A method for dehydration of isopropanol, a method for producing propylene, and a production apparatus

Abstract

The present invention relates to a method for dehydrating isopropanol to produce propylene, a method for producing propylene from acetone as a raw material including the process, and a related production apparatus. The dehydration method of the present invention includes a step of dehydrating a raw material containing isopropanol in the presence of a dehydration catalyst containing alumina to produce a product containing propylene, wherein the water content of the raw material is 0.1-10.0 wt% (, relative to the total mass of the raw material being 100 wt%), and the content of C3-C4 unsaturated impurities in the product is 30 ppm or less. According to the present invention, the production of undesirable by-products can be significantly suppressed while improving the conversion rate of isopropanol.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of chemical industry, and relates to a method for preparing propylene by dehydrating isopropyl alcohol, a method for preparing propylene from acetone as raw material and a related production device. BACKGROUND

[0002] In recent years, the global demand for phenol has increased significantly. In 2017, the global total capacity of phenol reached 1363.7 million tons per year, which was 47% higher than that in 2009. According to statistics, in recent years, many new phenol and acetone devices have been put into production globally, especially in Asia and China. The existing phenol production mainly adopts cumene oxidation process, and acetone is a by-product of the process. With the strong global demand for phenol, the problem is that the rigid supply of acetone produced by the existing phenol and ketone device is too large, and there is a situation of regional and even global excess of acetone.

[0003] In view of the current situation of large capacity, large market supply and demand, and low price of acetone in China and even in the world, and the shortage of propylene resources and high price, the process of preparing propylene by hydrogenation and dehydration of acetone is integrated with the phenol and ketone device, which can solve the problem of low price and poor sales of acetone, and at the same time provides a technical solution for adjusting the product ratio of the phenol and ketone device. Especially in the period when the price difference between propylene and acetone is large, the market competitiveness of phenol and its downstream products can be significantly improved, which has significant economic benefits.

[0004] CN102690172A proposes a method for preparing isopropyl alcohol by hydrogenation of acetone. The method is to solve the problem of preparing isopropyl alcohol by hydrogenation of acetone and removing impurities, especially water, from isopropyl alcohol. The method is to convert acetone into isopropyl alcohol by hydrogenation, then use diisopropylamine as an azeotrope agent to carry out water in isopropyl alcohol, and then remove heavy components to obtain qualified isopropyl alcohol product.

[0005] CN102728361A proposes a catalyst for preparing isopropyl alcohol by hydrogenation of acetone and its application. The method uses alumina with a BET specific surface area of 150-359 m 2 / g and a pore volume of 0.30-0.8 m 2 / g as a carrier, contains 8%-25% of nickel, and the surface area of nickel is 10-30 m 2 / g total nickel content.

[0006] CN103772145B proposes a method for separating acetone hydrogenation product to isopropanol, which includes: the acetone hydrogenation product is subjected to azeotropic rectification and extractive rectification to obtain high-purity isopropanol. Specifically, it includes: (1) the acetone hydrogenation product enters the rectification tower for azeotropic rectification, the azeotrope is collected from the top of the tower, the heavy component is obtained from the tower bottom, and the isopropanol product is collected from the side line of the tower body; (2) the azeotrope collected from the top of the rectification tower enters the recovery tower, and is subjected to extractive rectification by using an extractant, the reflux including acetone and isopropanol is collected from the top of the tower and is sent back to the reactor for recycling, and the water solution rich in the extractant is collected from the tower bottom; (3) the stream from the tower bottom of the recovery tower enters the dehydration tower, and the extractant is collected from the tower bottom and is recycled to the recovery tower.

[0007] CN103508833B proposes a method for preparing propylene by dehydrating isopropanol, which includes: under the dehydration reaction conditions of isopropanol, isopropanol is contacted with a catalyst to obtain propylene by dehydration. The catalyst is prepared by the following method: a gel system containing a template agent and an aluminum source is prepared; then mesoporous nano-alumina is removed.

[0008] Ma Huaixia et al. in the article “Thermodynamic analysis of isopropanol dehydration to prepare propylene” in Modern Chemical Industry, Vol. 40, No. 6, point out that from the perspective of thermodynamic equilibrium, the isopropanol dehydration reaction should adopt a high-temperature and normal-pressure gas-phase dehydration process. However, since the isopropanol dehydration reaction is still in the kinetic control stage and has not reached the thermodynamic equilibrium, the isopropanol dehydration reaction is not greatly guided.

[0009] Liu Chunyan et al. in the article “Reaction of isopropanol dehydration to prepare propylene catalyzed by acid catalyst” in Petroleum and Chemical Industry, Vol. 19, No. 5, point out that a higher isopropanol conversion rate can be achieved by simply increasing the reaction temperature, but the selectivity of propylene is reduced due to more side reactions, and the effect is not ideal. SUMMARY

[0010] The inventors of the present application believe that, in view of the strong demand for phenol in the current market and the overproduction of acetone in the acetone production process of the phenol-ketone device, the technical route of producing propylene by hydrogenation of acetone is an excellent adjustment product scheme. However, the existing technology has the problems of long process flow, high conversion rate and selectivity requirements for the catalyst, high energy consumption in the separation process, and high product purity requirements. In addition, the existing technology is a single process operation of acetone hydrogenation and isopropanol dehydration, and there is no integrated process for producing isopropanol by hydrogenation and dehydration of acetone. For the production of propylene from acetone, due to the high quality requirements of the polymerization grade propylene product (GB / T 7716-2014), there are the following problems: (1) The single-stage conversion rate and selectivity of acetone hydrogenation and isopropanol dehydration are relatively high, otherwise, the low conversion rate and selectivity of any one stage will make it difficult to meet the quality requirements of propylene; (2) In particular, for the process of isopropanol dehydration to produce propylene, the single-stage conversion rate and selectivity will directly affect the yield, product purity, and energy consumption of the refining and separation of propylene. Therefore, improving the conversion rate and selectivity of the process of isopropanol dehydration to produce propylene is very important for improving the purity of propylene product, reducing the consumption of isopropanol and acetone, and reducing the energy consumption of separation.

[0011] Therefore, the inventors of the present application believe that, in view of the overproduction of acetone caused by the excessive supply of acetone in the phenol-ketone device and the shortage of propylene resources, the lack of an overall method for producing propylene from acetone in the prior art, and the lack of a technology for integrating propylene production with a phenol device, the process of producing propylene by hydrogenation and dehydration of acetone is integrated with the phenol-ketone device, which not only solves the problem of low price and poor sales of acetone, but also provides a technical solution for adjusting the product ratio of the phenol-ketone device, thereby achieving significant economic benefits.

[0012] The inventors of the present application have found through diligent research that, in the isopropanol dehydration reaction, there is a reaction of isopropanol dehydration to produce propylene, and there is also a significant side reaction of propylene dimerization to produce heavy component impurities such as propylene dimers. In addition, due to the high temperature required for the dehydration reaction, in the case where the dehydration catalyst contains alumina, the propylene dimers can also crack to produce carbon two light components such as ethylene, or carbon three and carbon four heavy components such as methyl acetylene and butene. Therefore, for the process of isopropanol dehydration to produce propylene, if the dehydration catalyst contains alumina, the dimerized propylene and the cracked carbon two, carbon three, and carbon four components in the reaction product will directly affect the yield, product purity, and energy consumption of the refining and separation of propylene. Therefore, the impurities generated by the side reaction reduce the quality of the produced propylene, and further refining is required to produce propylene to meet the requirements of the national standard polymerization grade propylene.

[0013] The requirements of the superior product and the first-class product of the national standard GB / T 7716-2014 "Polymerization Grade Propylene" are shown in Table 1.

[0014] Table 1 Technical requirements of polymerization grade propylene

[0015]

[0016] As can be seen from Table 1, the first-class product of polymerization grade propylene requires propylene content ≥ 99.2 φ / %, and the superior product requires propylene content ≥ 99.6 φ / %. Since the propylene content of the superior product of the national standard is more than 99.6%, the carbon two ethylene content is required to be limited to less than 50 ppm in the first-class product of the national standard, the acetylene is less than 5 ppm, and the carbon three and carbon four unsaturated impurity content also needs to be less than 10 ppm. The superior product requires that the carbon two unsaturated impurity content be limited to less than 20 ppm, and the carbon three and carbon four unsaturated impurity content also needs to be less than 5 ppm.

[0017] The inventor of the present application also found that since the polymerization grade propylene product strictly limits the content of light components such as ethylene and acetylene, once light component impurities are generated in the dehydration reaction process, a light component separation tower with a length of nearly one hundred meters needs to be used to separate the light component impurities, which significantly increases the energy consumption and material consumption of the subsequent separation process. How to directly control the ethylene and acetylene and other light component impurities in the isopropyl alcohol dehydration reaction effluent within the content range required by the standard, reduce the energy consumption and material consumption of the subsequent separation and purification section, and even completely eliminate the light component separation tower, and obtain the polymerization grade propylene product at a lower cost, is one of the main problems to be solved by the present patent, and it is also one of the technical problems existing in the prior art.

