Hydrogen is a clean and efficient secondary energy source. With the continuous expansion of the application of hydrogen and the increasing prominence of energy and environment problems in the world, biohydrogen production technology has received extensive attention.Among them, hydrogen production from crude glycerol is also an important comprehensive utilization of by-products of biodiesel, which has attracted more and more attention. The main processes of hydrogen production from glycerol include steam reforming, partial oxidation, autothermal reforming, water phase reforming and supercritical water reforming. Steam reforming is the most widely used technology in chemical industry.ADHIKARI used steam reforming process to prepare hydrogen and catalyzed high endothermic reaction of glycerol and water to produce hydrogen. The catalytic reforming performance of Ni/MgO, Ni/Ti2 and Ni/CeO2 catalysts was investigated. It was found that Ni/MgO had the highest hydrogen production activity at 650℃ and the hydrogen yield could reach 56.5%. SLINN investigated the feasibility of hydrogen production from glycerol steam reforming, a byproduct of biodiesel. Pt-Al2O3 was used as catalyst. It was found that the higher the reaction temperature, the higher the gas phase yield, the highest yield was close to 100%, and the selectivity was 70%. Under the optimal conditions of hydrogen production from glycerol steam reforming, the carbon deposition of glycerol, a byproduct of biodiesel, was slightly higher than that of pure glycerol, but the catalytic activity of the two catalysts was similar.BYRD uses supercritical water reforming process, using glycerol, a byproduct of biodiesel, as raw material and Au/Al2O3 as catalyst to produce hydrogen. The reaction is carried out in a tubular fixed-bed reactor. The reaction temperature is 700-800 C, the glycerol concentration (mass fraction) in the feed is 40%. The maximum yield is close to the theoretical yield, and 7 mol hydrogen can be obtained per mol glycerol. These processes all have certain requirements for the purity of glycerol, because excessive impurities in crude glycerol will have a certain impact on the activity and service life of catalysts. In order to accelerate the efficiency of hydrogen production from crude glycerol and reduce production costs, it is necessary to develop catalysts with strong environmental adaptability, resistance to impurity corrosion and high activity.
Crude glycerol can also be converted into hydrogen by microbial catalytic transformation. GUILLAUME utilizes photosynthetic bacteria to convert crude glycerol into hydrogen by light fermentation. The yield of this process is high, producing 6 mol hydrogen per mol of glycerol (75% of the theoretical value and 8 mol hydrogen per mol of glycerol in theory). At the same time, it is found that impurities in crude glycerol, a byproduct of biodiesel, have no inhibition or toxicity to the whole fermentation process. Based on the above analysis, hydrogen can be prepared from crude glycerol, a by-product of biodiesel, by various chemical catalytic processes or microbial transformation technologies. The process has the advantages of renewable raw materials, clean and pollution-free. It is one of the efficient ways of hydrogen production and has a good development space.
