Fluorinated alkylene oxide isomerization catalyst and preparation method and application thereof

Abstract

The present invention provides a fluorinated alkylene oxide isomerization catalyst and a preparation method and application thereof, wherein the catalyst system comprises a fluorinated alumina catalyst component and an auxiliary component, and the impurity metal element content in the two is maintained at an extremely low level, and the impurity metal element includes: alkali metal, alkaline earth metal, chromium, titanium, tungsten, tin, vanadium, iron, copper, silver, zirconium and zinc. The catalyst of the present invention has an extremely low impurity metal content and uses the combined component and the auxiliary component in combination, thereby achieving excellent raw material conversion rate, product selectivity, reaction stability, catalyst life and excellent reaction system temperature control.

Description

Technical Field

[0001] The invention belongs to the field of catalytic reactions, and in particular relates to a novel catalyst for isomerization reaction of fluorinated compounds, a preparation method and application thereof. Background Art

[0002] Various fluorinated carbonyl compounds (also known as fluorinated ketones or fluorinated ketones) have a wide range of uses in various chemical fields. For example, hexafluoroacetone (CF3COCF3, referred to as HFA) is one of the most commonly used fluorinated carbonyl compounds. Due to its unique physical and chemical properties, it is widely used as an intermediate in medicine, biochemistry, synthetic materials, microelectronics, aerospace and other fields. With the rapid development of these fields, people's interest in hexafluoroacetone and other similar fluorinated carbonyl compounds has increased year by year.

[0003] At present, the synthesis method of hexafluoroacetone mainly includes acetone direct fluorination method, hexafluoropropylene catalytic oxidation method, octafluoroisobutylene oxidation method, hexachloroacetone gas exchange method, etc., and the most widely used method is to use hexafluoropropylene oxide as raw material, and to generate hexafluoroacetone through molecular rearrangement isomerization. In the prior art, this method mainly uses oxides, chlorides or acyl chlorides of elements such as Cr, Al, Ti, W, Sn, V, Fe, Cu, Zr as catalysts for this reaction, but according to reports, the technology using these catalysts all has insurmountable defects. Specifically, the catalytic activity of these catalysts is always unsatisfactory, whether it is the conversion rate of raw material hexafluoropropylene oxide, the selectivity and yield of product hexafluoroacetone are all on the low side. In addition, the isomerization reaction is a highly exothermic reaction. During the reaction, the catalyst bed is prone to temperature spikes, which reduces the stability of the reaction operation and causes the catalyst to deactivate in a short period of time. To address the above problems, the countermeasures adopted by people are to frequently replace fresh catalysts or use inert dilution gases to reduce the raw material concentration in the reaction system. However, the frequent shutdowns and reduced production flux caused by these practices will also significantly affect the production capacity of the factory. These problems are also what people hope to avoid.

[0004] In the past few decades, people have conducted a lot of research to solve the above problems. For example, people have tried to dope or combine existing catalysts in various ways. These attempts may alleviate the above problems to a certain extent in one aspect, but they often cannot solve other problems at the same time. For example, a certain doping technology reported can slightly improve the conversion rate, but problems such as runaway temperature, reaction stability and catalyst life cannot be solved at the same time. In addition, doping existing catalysts often brings new problems, such as the generation of new by-products, which creates new problems for product purity and downstream purification and utilization.

[0005] In order to solve the above problems, the inventors of this application have conducted a lot of research and found that by strictly controlling the content of impurity metals in the catalytic system and arranging the catalyst and the additive in the form of alternating layers, all of the above problems can be solved at the same time, and excellent raw material conversion rate, product selectivity, reaction stability, catalyst life and excellent reaction system temperature control can be achieved, and significant improvements in process efficiency and economic benefits can be achieved. Based on the above research results, the technical purpose of the present invention is achieved. Summary of the invention

[0006] The first aspect of the present invention provides a fluorinated alkylene oxide isomerization catalyst, the catalyst comprising a fluorinated-alumina catalyst component and an auxiliary component, the fluorinated-alumina catalyst component comprising alumina and fluorine, and based on the weight of the fluorinated-alumina catalyst component, the fluorine content in the fluorinated-alumina catalyst component is 5-67.8% by weight, the total content of impurity metal elements in the isomerization catalyst is less than 0.065% by weight, and the impurity metal elements include: alkali metals, alkaline earth metals, chromium, titanium, tungsten, tin, vanadium, iron, copper, silver, zirconium and zinc. Preferably, the auxiliary component is selected from: graphene, silicon carbide, boron nitride, aluminum nitride, diamond, polysilicon, or a combination thereof.

[0007] The second aspect of the present invention provides a method for synthesizing the catalyst of the present invention, which comprises: (A) providing aluminum oxide, an auxiliary agent and a molding agent, wherein the dry weight ratio of impurity metal elements contained in the aluminum oxide, the auxiliary agent and the molding agent is less than 0.065 weight %; (B) mixing the aluminum oxide, the auxiliary agent and the molding agent to form a raw material mixture, extruding, drying and sintering the raw material mixture to form a catalyst precursor; (C) fluorinating the catalyst precursor with a fluorinating agent to form the catalyst.

[0008] According to one embodiment of the second aspect of the present application, in step (B), the raw material mixture is kneaded and slurried before extrusion molding.

[0009] According to another embodiment of the second aspect of the present application, the molding agent comprises an acidic solution and a solid molding agent selected from the following: methylcellulose, ethylcellulose, propylcellulose, carboxymethylcellulose, cellulose acetate butyrate, hydroxypropylcellulose, hydroxypropylmethylcellulose, polyether resin, polyester resin, polyvinyl chloride resin, polyethylene oxide, polypropylene oxide, polyvinyl alcohol, styrene-butadiene-styrene (SBS) resin, starch, modified starch, guar gum, substituted agar, dextrin. According to another embodiment of the second aspect of the present application, the concentration of the acidic solution is 0.1-8wt%. According to another embodiment of the second aspect of the present application, based on the total weight of the raw material mixture, the content of the aluminum oxide is 10-69% by weight, the content of the auxiliary agent is 10-69% by weight, the content of the acidic solution is 10-50% by weight, and the content of the solid molding agent is 0.1-20% by weight.

