Study On The Synthesis Of P-Hydroxyacetophenone

P-hydroxyacetophenone(p-HAP)is an important organic chemical raw material,mainly used in medicine and spices industries.At present,the industrial synthesis of p-HAP is mainly used phenol as the raw material,then both Friedel-Crafts acylation of phenol and Fries rearrangement of phenyl acetate are pathways for its preparation.The acylation reagents used are generally acetic anhydride,acrtyl chloride,etc.And anhydrous AICl3 used as the Fries rearrangement catalyst.In this process,the acylation reagents’ ues are limited and may cause environment pollution,the strong Lewis acid catalysts are comsumption,highly corrosive,produce many by-products,and are difficult to separate from the reaction system.Later,the ues of solid acid catalysts may also has problems,such as low activity and deactivation of poisoning.Therefore,exploring a green-economy p-HAP syhthesis route and seeking high activity and environment-friendly catalysts have an important significance.In this thesis,we report a proposes route for the synthesis of PA from the O-acylation for the phenol react with acetic,and Frie rearrangement of PA to synthesize p-HAP.The better catalyst of these two steps were selected,suitable process conditions were obtained,and the reaction mechanism was discussed.The main contents are as follows:1.ZSM-5 zeolite catalysts catalyze oxyacylation of phenol.The catalytic activities of the Na+,H+ and alkali-modified ZSM-5 zeolite catalysts were compared,and the catalysts were characterized.The 60-1HZSM-5 zeolite catalyst was selected due to its specific surface area,pore volume,crystallinity and acid content.The conversion was 72.72%,the selectivity was 72.94%,and the yield was 53.04%under the optimized operating conditions determined by single factor experiments,which the reflux and water separation device was used.The yield decreases after the catalyst reused three times was obviously,to 7.84%.The mechanism of O-acylation for the phenol catalyzed by the 60-1HZSM-5 zeolite catalyst was discussed,it was considered that the reaction was completed through the addition-elimination process.In the nuclear addition reaction,the carbonyl carbon atom which activated by catalyst was reacted with the phenol,which was play as a nucleophile,the formed tetrahedral positive ion intermediate removes one molecule of water and finally forms PA.2.The HClO4-silica gel catalyst catalyzes the PA Fries rearrangement reaction.The catalytic activities of different supported solid acid catalysts for Fries rearrangement of PA were compared in liquid and gas phase reaction systems,and the catalysts were characterized.The HClO4-silica gel catalyst was selected due to its specific surface area,pore volume,crystallinity and acid content.The conversion was 77.83%,the selectivity was 25.80%,and the yield was 20.08%under the optimized operating conditions determined by single factor experiments,which the hydrothermal synthesis reactor was used.After reuse of the catalyst 3 times,it was found that the yield of the cyclohexane-treated catalyst was 4.7 times higher than that of the untreated catalyst,which was 10.21%.Comparision of Fries rearrangement after acylation and one pot synthesis of product on the yield,which show that the former was higher than the later,and the total yield was 14.27%,indicating that the formation of para-position products is favored under low temperature conditions.The mechanism of Fries rearrangement of PA in the hydrothermal synthesis reactor was discussed,it was considered that it is a mechanism involving carbocation,and the solvent with high polarity has obvious promotion effect on PA protonation and carbon-oxygen bond cleavage process.Both intramolecular and intermolecular reactions occured during the reaction.3.The HClO4-silica gel catalyst catalyzes the PA Fries rearrangement reaction under microwave irradiation.To shorten the reaction time and increase the selectivity of the reaction,PA Fries rearrangement reaction was investigated by microwave irradiation.The reaction temperature,reaction time,catalyst dosage and microwave power were determined by using L9(43)orthogonal table.The optimized operating conditions of Frie rearrangement of PA were determined by using orthogonal experiments,the conversion was 45.32%,the selectivity was 63.50%,and the yield was 28.78%.Further validation tests show that using a microwave reactor can significantly shorten the reaction time and increase product selectivity.The above experimental results in this paper provide an important reference for optimizing the synthesis route of p-HAP.