Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C5/00—Preparation of hydrocarbons from hydrocarbons containing the same number of carbon atoms
  • C07C5/02—Preparation of hydrocarbons from hydrocarbons containing the same number of carbon atoms by hydrogenation
  • C07C5/10—Preparation of hydrocarbons from hydrocarbons containing the same number of carbon atoms by hydrogenation of aromatic six-membered rings
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
  • B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
  • B01J23/74—Iron group metals
  • B01J23/755—Nickel
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
  • B01J37/02—Impregnation, coating or precipitation
  • B01J37/0238—Impregnation, coating or precipitation via the gaseous phase-sublimation
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
  • B01J37/08—Heat treatment
  • B01J37/082—Decomposition and pyrolysis
  • B01J37/086—Decomposition of an organometallic compound, a metal complex or a metal salt of a carboxylic acid
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C2521/00—Catalysts comprising the elements, oxides or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium or hafnium
  • C07C2521/02—Boron or aluminium; Oxides or hydroxides thereof
  • C07C2521/04—Alumina
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C2523/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group C07C2521/00
  • C07C2523/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group C07C2521/00 of the iron group metals or copper
  • C07C2523/74—Iron group metals
  • C07C2523/755—Nickel

Definitions

• the present invention concerns a method for manufacturing such a heterogeneous catalyst according to the preamble of claim 1 suited for hydrogenation of aromatics which contains nickel bonded onto a porous inorganic support such as alumina.
• Conventional heterogeneous hydrogenation catalysts incorporate a catalytically active component bonded onto a support material.
• the most common methods for bonding the active components onto the support are impregnation, precipitation and ion exchange techniques.
• the precursors hereby are compounds of the catalytically active component such as salts, for example, which are soluble in a suitable solvent such as water, alcohol or a hydrocarbon.
• a plurality of work steps have compulsory in conventional catalyst manufacturing methods. Among others, the following work steps have been required: Making a solution of the catalyst species or its precursor; treatment of the support with the solution; removal and recovery of unreacted suspension; catalyst wash, drying and calcining plus separate processing steps for the activation of the catalyst.
• NiCl 2 is condensed onto the alumina surface, the chloride is removed with the help of hydrogen and the nickel is reduced.
• the obtained Ni concentration is dependent on the used reaction time.
• nickel is poorly dispersed onto the support surface, forming clusters of 500...600 nm diameter onto the support surface.
• the formation of such large clusters causes an appreciable reduction of the active nickel area capable of catalytically interacting with the reactant vapor phase.
• the invention is based on principle that nickel is deposited onto the support material surface from vapor phase containing a compound of sufficiently high vapor pressure.
• a compound employed in the invention is an organonickel compound.
• the reaction between the nickel compound and the support is carried out under conditions in which the nickel compound is chemisorbed on the surface bonding sites of the support.
• the support is heated to a temperature which is above the condensation temperature of the nickel compound employed, yet below the decomposition temperature of said compound.
• the vaporized nickel compound is offered in an excess ratio relative to the surface bonding sites available of the support surface, whereby the bonding process is controlled only by the qualitative properties of the surface bonding sites and the reagerit under the process conditions used. According to the above-described method, advantageous bonding sites on the support material surface will be saturated with nickel.
• the catalyst in accordance with the invention is principally characterized by what is stated in the characterizing part of claim 1.
• the method according to the present invention it is possible to attain an improved distribution of the nickel species on the support material surface. It has been found that the size of the Ni particles remains very small even after repeated reaction cycles. Such a good dispersion of the metal species is achieved by way of the above-described saturation-controlled surface reactions which are described in greater detail in FI patent publication 84562 and FI patent application 913438.
• saturation-controlled surface reactions the metal compound to be bonded is introduced onto the support material surface at such a high temperature that chemisorption reactions alone are possible between the metal compound and the support.
• the number of bonding sites on the support has been regulated to a desired level by way of preheating, for example, prior to the actual reaction.
• the reagent is allowed to interact with the support until essentially all bonding sites capable of forming a bond have reacted. After this stage, any further prolonging of the reaction time or introduction of excess reactant onto the support surface has no contribution to the achieved metal species content.
• the present method is thus entirely different from the method disclosed by Uemura et al. in which the metal species content is determined by the reaction time and reactant concentration.
• the precursor employed is Ni-acetylacetonate [abbreviated as Ni(acac) 2 in the text below].
