Method for treating a catalyst

Abstract

The invention relates to a method for treating a catalyst, said method comprising a hydrothermal treatment step in which the drying rate is lower than in the subsequent drying step. The catalyst can be treated according to said method, before its first use, preferably in oligomerisation, or after its use, preferably in oligomerisation.

Description

[0001] Process for treating a catalyst

[0002] The present invention relates to a process for treating a catalyst, wherein the process comprises a hydrothermal treatment step in which the drying rate is lower than in the subsequent drying step. The catalyst can be treated with the process according to the invention before its first use, preferably in the oligomerization, or after its use, preferably in the oligomerization.

[0003] There are hardly any processes in industrial chemistry that can be carried out without a catalyst. Some of the catalysts used contain nickel as the active metal, for example, in hydrogenation or oligomerization. During hydrogenation, unsaturated hydrocarbons are (partially) saturated by hydrogen bonding. During oligomerization, unsaturated hydrocarbons react with themselves, forming correspondingly longer-chain hydrocarbons, so-called oligomers (e.g., dimers, trimers, or tetramers).

[0004] It is widely known that catalysts lose activity over time when used in chemical processes. This means that important parameters such as conversion or selectivity decrease over time. However, it can also happen that freshly prepared catalysts do not exhibit sufficient activity for economic viability. The basic solution to this problem is pretreatment of a fresh catalyst or regeneration of a catalyst whose activity has decreased. Numerous corresponding processes have been published in the literature.

[0005] In large-scale processes, there is a constant challenge to improve the process. This includes improving the catalysts used and their activity in order to make the processes even more economical on a large scale.

[0006] The present invention therefore aimed to provide a process for treating a catalyst, preferably an oligomerization catalyst, with which the properties of the catalyst can be improved. Particularly when used in oligomerization, higher selectivities and higher conversions should be achieved without adversely affecting the catalyst's service life or mechanical properties such as strength.

[0007] The underlying object of the present invention has been achieved with the process for treating a catalyst according to claim 1. Preferred embodiments are specified in the subclaims. The process according to the invention is therefore a process for treating a nickel-containing catalyst, wherein the process comprises at least the following steps: a) thermal treatment of the catalyst at a temperature of 500 to 900°C to remove carbon-containing deposits; b) impregnation of the catalyst with an aqueous or ammoniacal solution comprising a nickel compound;c) hydrothermal treatment of the catalyst, wherein the hydrothermal treatment is carried out by heating the catalyst from room temperature to a temperature in the range of 75°C to 150°C, preferably 80°C to 110°C, and optionally maintaining it at that temperature until a residual moisture content of at most 30%, preferably at most 50%, is obtained; d) drying the catalyst, wherein the drying rate during the drying in step cd) is higher than during the hydrothermal treatment in step bc) and wherein the drying is carried out to a residual moisture content of at most 15%, preferably to a residual moisture content of at most 10%; and e) calcining the catalyst.

[0008] The oligomerization catalyst has a composition of 15 to 50 wt.%, preferably 15 to 40 wt.% NiO, 10 to 30 wt.% Al2O3, 55 to 70 wt.% SiO2, and 0.01 to 2.5 wt.%, preferably 0.01 to 2.5 wt.% of an alkali metal oxide, preferably sodium oxide. The figures relate to a total composition of 100 wt.%. In a particularly preferred embodiment of the present invention, the oligomerization catalyst is substantially free of titanium dioxide and / or zirconium dioxide; in particular, the oligomerization catalyst contains less than 0.5 wt.%, preferably less than 0.1 wt.%, particularly preferably less than 0.01 wt.% of titanium dioxide and / or zirconium dioxide in its total composition.

[0009] According to the invention, the oligomerization catalyst can also have a specific surface area (calculated according to BET) of 150 to 400 m 2 / g, preferably 190 to 350 m 2 / g, particularly preferably from 220 to 330 m 2 / g. The BET surface area is measured using nitrogen physisorption according to DIN-ISO 9277 (as of January 2014).

