Mechanically robust large-PORE alumina-based catalyst support material and method for its preparation

Abstract

The present invention relates to a method for producing a precursor alumina obtained from a mixed aqueous dispersion of at least two different boehmites having different crystallite sizes as measured along the 021 and the 020 direction. The precursor alumina so obtained may be calcined to obtain an alumina support. According to a further aspect of the invention, the alumina support may be treated with a modifying agent, dried, and calcined to obtain a modified alumina support. The modifying agent may be one or more compounds containing Si, Ti, a transition element, or a rare-earth element. A further aspect of the invention is the alumina support precursor, the alumina support, or the modified alumina support obtainable by the method described above and / or with certain characteristics.

Description

[0001] MECHANICALLY ROBUST LARGE-PORE ALUMINA-BASED CATALYST SUPPORT MATERIAL AND METHOD FOR ITS PREPARATION

[0002] The present invention concerns methods for producing a precursor alumina, an alumina support, and a modified alumina support. Further aspects of the invention concern an alumina support precursor, an alumina support, and a modified alumina support.

[0003] Background art

[0004] Transition aluminas are used as carrier materials for heterogeneous catalysts. These aluminas are obtained by calcination of alumina monohydrates, like boehmite and pseudoboehmite, or of alumina trihydrates, like gibbsite or bayerite. In particular, boehmite and pseudoboehmite are obtained by precipitation of acidic and basic aluminum salts or by hydrolysis of aluminum alkoxides. The advantage of the hydrolysis of alkoxides, as described for example in DE 1258854 B, is that boehmite and pseudoboehmite with a very high purity are obtained.

[0005] When boehmites and pseudoboehmites obtained by the hydrolysis of aluminum alkoxides are calcined, transition aluminas having a mean pore radius of 2 to 4 nm may be obtained. These aluminas may be used as catalyst carriers for some catalytic reactions. However, it is particularly desirable that such aluminas are obtained with a pore volume or with pore radii in a specific range. It is particularly desirable to increase the pore volume and also to increase the pore radius while maintaining a very narrow pore radius distribution. For this reason, US 5055019 teaches ageing a boehmitic or pseudoboehmitic alumina dispersion obtained by neutral aluminum alkoxide hydrolysis in an autoclave having a steam pressure of 1 to 30 bar at a temperature of 100° to 235°C for between 0,5 and 20 hours. By this process boehmitic or pseudoboehmitic aluminas are obtained which can be calcined to transition aluminas having average pore radii in the range between 2 and 300 nm.

[0006] The manufacturing of liquid fuels from mixtures of hydrogen and carbon monoxide by the Fischer-Tropsch synthesis is a very important heterogeneously catalyzed process. As described in EP 1432778 B2 modified and unmodified SASOL products PURALOX SCCa 2 / 150 and SIRALOX 1,5 are preferred catalyst supports for the slurry phase process having good resistance against attrition, abrasion and dissolution. These properties can be further improved by the addition of modifying agents according to EP 2790831 B1. The average pore diameter of these catalyst carriers is in the preferred range between 10 and 15 nm.New developments in Fischer-Tropsch catalysis require catalyst supports having larger pores while, at the same time, maintaining a high mechanical stability. For fluid bed (e.g. slurry bed) applications, good resistance against attrition is a key mechanical stability parameter. In large-pore materials cobalt crystallite sizes are usually also larger which results in a higher catalytic activity and a more favorable selectivity towards the formation of desired long-chain hydrocarbons (see for example A. Y. Khodakov, Catalysis Today 2009, 144, 251-257). Therefore, there is a need for alumina supports having larger pores. Such aluminas might be obtained using the teaching of US 5055019 A. However, these high porosity materials suffer from very low mechanical stability, in particular resistance to attrition. According to US 2006 / 0035783 A1 the addition of a peptizing agent might increase the attrition resistance of cobalt / alumina catalysts.

[0007] Other catalytic reactions carried out in fluid bed reactors include the oxidation of naphthalene to phthalic anhydride, the ammoxidation of isobutane to methacrylonitrile, the synthesis of maleic anhydride from naphtha cracker C4 fraction or from n-butane, the reaction of acetylene with acetic acid to vinyl acetate, the oxychlorination of ethylene to 1 ,2-di-chloroethane, the chlorination of methane, the reaction of phenol with methanol to cresol and 2,6-xylenol, the reaction of methanol to gasoline, the synthesis of phthalonitrile by ammoxidation of o-xylene, the synthesis of aniline by gas-phase hydrogenation of nitrobenzene, and the low-pressure synthesis of melamine from urea.

[0008] Objects of the invention

[0009] Many of these reactions using alumina supported catalysts, especially those involving larger molecules as reagents or products, are likely to benefit from larger pore sizes as better diffusion of such large molecules is to be expected.

[0010] There is therefore a need for alumina supports with larger pores and good resistance to attrition.

[0011] Summary of the Invention

[0012] According to a first aspect of the invention, there is provided a method of producing an alumina support precursor comprising alumina hydrates, the method comprising at least the following steps:providing a first boehmite having a crystallite size of between 7 and 100 nm, preferably of between 10 and 40 nm, along the 021 direction and of between 5 and 100 nm, preferably of between 5 and 40 nm, along the 020 direction;

[0013] providing a second boehmite having crystallite size below 7 nm, preferably below 5 nm, along the 021 direction and below 7 nm, preferably below 5 nm, along the 020 direction;

[0014] preparing a mixed dispersion comprising water, the first boehmite and the second boehmite, with the aluminum in the first boehmite constituting 65 to 85 wt.%, preferably 70 to 80 wt.%, of the sum of the aluminum in the first boehmite and the aluminum in the second boehmite in the mixed dispersion; and

[0015] drying the mixed dispersion to obtain the alumina support precursor.

[0016] The first boehmite and the second boehmite are characterized by the crystallite sizes along the 021 direction (perpendicular to the 021 plane) and along the 020 direction (perpendicular to the 020 plane). Boehmite with crystallite sizes equal to or smaller than 5 nm along the 020 and 021 direction may be obtained by a precipitation reaction using acidic and basic aluminum salts or preferably by the hydrolysis of aluminum alkoxides. Boehmite with larger crystallite sizes along the 020 and 021 direction may be obtained by hydrothermal ageing, for example as taught in US 5055019 or EP 1025045 B1.

