NO803956L - NICKEL-BASED, BASELY CATALYSTS AND PROCEDURES IN PRODUCING THEREOF. - Google Patents

Description

The invention relates to a nickel-based, supported catalyst

and method of production thereof. The catalyst is particularly useful in the hydrogenation of polyunsaturated organic compounds to the corresponding partially or completely saturated compounds.

Supported nickel catalysts with a support, such as diatomaceous earth, aluminum oxide or silicon dioxide gel, have long been used as heterogeneous catalysts in the selective hydrogenation of polyunsaturated organic compounds to di- or monounsaturated compounds. One of the most important of these processes is the hydrogenation of unsaturated fatty acids in vegetable oils and animal fats or the hydrogenation of free unsaturated fatty acids to the corresponding partially or fully saturated compounds. Currently, world consumption exceeds year of oils and fats that have been hydrogenated for further use in foodstuffs and technical products, 4 x 10^ tonnes. This fact and the effort to make maximum use of all food resources forces the producers to improve the hydrogenation methods, so that, in addition to achieving an optimal economic process, it should also be able to provide a selective way to

perform the process on.

Due to the boiling points of the treated materials, the hydrogenation process is carried out in the liquid phase at elevated temperature and pressure and in the presence of a heterogeneous catalyst, so that a relatively complex three-phase liquid-gas-solid system is obtained. Apart from technological parameters of the equipment, such as equipment for continuous or discontinuous operation, and the method of mass and heat transfer in the system etc., it is the quality of the catalyst used that is of greatest importance. To be able to fully utilize a hydrogenation unit's. capacity, it is necessary to achieve a high reaction rate, and the prerequisite for this is that the catalyst has high activity. In order to obtain a product with the required composition so that it contains pre-selected esters of fatty acids, emphasis must also be placed on the selective effect of the hydrogenation catalyst. Thus, when hydrogenating vegetable oils, such as rapeseed oil or soybean oil, which contain glycerides of linoleic acid, it is necessary for the product to have a constant taste and smell, that the glycerides of linolenic acid are completely or essentially completely removed, while the content of glycerides of linoleic acid must be reduced as little as possible and the content of glycerides of stearic acid must be increased as little as possible.

Nickel catalysts that have so far been used on a technical scale usually exhibit high activity together with high selectivity with regard to the hydrogenation of polyunsaturated organic compounds, and as a rule only one of these properties is dominant.

According to the invention, a nickel-based catalyst is provided which is supported on an inorganic carrier, such as diatomaceous earth, aluminum oxide or silicon dioxide gel, and which comprises 10-85% by weight of nickel, of which 40-99% by weight is made up of nickel in the form of metal, and 0.05 -6.7 wt% boron. The catalyst according to the invention can also contain 0.01-10% by weight of copper, silver, chromium, zirconium, thorium, tin, rhenium,

one or more of the metals from group VIII or a mixture of at least two of the aforementioned metals.

The above-mentioned catalyst is prepared in the following way: (i) A suspension of an inorganic carrier is precipitated with alkali in a nickel salt solution, (ii) the mixture of the inorganic carrier and the precipitated nickel dihydroxide and/or nickel hydroxide carbonate with a composition NiCO-j.x Ni(OH) 2.y H 2 O, in which x denotes a number from 1 to 30 inclusive and y an arbitrary number, is exposed to the influence of an alkaline borohydride solution in an amount of 0.005-1.25 mol borohydride per moles of nickel, this step being carried out at a temperature of 20-100°C and a pH above 10 within 5-60 minutes,

(iii) the mass obtained is washed and dried,

(iv) the mass is calcined at a temperature of 300-500°C, and (v) the calcined mass is reduced at a temperature of 250-480°C with a degree of reduction of 0.40-0.99.

