1 顺酐的生产工艺
1 Production process of maleic anhydride
目前，工业上顺酐的生产工艺路线按原料可分为苯氧化法、正丁烷法氧化法、C4烯烃法和苯酐副产法4种。其中苯氧化法应用更为广泛，但由于苯资源有限，C4烯烃和正丁烷为原料生产顺酐的技术应运而生，尤其是富产天然气和油田伴生气的，拥有大量的正丁烷资源，因此近年来正丁烷氧化法生产顺酐的技术发展迅速，已经在顺酐生产中占主导地位，其生产能力约占世界顺酐总生产能力的80%。
At present, the industrial production process routes of maleic anhydride can be divided into four kinds according to raw materials: benzene oxidation, n-butane oxidation, C4 olefin process and phthalic anhydride by-product process. Among them, the benzene oxidation method is the most widely used, but due to the limited benzene resources, the technology of producing maleic anhydride with C4 olefin and n-butane as raw materials has emerged at the historic moment, especially in countries rich in natural gas and oil field associated gas, which have a large number of n-butane resources. Therefore, in recent years, the technology of producing maleic anhydride by n-butane oxidation method has developed rapidly and has occupied a leading position in the production of maleic anhydride, and its production capacity accounts for about 80% of the total production capacity of maleic anhydride in the world.
2.1.1 苯氧化法
2.1.1 Benzene oxidation method
苯蒸气和空气（或氧气）在以V2O5-MnO3等为活性组分，a-Al2O3为载体的催化剂上发生气相氧化反应生成顺酐。
Benzene vapor and air (or oxygen) undergo gas-phase oxidation reaction to produce maleic anhydride on the catalyst with V2O5-MnO3 as the active component and a-Al2O3 as the carrier.
苯氧化法自1933年实现工业化到20世纪末，一直是顺酐的主要生产方法，工艺技术成熟可靠，主要技术商有美国SD、Alusuisle/UCB (现Lonza/UCB)和日本触媒公司。其中以SD法应用更为普及，Alusuisle／UCB法原料苯的消耗量，是较为的生产方法。
Since the industrialization of benzene oxidation in 1933 to the end of the 20th century, it has been the main production method of maleic anhydride. The process technology is mature and reliable. The main technology patentees include SD, Alusuisle/UCB (now Lonza/UCB) and Japanese catalyst companies. Among them, SD method is the most widely used, and Alusuisle/UCB method has the lowest consumption of raw material benzene, which is a relatively advanced production method.
2.1.2 C4烯烃法
2.1.2 C4 olefin method
C4烯烃法是以混合C4馏分中的有效成分正丁烯、丁二烯等为原料，和空气（或氧气），在V2O5-P2O3系催化剂作用下经气相氧化反应生成顺酐，其中正丁烯在反应过程中先脱氢生成丁二烯，再氧化生成顺酐。在反应过程中，除生成主产物外，还副产生成一氧化碳、二氧化碳和水以及少量的乙醛、乙酸、丙烯醛和呋喃等。摘自六鉴投资网《顺酐技术与市场调研报告》《 顺酐投资分析报告》《10万吨/年顺酐项目投资建议书》
The C4 olefin method uses the effective components such as n-butene and butadiene in the mixed C4 fraction as raw materials, and air (or oxygen) to produce maleic anhydride through the gas-phase oxidation reaction under the action of V2O5-P2O3 system catalyst. In the reaction process, n-butene is dehydrogenated to produce butadiene, and then oxidized to produce maleic anhydride. In the reaction process, in addition to the main products, carbon monoxide, carbon dioxide and water as well as a small amount of acetaldehyde, acetic acid, acrolein and furan are also generated as by-products. Extracted from Liujian Investment Network, Maleic Anhydride Technology and Market Research Report, Maleic Anhydride Investment Analysis Report, and Investment Proposal for 100000 t/a Maleic Anhydride Project
德国***公司和***公司开发了以混合C4馏分为原料的固定床氧化工艺。开发了以含丁二烯的C4馏分为原料的流化床氧化制顺酐工艺。由于脱氢属于吸热反应，而且副产物较多，因此，混合C4烯烃氧化制顺酐发展前途不太乐观。
Germany * * * Company and * * * Company developed fixed bed oxidation process with mixed C4 fraction as raw material. * * * Company of Japan has developed a fluidized bed oxidation process to produce maleic anhydride using C4 fraction containing butadiene as raw material. Because dehydrogenation belongs to endothermic reaction and there are many by-products, the future of oxidation of mixed C4 olefins to maleic anhydride is not optimistic.