[0017] Following drying and calcination in air of the first boehmite, the resulting solid preferably has an AI2O3 content higher than 99.9 wt.%, more preferably higher than 99.99 wt.%. Following drying and calcination in air of the second boehmite, the resulting solid preferably has an AI2O3 content higher than 99.9 wt.%, more preferably higher than 99.99 wt.%.

[0018] Preferably, the pH of the mixed dispersion is adjusted to values between 6 and 10, preferably between 7 and 9, using a base. The pH is measured at 25 °C. The base may comprise alkali or alkali earth hydroxides, ammonia or nitrogen containing organic molecules like amines, hydroxylamines, urea or urotropine. The preferred base is ammonia.

[0019] The first boehmite may be provided as a first dispersion in water. When 100 g of the first dispersion is dried and calcined in air, between 1 and 40 g, preferably between 4 and 15 g of AI2O3 is obtained. Optionally, the first dispersion contains between 0.1 and 5 wt% (related to the total mass of the first dispersion) of an acid. An inorganic or an organic acid may be used, preferably nitric acid or acetic acid.The second boehmite may be provided as a powder. When 100 g of the powder is dried and calcined in air, preferably between 65 and 85 g of AI2O3 is obtained. Preferably, the powder contains between 0.1 and 10 wt.-% (related to the total weight of the powder), preferably between 1 and 5 wt.-%, of an acid. An inorganic or an organic acid may be used, preferably nitric or acetic acid. The mean particle size of the powder may be between 20 and 150 pm, preferably between 50 and 100 pm.

[0020] The second boehmite may be in the form of a second dispersion in water when preparing the mixed dispersion. When 100 g of the second dispersion is dried and calcined, between 1 and 40 g, preferably between 10 and 20 g of AI2O3 is obtained. Preferably the second dispersion contains between 0.1 and 5 wt.-% (related to the total weight of the second dispersion) of an acid. An inorganic acid such as nitric acid may be used. More preferably an organic acid may be used, preferably formic acid or acetic acid. The second dispersion may be wet-milled, and is preferably ball-milled as part of its preparation. Preferably the boehmite is well dispersed in the second dispersion. Addition of acids and wet-milling assists with the preparation of the second dispersion. The D50 value of the particle size distribution in the second dispersion may be between 30 and 5000 nm, preferably between 300 and 3000 nm. The D90 value of the particle size distribution in the second dispersion may be between 1000 nm and 20000 nm, preferably between 5000 and 12000 nm. By D50 and D90 are meant points in the particle size distribution obtained by laser diffraction measurements up to and including which 50% and, respectively, 90% of the total volume of the sample are contained.

[0021] Preparing the mixed dispersion may include mixing, preferably with stirrers of any shape, static mixers or screws.

[0022] The drying of the mixed dispersion may be performed using any kind of drying method, preferably contact or spray-drying, and most preferably spray-drying. The outlet temperature from the spray-drying may be between 90 and 140 °C, preferably between 100 and 120 °C.

[0023] The alumina precursor may be classified to obtain a fraction of particle sizes between 45 and 150 pm. For this classification step a sieving apparatus or an air classifier may be used.According to a second aspect of the invention, there is provided a method of producing an alumina support, the method including:

[0024] providing an alumina support precursor produced according the first aspect of the invention or performing the method hereinbefore described to produce the alumina support precursor; and

[0025] calcining the alumina support precursor at temperatures between 500 and 1400 °C, preferably between 600 and 1000 °C, for periods between 1 minute and 6 hours, preferably between 2 and 4 hours, to obtain the alumina support.

[0026] The calcination of the alumina support precursor may proceed batchwise using a muffle furnace or continuously in a rotary kiln.

[0027] According to a third aspect of the invention, there is provided a method of producing a modified alumina support, the method including:

[0028] providing an alumina support produced according to the second aspect of the invention or performing the method hereinbefore described to produce the alumina support;

[0029] modifying the alumina support by treatment with a modifying agent to form a treated alumina support;

[0030] drying the treated alumina support; and

[0031] calcining the dried treated alumina support at temperatures between 500 and 1400 °C, preferably between 600 and 1000 °C, for periods between 1 minute and 6 hours, preferably between 2 and 4 hours, to obtain the modified alumina support.

[0032] The modifying agent preferably comprises at least one compound containing Si, Ti, a transition element or a rare-earth element, more preferably a compound containing Si, and most preferably silicic acid. The modified alumina support may have a combined content of SiC>2 and / or TiC>2 of between 0.5 and 25 wt.% relative to the weight of the modified alumina support, preferably between 1 and 5 wt.%.

[0033] The treatment with a modifying agent may be done by any impregnation technique, preferably by EDF (equilibrium deposition filtration).

[0034] The drying of the treated alumina support is preferably in a belt dryer at temperatures between 50 and 200 °C, preferably between 100 and 200 °C.The calcination of the dried treated alumina support may proceed batchwise using a muffle furnace or continuously in a rotary kiln.

[0035] According to a fourth aspect of the invention there is provided an alumina support precursor comprising alumina hydrate having the following characteristics:

[0036] i. after calcination for 3h at 550 °C of the alumina support precursor, a unimodal pore diameter distribution for a pore diameter range between 1 and 100 nm obtained by mercury intrusion having its modal pore diameter between 8 and 100 nm; and ii. a ADIOhyd value smaller than 20 pm, preferably smaller than 14 pm, and most preferably smaller than 10 pm.

[0037] Preferably, substantially all of the alumina present in the aluminum support precursor is in the form of alumina hydrate. Preferably more 95 % of the aluminum in the alumina support precursor is in the form of alumina hydrate.

[0038] Preferably, the modal pore diameter is between 15 and 40 nm. As used in this specification, a pore diameter distribution is unimodal when it has a single peak, and the pore diameter at which the peak occurs is the modal pore diameter. In some embodiments, the pore diameter distribution may be unimodal for a pore diameter range between 1 and 500 nm.

