MXPA01007729A - Nickel catalysts on transition alumina - Google Patents

Abstract

A particulate catalyst suitable for the hydrogenation of fats or oils containing 5 to 75%by weight of nickel may be made by slurrying a transition alumina powder having a surface-weighted mean diameter D[3,2]in the range 1&mgr;m to 20&mgr;m with an aqueous solution of a nickel ammine complex, followed by heating to deposit an insoluble nickel compound and then reducing the latter. Catalysts containing up to about 55%by weight of nickel have a nickel surface area above 130 m2/g of nickel. Catalysts having greater nickel contents made using alumina having an average pore diameter above 12&mgr;m may have a lower nickel surface area but are surprisingly active and selective.

Description

NICKEL CATALYSTS IN TRANSITIONAL ALUMINUM This invention relates to catalysts and in particular to catalysts suitable for use for hydrogenation, especially the hydrogenation of oils and fats. Oils and fats are often hydrogenated either partially or completely in a bulk batch suspension process by suspending a nickel catalyst in the form of oil or fat particles and feeding hydrogen thereto while the mixture is heated, typically at a temperature in the range of 80 to 250 ° C, possibly under pressure, for example, at a pressure of up to 30 bar absolute. For partial hydrogenation, the pressure is usually below 10 bar absolute, for example 2 to 4 bar absolute. For the hydrogenation of oil or grease, the catalyst must have high activity so that the desired degree of hydrogenation can be achieved in a short time and / or a small amount of nickel can be employed. The catalyst must also exhibit good selectivity in the case of partial hydrogenation so that over-hydrogenation of oils and fats is minimized. Additionally, it is desirable that the residual catalyst be easily filtered from the hydrogenated oil or fat and that the catalyst show good reuse properties. The catalysts frequently used for this process are nickel in a support of for example alumina and is characterized inter alia by a high surface area of nickel per gram of nickel. Typical catalysts having a high nickel content are described in EP 0,168,091, wherein the catalyst is made by precipitation of a nickel compound and then a soluble aluminum compound is added to the slurry of the precipitated nickel compound while the precipitate is maturing, that is, aging. After reduction of the resulting catalyst precursor, the reduced catalyst typically has a nickel surface area of the order of 90 to 150 m2 per g of total nickel. The catalysts have an atomic ratio of nickel / aluminum in the range of 2 to 10. The reduced catalysts having an atomic ratio of nickel / aluminum above 2, in which at least 70% by weight of the total nickel has been reduced to elemental nickel, they have a total nickel content of more than about 66% by weight. US-A-4191664 and US-A-4064152 disclose thermally stable nickel-alumina catalysts formed by precipitating a nickel hydroxide on a hydrated alumina powder carrier. Nickel / alumina hydrogenation catalysts, having a total nickel content of 5 to 40% by weight, but also having a high nickel surface area, made by a different route, are described in US 4,490,480. In the process of this last reference, a complex of nickel amine, particularly nickel amine carbonate, is heated in the presence of a transition alumina; this results in the precipitation of the nickel compound, such as nickel hydroxide or basic nickel carbonate, intimately associated with the alumina. In the latter process, an alumina powder with a solution of the nickel complex, or formed units, such as cylindrical spheres or extrudates, typically having a minimum dimension above about 1.5 mm, formed from the alumina, are impregnated with a solution of the nickel complex. While the catalysts have a nickel surface area of more than 130 m2 per g of total nickel, and in fact, in some cases above 200 mm2 per g of total nickel, these high surface area products are described. they are all processed by the impregnation route mentioned above, using units formed of alumina; the catalysts made by converting alumina powder into slurry, with the nickel complex they have surface areas of nickel significantly below 130 m2 per g of total nickel. While the catalysts made using the formed, preformed alumina units are useful in fixed-bed hydrogenation processes, they are unsuitable for the hydrogenation process of bulk suspension in batches, mentioned above since their size makes them reliable for sitting of the slurry and also, when used for partial hydrogenation, tend to give an over-hydrogenation of fats and oils. US 4,490,480 mentioned above indicates that suitable catalysts for slurry hydrogenation in batches can be made by grinding catalysts with high nickel surface area processed by the above impregnation route using units formed of alumina. However, the production of these catalysts by this technique comprises additional processing steps for the formation of alumina in the units formed and the subsequent step of grinding. Catalysts made directly from an alumina powder of a size of 60-70 μm containing 18-28% by weight of nickel having a nickel surface area of up to 123 m2 per g of nickel are also described in the US. 4,490,480 mentioned above. However, it has been found that these materials have a relatively poor activity for the hydrogenation of oils. It has now been found that nickel / alumina catalysts having a high activity and / or good selectivity can be made by the aforementioned process, using a slurry of the alumina powder, if an alumina powder having an alumina powder is used. small particle size. Surprisingly, despite the use of an alumina of a small particle size, the catalysts are easily filtered from the hydrogenated fat or oil. It has been proposed in GB 926,235 to make hydrogenation catalysts by this route using fossil flour as the support. However, it has been found that catalysts made using fossil flour with a small particle size, as opposed to transitional alumina, do not exhibit high surface areas of nickel.