When the supported nickel-based catalyst is also to contain the above-mentioned modifying metals, none of an inorganic support and the nickel dihydroxide and/or the nickel hydroxide carbonate are treated with the above-mentioned composition with an addition of a salt of copper, silver, chromium, zirconium, thorium, tin, rhenium or one of the metals from group VIII or a mixture of at least two of the aforementioned salts, in an amount corresponding to 0.1-10% by weight of the metal.

The present catalyst can be used in a method for the hydrogenation of oil-saturated organic compounds to the corresponding fully or partially saturated compounds, where hydrogen at a pressure of 1.013 x 10

2.7 x 10 g of Pa are brought into contact with a polyunsaturated organic compound at a temperature of 30-240°C in the presence of a supported nickel-based catalyst as described above. The contact time is chosen so that the product has the desired composition.

The nickel-based catalyst according to the invention is particularly suitable for use as a catalyst for the hydrogenation of unsaturated fatty acids and their glycerides to the corresponding fully or partially saturated compounds. The process is carried out at a hydrogen pressure of 1.013 x 10^ 2.7 x 10 6 Pa at a temperature of 80-240 oC. The conversion time is chosen again so that the fatty acids in the product have the desired composition. The amount of catalyst used can advantageously be 0.01-2% by weight of the metallic nickel, based on the weight of the treated raw material, preferably 0.02-0.06% by weight.

The hydrogenation process described here can be carried out

continuous or discontinuous.

When the precipitate obtained by mixing a nickel salt top-. solution with an alkali, is exposed to an alkaline borohydride solution, a replacement of a part of the nickel dihydroxide and/or nickel hydroxide carbonate's surface hydroxy groups with the (Dll^) anion is obtained. The finished catalyst will then exhibit a several times higher activity and selectivity in terms of hydrogenation of polyunsaturated organic compounds to the corresponding fully or partially saturated compounds, compared to a similar product that has not been treated with the alkaline borohydride.

The catalyst according to the invention is suitable for use in such processes as the hydrogenation of cyclooctadiene to cyclooctene. By far the most important industrial application, however, is for the hydrogenation of unsaturated fatty acids and their glycerides to the corresponding fully or partially saturated compounds. When the process is carried out on a selective basis so that partially hydrogenated vegetable oils are obtained, the hydrogenation process is usually stopped at 0-30% by weight

of the original amount of linolenic acid. When treating e.g. rapeseed oil with a minimal content of erucic acid with an initial iodine value of 115, the hydrogenation process is stopped when an iodine value of 90-100 has been reached. Under the given conditions, the content of esters of linolenic acid will be reduced to 50-80% by weight of the original amount. Oils treated in this way are then suitable for further use in the production of different types of salad oil, mayonnaise or margarine etc.

The catalyst's selective properties also make it possible

to achieve a relatively high yield of oleic acid when vegetable oils are hydrogenated. When processing rapeseed oil with a minimal content of erucic acid, e.g. the maximum content of the esters of oleic acid in the product be approx. 83%, and the product obtained can be further processed for technical purposes.

The catalyst according to the invention is also suitable for the hydrogenation of vegetable oils into a product with a melting point of 32-39°C which is further processed into margarine or diabetic fats etc. It can also be used for the complete hydrogenation of vegetable oils or free fatty acids into products with an iodine value of 2-5/where the catalyst's high activity plays the main role.

The invention will be described in more detail using the examples below.

Example 1

A suspension of diatomaceous earth in a nickel nitrate solution was added at 95°C to a heated sodium carbonate solution with stirring. The precipitation was finished by adding a sodium hydroxide solution in such a quantity that the molar ratio alkali:nickel became 2:1. The "precipitate" obtained, which after filtration, washing and drying had the composition NiC03. 10.5 Ni(OH)2. 7 H20, was at a pH of 10.5 exposed to the influence of a 10% aqueous solution of sodium borohydride (pH =10) during 60 minutes. Then the precipitate was filtered off, washed three times with methanol, calcined at 350°C and finally reduced at 360-380°C during 10 hours until a degree of reduction of 0, 86. The catalyst obtained contained 51.1% by weight of Ni and 0.8% by weight of boron, the rest being the carrier.