[0039] Preferably the alumina support precursor has one or more, preferably all, of the following characteristics:

[0040] i. after calcination for 3h at 550 °C of the alumina support precursor, a pore volume between 0.1 and 1.2 mL / g, preferably between 0.5 and 1.0 mL / g;

[0041] ii. after calcination for 3h at 550 °C of the alumina support precursor, a surface area of between 50 and 300 m2 / g, preferably between 100 and 250 m2 / g;

[0042] iii. a LOI of between 10 and 40 wt.%, preferably between 15 and 35wt.%; and iv. a particle size distribution characterized by a D50 of between 10 and 200 pm, preferably between 50 and 100 pm, and a D10 of between 5 and 100 pm, preferably between 30 and 60 pm.

[0043] By ADIOhyd is meant a stability parameter of a material, calculated as set out below.By D10 and D50 are meant points in the particle size distribution obtained by laser diffraction measurements up to and including which 10 and, respectively, 50% of the total volume of the sample are contained.

[0044] According to a fifth aspect of the invention there is provided an alumina support comprising alumina having the following characteristics:

[0045] i. a unimodal pore diameter distribution for a pore diameter range between 1 and 100 nm obtained by mercury intrusion having its modal pore diameter between 8 and 100 nm; and

[0046] ii. a ADIOcai value smaller than 20 pm, preferably smaller than 14 pm, and most preferably smaller than 10 pm.

[0047] Preferably, the modal pore diameter is between 10 and 100 nm, more preferably between 15 and 40 nm. In some embodiments, the pore diameter distribution may be unimodal for a pore diameter range between 1 and 500 nm.

[0048] Preferably the alumina support has one or more, preferably all, of the following characteristics:

[0049] i. a pore volume between 0.1 and 1.2 mL / g, preferably between 0.5 and 1.0 mL / g; ii. a surface area of between 50 and 300 m2 / g, preferably between 50 and 250 m2 / g; iii. a LOI of between 0 and 10 wt.%, preferably between 1 and 5 wt.%; and

[0050] iv. a particle size distribution characterized by a D50 of between 10 and 200 pm, preferably between 50 and 100 pm, and a D10 of between 5 and 100 pm, preferably between 30 and 60 pm.

[0051] By ADIOcai is meant a stability parameter of a material, calculated as set out below.

[0052] The alumina support may comprise Si, Ti, a transition element or a rare-earth element, preferably Si and is then called a modified alumina support.

[0053] The modified alumina support may have a combined content of SiC>2 and / or TiC>2 of between 0.1 and 25 wt.%, preferably between 3 and 15 wt.%.

[0054] The alumina support precursor, alumina support and the modified alumina support may be obtained using the methods hereinbefore described.Analytical Methods

[0055] A typical X-ray diffraction pattern of a boehmite alumina is shown in Figure 3. The reflection at 20 = 14° is dedicated to the 020 reflection and the reflection at 20 = 28 ° is dedicated to the 021 reflection. The crystallite size along the 020 and the 021 direction is determined from line broadening according to the Scherrer formula (1):

[0056] Crystallite size = (KxAx 57,3) / (p x cos 0) (1) where:

[0057] K is the form factor: 0,992

[0058] A is the X-ray wave length: 0,154 nm

[0059] P is the line broadening at half the maximum intensity, after subtracting the instrumental line broadening

[0060] 0 is the Bragg angle

[0061] The measurements may be carried out using a Bruker CubiX3apparatus.

[0062] The surface area is determined by nitrogen physisorption according to the BET theory based on well-described methods (IIIPAC Technical Report, Pure Appl. Chem. 2015, 87, 1052-1069 and DIN ISO 9277) using for example either a Quadrasorb Si or a Quadrasorb evo instrument (Quantachrome). Alumina support precursors comprising alumina hydrate were calcined at 550°C for 3h prior to the measurements.

[0063] The pore diameter distribution and the pore volume are determined by means of mercury intrusion based on DIN ISO 15901-1 using for example an AutoPore IV 9500 porosimeter (Micromeritics). The pore volume is calculated up to a pore diameter of 500 nm. Alumina support precursors comprising alumina hydrate were calcined at 550°C for 3h prior to the measurements.

[0064] Particle size distribution measurements of dispersion in liquid are performed in a Cilas 1090 laser diffraction instrument (CILAS / France). For the measurement of powders, the sample is dispersed in isopropyl alcohol.The mechanical robustness of particles, measured herein as stability parameter AD10, can be quantified as the difference between two particle sizes determined when atomizing the particles using compressed air at two different pressures. For this, the particle size distribution may be measured using a Malvern Mastersizer 2000 laser diffraction device equipped with a Scirocco 2000 dry dispersion unit. As previously described in the literature (see e.g. EP 2790831 B1 or M. Ali, T. Bonakdar, M. Ghadiri, A. Tinke, Powder Technology 2015, 285, 138-145), the sample is atomized into the measuring cell using compressed air. Depending on the pressure used for dispersion, the shear forces acting on the sample vary. As the pressure increases, the quantity of fine particles increases as well, and hence it is possible to observe a change in the particle size distribution. As a basis value, the particle size distribution at a pressure of 0.15 bar is measured, and the D10 value at this pressure is called D10 (0.15 bar). For alumina hydrate, the particle size distribution is then measured again at a pressure of 1.0 bar, while for calcined alumina the second particle size measurement is performed at 3.0 bar. The respective D10 values are called D10 (1.0 bar) and D10 (3.0 bar), respectively. The reason for the different pressures is that calcined materials are usually more stable and higher pressures can be applied before particle breakage or attrition is observed. The stability parameter AD10 is then calculated as a difference to the basis value D10 (0.15 bar). For alumina hydrate (ADIOhyd) and calcined alumina (AD10cai) the AD10 values are calculated according to the following formulas:

[0065] ADIOhyd = D10 (0.15 bar) - D10 (1.0 bar)

[0066] ADIOcai = D10 (0.15 bar) - D10 (3.0 bar)

[0067] At a pressure of 0.15 bar, usually no fragmentation of particles occurs, and this is why particle sizes recorded at this pressure typically correspond very well to particle size distributions obtained by other methods, e.g. by using the laser diffraction method described above. However, in certain cases, the D10 (0.15 bar) value is lower than the D10 value measured by liquid dispersion methods. In those cases, the particles are unstable and already show fragmentation at very low pressures. As this might lead to misinterpretations of the stability parameter AD10 (because the difference to the D10 value at higher pressures would be smaller), any material with a D10 (0.15 bar) value smaller than the D10 value obtained by the laser diffraction method described above was labeled “not stable” and no ADIOhyd or AD10caivalue is given.The thermogravimetric determination of the loss on ignition (LOI) is carried out by heating of the sample and comparing the weight of the sample before and after. The sample is heated with a heating rate of 10 K / min up to 150 °C and then up to 950 °C with a heating rate of 20 K / min. After achieving constant weight, the sample is slowly cooled to room temperature. The LOI is then calculated using equation (2)

[0068] LOI = (m0- m95o) / mo in % (2)

[0069] mo: initial mass of the sample

[0070] m95o: mass of the sample after heating at 950°C

[0071] The loss of ignition determination may for example be done using a TGA-701 instrument from LEGO.

