NO20023229L - Hydrocarbon synthesis catalyst improvement with hydrogen and ammonia - Google Patents

Description

IMPROVEMENT OF CATALYST FOR HYDROCARBON SYNTHESIS WITH HYDROGEN AND AMMONIA

BACKGROUND OF THE INVENTION

The subject area of the invention

The invention concerns the improvement of a catalyst for a hydrocarbon synthesis with hydrogen and ammonia. More particularly, the invention relates to an improvement of a hydrocarbon synthesis catalyst, including a Fischer-Tropsch type hydrocarbon synthesis catalyst, by contacting the catalyst with a reducing gas comprising a mixture of hydrogen and ammonia, under catalyst reducing conditions, and a process with a hydrocarbon synthesis using the improved catalyst.

Background for the discovery

The synthesis of hydrocarbons, including oxygenated hydrocarbons such as methanol, from a synthesis gas comprising a mixture of H 2 and CO is well known. The synthesis gas feed is contacted with a Fischer-Tropsch catalyst at conditions effective for the H2 and CO in the gas feed to react and form hydrocarbons. The synthesis is known as a Fischer-Tropsch hydrocarbon synthesis. Depending on the catalyst and conditions, the hydrocarbons can vary from oxygenated compounds such as methanol and higher molecular weight alcohols to high molecular weight paraffins which are wax-like solids at room temperature. The process also produces smaller quantities of alkenes, aromatics, organic acids, ketones, aldehydes and esters. The synthesis is carried out in a reactor with solid or fluidized catalyst or in a liquid-phase slurry reactor. Hydrocarbon synthesis catalysts are also well known and typically comprise a composite with at least one catalytic metal component from the iron group on a support of, or composite with, at least one inorganic refractory metal oxide as support material, such as aluminum oxide, amorphous silica-alumina, zeolites and the like. Various catalyst preparation methods have been used to form hydrocarbon synthesis catalysts, including impregnation, initial wetting, compositing, ion exchange and other known techniques, to form a catalyst precursor. The precursor must be activated to yield the catalyst. Typical activation methods include oxidation or calcination, followed by reduction in a hydrogen stream, multiple oxidation-reduction cycles, and reduction without prior oxidation. Examples of catalyst preparation and activation methods for Fischer-Tropsch hydrocarbon synthesis catalysts are disclosed in, for example, US Patents US 4,086,262; 4,492,774 and 5,545,674.

SUMMARY OF THE INVENTION

The invention relates to increasing or improving the performance of an active hydrocarbon synthesis catalyst, including a Fischer-Tropsch type hydrocarbon synthesis catalyst, by contacting the catalyst with a reducing gas comprising a mixture of hydrogen and ammonia, under conventional reducing conditions for a catalyst , effective in providing an active catalyst and a hydrocarbon synthesis process using the improved catalyst. By catalyst is meant an active hydrocarbon synthesis catalyst where at least a part, and preferably only a part, of the one or more catalytic metals (e.g. Co, Fe, Ni) is in the reduced or catalytically active metal form, as a due to the reduction achieved by allowing the catalyst precursor to be in contact with a hydrogen-reducing gas without ammonia, under conventional hydrogen-reducing conditions. Thus, while the catalyst may be fully reduced and fully active prior to contact with the hydrogen and ammonia mixture in the practice of the invention, it is preferred that it be partially reduced in hydrogen without ammonia and partially reduced in a reducing gas comprising hydrogen and ammonia, to obtain complete reduction and activation. It has been found that contacting the catalyst with a reducing gas comprising a mixture of hydrogen and ammonia improves the hydrocarbon synthesis properties of the resulting active catalyst, with respect to at least one of; increased C5+ selectivity, increased alpha (Schultz-Flory alpha) of the synthesis reaction, and a reduction of the methane produced. These advantages are unexpected, considering the fact that ammonia is a well-known catalyst poison in hydrocarbon syntheses. Thus, with an improved catalyst, in the context of the invention it is intended that at least one, preferably at least 2, and more preferably all three of the following are achieved during the hydrocarbon synthesis: the C5+ selectivity of the catalyst is greater than it would otherwise be if the catalyst were not had been in contact with a reducing gas comprising a mixture of hydrogen and ammonia; (ii) the alpha of the synthesis reaction is greater than it would be if the catalyst had not been in contact with a reducing gas comprising a mixture of hydrogen and ammonia, and (iii) the amount of methane is reduced to a level lower than it would otherwise be if the catalyst had not been in contact with a reducing gas comprising a mixture of hydrogen and ammonia.

The catalyst precursor may or may not be calcined prior to activation by reduction. One or both of the hydrogen reducing gas and the reducing gas comprising the mixture of hydrogen and ammonia may or may not contain one or more diluting gases which have no adverse effect or adversely affect the reduction or simultaneous activation of the catalyst. Such gases include methane, argon or the like. The amount of ammonia present in the hydrogen reducing gas will vary widely from 0.01 to 15 mol %, preferably from 0.01 to 10 mol %, more preferably from 0.1 to 10 mol %, and even more preferably from 0.5 to 7 mol %, based on the total gas mixture. The hydrogen to ammonia molar ratio will vary from 1000:1 to 5:1 and preferably from 200:1 to 10:1.