[0010] According to another embodiment of the second aspect of the present application, in step (B), the temperature used for drying is 70-200°C, and the drying time is 2h-24h. According to another embodiment of the second aspect of the present application, sintering includes sintering at a temperature range of 300-400°C for 1-3 hours, and then sintering at a temperature range of 530-570°C for 4-7 hours. According to another embodiment of the second aspect of the present application, step (C) includes fluorinating the catalyst precursor with a mixed gas of hydrogen fluoride and nitrogen at a temperature of 150-300oC, in which the volume content of hydrogen fluoride is 1-20 volume %.

[0011] A third aspect of the present invention provides a method for forming a carbonyl-containing product by catalytic isomerization of a fluorinated alkylene oxide, the method comprising subjecting the fluorinated alkylene oxide to a catalytic isomerization reaction in the presence of the catalyst of the present invention.

[0012] According to one embodiment of the third aspect of the present invention, the fluorinated oxirane is selected from tetrafluoroethylene oxide, hexafluoropropylene oxide, perfluorobutylene oxide, perfluoropentane oxide, perfluorohexane oxide, perfluoroheptane oxide, perfluorooctane oxide, and combinations thereof. According to another embodiment of the third aspect of the present invention, the carbonyl-containing product is selected from tetrafluoroacetaldehyde, hexafluoroacetone, perfluorobutanone, perfluoropentanone, perfluorohexanone, perfluoroheptanone, and perfluorooctanone. According to another embodiment of the third aspect of the present invention, the catalytic isomerization reaction is carried out at a temperature of 0-140°C and a pressure of 0.1-0.4MPa.

[0013] In the following detailed description section, the process and design of the present application are described in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 The reaction mechanism of synthesizing hexafluoroacetone by catalytic isomerization of hexafluoropropylene oxide according to one embodiment of the present application is shown;

[0015] Figure 2 A process flow chart of a method for synthesizing an isomerization catalyst according to one embodiment of the present application is shown;

[0016] Figure 3 The results of investigating the stability and catalyst life of one embodiment of the present invention are shown. DETAILED DESCRIPTION

[0017] "Range" disclosed herein is in the form of lower limit and upper limit. It can be one or more lower limits, and one or more upper limits respectively. A given range is defined by selecting a lower limit and an upper limit. The selected lower limit and upper limit define the boundaries of a particular range. All ranges that can be defined in this way are inclusive and combinable, i.e. any lower limit can be combined with any upper limit to form a range. For example, a range of 60-120 and 80-110 is listed for a particular parameter, and it is understood that a range of 60-110 and 80-120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following ranges can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5.

[0018] In the present invention, unless otherwise specified, the numerical range "ab" represents an abbreviation of any real number combination between a and b, where a and b are real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" have been listed in this document, and "0-5" is just an abbreviation of these numerical combinations.

[0019] In the present invention, unless otherwise specified, all embodiments and preferred embodiments mentioned herein can be combined with each other to form a new technical solution.

[0020] In the present invention, unless otherwise specified, all the technical features and preferred features mentioned herein can be combined with each other to form a new technical solution.

[0021] In the present invention, unless otherwise specified, all steps mentioned herein may be performed sequentially or randomly, but are preferably performed sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0022] In the present invention, if there is no special explanation, the "including" mentioned herein means open or closed. For example, the "including" may mean that other components not listed may also be included, or only the listed components may be included.

[0023] In the present invention, when describing the spatial relationship of a specific component or object relative to other components or objects, the terms "inside", "outside", "above", "below", etc. are used to indicate that the former is located inside, outside, above or below the latter, and the two may be in direct contact, or be separated by a certain distance or separated by a third component or object.

[0024] It should be emphasized that what is shown in the drawings and described below are only some specific embodiments of the present invention, and the protection scope of the present invention is not limited to these specific embodiments. The protection scope of the present invention is defined by the claims of the present invention, and may include any technical solution within the scope of the claims, including but not limited to further improvements and substitutions to these specific embodiments.

[0025] In the following, mainly based on the reaction of synthesizing the target product hexafluoroacetone by catalytic isomerization with hexafluoropropylene oxide as raw material, the characteristics and advantages of the method of the present invention are specifically described, but the scope of application of the method of the present invention is not limited to this. In fact, the method of the present invention can also be used to catalyze the isomerization reaction of other fluorinated epoxy raw materials to synthesize the corresponding fluorinated carbonyl-containing products and achieve similar technical effects. For example, as a non-limiting example, examples of fluorinated oxirane hydrocarbons that can be used for the isomerization reaction of the present application can include fluorinated C2-C22 oxirane hydrocarbons. According to one embodiment, the fluorinated oxirane hydrocarbons can include 2-22 carbon atoms, such as 3-16 carbon atoms, or 3-12 carbon atoms, or 3-10 carbon atoms, or 3-8 carbon atoms, or 3-6 carbon atoms, or 3-4 carbon atoms. According to another embodiment, the fluorinated C2-C22 oxirane hydrocarbons include one, two or three oxirane groups. According to another embodiment, at least 50% of the hydrogen atoms in the fluorinated C2-C22 alkylene oxide are replaced by fluorine atoms, for example, at least 55%, or at least 60%, or at least 65%, or at least 70%, or at least 75%, or at least 80%, or at least 85%, or at least 90%, or at least 95%, or 100% (i.e., perfluorinated) hydrogen atoms are replaced by fluorine atoms. According to a preferred embodiment of the application, examples of the raw materials include tetrafluoroethylene oxide, hexafluoropropylene oxide, perfluorobutylene oxide, perfluoropentene oxide, perfluorohexylene oxide, perfluoroheptane oxide, and perfluorooctane oxide.

