Method for regenerating hydrogenation catalysts

Abstract

To provide a process for regenerating a catalyst used for the ring hydrogenation of an aromatic species, especially an aromatic ester.SOLUTION: The present invention discloses a process for regenerating a catalyst used for the ring hydrogenation of an aromatic species in at least one reactor, wherein the regeneration is conducted by passing a gas stream having an oxygen content of 100 to 20,000 ppm, over the catalyst to be regenerated; at a temperature of 15 to 170°C; and without removing the catalyst from the at least one reactor.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for regenerating a catalyst used for the ring hydrogenation of aromatic chemicals, particularly aromatic esters, and uses a gas stream containing a specific amount of oxygen for the regeneration.

Background Art

[0002] The hydrogenation of aromatics, particularly aromatic esters, is known to hydrogenate the aromatic ring, which is also referred to as ring hydrogenation. In such ring hydrogenation, for example, a transition metal-containing catalyst is used. Suitable catalysts are known to those skilled in the art. The corresponding hydrogenation method is also used on an industrial scale.

[0003] As the ring hydrogenation proceeds for a long time, the activity of the catalyst used may be lost due to blocking, disappearance or poisoning of the active sites of the catalyst. When the activity is significantly reduced and the hydrogenation treatment process cannot be operated sufficiently and economically, it is necessary to increase the activity of the catalyst. This is done by a regeneration process to remove deposits and adherents on the catalyst. Here, calcination of the catalyst to remove deposits at a high temperature (200 °C or higher) can be performed, but this may be a problem for certain catalysts and is also a purely energy-related problem due to the high temperature.

[0004] The catalyst can alternatively be regenerated by passing a gas stream over it, by which deposits are transported and removed. Such a method for regenerating a ruthenium catalyst is described, for example, in Patent Document 1. The feature of the regeneration method disclosed in that document is to purge the catalyst with an inert gas until the activity of the catalyst is partially or completely restored. As a reason for the regeneration function regarding benzene hydrogenation described in that document, removal of water, that is, drying of the catalyst, can be cited.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

[0006] However, known methods have a problem in that the regeneration effect may be too low, especially when water is not the only substance that needs to be removed from the catalyst, or when water and other substances that reduce hydrogenation activity are also present on the catalyst.

[0007] Therefore, the problem to be solved by the present invention is to provide a method for regenerating catalysts used in the ring hydrogenation of aromatics, particularly aromatic esters, thereby enabling the achievement of acceptable activity more effectively and quickly. [Means for solving the problem]

[0008] The problem is solved by the method described in claim 1. Preferred embodiments are specified in the dependent claims. The method relating to the present invention is a method for regenerating a catalyst used for the cyclhydrogenation of aromatics in at least one reactor, wherein the regeneration is as follows: - Pass a gas stream with an oxygen content of 100 ppm to 20,000 ppm over the catalyst to be regenerated; At temperatures of -15 to 170°C; and - The catalyst is not removed from the at least one reactor; It will be done in this manner.

[0009] The method of the present invention can achieve advantageous regeneration of the hydrogenation catalyst because a small amount of oxygen is present in the gaseous flow that serves as the regeneration medium. The catalytic activity is improved by regeneration, and this can be achieved even under low oxygen concentrations. The regeneration described herein allows for the restart of cyclhydride, which actually produces beneficial products, in a highly efficient and effective manner. At the same time, the considerably low oxygen concentration prevents the oxidation process from causing a significant increase in reactor temperature (locally if necessary), which could damage the catalyst or, in the worst case, the reactor.

[0010] The ring hydrogenation of aromatics, particularly aromatic esters, described herein is usually carried out in at least one reactor, meaning that the ring hydrogenation can be carried out in one or more reactors, each containing a suitable catalyst. Regeneration of the catalysts used in the present invention can be carried out in any reactor present. If multiple reactors are present, regeneration can be carried out at different times or simultaneously for each reactor, but it is preferable to regenerate all catalysts simultaneously in all reactors present.

[0011] According to the present invention, the method is suitable for all catalysts used in the cyclic hydrogenation of aromatics, particularly aromatic esters. Preferably, however, the catalyst contains at least one transition metal on the support material or contains at least one transition metal on the support material. Suitable catalysts are, however, well known to those skilled in the art and are described, for example, in International Publication No. 03 / 103830.

