Apparatus and method for preparing aminobenzene by nitrobenzene gas-phase hydrogenation

[0050] The process method for preparing aniline according to the present invention is specifically as follows:

[0051] A metal-supported catalyst with an average particle diameter of 45-300 microns is introduced into the reactor from the catalyst inlet 4. In order to allow all the catalyst to enter the reactor, nitrogen or air is introduced through the gas distributor 12 at the gas feed inlet 1 at the bottom of the reactor when the catalyst is added. Under the loosening of nitrogen or air with a small gas flow, the catalyst particles enter the reactor from the catalyst inlet 4 and mainly stay in the dense phase zone 14 of the first catalyst. After the catalyst is loaded into the reactor, the gas in the reactor is replaced by an inert gas to an oxygen-free state. During this period, the temperature was gradually increased to 200-300°C, and then hydrogen was cut in to perform catalyst reduction. During the reduction, the gas velocity in the reactor is controlled between 0.05-0.6m/s to ensure that the catalyst is in a fluidized state, and to avoid the local stacking of the catalyst that is too dense, resulting in sintering and deactivation of the catalyst. At the same time, cooling water is introduced into the heat exchanger 13 through the inlet 8, and the temperature of the cooling water increases after passing through the heat exchanger 13 and becomes a steam-water mixture exiting the heat exchanger 13 from the outlet 9. In this way, the reduction temperature in the reactor can be controlled between 300-600°C. The reduction time is 3-40 hours, preferably 8-28 hours. After the reduction, the flow rate of the cooling water in the heat exchangers 13 and 17 is increased to cool the reactor to between 230-300°C.

[0052] The vaporized hydrogen and nitrobenzene are fed into the reactor through the reaction raw material gas inlet 1 and the gas distributor 12 until the molar ratio of hydrogen to nitrobenzene is 7:1-20:1, preferably 9:1 15:1. Adjust the cooling water flow in the heat exchangers 13 and 17 so that the temperature in the reactor is maintained at 230-300°C. The weight space velocity in the reactor is controlled to be 0.1-0.5 g nitrobenzene/g catalyst/hour, and the absolute pressure of the reactor is 0.1-1.0 MPa.

[0053] The total feed flow rate of hydrogen and nitrobenzene is controlled to make the actual gas velocity in the reactor reach 0.1-0.9m/s. The reactants are converted into aniline after passing through the first catalyst dense phase zone 14 and the second catalyst dense phase zone 18. The reaction product enters the expansion section 19 of the reactor, enters the cyclone separator 20 from the inlet 6 of the cyclone separator, and the hydrogen, aniline, water and a small amount of impurities exit the reactor from the outlet 7 of the cyclone separator.

[0054] During this process, part of the catalyst in the first catalyst dense phase zone 14 is carried by the gas flow, passes through the second gas distributor 16 and enters the second catalyst dense phase zone 18. When the amount of catalyst in the dense phase zone of the second catalyst is greater than the process allowable value, most of the excess catalyst will enter the overflow device 21 set in the two dense phase zones of the catalyst from the overflow device inlet 5, and then pass through the overflow device. The outlet 3 returns to the first catalyst dense phase zone 14 (in the case of an internal overflow device, the catalyst passes through the overflow device outlet 3 and bypasses the inverted cone structure 22 to return to the catalyst dense phase zone 14). This can effectively ensure the stable operation of the entire reactor. A small part of the catalyst in the dense phase zone of the second catalyst continues to be carried by the gas flow, enters the enlarged section 19 of the reactor, enters the cyclone separator 20 from the inlet 6 of the cyclone separator, and returns to the dense phase zone of the catalyst through the feed leg 15.

[0055] When the catalyst is completely deactivated, it can be discharged from the bottom of the reactor through the catalyst deactivation port 2. The catalyst can be added from the catalyst inlet 4 at an appropriate time.

[0056] Example 1:

[0057] In such figure 1 The reaction is carried out in the two-stage fluidized bed device shown for the gas phase hydrogenation of nitrobenzene to prepare aniline. The feed is hydrogen and nitrobenzene, the molar ratio is 20:1; the operating pressure (absolute pressure) is 0.25MPa; the temperature of the dense phase zone of the first catalyst is 240°C, and the temperature of the dense phase zone of the second catalyst is 270°C; Weight airspeed is 0.26 hours -1 , The actual gas velocity in the dense phase zone of the first catalyst is 0.45m/s. The conversion rate of nitrobenzene is 99.9993%, and the selectivity is 99.90%.

[0058] Example 2:

[0059] In such figure 1 The reaction is carried out in the two-stage fluidized bed device shown for the gas phase hydrogenation of nitrobenzene to prepare aniline. The feed is hydrogen and nitrobenzene, the molar ratio is 15:1; the operating pressure (absolute pressure) is 0.4MPa; the temperature of the dense phase zone of the first catalyst is 240°C, and the temperature of the dense phase zone of the second catalyst is 285°C; The weight airspeed is 0.4 hours -1 , The actual gas velocity in the dense phase zone of the first catalyst is 0.45m/s. The conversion rate of nitrobenzene is 99.999%, and the selectivity is 99.87%.