A method for preparing ethylene by low-temperature oxidation of ethane

Abstract

The present invention belongs to the field of chemical technology, and specifically relates to a method for preparing ethylene by low-temperature oxidation of ethane. The method is characterized in that ethane and carbon dioxide are first introduced into a pressurized mixing tank, and after being heated by a preheater, they are introduced into the inner tube of a jacketed reactor from the top, and the inner tube is filled with macroporous alumina beads loaded with vanadium; then the gas is mixed with water vapor and introduced into the outer tube, and the outer tube is a grid-shaped stainless steel hollow structure and a reverse reaction. The method of the present invention greatly reduces the temperature of preparing ethylene from ethane, reduces the reaction energy consumption, and obtains a higher ethane conversion rate and ethylene selectivity, with a yield of up to 76%.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical engineering, and specifically relates to a method for preparing ethylene by low-temperature oxidation of ethane. Background Art

[0002] Ethylene production is one of the important indicators of a country's petrochemical development level. Its production currently mainly comes from the cracking process of naphtha or light oil. As oil resources become increasingly scarce, the use of abundant and cheap ethane dehydrogenation to produce ethylene has attracted more and more attention.

[0003] Although ethane dehydrogenation to ethylene has been industrialized, it mainly uses steam cracking technology. However, due to the limitation of thermodynamic equilibrium conversion rate, the reaction temperature is basically above 850°C, and the energy consumption is particularly high. Therefore, introducing mild oxidant carbon dioxide into the reaction system becomes a feasible experimental scheme. It does not cause deep oxidation of ethane and can ensure the selectivity of the product ethylene; at the same time, it provides part of the energy for the dehydrogenation endothermic reaction and reduces the reaction temperature, which meets the current environmental protection needs.

[0004] However, although adding carbon dioxide as an oxidant in the process of ethane to ethylene can reduce the reaction energy consumption, the selectivity and conversion rate are relatively low, so a catalyst needs to be added. However, the presence of the catalyst also increases the number of side reactions. Therefore, from the perspective of energy consumption and reaction efficiency, low-temperature carbon dioxide oxidation and dehydrogenation of ethane to produce ethylene is an important research direction for us. Summary of the invention

[0005] The purpose of the present invention is to provide a method for preparing ethylene by low-temperature oxidation of ethane, thereby reducing the energy consumption of ethane oxidative cracking and improving the reaction efficiency.

[0006] The present invention proposes a method for preparing ethylene by low-temperature oxidation of ethane, which comprises the following steps: firstly introducing ethane and carbon dioxide into a pressurized mixing tank, then passing through a preheater for heating, and then passing through an inner tube of a jacketed reactor from the top, wherein the inner tube is provided with macroporous alumina beads loaded with vanadium, and then the gas flows through the bottom of the reaction tube, wherein a water vapor injection device is installed at the bottom of the reaction tube, and the gas mixed with the water vapor is passed through an outer tube, which is a grid-like stainless steel hollow structure, and the gas after the reaction is sent out from the top.

[0007] Furthermore, in the preparation method of the present invention, the pressure of the mixing tank is 0.1-0.4 MPa, and the temperature of the preheater is 200-250°C.

[0008] The preparation method of the invention adopts a jacketed reactor, the reaction temperature of the inner tube of the reactor is 550-600°C, the reaction temperature of the outer tube is 600-650°C, and the ratio of the inner tube diameter to the outer tube diameter is 1:2.

[0009] In the preparation method of the present invention, the catalyst used in the inner tube is a perforated alumina catalyst loaded with 1-3% vanadium content.

[0010] In the preparation method of the present invention, the outer tube adopts a 3mm*3mm 2520 stainless steel mesh with a mesh wall thickness of 1mm.

[0011] In the preparation method of the present invention, a water vapor injection device is provided.

[0012] Beneficial effects of the present invention: The catalyst prepared by the method of the present invention greatly reduces the reaction temperature of preparing ethylene from ethane and reduces the reaction energy consumption; utilizing the reaction characteristics, the reaction of preparing ethylene from ethane at low temperature has a higher ethane conversion rate and ethylene selectivity, and the yield can be as high as 76%. DETAILED DESCRIPTION

[0013] The present invention is further described below in conjunction with embodiments, but the protection scope of the present invention is not limited thereto.

[0014] Example 1

[0015] Through the mass flowmeter, ethane with a flow rate of 100ml / min and carbon dioxide with a flow rate of 200ml / min are first introduced into the pressurized mixing tank, and the reaction pressure is set to 0.1MPa. Then, the temperature is raised to 200℃ through the preheater, and then introduced into the inner tube of the jacket reactor with an inner diameter of 5cm from the top. The inner tube is equipped with macroporous alumina beads with a load of 1% vanadium content, the diameter of the beads is 4mm, and the reaction temperature is 600℃; then the gas flows through the bottom of the reaction tube equipped with a water vapor injection device, the water vapor temperature is 600℃, and the water pump flow rate is 1ml / min. The gas mixed with water vapor is introduced into the outer tube of 2520 stainless steel hollow mesh designed to be 3mm*3mm in size and 1mm in mesh wall thickness. The outer tube diameter is 10cm and the reaction temperature is 650℃; after the reaction, the gas is sent out from the top. The measured ethane conversion rate is 73%, the ethylene selectivity is 77%, the carbon dioxide conversion rate is 37%, and the carbon deposition rate is 0.8%.

