Research And Discussion On Quality Control Of Pentaerythritol Production Process Based On Near Infrared Technolog

At this stage,the production of pentaerythritol at home and abroad mainly uses alkali as a catalyst to catalyze the reaction of methanal and ethanal to cannizzaro.The process is mature,simple to operate,and does not have high requirements for equipment,but there are many side reactions,resulting in low yield of pentaerythritol.Near infrared spectrum analysis technology is one of the most widely used technology at present,it can realize online analysis of the whole production process.In this paper,a quantitative analysis model of pentaerythritol and its by-products sodium formate and dipentaerythritol in the production process was established by using near infrared analysis technology,which can realize the characteristics of online monitoring,combined with stoichiometry,so as to realize online monitoring of the production process and timely obtain the content changes of products and their by-products in the reaction process.The main results are shown below.（1）In this paper,caustic soda flakes was used as a catalyst and methanal and ethanal were used as semifinished materials to synthesize pentaerythritol.The effect of various possible experimental factors on the content of pentaerythritol produced by the reaction was investigated.The results showed that the yield of pentaerythritol would gradually increase with the rising of reaction time and feeding time within a certain reaction time and feeding time,and then gradually decrease with the increase of reaction time and feeding time;the reaction temperature and material molar ratio also showed this pattern.The maximum yield of pentaerythritol was determined for a reaction time of 100 min,a molar ratio of n（methanal）:n（ethanal）:n（alkali）=5.5:1:1.2,a feeding time of 80 min and a reaction temperature of 45°C.（2）After single-factor experimental investigation,it can be obtained that the influence of feeding time and sodium hydroxide dosage is small,so the response surface experiment only considers three factors:reaction time,reaction temperature,n（methanal）:n（ethanal）.The three reaction conditions were experimentally tested with the response surface:the established regression model was extremely significant,with high fit,good accuracy and predictability,which could be used to predict the yield of pentaerythritol.The three reaction conditions affected the yield of pentaerythritol significantly:response time>response temperature>molar ratio of the material.The best reaction conditions for the production of pentaerythritol by the Response Surface were as follows:response time 96.73 min,response temperature 45.48°C,n（formaldehyde）:n（acetaldehyde）=5.55,and the predicted yield of pentaerythritol under best conditions was 93.21%.（3）A quantitative detection method for products and substances resulting from their side reaction in the synthesis of pentaerythritol（HPLC）was created,and the methodological research of the method indicated that the accuracy of the method was high,and the content of products and by-products in the synthesis process of pentaerythritol could be accurately determined.（4）Using the pure pentaerythritol product as the research object,the influence of various factors on the established model was investigated.Taking the RMSEC,RMSEP and R as the evaluation index,the optimal scanning number was finally determined to be 64,the spectral resolution was 8 cm^-1,the spectral preprocessing method was MSC+F-D+N-s combination,the modeling band was 7082.52 cm^-1～4081.20 cm^-1,the modeling method was PLS,and the best factor digit was 2.The quantitative correction model of pure pentaerythritol is stable and reliable,and the content of pure pentaerythritol can be predicted by this model.（5）By establishing a near-infrared quantitative analysis model of the product and its by-products in the process of pentaerythritol synthesis,the synthesis process of pentaerythritol can be monitored online,and the quality and efficiency of the production of pentaerythritol can be improved.The effects of modeling band,spectral preprocessing method,modeling method and model principal factor number on the model of related substances were investigated,and the model was evaluated by using specificity,linearity and other evaluation.The results show that the three quantitative analysis models established are stable and reliable,which can predict the content of pentaerythritol synthesis products and by-products,and realize the online monitoring of the synthesis process of pentaerythritol.