Method for producing 1,2-dichloroethane

Abstract

To provide a method for producing 1,2-dichloroethane which prevents dew-point corrosion resulting from steam pressure and reaction temperature conditions in a reactor filled with a catalyst, thereby allowing operation under stable, safe, and optimal conditions.SOLUTION: The present invention provides a method for producing 1,2-dichloroethane, wherein: when producing 1,2-dichloroethane from at least ethylene, hydrogen chloride, and oxygen in an oxychlorination catalytic reaction process, the oxychlorination catalytic reaction is induced in a reactor capable of being controlled at least in terms of temperature and steam pressure; the conditions of reaction temperature and steam pressure that achieve a corrosion rate at or below an acceptable limit is estimated from the relationship between reaction temperature, steam pressure, and reactor material corrosion rate in the presence of an oxychlorination catalyst; and control is performed under the estimated conditions.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for producing 1,2-dichloroethane, which is useful as a raw material for vinyl chloride monomer, from ethylene, and more specifically to a method for producing 1,2-dichloroethane in a stable and safe manner by estimating reaction conditions that result in an allowable corrosion rate or less for a reactor and suppressing the adverse effects of corrosion. [Background technology]

[0002] Among the methods for producing vinyl chloride monomer, the balanced oxychlorination process, which consists of (1) the direct chlorination of ethylene to produce 1,2-dichloroethane, (2) the thermal decomposition of 1,2-dichloroethane to produce vinyl chloride monomer, and (3) the oxychlorination of ethylene to produce 1,2-dichloroethane, is widely used in the petrochemical industry.

[0003] Among these, the process for producing 1,2-dichloroethane by the oxychlorination reaction of ethylene is positioned as an important process because it recycles and utilizes the hydrogen chloride by-product from the thermal decomposition reaction of 1,2-dichloroethane.

[0004] There are three known methods for the oxychlorination of ethylene: the air method, which uses air as the oxygen source, the oxygen-enriched method, which uses a small amount of molecular oxygen in air, and the oxygen method, which uses molecular oxygen as the oxygen source. 1,2-dichloroethane is produced from these molecular oxygen, hydrogen chloride, and ethylene, and water is also produced as a by-product. The coexistence of this by-product water and the raw material hydrogen chloride causes constant corrosion of the reaction tube and downstream metal tubes, and although periodic replacement is a common countermeasure, unexpected dew-point corrosion can occur in some cases.

[0005] Therefore, in conventional operation, the temperature of the reaction tube filled with the catalyst was mainly controlled to maintain the temperature above the dew point. Specifically, in normal operation, the dew point temperature at the maximum expected water vapor pressure in the reaction tube was estimated, and the temperature was maintained at a level higher than the dew point to prevent the occurrence of dew point corrosion.

[0006] Furthermore, as a method for producing 1,2-dichloroethane that prevents corrosion, for example, a method has been proposed in which steam and / or steam condensate discharged from a recovery column or a low-boiling component distillation column during the production of 1,2-dichloroethane is neutralized with a basic substance to remove hydrogen chloride and purify the product (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2000-229895 A Summary of the Invention [Problem to be solved by the invention]

[0008] However, the temperature of the reaction tube filled with the catalyst is not uniform due to the heat of reaction. Furthermore, since the water that constitutes the steam is a by-product produced by the reaction, the water vapor pressure changes depending on the progress of the reaction, and the operating conditions are changed based on the production plan, and the catalyst performance also changes over time, so the water vapor pressure is not always constant.

[0009] Therefore, when it becomes difficult to maintain a high temperature equal to or higher than the dew point temperature in the entire reaction tube at the dew point temperature at the maximum water vapor pressure, the production plan must be changed, which causes a decrease in productivity. Also, if the operation is performed based on an overestimated water vapor pressure, inefficient operation due to over-estimated temperature control is forced even in the range where labor-saving operation is possible, and economic efficiency is reduced.

[0010] In addition, when it comes to dew-point corrosion in a reaction tube filled with a catalyst, the effect of the catalyst must be taken into consideration, but there have been no reports of studies clarifying the details of the effects of temperature and water vapor pressure in the presence of a catalyst on the corrosion rate.