[0010] In a further preferred embodiment, the oligomerization catalyst has mesopores and macropores, i.e., it has a bimodal pore size distribution. The mesopores of the oligomerization catalyst according to the invention have an average pore diameter of 5 to 15 nm, preferably of 7 to 14 nm, particularly preferably of 9 to 13 nm. In contrast, the macropores of the oligomerization catalyst according to the invention preferably have an average pore diameter of 1 to 100 pm, particularly preferably of 2 to 50 pm. The average pore volume of the oligomerization catalyst according to the invention, ie, both the mesopores and the macropores, can be 0.5 to 1.5 cm 3 / g, preferably 0.7 to 1.3 cm 3 / g. The mean pore diameter and the mean pore volume can be determined using mercury porosimetry according to DIN 66133 (as of 1993-06).

[0011] The oligomerization catalyst according to the invention is preferably in the form of granules. Furthermore, the oligomerization catalyst according to the invention can have an average particle diameter (d50) of 0.1 mm to 7 mm, preferably 0.5 to 6 mm, particularly preferably 1 mm to 5 mm. The average particle diameter can be determined using imaging techniques, in particular by the methods specified in the standards ISO 13322-1 (as of December 1, 2004) and ISO 13322-2 (as of November 1, 2006). A suitable device for analyzing the particle diameter is, for example, the Camsizer 2006 (Retsch Technology).

[0012] In a further preferred embodiment, the oligomerization catalyst has a Bulk Crush Strength (BCS) of more than 0.5 MPa, preferably more than 0.6 MPa, and particularly preferably more than 0.8 MPa. The BCS value is a measure of the mechanical strength of mineral granules. The Bulk Crush Strength (BCS) of a solid is a parameter defined as the pressure in MPa at which 0.5 wt.% fines (i.e., particles sieved through a sieve with a mesh size of 0.425 mm) are formed when the solid sample is pressurized via a piston in a tube. For this purpose, 20 ml of the solid is pre-sieved with a sieve (mesh size: 0.425 mm), filled into a cylindrical sample tube (inner diameter: 27.6 mm, wall thickness: 5 mm, height: 50 mm) and 5 ml of steel balls (diameter: 3.9 mm) are placed on top of the solid.The solid is then subjected to varying (increasing) pressures for three minutes. The fine particles created by the pressure are then separated by sieving, weighed together, and their percentage determined. This process is continued until a fine particle content of 0.5 wt.% is reached.

[0013] An oligomerization catalyst can also be characterized by its maximum bulk density. In a preferred embodiment, the oligomerization catalyst according to the invention has a maximum bulk density of 0.1 to 2 g / cm 3 , preferably 0.2 to 1.5 g / cm 3 , particularly preferably from 0.3 to 1.0 g / cm 3The bulk density can be determined using a measuring cylinder. A specific volume of the solid to be analyzed is poured into the measuring cylinder, for example, using a suitable dosing device such as the DR100 (Retsch), and the measuring cylinder is weighed. The maximum bulk density can be determined from the weight and volume. If necessary, the residual moisture content must be subtracted from the sample weight.

[0014] The oligomerization catalyst according to the invention is prepared by a process which comprises the following generally formulated steps:

[0015] 1) Mixing the amorphous silica-alumina support material, the Al-containing and Si-free binder and at least a portion of a nickel source, optionally additionally an alkali source, and granulating the mixture thus prepared;

[0016] 2) impregnating the granulate produced in step a) with at least a portion of a nickel source and / or an alkali source, provided that the entire nickel source and / or the alkali source has not already been mixed in step a) with the silica-alumina support material and the Al-containing and Si-free binder; and

[0017] 3) Calcining the granules to produce the oligomerization catalyst.

[0018] Corresponding methods and the precise conditions are known and are disclosed, for example, in EP 3 549 669 A1, EP 3 546 065 A1 or EP 3 542 898 A1.

[0019] After the catalyst has been prepared, it can be used in the oligomerization of olefins. However, the catalyst can also be subjected to the process according to the invention after its preparation but before its first use, where the preparation steps are partially repeated but an additional hydrothermal step is also carried out. The direct preparation of a catalyst using a hydrothermal treatment step is not part of this invention.

