A METHOD FOR PREPARING A WATER-GAS AND HYDROFORMULATING CATALYST

Abstract: The invention relates to a method for preparing a catalyst for water-gas and hydroformulating reactions, which catalyst includes as active components a ruthenic carbonyl and a heterocyclic base on a solid carrier. The catalyst is formed by means of one or more successive reactions, in which the ruthenic carbonyl is fixed from a gas phase to said carrier and the heterocyclic base is fixed to the carrier either from the gas phase in the same way as from the ruthenic carbonyl or from a solution or melt of a heterocyclic base.

Description: The invention relates to a method for preparing a water-gas and hydroformulating catalyst for C₁ chemical reactions, especially for preparing a hydrogen gas from carbon monoxide and water, as well as for hydroformulating olefines by means of carbon monoxide and hydrogen. The transfer reaction CO + H₂O --> CO₂ + H₂ of the water gas is used for preparing hydrogen e.g. in the ammonia industry and for increasing the hydrogen content of a synthetic gas e.g. in the Fischer-Trosch synthesis. The reaction is most advantageous in a low temperature with respect to a thermodynamic yield. The catalysts used in the industry for a transfer reaction of a water gas are either mixtures of iron and chrome oxides operating at a high temperature or mixtures of copper, zinc and aluminum oxides catalyzing at a lower temperature. Even the last-mentioned catalysts require a temperature of min. 200°C, whereby the conversion of the reaction is partially limited by a reaction balance on the side of the reactants. One of the most effective catalysts operating af the lowest temperatures of the water-gas transfer reaction is a compound prepared from a ruthenic carbonyl Ru₃(CO)₁₂ and a 2,2'bipyridine and an inorganic oxide (FI patent no. 69620). The preparation method of the catalyst is based on mixing the reactants in a solid or liquid phase, in which case it is difficult to utilize the large specific area of the oxide component in the optimization of the catalyst activity. Alcohols and aldehydes are generally prepared by means of hydroformulating processes. The catalysts used in industrial processes are generally homogenic rhodium or cobalt carbonyls or phosphines: However, a heterogenous catalyst is usually easier to use, especially relative to the separation of the products. This advantage is especially emphasized when using expensive rhodium catalysts. The advantages of a heterogenous catalyst also include a higher thermal stability and minor corrosion problems. A hydroformulating catalyst can also be prepared from ruthenic carbonyl and bipyridine, which catalyst together with an inorganic oxide forms a heterogenous catalyst system (FI patent application no. 881361). The catalyst is prepared by admixing a ruthenic carbonyl, a bipyridine and an oxide in an organic solvent, from which the solvent is evaporated. A similar solvent based process is used in the EP-A-0 163 532 for the preparation of a catalyst for producing hydrogen gas from carbon monoxide and water, the catalyst comprising a ruthenium or a ruthenium-iron carbonyl compound having one or more chelating bidentake aromatic hetercyclic base(s), such as bipyridine, and optionally having a triaryl or trialkyl phosphine or phosphite ligand. These solvent based preparation methods cannot effectively utilize the large surface area of the porous oxide component. Because of this, the repeatability of the catalyst preparation is unadvantageous, and the solubility into the product mixture is detrimental to the heterogenous catalysis. The invention according the application relates to a new catalyst preparation method, wherein the catalyst is synthesized by means of successive controlled reactions. The method is adapted to the preparation of water-gas and hydroformulating catalysts formed by a ruthenic carbonyl, a bipyridine and an oxide. The method according to the invention for preparing a catalyst for water-gas and hydroformulating reactions, which catalyst includes as active components a ruthenic carbonyl and a heterocyclic base on a solid carrier, is thus characterized in that the catalyst is formed by means of one or more successive reactions, in which the ruthenic carbonyl is fixed from a gas phase to said carrier and the heterocyclic base is fixed to the carrier either'from the gas phase in the same way as from the ruthenic carbonyl or from a solution or melt of a heterocyclic base. In accordance with one