1 順酐的生產工藝
1 Production process of maleic anhydride
目前，工業上順酐的生產工藝路線按原料可分為苯氧化法、正丁烷法氧化法、C4烯烴法和苯酐副產法4種。其中苯氧化法應用更為廣泛，但由于苯資源有限，C4烯烴和正丁烷為原料生產順酐的技術應運而生，尤其是富產天然氣和油田伴生氣的國家，擁有大量的正丁烷資源，因此近年來正丁烷氧化法生產順酐的技術發展迅速，已經在順酐生產中占主要地位，其生產能力約占世界順酐總生產能力的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
苯蒸氣和空氣（或氧氣）在以V2O5-MnO3等為活性組分，a-Al2O3為載體的催化劑上發生氣相氧化反應生成順酐。
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年實現工業化到20世紀末，一直是順酐的主要生產方法，工藝技術成熟可靠，主要技術商有美國SD、Alusuisle/UCB (現Lonza/UCB)和日本觸媒公司。其中以SD法應用更為普及，Alusuisle／UCB法原料苯的消耗量，是較為先進的生產方法。
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烯烴法
2.1.2 C4 olefin method
C4烯烴法是以混合C4餾分中的有效成分正丁烯、丁二烯等為原料，和空氣（或氧氣），在V2O5-P2O3系催化劑作用下經氣相氧化反應生成順酐，其中正丁烯在反應過程中先脫氫生成丁二烯，再氧化生成順酐。在反應過程中，除生成主產物外，還副產生成一氧化碳、二氧化碳和水以及少量的乙醛、乙酸、丙烯醛和呋喃等。摘自六鑒投資網《順酐技術與市場調研報告》《 順酐投資分析報告》《10萬噸/年順酐項目投資建議書》
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
德國***公司和***公司開發了以混合C4餾分為原料的固定床氧化工藝。開發了以含丁二烯的C4餾分為原料的流化床氧化制順酐工藝。由于脫氫屬于吸熱反應，而且副產物較多，因此，混合C4烯烴氧化制順酐發展前途不太樂觀。
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 苯酐副產法
2.1.3 Phthalic anhydride by-product method
在由鄰二甲苯生產苯酐時，可以副產得到一定數量的順酐產品，其產量約為苯酐產量的5%。在苯酐生產中，反應尾氣經洗滌塔除去有機物后排放到大氣中，洗滌液為順酐和少量的苯甲酸、苯二甲酸等雜質，經濃縮精制和加熱脫水后得到順酐產品。
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年實現工業化。由于原料價廉、對環境污染小以及正丁烷資源豐富等原因而得到迅速的發展，代表了順酐生產工藝的發展趨勢。
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系催化劑上選擇氧化生成順酐，其氧化反應器有固定床和流化床，順酐回收工藝有水吸收法和溶劑吸收法。
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 固定床工藝
2.1.4.1 Fixed bed process
丁烷法固定床工藝主要由亨斯邁公司(1993年Monsanto將順酐業務轉讓給Huntsman公司)、BP、SD、康斯爾(Conser)公司擁有，與苯氧化法基本相似，但正丁烷氧化轉化率和選擇性均比苯低，其順酐的摩爾收率按正丁烷計僅為50～55%，而原料氣體中苯和正丁烷的摩爾濃度基本相同。因此對于同樣規模的生產裝置，正丁烷法需要較大的反應器和壓縮機反應溫度400～450℃，壓力為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 流化床工藝
2.1.4.2 Fluidized bed process
流化床工藝是Lummus公司和Lonza公司合作開發的ALMA工藝。流化床反應器中，正丁烷和空氣分別進入反應器后混合，避免了其混合時發生爆炸的可能，因此原料氣中正丁烷的摩爾分數可以提高到4％，反應所需空氣約為固定床的一半，減少了空氣壓縮機的投資和操作費用。流化床工藝的能耗低于固定床，但丁烷的單耗要比固定床高約8％，另外流化床催化劑的磨損也較大。
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
在采用丁烷法生產順酐的初期，主要是一些苯法裝置通過更換催化劑實現，就是新建的裝置工藝也與苯法基本一致，均為水吸收法回收。
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.
水吸收法是將未冷凝的含50wt%的順酐氣體在吸收塔中用水吸收成43%左右的馬來酸，然后將馬來酸溶液送至脫水精餾塔，通過二甲苯的恒沸脫水及減壓精餾生產出順酐產品。整個后處理為間歇操作。水吸收工藝國產化技術已比較成熟，操作簡便，占地較少，投資節省，對于規模2萬噸的裝置具有投資的優勢。
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 溶劑吸收法
2.1.4.4 Solvent absorption method
由于丁烷氧化反應生成少量的乙酸和丙烯酸，而苯氧化反應幾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藝遇到的腐蝕和堵塞問題要比苯法多。為了減輕腐蝕，提高順酐收率，降低能耗，各公司在改進丁烷氧化催化劑的同時，加強了對順酐回收工藝的研究。溶劑吸收工藝采用低揮發性有機溶劑，順酐收率比水吸收工藝約高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.
溶劑吸收法是以溶劑為吸收劑，經吸收、解吸、精制工序得到液體順酐，溶劑經洗滌后循環使用。整個后處理為連續操作。溶劑吸收與水吸收相比可以節約運行成本，工藝操作可實現連續化，整個裝置蒸汽平衡，避免了水吸收法中蒸汽使用不連續波峰波谷相差較大給整個裝置蒸汽平衡帶來的困難，產品質量比水吸收法更高，目前國外大部分順酐裝置采用溶劑吸收法。
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工藝采用六氫鄰苯二甲酸二異丁酯(DIBE)，Huntsman公司和Conser公司采用鄰苯二甲酸二正丁酯(DBP)。在工業生產中，這兩種溶劑的消耗接近，DIBE溶劑處理需進行水洗和堿洗兩個過程，而DBP溶劑僅需水洗。另外，DIBE的價格要高于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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