Spherical support for catalysts based on group IVb metal oxides and related manufacturing processes

Abstract

In the field of catalyst supports, as a result of the development of new processes, there is a significant demand for matrices to replace alumina and silica. The object of the present invention is to produce spherical catalysts or catalyst supports based on Group IVb metal oxides (especially titanium dioxide, zirconium dioxide or doped versions) having high purity, good sphericity and a reduced standard deviation of the measured diameter, and further, the spherical catalysts or catalyst supports must have a high porosity and BET surface area while having good mechanical properties. Spherical supports are required in many chemical processes to facilitate the process itself or simply to avoid changes in the reactor structure.

Description

Technical Field

[0001] Technical Field The present invention relates to a spherical support for a catalyst based on a Group IVb metal oxide and a manufacturing process thereof.

Background Art

[0002] Background Art In the field of catalyst carriers, with the development of new processes, the demand for matrices to replace classical ones such as alumina and silica is increasing. Of particular interest are Group IVb metal oxides that share the advantage of being fairly stable in basic or acidic reaction environments. For example, the use of anatase form titanium dioxide is already known in the Claus process and some fine chemistry synthesis processes. It can also be used as a support for impregnating noble metals (S. Bagheri et al., Hindawi Publishing Corp., The Scientific World Journal, Vol. 2014, Article ID 727496).

[0003] Catalyst carriers based on rutile form titanium are also already known in the literature (International Publication No. 2006 / 132918 A1). In addition to good chemical stability, titanium dioxide phases such as rutile or especially anatase are thought to interact with metals and provide oxygen to catalyze reactions or photochemical processes (S. Dafna et al., Molecules 2021, 26:5363).

[0004] When the reaction conditions are particularly extreme and a chemically stable support is required, zirconia, another oxide of group IVb metals, is well recognized as a suitable alternative to alumina (WO 2013 / 060628 A1) (EP 3080071 B1). In its pure form, it is mainly found as the monoclinic phase (P.D.L. Mercera et al., Appl. Catalysis 1991, 71:363), and US 2009 / 0305882 A1 also describes a procedure for preparing a catalyst support containing at least a certain proportion of tetragonal zirconia. The latter patent generally presents the idea that spherical catalyst supports can be provided as long as the composition contains a certain amount of binder (almost 1 / 3 of the "silica stabilizer") that is clearly necessary to ensure its mechanical stability (US 2009 / 0305882 A1).

[0005] The tetragonal phase is also obtained when zirconia co-precipitates with dopants such as SiO 2 , sulfates, TiO 2 , Y 2 O 3 , La 2 O 3 , CeO 2 , phosphates, CaO, etc., or when they are directly impregnated into the precursor (typically zirconium hydroxide) (WO 2010 / 101636 A2) (A.-K. Aboul-Gheit et al., Egypt. J. Chem. 2012, 55:509) (K. Shimizu et al., Catalysis Letters 1998, 54:153), and can preferably be present in the range of 1 to 15 wt%. In addition to having a high surface area, these supports also exhibit interesting acidic properties, and for this very reason, they can replace acid catalysts such as zeolites in isomerization reactions (US 10384196 B2).

[0006] On the one hand, titanium dioxide and zirconium dioxide-based supports are known to experts to be more difficult to form than, for example, alumina supports because they have a low ability to react with dispersants such as nitric acid. Furthermore, on the one hand, it is difficult to achieve good porosity and BET surface area, and on the other hand, it is still difficult to maintain sufficient mechanical properties (hardness, wear loss).

[0007] These metal oxides are typically used as coatings on some supports (C. Agrafiotis, J. Europ. Ceram. Soc. 2000, 20(7):825), or in the form of cylindrical extrudates (sometimes also having a star or three-lobed shape). Some examples of commercial products are S-7001 / ESM-271 by Eurosupport B.V. or CRS31 by Axens SA.

[0008] Compared to most inert materials that guarantee good consistency, the coated supports contain only a small amount of the desired material, but the extrudates, in most cases, have a poor compromise between porosity / surface area and mechanical properties. Wear loss is often much higher than for alumina extrusion and easily reaches values of up to 10% (ASTM D4058-96), making it difficult to use such supports in impregnation processes where large amounts of precious metals are lost.

