2-Methylpyrazine CAS 109-08-0

1. Reaction: Put catalyst 1 in reactor 1, pass in nitrogen gas, check the airtightness of the reaction pipeline, and discharge the air in reactor 1 at the same time, the flow rate of nitrogen gas is 0.2L/min, heat the reactor 1. Control the temperature rise rate, and finally rise to 360°C; during the temperature rise period, while maintaining the total gas flow at 0.2L/min, slowly increase the ratio of hydrogen and nitrogen until they are finally equal, and the catalyst 1 is reduced for 4 hours; the B2 Amine and 1,2-propanediol are mixed in an equimolar ratio and enter a preheater at 300°C through a metering pump. After reactor one is heated to a predetermined temperature, it enters reactor one for a gas-solid phase contact catalytic reaction. The mixture enters the receiver after being cooled by the condenser, and the exhaust gas is taken after being absorbed and then emptied and separated to obtain the 2-methylpyrazine.
2. Separation: collect the crude product obtained from the above reaction, separate it through a rectification tower, control the reflux ratio, obtain 4 fractions after 65-85°C, 85-95°C, 95-100°C, and 100°C, and carry out azeotropic For the separation of fractions, add a dehydrating agent to the azeotropic distillation at 95-100°C for dehydration, then raise the temperature and distill out, collect the fractions after 135°C to obtain the 2-methylpyrazine.

Among them, the catalyst is a copper-containing composite catalyst prepared by an impregnation method with Al2O3 as a carrier; the copper-containing composite catalyst is prepared from copper, cadmium, and chromium catalysts with an oxide content of 2:2:1 by weight.

The method for co-preparing 2-methylpyrazine by propylene glycol and ethylenediamine is as follows:

(1) Propylene glycol and ethylenediamine are mixed;

(2) Adding water to the mixed mixture to dilute;

(3) Vaporize the diluted mixture;

(4) Adding the vaporized mixed gas to the catalyst for reaction;

(5) The product after reaction is cooled and filtered, and the ethylenediamine obtained by filtration is reclaimed;

(6) The cooled product is dehydrated, and the waste water obtained by dehydration is removed;

(7) Carry out rectification to the product after dehydration, and the rectification residue that rectification obtains is got rid of;