[0011] From the above, it is important to clarify the effects of temperature and water vapor pressure on the corrosion rate and to carry out temperature control appropriate to the actual conditions in order to suppress dew-point corrosion and to operate economically in accordance with production plans and with consideration of catalyst performance.

[0012] Furthermore, the method proposed in Patent Document 1 does not solve the problem by changing the conditions, requires a complicated device, and has difficulty in dealing with dew-point corrosion.

[0013] The present invention has been made in consideration of the above-mentioned problems, and its object is to clarify the conditions under which dew-point corrosion occurs due to water vapor pressure and temperature in a reactor packed with a catalyst, and to provide a method for producing 1,2-dichloroethane simply and effectively while suppressing unexpected dew-point corrosion. [Means for solving the problem]

[0014] As a result of extensive investigations aimed at solving the above problems, the present inventors have clarified the relationship between water vapor pressure, temperature and corrosion rate in the presence of an oxychlorination catalyst and have found that by controlling the production conditions based on this relationship, an efficient method for producing 1,2-dichloroethane can be achieved which suppresses unexpected corrosion, particularly dew-point corrosion.

[0015] That is, the present invention relates to a method for producing 1,2-dichloroethane from at least ethylene, hydrogen chloride and oxygen in an oxychlorination catalytic reaction process, characterized in that the oxychlorination catalytic reaction is carried out in a reactor which can be controlled at least by temperature and water vapor pressure, and conditions of reaction temperature and water vapor pressure which give a corrosion rate equal to or lower than an allowable corrosion rate are estimated from the relationship between reaction temperature-water vapor pressure-reactor material corrosion rate in the presence of an oxychlorination catalyst, and control is carried out under said conditions.

[0016] The present invention will be described in detail below.

[0017] The method for producing 1,2-dichloroethane of the present invention is based on an oxychlorination catalytic reaction process for producing 1,2-dichloroethane from at least ethylene, hydrogen chloride and oxygen, and the oxychlorination catalytic reaction is carried out in a reactor that can be controlled at least by temperature and water vapor pressure.The method stably produces 1,2-dichloroethane by estimating the reaction temperature and water vapor pressure conditions that are equal to or lower than the allowable corrosion rate from the relationship between reaction temperature, water vapor pressure and corrosion rate of the reactor material in the presence of the oxychlorination catalyst, and controlling the reaction temperature and water vapor pressure under the conditions, and particularly relates to a production method that can suppress abnormal corrosion due to dew-point corrosion.

[0018] The reactor in the production method of the present invention may be any reactor capable of producing 1,2-dichloroethane in an oxychlorination catalytic reaction process and capable of controlling the reaction at least by temperature and water vapor pressure, and examples thereof include reactors having a fixed-bed flow-type catalytic reaction tower or a fluidized-bed flow-type catalytic reaction tower, among which a reactor having a fixed-bed flow-type catalytic reaction tower is preferred, and a multi-tubular fixed-bed fluidized reaction tower in which a plurality of reaction tubes are installed in parallel and each reaction tube is filled with a catalyst to form a reaction tower is further preferred. The temperature control method may be a known heat medium circulation method or a boiling water type.

[0019] The material of the reactor, particularly the reaction tube in the reaction tower in which the catalyst for oxychlorination is packed, may be any material that has corrosion resistance in the catalytic reaction process for oxychlorination, such as stainless steel, which is a type of alloy in which iron contains a certain amount of chromium and is defined as an alloy steel with a chromium content of 10.5% by weight or more and a carbon content of 1.2% by weight or less. Known stainless steels include austenitic, martensitic and ferritic stainless steels, such as SUS304, SUS310 and SUS316.

[0020] The catalytic reaction process for oxychlorination in the present invention is a process for producing 1,2-dichloroethane from at least ethylene, hydrogen chloride and oxygen in the presence of a catalyst for oxychlorination. The catalyst for oxychlorination packed in the reaction tube of the reaction tower in this case may be, for example, a catalyst containing copper chloride and at least one chloride of an alkali metal and an alkaline earth metal. In particular, a cylindrical alumina-supported catalyst for oxychlorination containing copper chloride and at least one chloride of an alkali metal and an alkaline earth metal is preferred.