• Ni(acac) 2 in the text below.
• This molecule has a size which is large in relation to the density of bonding sites on the support surface.
• the pre ⁇ cursor employed is nickelocene (dicyclopentadienyl-nickel(-Q).
• the invention can be implemented using other organic nickel compounds, provided that their organic parts are capable of inhibiting such a close deposition of two adjacent nickel atoms that they could form large-size clusters when bonding onto the support surface.
• Support materials onto which said nickel compound is deposited according to the invention are porous inorganic supports, advantageously aluminum or silicon oxides, or mixtures thereof. Also magnesium or titanium oxides, or mixtures thereof, or cogels formed with the above-mentioned inorganic supports may be used as support materials.
• the process conditions are set so as to prevent condensation of the Ni compound onto the support surface, but rather to favor the formation of a chemical bond with aluminum oxide, or alternatively, to evaporate away from the surface and find the closest free bonding sites on the surface.
• the operating temperature is advantageously in the range 50...300 °C.
• the advantageous temperature range is 190...220 °C, e.g., approx. 200 °C.
• Nickelocene is advantageously processed at approx. 100...250 °C.
• the reaction temperature can be set above the vaporization temperature of the compound.
• the precursor e.g., nickelocene
• the precursor is evaporated at approx. 130...170 °C (e.g., at approx. 150 °C) and reacted with aluminum oxide at 100...300 °C, e.g., at approx. 180...220 °C (typically at approx. 200 °C).
• the reagent is introduced in an excess ratio relative to the number of bonding sites available on the support surface.
• the unreacted Ni reagent is purged from the reaction space with the help of an inert carrier gas at the reaction temperature employed. Then, a portion of the reagent adhering to the support remains bonded by the ligand to the nickel species.
• Removal of the ligand can be performed with the help of, e.g., water vapor or dry/moist air at a temperature above the reaction temperature.
• the ligands are removed at approx. 200...600 °C, particularly advantageous at approx. 300... 500 °C. With nickelocene, the ligands are advantageously removed at approx. 200...400 °C.
• the Ni content of the catalyst can be increased stepwise by processing the catalyst through a greater number of Ni reagent/air reaction cycles.
• the annexed diagram shows how the nickel content increases with Ni(acac) 2 as the precursor from approx. 3 wt. % after one process cycle to over 21 wt. % after 10 process cycles.
• the number of reaction cycles can be easily implemented by introducing the Ni- containing compound, nitrogen and air into the reaction space in a cyclic sequence.
• the catalyst is activated with the help of conventional techniques by using hydrogen reduction of the nickel bonded onto the alumina surface at elevated temperature, advantageously at approx. 300...600 °C.
• a nickel-alumina catalyst suited for use in a hydrogenation reaction of sulfur-free hydrocarbon feedstock containing aromatics, in which catalyst the nickel content is approx. 3...21 wt. % .
• the nickel content is approx. 3...21 wt. % .
• To manufacture such a catalyst only four or five reaction cycles are needed.
• Typical application examples of a catalyst obtained in accordance with the present invention are represented by hydrogenation reactions of benzene and toluene.
• the invention offers significant benefits.
• the catalyst according to the invention is particularly suited to the hydrogenation of aromatics in both liquid and gas phase conditions using sulfur-free feedstock.
• sulfur is a well-known catalyst poison for Ni-containing catalysts that by all means should be removed prior to hydrogenation.
• the activity of the novel catalysts in toluene conversion into methylcyclohexane has been superior in comparison with both catalysts made by impregnation for reference tests and three commercially available catalysts. The tests have been carried out in both differential and integral conditions, as well as in liquid and gas phases.
• the nickel content was found satisfactory and the dispersion of the nickel species at least as good, in multiple cases even better, than in catalysts marketed commercially and manufactured by way of impregnation.
• Catalysts according to the invention also have a higher activity than other prior-art catalysts prepared from the gas phase, which property evidently can be traced to good dispersion of the active species.
• Manufacture of catalysts according to the invention is simpler than through conventional methods therein that a lower number of reaction steps is needed relative to prior-art methods and the different manufacturing steps are carried out sequentially in a single reaction space without using solvents.
• the concentration of the active species in the catalyst is controlled by the steric properties of the support surface and the reactant compounds employed, not by the concentrations used in the reaction space.