[0072] Elemental analysis of the samples is performed with an inductively coupled plasma optical emission spectrometer (e.g. a SPECTROBLUE from Spectro or 720-ES from Agilent). The analysis is carried out after pressure digestion in the microwave oven with addition of a mixture of nitric and phosphoric acids, and (in the case of materials produced according to the third aspect of the invention) after addition of hydrofluoric acid. Alternatively, the digestion may be carried out in a glassy carbon beaker on a magnetic stirrer hotplate at a temperature of 250 °C.

[0073] The invention will now be further described with reference to the non-limiting examples and figures in which:

[0074] Figure 1 shows the particle size distribution of Example 1 at an atomization pressure of 0.15 bar and 1.0 bar;

[0075] Figure 2 shows the pore diameter distribution and cumulative pore volume of Example 1; Figure 3 shows the XRD pattern of Example 1;

[0076] Figure 4 shows the pore diameter distribution and cumulative pore volume of Example 7; Figure 5 shows the pore diameter distribution and cumulative pore volume of Example 8; Figure 6 shows the pore diameter distribution of Examples 1, 7 and 8; and

[0077] Figure 7 shows the pore diameter distribution and cumulative pore volume of Comparative Example 7.Examples

[0078] For convenience, the phrases “crystallite size along the 021 direction of” and “crystallite size along the 020 direction of” is below shortened to “021 =” and “020 =” respectively.

[0079] Example 1

[0080] A first boehmite dispersion having an AI2O3 content of 4.9 wt% was prepared by adding DISPERAL HP14 (021 = 14.0 nm, 020 = 13.1 nm) in water with stirring. A second boehmite dispersion having an AI2O3 content of 15 wt% was prepared by adding 5.5 kg DISPERAL P2 (021 = 3.7 nm, 020 < 3.0 nm, HNO3 content in the powder: 3.9 wt%, LOI = 18.6 %) in acidic water (5 g formic acid per kg water) with stirring for at least 1 h and additional milling with a ball mill. After stirring and milling, the D50 value and the D90 value of the particle size distribution of the second boehmite dispersion was 2.3 pm and 9.5 pm respectively. The second boehmite dispersion was added to the first boehmite dispersion in a ratio of 75 wt.% aluminum of the first dispersion and 25 wt.% aluminum of the second dispersion using a propeller stirrer (speed: 80 rpm) to form a mixed dispersion. The pH value of the mixed dispersion was adjusted to 8.3 (measured at 25°C) using ammonia. This mixed dispersion was dried using a spray dryer (Niro) with an outlet temperature of 120 °C to produce an alumina support precursor.

[0081] Table 1: Analytical results for Example 1

[0082]

[0083] Note 1: Measurement performed following calcination of the alumina support precursor for 3 hours at 550 °C

[0084] Figure 2 shows the pore diameter distribution and cumulative pore volume of Example 1. The pore diameter distribution is unimodal.Example 2

[0085] A first boehmite dispersion having an AI2O3 content of 5.1 wt% was prepared by adding DISPERAL HP30 (021 = 33.1 nm, 020 = 32.2 nm) in water with stirring. A second boehmite dispersion having an AI2O3 content of 15 wt% was prepared by adding 5.5 kg DISPERAL P2 (021 = 3.7 nm, 020 < 3.0 nm, HNO3 content in the powder: 3.9 wt%, LOI = 18.6 %) in acidic water (5 g formic acid per kg water) with stirring for at least 1 h and additional milling with a ball mill. After stirring and milling, the D50 value and the D90 value of the particle size distribution of the second boehmite dispersion was comparable to Example 1 within ±1 pm. The second boehmite dispersion was added to the first boehmite dispersion in a ratio of 75 wt.% aluminum of the first dispersion and 25 wt.% aluminum of the second dispersion using a propeller stirrer (speed: 80 rpm) to form a mixed dispersion. The pH value of the mixed dispersion was adjusted to 8.3 (measured at 25 °C) using ammonia. This mixed dispersion was dried using a spray dryer (Niro) with an outlet temperature of 120 °C to produce an alumina support precursor.

[0086] Table 2: Analytical results for Example 2.

[0087]

[0088] Note 1: Measurements performed following calcination of the alumina support precursor for 3 hours at 550 °C

[0089] The pore diameter distribution for Example 2 is unimodal.

[0090] Example 3

[0091] A first boehmite dispersion having an AI2O3 content of 9.1 wt% was prepared by adding DISPERAL S (021 = 10.1 nm, 020 = 8.3 nm) in water with stirring. A second boehmite dispersion having an AI2O3 content of 15 wt% was prepared by adding 5.5 kg DISPERAL P2 (021 = 3.7 nm, 020 < 3.0 nm, HNO3 content in the powder: 3.9 wt%, LOI = 18.6 %) in acidic water (5 g formic acid per kg water) with stirring for at least 1 h and additional milling with a ball mill. After stirring and milling, the D50 value and the D90 value of the particle size distribution of the second boehmite dispersion was comparable to Example 1 within ±1 pm.The second boehmite dispersion was added to the first boehmite dispersion in a ratio of 75 wt.% aluminum of the first dispersion and 25 wt.% aluminum of the second dispersion using a propeller stirrer (speed: 80 rpm) to form a mixed dispersion. The pH value of the mixed dispersion was adjusted to 8.5 (measured at 25 °C) using ammonia. This mixed dispersion was dried using a spray dryer (Niro) with an outlet temperature of 120 °C to produce an alumina support precursor.

[0092] Table 3: Analytical results for Example 3

[0093]

[0094] Note 1: Measurements performed following calcination of the alumina support precursor for 3 hours at 550 °C

[0095] The pore diameter distribution for Example 3 is unimodal.