[0021] The copper chloride constituting the catalyst for oxychlorination can be copper(I) chloride and / or copper(II) chloride, and among them, copper(II) chloride is preferred since it is a catalyst for oxychlorination with excellent stability. The amount of copper chloride supported on the catalyst for oxychlorination is not limited as long as the catalyst for oxychlorination acts as a catalyst, and is preferably 8 to 25% by weight, particularly preferably 10 to 20% by weight, since it is a catalyst for oxychlorination with excellent catalytic activity.

[0022] Examples of the alkali metal chloride constituting the oxychlorination catalyst include lithium chloride, sodium chloride, potassium chloride, rubidium chloride, cesium chloride, etc. Examples of the alkaline earth metal chloride include magnesium chloride, calcium chloride, strontium chloride, barium chloride, etc. The amount of the alkali metal and / or alkaline earth metal chloride supported is preferably 1 to 20% by weight, particularly preferably 1 to 10% by weight, since this contributes to the stability of copper chloride and results in an oxychlorination catalyst with excellent catalytic activity.

[0023] The shape of the catalyst for oxychlorination is not particularly limited, and may be, for example, a spherical shape, a cylindrical shape, a cylindrical shape, or a honeycomb shape. Furthermore, the size of the catalyst is not particularly limited, and it is preferably a cylindrical shape with an outer diameter of 2 to 8 mm, an inner diameter of 1 to 7 mm, and a length of 2 to 8 mm, and more preferably an outer diameter of 3 to 7 mm, an inner diameter of 1 to less than 3 mm, and a length of 3 to 6 mm.

[0024] In order to enhance the heat removal effect, a diluent may be mixed into the catalyst layer in the reaction tube as necessary. As the diluent, any material may be used as long as it does not affect the oxychlorination reaction, and for example, silica, alumina, alumina-silica, magnesia, carbon, etc. are used. In addition, there is no particular limitation on the shape of the diluent, and for example, a spherical shape, a cylindrical shape, a cylindrical shape, a honeycomb shape, etc. are used. Furthermore, there is no particular limitation on the size of the diluent, and among them, it is preferable that the diluent has the same size as the oxychlorination catalyst because it can be uniformly filled with the oxychlorination catalyst, and for example, it is preferable that the diluent has a cylindrical shape with an outer diameter of 2 to 8 mm, an inner diameter of 1 to 7 mm, and a length of 2 to 8 mm, and more preferably an outer diameter of 3 to 7 mm, an inner diameter of less than 1 to 3 mm, and a length of 3 to 6 mm.

[0025] The catalytic oxychlorination process of the present invention is a reaction for producing 1,2-dichloroethane by supplying at least ethylene, hydrogen chloride and oxygen to a reactor filled with a catalyst for oxychlorination, and air or molecular oxygen can be used as the oxygen source. The ethylene, hydrogen chloride and oxygen supplied to the reactor can be used as they are or diluted with an inert gas. The type of inert gas is not particularly limited, and for example, one or a mixture of nitrogen, helium, argon and carbon dioxide can be used. In addition, oxygen-enriched air can be used as the oxygen source air. The oxygen content of the molecular oxygen-enriched air is preferably 21 to 60% by volume, more preferably 30 to 35% by volume.

[0026] The reaction temperature in the reactor is not particularly limited as long as it is possible to suppress dew-point corrosion, and is preferably 100°C to 400°C, and particularly preferably 150°C to 350°C, since conversion to 1,2-dichloroethane is efficient. There is also no particular limitation on the reaction pressure, which is usually 0.01 to 2 MPa, and preferably 0.05 to 1 MPa, in absolute pressure. Furthermore, the gas hourly space velocity, particularly the gas hourly space velocity (GHSV) during a fixed bed flow reaction, is preferably 10 hr since conversion to 1,2-dichloroethane is efficient. -1 ~10000hr -1 , and more preferably 30 hours-1 ~8000hr -1 Here, the gas hourly space velocity (GHSV) represents the amount of ethylene supplied per unit catalyst volume per unit time (hr).

