Study On Refining Of Low-Boiling Phenols In Low Temperature Coal Tar

China is rich in low-temperature coal tar resources,which contains about 30 wt% phenolic compounds.Phenolic compounds are important intermediates of chemical products with a wide range of industrial applications.Currently,there is a large gap in the phenolic market in our country.The research on the extraction and refining of phenolic compounds in low-temperature coal tar is in line with the national energy strategy needs and has very important economic and social benefits.In this paper,the crude phenols extracted from low-temperature coal tar were used as the research object,and the research was conducted from two aspects: crude phenols pretreatment and low-boiling phenols refining.The solvent extraction method was used to remove the neutral oil from the crude phenols,and the type of extractant,the extraction temperature,and the number of extraction stages on the neutral oil extraction rate and phenol entrainment rate were mainly investigated.The results show that when the solvent S07 is the extractant,the extraction temperature is 30℃,and the number of extraction stages is 6,the total extraction rate of neutral oil reaches 70.81%,and the extraction effect is the best at this time.The acid-base method was used to recover the crude phenols entrained in the neutral oil removal process,and alkali washing temperature,alkali concentration,and alkali washing times on the recovery of crude phenols were investigated.The results show that when the alkali washing temperature is 60℃,the alkali concentration is20 wt% Na OH solution,and the number of alkali washing is 3 times,the total recovery rate of crude phenols can reach 94.08%.The acid refining method was used to remove pyridines in crude phenols,and the type of acid refined preparation,acid concentration,reaction temperature,reaction time,agent-oil mass ratio,and reaction order on the removal effect of pyridine were investigated.The results show that when sulfuric acid is selected as the acid essence preparation,the concentration of sulfuric acid solution is 20 wt%,the reaction temperature is 30℃,the reaction time is 10 minutes,the single-stage agent-oil mass ratio is 0.5:1,and the reaction order is 3,the effect of removing pyridine is the best.At this time,the total removal rate of pyridine is 96.67%.The pretreated crude phenols were separated and refined by the vacuum distillation method,and the theoretical plate number of the packed distillation column was determined to be 49.The composition of crude phenols after pretreatment was analyzed by GC-MS,and the content of phenolic compounds could reach 91.32 wt%.The influence of operating pressure and reflux ratio on the purity and yield of the target product was investigated.The results show that the operating pressure of the rectification tower is 5 k Pa,and the reflux ratio during the separation of phenol,o-cresol,and m-cresol is 25,16,and 10 respectively,and the separation effect is better at this time.Under these conditions,intermittent vacuum distillation was performed.The purity of the three low-boiling phenol products were 64.45 wt%,48.49 wt%,and 71.85% by weight respectively,and the yields were 85.52%,56.84%,69.62%,and the total yield was 68.08%.The purity of the top product is limited by factors such as tower efficiency.Increasing the number of theoretical plates can significantly improve the product purity.