[0026] Accordingly, the product synthesized from the above raw materials may include a fluorinated C2-C22 carbonyl-containing compound. According to one embodiment, the fluorinated carbonyl-containing compound may include 2-22 carbon atoms, such as 3-16 carbon atoms, or 3-12 carbon atoms, or 3-10 carbon atoms, or 3-8 carbon atoms, or 3-6 carbon atoms, or 3-4 carbon atoms. According to another embodiment, the fluorinated C2-C22 carbonyl-containing compound includes one, two or three carbonyl groups. According to another embodiment, at least 50% of the hydrogen atoms in the fluorinated C2-C22 carbonyl-containing compound are replaced by fluorine atoms, such as at least 55%, or at least 60%, or at least 65%, or at least 70%, or at least 75%, or at least 80%, or at least 85%, or at least 90%, or at least 95%, or 100% (i.e., perfluorinated) hydrogen atoms are replaced by fluorine atoms. According to a preferred embodiment of the present application, examples of the product include tetrafluoroacetaldehyde, hexafluoroacetone, perfluorobutanone, perfluoropentanone, perfluorohexanone, perfluoroheptanone, and perfluorooctanone.

[0027] Figure 1A schematic diagram of a reaction mechanism according to one embodiment of the present application is shown. In the reaction, hexafluoropropylene oxide is used as a raw material, and under the catalytic action of the catalyst of the present application, an isomerization reaction occurs to form the target product hexafluoroacetone.

[0028] According to a non-limiting embodiment of the present application, the catalyst is specially designed by combining the fluoride-alumina catalytic component with the auxiliary component, preferably mixing the two evenly, and strictly controlling the content of impure metals in the final catalyst, while achieving significant improvement in catalytic performance and excellent temperature control.

[0029] According to one embodiment of the present application, the catalyst of the present invention comprises a fluorinated-alumina catalytic component, which can be obtained by fluoriding alumina, and preferably the fluorinated-alumina catalytic component is substantially composed of alumina and fluorine. Based on the total weight of the fluorinated-alumina catalytic component, the fluorine content is 5-67.8% by weight, such as 6-66% by weight, or 7-65% by weight, or 8-60% by weight, or 9-55% by weight, or 10-50% by weight, or 12-45% by weight, or 15-40% by weight, or 18-35% by weight, or 20-30% by weight, or 22-25% by weight, or 52-62% by weight, or within the numerical range obtained by combining any two of the above end values. According to another embodiment of the present application, based on the total weight of the isomerization catalyst, the total content of impurity metal elements in the isomerization catalyst is less than 0.065 wt%, such as less than 0.06 wt%, or less than 0.055 wt%, or less than 0.05 wt%, or less than 0.045 wt%, or less than 0.04 wt%, or less than 0.035 wt%, or less than 0.03 wt%, or less than 0.025 wt%, or less than 0.02 wt%, or less than 0.015 wt%, or less than 0.01 wt%. According to another embodiment of the present application, based on the total weight of the isomerization catalyst, the total content of all impurities (i.e., the combination of the impurity metal elements and other impurities described above) in the isomerization catalyst is less than 0.065 wt%. According to one embodiment of the present application, based on the total weight of the fluorinated-alumina catalyst component, the total content of impurity metal elements in the fluorinated-alumina catalyst component is less than 0.05% by weight, such as less than 0.045% by weight, or less than 0.04% by weight, or less than 0.035% by weight, or less than 0.03% by weight, or less than 0.025% by weight, or less than 0.02% by weight, or less than 0.015% by weight, or less than 0.01% by weight. According to one embodiment of the present application, based on the total weight of the auxiliary component, the total content of impurity metal elements in the auxiliary component is less than 0.02% by weight, such as less than 0.015% by weight, or less than 0.01% by weight, or less than 0.008% by weight, or less than 0.005% by weight, or less than 0.003% by weight, or less than 0.002% by weight, or less than 0.001% by weight.

[0030] According to one embodiment of the present application, the impurity metal elements include: alkali metals, alkaline earth metals, chromium, titanium, tungsten, tin, vanadium, iron, copper, silver, zirconium and zinc; the alkali metals include lithium, sodium, potassium, rubidium, cesium, and the alkaline earth metals include beryllium, magnesium, calcium, strontium, and barium. In the present application, the impurity metal elements refer to impurities introduced accidentally, such as impurities introduced by raw materials, processing reagents, reaction vessels and pipelines or other accidental factors, and the impurity metal elements (or any impurities including the impurity metal elements) are avoided as much as possible from entering the catalyst of the present invention by using high-purity raw materials (high-purity alumina, high-purity additives) and reagents (such as high-purity acidic solutions, high-purity forming agents) and strictly specifying equipment and process conditions. According to one embodiment of the present application, the impurity metal elements (or any impurities including the impurity metal elements) will not be intentionally introduced into the catalyst in the form of raw materials. According to a specific embodiment of the present application, any one or more of the above elements are excluded as much as possible from the isomerization catalyst of the present application. In addition, if any of the above elements is introduced into the catalyst of the present application as an accidental impurity, the content of any of the metal elements (or any impurities including the above impurity metal elements) in the isomerization catalyst of the present application is less than 0.065% by weight, for example, less than 0.06% by weight, or less than 0.055% by weight, or less than 0.05% by weight, or less than 0.045% by weight, or less than 0.04% by weight, or less than 0.035% by weight, or less than 0.03% by weight, or less than 0.025% by weight, or less than 0.02% by weight, or less than 0.015% by weight, or less than 0.01% by weight, or less than 0.005% by weight, or less than 0.001% by weight. According to a preferred embodiment of the present application, in addition to the above-mentioned fluorine and the impurities introduced accidentally (to be reduced or avoided as much as possible), the balance of the isomerization catalyst of the present invention is alumina and an additive (an inert thermal conductive additive), that is, no other components are intentionally added.