[0009] One possible strategy to improve mechanical properties is to add inorganic binders such as silica, clay, cement, gypsum, or alumina, thus reducing the chemical purity of the material. However, by doing so, other metals may be introduced, which may have an adverse effect on the desired process.

[0010] Spherical supports are required in many chemical processes to facilitate the process or simply to avoid changes in the reactor structure.

[0011] All typical processes for producing spheres such as agglomeration, dropping, and spheroidization have some drawbacks.

[0012] In particular, the agglomeration process produces a very wide size distribution, which involves the need to select products to achieve at least approximately 20% standard deviation, but still results in high pressure loss in the reactor due to the limited void ratio.

[0013] The oil dropping process functions only with a limited number of raw materials, particularly those that can be dropped and quickly precipitate and stabilize. This process is limited to the production of spheres with a maximum diameter of about 3 mm.

[0014] Spheroidization on a reticle plate, like the agglomeration process, produces spheres with high-dimensional standard deviation, incompleteness, rejects, and generally poor mechanical consistency. Summary of the Invention Means for Solving the Problems

[0015] Description of the Invention The object of the present invention is to produce a spherical catalyst or catalyst support based on a Group IVb metal oxide (particularly titanium dioxide, zirconium dioxide or a doped version) that exhibits high purity, good sphericity and low standard deviation at the measured diameter. Furthermore, it must have high porosity and BET surface area, and at the same time good mechanical properties. Embodiments for Carrying Out the Invention

[0016] Preferred Embodiment of the Invention (Product) The diameter (measuring the horizontal and vertical dimensions of 10 randomly selected spheres using a Mitutoyo ABSOLUTE Digimatic 0~150mm Carbide OD Jaws caliper (accuracy = + / -0.02 mm, resolution = 0.01 mm)) is between 3 and 6 mm, preferably between 3.5 and 5.5 mm.

[0017] Desired standard deviation of diameter: less than 10%, preferably less than 7.5%, particularly preferably less than 5%. This is accompanied by a good void volume in the reactor (preferably more than 33%, particularly preferably more than 38%), which provides advantages, for example, in terms of pressure drop.

[0018] Porosity (determined by mercury porosimetry at a maximum pressure of 60,000 psia, a contact angle of 140°, and a surface tension of 480 dyn / cm. The equipment used is AutoPore IV by Micromeritics): minimum 0.20 ml / g, preferably at least 0.25 ml / g, more preferably minimum 0.30 ml / g.

[0019] BET surface area (after degassing the sample at 300 °C for 2 hours, the surface is measured by the Brunauer - Emmet - Teller method using a Micromeritics TriStar II 3020 model instrument): for rutile, minimum 25 m 2 / g, minimum 50 m 2 / g, preferably at least 75 m 2 / g, particularly preferably more than 90 m 2 / g.

[0020] Hardness (the breaking strength of 10 randomly selected spheres is measured with a Dr. Schleuniger TABLET TESTER 8M instrument, and then the average value is calculated): minimum 35 N, preferably at least 50 N, particularly preferably more than 70 N.

[0021] Purity of the active ingredient: minimum 95%, preferably more than 97.5%, more preferably more than 98.0%, even more preferably more than 98.5%, particularly preferably more than 99%.

[0022] Wear loss (ASTM D4058 - 96): preferably less than 8%, more preferably less than 5%. For TiO 2 (rutile) - based materials, preferably less than 3%, particularly preferably less than 2%.

[0023] Heap void ratio (as the ratio of void volume to total volume, or more precisely, determined as follows)

[0024]

Number

[0025] (wherein the heap density corresponds to the tap density value, the geometric density is calculated directly as the ratio of mass to the calculated volume of the sphere, and the apparent density is determined instead by the Archimedes method): preferably greater than 0.3, more preferably greater than 0.38, and particularly preferably greater than 0.40.

[0026] Preferred embodiments (processes) of the present invention The support is manufactured by a process comprising the following steps.

[0027] (a) Producing a pure or doped raw material in powder form by a wet chemical process, such as precipitation and subsequent spray drying or flame spraying, etc. This may also include an impregnation step with a dopant.