[0018] The inventors of the present application have further found that, in the dehydration reaction of isopropyl alcohol, if the dehydration catalyst contains alumina, the dimerization of propylene and the cracking of the dimerization product can be inhibited by adding a small amount of water, thereby reducing the impurity components. Meanwhile, the inventors of the present application have also found that, in the dehydration reaction of isopropyl alcohol, the water content of the reaction raw material is closely related to the generation amount of specific impurities. Moreover, by using the correlation formula under the condition of a specific conversion rate, the generation amount of impurities can be controlled by adjusting the water content of the raw material, thereby achieving the purpose of reducing the difficult-to-separate impurities in the dehydration of isopropyl alcohol. In addition, by adjusting the water content of the raw material to further control the correlation method of reaction impurities, the problem of increasing side reactions caused by simply increasing the conversion rate of isopropyl alcohol by increasing the temperature can be avoided, and the current industrial operation can be guided, the reaction control means can be simplified, the side reactions in the dehydration of isopropyl alcohol can be effectively inhibited, and the subsequent separation difficulty of propylene product can be improved. Moreover, since water vapor can cause the removal of aluminum from the aluminum-containing catalyst, thereby damaging the stability of the catalyst, by controlling the amount of water added in the reaction in the present application, the adverse effects of the large water vapor atmosphere on the catalyst can also be avoided, and the overall energy consumption of the reaction can also be reduced.

[0019] The present application is completed based on the above findings.

[0020] Specifically, the present application relates to the following aspects.

[0021] 1. A dehydration method, comprising a step of causing a raw material containing isopropyl alcohol to undergo a dehydration reaction in the presence of a dehydration catalyst containing alumina to generate a product containing propylene (referred to as a dehydration step), and further comprising a step of measuring the content of carbon three carbon four unsaturated impurities in the product and comparing the measured value of the content (in ppm) with a preset value (such as 20 ppm, 10 ppm or 5 ppm, relative to the total mass of the product being 100 wt%), wherein when the measured value of the content is greater than the preset value, the conversion rate of isopropyl alcohol is measured, and the measured value of the conversion rate (denoted as C, in %) is obtained,

[0022] 1) when the measured value C is between 96.0% and 99.0%, increasing the water content of the raw material (preferably by 0.01-30 times, 0.01-20 times, 0.01-10 times, 0.01-5 times, 0.01-1 times, 0.01-0.5 times, 0.01-0.3 times, 0.01-0.2 times or 0.01-0.1 times), provided that the water content after the increase is in the range of 0.1-3.0 wt% (relative to the total mass of the raw material being 100 wt%), preferably, in a rectangular coordinate system with the conversion rate value of isopropyl alcohol (unit: %) as the abscissa (origin: 96.0, end: 99.0), the water content value of the raw material (unit: wt%) as the ordinate (origin: 0.1, end: 3.0) and the coordinate (0, 0) as the origin, drawing a straight line segment from the coordinate (96.0, 0.1) to the coordinate (99.0, 3.0), assuming that the coordinate of the measured value C on the straight line segment is (C, A1), wherein A1 represents the water content value on the straight line segment corresponding to the measured value C, then selecting a value in the range of A1 to 3.0 as the water content value after the increase, preferably selecting a value in the range of A1 to A1 + (3.0-A1) / 2 as the water content value after the increase,

[0023] 2) when the measured value C is between 99.0% and 99.5%, increasing the water content of the raw material (preferably by 0.01-2 times, 0.01-1 times, 0.01-0.5 times, 0.01-0.3 times, 0.01-0.2 times or 0.01-0.1 times), provided that the water content after the increase is in the range of 3.0-5.0 wt% (relative to the total mass of the raw material being 100 wt%), preferably, in a rectangular coordinate system with the conversion rate value of isopropyl alcohol (unit: %) as the abscissa (origin: 99.0, end: 99.5), the water content value of the raw material (unit: wt%) as the ordinate (origin: 3.0, end: 5.0) and the coordinate (0, 0) as the origin, drawing a straight line segment from the coordinate (99.0, 3.0) to the coordinate (99.5, 5.0), assuming that the coordinate of the measured value C on the straight line segment is (C, A2), wherein A2 represents the water content value on the straight line segment corresponding to the measured value C, then selecting a value in the range of A2 to 5.0 as the water content value after the increase, preferably selecting a value in the range of A2 to A2 + (5.0-A2) / 2 as the water content value after the increase,

[0024] 3) when the measured value C is between 99.5% and 99.9%, increasing the water content of the raw material (preferably by 0.01-2 times, 0.01-1 times, 0.01-0.5 times, 0.01-0.3 times, 0.01-0.2 times or 0.01-0.1 times), provided that the water content after the increase is in the range of 5.0-10.0 wt% (preferably 5.0-9.0 wt%, relative to the total mass of the raw material being 100 wt%), preferably, when a plane rectangular coordinate system is established with the conversion rate value of isopropyl alcohol (unit: %) as the abscissa (origin: 99.5, end: 99.9), with the water content value of the raw material (unit: wt%) as the ordinate (origin: 5.0, end: 10.0), and with the coordinate (0, 0) as the origin, a straight line segment is drawn from the coordinate (99.5, 5.0) to the coordinate (99.9, 10.0), and the coordinate of the measured value C on the straight line segment is denoted as (C, A3), wherein A3 represents the water content value on the straight line segment corresponding to the measured value C, then a value in the range of A3 to 10.0 (preferably A3 to 9.0) is selected as the value of the water content after the increase, and preferably a value in the range of A3 to A3 + (10.0-A3) / 2 (preferably A3 to A3 + (9.0-A3) / 2) is selected as the value of the water content after the increase.

[0025] 2. The dehydration method according to any one of the preceding or subsequent aspects, wherein the product has a carbon three carbon four unsaturated impurity content of 30 ppm or less (preferably 20 ppm or less, 10 ppm or less, or 5 ppm or less, relative to the total mass of the product being 100 wt%),

[0026] 3. The dehydration method according to any one of the preceding or subsequent aspects, wherein the raw material has a water content of 0.1-10.0 wt% (preferably 1.0-9.0 wt%, more preferably 3.0-5.0 wt%, relative to the total mass of the raw material being 100 wt%),

[0027] 4. The dehydration method according to any one of the preceding or subsequent aspects, wherein the product has a carbon two unsaturated impurity content of 50 ppm or less (preferably 30 ppm or less, 25 ppm or less, or 22 ppm or less, relative to the total mass of the product being 100 wt%), and / or, the product has a propylene content of 65.0-69.8 wt% (preferably 66.0-69.5 wt%, relative to the total mass of the product being 100 wt%).

[0028] 5. The dehydration process according to any of the preceding or following aspects, wherein the isopropanol content of the feedstock is 90.0-99.9 wt% (preferably 91.0-99.0 wt%, more preferably 92.0-97.0 wt%, relative to the total mass of the feedstock being 100 wt%), and / or, the conversion of isopropanol is 96.0-99.9% (preferably 97.0-99.8%, more preferably 98.5-99.5%).

[0029] 6. The dehydration process according to any of the preceding or following aspects, wherein the dehydration catalyst comprising alumina is selected from the group consisting of solid acid catalysts comprising alumina, preferably at least one of amorphous silica alumina and molecular sieve, more preferably amorphous silica alumina, in particular preferably amorphous silica alumina having an alumina mass content of 1-30 wt% (preferably 1-15 wt%), the balance being silicon dioxide, more in particular preferably the amorphous silica alumina having been treated with 300-500 °C saturated water vapor.

[0030] 7. The dehydration process according to any of the preceding or following aspects, wherein the operating conditions of the dehydration step comprise a reaction temperature of 150-450 °C (preferably 200-350 °C), a reaction pressure of 0.05-1.0 MPaG (preferably 0.1-0.5 MPaG), and a volume space velocity of 0.05-5.0 h -1 ( preferably 1-3 h -1 ).

[0031] 8. The dehydration process according to any of the preceding or following aspects, further comprising the step of separating an isopropanol / water mixture (preferably azeotrope) from the product,

[0032] or, further comprising the steps of:

[0033] 1) washing the product with an absorbent (preferably selected from at least one of water and isopropanol, in particular water), obtaining a crude propylene product and an enriched absorbent liquid,

[0034] 2) subjecting the crude propylene product to separation (preferably distillation) to remove (preferably only remove) heavy components, obtaining a purified propylene, and

[0035] 3) subjecting the enriched absorbent liquid to separation (preferably distillation), obtaining an isopropanol / water mixture (preferably azeotrope).

