Development Of Phenoxyacetic Acid Synthesis In A Environmental Benign Tolal-cycling Process

Phenoxyacetic acid is a kind of important chemical and pesticide intermediate. Its chloride product,2,4-dichlorophenoxyacetic acid(trade name is2,4-D) has been used for nearly70years as chemicalherbicide. Its safety and efficacy makes these drugs is irreplaceable in the foreseeable short time. But the lack-developed technology leads their shortages of low-rate production, bad selectivity, serious pollution and so on. It caused serious environmental problems. Thus, developing an environmentally friendly new production process can reduce consumption and emission, and also can reduce the cost.The main content of the research is focused on the chloroacetic acid hydrolysis and synthesis of phenoxyacetic acid using kinetics theory to determine pH variation. Simple, efficient and environmentally friendly synthetic methods is established by the rational design of chemical processes and experimental verification.Our developed research process route is as follows:chloroacetic acid was neutral-lized by sodium carbonate to produce sodium chloroacetate. Sodium chloroacetate and phenol can generate sodium phenoxyacetate by condensation reaction in organic-water two-phase system. Clean phenoxyacetic acid can be obtained by acidification and crystallization. Its yield is97%in terms of phenol. The features of the present study is the high yield, less wastewater, and less content of phenol in the wastewater. Deep investigation also had been made according to the problems by recycling the phenol with distillation tower out of the wastewater in high concentrated salt. The phenol can be recycled more than95%. The phenol content in the wastewater can be treated to less than10ppm under optimized conditions.The experiments indicated that excessive use-recycle of phenol was adopted in synthesizing phenoxyacetic acid. via investigation on the influence of pH, solvent, temperature and phenol dosage, the yield of sodium phenoxyacetate which was the product of the first stage reached to99%. the total yield of phenoxyacetic acid was over97%.2,4-dichlorobenzene oxygen acetic acid can be generated by chlorination of phenoxyacetic acid in some kind of solvents. The total yield is95%in terms of phenol. Distillation method can well recycle the phenol in phenolic wastewater.