[0027] The method for producing 1,2-dichloroethane of the present invention estimates the reaction temperature and water vapor pressure conditions that are below the allowable corrosion rate from the relationship between reaction temperature-water vapor pressure-reactor material corrosion rate in the presence of an oxychlorination catalyst during production, particularly the optimal reaction temperature and water vapor pressure, and continues the production of 1,2-dichloroethane under these conditions, thereby producing 1,2-dichloroethane stably, and is a production method that particularly suppresses dew-point corrosion. In this case, it is necessary to grasp the relationship between reaction temperature-water vapor pressure-reactor material corrosion rate in the presence of an oxychlorination catalyst in advance, and there is no particular restriction on the method for estimating the corrosion rate from the temperature and water vapor pressure. For example, a method of estimating the corrosion rate from a corrosion test in which a test piece made of a metal material constituting the reaction tube, such as SUS304, SUS310, SUS316, etc., is loaded into the reaction tube of a catalytic reaction tower together with an oxychlorination catalyst and held for a certain period of time, and the corrosion rate is measured from the weight difference before and after the test can be mentioned. Since the corrosion rate varies depending on the presence or absence of a catalyst for oxychlorination, it is meaningless to obtain a relationship in the absence of a catalyst for oxychlorination.

[0028] As a test method using the test piece, a method of loading the test piece into a reaction tube in a catalytic reaction tower may be used, but it is preferable to estimate using a laboratory-level test device as a model. When using a test device as a model, it is more preferable to select a material for the reaction tube that is less corroded than the material of the test piece, and examples of such a material include Hastelloy, nickel, and glass.

[0029] When loading a test piece into a reaction tube using a model test device, it is possible to grasp the relationship between reaction temperature, water vapor pressure, and reactor material corrosion rate closer to that in an actual reaction field. Therefore, the test piece is surrounded by an oxychlorination catalyst and the corrosion test is performed in the presence of the oxychlorination catalyst. In addition, gas such as ethylene, which is not related to the corrosive action, can be used instead of an inert gas such as nitrogen. The water vapor may be water produced by the oxychlorination reaction or may be supplied to the reaction tube as water vapor, and the test device may be improved so that the water vapor is vaporized to water vapor before reaching the test piece.

[0030] Using such a test device, corrosion tests can be conducted by varying the temperature and water vapor pressure, and a correlation diagram showing the relationship between the obtained values ​​of temperature, water vapor pressure, and corrosion rate (of the reactor material) can be created. Effect of the Invention

[0031] When producing 1,2-dichloroethane from at least ethylene, hydrogen chloride and oxygen, the reaction temperature and water vapor pressure conditions that provide an allowable corrosion rate or less can be estimated from the relationship between reaction temperature, water vapor pressure and corrosion rate of reactor material in the presence of an oxychlorination catalyst, and control is performed under these conditions. This makes it possible to suppress unexpected corrosion of the reaction tube filled with the oxychlorination catalyst, such as dew-point corrosion, and to produce 1,2-dichloroethane through efficient operation in accordance with production plans, taking into account economical operation and catalyst performance. EXAMPLES

[0032] The present invention will be described in detail below with reference to examples, but is not limited thereto. A correlation diagram showing the relationship between temperature, water vapor pressure, and corrosion rate will be experimentally created and described in detail, but as with the examples, the test method and the like for the correlation diagram are not limited thereto.

[0033] The corrosion test method and catalyst preparation method used in the examples are described below.

[0034] <Preparation of oxychlorination catalyst> A cylindrical alumina carrier (outer diameter 5.1 mm, inner diameter 1.9 mm, length 5.1 mm) was allowed to fully absorb water. 75 g of the alumina carrier was immersed in 200 ml of an immersion solution with a concentration of CuCl2 = 218 g / l and KCl = 134 g / l. After immersion at room temperature for 2 hours, the alumina carrier was removed from the immersion solution and dried at a temperature of 100 ° C or higher using a muffle furnace. Then, it was calcined at 150 to 400 ° C for 5 hours to prepare an oxychlorination catalyst carrying 13.8 wt % CuCl2 and 5.5 wt % KCl.

