Study On Technology Of Synthetizing Sec-butyl Acetate With Butene And Acetic Acid

China is a large energy consumption country in the world and every year witnesses a large number of oil and natural gas imported into the country. However, the oil refining technology in China is far behind that in the developed countries, especially the reprocessing technology of the refined products in the downstream refining process. For the refinery C4 hydrocarbon, large amounts of C4 hydrocarbon as by-products are produced by refining enterprises in China every year. Except for those in a small amount used in the production of Methyl tertiary butyl ether(The full name in English: Methyl tert-butyl ether, as MTBE for short) and alkylation oil, most of them have been burnt as a civil fuel gas, resulting in a great energy waste, which is really a pity. In addition to conducting researches on the C4 hydrocarbon used in the production of MTBE and alkylation oil as well as those used as a motor gasoline of high octane number harmonic group points, some large refining companies around the world also study the synthesis technology of sec-butyl acetate(The full name in English: Sec-butyl acetate; English abbreviation: Sec-BA), which is used as motor gasoline of high octane number harmonic components, with C4 olefin and acetic acid. By applying refinery C4 butene as the raw material, the technology intends to combine it with the acetic acid to synthesize Sec-BA, which is characterized by high octane value, non-toxic, non-corrosive, low oxygen content and can be used as a gasoline additive so as to further improve the gasoline octane value, working as the alternative technology of MTBE.At present, the production technology of Sec-BA includes the traditional alkyd synthesis process as well as using the method of C4 botanic acid in the synthesis process all over the world. The former adopts the acetic acid and sec-butyl alcohol as raw materials to synthesize the Sec-BA by the etherification reaction with the liquid H2SO4 as the catalyst. However, H2SO4 used as the catalyst has two disadvantages: first, the sulfuric acid can cause severe corrosion to the equipment in the reaction and second, due to the poor selection effect of H2SO4 as the catalyst, more by-products would be produced in the etherification reaction, which makes the separation of products much more difficult. In view of the above disadvantages of sulfuric acid catalyst, abundant researched have been conducted by refining companies both at home and abroad and they have developed the salt solid acid catalysts such as Ti O2/SO42-, diphenylamine methane suffocate, S2O82-/Ti O2, Sn Cl4/Si O2 to replace H2SO4. The sulfonic acid resin catalyst is usually used in the esterification reaction to synthesize the Sec-BA by the C4 botanic acid method. The most obvious feature of the resin catalyst is the high conversion rate of butane and high selectivity. On the other hand, the sulfonic acid resin catalyst is very sensitive to temperature so that it is prone to fall off and make the catalyst deactivation in the high temperature condition. Some typical C4 butene acid synthesis technologies in foreign countries include: the sulfonic acid cation exchange resin catalyst technology by Germany’s Bayer Company, the KY-23 cation exchange resin catalyst technology by the former Soviet union and the Amberlyst 15 cation exchange resin catalyst technology by Japanese NIPPON PETROCHEMICALS COMPANY etc. Hunan Zhongchuang chemical co., LTD. is the first domestic company to make the synthesis technology of Sec-BA with C4 olefin acid industrialized and it built the Sec-BA industrial equipment in 2006 with the annual output of 20000t/a and in June 2009 made the expansion with the annual output of 60000 t/a.By adopting the macroporous styrene type cationic acid resin catalyst I as well as the refinery C4 as raw materials, the paper studies the synthesis of Sec-BA with C4 olefin and acetic acid as raw materials undertaking on the 200 ml fixed bed reactor. Based on the tests, it intends to examine the temperature in the esterification reaction with C4 olefin and acetic acid, the raw material feeding airspeed, the effects of olefinic acid molar ratio on the butene conversion rate and the Sec-BA selectivity. Results show that under the optimized processing condition of the reaction temperature as 60℃, feeding quality airspeed 2.5 h-1, acetic acid to butene mole ratio 2.5 and the reaction pressure of 0.8MPa, the butene conversion rate can be more than 87%, the Sec-BA selectivity is over 96.5% and the product yield is 83.9%.The paper also studies the products separation technology in the synthesis process of Sec-BA with C4 olefin and acetic acid as raw materials, mainly focusing on separating the acetic acid and by-products from the Sec-BA. In terms of the separation technology research, it is very difficult to split the Sec-BA and acetic acid by applying the simple distillation method based on the fact that the boiling points of the Sec-BA(the boiling point 112.3℃) and acetic acid(the boiling point 117.9℃) are very close to each other. Therefore, the azeotropic distillation method has been applied to separate the Sec-BA and acetic acid from the products produced in the esterification reaction. The azeotropic distillation means to add a third component to the solution system which is difficult to be separated. The added component can correspond to the original one or two components in the solution system and form the azeotrope so that components in the system can be separated. In other words, choosing the appropriate azeotropic agent(or entrainer) is the key of azeotropic distillation. The separation process selects the H2 O as the azeotropic agent to separate Sec-BA and acetic acid. H2 O and the Sec-BA can form the azeotrope which can help to separate the acetic acid and then the separation of azeotropic agent helps to get the Sec-BA products. Besides, the Aspen plus chemical calculation software has been used to carry out a simulation calculation of the Sec-BA-acetate distillation tower with the DSTWU simple separation module. The simulation result is: the reflux ratio R=0.614, plate number N=20, feeding plate is 7, D/F=0.601. Moreover, a strict calculation module Rad Frac has also been used to make a detailed calculation of the Sec-BA-acetic acid rectification tower. Under the operation condition of the tower top temperature as 84.68℃, the feeding plate temperature 102.09℃, the tower bottom temperature of 116.77℃, the products content on the top tower reaches 98.1% after a further separation and purification of the Sec-BA while the bottom acetic acid content is 98.2%, which indicates a good separation effect, realizing the separation and purification of the Sec-BA products. The purity of the Sec-BA products reaches 98% meeting the project requirements.