Maleic anhydride manufacturers tell you the production process and use of maleic anhydride. What is maleic anhydride? Maleic anhydride is also known as maleic anhydride, maleic anhydride, 2,5-furanedione, etc. The orthorhombic system is a colorless needle or sheet crystal. It has strong pungent smell, soluble in ethanol, ether and acetone, but difficult to dissolve in petroleum ether and carbon tetrachloride. Maleic acid is formed by reaction with hot water. It is mainly used to produce unsaturated polyester resin, alkyd resin, malathion, 4049, iodoamine.

顺酐的工艺

Production process of maleic anhydride

1、苯氧化法

1. Oxidation of benzene

苯氧化为顺酐是在催化剂存在下进行的。常用催化剂的活性组分均为钒的氧化物（见金属氧化物催化剂），为抑制苯被完全氧化，常加入钼、磷、钛、钨、银及碱金属等元素的氧化物为添加剂，并采用低比表面的惰性物质为催化剂载体，如α－氧化铝、刚玉等。反应在常压下进行，温度350～400℃。工艺过程由苯的氧化，顺酐的分离和提纯两大部分组成（见图）。苯蒸气和空气能形成爆炸混合物，所以进入反应器的混合气中，苯的浓度应在爆炸极限之外，一般为1%～1.4%(摩尔)。苯氧化为强放热反应，工业上常采用列管式固定床反应器，有很大的传热面，管外为冷却系统，反应热可用于产生高压蒸汽。离开反应器的气体中含顺酐约1%（摩尔）,用冷却的办法可将其中所含一半左右的顺酐冷凝为液体，其余部分则用吸收法回收。吸收剂用水或惰性有机溶剂，大多数工厂采用的是水。所得到的吸收液是顺丁烯二酸的水溶液，浓度35%～40%(质量)，需用共沸溶剂（例如二甲苯、苯甲醚）进行脱水，把酸重新转化成酸酐。脱水也可在膜式蒸发器中进行。粗酐经减压精馏可得成品。以苯计算，整个过程的顺酐收率为92%～96%（质量）。

The oxidation of benzene to maleic anhydride is carried out in the presence of catalyst. The active components of the 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 substances with low specific surface area are used as catalyst carriers, such as α - alumina and corundum. The reaction was carried out under normal pressure at 350-400 ℃. The process consists of oxidation of benzene, separation and purification of maleic anhydride (see Figure). Benzene vapor and air can form explosive mixture, so the concentration of benzene in the mixture gas entering the reactor should be outside the explosion limit, generally 1% - 1.4% (mole). Benzene oxidation is a strong exothermic reaction. The 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 generate high pressure steam. About 1% (mole) of maleic anhydride is contained in the gas leaving the reactor. About half of the maleic anhydride in the gas can be condensed into liquid by cooling, and the rest can be recovered by absorption method. 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). The azeotropic solvent (such as xylene and anisole) is used for dehydration to convert the acid into anhydride again. Dehydration can also be carried out in membrane evaporator. The crude anhydride can be obtained by vacuum distillation. The yield of maleic anhydride in the whole process is 92% - 96% (mass).

2、C4烃氧化法

2. C4 hydrocarbon oxidation

正丁烷与丁烯均含有与顺酐相同的碳原子数，是顺酐的理想原料。由于正丁烷较其他原料低廉，用正丁烷更为有利。其流程与苯氧化法基本相同，催化剂为钒-磷-氧体系，添加剂有铁、铅、锌、铜、锑等元素的氧化物。可用固定床反应器或用流化床反应器，反应温度约400℃。正丁烷-空气混合物中正丁烷浓度为1.0%～1.6%(摩尔)。整个过程的顺酐收率按正丁烷计约为50%。由于C4烃氧化的选择性较低,因此设备投资较以苯为原料时为高，且后加工不能采用部分冷凝，而必须将反应气体中的顺酐全部用吸收法回收，从而使能耗加大。但由于正丁烷比苯便宜，而且苯毒性大。因此，以正丁烷为原料是有吸引力的，对本法所用催化剂的改进工作，各国都在大力进行中。

Both n-butane and butene have the same carbon atom number as maleic anhydride, so they are ideal raw materials for maleic anhydride production. Because the price of n-butane is lower than other raw materials, it is more advantageous to use n-butane. The process is basically the same as that of benzene oxidation, the catalyst is vanadium phosphorus oxygen system, and the additives are iron, lead, zinc, copper, antimony and other elements. Fixed bed reactor or fluidized bed reactor can be used, and the reaction temperature is about 400 ℃. The concentration of n-butane in n-butane air mixture was 1.0% - 1.6% (mol). The yield of maleic anhydride is about 50% in n-butane. Due to the low selectivity of C4 hydrocarbon oxidation, the equipment investment is higher than that with benzene as raw material, and partial condensation can not be used in the post-processing, but all maleic anhydride in the reaction gas must be recovered by absorption method, so as to increase energy consumption. However, n-butane is cheaper than benzene, and benzene is more toxic. Therefore, it is attractive to use n-butane as raw material. The improvement of catalyst used in this method is being vigorously carried out in various countries.

顺酐的用途

Application of maleic anhydride

顺酐主要用于不饱和聚酯树脂、醇酸树脂、农药马拉硫磷、低毒农药4049、长效碘胺的原料。也是涂料、马来松香、聚马来酐、顺酐-苯乙烯共聚物的共聚单体，也是油墨助剂、造纸助剂、增塑剂、酒石酸、富马酸、四氢呋喃等的有机化工原料。

Maleic anhydride is mainly used to produce unsaturated polyester resin, alkyd resin, malathion, high efficiency and low toxicity pesticide 4049, and long-acting iodoamine. It is also the comonomer of coating, maleic rosin, polymaleic anhydride and maleic anhydride styrene copolymer. It is also an organic chemical raw material for the production of ink auxiliaries, papermaking auxiliaries, plasticizers, tartaric acid, fumaric acid, tetrahydrofuran, etc.