Study On Green Synthesis Process Of 2-Amino-2-Methyl-1-Propanol

2-Amino-2-methyl-1-propanol（AMP）is one of the few industrial amines with low molecular weight and high alkalinity.It is widely used in various fields such as coatings,metal processing,adhesives,ink,rubber,personal care,water treatment,and so on.With the continuous development of the national economy,the use and consumption of AMP will increase year by year in the future,with good application prospects.In recent years,with the enhancement of people’s awareness of environmental protection and the proposed goal of"carbon neutrality and carbon compliance"in China,traditional AMP preparation processes do not meet the development trend of green chemistry and chemical engineering due to their high pollution and high energy consumption.Looking for a simple process,low production cost,environmentally friendly,low-carbon green,and sustainable AMP preparation process has become a key node in the industry’s development.In response to a series of bottlenecks that have plagued the development of the industry in traditional processes,such as the dangerous and complex process,the difficult source of raw materials,the difficult separation process,and the low yield of selective hydrogenation,this article focuses on the improvement and optimization of the traditional process of AMP,focusing on the three key links in the AMP process:ammoximation oxidation reaction,hydroxymethylation reaction,and nitro hydrogenation reaction,as well as the corresponding high activity Key units such as high selectivity and green catalyst preparation not only improve product yield,but also shorten the process flow of AMP preparation,greatly reducing problems such as excessive energy consumption and serious environmental pollution in traditional processes.The research and development of this technology is of great significance to the application and promotion of the industrialization of AMP series products in China.The main research contents of this article are as follows:1.Due to the limitation of the source of nitropropane in the AMP preparation process,we studied the reaction of acetone ammoximation oxidation to prepare 2-nitropropane.Firstly,in order to compensate for and avoid errors caused by changes in matrix composition,gas and auxiliary gas flow rates,surface tension,and absorption speed,and improve the accuracy of analysis,we use the internal standard method to analyze the material content;Secondly,based on the establishment of accurate analytical methods,the reaction conditions such as the amount of catalyst,reaction temperature,and material ratio in the process of preparing 2-nitropropane by ammoximation and oxidation of acetone were optimized.The optimal process was determined as follows:reaction temperature 70°C,feed time 1.5 h,n（H₂O₂）:n（acetone）=2.3:1,n（ammonia）:n（acetone）=1.2:1,and the amount of catalyst used was 20%of the mass of acetone.Under these conditions,the conversion of acetone was96.2%,and the selectivity of 2-nitropropane was 95.8%.Finally,an industrial process simulation of the distillation process of the reaction liquid was conducted using Aspen Plus software.2.In order to solve the problems of difficult separation of liquid alkali in the hydroxymethylation reaction unit in the AMP preparation process,which leads to environmental pollution,a Ca-Al-LDHs solid base catalyst with different calcium aluminum ratios was prepared by coprecipitation method and used for the heterogeneous catalytic hydroxymethylation of 2-nitropropane to prepare 2-nitro-2-methyl-1-propanol.According to comparative experiments,solid base catalysts exhibit good catalytic activity for the condensation of 2-nitropropane and formaldehyde when Ca/Al=1:1;The structure and performance of Ca-Al-LDHs solid base catalyst were characterized by SEM,XRD,FT-IR,and CO₂-TPD.The results showed that the catalyst had a typical LDHs structure,and the lattice structure of Ca₁₂Al₁₄O₃₃,as the main catalytic active center,enhanced the surface basicity of the catalyst and improved its catalytic activity.The structure-activity relationship between catalyst composition and catalytic activity was further studied,and the process conditions for the green catalytic synthesis of 2-nitro-2-methyl-1-propanol using solid base were optimized.The optimal conditions were:reaction temperature 70°C,reaction time 2h,n（formaldehyde）:n（2-nitropropane）=2:1,and the amount of catalyst used was 30%by mass of formaldehyde.Under these conditions,the conversion of 2-nitropropane was 96.2%,and the selectivity of 2-nitro-2-methyl-1-propanol was 99%,The total yield reached 95.24%;Finally,the life of the catalyst was evaluated,and the yield of the catalyst can still reach over 60%after 20 times of repeated use.The reason for catalyst deactivation was analyzed through characterization,and it was found that the loss of basic sites was the main reason for catalyst deactivation.Finally,the mechanism of hydroxymethylation under alkaline conditions was explored.3.The nano palladium catalyst supported on coconut shell activated carbon was prepared by ultrasonic assisted reduction method,which made the nano Pd particles on its surface smaller and more evenly dispersed,and improved its reaction activity.It was applied to the reaction of nitro hydrogenation to AMP.The process conditions for the preparation of AMP by palladium carbon catalyzed nitro hydrogenation were optimized.The optimal process conditions were determined as follows:reaction temperature 60°C,reaction pressure 1.5 MPa,in cyclohexane solvent,The amount of catalyst used was 5%of the mass of the raw material.After 3 hours of reaction under this condition,the conversion of 2-nitro-2-methyl-1-propanol was 98.43%,the selectivity of AMP was 99.14%,and the overall yield reached 97.58%.Comparative experiments were conducted on the reaction conditions of N-methylation reaction,and the range of process conditions for inhibiting side reactions was obtained:the amount of alkali was controlled to within 0.5%of the mass of the raw material,the reaction temperature was below 80°C,and the reaction time was within 6 hours.Within this range of process conditions,the N-methylation reaction can be effectively inhibited,thereby ensuring a high yield of nitro hydrogenation and the efficiency of preparing AMP.