Production of Nitrogen-Containing Compounds via the Conversion of Natural Microalgae from Water Blooms Catalyzed by ZrO2

Utilizing the inherent high nitrogen content in natural microalgae to produce value-added nitrogen-containing compounds such as fatty amides and fatty nitriles is a promising method. Herein, a method for producing value-added fatty amides and nitriles by liquefaction of natural microalgae from water blooms in n-heptane was developed. The effects of temperature, metal oxide catalyst (ZrO2, Al2O3, TiO2, ZnO, MgO, CaO), catalyst amount, and reaction time on the preparation of value-added nitrogen-containing compounds were studied. Under the optimized conditions (0.3 g ZrO2, 300 degrees C, 6 h), the total yield of fatty amides was 6.9 wt %, and the yield of fatty nitriles was 1.9 wt %. Compared with the results obtained in the absence of ZrO2, after adding ZrO2 the total yield of fatty acids was reduced by 4.7 wt % (18.5 to 13.8 wt %), while the total yield of fatty amides only increased by 0.9 wt % (6.0 to 6.9 wt %) and fatty nitriles was increased by 1.5 wt % (0.4 to 1.9 wt %). Exploring the role of ZrO2 by using model compounds (i. e., palmitic acid and palmitamide) revealed that ZrO2 could promote the dehydration of fatty amides to form fatty nitriles, but had limited effect on the reaction of fatty acid and NH3.