The catalyst that had been prepared in this way showed a significantly higher activity and selectivity with regard to the hydrogenation of cyclooctadiene to cyclooctene in the liquid phase, compared to a catalyst that had been prepared in the same way, but with the difference that the nickel hydroxide carbonate had not been exposed to sodium borohydride. The quantitative results, including the conditions of the hydrogenation reaction, are summarized in Table I.

Table I

Comparison between the hydrogenation course of cyclooctadiene to cyclooctene using a catalyst prepared as described in example 1 (catalyst A) and a similar catalyst prepared without treatment with sodium borohydride (catalyst D).-

Reaction conditions: temperature 30°C, hydrogen pressure 1.0374 x 10 5 Pa, catalyst concentration 0.833 g Ni per liter reaction mixture, solvent n-heptane.

example' 2

A nickel nitrate solution containing 10% silver nitrate was treated using the same method as described in Example 1. The catalyst obtained after the sample was reduced at 350°C to a degree of reduction of 0.8,

contained 45.8% by weight of nickel, 0.53% by weight of boron and 0.5% by weight of silver, the rest being the carrier. The catalyst was

three times as active and 2.8 times as selective in the hydrogenation of cyclodecatriene to cyclodecene as the same sample that had not been treated with sodium borohydride.

Example 3

A precipitation vessel was filled with a suspension of diatomaceous earth in a nickel chloride solution containing pdCl 2 in an amount equivalent to 0.1% palladium. After heating to 98°C, the nickel hydroxide carbonate was precipitated by adding sodium carbonate in an amount of 2.1 mol per mol of nickel. Then, 0.01 mol% sodium borohydride was added to the suspension in the mother liquor, and the mixture, which had a pH of 13.7, was stirred for 10 minutes at 98°C. After filtering, washing, drying and calcining at 400°C, the catalyst was reduced at 450°C to a reduction degree of 0.85. The obtained catalyst contained 58.2 wt% Ni, 0.85 wt% B.

and 0.1% by weight of Pd, the rest being the carrier. The catalyst's selectivity for the hydrogenation of cyclooctadiene to cyclooctene was improved by a factor of

3.1 as a result of the treatment with sodium borohydride.

Example 4

A nickel nitrate solution containing gis.elgur was

at 30°C precipitated with sodium hydroxide in an amount of 1.5 mol per moles of nickel. The resulting suspension of nickel dihydroxide was mixed with a sodium borohydride solution (0.6 mol borohydride per mol nickel) and heated at 70-80°C for 60 minutes. After filtration, washing, drying, calcination at 300°C and reduction at 350°C until a degree of reduction of 0.63, the catalyst contained 28% by weight of nickel and 0.3% by weight of boron. The catalyst showed 5.3 times as high selectivity in the hydrogenation of cyclooctadiene to cyclooctene as a similar sample that had not been treated with the alkaline borohydride.

Example 5

A stainless steel autoclave fitted with a paddle wheel stirrer was charged with 80 g of refined rapeseed oil with minimal erucic acid content and with a catalyst containing 3.8 wt% boron and 27 wt% nickel, 48 wt% of which the latter amount was present as metallic nickel. The amount of catalyst was 0.04% by weight calculated as nickel, based on the weight of the treated oil. The hydrogenation was carried out at 180°C with a hydrogen pressure of 1.52 x 10<5>Pa. The changes in the composition of the product during the hydrogenation are reproduced in Table II, which clearly shows the catalyst's high selectivity as well as its high activity. The quality of the products obtained satisfied the requirements for further processing for the production of ingredients for salad oil, mayonnaise, margarine or diabetic fat etc.