[0028] (b) Mixing the powder with an additive to improve the rheological behavior during extrusion. (c) Extruding the support at a diameter contained between 0 and 20%, preferably between 5 and 15%, smaller than the desired diameter of the green spheres.

[0029] (d) Optionally, pre-cutting the extrudate to a length contained between 80 and 800 mm, preferably between 120 and 500 mm, to facilitate the next step.

[0030] (e) Cutting the extrudate to a length approximately the same as the diameter (less than 20%, preferably less than 10%, more preferably less than 5%) that can be combined in a single pass with the subsequent rolling step, depending on the type of apparatus used.

[0031] (f) Rolling the cylindrical extrudate into a spherical shape using a dedicated apparatus. (g) Selection process (optional).

[0032] (h) Drying of the material (optional). (i) A step of firing the material at a sufficiently high temperature so as to remove an amount of additive that is preferably more than 90%, more preferably more than 95%, and particularly preferably more than 99%.

[0033] Details regarding the material and process, including descriptions of preferred ones Details of the preceding points: (a) These raw materials are commercially available. The titanium dioxide precursor material is preferably pure anatase or rutile (minimum purity 95%, preferably less than 97.5%, more preferably less than 98.5%, particularly preferably less than 99%) or a coprecipitate of oxides, or respective hydroxides or oxyhydrates with or without dopant elements such as Al, Si, Zr, and has a minimum desired TiO 2 content of 85%. Preferably, the surface area of anatase is at least 100 m 2 / g, and the surface area of rutile is at least 30 m 2 / g. The zirconium dioxide precursor is preferably pure zirconia (the above purity, surface area, preferably at least 80 m 2 / g, particularly preferably a minimum of 90 m 2 / g), a coprecipitated zirconium compound (e.g., W-, Ca-, Y-, Ce-, Si-, Ti-, lanthanum salts or organometallic compounds), or a zirconium precursor pre-doped with, for example, sulfates or phosphates, and has a preferred minimum ZrO 2 content of 85%. The starting materials can be obtained by precipitation or by some spray drying processes or similar methods. The water content is preferably between 1 and 20%, particularly preferably less than 6%.

[0034] (b) When used, the inorganic binder is introduced in an amount of less than 5%, preferably less than 1%. In particular, it is preferred not to add other oxides or silicates or their precursors (in the form of hydroxides or oxyhydrates). Extrusion additives typically used are graphite, starch, cellulose, petrolatum, wax, or chemically modified types of starch.

[0035] (c) The extruder can be continuous (e.g., a screw extruder) or discontinuous (e.g., a piston extruder) with single or multiple outputs. The preferred version is single-output extrusion. It is preferred to extrude a length of at least 5 times the diameter of the extrudate before making the first cut. In particular, the extrudate is cut into multiple pieces simultaneously.

[0036] (d) Cutting can be done by a blade or wire. Alternatively, the rolling device may have a cutting edge that cuts directly before the rolling process (single-pass process).

[0037] (e) During the spheronization process (U.S. Patent Application Publication No. 2335294 A) (U.S. Patent Application Publication No. 2593469 A) (U.S. Patent Application Publication No. 3104502 A) (U.S. Patent Application Publication No. 3791083 A) (U.S. Patent Application Publication No. 3847000 A) (International Publication No. 200426529 A1), a force preferably between 1 and 20 N is applied to the mixture.

[0038] (f) A selective process for removing poorly formed spheres (e.g., the leading and trailing parts of preliminary and non-preliminary cuts). Preferably, these can be reused in step (b) or (c).

[0039] (g) Drying is preferably carried out using an air stream at a temperature between 80 and 330 °C, more preferably between 90 and 130 °C. Drying can be done in a static dryer and a continuous dryer.

[0040] (h) The firing is preferably carried out at a temperature included between 330 °C and 1100 °C, more preferably included between 400 °C and 650 °C, even more preferably included between 500 °C and 600 °C. The size of the obtained fired spheres is generally about 15 - 30% smaller than the untreated size.

[0041] After the above steps, before final packaging, there is usually another control process such as screening to remove small particles and defective spheres. However, the yield of the desired fraction selection process is typically over 90%, more preferably over 95%, even more preferably over 98%.