of the embodiments of the invention, the catalyst is formed by performing one or more two-reaction cycles, in which the first reaction phase comprises the fixing of a ruthenic carbonyl from a gas phase to the surface of a carrier and the second reaction phase comprises the fixing of a heterocyclic base to the surface of a carrier. However, a heterocyclic base can be as readily fixed in such a way that the carrier treated with the ruthenic carbonyl according to the invention is treated with a heterocyclic-base melt or solution, whereby the base is fixed to the catalyst. The gas phase including a ruthenic carbonyl and a heterocyclic base advantageously also contains a gas acting as an inert carrier gas or a gas acting as a reactive carrier gas. For example nitrogen, argon or helium can be used as an inert gas and for example carbon monoxide or hydrogen can be used as a reactive gas. A catalyst forming according to an embodiment of the invention can be at any time before or after each reaction phase or between the reaction phases treated with a reactive gas for modifying its properties. In the method in accordance with the invention, can be applied e.g. a reactor 10 according to the figure, in which an oxide component 11 acting as a carrier is on top of a wire mesh or a ceramic sinter 12. Under the sinter 12 is led via a line 13 a carrier gas, which can be either an inert gas, such as nitrogen, argon or helium, or a reactive gas, such as carbon monoxide, as desired. The gas flow forms a fluidized bed, on which the oxide layer 11 is in continuously moving. Into the gas flow is led a ruthenic carbonyl Ru₃(CO)₁₂, which is sublimated from an oven by means of a suitable heating. The ruthenic carbonyl transfers with the carrier gas into the reactor 10, in which it can be adsorbed into the oxide by controlling the temperatures. Similarly, a bipyridine can be sublimated from the oven 15. The quantity of the adsorbing ruthenic can be controlled by means of the feeding time of the ruthenic and the reactor temperature, whereby a mono-molecular overlap, a reduced-layer overlap or a multilayer overlap can be selected. The correct temperatures and treatment times can be found experimentally, and they are dependent e.g on the evaporability of the active components used and the pressure conditions. When the ruthenic carbonyl is for example Ru₃(CO)₁₂, the treatment time can vary very widely e.g. from one second to 30 hours and the temperature can be 50 - 200°C. If the preparation of the catalyst is performed by using several successive ruthenic-carbonyl-bipyridine pulses, the treatment time in each pulse can be very short. If the ruthenic carbonyl is Ru(CO)₅, the temperatures to be used can be even considerably lower, even less than 0°C. The reactor pressure during the addition of the ruthenic carbonyl can also vary widely, e.g. between 10 mbar and 100 bar, but it is normally possible to operate near the atmospheric pressure, even though elevated temperatures are also possible. The ruthenic carbonyl is as such transferred by means of the inert carrier gas to the oxide. If a reactive carrier gas is used, the ruthenic carbonyl can be modified before the adsorption for example by decomposing or substituting. The reactive carrier gas can also affect the structure, composition and surface properties of the oxide surface. Gas flows can also be used in the reactor, by means of which the solid components of the catalyst are not transferred, but intermediate reactions are performed, with which the catalyst forming is treated. Such a gas flow can be for example hydrogen, with which a reduction is performed. The next phase of the preparation of the ruthenic-carbonyl-bipyridine-oxide is the reaction of a 2,2'-bipyridine with a ruthenic-carbonyl-oxide complex. This reaction can be performed e.g. in the reactor of the figure. When the reaction is performed in the reactor, a ruthenic carbonyl oven 14 is kept closed and a bipyridine oven 15 is opened. The oven is heated in such a way that the bipyridine is sublimated into the gas flow. In the reactor, the bipyridine immediately reacts with the ruthenic carbonyl - oxide complex. The suitable temperatures and treatment times can be found experimentally, and they are generally 50-200°C and between one second and 20 hours. The reaction can be continued by feeding a new ruthenic carbonyl-bipyridine pulse, whereby the ruthenic-bipyridine-oxide ratio of the catalyst can be adjusted to the optimum value. The catalyst can be further