Example 6

Using the same autoclave as described

in example 5, 80 g of sunflower oil with the following composition was hydrogenated:

The iodine value determined by the method of Wijs was found to be 129. The catalyst from the previous process was filtered off and recycled in an amount of 0.03% by weight calculated as nickel, based on the weight of the oil. The hydrogenation was carried out at 140 oC and a hydrogen pressure of 1.52 x 10^ Pa. After 160 minutes, the product's melting point reached 33.2°C, and the product had the consistency necessary for it to be further processed into margarine.

Example 7

80 g of fatty acids with an iodine value of 56 and distilled from animal fat were hydrogenated in the same autoclave as described in example 5. The hydrogenation was carried out at 200°C and a hydrogen pressure of 2.354 x 10^ Pa in the presence of a catalyst containing 0.25 wt% boron and 45 wt% nickel, 87% of the latter being in the form of metallic nickel. The amount of catalyst was 0.43% by weight calculated as nickel and based on the weight of the treated fatty acids. After 90 minutes, an iodine value of 2.5 was reached.

Claims (8)

Nickel-based catalyst supported on an inorganic support, such as diatomaceous earth, aluminum oxide or silicon dioxide gel, characterized in that it comprises 10-85% by weight nickel, of which 40-99% consists of metallic nickel, and 0.05-6.7% by weight boron. 2. Catalyst according to claim 1, characterized in that it contains 0.1-10% by weight of copper, silver, chromium, zirconium, thorium, tin, rhenium or a metal from group VIII or a mixture of at least two of the aforementioned metals. 3. Method for producing a nickel-based catalyst supported on an inorganic support, such as diatomaceous earth, aluminum oxide or silicon dioxide gel, characterized by the steps that (i) a suspension of an inorganic carrier in a nickel salt solution is precipitated with an alkali, (ii) the mixture of the inorganic carrier and the precipitate nickel dihydroxide and/or nickel hydroxide carbonate with the composition NiCO^ . x Ni(OH) 2 . y H^ O, where x denotes a number from 1 to 30 inclusive and y is an arbitrary number, is exposed to the influence of an alkaline borohydride solution in an amount of 0.005-1.25 mol borohydride per moles of nickel at a temperature of 20-100°C and a pH above 10 within 5-60 minutes, (iii) the mass obtained is washed and dried, (iv) the mass is calcined at a temperature of 300-500°C, and (v) the calcined mass is reduced at a temperature of 250-480°C until a degree of reduction of 0.40-0.99. 4. Method according to claim 3, characterized in that in step (ii) the mixture exposed to the influence of the alkaline borohydride solution comprises a salt of copper, silver, chromium, zirconium, thorium, tin, rhenium or one of the metals from group VIII or a mixture of at least two of the salts in an amount corresponding to 0.1-10% by weight calculated as metal. 5. Procedure for the hydrogenation of polyunsaturated organic compounds to the corresponding fully or partially saturated compounds in the liquid phase, characterized in that hydrogen at a pressure of 1.013 x IO <5> - 2.7 x IO <6> Pa is brought into contact with a polyunsaturated organic compound at a temperature of 30-240°C 1 presence of a nickel-based catalyst according to claim 1 or claim 2 for sufficient time for the product's required composition to be achieved. 6. Procedure for the hydrogenation of unsaturated fatty acids and/or glycerides thereof to the corresponding fully or partially saturated compounds in the liquid phase, characterized in that hydrogen at a pressure of 5 6 of 1.013 x 10 - 2.7 x 10 Pa is brought into contact with an unsaturated fatty acid or a mixture of unsaturated fatty acids and/or glycerides thereof at a temperature of 80-240°C in the presence of a nickel-based catalyst according to claim 1 or requirement 2 for sufficient time for the product's required composition to be achieved. 7. Method according to claim 6, characterized in that a catalyst quantity of 0.01-2% by weight calculated as metallic nickel and based on the weight of the treated raw material is used. 8. Method according to claim 6 or 7, characterized in that a catalyst amount of 0.02-0.06% by weight is used, calculated as metallic nickel and based on the weight of the treated raw material.