[0036] 0. The dehydration process according to any of the preceding or following aspects, wherein the water content of the mixture is 5-90 wt% (preferably 10-80 wt%, 10-50 wt% or 10-20 wt%, more preferably 12-13 wt%, relative to the total mass of the mixture being 100 wt%).

[0037] 10. The dehydration process according to any of the preceding or following aspects, further comprising the step of recycling at least a portion (preferably 50 wt% or more, 80 wt% or more, 90 wt% or more, or substantially 100 wt%) of the mixture to the dehydration step (referred to as a recycling step).

[0038] 11. The dehydration process according to any of the preceding or following aspects, wherein in the recycling step, the at least a portion of the mixture is mixed with the feedstock of the dehydration step, optionally supplemented with an additional amount of water, to adjust (such as increase or decrease) the water content of the feedstock to a predetermined value.

[0039] 12. A process for producing propylene, comprising the steps of:

[0040] hydrogenating acetone in the presence of a hydrogenation catalyst to produce a product comprising isopropanol,

[0041] separating the product comprising isopropanol to obtain a gas phase comprising hydrogen and a liquid phase comprising isopropanol,

[0042] separating the liquid phase comprising isopropanol to obtain isopropanol,

[0043] subjecting the isopropanol to a dehydration reaction according to the dehydration process of any of the preceding or following aspects to produce a product comprising propylene (referred to as a dehydration step),

[0044] washing the product comprising propylene with an absorbent to obtain a crude propylene product and an enriched absorbent liquid,

[0045] separating the enriched absorbent liquid to obtain an isopropanol / water azeotrope,

[0046] separating and removing heavies from the crude propylene product to obtain a refined propylene.

[0047] 13. The process for producing according to any of the preceding or following aspects, further comprising the step of:

[0048] recycling at least a portion (preferably 50 wt% or more, 80 wt% or more, 90 wt% or more, or substantially 100 wt%) of the isopropanol / water azeotrope to the dehydration step.

[0049] 14. A production apparatus for propylene, comprising, in series, an acetone hydrogenation reactor, a hydrogenation product gas-liquid separator, a fractionating column, an isopropanol dehydration reactor, a propylene absorption separation column, an azeotropic distillation column, and a crude propylene heavy component removal column, wherein the acetone hydrogenation reactor is configured to produce a product containing isopropanol by hydrogenating acetone in the presence of a hydrogenation catalyst, the hydrogenation product gas-liquid separator is configured to separate the product containing isopropanol to obtain a gas phase containing hydrogen and a liquid phase containing isopropanol, the fractionating column is configured to separate the liquid phase containing isopropanol to obtain isopropanol, the isopropanol dehydration reactor is configured to produce a product containing propylene by dehydrating the isopropanol in the presence of a dehydration catalyst comprising alumina, the propylene absorption separation column is configured to wash the product containing propylene with an absorbent to obtain a crude propylene product and an absorbent-rich liquid, the azeotropic distillation column is configured to separate the absorbent-rich liquid to obtain an isopropanol / water azeotrope, the crude propylene heavy component removal column is configured to remove heavy components from the crude propylene product to obtain refined propylene, and a material outlet at the top and / or upper portion of the azeotropic distillation column is connected to a raw material inlet of the isopropanol dehydration reactor.

[0050] 15. The production apparatus according to any one of the preceding or following aspects, wherein at least two measuring mechanisms, at least one comparison mechanism, and at least one control mechanism are provided at a product outlet of the isopropanol dehydration reactor, and in the at least two measuring mechanisms, at least one is configured to measure a carbon three carbon four unsaturated impurity content of the product to obtain a measured value of the content, and at least one is configured to measure a conversion rate of isopropanol to obtain a measured value of the conversion rate, the at least one comparison mechanism is configured to compare the measured values with the preset values, and based on the comparison result and the measured value of the conversion rate, to issue an instruction to the at least one control mechanism, and the at least one control mechanism is configured to execute the instruction to increase a water content of a raw material of the isopropanol dehydration reactor. BRIEF DESCRIPTION OF DRAWINGS

[0051] Figure 1 A process system for producing propylene from acetone is illustrated as an example to illustrate the present application. DETAILED DESCRIPTION

[0052] The following is a detailed description of specific embodiments of the application. However, it is to be understood that the scope of protection of the present application is not limited to these specific embodiments, but is determined by the claims appended hereto.

[0053] All publications, patent applications, patents, and other references mentioned in this specification are herein incorporated by reference. Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as is commonly understood by one of ordinary skill in the art. In case of conflict between the definitions in this specification and that of any document incorporated herein by reference, the definition in this specification prevails.

[0054] When the specification states a genus of elements with disclosure of examples, it is intended to convey that the genus can be limited to the disclosed examples or that the genus can encompass more than the disclosed examples.

[0055] Unless specifically indicated otherwise, all percentages, parts, ratios, etc. stated in this specification are based on weight and pressure is gauge pressure.

[0056] In the context of this specification, carbon diunsaturated impurities include ethylene and acetylene, carbon tri- and tetra-unsaturated impurities include methylacetylene, propadiene, butenes, butadiene, butyne, diacetylene, etc., and in particular methylacetylene, propadiene, butenes and butadiene.

[0057] In the context of this specification, the content of isopropanol (unreacted) in the product (in wt%) can be measured directly on-line on the gas at the reactor outlet using infrared spectroscopy, or can be measured by condensing the material at the outlet of the reactor, taking the liquid phase and measuring the content of isopropanol in the liquid phase (in wt%) using gas chromatography. In addition, the water content of the starting isopropanol can be measured by sampling the starting material at the inlet of the reactor and measuring the water content (in wt%) using gas chromatography or a moisture analyser.

[0058] In the context of this specification, the content of isopropanol in the product A (in wt%) is measured using infrared spectroscopy, and the water content of the starting material B (in wt%) is measured using a moisture analyser, and the conversion of isopropanol X is calculated according to the formula:

[0059] X = A / (1-B).

[0060] In the context of this specification, the content of isopropanol in the starting material C (in wt%) is measured using gas chromatography, the content of isopropanol in the condensed liquid D (in wt%) is measured using gas chromatography, the amount of starting material fed M (in g) is calculated from the pump flow rate and the sampling time, and the mass of condensed liquid N (in g) is measured by weighing, and the conversion of isopropanol X is calculated according to the formula:

[0061] X = (DN) / (CM).

[0062] In the context of the present specification, any two or more embodiments of the present application can be combined in an arbitrary manner, and the technical solutions thus formed are part of the original disclosure of the present specification and also fall within the protection scope of the present application.

[0063] The endpoints of the ranges and any values disclosed herein are not limited to the precise values stated. The ranges and values should be construed to be approximations that allow for significant variation. Each range endpoint is a separate point within the range, and each point within the range is incorporated into the disclosure as if expressly written in the disclosure. Any numerical values include increments of one unit plus or minus 0.0001, one unit plus or minus 0.001, one unit plus or minus 0.01, one unit plus or minus 0.1, one unit plus or minus 1, one unit plus or minus 2, one unit plus or minus 5, one unit plus or minus 10, and / or any other range endpoints less than or greater than zero, as these values are within manufacturing variability.

[0064] According to one embodiment of the present application, the dehydration method is a method for producing propylene by dehydration of isopropyl alcohol.

[0065] According to one embodiment of the present application, the dehydration method includes a step of dehydrating a raw material containing isopropyl alcohol in the presence of a dehydration catalyst containing alumina to produce a product containing propylene, referred to as a dehydration step. According to the present application, the intended technical effects of the present application are particularly remarkable in the case where the dehydration catalyst contains alumina.

[0066] According to one embodiment of the present application, the raw material has a water content of 0.1 to 10.0 wt%, preferably 1.0 to 9.0 wt%, and more preferably 3.0 to 5.0 wt%, relative to the total mass of the raw material being 100 wt%. According to the present application, when the water content is less than 0.1 wt%, the sum of the carbon di-unsaturated impurity content and the carbon tri- and tetra-unsaturated impurity content of the product exceeds the upper limit of the numerical value specified in the present application, and the intended technical effects of the present application such as a significant reduction in impurity content cannot be exhibited. In addition, when the water content is more than 10.0 wt%, not only the energy consumption of the dehydration method increases, but also the sum of the carbon di-unsaturated impurity content and the carbon tri- and tetra-unsaturated impurity content of the product exceeds the upper limit of the numerical value specified in the present application, and likewise the intended technical effects of the present application such as a significant reduction in impurity content cannot be exhibited.