[0016] Example 2

[0017] Through the mass flowmeter, ethane with a flow rate of 100ml / min and carbon dioxide with a flow rate of 200ml / min are first introduced into the pressurized mixing tank, and the reaction pressure is set to 0.4MPa. Then, the temperature is raised to 250℃ through the preheater, and then introduced into the inner tube of the jacket reactor with an inner diameter of 5cm from the top. The inner tube is equipped with macroporous alumina beads with a load of 3% vanadium content, the diameter of the beads is 6mm, and the reaction temperature is 550℃; then the gas flows through the bottom of the reaction tube equipped with a water vapor injection device, the water vapor temperature is 550℃, and the water pump flow rate is 1ml / min. The gas mixed with water vapor is introduced into the outer tube of 2520 stainless steel hollow mesh designed to be 3mm*3mm in size and 1mm in mesh wall thickness. The outer tube diameter is 10cm and the reaction temperature is 600℃; after the reaction, the gas is sent out from the top. The measured ethane conversion rate is 82%, the ethylene selectivity is 93%, the carbon dioxide conversion rate is 18%, and the carbon deposition rate is 0.4%.

[0018] Example 3

[0019] Through the mass flowmeter, ethane with a flow rate of 100ml / min and carbon dioxide with a flow rate of 200ml / min are first introduced into the pressurized mixing tank, and the reaction pressure is set to 0.2MPa. Then, the temperature is raised to 250℃ through the preheater, and then introduced into the inner tube of the jacket reactor with an inner diameter of 5cm from the top. The inner tube is equipped with macroporous alumina beads with a load of 2% vanadium content, the diameter of the beads is 8mm, and the reaction temperature is 600℃; then the gas flows through the bottom of the reaction tube equipped with a water vapor injection device, the water vapor temperature is 600℃, and the water pump flow rate is 1ml / min. The gas mixed with water vapor is introduced into the outer tube of 2520 stainless steel hollow mesh designed with a size of 3mm*3mm and a mesh wall thickness of 1mm. The outer tube diameter is 10cm and the reaction temperature is 650℃; after the reaction, the gas is sent out from the top. The measured ethane conversion rate is 75%, the ethylene selectivity is 72%, the carbon dioxide conversion rate is 31%, and the carbon deposition rate is 1.0%.

[0020] Example 4

[0021] Through the mass flowmeter, ethane with a flow rate of 100ml / min and carbon dioxide with a flow rate of 200ml / min are first introduced into the pressurized mixing tank, and the reaction pressure is set to 0.2MPa. Then, the temperature is raised to 250℃ through the preheater, and then introduced into the inner tube of the jacket reactor with an inner diameter of 5cm from the top. The inner tube is equipped with macroporous alumina beads with a load of 2% vanadium content, the diameter of the beads is 8mm, and the reaction temperature is 600℃; then the gas flows through the bottom of the reaction tube equipped with a water vapor injection device, the water vapor temperature is 600℃, and the water pump flow rate is 1ml / min. The gas mixed with water vapor is introduced into the outer tube of 2520 stainless steel hollow mesh designed with a size of 3mm*3mm and a mesh wall thickness of 1mm. The outer tube diameter is 10cm and the reaction temperature is 650℃; after the reaction, the gas is sent out from the top. The measured ethane conversion rate is 79%, the ethylene selectivity is 81%, the carbon dioxide conversion rate is 28%, and the carbon deposition rate is 1.1%.

[0022] Example 5

[0023] Ethane with a flow rate of 100 ml / min was introduced into the pressurized mixing tank through a mass flow meter, and the reaction pressure was set to 0.4 MPa, and then heated to 250°C through a preheater; it was simultaneously introduced into a fixed bed reactor with a 5 cm inner diameter and macroporous alumina beads loaded with 3% vanadium content, the diameter of the beads was 6 mm, and the reaction temperature was 600°C. The measured ethane conversion rate was 32%, the ethylene selectivity was 86%, and the carbon deposition rate was 0.2%.

[0024] Example 6

[0025] Ethane at a flow rate of 100 ml / min and carbon dioxide at 200 ml / min were first introduced into the pressurized mixing tank through a mass flow meter, and the reaction pressure was set to 0.4 MPa. Then, the temperature was raised to 250°C through a preheater, and then introduced from the top into a fixed bed reactor with a macroporous alumina ball with an inner diameter of 5 cm and loaded with 3% vanadium content. The ball diameter was 6 mm and the reaction temperature was 550°C. The measured ethane conversion rate was 46%, the ethylene selectivity was 67%, the carbon dioxide conversion rate was 7%, and the carbon deposition rate was 0.4%.

Claims

1. A method for preparing ethylene by low temperature oxidation of ethane, characterized in that Ethane and carbon dioxide are introduced into a pressurized mixing tank for pressurized mixing, and then heated by a preheater, and then introduced into the inner tube of the jacketed reactor from the top, wherein the inner tube is equipped with macroporous alumina beads loaded with vanadium, and the gas is mixed with water vapor at the bottom of the reaction tube and then introduced into the outer tube, which is a grid-shaped stainless steel hollow structure, and the gas is sent out from the top after the reaction; a water vapor injection device is installed at the bottom of the reaction tube; the ratio of the inner tube diameter to the outer tube diameter is 1:2; the diameter of the macroporous alumina beads is 4-8mm; the vanadium loading of the macroporous alumina beads in the inner tube is 1-3%; the stainless steel mesh size of the outer tube is 3mm*3mm, and the mesh wall thickness is 1mm; The mixing tank pressure is 0.1-0.4MPa; The preheater temperature is 200-250°C; The reaction temperature of the inner tube of the reactor is 550-600°C, and the reaction temperature of the outer tube is 600-650°C.

2. The method for preparing ethylene by low temperature oxidation of ethane as claimed in claim 1, characterized in that The outer tube stainless steel grid is made of 2520 stainless steel.