[0031] According to another embodiment of the present application, the fluorinated-alumina catalytic component in the isomerization catalyst is uniformly mixed with the auxiliary component. In the present invention, the term "uniformly mixed" means that in the entire isomerization catalyst, the concentration of the catalytic component at any point in the isomerization catalyst bed relative to the average weight concentration of the catalytic component (the total weight of the used catalyst component divided by the total volume of the bed filled with the prepared isomerization catalyst) is less than 5%, for example, less than 3%, or less than 2%, or less than 1%, or less than 0.5%, or less than 0.2%, or less than 0.1%, or less than 0.05%, or less than 0.01%.

[0032] According to one embodiment of the present application, based on the total weight of the isomerization catalyst of the present invention, the content of the fluorinated-alumina catalytic component is 1-99 weight%, for example, 5-95 weight%, or 10-90 weight%, or 15-85 weight%, or 20-80 weight%, or 25-75 weight%, or 30-70 weight%, or 35-65 weight%, or 40-60 weight%, or 45-55 weight%, or 48-50 weight%, or within the numerical range obtained by combining any two of the above end values. According to another embodiment of the present application, based on the total weight of the isomerization catalyst of the present invention, the content of the auxiliary component is 1-99 weight %, for example, 5-95 weight %, or 10-90 weight %, or 15-85 weight %, or 20-80 weight %, or 25-75 weight %, or 30-70 weight %, or 35-65 weight %, or 40-60 weight %, or 45-55 weight %, or 48-50 weight %, or within the numerical range obtained by combining any two of the above end values. According to another embodiment of the present application, in addition to the above-mentioned fluorinated-alumina catalytic component and the auxiliary component, the content of other components is ≤5 weight %, or ≤4 weight %, or ≤3 weight %, or ≤2 weight %, or ≤1 weight %, or ≤0.5 weight %, or ≤0.2 weight %, or ≤0.1 weight %, or ≤0.06 weight %, or ≤0.05 weight %, or ≤0.02 weight %, or ≤0.01 weight %. According to another embodiment of the present application, the catalyst system consists of the fluorinated-alumina catalyst component and an auxiliary component.

[0033] In the present application, the terms "auxiliary component", "auxiliary agent", "inert auxiliary agent", "inert thermal conductivity auxiliary agent", "inert thermal conductivity auxiliary agent" and "inert heat dissipation auxiliary agent" can be used interchangeably, and are all used to refer to the auxiliary agent component used in combination with the fluoride-alumina catalytic component in the catalyst of the present application to improve the temperature control and temperature stability of the catalyst system during the isomerization reaction.

[0034] The auxiliary agent component used in the catalyst of the present invention needs to meet two requirements in terms of performance. First, the auxiliary agent component should be substantially inert under the isomerization reaction conditions, will not have any adverse interactions with the raw materials, products, and by-products, will not hinder or block the flow of materials in the reactor, and will not have any negative impact on the raw material conversion rate, product selectivity, and product yield of the isomerization reaction. In addition, the auxiliary agent should have excellent or extremely high thermal conductivity (high thermal conductivity coefficient) to effectively assist the heat dissipation in the reactor (especially in the reaction bed). For example, according to a non-limiting embodiment of the present application, the auxiliary agent may be a high thermal conductivity material with a thermal conductivity coefficient of ≥20 w / (m·k), for example, its thermal conductivity coefficient may be ≥30 w / (m·k), or ≥40 w / (m·k), or ≥50 w / (m·k), or ≥60 w / (m·k), or ≥70 w / (m·k), or ≥80 w / (m·k), or ≥90 w / (m·k), or ≥100 w / (m·k), or ≥110 w / (m·k), or ≥120 w / (m·k ), or ≥130w / (m·k), or ≥150w / (m·k), or ≥180w / (m·k), or ≥200w / (m·k), or ≥250w / (m·k), or ≥300w / (m·k), or ≥350w / (m·k), or ≥400w / (m·k), or ≥450w / (m·k), or ≥500w / (m·k), or ≥600w / (m·k), or ≥800w / (m·k), or ≥1000w / (m·k).

[0035] According to an exemplary embodiment of the present application, the auxiliary component is selected from: graphene, silicon carbide, boron nitride, aluminum nitride, diamond, polysilicon, or a combination thereof.

[0036] According to another embodiment of the present application, when the catalytic reaction is carried out, the catalyst of the present invention is filled in the reactor to form a bed, and the fluorinated-alumina catalyst component and the auxiliary component are uniformly mixed with each other and uniformly distributed in the bed. According to an exemplary embodiment of the present application, the thickness of the filled catalyst layer (or bed) (that is, the height along the main axis direction of the reactor) can be adjusted as needed, for example, the thickness of the catalyst layer (or bed) can be 1-10 cm, or 1-8 cm, or 1-6 cm, or 1-5 cm, or 1-3 cm.

[0037] According to one embodiment of the present application, the isomerization reaction of the present invention can be carried out in a suitable reactor, for example, in a fixed bed reactor, the fixed bed reactor can have an elongated tubular structure, and the catalyst of the present invention can be filled in the elongated tubular fixed bed reactor to form one or more catalyst beds. According to one embodiment of the present application, one or more other beds, such as a filter bed, a protective bed, a heat-conducting bed, etc., can be arranged upstream and / or downstream of each catalyst bed. In the process of isomerization reaction, the raw material is introduced from the inlet of the reactor, and a large amount of heat is released while the isomerization reaction occurs when flowing through the catalyst bed. A considerable part of the heat generated is carried away by the logistics or effectively transferred by the inert auxiliary agent with high thermal conductivity contained in the catalyst bed, and dissipated through the outer wall of the fixed bed reactor (and the heat dissipation pipe, heat dissipation sleeve, heat sink, etc. that may be arranged around the outer wall of the fixed bed), thereby ensuring the temperature stability in the entire reactor.

[0038] Figure 2 A process flow chart showing a method for synthesizing the isomerization catalyst of the present invention is shown.