[0042] Conclusion regarding the advantages achieved The spheres obtained from the manufacturing process generally not only have promising properties but also exhibit mechanical properties comparable to and sometimes superior to those of commercially available cylindrical extrudates with similar porosity / BET surface area and dimensions / volume.

[0043] These spherical supports are usually used for the preparation of catalysts by impregnation with noble metals. The catalytic active material preferably contains at least one metal from the platinum group, even more preferably a metal compound from the platinum group (e.g., chloride, nitrate or nitrosyl nitrate) used in an impregnation process (preferably dried, i.e., with 100% absorption of the solution by the support) and then converted to the final metal form or metal oxide by heat and / or chemical treatment. The content of the metal or oxide of the platinum group (in terms of metal) is preferably less than 1%, particularly preferably less than 0.5%.

Examples

[0044] Further examples

[0045]

Table 1

Claims

1. A spherical support for a catalyst based on a Group IVb metal oxide, comprising a Group IVb metal oxide, having a diameter included between 3 and 6 mm, a purity of 95% or more, a porosity of 0.25 ml Hg / g or more, 30 m ２ / g or more of BET specific surface area, an average hardness value of 35 N or more measured with 10 spheres, and a wear loss of 8% or less measured according to ASTM D4058-96, the spherical support for a catalyst based on a Group IVb metal oxide, characterized by having the above properties.

2. 50 m ２ Pure anatase having a BET of 50 m2 / g or more and 30 m2 / g ２ / g having a minimum BET, having a diameter included between 3 and 6 mm, a purity of 95% or more, a porosity of 0.25 ml Hg / g or more, an average hardness value of 35 N or more measured with 10 spheres, and a wear loss of 8% or less measured according to ASTM D4058-96, the spherical support according to claim 1, characterized in that it is composed of a type of titanium oxide derived from a raw material selected from pure rutile

3. Composed of zirconium oxide, having a diameter included between 3 and 6 mm, a purity of 95% or more, a porosity of 0.25 ml Hg / g or more, 50 m ２ / g or more of BET, an average hardness value of 35 N or more measured with 10 spheres, and a wear loss of 8% or less measured in accordance with ASTM D4058-96, the spherical support according to claim 1.

4. Obtained by using a precursor produced by a coprecipitation or impregnation process, doped zirconia selected from the group of Zr - Al, Zr - Ca, Zr - Ce, Zr - sulfate, Zr - phosphate, Zr - Y, Zr - B, Zr - Ca, Zr - Si, Zr - Ge, Zr - Ga or a plurality of such dopants of the aforementioned selection, having a diameter included between 3 and 6 mm, a purity of 95% or more, a porosity of 0.25 ml Hg / g or more, 50 m ２ / g or more of BET, an average hardness value of 35 N or more measured with 10 spheres, and a wear loss of 8% or less measured according to ASTM D4058 - 96, the spherical support according to claim 1, characterized in that it has the above properties.

5. The spherical support for a catalyst according to at least one of the preceding claims, wherein the standard deviation of the diameter of the spherical support is less than 7.5%.

6. The spherical support according to at least one of the preceding claims, i.e., having a diameter included between 3 and 6 mm, a purity of 95% or more, a porosity of 0.25 ml Hg / g or more, a BET of 30 m ２ / g or more, an average hardness value of 35 N or more measured with 10 spheres, and a wear loss of 8% or less measured in accordance with ASTM D4058-96, and the following manufacturing process, - a step of mixing a powder of the pure or doped Group IVb metal oxide with water and an additive until a pasty mass is obtained; - a step of extruding the pasty mass having a cylindrical shape; - a step of cutting the extrudate having a cylindrical shape to produce an extruded portion having a cylindrical shape; - a step of rolling the cylindrical extruded portions to make them spherical; - a step of drying the material; - a step of firing the material; A process for producing a spherical support composed of a Group IVb metal oxide, which is produced according to the following steps:

7. Use of the spherical support according to any one of Claims 1 to 5 and obtained according to the process of Claim 6 as a support for an active compound containing a platinum group metal (or metal oxide).

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