[0035] The catalyst was crushed in a mortar and sized to a particle size of 0.85 to 1.4 mm.

[0036] <Corrosion test method> The corrosion test was performed using a fixed-bed gas-phase flow-type test apparatus using a Hastelloy metal tube (inner diameter 16 mm, length 600 mm). A SUS304 test piece (14 x 35 x 3 mm) was loaded in the middle of the Hastelloy metal tube, and an oxychlorination catalyst with a particle size of 0.85 to 1.4 mm was packed around it. After reaching a predetermined temperature under a pressurized condition of 0.43 MPa, water was supplied using a pump while supplying nitrogen. A supply port was installed so that the supplied water reached a predetermined temperature by the time it reached the metal test piece and evaporated into water vapor. Hydrogen chloride, oxygen, and nitrogen were then supplied. The test was started with a total gas amount including water vapor set to 250 ml / min. The corrosion test was performed for 24 hours. After the test was completed, the test piece was collected and the corrosion rate (mm / y) was calculated from the weight difference before and after the test.

[0037] <Correlation diagram showing the relationship between temperature, water vapor pressure and corrosion rate in corrosion tests> The corrosion test was carried out according to the method described above. The weight of the SUS304 test piece before the test was 10.20924g, and the temperature of the corrosion test was 222℃, with hydrogen chloride, oxygen, water vapor and nitrogen supplied at 69ml / min, 1.6ml / min, 45ml / min and 135ml / min, respectively. The total pressure was 0.43MPa and the water vapor pressure was 0.076MPa. The corrosion test was carried out for 24 hours. After the test, the test piece was collected and its weight after the test was measured, which was 10.20829g. The corrosion rate of 0.035mm / y was obtained from the weight difference before and after the test.

[0038] Similarly, the corrosion rate was determined by corrosion tests at different temperatures (214°C, 205°C) and with different water vapor pressures, with the amounts of hydrogen chloride, water vapor, and nitrogen supplied set to the values ​​shown in Table 1. Also, to confirm the effect of the oxychlorination catalyst on corrosion, a test was conducted at 214°C without the catalyst being loaded. The results are shown in Table 1. From these results, a correlation diagram was created showing the relationship between temperature, water vapor pressure, and corrosion rate (SUS304). This correlation diagram is shown in Figure 1.

[0039] [Table 1]

[0040] Example 1 In an oxychlorination reactor for producing 1,2-dichloroethane, which has a SUS304 fixed-bed flow-type reaction tube filled with an oxychlorination catalyst, ethylene, hydrogen chloride, oxygen and nitrogen were supplied to perform normal operation with a gas composition that would result in a lower limit control value of the reaction temperature of 205°C and a water vapor pressure of 0.041 MPa. The corrosion rate in this case was predicted to be 0.04 mm / y from the correlation diagram shown in Figure 1, so the control value of the corrosion rate was set to less than 0.05 mm / y.

[0041] Later, due to a change in plans to increase production of 1,2-dichloroethane, it was necessary to change the gas composition to one with a water vapor pressure of 0.060MPa. Therefore, the lower limit control value to maintain a corrosion rate of 0.04mm / y, which is below the control value, was reset to 214°C based on the correlation diagram shown in Figure 1, and production was continued. During the one-year operation period, the normal operation period and the increased production period were carried out in a 1:1 ratio, making it possible to produce according to the increased production plan.

[0042] When operation was stopped, the wall thickness of the reaction tube was measured and the corrosion rate was found to be 0.04 mm / y.

[0043] Example 2 In an oxychlorination reactor for producing 1,2-dichloroethane, which has a SUS304 fixed-bed flow-type reactor tube filled with an oxychlorination catalyst, ethylene, hydrogen chloride, oxygen and nitrogen were supplied to the reactor so that the lower limit of the reaction temperature was 205°C and the gas composition was 0.052 MPa. The total pressure was 0.43 MPa and the corrosion rate was controlled to be less than 0.05 mm / y.

