TG−FTIR−MS和TG−GC/MS联用研究地沟油的热裂解特性

Characteristics of waste cooking oil pyrolysis by TG−FTIR−MS and TG−GC/MS

采用热重-红外-质谱联用技术(TG-FTIR-MS)和热重-气质联用技术(TG-GC/MS)分析地沟油热裂解过程中热重分析仪逸出气相产物的组成成分,探究地沟油的热裂解反应过程和热裂解特性。研究结果表明:地沟油热裂解释放气相产物的主要成分包括甘油二酯、甘油一酯、脂肪酸、脂肪醛、脂肪酮、烷烃、烯烃、芳香烃和CO2等,气相产物的组成成分随温度升高发生显著变化。地沟油的热裂解过程分为3个阶段:第1阶段主要发生甘油三酯分子中C-O键的断裂生成甘油二酯、甘油一酯、脂肪酸和脂肪醛,第2阶段为热裂解第1阶段产生的酯类化合物及脂肪酸发生C-O键、C-C键的断裂和脱羧反应生成脂肪酸、脂肪醛、脂肪酮、烷烃、烯烃和CO2;第3阶段为脂肪酸的挥发和脱羧反应生成烷烃、烯烃和CO2以及共轭双烯与取代烯烃的Diels-Alder反应生成芳香烃。

The combined thermogravimetric-Fourier transform infared spectromotry-mass spectrometry(TG-FTIR-MS)and thermogravimetric-gas chromatograph-mass spectrometry(TG-GC/MS) analysis were used to investigate the composition of waste cooking oil pyrolysis products evolved from thermogravimetric analyzer. The reaction process and characteristics of waste cooking oil pyrolysis were studied. The results show that the composition of gaseous products from waste cooking oil pyrolysis are diacylglycerols, monoglycerides, fatty acids, aliphatic aldehydes, aliphatic ketones, alkanes, alkenes, aromatic hydrocarbons and CO2. The composition of gaseous products changes significantly with the increase of temperature. The pyrolysis process can be divided into three stages. The first stage is ascribed to the breakage of C-O bond between the glycerol backbone and the fatty acid chain to form diacylglycerols, monoglycerides, fatty acids and aliphatic aldehydes. The second stage is attributed to the cleavage of C-O and C-C bond of ester compounds and fatty acids derived from the first stage to release fatty acids, aliphatic aldehydes, aliphatic ketones, alkanes, alkenes and CO2. The third stage is the volatilization of fatty acids and the production of alkanes, alkenes and CO2 through the decarboxylation of fatty acids and the formation of aromatic hydrocarbons through Diels-Alder reactions between conjugated dienes and substituted alkenes.