Method for synthesizing o-methylphenylacetic acid

Abstract

The invention provides a method for synthesizing o-methyl phenylacetic acid, which comprises the following steps: putting o-methyl benzyl chloride and a sodium cyanide aqueous solution into a reaction kettle, controlling the temperature to be 85-90 DEG C, and dropwise adding a catalyst to synthesize o-methyl phenylacetonitrile for 80-100 minutes; preparing o-methyl phenylacetic acid from o-methyl phenylacetonitrile through hydrolysis reaction; using the reaction kettle for carrying out heat exchange and temperature adjustment on the kettle body from the outer side and the inner side at the same time, wherein media flow in one direction, the first spiral pipe plays a dual role in stirring and temperature adjustment, and the stirring reaction and temperature adjustment efficiency is improved. The synthesis temperature of the o-methyl phenylacetonitrile is controlled to be 85-90 DEG C, the synthesis time is shortened, the content of impurities in the o-methyl phenylacetonitrile is 0.7% or below, and the step of rectifying the o-methyl phenylacetonitrile is omitted.

Description

technical field [0001] The invention relates to the technical field of reactors, in particular to a method for synthesizing o-methylphenylacetic acid. Background technique [0002] The synthesis of o-methylphenylacetic acid mainly includes two stages, the first stage is the synthesis of o-methylphenylacetonitrile, this stage is by the synthetic o-methylphenylacetonitrile by o-methyl benzyl chloride and sodium cyanide aqueous solution, and this reaction is High-temperature exothermic reaction requires particularly high cooling performance of the reactor, and because o-methylbenzyl chloride is a highly corrosive material, stainless steel kettles cannot be used; the second stage is to prepare o-methylphenylacetic acid by hydrolyzing o-methylphenylacetonitrile , as disclosed in CN200610124563.7 and CN102476991B, a preparation method of o-methylphenylacetic acid. [0003] In the first stage, because the reaction is a high-temperature exothermic reaction, if the temperature canno...

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Problems solved by technology

[0003] In the first stage, because the reaction is a high-temperature exothermic reaction, if the temperature cannot be adjusted in time, the temperature in the reactor will be too high, and safety accidents such as explosions will easily occur; but the temperature control is too low, which will reduce the reaction rate and prolong the synthesis time. The impurity content in the o-toluene acetonitrile is relatively high. In the existing actual production, the temperature is usually controlled below 85°C to avoid excessive reaction speed and high temperature, and the temperature cannot be adjusted in time, but the synthesis time takes 5-6 hours. The impurity content in o-toluene acetonitrile is about 4%, which has the problem of long synthesis time and high impurity content, and subsequent rectification treatment is required for o-toluene acetonitrile

[0004] The existing reactor methods are mainly divided into three types: the first one is to install a temperature-adjusting shell on the outer wall of the reactor, but the temperature adjustment speed is slow, and the temperature adjustment in the middle of the reactor is limited, so it cannot be realized quickly; The second is to install a thermostat coil in the reactor. The thermostat coil will occupy the inner space of the reactor, and it will also easily affect the stirring range of the stirring shaft, which is not conducive to the full reaction of the material and rapid heat exchange; the third is A double-layer circulation cavity is set in the stirring shaft, and the cold source is exchanged through the double-layer circulation cavity. For example, CN209049386U discloses a kind of enamel reaction kettle. With this structure, the stirring area and the temperature adjustment area overlap, but the refrigerant flows in and out The channel is arranged side by side with the route, and the heat exchange between the two channels is easy, which reduces the efficiency of temperature adjustment, which is not conducive to the rapid removal of heat, and the stirring shaft is not easy to process

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