【作者】 潘琦；

【导师】 钱超；

【作者基本信息】 浙江大学 ， 化学工程（专业学位）， 2019， 硕士

【摘要】 Kolbe-Schmitt反应作为一种合成羟基苯甲酸类化合物的经典反应,具有原子利用率高,三废少,成本低廉的优点。文献报道的Kolbe-Schmitt反应工艺一般是将二氧化碳与酚的碱金属盐进行气固相反应。但此类气固反应存在着诸多问题:1)酚的碱金属盐粉末容易发生自燃,危险性高;2)反应传热差、产物易结焦,导致目标产物收率较低。所以,探索出一条更加安全、高效的Kolbe-Schmitt反应工艺十分重要。本文首先以苯酚为原料,采用气固法的Kolbe-Schmitt反应工艺合成邻羟基苯甲酸,优化后的反应条件为:所用碱为NaOH,温度120℃,反应压力1.5MPa,反应时间9h,使用螺带搅拌桨,苯酚的转化率达到63.1%,邻羟基苯甲酸的选择性达到95.4%。实验过程中的主要问题有:1)苯酚钠粉末转移时会发生自燃;2)需要专门的异构件来促进气固反应的传质;3)釜内受热不均,产物易结焦。为了解决上述问题,本文提出了溶剂法Kolbe-Schmitt反应的方案,并将该方案用于合成附加值更高的3,5-二叔丁基-4-羟基苯甲酸。并在之后以3,5-二叔丁基-4-羟基苯甲酸为原料,合成本文的目标产物3,5-二叔丁基-4-羟基苯甲酸正十六酯。采用溶剂法Kolbe-Schmitt反应,以2,6-二叔丁基苯酚为原料,甲苯为溶剂,合成3,5-二叔丁基-4-羟基苯甲酸。优化后的反应条件为:所用碱为KOH,温度130℃,反应压力2.5MPa,反应时间7h,溶剂为甲苯,溶反比5:1的条件下,2,6-二叔丁基苯酚的转化率达到48.1%,3,5-二叔丁基-4-羟基苯甲酸的选择性接近100%。相对于气固法,溶剂法Kolbe-Schmitt具有明显的优点:1)避免了 2,6-二叔丁基苯酚钾的自燃;2)无需采用异构件;3)反应时受热均匀,提高了产物的品质。通过在反应中添加用量为原料60%(mole)的促进剂2,6-二叔丁基-4-甲基苯酚的钾盐,成功将原料转化率由48.1%提高到66.2%,促进剂可以回收重复利用,小试回收率达97%。完成合成实验后,本文对添加促进剂提高反应转化率的现象做出了解释:2,6-二叔丁基-4-甲基苯酚钾首先与二氧化碳反应得到相应的络合物,该络合物会进攻2,6-二叔丁基苯酚钾的对位氢,最终得到3,5-二叔丁基-4-羟基苯甲酸的二钾盐与2,6-二叔丁基-4-甲基苯酚。据此,本文推测了一种可能的Kolbe-Schmitt反应机理:对于苯酚钾盐类进行Kolbe-Schmitt反应形成对羟基苯甲酸类化合物时,一分子的苯酚钾盐首先与二氧化碳形成络合物,之后会进攻另一分子的苯酚钾盐的对位氢,最终生成一分子的对羟基苯甲酸二钾盐类化合物与一分子的酚,因此苯酚钾盐类进行Kolbe-Schmitt反应的极限转化率为50%(以苯酚类计)。对于苯酚钠类进行Kolbe-Schmitt反应生成邻羟基苯甲酸类化合物时,酚钠在形成络合物后会发生分子内反应,进攻邻位氢,最终生成单钠盐,故而转化率可以突破50%。之后,本文研究了以3,5-二叔丁基-4-羟基苯甲酸和正十六醇为原料合成3,5-二叔丁基-4-羟基苯甲酸正十六酯的过程。优化后的反应条件为:一水合对甲苯磺酸为催化剂,催化剂用量为酸的23%(mole),醇:酸=1.5(mole),甲苯为反应溶剂,反应时间为6h,反应的转化率达99.9%,目标产物的选择性达到99.2%。根据小试实验的结果,本文完成了 一套以2,6-二叔丁基苯酚为原料年产100吨3,5-二叔丁基-4-羟基苯甲酸正十六酯的中试装置流程设计,其中生产3,5-二叔丁基-4-羟基苯甲酸的工艺是添加促进剂的溶剂法工艺。设计完成了流程的物料衡算,绘制了工艺流程图与带控制点的工艺流程图,编写了装置的操作流程,为工艺的工业化提供了参考依据。更多还原