• an improved method over prior-art techniques is achieved for controlling the nickel content in catalyst manufacture to a desired level by varying the number of cycles of the pretreatment/reaction sequences.
• the invention is next examined with the help of a few exemplifying embodiments.
• the diagram of the annexed drawing shows the Ni content in wt. % of a catalyst made according to the invention as a function of Ni(acac) 2 cycles employed. A detailed description of the diagram was given above.
• the support for the catalyst was aluminum oxide by AKZO under the trade name Alumina 000-1.5.
• the product was crushed and screened to particle size 0.15...0.3 mm.
• a 5...10 g aliquot of the support was used in each catalyst batch.
• After pretreatment at 800 °C the surface area of Al 2 O 3 was 152 m 2 /g. The surface area was determined using the multi-point BET method.
• the reagent used was Ni(acac) 2 , which is a commercially available compound.
• the vaporization temperature of this compound is 190...210 °C.
• the reagent was introduced onto the support in gas phase in excess ratio relative to the hydroxyl groups (surface bonding sites) available on the support surface.
• the number of hydroxyl groups in alumina has been theoretically determined by, i.a., Knozinger, H., Ratnasamy, P., Catal. Rev. Sci. Eng. j (1978) 31. According to tests performed by the inventor, complete saturation of alumina surface, that is, a nickel content of approx. 3 wt. % can be attained by using 1.5 mmol of the reagent Ni(acac) 2 .
• the catalysts were manufactured by placing the support in a static column through which the reagent vapor was routed from top downward. By using the reagent in 2-...3-fold excess amounts (approx. 3...4.5 mmol), the nickel content at the top of the column was assured to be equal to that of the column lower end, thus guaranteeing the saturation of the support surface.
• the catalysts listed in Table 1 were manufactured at a partial vacuum of 10...50 mbar, and the carrier gas was nitrogen.
• the basic structure of the apparatus employed in the manufacture is disclosed in FI patent publication 84562.
• the catalyst manufacture comprises five steps. During the first step the support material was heat-treated in an oven under air atmosphere (step A). This procedure removed physisorbed water and a portion of OH groups from the support surface. Next, any water physisorbed during possible storage of the support material was removed from the support in the reaction space under nitrogen atmosphere (step B). During the subsequent step the Al 2 O 3 support was treated with Ni(acac) 2 , whereby nickel was chemisorbed onto the aluminum oxide surface (step C).
• step D The posttreatment applied was purging with air which removed acac-ligands still left on the Ni species. Moist air was used for air purging. As a final treatment the catalyst was purged with nitrogen (step E).
• Table 1 shows six exemplifying grades of Ni/Al 2 O 3 catalysts with temperatures and durations of the above-described manufacturing steps, as well as the numbers of cycles in the repetition of the above steps in the manufacture of each catalyst. The last column of table gives the nickel content of the manufactured catalyst in weight percent. The nickel content was determined using x-ray fluorescence and the carbon content by combustion (via determination of carbon dioxide). All catalysts listed in Table 1 had a carbon content below the detection threshold of 0.1 wt. % .
• Catalyst #7 was prepared in the same fashion as Catalyst #2 with the exception that the number of process cycles was 2 and the ligands were removed by water vapor treatment. The nickel content of Catalyst #7 was 4.6 wt. % .
• Example 2a (reference)
• Reference catalysts were made using a conventional impregnation method in the following fashion: First, nickel nitrate was dissolved in water to an aqueous nickel nitrate solution. Next, dry impregnation was carried out until the entire volume of the solution was absorbed by the support material pores. The amount of nickel nitrate was approx. 0.12 g of Ni per 1 g of support. The support material was agitated by shaking during the impregnation step. Subsequently, the catalyst samples were dried at 120 °C for 12 h and heat-treated at 300 °C under oxidizing atmosphere. When the number of process cycles was varied from 1 to 3, the Ni contents of the catalyst samples were 5.4, 11.3 and 17.7 wt. %, respectively.
• Reference catalyst samples were made using an impregnation method.
• Ni(acac) 2 was dissolved in tetrahydrofuran (THF) to obtain a solution (4.2 g Ni(acac) 2 per 10 ml THF).
• the dry-impregnation step was carried out until the entire volume of the solution was absorbed by the support material pores.
• the amount of the solution applied was approx. 0.5 ml per 1 g of support.
• the support material was agitated by shaking during the impregnation step.