[0096] Example 4

[0097] A first boehmite dispersion having an AI2O3 content of 8.6 wt% was prepared by adding PLIRAL 200 (021 = 39.7 nm, 020 = 30.4 nm) in water with stirring. A second boehmite dispersion having an AI2O3 content of 15 wt% was prepared by adding 5.5 kg DISPERAL P2 (021 = 3.7 nm, 020 < 3.0 nm, HNO3 content in the powder: 3.9 wt%, LOI = 18.6 %) in acidic water (5 g formic acid per kg water) with stirring for at least 1 h and additional milling with a ball mill. After stirring and milling, the D50 value and the D90 value of the particle size distribution of the second boehmite dispersion was comparable to Example 1 within ±1 pm. The second boehmite dispersion was added to the first boehmite dispersion in a ratio of 75 wt.% aluminum of the first dispersion and 25 wt.% aluminum of the second dispersion using a propeller stirrer (speed: 80 rpm) to form a mixed dispersion. The pH value of the mixed dispersion was adjusted to 8.2 (measured at 25 °C) using ammonia. This mixed dispersion was dried using a spray dryer (Niro) with an outlet temperature of 120 °C to produce an alumina support precursor.Table 4: Analytical results for Example 4

[0098]

[0099] Note 1: Measurements performed following calcination of the alumina support precursor for 3 hours at 550 °C

[0100] The pore diameter distribution for Example 4 is unimodal.

[0101] Example 5

[0102] A first boehmite dispersion having an AI2O3 content of 4.9 wt% was prepared by adding DISPERAL HP14 (021 = 14.0 nm, 020 = 13.1 nm) in water with stirring. A second boehmite dispersion having an AI2O3 content of 15 wt% was prepared by adding 5.5 kg DISPERAL P2 (021 = 3.7 nm, 020 < 3.0 nm, HNO3 content in the powder: 3.9 wt%, LOI = 18.6 %) in acidic water (5 g formic acid per kg water) with stirring for at least 1 h and additional milling with a ball mill. After stirring and milling, the D50 value and the D90 value of the particle size distribution of the second boehmite dispersion was comparable to Example 1 within ±1 pm. The second boehmite dispersion was added to the first boehmite dispersion in a ratio of 75 wt.% aluminum of the first dispersion and 25 wt.% aluminum of the second dispersion using a propeller stirrer (speed: 80 rpm) to form a mixed dispersion. This mixed dispersion was dried using a spray dryer (Niro) with an outlet temperature of 120 °C to produce an alumina support precursor.

[0103] Table 5: Analytical results for Example 5

[0104]

[0105] Note 1: Measurements performed following calcination of the alumina support precursor for 3 hours at 550 °CThe pore diameter distribution for Example 5 is unimodal. Example 5 was prepared according to Example 1 without adjustment of the pH value of the mixed dispersion to 7 -9 using ammonia.

[0106] Example 6

[0107] A first boehmite dispersion having an AI2O3 content of 5.1 wt% was prepared by adding DISPERAL HP14 (021 = 14.0 nm, 020 = 13.1 nm) in water with stirring. A second boehmite dispersion having an AI2O3 content of 15 wt% wasprepared by adding 5.5 kg DISPERAL P2 (021 = 3.7 nm, 020 < 3.0 nm, HNO3 content in the powder: 3.9 wt%, LOI = 18.6 %) in acidic water (5 g formic acid per kg water) with stirring for at least 1 h and additional milling with a ball mill. After stirring and milling, the D50 value and the D90 value of the particle size distribution of the second boehmite dispersion was comparable to Example 1 within ±1 pm. The second boehmite dispersion was added to the first boehmite dispersion in a ratio of 75 wt.% aluminum of the first dispersion and 25 wt.% aluminum of the second dispersion using a propeller stirrer (speed: 80 rpm) to form a mixed dispersion. The pH value of the mixed dispersion was adjusted to 8.3 (measured at 25 °C) using sodium hydroxide solution. This mixed dispersion was dried using a spray drier (Niro) with an outlet temperature of 120 °C to produce an alumina support precursor.

[0108] Table 6: Analytical results for Example 6

[0109]

[0110] Note 1 : Measurements performed following ca cination of the alumina support precursor for 3 hours at 550 °C

[0111] The pore diameter distribution for Example 6 is unimodal. Example 6 was prepared according to Example 1 using sodium hydroxide solution instead of ammonia to adjust the pH value to 7 - 9.Example 7

[0112] A first boehmite dispersion having an AI2O3 content of 4.9 wt% was prepared by adding DISPERAL HP14 (021 = 14.0 nm, 020 = 13.1 nm) in water with stirring. A second boehmite dispersion having an AI2O3 content of 15 wt% was prepared by adding 5.5 kg DISPERAL P2 (021 = 3.7 nm, 020 < 3.0 nm, HNO3 content in the powder: 3.9 wt%, LOI = 18.6 %) in acidic water (5 g formic acid per kg water) with stirring for at least 1 h and additional milling with a ball mill. After stirring and milling, the D50 value and the D90 value of the particle size distribution of the second boehmite dispersion was comparable to Example 1 within ±1 pm. The second boehmite dispersion was added to the first boehmite dispersion in a ratio of 85 wt.% aluminum of the first dispersion and 15 wt.% aluminum of the second dispersion using a propeller stirrer (speed: 80 rpm) to form a mixed dispersion. The pH value of the mixed dispersion was adjusted to 8.3 (measured at 25 °C) using ammonia. This mixed dispersion was dried using a spray dryer (Niro) with an outlet temperature of 120 °C to produce an alumina support precursor.

[0113] Table 7: Analytical results for Example 7

[0114]

[0115] Note 1: Measurements performed following calcination of the alumina support precursor for 3 hours at 550 °C

[0116] Figure 4 shows the pore diameter distribution and cumulative pore volume of Example 7. The pore diameter distribution is unimodal. Example 7 was prepared according to Example 1 with the amount of aluminum from the second boehmite in the mixed dispersion reduced to 15 wt.%.

