Microalgae co-pyrolysis with waste plastics to prepare low-O/N and hydrocarbon-rich liquid oil

Abstract

In order to reduce N-/O-compounds content and improve the quality of microalgae bio-oil, the co-pyrolysis /catalytic of Nannochloropsis sp. (NS) and polyethylene (LDPE) were studied in a fixed bed, and discussed the distribution of N and O, as well as the interaction between microalgae and LDPE and the influence of the addition of catalyst. It is found that co-pyrolysis could effectively inhibit the transformation of O and N to oil, promote O releasing as H2O and N conversion to gas products. In addition, plastic adding significantly reduced the content of O-/N-compounds in oil, such as carboxylic acid, amide and N-heterocyclic, and increased the aliphatics content. Besides, it effectively promoted the formation of hydrocarbon gas, and showed a certain synergistic effect on CO and H2, and the interaction reached the maximum at 25%LDPE. Furthermore, ZSM-5 could promote the formation of hydrocarbon gas, increase the LHV of gas products (35.6 MJ/Nm3), and further reduce the nitrogen compounds in the oil, while the N in microalgae transferred to gas, and O converted to gas and H2O, which resulted in the further reduction of the O and N contents in the oil. Moreover, catalytic co–pyrolysis could inhibit the formation of aromatic hydrocarbons to a certain extent and improve the selectivity of aliphatic hydrocarbons.