1、苯氧化法
1. Benzene oxidation process
苯氧化為順酐是在催化劑存在下進行的。常用催化劑的活性組分均為釩的氧化物（見金屬氧化物催化劑），為抑制苯被完全氧化，常加入鉬、磷、鈦、鎢、銀及堿金屬等元素的氧化物為添加劑，并采用低比表面的惰性物質(zhì)為催化劑載體，如α－氧化鋁、剛玉等。反應(yīng)在常壓下進行，溫度350～400℃。工藝過程由苯的氧化，順酐的分離和提純兩大部分組成（見圖）。苯蒸氣和空氣能形成爆炸混合物，所以進入反應(yīng)器的混合氣中，苯的濃度應(yīng)在爆炸極限之外，一般為1%～1.4%(摩爾)。
The oxidation of benzene to maleic anhydride is carried out in the presence of catalyst. The active component of commonly used catalysts are vanadium oxides (see metal oxide catalysts). In order to inhibit the complete oxidation of benzene, oxides of molybdenum, phosphorus, titanium, tungsten, silver and alkali metals are often added as additives, and inert materials with low specific surface area are used as catalyst carriers, such as α－ Alumina, corundum, etc. The reaction was carried out at 350 ~ 400 ℃ under normal pressure. The process consists of benzene oxidation, maleic anhydride separation and purification (see Figure). Benzene vapor and air can form explosive mixture, so the concentration of benzene in the mixture entering the reactor should be beyond the explosion limit, generally 1% - 1.4% (mole).
苯氧化為強放熱反應(yīng)，工業(yè)上常采用列管式固定床反應(yīng)器，有很大的傳熱面，管外為冷卻系統(tǒng)，反應(yīng)熱可用于產(chǎn)生高壓蒸汽。離開反應(yīng)器的氣體中含順酐約1%（摩爾）,用冷卻的辦法可將其中所含一半左右的順酐冷凝為液體，其余部分則用吸收法回收。
Benzene oxidation is a strong exothermic reaction. Tubular fixed bed reactor is often used in industry. It has a large heat transfer surface and a cooling system outside the tube. The reaction heat can be used to produce high-pressure steam. The gas leaving the reactor contains about 1% (mole) maleic anhydride, about half of which can be condensed into liquid by cooling, and the rest can be recovered by absorption.
吸收劑用水或惰性有機溶劑，大多數(shù)工廠采用的是水。所得到的吸收液是順丁烯二酸的水溶液，濃度35%～40%(質(zhì)量)，需用共沸溶劑（例如二甲苯、苯甲醚）進行脫水，把酸重新轉(zhuǎn)化成酸酐。脫水也可在膜式蒸發(fā)器中進行。粗酐經(jīng)減壓精餾可得成品。以苯計算，整個過程的順酐收率為92%～96%（質(zhì)量）。
Absorbent water or inert organic solvents, most plants use water. The absorption solution obtained is an aqueous solution of maleic acid with a concentration of 35% - 40% (mass). Azeotropic solvents (such as xylene and anisole) are used for dehydration to convert the acid into anhydride again. Dehydration can also be carried out in a membrane evaporator. The crude anhydride can be obtained by vacuum distillation. Calculated by benzene, the yield of maleic anhydride in the whole process is 92% ～ 96% (mass).
2、C4烴氧化法
2. C4 hydrocarbon oxidation process
正丁烷與丁烯均含有與順酐相同的碳原子數(shù)，是順酐的理想原料。由于正丁烷較其他原料低廉，用正丁烷更為有利。其流程與苯氧化法基本相同，催化劑為釩-磷-氧體系，添加劑有鐵、鉛、鋅、銅、銻等元素的氧化物。可用固定床反應(yīng)器或用流化床反應(yīng)器，反應(yīng)溫度約400℃。正丁烷-空氣混合物中正丁烷濃度為1.0%～1.6%(摩爾)。
Both n-butane and butene contain the same number of carbon atoms as maleic anhydride, so they are ideal raw materials for maleic anhydride production. Because n-butane is cheaper than other raw materials, it is more advantageous to use n-butane. The catalyst is V-P-O system and the additives are oxides of iron, lead, zinc, copper and antimony. The reaction temperature is about 400 ℃. The concentration of n-butane in the mixture of n-butane and air is 1.0% ~ 1.6% (mole).
整個過程的順酐收率按正丁烷計約為50%。由于C4烴氧化的選擇性較低,因此設(shè)備投資較以苯為原料時為高，且后加工不能采用部分冷凝，而必須將反應(yīng)氣體中的順酐全部用吸收法回收，從而使能耗加大。但由于正丁烷比苯便宜，而且苯毒性大。因此，以正丁烷為原料是有吸引力的，對本法所用催化劑的改進工作，各國都在大力進行中。
The yield of maleic anhydride is about 50% based on n-butane. Due to the low selectivity of C4 hydrocarbon oxidation, the equipment investment is higher than that of benzene, and partial condensation can not be used in the post-processing, but the maleic anhydride in the reaction gas must be recovered by absorption method, thus increasing the energy consumption. But because n-butane is cheaper than benzene, and benzene is toxic. Therefore, it is attractive to use n-butane as raw material, and the improvement of catalyst used in this method is being vigorously carried out in various countries.
順酐的用途
Application of maleic anhydride
順酐主要用于不飽和聚酯樹脂、醇酸樹脂、農(nóng)藥馬拉硫磷、低毒農(nóng)藥4049、長效碘胺的原料。也是涂料、馬來松香、聚馬來酐、順酐-苯乙烯共聚物的共聚單體，也是油墨助劑、造紙助劑、增塑劑、酒石酸、富馬酸、四氫呋喃等的有機化工原料
Maleic anhydride is mainly used in the production of unsaturated polyester resin, alkyd resin, pesticide malathion, high efficiency and low toxicity pesticide 4049 and long-term iodamine. It is also a comonomer of coatings, maleic rosin, polymaleic anhydride and maleic anhydride styrene copolymer, and an organic chemical raw material for the production of ink additives, papermaking additives, plasticizers, tartaric acid, fumaric acid, tetrahydrofuran, etc