Accordingly, there is provided a method for the preparation of a nickel / alumina catalyst containing from 5 to 75% by weight of total nickel which comprises converting a transition alumina powder having a surface-weighted average diameter to a slurry. [3,2] in the range of 1 μm to 20 μm with an aqueous solution of a nickel amine complex, heating the slurry to cause the nickel amine complex to decompose with the deposit of an insoluble nickel compound , filtering the solid residue from the aqueous medium, drying and optionally after calcining the solid residue, reducing the solid residue. By the term "total nickel" is meant the amount of nickel if it is present in elemental or combined form. However, in general, at least 70% by weight of the total nickel in the reduced catalyst will be in the elemental state. The term, weighted average diameter in surface D [3,2], otherwise called the mean diameter of Sauter is defined by M. Alderliesten in the article?, A Nomenclature for Mean Particle Diameters ", Anal. Proc., Vol 21 , May 1984, pages 167-172, and is calculated from the particle size analysis that can be conveniently performed by laser diffraction, for example, using a Malvern Mastersizer.The transition alumina can be from the gamma-alumina group, for example, an eta-alumina or chi-alumina These materials can be formed by calcination of aluminum hydroxides at 400-750 ° C and generally have a surface area of BET in the range of 150-400 m2 / g. Alternatively, the transition alumina may be from the delta-alumina group which includes high temperature forms such as delta- and theta-aluminas which may be formed by heating an alumina of the gamma group at a temperature above 800 °. C. The aluminas of the group delta generally have a surface area of BET in the range of 50-150 m2 / g. Transitional aluminas contain less than 0.5 mol of water per mole of Al203, the actual amount of water that depends on the temperature at which it has been heated. The alumina must be porous, preferably having a pore volume of at least 0.2 ml / g, particularly in the range of 0.3 to 1 ml / g. It is preferred that the alumina of small particle size have a relatively large average pore diameter since the use of these aluminas appears to give catalysts of particularly good selectivity. Preferred aluminas have an average pore diameter of at least 12 nm, particularly in the range of 15 to 30 nm. [By the term, average pore diameter is meant 4 times the pore volume as measured from the desorption branch of the nitrogen fisisor isotherm at a relative pressure of 0.98 divided by the surface area of BET]. During the production of the catalyst, the nickel compounds are deposited in the pores of the alumina, and thus the average pore diameter of the catalyst will be smaller than that of the alumina used, and decreases as the proportion of the nickel increases. It is preferred that the reduced catalysts have an average pore diameter of at least 10 nm, preferably above 15 nm and particularly in the range of 15 to 25 nm. On the other hand, despite the nickel content of the catalyst, the particle size of the catalyst is essentially the same as the particle size of the transition alumina and thus the catalysts generally have an average diameter, weighted on the surface D [3,2] in the range of 1 to 20 μm, and preferably it is less than 10 μm and particularly less than 8 μm. The catalysts of the invention contain from 5 to 75% by weight of total nickel, preferably below 70% by weight of total nickel. Catalysts containing up to 55%, preferably from 5 to 45%, by weight of total nickel, typically have a nickel surface area of greater than 130., preferably above 150, more preferably above 180, in particular above 200 m2 per gram of total nickel. Accordingly, the present invention also provides a catalyst in the form of transition nickel / alumina particles containing from 5 to 55% by weight of total nickel, having a nickel surface area of at least 130 m2 per gram of total nickel and a surface-weighted average diameter D [3,2] in the range of 1 μm to 20 μm. The nickel surface area can be determined as described in "Physical and Chemical Aspects of Adsorbents and Catalysts" edited by B.G. Linsen, Academic Press, 1970 London and New York, pages 494 and 495, and is a measure of the surface area of reduced nickel, that is, elemental, in the catalyst. It has been found that, in general, the nickel surface area of the catalysts made by the process of the