[0067] According to one embodiment of the present application, the sum of the content of carbon di-unsaturated impurities and the content of carbon tri- and tetra-unsaturated impurities of the product is 80 ppm or less, preferably 75 ppm or less, 50 ppm or less, 40 ppm or less, 30 ppm or less or 27 ppm or less, with respect to the total mass of the product being 100 wt%. Preferably, the content of carbon di-unsaturated impurities of the product is 50 ppm or less, preferably 30 ppm or less, 25 ppm or less or 22 ppm or less, with respect to the total mass of the product being 100 wt%. Preferably, the content of carbon tri- and tetra-unsaturated impurities of the product is 30 ppm or less, preferably 20 ppm or less, 10 ppm or less or 5 ppm or less, with respect to the total mass of the product being 100 wt%.

[0068] According to one embodiment of the present application, the content of propylene of the product is 65.0 - 69.8 wt%, preferably 66.0 - 69.5 wt%, with respect to the total mass of the product being 100 wt%.

[0069] According to one embodiment of the present application, the content of isopropanol of the feedstock is 90.0 - 99.9 wt%, preferably 91.0 - 99.0 wt%, more preferably 92.0 - 97.0 wt%, with respect to the total mass of the feedstock being 100 wt%. In addition to isopropanol and water, the feedstock can also comprise other components, such as those remaining from the reaction of hydrogenation of acetone, such as acetone or methanol, among others.

[0070] According to one embodiment of the present application, the conversion of isopropanol is 96.0 - 99.9%, preferably 97.0 - 99.8%, more preferably 98.5 - 99.5%, from the point of view of the significant achievement of the technical effects contemplated by the present application.

[0071] According to one embodiment of the present application, the dehydration catalyst is any solid acid catalyst capable of dehydrating isopropanol known in the art, but must contain alumina. The technical effect contemplated by the present application is most significant when the dehydration catalyst contains alumina. The dehydration catalyst is preferably at least one selected from the group consisting of amorphous silica-alumina and molecular sieve, more preferably amorphous silica-alumina. Here, as the amorphous silica-alumina, particularly preferred is amorphous silica-alumina having an alumina mass content of 1 to 30 wt% (preferably 1 to 15 wt%) and the balance being silica. The amorphous silica-alumina can be a commercially available product or can be manufactured according to the prior art. More preferably, the above-mentioned amorphous silica-alumina is amorphous silica-alumina treated with saturated water vapor at 300 to 500°C. As a method of manufacturing the amorphous silica-alumina, for example, there can be mentioned treatment of commercially available amorphous silica-alumina pellets having an alumina mass content of 1 to 15 wt% with saturated water vapor at 300 to 500°C for 5 to 10 hours. The above-mentioned catalyst has good dehydration activity, selectivity and long-term stability under very mild conditions in the isopropanol dehydration process. In addition, as the dehydration catalyst, there can be mentioned the core-shell alumina catalyst mentioned in CN 102451674.

[0072] According to one embodiment of the present application, the reaction temperature of the dehydration step is 150 to 450°C, preferably 200 to 350°C.

[0073] According to one embodiment of the present application, the reaction pressure of the dehydration step is 0.05 to 1.0 MPaG, preferably 0.1 to 0.5 MPaG.

[0074] According to one embodiment of the present application, the volume space velocity of the dehydration step is 0.05 to 5.0 h -1 , preferably 1 to 3 h -1 .

[0075] According to one embodiment of the present application, the dehydration method further comprises a step of separating an isopropanol / water mixture from the product. Here, as the mixture, an azeotrope is preferred.

[0076] According to one embodiment of the present application, the dehydration method further comprises the following steps:

[0077] 1) washing the product with an absorbent to obtain a crude propylene product and an absorbent-rich solution. Here, the absorbent is a solvent capable of absorbing the water-soluble components in the isopropanol dehydration product, and is preferably water, isopropanol or a mixture of isopropanol and water in any ratio. The above-mentioned absorbent is lean absorbent before addition and becomes rich absorbent after absorption of the soluble components.

[0078] 2) the crude propylene product is separated to remove heavy components to obtain a refined propylene product. Here, as the separation, rectification is preferred. In addition, according to the present application, it is preferred that, due to the very low content of light components in the crude propylene product obtained by the isopropanol dehydration method of the present application, only the removal of heavy components from the crude propylene product by the separation is required to obtain a refined propylene product, particularly a refined propylene product meeting the requirements of the national standard for polymerization grade propylene. According to this preferred embodiment, the separation only includes the step of removing heavy components, and does not need to include the step of removing light components, which is generally required in the prior art. Here, the so-called heavy components generally refer to carbon four and above hydrocarbon substances, particularly the carbon four unsaturated impurities, and the so-called light components generally refer to carbon two and below hydrocarbon substances, particularly the carbon two unsaturated impurities.

[0079] 3) the rich absorbent is separated to obtain an isopropanol / water mixture. Here, as the separation, rectification, particularly azeotropic rectification, is preferred.

[0080] According to one embodiment of the present application, in the dehydration method, the water content of the mixture is 5-90 wt%, preferably 10-80 wt%, 10-50 wt% or 10-20 wt%, more preferably 12-13 wt%, relative to the total mass of the mixture being 100 wt%.

[0081] According to one embodiment of the present application, it further includes the step of recycling at least a portion of the mixture to the dehydration step (referred to as the recycling step). Here, as the at least a portion, preferably 50 wt% or more, 80 wt% or more, 90 wt% or more, or substantially 100 wt% (i.e. substantially all of the recycling). By recycling the mixture, particularly the azeotrope, to the dehydration step, the water content of the raw material can be flexibly adjusted, and the overall energy consumption of the dehydration method can be significantly reduced. For this purpose, it is preferred that, in the recycling step, the at least a portion of the mixture is mixed with the raw material of the dehydration step, and optionally an additional amount of water is supplemented, to adjust (such as increase or decrease) the water content of the raw material to a predetermined value. Here, the present application does not particularly limit the mixing method of the mixture with the raw material (and optionally the additional amount of water), as long as these materials are sufficiently mixed. From the perspective of adjusting the water content of the raw material, these materials are generally mixed before the raw material undergoes the dehydration reaction (such as before entering the dehydration reactor).

[0082] The inventors of the present application have found that the water content of the isopropyl alcohol feedstock during the reaction is closely related to the conversion rate of the isopropyl alcohol and the content of carbon three carbon four unsaturated impurities or carbon two unsaturated impurities in the product. Specifically, when the reaction conversion rate exceeds 96% by increasing the reaction temperature for example, the content of carbon three carbon four unsaturated impurities or carbon two unsaturated impurities in the reaction product will obviously increase with the increase of the reaction conversion rate. For this reason, the present application also relates to a control scheme for such impurities in the following embodiments.

[0083] According to one embodiment of the present application, the dehydration method further comprises a step of measuring the content of carbon three carbon four unsaturated impurities in the product. Here, the measurement method of the content is, for example, infrared spectroscopy analysis. Generally, the measurement is carried out at the outlet of the reaction product of the dehydration reactor. The measurement of the content can be carried out continuously, intermittently, on-line or off-line, and is not particularly limited.

[0084] According to this embodiment of the present application, by the content measurement, a measured value of the content (in ppm) is obtained. Then, the measured value of the content is compared with a preset value of the content. Here, as the preset value, it can be 20 ppm, 10 ppm or 5 ppm (relative to the total mass of the product being 100 wt%) for example. The preset value represents the highest allowable content of carbon three carbon four unsaturated impurities in the reaction product for those skilled in the art.

[0085] According to this embodiment of the present application, by the comparison, if the measured value of the content is greater than the preset value (triggering condition), the conversion rate of isopropyl alcohol is measured, and a measured value of the conversion rate (set as C, in %) is obtained. Generally, the measurement of the conversion rate is carried out at the outlet of the reaction product of the dehydration reactor. The measurement of the conversion rate can be carried out continuously, intermittently, on-line or off-line, and is not particularly limited. In addition, according to the present application, the measurement of the content and the measurement of the conversion rate can be carried out synchronously or in a certain order, and is not particularly limited, but from the perspective of efficiency, the measurement of the conversion rate is generally carried out when the triggering condition is met.

