Application of two morphologies of MnO for efficient catalytic -methylation of 4-chlorophenol.

Vapor phase -methylation of 4-chlorophenol with methanol was studied over MnO catalyst with two kinds of morphologies. Here, MnO was prepared by a precipitation and hydrothermal method, and showed the morphology of nanoparticles and nanowires, respectively. XRD characterization and BET results showed that, with the increase of calcination temperature, MnO had a higher crystallinity and a smaller specific surface area. N adsorption/desorption and TPD measurements indicated that MnO nanowires possessed larger external surface areas and more abundant acid and base sites. Simultaneously, in the fixed bed reactor, methanol was used as the methylation reagent for the -methylation reaction of 4-chlorophenol. XRD, XPS, TG-MS and other characterizations made it clear that methanol reduced 4-chlorophenol and its methide, which were the main side-reactions. And Mn was reduced to Mn under the reaction conditions. Changing the carrier gas N to a H/Ar mixture further verified that the hydrogen generated by the decomposition of methanol was not the reason for dechlorination of 4-chlorophenol compounds. Here we summarized the progress of 4-chlorophenol methylation based on the methylation of phenol. Also, we proposed a mechanism of the 4-chlorophenol dechlorination effect which was similar to the Meerwein-Ponndorf-Verley-type (MPV) reaction. The crystal phase and carbon deposition were investigated in different reaction periods by XRD and TG-DTA. The reaction conditions for the two kinds of morphologies of the MnO catalyst such as calcination temperature, reaction temperature, phenol-methanol ratio and reaction space velocity were optimized.