invention tend to decrease as the nickel content increases. However, it has also been found that catalysts made using aluminas with a large pore size and containing relatively large amounts of nickel are surprisingly active and selective although they may not have this high nickel surface area. In this manner, useful catalysts containing at least 20% by weight of total nickel having an average pore diameter above 10 nm and a nickel surface area above 110 m2 / g of total nickel can be made using aluminas with large pore size. Accordingly, the present invention also provides a catalyst in the form of transition nickel / alumina particles containing from 20 to 75% by weight of total nickel, having a nickel surface area of at least 110 m2 per gram of total nickel , a surface-weighted average diameter D [3,2] in the range of 1 μm to 20 μm, and an average pore diameter of at least 10 nm, preferably above 12 nm, and particularly in the range of 15 to 25 nm. Catalysts containing at least 20% by weight of total nickel having a nickel surface area as low as 80 m2 / g, of total nickel appear to have good activity and selectivity with the condition that the average pore diameter is above 15 nm. Accordingly, the present invention also provides a catalyst in the form of transition nickel / alumina particles containing from 20 to 75% by weight of total nickel, having a nickel surface area of at least 80 m2 per gram of total nickel , an average diameter, weighted surface D [3,2] in the range of 1 μm to 20 μm, and an average pore diameter of at least 15 nm. The catalysts can be formed by slurrying the transition alumina powder with the appropriate amount of an aqueous solution of a nickel amine complex, for example, the product of dissolving basic nickel carbonate, in a carbonate solution of ammonium in aqueous ammonium hydroxide, to give a product of the desired nickel content. The solution of the nickel amine complex preferably has a pH in the range of 9 to 10.5. The slurry is then heated, for example, to a temperature in the range of 60 to 100 ° C, to cause the nickel amine complex to decompose with the emission of ammonia and carbon dioxide and to deposit an insoluble compound of nickel, for example, basic nickel carbonate on the surface, and in the pores, of the transition alumina. The alumina having the deposited nickel compound is then filtered from the aqueous medium and dried. Then, it can be calcined in air, for example, at a temperature in the range of 250 to 450 ° C, to decompose the deposited compound from nickel to nickel oxide. In the reduction of nickel oxide, a high surface area of nickel is generated. Alternatively, the nickel deposited compound can be directly reduced, that is, without the need for a calcination step. The reduction, if a preliminary calcination step is employed, or not, can be effected by heating a temperature in the range of 250 to 450 ° C in the presence of hydrogen. As indicated above, the catalysts are of particular utility for the hydrogenation of fats and oils, such as fish oil, soybean oil, naba oil and sunflower oil. Alternatively, the catalysts can be used for other hydrogenation reactions such as the hydrogenation of olefinic compounds, for example, waxes, nitro or nitrile groups, for example, the conversion of nitrobenzene to aniline or the conversion of nitriles to amines. They can also be used for the hydrogenation of paraffin waxes to remove traces of unsaturation in them. As indicated above, in this hydrogenation process, the necessary amount of catalyst is dispersed in a load of the oil or fat and the mixture is heated, possibly under pressure, and so much that nitrogen is introduced, for example, sprayed through the mixture. Conveniently, the catalyst is charged to the hydrogenation vessel as a concentrate of the dispersed catalyst particles in a suitable carrier medium, for example, hardened soybean oil. Preferably, the amount of catalyst in the concentrate is such that the concentrate has a total nickel content of 5 to 30%, preferably 10 to 25% by weight. Alternatively, in some cases the reduction can be done in situ. In this way, the precursor comprising the transition alumina and the unreacted nickel compound, for example, the oxide, possibly as a concentrate, i.e., dispersed in a carrier as mentioned above, can be charged to the reactor. hydrogenation with the material to be hydrogenated and the mixture is heated while hydrogen is sprayed through the mixture.