[0086] According to this embodiment of the present application, when the measured value C is between 96.0% and 99.0%, the water content of the raw material is increased, provided that the water content after the increase is within the range of 0.1 to 3.0 wt% (relative to the total mass of the raw material being 100 wt%). Here, as the increase range (increase amount), it is generally 0.01 to 30 times, 0.01 to 20 times, 0.01 to 10 times, 0.01 to 5 times, 0.01 to 1 times, 0.01 to 0.5 times, 0.01 to 0.3 times, 0.01 to 0.2 times, or 0.01 to 0.1 times. According to the present application, it is preferred that, when a rectangular coordinate system is established with the conversion rate value of isopropyl alcohol (unit: %) as the abscissa (origin: 96.0, end: 99.0) and the water content value of the raw material (unit: wt%) as the ordinate (origin: 0.1, end: 3.0) and with the coordinate (0, 0) as the origin, a straight line segment is drawn from the coordinate (96.0, 0.1) to the coordinate (99.0, 3.0), and the coordinate of the measured value C on the straight line segment is set as (C, Al), where Al represents the water content value on the straight line segment corresponding to the measured value C, then a value within the range of Al to 3.0 is selected as the water content value after the increase, and preferably a value within the range of Al to Al + (3.0 - Al) / 2 is selected as the water content value after the increase. As the water content value after the increase, Al or its vicinity is generally selected. According to the present application, when the conversion rate of isopropyl alcohol is changed by changing the reaction temperature (for example, by increasing the reaction temperature), for example, the content of carbon three carbon four unsaturated impurities in the reaction product can be controlled to be 10 ppm or less, preferably 5 ppm or less, by this control scheme.

[0087] According to this embodiment of the present application, when the measured value C is between 99.0% and 99.5%, the water content of the raw material is increased, provided that the water content after the increase is within the range of 3.0 to 5.0 wt% (relative to the total mass of the raw material being 100 wt%). Here, as the increase range (increase amount), it is generally 0.01 to 2 times, 0.01 to 1 times, 0.01 to 0.5 times, 0.01 to 0.3 times, 0.01 to 0.2 times, or 0.01 to 0.1 times. According to the present application, it is preferable that, when a plane rectangular coordinate system is established with the conversion rate value of isopropyl alcohol (unit: %) as the abscissa (origin: 99.0, end: 99.5) and the water content value of the raw material (unit: wt%) as the ordinate (origin: 3.0, end: 5.0) and with the coordinate (0, 0) as the origin, a straight line segment is drawn from the coordinate (99.0, 3.0) to the coordinate (99.5, 5.0), and the coordinate of the measured value C on the straight line segment is set as (C, A2), where A2 represents the water content value on the straight line segment corresponding to the measured value C, then a value within the range of A2 to 5.0 is selected as the water content value after the increase, and preferably a value within the range of A2 to A2 + (5.0 - A2) / 2 is selected as the water content value after the increase. As the water content value after the increase, A2 or its vicinity is generally selected. According to the present application, when the conversion rate of isopropyl alcohol is changed by changing the reaction temperature (for example, by increasing the reaction temperature), for example, the content of carbon three carbon four unsaturated impurities in the reaction product can be controlled to be 10 ppm or less, preferably 5 ppm or less, by this control scheme.

[0088] According to this embodiment of the present application, when the measured value C is between 99.5% and 99.9%, the water content of the raw material is increased, provided that the water content after the increase is in the range of 5.0-10.0 wt% (preferably 5.0-9.0 wt%, based on the total mass of the raw material being 100 wt%). Here, as the increase range (increase amount), it is generally 0.01-2 times, 0.01-1 times, 0.01-0.5 times, 0.01-0.3 times, 0.01-0.2 times, or 0.01-0.1 times. According to the present application, it is preferable that, when a rectangular coordinate system is established with the conversion rate value of isopropyl alcohol (unit: %) as the abscissa (origin: 99.5, end: 99.9) and the water content value of the raw material (unit: wt%) as the ordinate (origin: 5.0, end: 10.0) and with the coordinate (0, 0) as the origin, a straight line segment is drawn from the coordinate (99.5, 5.0) to the coordinate (99.9, 10.0), and the coordinate of the measured value C on the straight line segment is set as (C, A3), where A3 represents the water content value on the straight line segment corresponding to the measured value C, then a value in the range of A3 to 10.0 (preferably A3 to 9.0) is selected as the water content value after the increase, and preferably a value in the range of A3 to A3 + (10.0 - A3) / 2 (preferably A3 to A3 + (9.0 - A3) / 2) is selected as the water content value after the increase. As the water content value after the increase, A3 or a value near A3 is generally selected. According to the present application, when the conversion rate of isopropyl alcohol is changed by changing the reaction temperature (for example, by increasing the reaction temperature), for example, the content of carbon three carbon four unsaturated impurities in the reaction product can be controlled to be 10 ppm or less, preferably 5 ppm or less, by this control scheme.

[0089] According to one embodiment of the present application, there is also provided a method for producing propylene, comprising the steps of:

[0090] hydrogenating acetone in the presence of a hydrogenation catalyst to produce a product containing isopropyl alcohol,

[0091] separating the product containing isopropyl alcohol to obtain a gas phase containing hydrogen and a liquid phase containing isopropyl alcohol,

[0092] separating the liquid phase containing isopropyl alcohol to obtain isopropyl alcohol,

[0093] subjecting the isopropyl alcohol to a dehydration reaction according to any one of the dehydration methods described above to produce a product containing propylene (referred to as a dehydration step),

[0094] washing the product containing propylene with an absorbent to obtain a crude propylene product and an absorbent-rich liquid,

[0095] separating the absorbent-rich liquid to obtain an isopropyl alcohol / water azeotrope,

[0096] removing heavy components from the crude propylene product to obtain refined propylene.

[0097] According to one embodiment of the present application, the hydrogenation of acetone can be carried out in any manner known in the art. For example, the hydrogenation of acetone can be carried out in the presence of a hydrogenation catalyst, and any catalyst capable of hydrogenating acetone to isopropanol can be used, but from the aspects of production cost, applicability, etc., a nickel-based or copper-based catalyst is generally used, the nickel content in the nickel-based catalyst is generally 5-45 wt%, and other active components or auxiliary components can also be contained, the copper content in the copper-based catalyst is generally 8-45 wt%, and other active components or auxiliary components can also be contained. As a further preference, a copper-based catalyst having good hydrogenation activity and selectivity under very mild conditions in the process of hydrogenating acetone to isopropanol is used, and the energy consumption and material consumption of the entire device are low. In addition, generally, the reaction temperature of the hydrogenation process of acetone is 100-200°C, the reaction pressure is 0.5-6.0 MPaG, the volume space velocity of the catalyst is 0.05-15 h -1 , and the molar ratio of hydrogen to acetone is 2:1-15:1.

[0098] According to the present application, the isopropanol-containing product is separated to obtain a gas phase containing hydrogen and a liquid phase containing isopropanol. Here, the gas phase can be recycled, and the liquid phase contains a small amount of unreacted acetone and heavy component by-products, and after removal by a fractionating column, refined isopropanol is obtained. According to the present application, the separation and removal, etc. are not limited in any way, and knowledge known in the art can be directly applied.

[0099] According to one embodiment of the present application, the manufacturing method further comprises the step of recycling at least a portion of the isopropanol / water azeotrope to the dehydration step. Here, as the at least a portion, 50 wt% or more, 80 wt% or more, 90 wt% or more, or substantially 100 wt% (i.e., substantially all of the recycling) is preferred.

[0100] According to one embodiment of the present application, a propylene production device is also involved, which comprises, in sequence, a hydrogenation reactor for acetone, a gas-liquid separator for hydrogenation product, a fractionating column, an isopropanol dehydration reactor, a propylene absorption separation column, an azeotropic rectification column, and a heavy component removal column for crude propylene. Here, the propylene production device is a device specifically used to implement the manufacturing method of propylene described in the foregoing of the present application.

[0101] According to one embodiment of the present application, in the propylene production apparatus, the acetone hydrogenation reactor is configured to produce a product containing isopropyl alcohol by hydrogenating acetone in the presence of a hydrogenation catalyst, the hydrogenation product gas-liquid separator is configured to separate the product containing isopropyl alcohol to obtain a gas phase containing hydrogen and a liquid phase containing isopropyl alcohol, the fractionating column is configured to separate the liquid phase containing isopropyl alcohol to obtain isopropyl alcohol, the isopropyl alcohol dehydration reactor is configured to produce a product containing propylene by dehydrating isopropyl alcohol in the presence of a dehydration catalyst containing alumina, the propylene absorption separation column is configured to wash the product containing propylene with an absorbent to obtain a crude propylene product and an absorbent-rich liquid, the azeotropic rectifying column is configured to separate the absorbent-rich liquid to obtain isopropyl alcohol / water azeotrope, and the crude propylene heavy component removal column is configured to separate and remove heavy components from the crude propylene product to obtain refined propylene. According to the present application, in order to obtain refined propylene, a light component removal column does not need to be provided.

[0102] According to one embodiment of the present application, in the propylene production apparatus, a material outlet at the top and / or upper portion of the azeotropic rectifying column is communicated with a raw material inlet of the isopropyl alcohol dehydration reactor. Through this specific communication structure, at least a part of the isopropyl alcohol / water azeotrope can be recycled to the dehydration step.