[0020] The process according to the invention can also be used to regenerate a catalyst already used in the oligomerization process. With increasing use of the oligomerization catalyst in the oligomerization process, a decrease in conversion and / or selectivity may occur, for example, due to the deposition of organic compounds. The catalyst according to the invention can be regenerated after use in the oligomerization reaction with the catalyst according to the invention, i.e., exhibit improved oligomerization activity compared to its previous state. The individual steps are explained in more detail below:

[0021] Step a)

[0022] It is possible that the oligomerization catalyst may contain deposits of organic substances after use in oligomerization reactions. Removal of these deposits is often advisable. The removal of at least some of the organic compounds deposited in the catalyst preferably occurs in step a) by thermal treatment (oxidation), which produces carbon oxides and water. Step a) can be carried out continuously or batchwise in a furnace, for example in a rotary kiln or a shaft kiln. For this purpose, the oligomerization catalyst is fed into the furnace and preferably maintained at a predetermined furnace temperature of 500 to 900 °C, particularly preferably 600 to 850 °C. Combustion air is typically used in step a).The combustion air used is preferably supplied in countercurrent; optionally, additional air is blown into the granulate (oligomerization catalyst) via suitable inlets to ensure faster oxidation.

[0023] Step b)

[0024] In step b), the catalyst obtained from step a) is impregnated with an aqueous or ammoniacal solution. Impregnation, in the context of the present invention, means bringing the catalyst into contact with the aqueous or ammoniacal solution; for example, impregnation can be carried out by spraying until a permanent liquid film appears on the surface (incipient wetness). Impregnation introduces at least the moisture required for the subsequent hydrothermal treatment.

[0025] According to the invention, the aqueous or ammoniacal solution preferably comprises a

[0026] Nickel compound. This allows additional amounts of nickel to be deposited on the

[0027] To deposit an oligomerization catalyst, any soluble nickel compound such as nickel nitrate (Ni(NOs)2), nickel acetate (Ni(ac)2), nickel acetylacetonate (Ni(acac)2), nickel sulfate (NiSO4), or nickel carbonate (NiCOs) can be used to produce an aqueous or ammoniacal nickel solution.

[0028] The use of NiHAC solutions, i.e., ammoniacal Ni(CO3) solutions, has proven particularly advantageous. Such solutions can be used with nickel contents of 0.5 to 14 wt. %, in particular 2 to 10 wt. %, and most especially 4 to 8 wt. %. Step c)

[0029] After impregnation, a hydrothermal treatment follows in step c). The hydrothermal treatment is carried out by heating the catalyst from room temperature to a temperature in the range of 75°C to 150°C, preferably 80°C to 110°C, and optionally maintaining it at this temperature until a residual moisture content of no more than 30%, preferably no more than 50%, is achieved. The term "residual moisture" refers to the state of the catalyst prior to the hydrothermal treatment, where the catalyst has a residual moisture content of 100%. The hydrothermal treatment therefore dries the catalyst only slowly or not at all.

[0030] The hydrothermal treatment is the core of the present process and must be clearly distinguished from the subsequent drying in step d). In the hydrothermal treatment, the drying rate (mass loss of evaporable components such as water or ammonia per unit time (e.g. min)) is significantly lower than in the drying in step d). The hydrothermal treatment in step c) can be carried out at ambient pressure or at a pressure higher than ambient pressure, but not in a vacuum. The hydrothermal treatment is preferably carried out in a suitable apparatus in which the drying rate can be limited. The hydrothermal treatment in step c) can, for example, also be carried out in a closed container, whereby the drying rate relative to the volume of the container is 0. If the hydrothermal treatment is carried out in a closed container, the pressure increases due to the evaporating water and evaporating ammonia.For safety reasons, it may be necessary in this case for the closed container to have a pressure relief valve to prevent the pressure from becoming too high.

[0031] Step d)

[0032] The oligomerization catalyst will then be dried in a suitable drying apparatus, for example, a belt dryer with air flow or a conical dryer, at temperatures between 80 and 250 °C, preferably between 100 and 220 °C, and at atmospheric pressure or even under vacuum. The drying rate is higher during the drying in step d) than during the hydrothermal treatment in step c). In a preferred embodiment, the drying apparatus and the apparatus for the hydrothermal treatment are not identical. Instead, the incompletely dried oligomerization catalyst can be removed from the apparatus in which step c is carried out and introduced into the drying apparatus.

