Research on separation of biphenylcarboxylic acid isomers by inclusion isolation method

The inclusion isolation method was used to separate the isomers of 4-biphenylcarboxylic acid and 3-biphenylcarboxylic acid by taking β-cyclodextrin(β-CD) as host.The influence of heating temperature,stirring time,inclusion time and material ratio on the separation results was studied respectively.The stirring time is defined at 2.5 h and the heating temperature is controlled at 60-70 ℃.Orthogonal test shows that molar ratio of β-CD to biphenylcarboxylic acid is the most important factor to influence the yield and selectivity of 4-biphenylcarboxylic acid.The best separation conditions are as follows: molar ratio of β-cyclodextrin to biphenylcarboxylic acid is 1∶2,heating temperature is 60 ℃,stirring time is 2.5 h,and inclusion time is 2 d.Under these conditions,the separation result is the best.The yield of 4-biphenylcarboxylic acid can reach 35.47%,and the purity can reach more than 99%.