【Abstract】 Kolbe-Schmitt reaction as a classical reaction for the synthesis of hydroxybenzoic acid compounds,has the advantages of high atomic utilization,low waste,and low cost.Kolbe-Schmitt reaction process reported in the literature generally involves a gas-solid phase reaction of carbon dioxide with an alkali metal salt of a phenol.However,there are many problems in such gas-solid reaction:1)The alkali metal salt powder of phenol is prone to spontaneous combustion and has high risk;2)the reaction heat transfer is poor,and the product is easy to coke,resulting in low yield of the target product.Therefore,it is important to explore a safer and more efficient Kolbe-Schmitt reaction process.In this paper,phenol was used as raw material to synthesize o-hydroxybenzoic acid by gas-solid Kolbe-Schmitt reaction.The optimized reaction conditions were as follows:the base used was NaOH,the temperature was 120℃,the reaction pressure was 1.5 MPa,the reaction time was 9 h,and the snail was used.With a stirring paddle,the conversion of phenol reached 63.1%,and the selectivity of o-hydroxybenzoic acid reached 95.4%.The main problems in this experiment are:1)spontaneous combustion occurs when sodium phenolate powder is transferred;2)special gas-solid stirring paddle is needed to promote mass transfer of gas-solid reaction;3)uneven heating in the kettle,the product is easy to coke.In order to solve the above problems,a scheme of the solvent method Kolbe-Schmitt reaction was proposed,and the scheme was applied to synthesize a higher added value of 3,5-di-tert-butyl-4-hydroxybenzoic acid.Then,3,5-di-tert-butyl-4-hydroxybenzoic acid was used as a raw material to synthesize the target product,n-hexadecyl 3,5-di-tert-butyl-4-hydroxybenzoate.The solvent method Kolbe-Schmitt reaction was used to synthesize 3,5-di-tert-butyl-4-hydroxybenzoic acid using 2,6-di-tert-butylphenol as a raw material and toluene as a solvent.The optimized reaction conditions were as follows:the base used was KOH,the temperature was 130℃,the reaction pressure was 2.5 MPa,the reaction time was 7 h,the solvent was toluene,and the conversion ratio of 2,6-di-tert-butylphenol was 5:1.Up to 48.1%,the selectivity of 3,5-di-tert-butyl-4-hydroxybenzoic acid was close to 100%.Compared with the gas-solid method,the solvent method Kolbe-Schmitt has obvious advantages:1)avoiding spontaneous combustion of potassium 2,6-di-tert-butylphenol;2)eliminating the need for a gas-solid stirring paddle;3)heating evenly during the reaction to improve the quality of the product.By adding a potassium salt of the promoter 2,6-di-tert-butyl-4-methylphenol as accelerator in an amount of 60%by mole to the reaction,the conversion of the raw material was successfully increased from 48.1%to 66.2%.The accelerator can be recycled and reused,and the experiment recovery rate is 97%.After the completion of the synthesis experiment,this paper explained the phenomenon of adding a promoter to increase the conversion rate of the reaction:2,6-di-tert-butyl-4-methylphenol potassium was first reacted with carbon dioxide to obtain the corresponding complex,and then the complexation attacked the para-hydrogen of 2,6-di-tert-butylphenol potassium to finally obtain the dipotassium salt of 3,5-di-tert-butyl-4-hydroxybenzoic acid and 2,6-di-tert-butyl-4-methyl phenol.Based on this,this paper speculated a possible Kolbe-Schmitt reaction mechanism:when a Kolbe-Schmitt reaction is carried out to form a p-hydroxybenzoic acid compound,one molecule of phenol potassium salt first forms a complex with carbon dioxide,after which it will attack the para-hydrogen of another molecule of phenol potassium salt,and finally produce one molecule of dipotassium p-hydroxybenzoate and one molecule of phenol,so the limit conversion of Kolbe-Schmitt reaction of phenol potassium salt is 50%(based on phenols).When the Kolbe-Schmitt reaction is carried out to form an o-hydroxybenzoic acid compound,the sodium phenolate undergoes an intramolecular reaction after forming a complexation,attacks the ortho hydrogen,and finally forms a monosodium salt,so the conversion rate can exceed 50%.Then,the process of synthesizing 3,5-di-tert-butyl-4-hydroxybenzoic acid n-hexadecyl ester from 3,5-di-tert-butyl-4-hydroxybenzoic acid and hexadecanol was studied.The optimized reaction conditions were as follows:p-toluenesulfonic acid monohydrate as catalyst,the amount of catalyst was 23%(mole)of acid,alcohol:acid=1.5(mole),toluene was the reaction solvent,reaction time was 6h,reaction conversion rate up to 99.9%,the selectivity of the target product reached 99.2%.According to the results of the pilot test,a pilot plant with an annual output of 100 tons of 3,5-di-tert-butyl-4-hydroxybenzoic acid n-hexadecyl ester using 2,6-di-tert-butylphenol as raw material was completed.The process design where in the process for producing 3,5-di-tert-butyl-4-hydroxybenzoic acid was a solvent process in which a promoter was added.The material balance of the process was designed,the process flow diagrams and the piping&instrument diagrams were drawn,and the operation flow of the devices was written,which provided a reference for the industrialization of the process.更多还原