[0033] Step e)

[0034] Step e) is the final calcination. The calcination of the oligomerization catalyst can be carried out continuously or discontinuously in a suitable furnace, such as a shaft furnace or rotary kiln. In continuous calcination, a gas is preferably passed countercurrently through the oligomerization catalyst (granules). The gas used can be air, nitrogen, or a mixture thereof. The gas flow can be 0.2 to 4 m 3 Gas per kg of granulate per hour, and the gas inlet temperature should be between 400 and 900 °C, preferably between 450 and 750 °C. In addition to the heat introduced by the gas, energy can be introduced by actively heating the furnace walls.

[0035] The calcination temperature in the furnace can be 400 to 900 °C, preferably 450 to 850 °C. This temperature can be maintained for several hours, preferably 0.5 to 20 hours, particularly preferably 1 to 10 hours, before the granules are cooled. Cooling preferably takes place in an air stream.

[0036] The oligomerization catalyst according to the invention or the catalyst prepared or regenerated by the process according to the invention can be used in particular for the oligomerization of C3 to C6 olefins, preferably C3 to C5 olefins, particularly preferably C4 olefins, or olefin-containing feed mixtures based thereon. The olefins or olefin-containing feed mixtures are used as the reactant stream.

[0037] After carrying out the process according to the invention, the catalyst can be used for the oligomerization of olefins. The present invention therefore also provides a process for the oligomerization of C3 to C6 olefins, wherein an olefin-containing feed mixture containing the C3 to C6 olefins is passed over a catalyst in at least one reaction zone, the catalyst having been subjected to a treatment according to the process according to the invention.

[0038] The olefins used in the process according to the invention are C3 to C6 olefins, preferably C3 to C5 olefins, particularly preferably C4 olefins or olefin-containing feed mixtures based thereon, which may also contain proportions of analogous alkanes. Suitable olefins include α-olefins, n-olefins, and cycloalkenes. The olefins used as reactants are preferably n-olefins. In a particularly preferred embodiment, the olefin is n-butene. The term "olefin-containing feed mixtures based thereon" is to be understood according to the invention to refer to any type of mixture containing the corresponding C3 to C6 olefins to be oligomerized in an amount that enables the oligomerization to be carried out. The olefin-containing feed mixtures preferably contain virtually no other unsaturated compounds and polyunsaturated compounds such as dienes or acetylene derivatives.Preference is given to using olefin-containing feed mixtures which contain less than 5% by weight, in particular less than 2% by weight, of branched olefins, based on the olefin content. Further preference is given to using olefin-containing feed mixtures which contain less than 2% by weight of branched olefins, in particular isoolefins. Propylene (C3) is produced industrially by cracking naphtha and is a readily available commodity chemical. C5 olefins are present in light naphtha fractions from refineries or crackers. Industrial mixtures containing linear C4 olefins are light naphtha fractions from refineries, C4 fractions from FC or steam crackers, mixtures from Fischer-Tropsch syntheses, mixtures from the dehydrogenation of butanes, and mixtures formed by metathesis or from other industrial processes. For example, mixtures of linear butenes suitable for the process according to the invention can be obtained from the C4 fraction of a steam cracker.In the first step, butadiene is removed. This occurs either by extraction or extractive distillation of the butadiene or its selective hydrogenation. In both cases, a virtually butadiene-free C4 fraction is obtained, raffinate I. In the second step, isobutene is removed from the C4 stream, e.g., by producing methyl tert-butyl ether (MTBE) by reaction with methanol. Other possibilities include reacting the isobutene from raffinate I with water to form tert-butanol or acid-catalyzed oligomerization of isobutene to form diisobutene. The now isobutene-free C4 fraction, raffinate II, contains the linear butenes and optionally butanes as desired. Optionally, the 1-butene can also be separated by distillation. Both fractions, the one containing 1-butene or the one containing 2-butene, can be used in the process according to the invention.

