Valorizing defatted microalgae after lipid extraction maximizes the value derived from microalgae. Catalytic fast pyrolysis (CFP) of defatted microalgae effectively promotes denitrogenation, thereby advancing the sustainable production of aromatic hydrocarbons (AHs). This study explored how the intricate structures of various amino acids (lysine, proline, and tryptophan) and extracted microalgae protein influenced nitrogen transformation pathways by means of pyrolysis − gas chromatography/mass spectrometry (Py-GC/MS) at 500 °C. The roles of acidic sites and pore sizes of metal-doped (0.5Ni) and alkali-treated (0.05 M) HZSM-5 (Hydrogen Zeolite Socony Mobil-5) catalysts in denitrogenation and aromatization were focused upon. The doping of Ni led to a 2.5 % increase in medium acidity, whereas the alkaline pretreatment resulted in a 40.0 % increase in mesopore volume. The relative yields of AHs from extracted protein increased by 10.0, 10.3, and 10.5 times with the addition of HZSM-5, 0.05 M and 0.5Ni, respectively. The denitrogenation indices of the extracted protein were 0.22, 0.28 and 0.31 when HZSM-5, 0.05 M and 0.5Ni catalysts were applied, respectively. The results revealed that surface area enhanced the adsorption of intermediates from lysine, facilitating their entry into pore channels for subsequent reactions on acid sites. The formation of mesopores in the 0.05 M catalyst improved mass diffusion and accessibility of acids sites for the pyrolysis of proline and tryptophan which had a larger molecular size than lysine. A hydrogenation catalyst like Ni was crucial especially for the cleavage of N-heterocyclic amino acids with lower degree of saturation within N-containing bonds. This research provides a basic understanding of the roles that chemical structures of amino acids and catalysts synthesis play in the efficient denitrogenation and AHs production from microalgae pyrolysis.

中文翻译：

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催化剂孔隙率和酸度在微藻催化快速热解过程中氮转化中的作用：提取蛋白和模型氨基酸的研究


脂质提取后对脱脂微藻进行估价可最大限度地提高微藻的价值。脱脂微藻的催化快速热解 （CFP） 有效促进脱氮，从而促进芳烃 （AH） 的可持续生产。本研究通过在 500 °C 下通过热解 - 气相色谱/质谱 （Py-GC/MS） 探讨了各种氨基酸（赖氨酸、脯氨酸和色氨酸）和提取的微藻蛋白的复杂结构如何影响氮转化途径。 重点介绍了金属掺杂 （0.5Ni） 和碱处理 （0.05 M） HZSM-5 （Hydrogen Zeolite Socony Mobil-5） 催化剂的酸性位点和孔径在脱氮和芳构化中的作用。Ni 的掺杂导致中等酸度增加 2.5%，而碱性预处理导致中孔体积增加 40.0%。添加 HZSM-5 、 0.05 M 和 0.5 Ni 后，提取蛋白中 AHs 的相对产量分别提高了 10.0 、 10.3 和 10.5 倍。当使用 HZSM-5、0.05 M 和 0.5Ni 催化剂时，提取的蛋白质的脱氮指数分别为 0.22、0.28 和 0.31。结果表明，表面积增强了赖氨酸中间体的吸附，促进了它们进入孔通道，用于随后在酸位点上的反应。在 0.05 M 催化剂中形成介孔改善了酸位点的质量扩散和酸位点的可及性，用于热解脯氨酸和色氨酸，其分子尺寸比赖氨酸大。像 Ni 这样的加氢催化剂尤其对于在含 N 键内饱和度较低的 N-杂环氨基酸的裂解至关重要。 这项研究提供了对氨基酸和催化剂合成的化学结构在微藻热解高效脱氮和 AHs 生产中的作用的基本理解。