[0103] According to one embodiment of the present application, in the propylene production apparatus, a column bottom liquid outlet of the azeotropic rectifying column is communicated with an absorbent inlet of the propylene absorption separation column.

[0104] According to one embodiment of the present application, the acetone hydrogenation reactor is a fixed bed reactor, preferably a fixed bed reactor with tubes, in which the catalyst is loaded in the tubes and the heat removal medium is introduced outside the tubes, because the acetone hydrogenation reaction is exothermic.

[0105] According to one embodiment of the present application, the isopropyl alcohol dehydration reactor is a fixed bed reactor, preferably a fixed bed reactor with tubes, in which the catalyst is loaded in the tubes and the heat supply medium is introduced outside the tubes, because the isopropyl alcohol dehydration reaction is endothermic.

[0106] According to one embodiment of the present application, in the propylene production device, at least two measuring mechanisms, at least one comparing mechanism and at least one controlling mechanism are provided at the product outlet of the isopropanol dehydration reactor. According to this embodiment of the present application, in the at least two measuring mechanisms, at least one is configured to measure the content of carbon three, carbon four and / or carbon two unsaturated impurities in the product to obtain a measured value of the content, and at least one is configured to measure the conversion rate of isopropanol to obtain a measured value of the conversion rate (such as the aforementioned measured value C or measured value D). In addition, the at least one comparing mechanism is configured to compare the measured value of the content with a preset value, and based on the comparison result (such as the measured value of the content is greater than the preset value) and the measured value of the conversion rate, an instruction is issued to the controlling mechanism, which is preferably used to implement the aforementioned impurity control scheme, and the instruction is generally to increase the water content of the raw material of the isopropanol dehydration reactor according to the impurity control scheme. Moreover, the controlling mechanism is configured to execute the instruction to actually increase the water content of the raw material of the isopropanol dehydration reactor. For example, the controlling structure can be provided on the azeotrope circulating pipeline to increase the circulating proportion of the azeotrope, or on the water supplement pipeline to increase the amount of water supplement to the raw material.

[0107] Without being limited by any theory, the inventors of the present application believe that in the isopropanol dehydration reaction, when the dehydration catalyst contains alumina, due to the existence of B acid sites on the dehydration catalyst, the dimerization of propylene to form 4-methyl-1-pentene and other propylene dimers, and the cracking of dimers to form carbon two and carbon four olefin and alkyne components are promoted. The present application ensures the reaction efficiency while competing with the two side reactions of propylene dimerization and dimer product cracking by including a small amount of water (such as 0.1 wt% or more) in the raw material as a reaction competitor of B acid site nucleophilicity, thereby inhibiting the occurrence of side reactions. However, when the water content is too high (such as higher than 10.0 wt%), the B acid sites will increase due to the hydrolysis of the dehydration catalyst and other reasons, which will aggravate the side reactions. In addition, the present application proposes the correlation between the water content and the heavy components and light components after the reaction, which facilitates predictable operation during the reaction, avoids the influence of blind operation on the generation of impurities, and at the same time realizes the effective inhibition of the impurity content of isopropanol under high conversion rate conditions. Examples

[0108] The present application will be further described in detail by examples and comparative examples, but the present application is not limited to the following examples.

[0109] Example 1

[0110] This embodiment provides a process system for producing propylene from acetone:

[0111] As shown in Figure 1 the process system includes acetone raw material storage tank, acetone hydrogenation reactor, gas-liquid separator, fractionating column, isopropyl alcohol storage tank, isopropyl alcohol dehydration reactor, absorption separation column, compressor and crude propylene refining column connected in sequence, wherein the overhead outlet of the absorption separation column is connected to the compressor, and the bottom outlet is further connected to an azeotropic distillation column, the azeotrope outlet of the azeotropic distillation column is connected to the inlet of the isopropyl alcohol dehydration reactor, and the bottom product outlet of the azeotropic distillation column is further connected to the inlet of the absorption separation column and added into the absorption separation column together with the absorbent entering the absorption separation column; the gas outlet of the gas-liquid separator is connected to the compressor and finally connected to the acetone hydrogenation reactor, and the hydrogen obtained by gas-liquid separation is used as the supplementary hydrogen for acetone hydrogenation; the overhead light component product outlet of the fractionating column is connected to the acetone raw material storage tank, and the unreacted acetone is recycled.

[0112] The acetone hydrogenation reactor is a tube reactor, and the tube is filled with acetone hydrogenation catalyst, and the outside of the tube is connected to a heat removal medium to remove the reaction heat. The isopropyl alcohol dehydration reactor is a tube reactor, and the tube is filled with isopropyl alcohol dehydration catalyst, and the outside of the tube is connected to a heat supply medium to provide heat.

[0113] The method for preparing propylene from acetone by using the above process system includes an acetone hydrogenation reaction section and an isopropyl alcohol dehydration reaction section.

[0114] The acetone hydrogenation reaction section: the acetone raw material enters the acetone raw material storage tank, is pressurized, mixed with recycled hydrogen, and heated, and then enters the acetone hydrogenation reactor to undergo hydrogenation reaction under the action of the acetone hydrogenation catalyst to obtain a reaction effluent containing isopropyl alcohol. The reaction effluent is cooled by condensation and then enters the gas-liquid separator, the separated gas phase is pressurized by the compressor and recycled, and the separated liquid phase enters the fractionating column. The fractionating column fractionates the mixture containing isopropyl alcohol to remove a small amount of light components and heavy components to obtain refined isopropyl alcohol, wherein the removed light components are generally unreacted acetone and are recycled to the raw material tank, and the removed heavy components are generally acetone hydrogenation by-products and can be continuously or intermittently discharged.

[0115] The refined isopropyl alcohol obtained from the acetone hydrogenation reaction section is used as raw material to enter an isopropyl alcohol storage tank, mixed with the azeotrope obtained from the azeotrope rectification tower and / or additional water, and then enters an isopropyl alcohol dehydration reactor to undergo isopropyl alcohol dehydration reaction under the action of a dehydration catalyst, to obtain a reaction effluent containing propylene, which enters the bottom of an absorption separation tower, an absorbent is introduced into the top of the tower, and after heat exchange and absorption mass transfer exchange in the tower, the crude propylene discharged from the top is pressurized by a compressor, and the rich absorbent discharged from the bottom enters the azeotrope rectification tower. The crude propylene pressurized by the compressor enters a crude propylene rectification tower, and refined propylene and a small amount of heavy components are separated, wherein the heavy components are generally polymers of propylene, and the small amount of heavy components are intermittently discharged. The rich absorbent entering the azeotrope rectification tower is subjected to azeotrope rectification in the tower, and the azeotrope is obtained at the top of the tower, and the bottom product is returned to the absorption separation tower as an absorbent for recycling.

[0116] The acetone raw material in the following examples and comparative examples is from a certain factory, and the specifications are shown in Table 1.

[0117] Table 1.

[0118]

[0119] The specific implementation of using the above system and method to produce propylene from acetone is as follows:

[0120] The above acetone raw material is used to produce propylene:

[0121] The size of the tube of the acetone hydrogenation reactor is φ20×2.0, and the length is 1.5 meters. The outer tube of the reaction tube is connected to a heat removal medium water, which is heated by the vaporization of water to generate 0.3 MPa steam. The acetone hydrogenation reaction conditions are as follows: the temperature is 170°C, the pressure is 3.5 MPa, the catalyst space velocity is 1.5 h -1 , and the volume ratio of hydrogen to acetone is 10:1. The acetone hydrogenation catalyst is a copper-based catalyst developed by Sinopec Dalian Petrochemical Research Institute, and the catalyst has a cylindrical shape.

[0122] The isopropyl alcohol raw material is mixed with the azeotrope rectification product at the top of the azeotrope tower and water to undergo dehydration reaction

[0123] The size of the tube of the isopropyl alcohol dehydration reactor is φ10×2.0, and the isopropyl alcohol dehydration reaction conditions are as follows: the temperature is 280°C, the pressure is 0.3 MPa, the catalyst space velocity is 1.5 h -1 , and the isopropyl alcohol dehydration catalyst is a self-made alumina type catalyst: amorphous silicon-aluminum beads with an alumina mass content of 10% are treated in a saturated water vapor atmosphere at 450°C for 10 hours to obtain the isopropyl alcohol dehydration catalyst. The catalyst has a spherical shape.

[0124] In the isopropanol dehydration reaction section, the water content of the isopropanol raw material was 8 wt%, the isopropanol content in the product was 3.2 wt%, the content of carbon two unsaturated impurities in the reaction effluent was 9 ppm, the content of carbon three and carbon four unsaturated impurities was 3 ppm, and the conversion rate of isopropanol was 96.8%.