[0039] In a further preferred embodiment, C4-olefin-containing streams are fed to the process as olefin-containing feed mixtures. Suitable olefin-containing feed mixtures include raffinate I (butadiene-free C4 fraction from the steam cracker) and raffinate II (butadiene- and isobutene-free C4 fraction from the steam cracker).

[0040] Another possibility for producing a suitable olefin-containing feed mixture is to hydroisomerize raffinate I, raffinate II, or a similarly composed hydrocarbon mixture in a reactive column. This can yield, among other things, a mixture consisting of 2-butenes, small amounts of 1-butene, and optionally n-butane, as well as isobutane and isobutene.

[0041] The oligomerization is generally carried out at a temperature in the range of 50 to 200 °C, preferably 60 to 180 °C, more preferably in the range of 60 to 130 °C, and at a pressure of 10 to 70 bar, preferably 20 to 55 bar. If the oligomerization is to take place in the liquid phase, the pressure and temperature parameters must be selected such that the reactant stream (the olefins or olefin-containing feed mixtures used) is in the liquid phase. The weight-based space velocities (reactant mass per catalyst mass per time; weight hourly space velocity (WHSV)) of the olefin-containing feed mixture are in the range between 1 g of reactant per g of catalyst and per h (= 1 h -1 ) and 190 h -1 , preferably between 2 h' 1 and 35 hours -1 , particularly preferably between 3 h -1 and 25 hours -1 . However, the typical conditions are also known to the expert.

[0042] The oligomers produced by the process according to the invention are used, among other things, for the production of aldehydes, alcohols, and carboxylic acids. For example, the dimer of linear butenes yields a nonanal mixture by hydroformylation. This yields the corresponding carboxylic acids either by oxidation or a C9 alcohol mixture by hydrogenation. The C8 acid mixture can be used to produce lubricants or driers. The C8 alcohol mixture is a precursor for the production of plasticizers, in particular di-isoonyl phthalates, di-isononyl terephthalates, di-isononyl-1,4-cyclohexanedicarboxylic acid esters, or di-isononyl-1,2-cyclohexanedicarboxylic acid esters.

[0043] The present invention is explained in more detail below using examples. Alternative embodiments of the present invention are obtainable in an analogous manner.

[0044] Examples:

[0045] Original catalyst material

[0046] The catalyst material originates from a production plant for the oligomerization of butenes, with a typical composition of approximately 20 wt.% NiO on AhOVSiOg. The used catalyst material is first regenerated by thermally treating the catalyst material in a rotary kiln at temperatures between 550 and 650 °C in a second step, re-impregnating it with a 5% Ni solution in a second step, drying it in a drying oven at approximately 110 to 120 °C for more than 10 hours to a residual moisture content of approximately 15%, and then calcining it at 650 °C in a split-tube furnace. No additional hydrothermal treatment was performed for comparative catalyst 2. To produce catalyst 1 according to the invention, a further hydrothermal treatment was performed prior to drying in the drying oven.The material was hydrothermally treated in a partially opened container (sealed with a vented screw cap with a PTFE membrane) for 6 hours at 110 °C in a drying cabinet until a residual moisture content of approximately 30% was reached. The drying rate was higher during the subsequent drying process. The two catalysts prepared in this way were used for catalytic testing as follows.

[0047] Approximately 350 g of catalyst were charged into each metal tube with an inner diameter of 21 mm. Glass beads with a diameter of 2 mm were placed upstream and downstream of the catalyst to serve as preheating and cooling phases, respectively. The oligomerization was carried out using a feed stream at 30 bar and a space velocity of 2 g / h of butene per gram of catalyst, with the reaction temperature varying between 80 °C and 100 °C. The products were analyzed by gas chromatography for butene conversion and octene linearity. The compositions of the feed stream for the oligomerization are shown in Table 1 below.

[0048] Table 1 : Composition of the feed stream

[0049] The conversions achieved for the feed stream as a function of temperature for catalyst 1 (according to the invention) and catalyst 2 (not according to the invention), as well as the resulting ISO indices, are given in Table 2.

[0050] The linearity of an oligomerization product or of the resulting dimers is described by the ISO index, which represents the average number of methyl branches in the dimer. For example, (for butene as the reactant) n-octenes contribute 0, methylheptenes 1, and dimethylhexenes 2 to the ISO index of a C8 fraction. The lower the ISO index, the more linear the molecules in the respective fraction are.