• the catalyst samples were dried at 120 °C for 12 h and the (acac)-ligands were removed by heat-treatment for 4 h at 300 °C under oxidizing atmosphere. Using different numbers of process cycles (comprising impregnation, drying and oven- treatment), catalyst samples of varying Ni contents were made.
• the Ni contents of the catalyst samples were 3.8, 7.5 and 10.9 wt. %, respectively.
• the carbon content (formed by possibly remaining ligands) in all catalyst samples was below the detection threshold and the nickel species were well dispersed in all catalysts as the catalysts were XRD amorphic (having a Ni compound particle size less than 20 A) with respect to Ni compounds.
• the above-described analysis results are proof of an extremely successful impregnation.
• catalysts samples were made from the same Ni compound (Ni(acac) 2 ) onto identical alumina support by way of both dry impregnation and a method according to the invention directly from vapor phase.
• Catalyst # 1 (cf. Table 1), manufactured in the method according to the invention by cyclically introducing Ni(acac) 2 onto alumina substrate from vapor phase until an Ni content of 10.1 wt. % was attained, and a catalyst made in the above-described impregnation method by bonding Ni(acac) 2 from a solution onto identical alumina substrate as was used in the manufacture of Catalyst # 1.
• This impregnated catalyst (IMP / acac) had an Ni content of 10.9 wt. %.
• the first test was performed to compare the conversion efficiency of two catalysts (#1 and #4) made from vapor phase with that of a commercial-grade catalyst of approximately equivalent Ni content. The comparison was made in gas-phase test conditions at 175 °C temperature, a molar ratio of approx. 3.1 of H 2 to toluene and WHSV of approx. 90.
• the fourth test was performed to compare the reaction rates attainable with a commercial-grade catalyst (Commercial #3) and a novel catalyst (#2) made from vapor phase in differential conditions of gas phase at different temperatures.
• Table 5 gives the reaction rates at different temperatures as conversion rate of methylcyclohexane (MECH) per hour and gram of catalyst, and respectively, gram of Ni.
• the partial pressure ratio Pjc P to i ueoc was approx. 2,2. Table 5.
• the catalysts according to the invention in multiple cases provide superior activity over three commercial-grade catalysts and one impregnated reference catalyst manufactured by the inventor.
• the support material of the catalyst here was same aluminum oxide as in Example 1.
• the support was pretreated at 800 °C.
• the reagent used was commercial-grade nickelocene, Ni(C 5 Hj) 2 .
• Vaporization temperature of nickelocene in the catalysts of this example was 150 °C and the reaction temperature at which the nickel species were chemisorbed onto the Al 2 O 3 support was 200 °C.
• the reaction time was 4 h.
• the hydrocarbon ligands of nickelocene were removed with the help of moist air.
• the air treatment was carried out at 200 °C for 2 h and at 400 °C for 4 h. Finally the catalyst was purged with nitrogen at 400 °C for 1 h.
• Table 6 lists 3 catalysts manufactured in the above-described manner.
• the column "No. of repetition cycles" in the table indicates the number of repetition cycles for the above-mentioned nickelocene/air treatment steps.
• Catalysts #8, #9 and #10 had a carbon content which was below the detection threshold of less than 0.1 wt. % .
• Example 7 The activities of the catalysts made according to Example 7 were compared with Catalysts #1 and #4 as well as the Commercial catalyst #1. The comparison was carried out in differential conditions, for hydrogenation of toluene, at approx. 4 % conversion at ambient pressure and 175 °C temperature. The molar ratio of H 2 to toluene in feedstock was approx. 2.5, corresponding to a thermodynamical equilibrium conversion of approx. 45 %. Table 7 gives the reaction rate of toluene after a 4-hour run (stabilized state) as the amount of produced methylcyclohexane per gram of catalyst and 1 h, as well as per gram of catalytic nickel and 1 h. The catalysts are rated in column 4 for functionality according to their catalytic performance and nickel content. Table 7. Reaction rate in hydrogenation of toluene for different catalysts
• nickelcyclopentadienyl is well suited for use as the precursor in the manufacture of a hydrogenation catalyst.

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• 1992
  • 1992-07-09 FI FI923169A patent/FI90632C/sv active IP Right Grant
• 1993
  • 1993-07-09 EP EP93914766A patent/EP0649344A1/en not_active Ceased
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