[0117] Example 8

[0118] A first boehmite dispersion having an AI2O3 content of 4.9 wt% was prepared by adding DISPERAL HP14 (021 = 14.0 nm, 020 = 13.1 nm) in water with stirring. A second boehmite dispersion having an AI2O3 content of 15 wt% was prepared by adding 5.5 kg DISPERAL P2 (021 = 3.7 nm, 020 < 3.0 nm, HNO3 content in the powder: 3.9 wt%, LOI = 18.6 %) in acidic water (5 g formic acid per kg water) with stirring for at least 1 h and additional milling with a ball mill.After stirring and milling, the D50 value and the D90 value of the particle size distribution of the second boehmite dispersion was comparable to Example 1 within ±1 pm. The second boehmite dispersion was added to the first boehmite dispersion in a ratio of 65 wt.% aluminum of the first dispersion and 35 wt.% aluminum of the second dispersion using a propeller stirrer (speed: 80 rpm) to form a mixed dispersion. The pH value of the mixed dispersion was adjusted to 8.3 (measured at 25 °C) using ammonia. This mixed dispersion was dried using a spray dryer (Niro) with an outlet temperature of 120 °C to produce an alumina support precursor.

[0119] Table 8: Analytical results for Example 8

[0120]

[0121] Note 1: Measurements performed following calcination of the alumina support precursor for 3 hours at 550 °C

[0122] Figure 5 shows the pore diameter distribution and cumulative pore volume of Example 8. The pore diameter distribution is unimodal. Example 8 was prepared according to Example 1 with the amount of aluminum from the second boehmite in the mixed dispersion increased to 35 wt.%.

[0123] The pore diameter distributions of Example 1, 7 and 8 shown in Figure 6 verify a unimodal pore diameter distribution when the aluminum from the second boehmite is between 15 wt.% to 35 wt.% of the aluminum in the mixed dispersion.

[0124] Comparative Example 1

[0125] A boehmite dispersion having an AI2O3 content of 8.7 wt% was prepared by adding PLIRAL SD65 (021 = 6.5 nm, 020 = 5.1 nm) in water with stirring. This dispersion was dried using a spray drier (Niro) with an outlet temperature of 120 °C to produce an alumina support precursor.Table 9: Analytical results for Comparative Example 1

[0126]

[0127] Note 1: Measurements performed following calcination of the alumina support precursor for 3 hours at 550 °C

[0128] Comparative Example 1 is the comparison to Example 1 without adding a second boehmite with small crystallites to a boehmite with large crystallites and without adjusting the pH of the boehmite dispersion using ammonia. Additionally, a boehmite with smaller crystallites than in Example 1 was used. The material that was prepared has a modal pore diameter below that targeted by this invention.

[0129] Comparative Example 2

[0130] A boehmite dispersion having an AI2O3 content of 4.9 wt% was prepared by adding DISPERAL HP14 (021 = 14.0 nm, 020 = 13.1 nm) in water with stirring. This dispersion was dried using a spray dryer (Niro) with an outlet temperature of 120 °C to produce an alumina support precursor.

[0131] Table 10: Analytical results for Comparative Example 2

[0132]

[0133] Note 1: Measurements performed following calcination of the alumina support precursor for 3 hours at 550 °C

[0134] Comparative Example 2 is the comparison to Example 1 without adding a second boehmite with small crystallites to a boehmite with large crystallites and without adjusting the pH of the boehmite dispersion using ammonia. The results show that a mechanically robust material is not produced in the absence of adding second boehmite with small crystallites.Comparative Example 3

[0135] A boehmite dispersion having an AI2O3 content of 5.1 wt% was prepared by adding DISPERAL HP30 (021 = 32.2 nm, 020 = 31.3 nm) in water with stirring. This dispersion was dried using a spray drier (Niro) with an outlet temperature of 120 °C to produce an alumina support precursor.

[0136] Table 11: Analytical results for Comparative Example 3

[0137]

[0138] Note 1: Measurements performed following calcination of the alumina support precursor for 3 hours at 550 °C

[0139] Comparative Example 3 is the comparison to Example 2 without adding second boehmite with small crystallites to a boehmite with large crystallites and without adjusting the pH of the boehmite dispersion using ammonia. The results show that a mechanically robust material is not produced in the absence of adding a second boehmite with small crystallites.

[0140] Comparative Example 4

[0141] A boehmite dispersion having an AI2O3 content of 8.7 wt% was prepared by adding DISPERAL S (021 = 10.8 nm, 020 = 7.4 nm) in water with stirring. This dispersion was dried using a spray dryer (Niro) with an outlet temperature of 120 °C to produce an alumina support precursor.

[0142] Table 12: Analytical results for Comparative Example 4

[0143]

[0144] Note 1: Measurements performed following calcination of the alumina support precursor for 3 hours at 550 °CComparative Example 4 is the comparison to Example 3 without adding a second boehmite with small crystallites to a boehmite with large crystallites and without adjusting the pH of the boehmite dispersion using ammonia. The results show that a mechanically robust material is not produced in the absence of adding a second boehmite with small crystallites.

[0145] Comparative Example 5

[0146] A boehmite dispersion having an AI2O3 content of 4.9 wt% was prepared by adding DISPERAL HP14 (021 = 14.0 nm, 020 = 13.1 nm) in water with stirring. The pH value of the boehmite dispersion was adjusted to 5.0 (measured at 25 °C) using formic acid. This dispersion was dried using a spray drier (Niro) with an outlet temperature of 120 °C to produce an alumina support precursor.

[0147] Table 13: Analytical results for Comparative Example 5

[0148]

[0149] Note 1: Measurements performed following calcination of the alumina support precursor for 3 hours at 550 °C

[0150] Comparative Example 5 is the comparison to Example 1 without adding a second boehmite with small crystallites to a boehmite having large crystallites and without adjusting the pH of the boehmite dispersion using ammonia. The pH value was adjusted to 5 using formic acid. The results prove that addition of a peptizing agent alone (as described in US2006 / 0035783 A1) is not sufficient to produce a mechanically robust material.