[0051] The ISO index is calculated using the following general formula:

[0052] (singly branched dimers (wt%) + 2 x doubly branched dimers (wt%)) 1ÖÖ

[0053] Accordingly, a dimer mixture with an ISO index of 1.0 has, on average, exactly one methyl branch per dimer molecule. The proportion of the individual isomers can be determined, for example, using gas chromatography.

[0054] Table 2: Catalyst results It is shown that the inventive catalyst 1 delivers significantly higher conversions at comparable or lower ISO indices. This is surprising in that higher conversion is often associated with lower linearity of the oligomers in the product mixture. The additional hydrothermal treatment therefore ensures increased catalyst effectiveness, regardless of temperature.

Claims

AMENDED CLAIMS received by the International Bureau on November 13, 2023 (13.11.2023). A process for treating a nickel-containing catalyst, the process comprising at least the following steps: a) thermal treatment of the catalyst at a temperature of 500 to 900 °C to remove carbon-containing deposits; b) impregnation of the catalyst with an aqueous or ammoniacal solution comprising a nickel compound; c) hydrothermal treatment of the catalyst, the hydrothermal treatment being carried out by heating the catalyst from room temperature to a temperature in the range of 75 °C to 150 °C, preferably 80 °C to 110 °C and optionally holding it at that temperature until a residual moisture content of at most 30%, preferably of at most 50%, is obtained, the hydrothermal treatment being carried out at a pressure higher than ambient pressure;d) drying the catalyst, wherein the drying rate during the drying in step d) is higher than during the hydrothermal treatment in step c) and wherein the drying is carried out to a residual moisture content of not more than 15%, preferably to a residual moisture content of not more than 10%;and e) calcining the catalyst. . Process according to claim 1, wherein the treatment process takes place following the preparation of the catalyst or for regeneration after use in a heterogeneously catalyzed reaction, preferably an oligomerization. . Process according to claim 1, wherein the nickel compound is selected from the group consisting of nickel nitrate (Ni(NOs)2), nickel acetate (Ni(ac)2), nickel acetylacetonate (Ni(acac)2), nickel sulfate (NiSO4), nickel citrate or nickel carbonate (NiCO3). . Process according to claim 4, wherein the aqueous or ammoniacal solution is an ammoniacal Ni(CO3) solution. . Process according to one of the preceding claims, wherein the thermal treatment in step a) takes place at a temperature of 600 to 850 °C.; AMENDED SHEET (ARTICLE 19) 6. A process according to any one of the preceding claims, wherein the duration of hydrothermal treatment in step c) is 1 to 24 hours.

7. Process according to one of the preceding claims, wherein the drying in step d) takes place at a temperature in the range from 80 to 250 °C, preferably in the range from 100 to 220 °C.

8. Process according to one of the preceding claims, wherein the drying in step d) is carried out such that the dried material obtained has a loss on drying at 110 °C (LOD) of not more than 5 wt.%.

9. A process according to any one of the preceding claims, wherein the drying rate in step d) is twice as high as in step c).

10. The process according to any one of the preceding claims, wherein the calcination in step e) is carried out at a temperature between 400 °C and 900 °C, preferably 450 °C to 850 °C.

11. A process according to any one of the preceding claims, wherein the calcination in step e) is carried out in an air stream, a nitrogen stream or a combination thereof.

12. A process according to any one of the preceding claims, wherein the catalyst has the following composition of 15 to 50 wt% NiO, 10 to 30 wt% Al2O3, 55 to 70 wt% SiO2 and 0.01 to 2.5 wt% of an alkali metal oxide.

13. A process according to any one of the preceding claims, wherein the catalyst has a specific BET surface area of ​​150 to 400 m 2 / g, determined by nitrogen physisorption.

14. A process for the oligomerization of C3 to C6 olefins, wherein an olefin-containing feed mixture containing the C3 to C6 olefins is passed over a catalyst in at least one reaction zone, the catalyst having been subjected to a treatment according to any one of claims 1 to 14. AMENDED SHEET (ARTICLE 19)

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