Effects of oxygen-containing substituents on pyrolysis characteristics of β-O-4 type model compounds

Abstract

In order to uncover the influence of oxygen-containing functional groups on the pyrolysis characteristics of β-O-4 type model compounds, in-situ diffuse reflectance infrared pyrolysis and pyroprobe-GC–MS were used to study the migration patterns of functional groups and the specific pyrolysis product distributions with changing temperature. The results showed that the initial temperature of phenolic hydroxy production was 300°C, and peaks corresponding to this increased gradually in intensity in 1-benzyl-2-(2-methoxy-phenol)-ethanol, while this product did not begin appearing until 600°C in 1-ethyl-benzene-2-(2-methoxy-phenol). The intensities of the CH4 peaks were similar in all three samples, but the CO2 absorption peak was significantly lower in 1-(4-methoxy-phenoxy)-2-(2-methoxy-phenol)-ethanol. In addition, α-OH was found to promote the generation of aryl-ketone products. The 4-methoxy-styrene contents of 1-ethyl-benzene-2-(2-methoxy-phenol) and 1-(4-methoxy-phenoxy)-2-(2-methoxy-phenol)-ethanol at 500°C were 36.1% and 31.3%, respectively, higher than the styrene content of 1-benzyl-2-(2-methoxy-phenol)-ethanol (26.3%). The content of acetophenone was only 0.3% in 1-ethyl-benzene-2-(2-methoxy-phenol), but the yields of acetophenone and 4-methoxy-acetophenone were 16.7% and 19.6% in 1-benzyl-2-(2-methoxy-phenol)-ethanol and 1-(4-methoxy-phenoxy)-2-(2-methoxy-phenol)-ethanol, respectively.