2.1.3 苯酐副产法
2.1.3 Phthalic anhydride by-product method
在由邻二甲苯生产苯酐时，可以副产得到一定数量的顺酐产品，其产量约为苯酐产量的5%。在苯酐生产中，反应尾气经洗涤塔除去有机物后排放到大气中，洗涤液为顺酐和少量的苯甲酸、苯二甲酸等杂质，经浓缩精制和加热脱水后得到顺酐产品。
When phthalic anhydride is produced from o-xylene, a certain amount of maleic anhydride products can be obtained as a by-product, and its output is about 5% of the output of phthalic anhydride. In the production of phthalic anhydride, the reaction tail gas is discharged into the atmosphere after the organic matter is removed by the washing tower. The washing liquid is maleic anhydride and a small amount of benzoic acid, phthalic acid and other impurities. The product of maleic anhydride is obtained after concentration, refining and heating dehydration.
2.1.4 正丁烷氧化法
2.1.4 n-butane oxidation method
正丁烷氧化法于1974年实现工业化。由于原料价廉、对环境污染小以及正丁烷资源丰富等原因而得到迅速的发展，代表了顺酐生产工艺的发展趋势。
The n-butane oxidation process was industrialized by Company of the United States in 1974. Due to the low cost of raw materials, low environmental pollution and abundant n-butane resources in Europe and the United States, the rapid development represents the development trend of maleic anhydride production process.
正丁烷在V2O5-P2O3系催化剂上选择氧化生成顺酐，其氧化反应器有固定床和流化床，顺酐回收工艺有水吸收法和溶剂吸收法。
N-butane is selectively oxidized on V2O5-P2O3 catalyst to produce maleic anhydride. The oxidation reactor has fixed bed and fluidized bed, and the recovery process of maleic anhydride has water absorption method and solvent absorption method.
2.1.4.1 固定床工艺
2.1.4.1 Fixed bed process
丁烷法固定床工艺主要由亨斯迈公司(1993年Monsanto将顺酐业务转让给Huntsman公司)、BP、SD、康斯尔(Conser)公司拥有，与苯氧化法基本相似，但正丁烷氧化转化率和选择性均比苯低，其顺酐的摩尔收率按正丁烷计仅为50～55%，而原料气体中苯和正丁烷的摩尔浓度基本相同。因此对于同样规模的生产装置，正丁烷法需要较大的反应器和压缩机反应温度400～450℃，压力为125～130MPa。
Butane fixed-bed process is mainly owned by Huntsman Company (Monsanto transferred the maleic anhydride business to Huntsman Company in 1993), BP, SD, and CONSER. It is basically similar to the benzene oxidation process, but the conversion and selectivity of n-butane oxidation are lower than that of benzene. The molar yield of maleic anhydride is only 50-55% based on n-butane, while the molar concentration of benzene and n-butane in the feed gas is basically the same. Therefore, for production units of the same scale, the n-butane process requires larger reactor and compressor reaction temperature of 400~450 ℃ and pressure of 125~130MPa.
2.1.4.2 流化床工艺
2.1.4.2 Fluidized bed process
流化床工艺是Lummus公司和Lonza公司合作开发的ALMA工艺。流化床反应器中，正丁烷和空气分别进入反应器后混合，避免了其混合时发生爆炸的可能，因此原料气中正丁烷的摩尔分数可以提高到4％，反应所需空气约为固定床的一半，减少了空气压缩机的投资和操作费用。流化床工艺的能耗低于固定床，但丁烷的单耗要比固定床高约8％，另外流化床催化剂的磨损也较大。
Fluidized bed process is an ALMA process developed jointly by Lummus and Lonza. In the fluidized bed reactor, n-butane and air are mixed after entering the reactor respectively, avoiding the possibility of explosion when they are mixed, so the mole fraction of n-butane in the feed gas can be increased to 4%, and the air required for the reaction is about half of that of the fixed bed, reducing the investment and operating costs of the air compressor. The energy consumption of the fluidized bed process is lower than that of the fixed bed, but the unit consumption of butane is about 8% higher than that of the fixed bed, and the wear of the fluidized bed catalyst is also large.