Accordingly, a catalyst precursor comprising a transition alumina and a reducible nickel compound is also provided, which when reduced with hydrogen at a temperature in the range of 250 to 450 ° C, gives a catalyst in the form of particles that they contain from 5 to 55% by weight of total nickel, which has a nickel surface area of at least 130 m2 per gram of total nickel, and an average diameter, weighted on the D surface [3,2] of 1 μm to 20 μm , preferably, less than 10 μm. Also provided is a catalyst precursor comprising a transition alumina and a reducible nickel compound, which when reduced with hydrogen at a temperature in the range of 250 to 450 ° C gives a particulate catalyst containing from 20 to 75% by weight of total nickel, having a nickel surface area of at least 80 m2 per gram of total nickel, and a surface weighted average diameter D [3,2] of 1 μm to 20 μm, preferably less than 10 μm, and an average pore diameter above 10 nm. The invention is illustrated by the following examples in which, unless otherwise specified, all percentages and parts per million (ppm) are by weight. The nickel surface areas are determined as described in the above "Physcal and Chemical Aspects of Adsorbent and Catalysts", edited by B.G. Linsen, Academic Press, 1970 London and New York, on pages 494-495 using a 1-hour reduction time.

Example 1 The alumina employed was a transition alumina of the theta-alumina type having a surface area of about 108 m2 / g and a pore volume of about 0.42 ml / g and having a weighted average surface diameter D [3.2 ] of 3.87 μm. The average pore diameter was thus approximately 16 nm. A concentrated solution containing the complex in nickel amine was obtained by dissolving, per liter of concentrated solution, 52.1 g of basic nickel carbonate (48% of Ni, 20% of C03), 37.4 g of ammonium carbonate (32.5%) of NH3, 55% of C03) and 133 g of NH3 to 30% of water. The alumina particles and enough of the concentrated solution to give approximately 33 g of nickel per 100 g of aluminas were charged to a stirred vessel equipped with a condenser. The pH of the aqueous solution was 10.2. The mixture was heated to a boil while stirring and boiling gently at about 96 ° C was maintained until the solution became clear after about 90 minutes. The solid was then completely filtered, washed and then dried with air at 120 ° C overnight. The resulting catalyst precursor, which had a nickel content of 19.6%, was then reduced by passing hydrogen through a catalyst bed while heating to 430 ° C. The reduced catalyst (designated catalyst A) had a total nickel content of 24.7% of a nickel surface area of approximately 187 m2 per g of total nickel (approximately 46 m2 per g of catalyst). The average pore diameter of the catalyst was approximately 9.5 nm and the surface area of BET was 135 m2 / g. The weighted average surface diameter of the reduced catalyst particles was similar to that of the transition alumina used.

Example 2 (comparative) A catalyst, designated catalyst B, was prepared according to the procedure of EP 0,168,091, using as the alkaline precipitation agent a solution containing 66.6 g of sodium carbonate and 25.4 g of sodium hydroxide per liter and a solution containing 35 g of nickel per liter. These two solutions were continuously fed into the precipitation vessel. Room temperature (22 ° C), an average residence time of 30 seconds and a stirring energy of 25 k / m2 were used for this precipitation. The solution leaving this precipitation vessel was continuously fed into a stabilization reactor which was maintained at 70 ° C. A solution of sodium aluminate containing 10 g of Al per liter was also fed continuously into the stabilization reactor while stirring moderately with an energy input of 2 kW / m3. The slurry leaving the second reactor was collected in a third vessel and kept at 60 ° C for five hours. The thick suspension then leaked, and washed with water at 70 ° C. The washed precipitate was converted back into slurry in water at 70 ° C and subsequently spray dried. Elemental analysis of the spray dried product gave the following composition 45.6 nickel, 4.0% aluminum, 0.02% sodium. The spray-dried product was reduced to 430 ° C in a hydrogen flow for 30 minutes and then used as the catalyst B. The nickel surface area was 115 m per g total nickel. The above preparation was repeated to give a similar catalyst, designated Catalyst C. The hydrogenation performance of the catalysts was determined by using two different oils as follows: In the first test, a soybean oil of IV 133.5 and containing 1.8 ppm of P, 1600 ppm of free fatty acids, 100 ppm of water and 0 ppm of soap and S, is used. 200 g of the oil and the required amount of reduced catalyst are charged to a hydrogenation reactor, stirred, closed. The mixture is heated to 160 ° C and the hydrogen is sprayed through the slurry under a pressure of 2 bar absolute. The hydrogenation is carried out isothermally. The amount of hydrogen absorbed in the oil is monitored and the test is determined once the amount of hydrogen required to lower the IV to 70 has been used. The hydrogenation time to reach an IV of 70 is used as a measure of the catalyst activity. In the second test, a sunflower oil of IV 132 is used and it contains 0.4 ppm of P, 800 ppm of free fatty acids, 600 ppm of water, 4 ppm of soap and 0.5 ppm of S. The hydrogenation is carried out as described above but at 120 ° C of a pressure of 4 bar absolute, and the time to reach an IV of 80 is determined. The results are shown in the following table .