[0044] Later, the plan was changed to increase production of 1,2-dichloroethane, and the gas flow rate was increased without changing the gas composition. At this time, the total pressure increased to 0.50 MPa. Due to the increase in total pressure caused by the increase in gas flow rate, the water vapor pressure was predicted to increase to 0.060 MPa.

[0045] Therefore, the lower limit control value for maintaining a corrosion rate of 0.04 mm / y, which is below the control value, was reset to 214°C based on the correlation diagram shown in Figure 1, and production was continued. During the one-year operation period, the normal operation period and the increased production period were performed in a ratio of 1:2, making it possible to produce according to the increased production plan.

[0046] When operation was stopped, the wall thickness of the reaction tube was measured and the corrosion rate was found to be 0.04 mm / y.

[0047] Comparative Example 1 The lower limit control value was not changed when the production expansion plan was changed, and production was continued at 205°C. In the same manner as in Example 1, except that the normal operation period and the operation period with increased conversion rate were in a 1:1 ratio, production was carried out for an operation period of one year.

[0048] When operation was stopped, the thickness of the reaction tube was measured and the corrosion rate was found to be 0.064 mm / y, which indicated that the operation had exceeded the control value for the corrosion rate. With this operating method, the equipment had deteriorated significantly due to corrosion of the reaction tube, making continuous operation difficult.

[0049] Comparative Example 2 Except for continuing production at 205°C without changing the lower limit control value when the production expansion plan was changed, production was carried out for one year in the same manner as in Example 1, with the ratio of the normal operation period to the operation period with increased conversion rate being 1:2. The total pressure after the production expansion plan at this time increased to 0.50 MPa.

[0050] When operation was stopped, the thickness of the reaction tube was measured and the corrosion rate was found to be 0.072 mm / y, which indicated that the operation had exceeded the control value for the corrosion rate. With this operating method, the equipment had deteriorated significantly due to corrosion of the reaction tube, making continuous operation difficult. [Industrial Applicability]

[0051] In the method for producing 1,2-dichloroethane of the present invention, even if a production plan or the like is changed, the reaction temperature and water vapor pressure conditions that provide an allowable corrosion rate or less can be estimated from the relationship between the reaction temperature, water vapor pressure, and corrosion rate of the reactor material in the presence of the catalyst for oxychlorination are estimated, and control is performed under those conditions. This makes it possible to suppress unexpected corrosion of the reaction tube filled with the catalyst for oxychlorination, such as dew-point corrosion, and to produce 1,2-dichloroethane by economical operation according to the production plan and efficient operation taking into account the catalyst performance. [Brief description of the drawings]

[0052] [Figure 1];Correlation diagram showing the relationship between temperature, water vapor pressure, and corrosion rate (SUS304) obtained from corrosion tests.

Claims

1. A method for producing 1,2-dichloroethane from at least ethylene, hydrogen chloride and oxygen in an oxychlorination catalytic reaction process, characterized in that the oxychlorination catalytic reaction is carried out in a reactor which can be controlled at least by temperature and water vapor pressure, and conditions of reaction temperature and water vapor pressure which result in an allowable corrosion rate or less are estimated from the relationship between reaction temperature-water vapor pressure-reactor material corrosion rate in the presence of an oxychlorination catalyst, and control is carried out under said conditions.

2. The method for producing 1,2-dichloroethane according to claim 1, wherein the reactor is a fixed-bed flow-type reaction tower.

3. 2. The process for producing 1,2-dichloroethane according to claim 1, characterized in that the reactor is a reactor having a stainless steel tube for packing the oxychlorination catalyst.

4. 2. The method for producing 1,2-dichloroethane according to claim 1, wherein the reactor is a reactor having a tube selected from the group consisting of a SUS304 tube, a SUS310 tube and a SUS316 tube for packing a catalyst for oxychlorination.

5. 2. The process for producing 1,2-dichloroethane according to claim 1, wherein the catalyst for oxychlorination is an alumina-supported catalyst for oxychlorination having a cylindrical shape and containing copper chloride and at least one chloride of an alkali metal and an alkaline earth metal.

Images