2.1.4.3 水吸收法
2.1.4.3 Water absorption method
在采用丁烷法生产顺酐的初期，主要是一些苯法装置通过更换催化剂实现，就是新建的装置工艺也与苯法基本一致，均为水吸收法回收。
At the initial stage of the production of maleic anhydride by butane process, it was mainly achieved by replacing catalysts in some benzene process units. Even the newly built unit process was basically the same as that of benzene process, which were recovered by water absorption method.
水吸收法是将未冷凝的含50wt%的顺酐气体在吸收塔中用水吸收成43%左右的马来酸，然后将马来酸溶液送脱水精馏塔，通过二甲苯的恒沸脱水及减压精馏生产出顺酐产品。整个后处理为间歇操作。水吸收工艺国产化技术已比较成熟，操作简便，占地较少，投资节省，对于规模2万吨的装置具有投资的优势。
The water absorption method is to absorb the uncondensed maleic anhydride gas containing 50wt% into about 43% maleic acid in the absorption tower with water, and then send the maleic acid solution to the dehydration and distillation tower to produce maleic anhydride products through azeotropic dehydration of xylene and vacuum distillation. The whole post-treatment is intermittent operation. The localization technology of water absorption process has been relatively mature, easy to operate, less land occupation, and investment saving. It has the advantage of investment for the 20000 ton unit.
2.1.4.4 溶剂吸收法
2.1.4.4 Solvent absorption method
由于丁烷氧化反应生成少量的乙酸和丙烯酸，而苯氧化反应几乎不生成乙酸和丙烯酸，另外丁烷氧化生成的水也比苯氧化多1倍，所以丁烷法水吸收工艺遇到的腐蚀和堵塞问题要比苯法多。为了减轻腐蚀，提高顺酐收率，降低能耗，各公司在改进丁烷氧化催化剂的同时，加强了对顺酐回收工艺的研究。溶剂吸收工艺采用低挥发性有机溶剂，顺酐收率比水吸收工艺约高5%。
Since butane oxidation reaction generates a small amount of acetic acid and acrylic acid, while benzene oxidation reaction hardly generates acetic acid and acrylic acid, and the water generated by butane oxidation is also twice as much as that of benzene oxidation, so the butane water absorption process encounters more corrosion and blockage problems than benzene method. In order to reduce corrosion, improve the yield of maleic anhydride and reduce energy consumption, companies have strengthened the research of maleic anhydride recovery process while improving the butane oxidation catalyst. The solvent absorption process uses low volatile organic solvent, and the yield of maleic anhydride is about 5% higher than that of water absorption process.
溶剂吸收法是以溶剂为吸收剂，经吸收、解吸、精制工序得到液体顺酐，溶剂经洗涤后循环使用。整个后处理为连续操作。溶剂吸收与水吸收相比可以节约运行成本，工艺操作可实现连续化，整个装置蒸汽平衡，避免了水吸收法中蒸汽使用不连续波峰波谷相差较大给整个装置蒸汽平衡带来的困难，产品质量比水吸收法更高，目前国外大部分顺酐装置采用溶剂吸收法。
Solvent absorption method uses solvent as absorbent to obtain liquid maleic anhydride through absorption, desorption and refining processes. The solvent is recycled after washing. The whole post-processing is continuous operation. Compared with water absorption, solvent absorption can save operation costs, realize continuous process operation, and achieve steam balance of the whole plant, which avoids the difficulty of steam balance of the whole plant caused by the large difference between the discontinuous peak and trough of steam in water absorption method. The product quality is higher than that of water absorption method. At present, most maleic anhydride plants abroad use solvent absorption method.
ALMA工艺采用六氢邻苯二甲酸二异丁酯(DIBE)，Huntsman公司和Conser公司采用邻苯二甲酸二正丁酯(DBP)。在工业生产中，这两种溶剂的消耗接近，DIBE溶剂处理需进行水洗和碱洗两个过程，而DBP溶剂仅需水洗。另外，DIBE的要高于DBP。
Diisobutyl hexahydrophthalate (DIBE) is used in ALMA process, and Di-n-butyl phthalate (DBP) is used by Huntsman and CONSER. In industrial production, the consumption of these two solvents is close. DIBE solvent treatment requires two processes: water washing and alkali washing, while DBP solvent only needs water washing. In addition, the price of DIBE is higher than that of DBP.
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