[0039] The synthesis method first includes step (A): providing aluminum oxide, an inert thermal conductivity aid and a molding agent, wherein the dry weight ratio of the impurity metal elements contained in the aluminum oxide, the inert thermal conductivity aid and the molding agent is less than 0.065% by weight. In order to minimize the introduction of the impurity metal elements, the aluminum oxide used here is high-purity aluminum oxide or ultra-high-purity aluminum oxide. The auxiliary agent component is selected from: graphene, silicon carbide, boron nitride, aluminum nitride, diamond, polycrystalline silicon, or a combination thereof. In order to minimize the introduction of the impurity metal elements, the auxiliary agent component used here is also selected as a high-purity auxiliary agent provided by the supplier as much as possible. The forming agent used comprises an acidic solution and a solid forming agent selected from the group consisting of methylcellulose, ethylcellulose, propylcellulose, carboxymethylcellulose, cellulose acetate butyrate, hydroxypropylcellulose, hydroxypropylmethylcellulose, polyether resins, polyester resins, polyvinyl chloride resins, polyethylene oxide, polypropylene oxide, polyvinyl alcohol, styrene-butadiene-styrene (SBS) resins, starch, modified starch, guar gum, substituted agar, dextrin, and a combination of two or more of the above-mentioned solid forming agents. In order to minimize the introduction of the impurity metal elements, the acidic solution and the solid forming agent are also prepared using high-purity raw materials as much as possible, such as by selecting analytically pure raw materials or by adopting high-purity raw materials provided by suppliers, to reduce the content of the impurity metal elements therein so that it meets the requirements of the present invention.

[0040] According to one embodiment of the present application, in step (A), the acidic solution can be any conventional acidic solution, such as nitric acid solution, trifluoroacetic acid solution, oxalic acid solution, formic acid solution, acetic acid solution, propionic acid solution, etc., as long as it can be removed in the subsequent processing steps and drying and sintering steps, and the impurity metal elements are not significantly introduced. According to another embodiment of the present application, the concentration of the acidic solution is 0.1-8% by weight, such as 0.5-7% by weight, or 1-6.5% by weight, or 2-6% by weight, or 3-5.5% by weight, or 4-5% by weight.

[0041] According to another embodiment of the present application, based on the total weight of the raw material mixture, the content of the aluminum oxide is 10-69% by weight, and the aluminum oxide content described here is based on the solid dry weight of the aluminum oxide, for example, the content of the aluminum oxide can be 15-65% by weight, or 20-60% by weight, or 25-55% by weight, or 30-50% by weight, or 35-45% by weight, or 40-45% by weight, or can be within the numerical range obtained by combining any two of the above end values. According to another embodiment of the present application, based on the total weight of the raw material mixture, the content of the auxiliary agent is 10-69% by weight, and the auxiliary agent content described here is based on the solid dry weight, for example, the content of the inert thermal conductive auxiliary agent can be 15-65% by weight, or 20-60% by weight, or 25-55% by weight, or 30-50% by weight, or 35-45% by weight, or 40-45% by weight, or can be within the numerical range obtained by combining any two of the above end values. According to another embodiment of the present application, based on the total weight of the raw material mixture, the content of the acidic solution is 10-50% by weight, and the acidic solution content described herein is based on the total weight of the acidic solution, that is, including the weight of the acid / acidic substance and the solvent (water) in the solution, for example, the content of the acidic solution can be 15-50% by weight, or 20-50% by weight, or 25-50% by weight, or 30-45% by weight, or 35-40% by weight, or can be within the numerical range obtained by combining any two of the above end values. According to another embodiment of the present application, based on the total weight of the raw material mixture, the content of the solid forming agent is 0.1-20% by weight, and the solid forming agent content described herein is based on the solid dry weight of the solid forming agent, for example, the content of the solid forming agent can be 0.5-18% by weight, or 1-16% by weight, or 2-15% by weight, or 5-12% by weight, or 8-10% by weight, or can be within the numerical range obtained by combining any two of the above end values.

[0042] In step (B) of the synthesis method, the alumina, the inert thermal conductivity aid and the molding agent are mixed to form a raw material mixture, and the raw material mixture is sequentially subjected to extrusion molding, drying and sintering to form a catalyst precursor. According to a preferred embodiment of the present application, before the extrusion molding, the raw material mixture is also kneaded and slurried.

[0043] According to one embodiment of the present application, the kneading can be performed using a conventional kneading machine under a certain pressure (for example, a pressure of 0.2-0.5MPa) for pressurized kneading. The kneading machine usually includes a pair of mixing blades that cooperate and rotate with each other. The strong shearing effect generated by these blades allows various materials to be evenly mixed. The discharging methods of the kneading machine may include hydraulic discharging, cylinder unloading, ball valve discharging, etc. The mud kneading can be performed manually or in a conventional mechanical vacuum mud kneading machine. The air in the raw material mixture is removed more thoroughly through mud kneading, the mixture is more uniform, the plasticity and density are further improved, and the molding ability of the mixture is improved. The extrusion molding can be performed using a conventional extruder. Examples of extruders may include twin-screw extruders, single-screw extruders, etc. According to one embodiment of the present application, an extruder is used to extrude the raw material mixture to form a target reactor (for example Figure 2 The catalyst bed is conveniently loaded and replaced by a plug (or sheet) that is adapted to the internal size of the fixed bed reactor shown in the figure. According to another embodiment of the present application, the raw material mixture is extruded into small particles or small pellets using an extruder, and these small particles or small pellets are filled into the reactor to form a catalyst bed when used.

[0044] According to another embodiment of the present application, drying can be carried out using any conventional drying equipment (such as an infrared oven, a convection oven, etc.); the drying temperature used can be 70-200°C, such as 80-180°C, or 90-160°C, or 100-150°C, or 110-140°C, or 120-130°C, or within the numerical range obtained by combining any two of the above end values; the duration of the drying process can be 2-24 hours, such as 3-22 hours, or 4-20 hours, or 6-18 hours, or 8-16 hours, or 10-12 hours, or within the numerical range obtained by combining any two of the above end values. Drying can be carried out in a suitable atmosphere, such as in an air atmosphere, or in an inert atmosphere (such as a nitrogen atmosphere) or under vacuum conditions. According to another embodiment of the present application, the sintering process can be carried out in any conventional equipment, such as in a muffle furnace, a tubular furnace, or other roasting equipment. The sintering temperature may be 300-700°C, and the sintering time may be 1-24 hours, for example, sintering at a temperature range of 300-400°C for 1-3 hours, and then sintering at a temperature range of 530-570°C for 4-7 hours.

