“…There are some substances which could be used as a hydrogen donor for HCUP. Water, sodium borohydride, tetralin, citric acid, ammonia, methanol, ethanol, formic acid, hydrazine, methane, pentane, naphtha, light crudes, and hydrogen are mentioned in the literature . Non‐organic substances would make an emulsion when added to the process as a hydrogen donor making oil heavier and more viscous.…”