Depending on the different raw materials used, the currently industrialized synthesis methods of resorcinol are mainly: benzene sulfonation alkali fusion method, m-dicumyl oxidation method and m-phenylenediamine method. The synthesis method of m-phenylenediamine is shown in the table below. Benzene sulfonation alkali fusion method m-dicumyl oxidation method m-phenylenediamine method Principle benzene and 25 fuming sulfuric acid are first sulfonated at 70-80°C, and then mixed with 65 fuming sulfuric acid Nicotinic sulfuric acid undergoes secondary sulfonation at 130-160°C to generate isophenylenediiodic acid, which is then neutralized with an alkali to prepare isophenylenedisulfonic acid sodium salt; the above product is added to molten anhydrous sodium hydroxide. Alkali fusion, heat preservation reaction at 320-360t. The reaction product is diluted with water, filtered, acidified to pH=4-5, and finally extracted with diethyl ether, isopropyl ether or n-butanol, and distilled to obtain resorcinol. Meta-dicumylbenzene is oxidized at 80-90°C, with a pH of 8-10, and a pressure of 0.54 and Pa in the air for 36 hours. The oxidation solution is then placed in a mixture of H2O2 and H2SO4, and pretreated at 80°C for about 20 minutes. . After layering, the organic phase is washed with water, diluted with acetone, catalytically hydrolyzed for 35 minutes, and purified to obtain resorcinol. Meta-dicumene is obtained industrially as a by-product of the production of cumene. Meta-phenylenediamine is produced by hydrogenation of m-dinitrobenzene, and then resorcinol is obtained by hydrolysis of m-phenylenediamine. Advantages: The process conditions are simple and the technology is mature. This process has low pollution, low cost, short process, and the total industrial production yield can reach 70%. Above (based on benzene), acetone is also produced as a by-product; it is reported that the highest yield can reach about 90%. Disadvantages: Secondary sulfonation requires the use of a large amount of oleum, which seriously corrodes equipment; and the reaction by-product Na2SO4 is difficult to handle; the intermediate product benzene disulfonic acid sodium salt is solid particles, and resorcinol sodium salt is a high-viscosity solid. To increase fluidity, add excess caustic soda. This process produces a large amount of three wastes and causes serious environmental pollution. The technical content is high and it is not as simple and easy as the patents and some data suggest. Data from many domestic scientific research institutions show that the production of resorcinol by oxidation is quite difficult in terms of oxidation, extraction, separation and engineering amplification. It is very difficult in China. It is difficult to achieve a breakthrough. The raw material of this method, m-dinitrobenzene, is produced by the nitration of benzene in mixed acid. The environmental pollution is greater, even more serious than that of the sulfonation method. The reaction process is long, so it is difficult to produce industrially. Current situation This method is a traditional method for producing resorcinol. This process is the main method for producing resorcinol abroad (mainly Japan), and it is also the main direction for the development of resorcinol production in the future. However, there is currently no industrialized device in our country. Foreign literature also reports a variety of other resorcinol synthesis process routes, the main ones are: (1) using benzene as raw material, m-dinitrobenzene is obtained through nitration, then reduced to m-phenylenediamine, and then m-phenylenediamine is obtained through oxidation Phenol; (2) Condensation of acetone and acrylic acid to generate δ-keto acid, which is then reacted with alcohol to obtain ketone ester, which is then ring-formed in the presence of a palladium/thorium catalyst and dehydrogenated to obtain resorcinol; (3) Phenol selection Sexual hydrogenation generates cyclohexanone, selective oxidative dehydrogenation generates α, β-unsaturated ketones, and after hydration, 3-hydroxycyclohexanone is obtained. With carbon as the carrier and iodine and palladium as the catalyst, resorcinol is obtained after dehydrogenation. Phenol; (4) Some domestic companies use m-aminophenol oxidation to prepare resorcinol. Although there are many reports in the literature, industrialization has not been achieved due to various factors. 1.2 Improvement of the benzene sulfonation alkali fusion method In view of the problems of the benzene sulfonation alkali fusion method, various companies and research units have put forward some improvement suggestions, and have made some achievements in reducing alkali consumption, acid consumption, reducing the production of three wastes, and increasing the yield. progress. (1) SO3 sulfonation technology. Overseas, SO3 has been developed as a sulfonation agent instead of fuming sulfuric acid. In recent years, it has also been successfully developed in China and has been industrialized. Using SO3 as a sulfonating agent not only reduces costs, but also reduces environmental pollution. (2) After the secondary sulfonation of resorcin and p-cresol to produce benzene disulfonic acid, vaporized toluene is added for tertiary sulfonation, which can remove the sulfuric acid generated during sulfonation. This not only reduces The consumption of alkali during neutralization and alkali melting also greatly reduces the generation of by-product Na2SO4 and reduces pollution. During alkali fusion, the presence of sodium toluenesulfonate reduces the viscosity of the reaction solution, making the operation easier. Such a set of equipment can produce resorcinol and p-cresol at the same time.
(3) Co-production process of resorcinol and phenol. This process was first proposed by Japan's Ube Kosan Co., Ltd. and Mitsui Toka Co., Ltd., and adopts the method of first liquid phase sulfonation and then gas phase sulfonation. The sulfonation liquid is recycled without neutralization, which not only reduces the usage of NaOH, but also simplifies the operation. At the same time, the sulfonated by-products can generate phenol sodium salt, m-carboxybenzenesulfonic acid sodium salt and resorcinol disodium salt during alkali fusion, which allows the by-products to be more recovered. The resorcinol generated by the acidification of the alkali melt is extracted by the phenol generated at the same time. After being separated from the water, it is directly distilled, which simplifies the original multiple extraction operations. (4) Improvement of alkali melting kettle: Indspek Chemical Company adopts a kneading alkali melting kettle with a powerful stirrer, which can greatly reduce the consumption of alkali, thereby also reducing the consumption of acid and reducing by-products.