[0012] The transition metal of the regenerated catalyst is preferably a metal selected from the group consisting of iron, ruthenium, nickel, rhodium, platinum, palladium, and mixtures thereof. Ruthenium is a particularly preferred transition metal for catalysts used in the present invention. The content of the transition metal in the regenerated catalyst is generally 0.1 to 30% by mass. The content of ruthenium calculated as metal is preferably in the range of 0.1% to 10% by mass, particularly 0.3% to 5% by mass, and particularly 0.4% to 2.5% by mass.

[0013] The carrier material containing the transition metal is preferably selected from the group consisting of activated carbon, silicon carbide, aluminum oxide, silicon dioxide, aluminosilicate, titanium dioxide, zirconium dioxide, magnesium oxide, zinc oxide, and mixtures thereof. Preferred carrier materials are aluminum oxide, silicon dioxide, titanium dioxide, and mixtures thereof. Furthermore, these carrier materials may contain alkali metals, alkaline earth metals, and / or sulfur. In a particularly preferred embodiment of the present invention, the catalyst to be regenerated is an eggshell catalyst.

[0014] According to the present invention, the regeneration medium used is a gas stream. This gas stream preferably consists of an inert gas and oxygen, and the oxygen content of the gas stream is from 100 ppm, preferably 250 ppm, more preferably 380 ppm to 20,000 ppm, preferably 13,000 ppm, and more preferably 9,000 ppm. The inert gas may be nitrogen, helium, neon, argon, carbon dioxide, or a mixture thereof. It is particularly preferable to use nitrogen as the inert gas. In regeneration, the gas stream can pass over the catalyst in the same direction or opposite direction to the circahertile flow direction, preferably in the same direction.

[0015] If multiple hydrogenation reactors are present, the regeneration medium may be supplied only to the first reactor. In this case, the regeneration medium is also supplied from the first reactor to the downstream reactors to regenerate the catalyst. However, if multiple reactors are present, it is desirable to supply the regeneration medium to each reactor. Therefore, the regeneration medium is supplied directly to each reactor and does not first pass through the upstream reactors.

[0016] The regeneration temperature is 15-170°C, preferably 25-150°C, and more preferably 25-120°C. Importantly, there should be no catalyst burnout at high temperatures to remove impurities. The pressure during regeneration is preferably in the range of 0.5-200 bar, preferably 1-110 bar.

[0017] To sufficiently improve catalytic activity, the regeneration period described in this document depends on various factors. Examples of these factors include the nature and amount of impurities, the characteristics of the reactor (size, diameter), or the characteristics of the catalyst particles (particularly size, shape, surface area, pore structure, metal packing, and the penetration depth of the metal into the support). In a preferred embodiment of the present invention, the regeneration period is at least 24 hours. If regeneration is stopped too early, the catalyst may need to be regenerated again even though it has only been used for a relatively short period of cyclhydride.

[0018] The regeneration according to the present invention is performed on a catalyst used for the cyclic hydrogenation of aromatics. In a preferred embodiment, the regeneration according to the present invention is performed on a catalyst used for the cyclic hydrogenation of aromatic esters. The aromatic esters are preferably esters of benzenecarboxylic acids, esters of benzenedicarboxylic acids, esters of benzenetricarboxylic acids, or esters of benzenetetracarboxylic acids, preferably esters of benzenedicarboxylic acids or esters of benzenetricarboxylic acids. These include phthalic acid, isophthalic acid, terephthalic acid, and trimellitate. Benzenedicarboxylic acids, i.e., esters of phthalic acid, isophthalic acid, and terephthalic acid, are preferred. Of these, C8-C10 alkyl esters are particularly preferred, especially C8-C10 alkyl esters of phthalic acid (e.g., dioctyl phthalate, diethylhexyl phthalate, diisononyl phthalate, dipropylheptyl phthalate) or C8-C10 alkyl esters of terephthalic acid (e.g., dioctyl terephthalate, diethylhexyl terephthalate, diisononyl terephthalate, dipropylheptyl terephthalate).

[0019] Circa-hydrogenation is preferably carried out in the liquid phase. Circa-hydrogenation can be carried out continuously or discontinuously using a suspended catalyst or a bulk catalyst placed on a fixed bed. In the method of the present invention, continuous circa-hydrogenation is preferably carried out even under reaction conditions where the product / reactant phase is primarily in a liquid state on a catalyst placed on a fixed bed. Preferably, the reactor is operated as a trickle-bed reactor that can be fully or partially submerged.

[0020] When continuously performing ring hydrogenation on a catalyst disposed in a fixed bed, it is suitable to convert the catalyst to an active form before first performing the ring hydrogenation. After regeneration, this activity is not necessarily required. This activation can be carried out by reducing the catalyst with a hydrogen-containing gas according to a temperature program. In some cases, this reduction may be carried out in the presence of a liquid phase that is dripped onto the catalyst. The liquid phase may be a solvent or a hydrogenation reaction product.

