Preparation And Application Of The Solid Acid Ester Catalyst

As we all know, organic carboxylic acid ester is an important class of fine organic chemical products which was mainly used in solvents, plasticizers, resins, paints, cosmetics, pharmaceuticals, surface active agent in organic synthesis industry . Therefore, the esterification reaction as synthesis of organic intermediates, raw materials and an important way. People trying to develop the ideal new ester synthesis catalyst, and expect to apply it to the industrial production.The traditional catalysts such as sulfuric acid, phosphoric acid and hydrofluoric acid catalytic effect due to its better catalytic activity for a wide range of advantages and has been widely used in fine chemical, petrochemical, pharmaceutical synthesis, and various specialty chemicals. But these catalysts were also exist organic carbon, the reaction selectivity, equipment corrosion, environmental pollution, the reaction difficult to control and post-processing complexity of such shortcoming. The reaction did not meet the "green" economic development of chemical and atomic concept.Compared with the traditional acid catalyst, the solid acid catalyst separation and recovery simple, easy activation of regeneration, high temperature stability, and ease of continuous operation and automation of chemical, corrosion, environmental protection, etc., show a broad application prospects. The new non-toxic and efficient catalyst for the process of production of "atom economy" of and raw materials "zero emissions " is currently one of the hot catalysis.In this paper, polystyrene/acrylic sodium (St/SAS) was prepared by emulsion polymerization method, and styrene (St) and propylene sulfonate (SAS) as the main monomers, potassium persulfate (K₂S₂O₈) as initiator, respectively. The solid acid catalyst materials polystyrene/acrylic acid (St/AS) was prepared by acidification of hydrochloric; The influence of monomer dosage, initiator dosage, reaction time, stirring rate was investigated by the orthogonal experiment and the combination of single-factor analysis Methods. The best solution to the polymerization reaction was determined.All the structures and performance tests were characterized by infrared (IR) spectroscopy, scanning electron microscopy (SEM), thermogravimetric differential thermal analysis (TG-DTA) and determination of total sulfur in the polymer material St/SAS. The results show that the benzene ring of St/AS were observed at 1650 cm^-1, 1600 cm^-1 and 691 cm^-1, 750 cm^-1 from IR spectrum of St/AS. And the characteristic absorption peak of sulfonic acid at the 1058 cm^-1 and 1180 cm^-1. It can be recognized from photos of SEM that the surface of St/AS was changed dramatically. The polymer material was small particles and uniform distribution; The results of TG-DTA show that the decomposition temperature of St/AS was high, and the solid acid catalyst St/AS did not break down under 300℃, and it can be used for high temperature catalytic reaction; The total sulfur content in the polymer St/AS was about 3.0%, The conversion rate of the SAS was relatively high. Compared with concentrated H₂SO₄, the amount of esterification yield was higher by St/AS as catalytic.The yield of ethyl acetate can reach 90% when the rection time was 50 min with the amount of St/AS 1.6 g, acetic acid 6 mL, ethanol 6 mL. The catalytic of St/AS can be repeated up to 10 or more of continuous use, and the yield of ethyl acetate also can maintain a high yield without reprocessing, above 72%. The esterification reaction of the product is simple with the St/AS as catalytic. The pH of ethyl acetate coarse product was 7 and shows neutral that the solid acid St/AS as catalyst. The reprocess of product was very simple and it needed not wash by saturated Na₂CO₃ solution. Chromatographic analysis showed that the ethyl acetate product was impurity which was synthesised by the solid acid catalyst St/AS. Therefore, it did not pollute the environment.When the amount of catalyst St/AS was 2.5 g; acid 7.5 mL, isoamyl alcohol 9 mL; reflux time 1.5 h, the yield of isoamyl acetate can be reach more than 92%. The reprocess of product was very simple and the product need not to remove the acid. The yield of isoamyl acetate can up to 86% after 5 times reuse with the drying St/AS. The products was colorless transparent liquid, and the refractive indexes was nD20 = 1.4032. The solid acid catalyst St/AS in the esterification reaction has a good catalytic performance, reuse, easy recycling and easy post-processing and other advantages. And the catalyst was environmentally friendly, green chemistry and environmental indicators; simple post-processing step, saving costs, and the catalyst was comply with the concept of green chemistry.The acetic anhydride and acetyl salicylic acid by the esterification reaction with the laboratory-made solid acid St/AS as a catalyst. The yield of acetyl salicylic acid 90% or more with n (acid): n (acetic anhydride) = 1:2.0, the amount of catalyst 1.0 g, reaction time was 30 min. Solid acid St/AS catalyst can repeated use 6 times, the production rate was still 71% or more. Experimental results show that the solid acid St/AS catalyst for the synthesis of acetylsalicylic acid with high catalytic activity and esterification of simple post-processing can also be reused, and do not pollute the environment, and it had a good prospect and environment-friendly green catalyst.