Alkylation of xylenes with methanol on alumina activated with hydrofluoric acid.

The catalytic alkylation of xylenes with methanol over alumina activated with hydrofluoric acid was examined using a flow reactor under the atmospheric pressure. The methylation takes place from 300°to 500°in the presence of an excess amount of methanol. At temperatures from 300°to 350°isomerization and disproportionation are not observed. The selectivity of the methylating position was correlated with the nature of the catalyst such as acidity, acid strength, and the structure of fluorinated alumina catalysts. The activity showed a maximum for 12.7% fluorinated alumina catalyst and conversion increased with the acidity of catalysts. The acid strength determined by the indicator method falls in the range of +1.5≤H0≤3.3, which suggests that the acid sites have a uniform structure on its surface. From the X-ray powder patterns of the catalysts used the active species were proposed to be AlF (OH)2 and AlF2 (OH).