It is seen that the catalyst A according to the invention was significantly more active than the comparative catalysts B and C since the hydrogenation time was decreased and / or less nickel can be used. The selectivity of the catalysts was assessed by determining the sliding melting point, the solid fat content at 10 ° C, 20 ° C, 30 ° C 35 ° C, and the content behind an isomer in the hydrogenated oils.

The filtration capacity was measured by using a normal filtration test. In this test, 170 ml of the hydrogenated oil to which 0.045 g of a filter aid (Harborlite 700) have been added, is heated at 110 ° C and maintained at a pressure of 3 absolute bars in a vessel having an output of an area of 0.5 cm2 in its background. This outlet contains an iron wire support in which a cotton cloth pre-coated with 0.02 g of the filter aid has been fixed, such that all the oil has to be filtered through the cotton cloth. The time taken for 120 g of oil to filter is used as a measure of the filtration capacity. The selectivity and filtration capacity is shown in the following table.

Example 3 The procedure of Example 1 was repeated but using an amount of the nickel amine complex solution which was about 50 g of nickel per 100 g of alumina. The reduced catalyst has a total nickel content of 33.7% and a nickel surface area of 161 m2 per g of total nickel.

Example 4 The procedure of Example 1 was repeated but using different amounts of the nickel amine carbonate solution in relation to the amount of alumina to obtain a range of catalyst precursors, hence reduced catalysts (Catalysts D, E, and F), of different nickel contents.

Example 5 The procedure of Example 4 was repeated using an alumina and a larger pore diameter. The alumina used was a transition alumina of the gamma-alumina type having a surface area of about 145 m2 / g and a pore volume of about 0.85 ml / g and having a weighted average surface diameter D [3,2] of 2.08 μm. The average pore diameter was approximately 23 nm. As in Example 4, a range of catalysts (catalysts G, H, I, J and K) of different nickel contents were produced.

The physical properties of the catalysts of Examples 4 and 5 are set forth in the following table.

The comparison of the catalysts F and K shows that while with the support of alumina with a small pore size, the incorporation of a large amount of nickel results in a low nickel surface area, the use of an alumina with a size of large pore allows catalysts having a relatively high nickel surface area to be obtained. The catalysts (with the exception of catalysts F and K) were tested as in Examples 1 and 2 and the results are shown in the following tables.

Example 6 The samples of the precursors used to make the catalysts J and K were reduced to 360 ° C instead of 430 ° C as in the previous examples to produce the catalysts L and M, respectively, and then tested as before. The nickel surface area was determined for catalyst L and found to be 114 m2 / g of total nickel, similar to that (115 m2 / g of total nickel) for the corresponding catalyst, catalyst J, reduced to 430 ° C. The results are shown in the following tables.

This shows that with these catalysts having a relatively high nickel content, satisfactory catalysts can be obtained using a lower reduction temperature. In particular, it is noted that the high nickel content K catalyst (67.3%) has a relatively low nickel surface area (88 m2 / g of total nickel) when reduced to 430 ° C, the performance of the corresponding catalyst, the M catalyst, reduced at the lowest temperature, 360 ° C, was similar to, or better than, that of catalyst H which has a much lower nickel content (35.5%) but a much higher nickel surface area (177 m2 / g of total nickel).

