Improvement of the unit for obtaining a commercial product of the para-tertiary butylphenol synthesis unit

Industrial synthesis of para-tertiary butylphenol is carried out by alkylation of phenol with isobutylene on Amberlyst 36 Dry, Amberlyst 36 Wet Resin or KU-23 catalysts. In addition to the target product of para-tertiary butylphenol, unreacted phenol and by-products are present in the alkylation reaction mass, therefore, the technological scheme provides for their separation, recycling of phenol into the reaction unit and obtaining commercial para-tertiary butylphenol in the form of distillate of the K-148 column with the return of the cubic residue to the reactor. The cubic residue contains para-tertiary butylphenol, 2,4-di-tert-butylphenol and high-boiling products. In order to assess the principal possibility of organizing an effective and clear separation of the cubic residue of the K-148 column into the target para-tertiary butylphenol and the stream recycled into the alkylation reactor for the disproportionation of the 2,4-di-tert-butylphenol by-product into the target product, a study of the operation of the K-148 industrial column was performed. Using industrial data from the operation of the para-tertiary butylphenol synthesis plant in the Honeywell UniSim Design modeling software environment, a model of the alkylate separation unit and the production of commercial para-tertiary butylphenol was developed. The NRTL method was used as a mathematical package for calculating the thermodynamic properties of process flow components. The adequacy of the technological scheme model is confirmed by comparing the calculated values with industrial data. The component composition of alkylate contains phenol, para-tertiary butylphenol, ortho-tertiary butylphenol, 2,6-di-tert-butylphenol, 2,4-di-tert-butylphenol, 2,4,6-tri-tert-butylphenol and high-boiling products. The analysis of the technological flows of the K-148 column showed that the cubic residue of the column recycled into the alkylation reactor contains up to 96% by weight. the target para-tertiary butylphenol, the flow of which into the reactor leads to a decrease in the useful reaction volume of the apparatus, and at the same time, it is of practical interest to assess the possibility of isolating high-quality target para-tertiary butylphenol from the cubic residue of the K-148 column. For this purpose, a variant of changing the technological scheme of the process with the inclusion of an additional distillation column PK-1-2 is proposed. Estimates of the technological and structural parameters of the PK-1-2 column calculated by the model showed that the stream selected as distillate contains 99.92% by weight. the target para-tertiary butylphenol, which is about 8.8% of the amount of the target product taken from the top of the K-148 column. At the same time, a decrease in the amount of para-tertiary butylphenol in the cubic residue of the PK-1-2 column provides an increase in the use of the volume of the alkylation reactor by 1.7%. The research results and the model can be used to optimize technological modes and evaluate the design parameters of mass transfer devices of the scheme, as well as to train technologists in the techniques of qualified process management.