[0045] In step (C) of the synthesis method, the catalyst precursor is fluorinated with a fluorinating agent to form the isomerization catalyst of the present invention. According to an exemplary embodiment, step (C) includes fluorinating the catalyst precursor with a mixed gas of hydrogen fluoride and nitrogen at a temperature of 150-300°C, wherein the volume content of hydrogen fluoride in the mixed gas is 1-20% by volume based on the total volume of the mixed gas; the temperature used in the fluorination step can be 170-280°C, such as 180-260°C, or 200-220°C; the duration of the fluorination step can be 1-24 hours, such as 2-20 hours, or 3-18 hours, or 4-16 hours, or 6-12 hours, or 8-10 hours.

[0046] According to one embodiment of the present application, the catalytic reaction is carried out in a temperature range of 0-140°C, for example, the temperature range can be 30-120°C, or 40-100°C, or the temperature can be within the range obtained by combining any two of the above end values. According to another embodiment of the present application, the catalyst of the present invention is loaded in a fixed bed reactor to form a catalyst bed. Since the catalyst bed contains uniformly distributed catalyst components and inert thermal conductive additive components, a stable state is reached after a short period of time after the start of the reaction. In this stable state, the temperature of each bed in the reactor can be controlled at 60-90°C, for example, 70-80°C, or in this stable state, the temperature can be maintained within the range obtained by combining any two of the above end values. During the reaction, the pressure in the reactor can be maintained at normal pressure or slightly positive pressure, for example, the gauge pressure can be displayed as 0-0.3 MPa, that is, the absolute temperature in the reactor can be maintained at about 0.1-0.4 MPa, for example, 0.15-0.35 MPa, or 0.2-0.3 MPa, or 0.25-0.28 MPa, or within the range obtained by combining any two of the above end values.

[0047] Without being limited to any specific theory, compared with the prior art, the method of the present invention has the following advantages:

[0048] 1. Excellent catalytic activity is achieved, for example, the raw material conversion rate can be as high as 100%, and the conversion rate of the target product (such as hexafluoroacetone) can be as high as 99% or more, avoiding the product containing unconverted raw materials (for example, hexafluoropropylene oxide and hexafluoroacetone have similar separation boiling points, and distillation separation is extremely difficult), so that hexafluoroacetone can be used directly after simple distillation, avoiding water absorption, and saving use steps.

[0049] 2. The catalyst developed by the present invention is inert to common impurities in raw materials such as hexafluoropropylene and will not cause these common impurities to react. Even if a small amount of impurities such as hexafluoropropylene are entrained in the hexafluoropropylene oxide raw material, it will not affect the reaction and subsequent product separation.

[0050] 3. The catalyst developed by the present invention can achieve extremely high reaction heat conduction efficiency, make the reaction temperature controllable, stabilize the reaction, significantly increase the reaction life, and is suitable for industrial production.

[0051] Any two or more of all the above-mentioned embodiments of the present invention may be arbitrarily combined with each other, and these combinations are also included in the overall technical concept of the present invention.

[0052] Any two or more of all the above-mentioned embodiments of the present invention may be arbitrarily combined with each other, and these combinations are also included in the overall technical concept of the present invention.

[0053] Example

[0054] The preferred embodiments of the present invention are specifically listed in the following examples, but it should be understood that the protection scope of the present invention is not limited thereto.

[0055] In the following examples and comparative examples, specially ordered high-purity aluminum oxide was used, and other chemical reagents used were of analytical grade, wherein the content of any impurity metal element described herein was less than 0.001% by weight, which was lower than the lower limit of ICP element analysis. Alumina powder having a sodium ion content of 0.5% by mass was obtained for comparative example 1 by deliberately adding a specific amount of sodium nitrate (added in the form of sodium nitrate aqueous solution, fully mixed and dried for standby use) to the specially ordered high-purity aluminum oxide.

[0056] Comparative Example 1: Preparation of Catalyst 1

[0057] Weigh 67.5 parts by weight of alumina powder (with a sodium ion content of 0.5% by mass), 30 parts by weight of a 5% by weight aqueous nitric acid solution and 2.5 parts by weight of carboxymethyl cellulose, knead them in a kneader, and then knead them in a mud kneader. Then, extrude them through a template with a circular hole of 4 mm in diameter in a single-screw extruder to form a granular material. The granular material is dried in an infrared oven at 120°C for 16 hours, then placed in a muffle furnace, calcined at 350°C for 1 hour, and then the muffle furnace is heated to 550°C and calcined at this temperature for another 5 hours to obtain a catalyst precursor. The above drying and calcination are both carried out in an atmospheric atmosphere. The granular catalyst precursor is loaded into a fixed bed reactor (reactor inner diameter is 2 cm, length is 80 mm), the reactor is heated to 250°C, a mixed gas of hydrogen fluoride and nitrogen with a volume ratio of 1:20 is passed into the reactor at a flow rate of 1 liter / minute, and ventilation is continued until hydrogen fluoride is detected in the outflowing tail gas, at which time the hydrogen fluoride is stopped, the reactor temperature is lowered to room temperature, and then nitrogen is passed at a flow rate of 1 liter / minute for purging until the outflowing tail gas does not contain hydrogen fluoride, thereby obtaining a catalyst for standby use. The catalyst synthesized in Comparative Example 1 is recorded as Catalyst 1. The fluorine content in Catalyst 1 is 57% as measured by EDS energy spectrum analysis.

