Nitration method for synthesizing dinitrotoluene in one step

Abstract

The invention relates to one-step dinitrotoluene synthesis in a microchannel reactor. The method comprises the steps of taking toluene and mixed acid of nitric acid / sulfuric acid (n / s) as initial reaction materials, inputting material flow synchronously into a microreactor through a metering pump and finishing mixed mass transfer and reaction in a reaction channel. The substance ratio of n to s in the reactive mixed acid is 0.1 to 1.0, and the mass ratio of water is less than 15 percent. The liquid hourly space velocity in the reactor is 500 to 50,000 h<-1>. The microchannel reactor adopts a stainless steel flat-plate structure which comprises fixed pressing-sealing plates, a microchannel plate, a raw-material inlet, a product outlet, as well as a temperature-control pore channel and a thermal-couple measurement-control jack which are positioned on two sealing plates. The method is continuously operated under a technological condition with medium / strong nitrating acid, and is safe in process. The conversion rate of the toluene in the reactor at an operation temperature between normal temperature and 80 DEG C is higher than 98 percent, and the yield of dinitrotoluene is higher than95 percent, wherein the ratio of two main isomer components, namely 2,4-dinitrotoluene and 2,6-dinitrotoluene, is more than 4 and can be nearly 5 under optimum conditions.

Description

technical field [0001] The present invention relates to the nitration of aromatic hydrocarbons, specifically a nitration method and a microchannel reactor for synthesizing dinitrotoluene in one step, wherein dinitrotoluene is synthesized in one step from toluene in the microchannel reactor; The safe and continuous synthesis of dinitrotoluene in a microchannel reactor under the reactor condition of up to 80°C, wherein the design and application of the microchannel reactor belongs to the field of new chemical reactors. Background technique [0002] Toluene nitration is an important reaction in the chemical industry, and its nitrated product dinitrotoluene (DNT) is mainly used in the preparation of dyes, paints, and coatings, and is also a precursor for the production of explosives and toluene diisocyanate (TDI). Conventional industrial production DNT method is to use many ring-type or multi-pot-type stirring reaction systems connected in series or in parallel to make toluene a...

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Problems solved by technology

[0005] CN1793106A (2006) adopts a two-step constant temperature reaction process with 8 kettles connected in series to obtain a concentration of dinitrotoluene greater than 95.3%, and without MNT and TNT, but there are many reactor stages, and a reactor with a paddle agitator is used , the safety of the reaction process is difficult to guarantee

[0011] From the point of view of the single-pass conversion rate and product selectivity of the reactor, its production cost of the method for the synthesis of dinitrotoluene described in the above disclosed patents is all expensive, because there are many reactor stages (called cascade reaction) device), the ratio of raw materials is strictly controlled, the stirring device and cooling system are required to be in step with the shutdown and start-up of the reaction system, the local temperature rise is serious, the reaction time is long, and the medium containing DNT or most of the DNT is subjected to high temperature stress. , the device is unsafe to operate with the

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