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

Abstract

The invention discloses a device and method to prepare aniline by the nitrobenzene gas phase hydrogenization, and the device mainly includes a fluidized bed reactor set at the raw material gas inlet at the bottom of the reactor, a first gas distributor on the top of the gas inlet, a second gas distributor separating the reactor in the middle of axial height of the reactor into two catalyst dense phase regions, and heat exchangers in two catalyst dense phase regions; catalyst overflow device connected with two catalyst dense phase regions and gas-solid separator. It also discloses a method to prepare aniline by the device, mainly including: the steps of controlling the mol ratio of hydrogen gas to nitrobenzene, controlling the temperature in two catalyst dense phase regions, etc. It has advantages of large reactor operation flexibility, high nitrobenzene conversion, high aniline production selectivity, high product purity, etc.

Description

technical field

[0001] The invention relates to equipment and a process method for preparing aniline by gas-phase hydrogenation of nitrobenzene, and belongs to the technical field of chemical process and equipment. Background technique

[0002] Aniline is a very important class of chemical products. With the wide application of polyurethane in the fields of construction, automobiles, electrical appliances and packaging materials, the output of methyl diisocyanate (MDI for short, prepared from aniline), the main raw material of polyurethane, has increased rapidly, resulting in a substantial increase in the consumption of aniline. . At present, aniline is mainly used in the production of MDI and rubber additives, and can also be used in the fields of pesticides, organic pigments and pharmaceuticals. The world's annual demand is about 3 million tons.

[0003] At present, there are three methods for the industrial production of aniline, namely, gas-phase hydrogenation of nitro...

Examples

preparation example Construction

[0050] The processing method of preparing aniline of the present invention is specifically as follows:

[0051] The metal-loaded catalyst with an average particle diameter of 45-300 microns enters the reactor from the catalyst inlet 4 . In order to make the catalyst fully enter the reactor, nitrogen or air is fed through the gas distributor 12 through the gas distributor 12 at the gas raw material inlet 1 at the bottom of the reactor when adding the catalyst. 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 first catalyst dense phase zone 14 . After loading the catalyst into the reactor, pass inert gas to replace the gas in the reactor to an oxygen-free state. During this period, the temperature is gradually raised to 200-300°C, and then hydrogen gas is switched in for catalyst reduction. During the reduction, the gas velocity in the reactor is controlled between 0.05-0.6m / ...

Embodiment 1

[0057] in such as figure 1 The reaction is carried out in the two-stage fluidized bed device shown for the preparation of aniline by gas-phase hydrogenation of nitrobenzene. The feed is hydrogen and nitrobenzene, and the molar ratio is 20:1; the operating pressure (absolute pressure) is 0.25MPa; the temperature of the first catalyst dense-phase zone is 240°C, and the temperature of the second catalyst dense-phase zone is 270°C; Weight airspeed of 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%.

Embodiment 2

[0059] in such as figure 1 The reaction is carried out in the two-stage fluidized bed device shown for the preparation of aniline by gas-phase hydrogenation of nitrobenzene. The feed is hydrogen and nitrobenzene, and the molar ratio is 15:1; the operating pressure (absolute pressure) is 0.4MPa; the temperature of the first catalyst dense-phase zone is 240°C, and the temperature of the second catalyst dense-phase zone is 285°C; Weight airspeed of 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%.

technical field

[0001] The invention relates to equipment and a process method for preparing aniline by gas-phase hydrogenation of nitrobenzene, and belongs to the technical field of chemical process and equipment. Background technique

[0002] Aniline is a very important class of chemical products. With the wide application of polyurethane in the fields of construction, automobiles, electrical appliances and packaging materials, the output of methyl diisocyanate (MDI for short, prepared from aniline), the main raw material of polyurethane, has increased rapidly, resulting in a substantial increase in the consumption of aniline. . At present, aniline is mainly used in the production of MDI and rubber additives, and can also be used in the fields of pesticides, organic pigments and pharmaceuticals. The world's annual demand is about 3 million tons.

[0003] At present, there are three methods for the industrial production of aniline, namely, gas-phase hydrogenation of nitro...

Examples

preparation example Construction

[0050] The processing method of preparing aniline of the present invention is specifically as follows:

[0051] The metal-loaded catalyst with an average particle diameter of 45-300 microns enters the reactor from the catalyst inlet 4 . In order to make the catalyst fully enter the reactor, nitrogen or air is fed through the gas distributor 12 through the gas distributor 12 at the gas raw material inlet 1 at the bottom of the reactor when adding the catalyst. 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 first catalyst dense phase zone 14 . After loading the catalyst into the reactor, pass inert gas to replace the gas in the reactor to an oxygen-free state. During this period, the temperature is gradually raised to 200-300°C, and then hydrogen gas is switched in for catalyst reduction. During the reduction, the gas velocity in the reactor is controlled between 0.05-0.6m / ...

Embodiment 1

[0057] in such as figure 1 The reaction is carried out in the two-stage fluidized bed device shown for the preparation of aniline by gas-phase hydrogenation of nitrobenzene. The feed is hydrogen and nitrobenzene, and the molar ratio is 20:1; the operating pressure (absolute pressure) is 0.25MPa; the temperature of the first catalyst dense-phase zone is 240°C, and the temperature of the second catalyst dense-phase zone is 270°C; Weight airspeed of 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%.

Embodiment 2

[0059] in such as figure 1 The reaction is carried out in the two-stage fluidized bed device shown for the preparation of aniline by gas-phase hydrogenation of nitrobenzene. The feed is hydrogen and nitrobenzene, and the molar ratio is 15:1; the operating pressure (absolute pressure) is 0.4MPa; the temperature of the first catalyst dense-phase zone is 240°C, and the temperature of the second catalyst dense-phase zone is 285°C; Weight airspeed of 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%.

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