Study On Catalysis In Synthesizing Hydroxypivalic Acid Neopentyl Glycol Monoesters

The catalysis on synthesis of Hydroxypivalic acid neopentyl glycol monoesters?HPN?was researched in this paper.The process included aldol condensation of iso-butyraldehyde?IBD?and formaldehyde?FA?and disproportionation of 2,2-dimethyl-3-hydroxy propionaldehyde?HPA?to HPN.In this paper,the best catalyst for the aldol condensation had been studied.The optimum reaction conditions were obtained by single-factor experiments.The results showed that the conversion of IBD reached 98%and the selectivity of HPA reached 98%in the condensation of IBD and FA under the following reaction conditions:reaction temperature 75?,reaction time 3 h,TEA as catalyst and n?IBD?:n?FA?:n?TEA?=1:1.07:0.06;both the conversion of HPA and the selectivity of HPN reached 98%in the disproportionation of HPA under the following reaction conditions:reaction temperature 90?,reaction time 90 min,Mg?tactac?₂ as catalyst,catalyst dosage 0.05%.The structure of obtained product was characterized by IR.The above-mentioned homogeneous catalyst of disproportionation was immobilized on different supports,and the catalytic activity of immobilized catalyst was investigated.The results showed that the best support for the homogeneous catalyst was silica.In the process for the preparation of HPN which employed HPA as raw materials,the conversion of HPA and the selectivity of HPN reached 97%under the optimum reaction conditions:reaction temperature 90?,reaction time 90 min.The dosage of supported Mg?tactac?2/SiO2 was 0.5%.Using supported MgO/SiO₂ as the catalyst of disproportionation,the results showed that the conversion of HPA reached 91%and the selectivity of HPN reached97%under the optimum reaction conditions:reaction temperature 90?,reaction time90 min.The dosage of supported MgO/SiO₂ was 3%.The yield of HPN reached 80%.The supported catalysts were characterized by IR,BET and SEM.The experiments showed that the above-mentioned catalyst could easily be filt after the reaction.The supported MgO/SiO₂ catalyst could be reused up to 4 times with no apparent decrease in the conversion of HPA and yield of HPN.