[0058] Example 1: Preparation of Catalyst 2

[0059] Weigh 62.5 parts by weight of alumina powder (wherein the content of the impurity metal elements described herein is less than 0.001% by weight), 5 parts by weight of polysilicon powder (wherein the content of the impurity metal elements described herein is less than 0.001% by weight), 30 parts by weight of a 5% by weight nitric acid aqueous solution (wherein the content of the impurity metal elements described herein is less than 0.001% by weight), and 2.5 parts by weight of carboxymethyl cellulose (wherein the content of the impurity metal elements described herein is less than 0.001% by weight), knead them in a kneader, knead them in a mud kneader, and then extrude them through a template with a circular hole of 4 mm in diameter in a single-screw extruder to form a granular material, which is dried in an infrared oven at 120°C for 16 hours, then placed in a muffle furnace, calcined at 350°C for 1 hour, and then the muffle furnace is heated to 550°C and calcined at this temperature for another 5 hours to obtain a catalyst precursor. The above drying and calcination are both carried out under atmospheric atmosphere. The granular catalyst precursor is loaded into a fixed bed reactor (reactor inner diameter is 2 cm, length is 80 mm), the reactor is heated to 250°C, a mixed gas of hydrogen fluoride and nitrogen with a volume ratio of 1:20 is passed into the reactor at a flow rate of 1 liter / minute, and ventilation is continued until hydrogen fluoride is detected in the outflowing tail gas, at which time the hydrogen fluoride is stopped, the reactor temperature is lowered to room temperature, and then nitrogen is passed at a flow rate of 1 liter / minute for purging until the outflowing tail gas does not contain hydrogen fluoride, thereby obtaining a catalyst for use. The catalyst synthesized in Example 1 is recorded as catalyst 2. The fluorine content in catalyst 2 is 59% as measured by EDS spectrum analysis.

[0060] Example 2: Preparation of Catalyst 3

[0061] Weigh 50 parts by weight of alumina powder (wherein the content of the impurity metal elements described herein is less than 0.001 weight %), 15 parts by weight of silicon carbide powder (wherein the content of the impurity metal elements described herein is less than 0.001 weight %), 30 parts by weight of a 5 weight % nitric acid aqueous solution (wherein the content of the impurity metal elements described herein is less than 0.001 weight %) and 5 parts of carboxymethyl cellulose (wherein the content of the impurity metal elements described herein is less than 0.001 weight %), knead them in a kneader, knead them in a mud kneader, and then extrude them through a template with a circular hole of 4 mm in diameter in a single-screw extruder to form a granular material, which is dried in an infrared oven at 120°C for 16 h, then placed in a muffle furnace, calcined at 350°C for 1 h, and then the muffle furnace is heated to 550°C and calcined at this temperature for another 5 h to obtain a catalyst precursor. The above drying and calcination are both carried out under atmospheric atmosphere. The granular catalyst precursor is loaded into a fixed bed reactor (reactor inner diameter is 2 cm, length is 80 mm), the reactor is heated to 250°C, a mixed gas of hydrogen fluoride and nitrogen with a volume ratio of 1:20 is passed into the reactor at a flow rate of 1 liter / minute, and ventilation is continued until hydrogen fluoride is detected in the outflowing tail gas, at which time the hydrogen fluoride is stopped, the reactor temperature is lowered to room temperature, and then nitrogen is passed at a flow rate of 1 liter / minute for purging until the outflowing tail gas does not contain hydrogen fluoride, thereby obtaining a catalyst for use. The catalyst synthesized in Example 2 is recorded as catalyst 3. The fluorine content in catalyst 3 is 54% as measured by EDS energy spectrum analysis.

[0062] Example 3: Preparation of Catalyst 4

[0063] Weigh 25 parts by weight of alumina powder (wherein the content of impurity metal elements described in this article is less than 0.001 weight %), 25 parts by weight of carbonized nitrogen powder (wherein the content of impurity metal elements described in this article is less than 0.001 weight %), 30 parts by weight of 5 weight % nitric acid aqueous solution (wherein the content of impurity metal elements described in this article is less than 0.001 weight %) and 5 parts by weight of carboxymethyl cellulose (wherein the content of impurity metal elements described in this article is less than 0.001 weight %), knead them in a kneader, knead them in a mud kneader, and then extrude them through a template with a circular hole of 4 mm in diameter in a single-screw extruder to form a granular material, the granular material is dried in an infrared oven at 120°C for 16 hours, then placed in a muffle furnace, calcined at 350°C for 1 hour, and then the muffle furnace is heated to 550°C and calcined at this temperature for another 5 hours to obtain a catalyst precursor, and the above drying and calcination are carried out under atmospheric atmosphere. The catalyst precursor is loaded into a fixed bed reactor (reactor inner diameter 2cm, length 80mm), the reactor is heated to 250°C, a mixed gas of hydrogen fluoride and nitrogen with a volume ratio of 1:20 is passed into the reactor at a flow rate of 1 liter / minute, and ventilation is continued until hydrogen fluoride is detected in the outflowing tail gas, at which time the hydrogen fluoride is stopped, the reactor temperature is lowered to room temperature, and then nitrogen is passed at a flow rate of 1 liter / minute for purging until the outflowing tail gas does not contain hydrogen fluoride, thereby obtaining a catalyst for use. The catalyst synthesized in Example 3 is recorded as catalyst 4. The fluorine content in catalyst 4 is 60% as measured by EDS energy spectrum analysis.

[0064] Example 4: Characterization of the catalytic performance of the catalyst in the catalytic isomerization of hexafluoropropylene oxide to produce hexafluoroacetone

[0065] The reaction was carried out in a fixed bed reactor (reactor inner diameter 1 mm, length 40 mm), and 80 g of the catalysts 1-4 synthesized in the above Comparative Example 1 and Examples 1, 2, and 3 were respectively loaded into independent fixed bed reactors.

