Microalgae co-pyrolysis with waste plastics to prepare low-O/N and hydrocarbon-rich liquid oil
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摘要: 为了减少油中氮氧化合物,提高微藻生物油品质,本研究在固定床上开展了微拟球藻(NS)和聚乙烯塑料(LDPE)的混合热解/催化特性,探讨了O和N在热解气、液、固相的分布,并以此探讨了微藻与LDPE之间的交互作用以及催化剂的加入对混合热解的影响。研究发现,混合热解能有效抑制O和N向油中转移,促进微藻中O转变为H2O,N向气体产物转移。此外塑料添加明显减少了油中羧酸、酰胺和含氮杂环等含氧/氮化合物,提高了脂肪烃含量,同时有效促进碳氢气体的形成,并对CO和H2也有一定的协同作用,特别是在25%LDPE时协同效应最强。同时ZSM-5能促进碳氢气体形成,提高气体产物的热值(35.6 MJ/m3),并进一步减少油中含氮化合物,促进N向气体转移,O向气体和H2O中转移,从而使油中O、N含量明显降低;此外混合催化热解能在一定程度上抑制芳烃的形成,提高脂肪烃选择性。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 the distribution of N and O was discussed, as well as the interaction between microalgae and LDPE and the influence of the addition of catalyst. It was found that co-pyrolysis could effectively inhibit the transformation of O and N to oil, and promote the O release 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.
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Key words:
- co-pyrolysis/catalysis /
- microalgae /
- LDPE /
- interaction /
- deoxygenation and denitrification
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表 1 样品的工业分析、元素分析和微藻的生化组成
Table 1 Proximate, ultimate analysis of samples and biochemical constituents of microalgae
Sample Ultimate analysis wad/% Proximate analysis wad/% Biochemical constituents wad/% C H N S O* M V FC A lipid protein carbohydrate* NS 50.61 7.31 6.68 0.64 24.8 4.01 79.61 10.38 6 30 40.8 19.2 LDPE 84.32 15.47 − 0.21 − − 100 − − * : by difference; –: not detected -
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