[0151] Comparative Example 6

[0152] A first boehmite dispersion having an AI2O3 content of 4.9 wt% was prepared by adding DISPERAL HP14 (021 = 14.0 nm, 020 = 13.1 nm) in water with stirring. A second boehmite dispersion having an AI2O3 content of 15 wt% was prepared by adding 5.5 kg DISPERAL P2 (021 = 3.7 nm, 020 < 3.0 nm, HNO3 content in the powder: 3.9 wt%, LOI = 18.6 %) in acidic water (5 g formic acid per kg water) with stirring for at least 1 h and additional milling with a ball mill.After stirring and milling, the D50 value and the D90 value of the particle size distribution of the second boehmite dispersion was comparable to Example 1 within ±1 pm. The second boehmite dispersion was added to the first boehmite dispersion in a ratio of 90 wt.% aluminum of the first boehmite dispersion and 10 wt.% aluminum of the second dispersion using a propeller stirrer (speed: 80 rpm) to form a mixed dispersion. The pH value of the mixed dispersion was adjusted to 8.5 (measured at 25 °C) using ammonia. This mixed dispersion was dried using a spray dryer (Niro) with an outlet temperature of 120 °C to produce an alumina support precursor.

[0153] Table 14: Analytical results for Comparative Example 6

[0154]

[0155] Note 1: Measurement performed following calcination of the alumina support precursor for 3 hours at 550 °C

[0156] Comparative Example 6 is the comparison to Example 1 with the ratio of aluminum from the second boehmite in the mixed dispersion reduced to 10 wt.%. The results prove that the ratio of at least 15 wt.% of aluminum from the second dispersion is necessary in the mixed dispersion to prepare a mechanically robust material.

[0157] Comparative Example 7

[0158] A first boehmite dispersion having an AI2O3 content of 4.9 wt% was prepared by adding DISPERAL HP14 (021 = 14.0 nm, 020 = 13.1 nm) in water with stirring. A second boehmite dispersion having an AI2O3 content of 15 wt.% was prepared by adding 5.5 kg DISPERAL P2 (021 = 3.7 nm, 020 < 3.0 nm, HNO3 content in the powder: 3.9 wt%, LOI = 18.6 %) in acidic water (5 g formic acid per kg water) with stirring for at least 1 h and additional milling with a ball mill. After stirring and milling, the D50 value and the D90 value of the particle size distribution of the second boehmite dispersion was comparable to Example 1 within ±1 pm. The second boehmite dispersion was added to the first boehmite dispersion in a ratio of 60 wt.% aluminum of the first dispersion and 40 wt.% aluminum of the second dispersion using a propeller stirrer (speed: 80 rpm) to form a mixed dispersion. The pH value of the mixed dispersion was adjusted to 8.4 (measured at 25 °C) using ammonia. This mixed dispersion was dried using a spray drier (Niro) with an outlet temperature of 120 °C to produce an alumina support precursor.Table 15: Analytical results for Comparative Example 7

[0159] >

[0160]

[0161] Note 1: Bimodal pore size distribution; second peak at 6 nm

[0162] Note 2: Measurements performed following calcination of the alumina support precursor for 3 hours at 550 °C

[0163] Figure 7 shows the pore diameter distribution and cumulative pore volume of Comparative Example 7. The pore diameter distribution is bimodal. Comparative Example 7 is the comparison to Example 1 with a ratio of aluminum from the second boehmite in the mixed dispersion increased to 40 wt.%. The material from Comparative Example 7 shows a stability comparable to the material obtained from Example 1. However, a bimodal pore diameter distribution is observed.

[0164] Comparative Example 8

[0165] Example C12 in W02006115668 was reworked. Two boehmite support materials commercially available from Sasol under the tradenames Disperal P2 and Dispal 18N4-80 were dispersed together in water and spray dried to form an alumina catalyst precursor comprising 4 wt% of the Disperal P2 and 96 wt% of the Dispal 18N4-80. The Disperal P2 had a crystallite size along the 021 direction of 3.7 nm and a crystallite size along the 020 direction of less than 3.0 nm. The Dispal 18N4-80 had a crystallite size along the 021 direction of 14 nm and a crystallite size along the 020 direction of 8 nm.

[0166] Table 16: Analytical results for Comparative Example 8

[0167]

[0168] Note 1: Measurements performed following calcination of the alumina support precursor for 3 hours at 550 °CThe pore diameter distribution for Comparative Example 8 is unimodal. Comparative Example 8 further illustrates than when aiming for larger modal pore diameters as targeted by this invention, a mechanically robust material is not produced when too low an amount of the second boehmite with small crystallites is used.

[0169] Comparative Example 9

[0170] Example C13 in W02006115668 was reworked. Two boehmite support materials commercially available from Sasol under the tradenames Disperal P2 and Dispal 23N4-80 were dispersed together in water and spray dried to form an alumina catalyst precursor comprising 4 wt% of the Disperal P2 and 96 wt% of the Dispal 23N4-80. The Disperal P2 had a crystallite size along the 021 direction of 3.7 nm and a crystallite size along the 020 direction of less than 3.0 nm. The Dispal 18N4-80 had a crystallite size along the 021 direction of 8 nm and a crystallite size along the 020 direction of 4 nm.

[0171] Table 17: Analytical results for Comparative Example 9

[0172]

[0173] Note 1: Measurements performed following calcination of the alumina support precursor for 3 hours at 550 °C

[0174] The pore diameter distribution for Comparative Example 9 is unimodal. Comparative Example 9 achieves a modal pore diameter below that targeted by this invention.

[0175] Example 9

[0176] The material produced in Example 1 was classified to obtain a fraction between 45 and 150 pm using a sieve. The classified material was calcined for 3 h at 950°C in a kiln to produce an alumina support. The calcined material was again classified to reduce the content of particles < 45 pm using a sieve.Table18: Analytical results for Example 9

[0177]

[0178] Comparative Example 10

[0179] The material from Comparative Example 2 was classified to obtain a fraction between 45 and 150 pm using a sieve. The classified material was calcined for 3 h at 950°C in a kiln to produce an alumina support. The calcined material was again classified to reduce the content of particles < 45 pm using a sieve.

[0180] Table19: Analytical results for Comparative Example 11

[0181]

[0182] Example 10

[0183] Following the procedure disclosed in EP 1432778 B2, a 45 wt.% dispersion of the calcined material from Example 9 in water was prepared and the appropriate amount of orthosilicic acid (1.0% SiC>2, obtained from ion-exchanged sodium silicate solution) was added to obtain a target SiC>2 loading of 2.0%. The mixture was stirred at 50 °C (200-300 rpm) for 3 h before filtration. The obtained powder was dried overnight at 120 °C and subsequently calcined for 1 h at 650 °C to produce a modified alumina support.