[0066] A uniform mixed gas flow of hexafluoropropylene oxide (HFPO) raw material and nitrogen was input into the reactor, the mass flow rate of HFPO was maintained at 0.5 g / min, and the nitrogen flow rate was 80 ml / min. The temperature in the reactor was maintained at 5°C, 15°C, 30°C, 60°C, 80°C and 100°C, respectively, and the operating pressure was normal pressure. About 1 hour after the reaction started, the gas flow flowing out of the reactor was analyzed and measured using gas chromatography. The chromatographic analysis results are shown in Table 1.

[0067] Table 1 Comparison of reaction performance results of different catalyst samples

[0068]

[0069] As can be seen from Table 1, the HFPO conversion rate of the experiments using catalysts 2, 3 and 4 in the reaction temperature range of 5°C-100°C reached 100%, and the HFA selectivity reached more than 99%. In contrast, the HFPO conversion rate and HFA selectivity of the experiment using catalyst 1 as a comparative example were very low, indicating that the catalyst of the present invention has a more excellent reaction performance in the low temperature region and has a significant low-temperature reaction activity compared with the catalyst in the prior art that does not strictly control the impurity metal elements due to the strict control of the impurity metal elements.

[0070] These experimental results indicate that the reaction performance of catalysts with low metal element impurities has been greatly improved, and high-purity hexafluoroacetone hydrate can be obtained by simple distillation separation.

[0071] Example 5: Catalyst life test

[0072] In Example 5, Catalyst 2 was used, and the reaction system was constructed as described in Example 4. However, the reaction was allowed to continue for a long time to investigate the stability and life of the catalyst. The operating pressure was normal pressure, and the contact time was about 15.0 seconds. During the entire catalytic reaction process lasting 3600 hours, the conversion rate and flow rate of the raw material HFPO, the temperature in the reaction system, and the selectivity of the product HFA were continuously detected. The results are as follows: Figure 3 As shown. Figure 3 The results shown show that the catalyst system of the present invention has good reaction stability during the long-term reaction process, the hexafluoropropylene oxide conversion rate is always maintained at 100%, the hexafluoroacetone selectivity is maintained at more than 99%, the temperature also maintains excellent stability, and the performance does not change significantly after the reaction exceeds 3600h.

[0073] The above embodiments are only for illustrating the technical concept and technical features of the present invention, and cannot be used to limit the protection scope of the present invention. Any equivalent transformation or modification made according to the essence of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for forming a carbonyl-containing product by catalytic isomerization of a fluorinated alkylene oxide, the method comprising subjecting the fluorinated alkylene oxide to a catalytic isomerization reaction in the presence of a catalyst, wherein the catalytic isomerization reaction is carried out at a temperature of 0-140° C. and a pressure of 0.1-0.4 MPa; The catalyst comprises a fluorided-alumina catalyst component and an auxiliary component, wherein the fluorided-alumina catalyst component comprises alumina and fluorine, and based on the weight of the fluorided-alumina catalyst component, the fluorine content in the fluorided-alumina catalyst component is 52-65% by weight, and the total content of impurity metal elements in the catalyst is less than 0.01% by weight, and the impurity metal elements include: alkali metals, alkaline earth metals, chromium, titanium, tungsten, tin, vanadium, iron, copper, silver, zirconium and zinc; The auxiliary component is selected from: graphene, silicon carbide, boron nitride, aluminum nitride, diamond, polysilicon or a combination thereof; The catalyst consists of the catalytic component and the auxiliary component, and based on the weight of the catalyst, the content of the catalytic component is 1-99% by weight, and the content of the auxiliary is 1-99% by weight.

2. The method according to claim 1, characterized in that The catalyst is synthesized by a method comprising the following steps: (A) providing alumina, an auxiliary agent and a shaping agent, wherein the dry weight proportion of impurity metal elements contained in the alumina, the auxiliary agent and the shaping agent is less than 0.01% by weight; (B) mixing the alumina, the auxiliary agent and the forming agent to form a raw material mixture, and extruding, drying and sintering the raw material mixture to form a catalyst precursor; (C) fluorinating the catalyst precursor with a fluorinating agent to form the catalyst.

3. The method according to claim 2, characterized in that In step (B), the raw material mixture is kneaded and slurried before extrusion molding.

4. The method according to claim 2, characterized in that The forming agent comprises an acidic solution and a solid forming agent selected from the group consisting of methyl cellulose, ethyl cellulose, propyl cellulose, carboxymethyl cellulose, cellulose acetate butyrate, hydroxypropyl cellulose, hydroxypropyl methyl cellulose, polyether resin, polyester resin, polyvinyl chloride resin, polyethylene oxide, polypropylene oxide, polyvinyl alcohol, styrene-butadiene-styrene resin, starch, modified starch, guar gum, substituted agar, dextrin, and a combination of two or more of the solid forming agents; The concentration of the acidic solution is 0.1-8wt%; and Based on the total weight of the raw material mixture, the content of the aluminum oxide is 10-69% by weight, the content of the auxiliary agent is 10-69% by weight, the content of the acidic solution is 10-50% by weight, and the content of the solid forming agent is 0.1-20% by weight.

5. The method according to claim 2, characterized in that In step (B), the drying temperature is 70-200° C., and the drying time is 2 h to 24 h; the sintering includes sintering at a temperature range of 300-400° C. for 1-3 hours, and then sintering at a temperature range of 530-570° C. for 4-7 hours; Step (C) comprises fluorinating the catalyst precursor with a mixed gas of hydrogen fluoride and nitrogen at a temperature of 150-300° C., wherein the volume content of hydrogen fluoride in the mixed gas is 1-20 volume %.

6. The method according to claim 1, characterized in that The fluorinated alkylene oxide is selected from tetrafluoroethylene oxide, hexafluoropropylene oxide, perfluorobutylene oxide, perfluoropentane oxide, perfluorohexane oxide, perfluoroheptane oxide, perfluorooctane oxide, and combinations thereof; the carbonyl-containing product is selected from tetrafluoroacetaldehyde, hexafluoroacetone, perfluorobutanone, perfluoropentanone, perfluorohexanone, perfluoroheptanone, and perfluorooctanone.

Images