[0125] The properties of the final propylene product, the selectivity of the isopropanol dehydration catalyst, the composition of the unsaturated hydrocarbon impurities in the product, and the energy consumption (the energy consumption refers to the energy consumption per ton of product in the entire process when the isopropanol dehydration method produces qualified propylene product) are shown in Table 2.

[0126] Example 2

[0127] Isopropanol was prepared using the raw materials and method of Example 1, and isopropanol directly mixed with water was used as the raw material for the dehydration reaction

[0128] The column size of the isopropanol dehydration reactor was φ10x2.0, and the isopropanol dehydration reaction conditions were as follows: temperature was 280°C, pressure was 0.3 MPa, catalyst space velocity was 1.5h -1 , the water content of the isopropanol raw material was 1%, and the isopropanol dehydration catalyst was a self-made alumina type catalyst: amorphous silicon aluminum beads with an alumina mass content of 10% were treated in a saturated water vapor atmosphere at 450°C for 10 hours to obtain the isopropanol dehydration catalyst. The catalyst was in the shape of a sphere.

[0129] As the device was running, the reaction conversion rate was maintained or increased by increasing the reaction temperature, the reaction efficiency was improved, and the reaction temperature was increased to 290°C. At this time, it was detected that the content of methyl acetylene, propadiene in the reaction gas phase product was 6 ppm, the content of butene and butadiene was 7 ppm, the isopropanol content in the product was 2.5 wt%, and the conversion rate was 97.5%. According to the water adjustment formula of the recombination material proposed in the present patent, after adjusting the water content of isopropanol in the raw material to 1.5%, it was detected that under the reaction conditions, the content of carbon two unsaturated impurities in the reaction effluent was 15 ppm, the content of methyl acetylene, propadiene was 5 ppm, and the content of butene and butadiene was 4 ppm.

[0130] The properties of the final propylene product, the selectivity of the isopropanol dehydration catalyst, the composition of the unsaturated hydrocarbon impurities in the product, and the energy consumption (the energy consumption refers to the energy consumption per ton of product in the entire process when the isopropanol dehydration method produces qualified propylene product) are shown in Table 2.

[0131] Example 3

[0132] Isopropanol was prepared using the raw materials and method of Example 1, and isopropanol directly mixed with water was used as the raw material for the dehydration reaction

[0133] The column tube size of the isopropanol dehydration reactor is φ10x2.0, and the isopropanol dehydration reaction conditions are as follows: the temperature is 280 ℃, the water content of the raw material isopropanol is 3.5%, the pressure is 0.3 MPa, and the catalyst space velocity is 1.5h -1 The isopropanol dehydration catalyst is a self-made alumina type catalyst: the amorphous silicon-aluminum beads with an alumina mass content of 10% are treated in a saturated water vapor atmosphere at 450 ℃ for 10 hours to obtain the isopropanol dehydration catalyst. The catalyst shape is spherical.

[0134] With the operation of the device, the reaction conversion rate is maintained or increased by increasing the reaction temperature, the reaction efficiency is improved, and the reaction temperature is increased to 301 ℃. At this time, the methylacetylene, propadiene content in the reaction gas phase product is 7 ppm, the butene and butadiene content is 8 ppm, the isopropanol content in the product is 0.7 wt%, and the conversion rate is 99.3%. According to the recombination water adjustment formula proposed in the patent, the water content of isopropanol in the raw material is adjusted to 4.2% after the reaction conditions are detected. The carbon two unsaturated impurity content of the reaction effluent under the reaction conditions is 16 ppm, the methylacetylene, propadiene content is 4 ppm, and the butene and butadiene content is 5 ppm.

[0135] The properties of the finally obtained propylene product, the selectivity of the isopropanol dehydration catalyst, the composition of the unsaturated hydrocarbon impurities in the product, and the energy consumption (the energy consumption refers to the energy consumption per ton of product in the entire process when the isopropanol dehydration method is used to prepare qualified propylene product) are shown in Table 2.

[0136] Example 4

[0137] The isopropanol is prepared by using the raw material and method of Example 1, and the isopropanol is directly mixed with water and then used as a raw material for dehydration reaction

[0138] The column tube size of the isopropanol dehydration reactor is φ10x2.0, and the isopropanol dehydration reaction conditions are as follows: the temperature is 280 ℃, the water content of the raw material isopropanol is 7.0%, the pressure is 0.2 MPa, and the catalyst space velocity is 1.5h -1 The isopropanol dehydration catalyst is a self-made alumina type catalyst: the amorphous silicon-aluminum beads with an alumina mass content of 10% are treated in a saturated water vapor atmosphere at 450 ℃ for 10 hours to obtain the isopropanol dehydration catalyst. The catalyst shape is spherical.

[0139] As the device operates, the reaction conversion rate is maintained or increased by increasing the reaction temperature, improving the reaction efficiency, and the reaction temperature is increased to 308°C. At this time, the methylacetylene content in the reaction gas phase product is detected to be 7 ppm, the propadiene content is 6 ppm, the isopropyl alcohol content in the product is 0.3 wt%, and the conversion rate is 99.7%. According to the recombination water adjustment formula proposed in the patent, the isopropyl alcohol water content in the raw material is adjusted to 8.7% after the reaction under the above conditions. The carbon two unsaturated impurity content in the reaction effluent is 21 ppm, the methylacetylene and propadiene content is 3 ppm, and the butene and butadiene content is 5 ppm.

[0140] The properties of the final propylene product, the selectivity of the isopropyl alcohol dehydration catalyst, the composition of the unsaturated hydrocarbon impurities in the product, and the energy consumption (the energy consumption refers to the energy consumption per ton of product in the entire process when the isopropyl alcohol dehydration method produces qualified propylene product) are shown in Table 2.

[0141] Comparative Example 1:

[0142] Pure isopropyl alcohol was used as the raw material to enter the reactor for dehydration reaction, and the column tube size of the isopropyl alcohol dehydration reactor was φ10x2.0.

[0143] The isopropyl alcohol dehydration reaction conditions were as follows: the temperature was 280°C, the pressure was 0.3 MPa, and the catalyst space velocity was 1.5h -1 The isopropyl alcohol dehydration catalyst was a self-made alumina type catalyst: amorphous silicon aluminum beads with an alumina mass content of 10% were treated in a saturated water vapor atmosphere at 450°C for 10 hours to obtain the isopropyl alcohol dehydration catalyst. The catalyst was spherical in shape, and the product was analyzed by gas chromatography.

[0144] Here, the water content of the isopropyl alcohol raw material was 0 wt%, and the isopropyl alcohol content in the product was 0.9 wt%.

[0145] The properties of the final propylene product, the isopropyl alcohol conversion rate, the composition of the alkyne impurities in the product, and the energy consumption (the energy consumption refers to the energy consumption per ton of product in the entire process when the isopropyl alcohol dehydration method produces qualified propylene product) are shown in Table 2.

[0146] Comparative Example 2:

[0147] Pure isopropyl alcohol was used as the raw material to enter the reactor for dehydration reaction, and the column tube size of the isopropyl alcohol dehydration reactor was φ10x2.0.

[0148] The isopropyl alcohol dehydration reaction conditions were as follows: the temperature was 300°C, the pressure was 0.3 MPa, and the catalyst space velocity was 1.5h -1, isopropanol dehydration catalyst using self-made alumina type catalyst: the alumina content of 10% amorphous silicon aluminum beads, in the saturated water vapor atmosphere at 450 ℃ for 10 hours to obtain the isopropanol dehydration catalyst. Catalyst shape is spherical, the product is analyzed by gas chromatography.

[0149] Here, the water content of isopropanol raw material is 0wt%, the isopropanol content in the product is 0.3wt%.

[0150] The final propylene product properties, isopropanol conversion rate, product alkyne impurity composition and energy consumption (energy consumption refers to the energy consumption of the whole process when the isopropanol dehydration method is used to prepare qualified propylene product) are shown in table 2.

[0151] Comparative example 3:

[0152] Pure isopropanol is used as raw material into the reactor for dehydration reaction, isopropanol dehydration reactor column size is φ10×2.0.

[0153] Isopropanol dehydration reaction conditions are as follows: temperature is 330 ℃, pressure is 0.3 MPa, catalyst space velocity is 1.5h -1 , isopropanol dehydration catalyst using self-made alumina type catalyst: the alumina content of 10% amorphous silicon aluminum beads, in the saturated water vapor atmosphere at 450 ℃ for 10 hours to obtain the isopropanol dehydration catalyst. Catalyst shape is spherical, the product is analyzed by gas chromatography.

[0154] Here, the water content of isopropanol raw material is 16wt%, the isopropanol content in the product is 0.5wt%.