[0184] Table20: Analytical results for Example 10

[0185]

[0186] Example 11

[0187] Calcined material from Example 9 was treated as described in Example 10, but the target loading was 12% SiC>2.

[0188]

Claims

CLAIMS1. A method of producing an alumina support precursor comprising alumina hydrates, the method comprising at least the following steps:providing a first boehmite having a crystallite size along the 021 direction of between 7 and 100 nm, preferably of between 10 and 40 nm, and a crystallite size along the 020 direction of between 5 and 100 nm, preferably of between 5 and 40 nm;providing a second boehmite having a crystallite size along each of the 021 direction and the 020 direction of below 7 nm, preferably below 5 nm;preparing a mixed dispersion comprising water, the first boehmite and the second boehmite, with the aluminum in the first boehmite constituting 65 to 85 wt.-%, preferably 70 to 80 wt.-%, of the sum of the aluminum in the first boehmite and the aluminum in the second boehmite in the mixed dispersion; anddrying the mixed dispersion to obtain the alumina support precursor.

2. The method of claim 1 further comprising adjusting the pH of the mixed dispersion to values of between 6 and 10, preferably of between 7 and 9, by including a base in the mixed dispersion.

3. The method of claim 2 in which the base comprises ammonia.

4. The method of any one of claims 1 to 3 in which the first boehmite is provided dispersed in water to form a first dispersion, wherein when 100 g of the first dispersion is dried and calcined in air, between 1 and 40 g, preferably between 4 and 15 g of AI2O3 is obtained.

5. The method of any one of claims 1 to 4 in which the second boehmite is provided as a powder.

6. The method of any one of claims 1 to 4 in which the second boehmite is provided as a dispersion in water to form a second dispersion, wherein when 100 g of the second dispersion is dried and calcined in air, between 1 and 40 g, preferably between 10 and 20 g of AI2O3 is obtained, the second dispersion further containing between 0.1 and 5 wt.-% of an acid, preferably an organic acid, more preferably formic acid or acetic acid.

7. The method of claim 6 which includes wet-milling the second dispersion as part of its preparation, preferably by ball-milling.

8. The method of claim 6 or claim 7 in which the particle size distribution in the second dispersion has a D50 value of between 30 and 5000 nm, preferably between 300 and 3000 nm, and a D90 value of between 1000 nm and 20000 nm, preferably between 5000 and 12000 nm.

9. A method of producing an alumina support, the method comprising at least the following steps:the steps according to the method of any one of claims 1 to 8 to obtain the alumina support precursor; andcalcining the alumina support precursor at temperatures between 500 and 1400 °C, preferably between 600 and 1000 °C, for periods between 1 minute and 6 hours, preferably between 2 and 4 hours, to obtain the alumina support.

10. A method of producing a modified alumina support, the method comprising at least the following steps:the steps according to the method of claim 9 to obtain the alumina support; modifying the alumina support by treatment with a modifying agent to form a treated alumina support;drying the treated alumina support to form a dried alumina support; andcalcining the dried alumina support at temperatures between 500 and 1400 °C, preferably between 600 and 1000 °C, for periods between 1 minute and 6 hours, preferably between 2 and 4 hours, to obtain the modified alumina support.

11. The method of claim 10 in which the modifying agent comprises at least one compound containing Si, Ti, a transition element or a rare-earth element, preferably a compound containing Si, most preferably silicic acid.

12. The method of claim 10 or claim 11 in which the treatment with the modifying agent is performed by an impregnation technique, preferably equilibrium deposition filtration.

13. An alumina support precursor comprising alumina hydrate having the following characteristics:i) after calcination for 3h at 550 °C of the alumina support precursor, a unimodal pore diameter distribution for a pore diameter range between 1 and 100 nm obtained by mercury intrusion having its modal pore diameter between 8 and 100 nm; and ii) a ADIOhyd value smaller than 20 pm, preferably smaller than 14 pm, and most preferably smaller than 10 pm.

14. The alumina support precursor of claim 13 in which the modal pore diameter is between 15 and 40 nm.

15. The alumina support precursor of claim 13 or claim 14 having one or more, preferably all, of the following characteristics:i) after calcination for 3h at 550 °C of the alumina support precursor, a pore volume of between 0.1 and 1.2 mL / g, preferably between 0.5 and 1.0 mL / g;ii) after calcination for 3h at 550 °C of the alumina support precursor, a surface area after calcination of the alumina support precursor for 3h at 550 °C of between 50 and 300 m2 / g, preferably between 100 and 250 m2 / g;iii) a LOI of between 10 and 40 wt.%, preferably of between 15 and 35wt.%; and iv) a particle size distribution characterized by a D50 of between 10 and 200 pm, preferably of between 50 and 100 pm, and a D10 of between 5 and 100 pm, preferably of between 30 and 60 pm.

16. An alumina support comprising alumina having the following characteristics:i) a unimodal pore diameter distribution for a pore diameter range between 1 and 100 nm obtained by mercury intrusion having its modal pore diameter between 8 and 100 nm; andii) a ADIOcai value smaller than 20 pm, preferably smaller than 14 pm, and most preferably smaller than 10 pm.

17. The alumina support of claim 16 in which the modal pore diameter is between 15 and 40 nm.

18. The alumina support of claim 16 or claim 17 having one or more, preferably all, of the following characteristics:i) a pore volume of between 0.1 and 1.2 mL / g, preferably of between 0.5 and 1.0 mL / g; ii) a surface area of between 20 and 300 m2 / g, preferably of between 50 and 250 m2 / g; iii) a LOI of between 0 and 10 wt.%, preferably of between 1 and 5 wt.%; andiv) a particle size distribution characterized by a D50 of between 10 and 200 pm, preferably of between 50 and 100 pm, and a D10 of between 5 and 100 pm, preferably of between 30 and 60 pm.

19. A modified alumina support having the characteristics of any one of claims 16 to 18 and comprising Si, Ti, a transition element or a rare-earth element, preferably Si.

20. The modified alumina support of claim 19 which has a content of SiC>2 and / or TiC>2, either individually or combined, of between 0.1 and 25 wt.%, preferably of between 3 and 15 wt.%.

Images