[0021] Since this activation is also carried out under the reaction conditions, depending on the corresponding hydrogenation conditions, the activation may be omitted.

[0022] For ring hydrogenation, various process variations can be selected. This can be carried out adiabatically, polytropically, or substantially isothermally, i.e., usually with a temperature rise of less than 10 °C, in one step or in several steps. In the latter case, all reactors, conveniently tubular reactors, can be operated adiabatically or substantially isothermally, and one or more can be operated adiabatically and the others substantially isothermally. Alternatively, the ring hydrogenation may be carried out as a trickle bed. The reactor may also be partially or completely flooded.

[0023] Ring hydrogenation can be carried out in the liquid phase of a liquid phase / gas phase mixed phase or a three-phase reactor in co-current flow, whereby the hydrogenation gas is distributed to the liquid reactant / product stream in a manner known per se. Since the liquid distribution is uniform, the removal of the reaction heat is improved, and the space-time yield is high, the reactor preferably operates at a high liquid load of 15 to 120, particularly 25 to 80 m 2 per square meter of the cross-section of the empty reactor and per hour. When operating the reactor in a straight path, the specific catalyst load (LHSV) can be a value of 0.1 to 10 / hour. 3

[0024] Ring hydrogenation may be carried out in the absence of a solvent or, preferably, in the presence of a solvent. The solvent may be any liquid that forms a homogeneous solution with the reactants and products, is inert under the hydrogenation conditions, and can be easily separated from the product. The solvent may be a mixture of a plurality of substances and may optionally contain water.

[0025] For example, linear or cyclic ethers such as tetrahydrofuran or dioxane, and aliphatic alcohols having 1 to 13 carbon atoms in the alkyl radical can be used as the solvent. Preferably, alcohols such as isopropanol, n-butanol, isobutanol, n-pentanol, 2-ethylhexanol, nonanol, industrial nonanol mixture, decanol, industrial decanol mixture, tridecanol, etc. may be used.

[0026] When using alcohol as the solvent, it may be appropriate to use the alcohol or a mixture thereof that would be produced when saponifying the product. Therefore, the formation of by-products due to transesterification can be suppressed. A more preferred solvent is the hydrogenation reaction product itself.

[0027] By using a solvent, the concentration of aromatics in the reactor feed can be limited, and as a result, the temperature control of the reactor is improved. As a result, side reactions can be minimized and the yield of the product can be increased. Preferably, the aromatic content in the reactor feed is 1 to 35%, particularly 5 to 25%. In a reactor operated in a circulation mode, it can be adjusted to the desired concentration range by the circulation rate (the quantitative ratio of the amount of recycled hydrogenation reaction effluent to the reactants).

[0028] The pressure range of ring hydrogenation may be 20 to 300 bar, preferably 40 to 200 bar. The temperature for hydrogenation is preferably in the range of 60°C to 200°C, particularly 80°C to 180°C.

[0029] The hydrogenation gas can be any desired hydrogen-containing gas mixture, provided it does not contain harmful amounts of catalyst poisons, such as carbon monoxide or hydrogen sulfide. The inert gas component may be, for example, nitrogen or methane. Preferably, it can be used with a purity of over 95%, and especially over 98%.

[0030] The present invention will be described below with reference to examples. These examples illustrate exemplary embodiments and should not be considered limiting. [Example 1]

[0031] Isoxic concentration In this experiment, it was necessary to first manufacture a reproducible catalyst and then regenerate it. For this purpose, diisononyl terephthalate (DINT) was continuously hydrogenated. The cyclic hydrogenation of DINT was carried out in a recirculation mode using a tubular reactor. The liquid phase (DINT and hydrogenation products) and the gas phase (hydrogen) were flowed co-currently into the circulating tubular reactor via a trickle bed. As the hydrogenation catalyst for Example 1, a commercially available ruthenium catalyst (Specialyst® 102: 1% Ru on a TiO2 support, manufactured by Evonik Operations GmbH) was used. This was diluted equally with an inert substance (TiO2) and used in a tubular reactor with an inner diameter of 40 mm and a length of 378 mm. The supply rate of DINT used for cyclic hydrogenation was always 130 g / hour, and the recirculation flow rate was 80 L / hour. The H2 level was controlled in a steady-state exhaust gas mode with an exhaust gas flow rate of 0.5 L / hour. In all cases, the experiments were conducted at a plant pressure of 100 bar and a tubular reactor temperature of 110°C. The concentration of DINT was measured by in-line Raman analysis. Over time, the DINT turnover rate decreased continuously. Regeneration was performed after approximately 3700 to 5700 hours.

