 (254), p. 1–6, 28 Apr.2021.