activated in the reactor either by means of heat or a gas treatment. The bipyridine reaction can also be performed in such a way that the ruthenic carbonyl - oxide complex is transferred into a molten bipyridine, whereby a catalyst is prepared. When a silica gel SiO₂ is used as an oxide and a carbon monoxide is used as a carrier gas, a new reactive surface complex is formed in the fluidized-bed reactor from the ruthenic carbonyl Ru₃(CO)₁₂, the IR spectroscopic properties of which complex clearly deviate from a surface complex prepared with an inert gas or adsorbed from a solution. This new complex immediately reacts with the bipyridine in room temperature. The Ru₃(CO)₁₂-2,2'-bipyridine silica gel catalyst acts both in the transfer reaction of the water gas and in the hydroformulation of the olefines. The highest activity reached in the water gas reactor 19500 mol H₂/mol Ru₃(CO)₁₂ * 24 h is 2-4 times greater than the results reported earlier. In the hydroformulation, the activities are slightly lower than those reported earlier, but the stability of the catalyst is correspondingly better. The advantages of the invention described above in comparison with prior art are a better controllability of the ruthenic-bipyridine-oxide catalyst and thereby more effective catalysts. The preparation reaction is performed in controlled manner by phases, whereby the quantity of the reactants used correspond only the quantity with which the oxide surface is ready to react in the different phases of preparation. Each reaction phase can be characterized separately, owing to which a more detailed analysis of the preparation reaction is possible. When comparing the analyzed metal content of the catalyst with the surface area available for the oxide adsorption, it can be seen that the change reaction gives with one pulse a clearly lower monomolecular overlap degree. A higher overlap degree can be obtained by changing the reactor temperature or by extending the sublimation time. In the method according to the invention, the ruthenic carbonyl is preferably Ru₃(CO)₁₂. A bipyridine, especially a 2,2'-bipyridine ia used as a heterocyclic base. Any inorganic oxide can be used as a solid carrier, but an especially preferable oxide is silica. The carrier is preferably dried before the reaction with the ruthenic carbonyl for example by heating at about 600°C. The catalysts prepared with the method according to the invention are especially suitable for the transfer reaction of the water gas for preparing a hydrogen gas from carbon monoxide and water, but the same catalysts can also be applied to the hydroformulation of olefines into alcohols. The invention is next described by means of examples. Example 1 The catalyst was prepared by sublimating Ru₃(CO)₁₂ to an oxide on a fluidized bed (silica F-22, dried at 600°C, 2.3 g) in a CO gas flow (flow rate = 30 ml/min) for 5 hours at 145°C. The ruthenic content measured with an atomic absorption spectrophotometer (calculated per 1 g of oxide) was 4.7 mg. 1.2 g of ruthenic-sublimated oxide and 0.2 g of 2-2'-bipyridine were admixed in an N₂ atmosphere, evacuated and kept in an oil bath of 80°C for 3 days. Examples 2-5 As in Example 1, except that in Example 2 the sublimation time was 10 hours and the mixture contained 1.7 g of ruthenic-sublimated oxide (determined ruthenic content 11.7 mg/g of oxide), and in Example 3 the sublimation time was 15 hours and the quantity of oxide in the mixture was 1.6 g (ruthenic content 16.0 mg/g of oxide), in Example 4 the sublimation time was 20 hours, the flow rate 46 ml/min and the quantity of oxide in the mixture was 1.8 g (ruthenic content 28.0 mg/g of oxide), and in Example 5 the sublimation time was 30 hours and the flow rate 46 ml/min and quantity of oxide 1.8 g (ruthenic content 51.4 mg/g of oxide). Example 6 The catalyst was prepared by sublimating Ru₃(CO)₁₂ to an oxide on a fluidized bed (silica F-22, dried at 600°C, 2.5 g) in a CO gas flow for 11.5 hours at 120°C. 2,2'-bipyridine was then sublimated for 11.5 hours at 65°C. The reactor was the kept in an oil bath of 100°C for 4 days. The determined ruthenic content was 12.1 mg/1 g of the catalyst. Example 7 As in Example 6 except that the sublimation time was 1 hour at a time and the cycle was repeated 10 times. After each addition of 2,2'-bipyridine, the catalyst was cured at 100°C. The determined ruthenic content was 5.3 mg/g of the catalyst. Example 8 The catalyst of Example 1 (0.5 g), 1-hexene (1.0 cm³), toluene (5.0 cm³) and benzene (0.2 cm³) were transferred in a nitrogen atmosphere into an autoclave (V = 0.09 dm³), and 2.5 MPa of H² and 2.5 MPa of CO were added. The autoclave was kept at 150°C for 17.5 hours. The product mixture was analyzed by means of gas chromatography. The reaction product did not contain alcohols or aldehydes. Example 9 As in Example 8 except that the catalyst of Example 2 was used as the catalyst. The reaction product contained 5% of C₇ alcohols. Example 10 As in Example 8 except that the catalyst of Example 3 was used as the catalyst. The reaction product contained 26% of C₇ alcohols. Example 11 As in Example 8 except that the catalyst of Example 4 was used as the catalyst. The reaction product contained 35% of C₇ alcohols. Example 12 As in Example 8 except that the catalyst of Example 5 was used as the catalyst. The reaction product contained 36.5% of C₇ alcohols. Example 13 As in Example 8 except that the catalyst of Example 6 was used as the catalyst. The reaction product contained 35% of C₇ alcohols. The Examples 8-13 show that as the ruthenic content of the catalyst increases, also the alcohol conversion increases but yet reaches a certain maximum level in these hydroformulating conditions. Example 14 As in Example 13 except that the reaction time in the hydroformulation was 66 h. The reaction product contained 52% of C₇ alcohols. Example 15 The catalyst of Example 7 was tested in a continuous reactor in a water-gas transfer reaction. 1.0 g of the catalyst was packed into a reaction tube (p(CO) = 7 bar, P(H₂O) = 6.5 bar, T = 150°C, v = 6-40 ml/min), the product gas flowing through it was analyzed with a gas chromatograph. The maximum activity obtained was 5800 mol H₂/mol Ru₃(CO)₁₂ * 24 h. Example 16 As in Example 15 except that the catalyst of Example 3 (0.9 g) was used as the catalyst. The maximum activity obtained was 16900 mol H₂/ mol Ru³(CO)₁₂ * 24 h. Example 17 As in Example 15 except that the catalyst of Example 5 (0.7 g) was used as the catalyst. The maximum activity obtained was 19500 mol H₂/ mol Ru³(CO)₁₂ * 24 h.

Claims: A method for preparing a catalyst for water-gas and hydroformulating reactions, which catalyst includes as active components a ruthenic carbonyl and a heterocyclic base on a solid carrier, characterized in that the catalyst is formed by means of one or more successive reactions, in which the ruthenic carbonyl is fixed from a gas phase to said carrier and the heterocyclic base is fixed to the carrier either from the gas phase in the same way as from the ruthenic carbonyl or from a solution or melt of a heterocyclic base. A method according to Claim 1, characterized in that the catalyst is formed by performing one or more two-reaction cycles, in which the first reaction phase comprises the fixing of a ruthenic carbonyl from a gas phase to the surface of a carrier and the second reaction phase comprises the fixing of a heterocyclic base to the surface of a carrier. A method according to Claim 2, characterized in that said gas phase contains an inert and/or reactive gas. A method according to Claim 3, characterized in that nitrogen, argon or helium is used as an inert gas and carbon monoxide or hydrogen as a reactive gas. A method according to any of the Claims 2-4, characterized in that the catalyst forming before or after each reaction phase or between the reaction phases is treated with a reactive gas for modifying its properties. A method according to any of the preceding Claims, characterized in that such temperature conditions and treatment times are selected in each reaction phase that a monomolecular overlap, a reduced-layer overlap or a multilayer overlap of the active component can be achieved on a carrier. A method according to Claim 1 or 2, characterized in that the ruthenic carbonyl is added to the carrier from a gas phase containing carbon monoxide. A method according to any of the preceding Claims, characterized in that the ruthenic carbonyl is selected from a group consisting of Ru³(CO)₁₂ and Ru(CO)₅. A method according to any of the preceding Claims, characterized in that the heterocyclic base is 2,2'-bipyridine. A method according to any of the preceding Claims, characterized in that the solid carrier is an inorganic oxide, preferably a silica.

Inventors: ALVILA, LEILA, HIRVA, PIPSA, KRAUSE, OUTI, PAKKANEN, TAPANI, VENAELAEINEN, TAPANI, Venäläinen, Tapani
Applicants: NESTE OY
Application year: 1990
Main classification: B01J31
IPC codes: C07C29, C07C45, C01B3, C07C47, C07C27, C07C31, C07B61, B01J31