mbf not only does this result in a loss of phenol but as can be seen the time necessary to reduce the mbf content to near 0 ppm by weight is extended significantly approximately 130 minutes fig4 illustrates an example where the higher boiling compounds formed by treatment with acidic resin are removed by flash distillation of the phenol prior to acidic resin treatment at elevated temperature to remove mbf as can be seen in fig4 no increase in mbf content is experienced further the mbf content is reduced to near 0 ppm in about 10 minutes as opposed to 130 minutes in an alternative embodiment of the invention a distilled phenol stream containing acetol is heated in a closed system at elevated temperature to convert acetol to higher boiling compounds other than mbf the heat treatment may be carried out with or without the addition of a small amount of caustic if the heat treatment is carried out without the addition of caustic the ph of the phenol stream should be above 2 preferably above 2 5 in general this is the ph of the distilled phenol stream from the neutralized reaction product lower ph may lead to additional amounts of mbf the caustic is preferably added as a concentrated solution e g 50 percent by weight again the phenol is separated from the higher boiling compounds via distillation the temperatures used.