Example 7 Catalysts N and 0 were prepared following a procedure described in Example 1, using a different alumina substrate. ALCOA HÍQ7412F, grades Q1037 and Q1058, respectively. The Q1037 grade had a weighted average surface diameter D [3.2] of 4.4 μm, a pore volume of 0.44 ml / g and a BET surface area of 137 m2 / g, giving an average pore diameter of approximately 13 nm . The Q1058 grade had a particle size (d, 3.2) of 1.5 μm, a pore volume of 0.34 ml / g of a BET surface area with mixtures of 117 m2 / g, giving an average pore diameter of approximately 12 nm. The catalysts were prepared using an alumina: nickel ratio of 2.25 wt.

The hydrogenation performance of the catalysts was tested using soybean oil as described in Example 2 and the results are shown in Table 8 below.

Table 8

Claims (16)

1. CLAIMS 1. A catalyst in the form of transition nickel / alumina particles containing from 5 to 75% by weight of total nickel, having a nickel surface area of at least 80 m2 per gram of total nickel, and an average diameter , weighted surface D [3,2] in the range of 1 μm to 20 μm.
2. 2. A particulate catalyst according to claim 1, having a nickel surface area of at least 110 m2 per gram of total nickel.
3. 3. A catalyst in the form of transition nickel / alumina particles according to any of claims 1 or 2, containing from 5 to 55% by weight of total nickel, having a nickel surface area of at least 130 m2 per gram of total nickel, and a weighted average surface diameter D [3,2] in the range of 1 μm to 20 μm.
4. 4. A particulate catalyst according to claim 3, having a total nickel content in the range of 20 to 35% by weight.
5. 5. A catalyst in the form of a particle according to claim 3 or claim 4, having an average pore diameter above 10 nm.
6. 6. A transition nickel / alumina particle catalyst according to claim 1, containing from 20 to 75% by weight of total nickel, having a nickel surface area of at least 80 m per gram of total nickel, a weighted average surface diameter D [3,2] in the range of 1 μm to 20 μm and an average pore diameter above 15 nm.
7. 7. A catalyst in the form of a particle according to claim 6, having a nickel surface area of greater than 110 m2 per gram of total nickel.
8. 8. A catalyst in the form of transition nickel / alumina particles according to claim 1, which continues from 20 to 75% by weight of total nickel, having a nickel surface area of at least 110 m2 per gram of total nickel , and the particles having an average size, weighted on the D surface [3,2] in the range of 1 μm to 20 μm and an average pore diameter above 10 nm.
9. 9. A catalyst in the form of particles according to any of claims 1 to 8, which has a total nickel content below 70% by weight.
10. 10. A particulate catalyst according to any of claims 1 to 9, having a surface-weighted average diameter D [3,2] below 10 μm.
11. 11. A catalyst precursor comprising a transition alumina and a reducible nickel compound, which when reduced with hydrogen at a temperature in the range of 250 to 450 ° C of a particulate catalyst according to any of the claims 1 to 10. A method for making a nickel / alumina catalyst containing from 5 to 75% by weight of the total nickel comprising forming in slurry a transition alumina powder having a weighted average surface diameter D [3,2] in the range of 1 μm to 20 μm with an aqueous solution of a nickel amine complex, heating the slurry to make the nickel amine complex decompose with the deposit of an insoluble nickel compound , filtering the solid residue from the aqueous medium, drying and optionally after calcination of the solid residue, reducing the solid residue. The method according to claim 12, wherein the alumina pore has an average pore diameter of at least 12 nm. 14. A method according to claim 12 or claim 13, wherein the transition alumina is a delta-alumina. 15. A concentrate having from 10 to 25% by weight of nickel comprising a particulate catalyst according to any of claims 1 to 10, or a catalyst precursor according to claim 11, or a catalyst in the form of a catalyst. The particle form prepared by a method according to any of claims 12 to 14, dispersed in a carrier. 16. The use of a catalyst in the form of particles according to any of claims 1 to 10, or a catalyst made by a method according to any of claims 12 to 14, or of a catalyst precursor according to the claim 11, or of a concentrate according to claim 15, for hydrogenation.