[0155] The final propylene product properties, isopropanol conversion rate, product alkyne impurity composition and energy consumption (energy consumption refers to the energy consumption of the whole process when the isopropanol dehydration method is used to prepare qualified propylene product) are shown in table 2.

[0156] Comparative example 4:

[0157] Pure isopropanol is used as raw material into the reactor for dehydration reaction, isopropanol dehydration reactor column size is φ10×2.0.

[0158] Isopropanol dehydration reaction conditions are as follows: temperature is 300 ℃, pressure is 0.3 MPa, catalyst space velocity is 1.5h -1 , isopropanol dehydration catalyst using heteropoly acid type catalyst. The product is analyzed by gas chromatography.

[0159] Here, the water content of isopropanol raw material is 3.0wt%, the isopropanol content in the product is 0.2wt%.

[0160] The properties of the final propylene product, the conversion of isopropanol, the composition of the ene-yne impurities in the product, and the energy consumption (energy consumption refers to the energy consumption per ton of product in the entire process when isopropanol is dehydrated to prepare a qualified propylene product) are shown in Table 2.

[0161] Table 2: Conversion of isopropanol, product composition, and energy consumption

[0162]

Claims

1. A method for the dehydration of isopropyl alcohol, characterized in that, The method comprises the steps of: dehydrating a raw material containing isopropyl alcohol in the presence of a dehydrating catalyst containing alumina to produce a product containing propylene, the dehydrating catalyst containing alumina being amorphous silicon-aluminum with an alumina mass content of 1-30 wt%, the balance being silicon dioxide, the amorphous silicon-aluminum being treated with 300-500°C saturated water vapor, and measuring the content of carbon three carbon four unsaturated impurities in the product and comparing the measured value with a preset value, the impurity content being 100 wt% based on the total mass of the product, wherein when the measured value is greater than the preset value, the conversion rate of isopropyl alcohol is measured, and the measured value of the conversion rate is set as C, the unit being %, 1) when the measured value C is between 96.0%-99.0%, the water content of the raw material is increased by 0.01-30 times, provided that the water content after the increase is within the range of 0.1-3.0 wt% based on the total mass of the raw material being 100 wt%; 2) when the measured value C is between 99.0%-99.5%, the water content of the raw material is increased by 0.01-2 times, provided that the water content after the increase is within the range of 3.0-5.0 wt% based on the total mass of the raw material being 100 wt%; 3) when the measured value C is between 99.5%-99.9%, the water content of the raw material is increased by 0.01-2 times, provided that the water content after the increase is within the range of 5.0-10.0 wt% based on the total mass of the raw material being 100 wt%.

2. The dewatering method of claim 1, wherein 1) in the first case, a straight line segment is drawn from the coordinate (96.0, 0.1) to the coordinate (99.0, 3.0) in a plane rectangular coordinate system established with the conversion rate of isopropyl alcohol as the horizontal coordinate, the starting point being 96.0% and the ending point being 99.0%, and the water content of the raw material as the vertical coordinate, the starting point being 0.1 wt% and the ending point being 3.0 wt%, with the coordinate (0, 0) as the origin, and the coordinate of the measured value C on the straight line segment is set as (C, A1), wherein A1 represents the water content value corresponding to the measured value C on the straight line segment, and a value within the range of A1 to 3.0 is selected as the value of the water content after the increase; 2) in the second case, a straight line segment is drawn from the coordinate (99.0, 3.0) to the coordinate (99.5, 5.0) in a plane rectangular coordinate system established with the conversion rate of isopropyl alcohol as the horizontal coordinate, the starting point being 99.0% and the ending point being 99.5%, and the water content of the raw material as the vertical coordinate, the starting point being 3.0 wt% and the ending point being 5.0 wt%, with the coordinate (0, 0) as the origin, and the coordinate of the measured value C on the straight line segment is set as (C, A2), wherein A2 represents the water content value corresponding to the measured value C on the straight line segment, and a value within the range of A2 to 5.0 is selected as the value of the water content after the increase; 3) in the 3), a straight line segment is drawn from the coordinate (99.5, 5.0) to the coordinate (99.9, 10.0) when a rectangular coordinate system is established with the conversion rate value of isopropyl alcohol as the abscissa, the starting point being 99.5% and the ending point being 99.9%, the water content value of the raw material as the ordinate, the starting point being 5.0wt% and the ending point being 10.0wt%, and the origin being the coordinate (0, 0), and the coordinate of the measured value C on the straight line segment is (C, A3), wherein A3 represents the water content value on the straight line segment corresponding to the measured value C, then a value in the range of A3 to 10.0 is selected as the value of the water content after the increase.

3. The dewatering method of claim 2, wherein, 1) in the 1), a value in the range of A1 to A1 + (3.0 - A1) / 2 is selected as the value of the water content after the increase; 2) in the 2), a value in the range of A2 to A2 + (5.0 - A2) / 2 is selected as the value of the water content after the increase; 3) in the 3), a value in the range of A3 to A3 + (10.0 - A3) / 2 is selected as the value of the water content after the increase.

4. The dewatering method of claim 3, wherein, 3) in the 3), a value in the range of A3 to A3 + (9.0 - A3) / 2 is selected as the value of the water content after the increase.

5. The dewatering method of claim 1, wherein, The water content of the raw material is 1.0-9.0wt%, based on the total mass of the raw material being 100wt%.

6. The dewatering method of claim 1, wherein, The content of carbon three and carbon four unsaturated impurities in the product is 30ppm or less, based on the total mass of the product being 100wt%.

7. The dewatering method of claim 6, wherein, The content of carbon three and carbon four unsaturated impurities in the product is 20ppm or less, based on the total mass of the product being 100wt%.

8. The dewatering method of claim 6, wherein, The content of carbon three and carbon four unsaturated impurities in the product is 10ppm or less, based on the total mass of the product being 100wt%.

9. The dewatering method of claim 1, wherein, The content of carbon two unsaturated impurities in the product is 50ppm or less, and / or the content of propylene in the product is 65.0-69.8wt%, based on the total mass of the product being 100wt%.

10. The dehydration method according to claim 1, wherein the content of isopropyl alcohol in the raw material is 90.0-99.9wt%, based on the total mass of the raw material being 100wt%, and / or the conversion rate of isopropyl alcohol is 96.0-99.9%.

11. The dehydration method according to claim 1, wherein the dehydration catalyst comprising alumina is amorphous silica alumina with an alumina mass content of 1-15wt% and the balance being silica.

12. The dewatering method of claim 1, wherein the operating conditions of the dewatering step include: The reaction temperature is 150-450°C, the reaction pressure is 0.05-1.0 MPaG, the volume space velocity is 0.05-5.0 h -1 .

13. The dewatering method of claim 12, wherein the operating conditions of the dewatering step include: The reaction temperature is 200-350°C, the reaction pressure is 0.1-0.5 MPaG, the volume space velocity is 1-3h -1 .

14. The dehydration method according to claim 1, further comprising a step of separating an isopropyl alcohol / water mixture from the product, or, further comprising the following steps: 1) washing the product with an absorbent to obtain a crude propylene product and an enriched absorbent liquid, 2) subjecting the crude propylene product to separation to remove heavy components to obtain a refined propylene, and 3) subjecting the enriched absorbent liquid to separation to obtain an isopropyl alcohol / water mixture.

15. The dehydration method according to claim 14, wherein the water content of the mixture is 5-90wt%, based on the total mass of the mixture being 100wt%.

16. The dehydration method according to claim 14, further comprising the step of recycling 50 wt% or more of the mixture to the dehydration step.

17. The dehydration method according to claim 16, wherein in the recycling step, the at least a portion of the mixture is mixed with the raw material of the dehydration step, optionally supplemented with an additional amount of water, to adjust the water content of the raw material to a predetermined value.

18. A method for producing propylene, comprising the steps of: hydrogenating acetone as a raw material in the presence of a hydrogenation catalyst to produce a product containing isopropyl alcohol, separating the product containing isopropyl alcohol to obtain a gas phase containing hydrogen and a liquid phase containing isopropyl alcohol, separating the liquid phase containing isopropyl alcohol to obtain isopropyl alcohol, subjecting the isopropyl alcohol to a dehydration reaction according to the dehydration method of any one of claims 1 to 17 to produce a product containing propylene, referred to as a dehydration step, washing the product containing propylene with an absorbent to obtain a crude propylene product and an enriched absorbent, separating the enriched absorbent to obtain an isopropyl alcohol / water azeotrope, removing heavy components from the crude propylene product to obtain a refined propylene.

19. The method for producing propylene according to claim 18, further comprising the step of: recycling 50 wt% or more of the isopropyl alcohol / water azeotrope to the dehydration step. ​ ​ ​ ​ ​ ​ ​ ​

Images