[0032] Before regeneration, the circulation pump and reactant supply were stopped, and the liquid was discharged from the circulation reactor. Then, various regeneration conditions (pressure, temperature, etc.) were set, and regeneration was performed for a certain period (see Table 1). After regeneration, the recirculation pump and reactant supply were restarted, and circulatory hydrogenation was performed again in the same manner as above. To evaluate the regeneration effect, samples were taken immediately before stopping the reactant supply (DINT rotation speed before regeneration) and approximately 20 to 40 hours after restarting the reactant supply (DINT rotation speed after regeneration). The results are shown in Table 1 below.

[0033] Table 1: Experimental data for Example 1

[0034] [Table 1] Table 1 shows that neither pressure nor regeneration period has a significant impact on regeneration. [Example 2]

[0035] Different oxygen concentrations The experiment in Example 2 was conducted in a similar manner to the test in Example 1. Therefore, only the differences from the procedure in Example 1 are described below. A ruthenium catalyst containing a higher amount of Ru was used as the hydrogenation catalyst (2% Ru on the TiO2 support). The supply rate of DINT used in cyclic hydrogenation was always 180 g / hour, and hydrogenation was carried out at a temperature of 92.5°C. Unlike Example 1, in addition to temperature and pressure, the oxygen concentration was also changed during regeneration. To avoid problems (hydrogen oxy), the reactor was first inactivated with N2 before the regeneration experiment in which the O2 concentration was increased. The results are shown in Table 2.

[0036] Table 2: Experimental data for Example 2

[0037] [Table 2] Table 2 shows that regeneration was poor at very low oxygen concentrations. While regeneration occurred quickly at high oxygen concentrations, it should be noted that regeneration must be performed at low temperatures or low pressures due to the risk of catalyst calcination or combustion at high concentrations. For even higher oxygen concentrations (20,000 ppm or above), this invention is unsuitable for safety reasons.

Claims

1. 1. A method for regenerating a catalyst used in the ring hydrogenation of aromatics in at least one reactor, comprising: passing a gas stream having an oxygen content of from 100 ppm to 20,000 ppm over the catalyst to be regenerated; at a temperature of 15 to 170° C.; and The catalyst is not removed from the at least one reactor; So, how is it played?

2. The method of claim 1, wherein the oxygen content of the gas stream is between 250 ppm and 13000 ppm.

3. The method of claim 1, wherein the oxygen content of the gas stream is between 380 ppm and 9000 ppm.

4. The process according to any one of claims 1 to 3, wherein the regeneration is carried out at a temperature between 25°C and 150°C.

5. The method of claim 1, wherein the catalyst comprises at least one transition metal on a support material.

6. 6. The method of claim 5, wherein the at least one transition metal is a metal selected from the group consisting of iron, ruthenium, nickel, rhodium, platinum, palladium, and mixtures thereof.

7. 6. The method of claim 5, wherein the support material is selected from the group consisting of activated carbon, silicon carbide, aluminum oxide, silicon dioxide, aluminosilicates, titanium dioxide, zirconium dioxide, magnesium oxide, zinc oxide, and mixtures thereof.

8. The method described in any one of claims 5 to 7, wherein the catalyst is an eggshell catalyst.

9. The method according to any one of claims 1 to 8, wherein the gas stream is an inert gas, nitrogen, helium, neon, argon, carbon dioxide and mixtures thereof, having an oxygen content according to claim 1.

10. The method according to any one of claims 1 to 3, wherein the aromatic is an aromatic ester.

11. 11. The method of claim 10, wherein the aromatic ester is an ester of a benzene carboxylic acid, a benzene dicarboxylic acid, a benzene tricarboxylic acid, or a benzene tetracarboxylic acid.

12. The method of claim 11, wherein the aromatic ester is a C8 to C10 alkyl ester of phthalic acid or a C8 to C10 alkyl ester of terephthalic acid.

13. The process according to any one of claims 1 to 12, wherein the regeneration is carried out at a pressure in the range of from 0.5 to 200 bar.

14. The method according to any one of claims 1 to 13, wherein the period of regeneration is at least 24 hours.

15. 15. The process according to claim 1, wherein the gas flow during regeneration is directed over the catalyst in the same direction or counter-direction to the flow direction in the hydrogenation.