Studies on the direct liquefaction of protein-contained biomass: The distribution of nitrogen in the products

In studies of the direct aqueous liquefaction of protein-contained biomass such as sewage sludge, nitrogen derived from proteins is distributed in both the oil and aqueous phases. The nitrogen in the oil is very difficult to remove by hydrotreatment over nickel/molybdenum catalysts. Egg albumin was used as a model protein in direct liquefaction studies of the nitrogen distribution in the products. The oil yield from albumin (10%) was much less than that obtained from actual feedstocks (typically in the range 30–40%). The nitrogen content of the oil (9%) represented less than 5% of the total nitrogen, while in the liquefaction of actual feedstocks, 30–50% of the nitrogen in the feedstock was found in the oil. No distribution of nitrogen to oil under 150°C occurred because of no oil yield. The majority of the nitrogen in albumin (80%) was distributed to the aqueous phase above 200°C. The distribution of nitrogen to oil was completed by 250°C. Sodium carbonate, used as a catalyst, prevented the distribution of nitrogen to oil. Albumin was decomposed to ammonia, not to amino acids.