Catalytic conversion of glycerol to propylene glycol over copper/zine oxide-based catalysts: effect of catalyst supports

Abstract

In this work, the catalytic conversion of glycerol to propylene glycol (PG) was investigated over the copper/zinc oxide-based catalysts prepared by different supports--i.e. Alumina (Al₂O₃), amorphous silica-alumina (ASA), magnesium oxide (MgO), and hydrotalcite (Mg₆AI₂CO₃(OH)₁₆•4(H₂O)). The prepared catalysts were tested for the catalytic activity in a packed-bed reactor at 250 ºC and 500 psig under hydrogen atmosphere. CuZnO/Al₂O₃ gave the highest glycerol conversion and PG selectivity compared to CuZnO/MgO, CuZnO/Hydrotalcite, and CuZnO/ASA. This might be because the surface area of CuZnO/Al₂O₃ was larger than the other catalysts. Noticeably, CuZnO/MgO exhibited the highest performance in terms of stability. The effect of Na and K addition in feed was investigated on CuZnO/MgO and CuZnO/ Al₂O₃. The results showed that the relined glycerol exhibited a higher conversion compared to the refined glycerol mixed with 0.1% Na or with 0.1% K over CuZnO/Al₂O₃. On the other hand, the refined glycerol mixed with 0.1% Na or with 0.1% K exhibited a higher conversion compared to the refined glycerol feed on CuZnO/MgO. The glycerol conversion of the regenerated CuZnO/MgO catalyst was as good as that of the fresh catalyst.