In one embodiment, the invention is a process comprising the improvement of a Fischer-Tropsch type hydrocarbon synthesis catalyst, comprising at least one catalytic metal component, and preferably at least one catalytic metal component and a support type component of a metal oxide, by allowing the catalyst to be in contact with a reducing gas comprising a mixture of hydrogen and ammonia, under catalyst-reducing conditions effective to reduce the one or more catalytic metal components to the reduced, catalytically active metallic form, and preferably wherein a portion of the one or more of the catalytic metal components is reduced to the catalytically active form as a result of the contact. In another embodiment, the invention comprises a process for synthesizing hydrocarbons from a synthesis gas comprising a mixture of H2 and CO, where the synthesis gas comes into contact with an improved Fischer-Tropsch type hydrocarbon synthesis catalyst, under reaction conditions effective for H2 and CO in the gas to react and form hydrocarbons, wherein the improved catalyst comprises a composite of at least one catalytic metal component and a metal oxide as a support component, and it has been improved by contacting the catalyst with a reducing gas comprising a mixture of hydrogen and ammonia, under reducing conditions of the catalyst effective to reduce the one or more catalytic metal components to the reduced, catalytically active metal form, and preferably where part of the one or more catalytic metal components is reduced to the catalytically active metal form as a result of the contact. In yet another embodiment, at least a portion of the synthesized hydrocarbons are liquid at the reaction conditions. By conventional catalyst reducing conditions are meant conditions with respect to temperature, pressure, hydrogen partial pressure and space velocity of a conventional reducing hydrogen gas, sufficient to reduce one or more catalytic metal components in the precursor to metal and provide an active catalyst.

DETAILED DESCRIPTION

Hydrocarbon synthesis catalysts are well known and a typical Fischer-Tropsch hydrocarbon synthesis catalyst will comprise, for example, catalytically effective amounts of one or more Group VIII metal catalytic components such as Fe, Ni, Co and Ru. Preferably, the catalyst comprises a catalyst on a carrier, where one or more carrier components for the catalyst will comprise an inorganic refractory metal oxide. Metal oxide carrier components are preferably one that is difficult to reduce, such as an oxide of one or more metals in Groups III, IV, V, VI, and VII. The metal groups referred to here are those found in the Sargent-Welch Periodic Table of the Elements,<®>1968. Typical carrier components include one or more of alumina, silica, and amorphous and crystalline aluminosilicates, such as zeolites. Particularly preferred carrier components are Group IVB metal oxides, especially those having a surface area of 100 m<2>/g or less and even 70 m<2>/g or less. These carrier components can, in turn, be supported by one or more carrier materials. Titanium dioxide, and especially rutile titanium dioxide, is a preferred carrier component, especially when the catalyst contains a cobalt catalytic component. Titanium dioxide is a useful component, particularly when using a slurry hydrocarbon synthesis process, in which higher molecular weight, primarily paraffinic, liquid hydrocarbon products are desired. In some cases, in which the catalyst comprises catalytically effective amounts of Co, it will also comprise one or more components or compounds of Re, Ru, Fe, Ni, Th, Zr, Hf, U, Mg and La, some of which are effective as promoters. A combination of Co and Ru is often preferred. Useful catalysts and their preparation are known and illustrative but not limiting examples can be found, for example in the US. - patents 4,568,663; 4,663,305; 4,542,122; 4,621,072 and 5,5545,674.

The catalysts are prepared by any suitable and known method, such as impregnation, initial wetting, ion exchange, crushing, precipitation or coprecipitation, melt deposition, or any other composite technique to provide the catalyst precursor. The catalytic metal component is typically applied as a solution of a compound that decomposes during the subsequent calcination and/or reduction. For example, a cobalt component is typically applied as a nitrate salt. It is not uncommon to calcine the precursor after each application of the reducible catalytic metal compound, in order to achieve better catalytic metal dispersion. After forming and extruding the precursor composite, it is typically pelletized and dried. The precursor is then reduced, or calcined and reduced, to give the catalyst. The reduction is accomplished by contacting the precursor with flowing hydrogen or a hydrogen-reducing gas, under conditions effective to reduce the catalytically active metal component (eg, cobalt) to the metal form. A common method is known as the R-O-R method, in which the precursor is reduced in hydrogen, then calcined, followed by reduction again. As mentioned above, the reducing hydrogen gas can be pure (only hydrogen), or mixed with one or more diluting gases (eg methane, argon) which are inert to the reduction. In the practice of the invention, the R-O-R method can also be used, and a conventional hydrogen reducing gas used in the first and at least part of the second reduction, and preferably with part of the final reduction achieved with a reducing gas comprising a mixture of hydrogen and ammonia. Typical reducing conditions effective to form the catalyst comprising the reduced metal component on the support from the precursor range from M to 24 hours, 200-500°C, 1-100 bar, and a GHSV of 50-10000. The actual conditions will depend on the hydrogen concentration in the reducing gas, as well as the metal to be reduced and its precursor form (eg salt or oxide). In the catalyst improving process according to the invention, the at least partially reduced and active catalyst is allowed to come into contact with a mixture of a hydrogen-reducing gas and ammonia, under typical reducing conditions as presented above, corresponding to those used for normal reduction and simultaneous activation. The catalyst improvement can be carried out in accordance with the process according to the invention, either before it is loaded onto the hydrocarbon synthesis reactor or in-situ in the hydrocarbon synthesis reactor.

The improved catalyst can be used in either a fixed bed, a fluidized bed or in hydrocarbon synthesis slurry processes, to provide hydrocarbons from a synthesis gas comprising a mixture of H 2 and CO. These processes are well known and documented in the literature. In all these processes, the synthesis gas is allowed to come into contact with a suitable Fischer-Tropsch type hydrocarbon synthesis catalyst, under reaction conditions effective for H2 and CO in the gas to react and produce hydrocarbons. Depending on the process, catalyst and synthesis reaction variables, some of these hydrocarbons will be liquid, some solid (e.g. wax) and some gaseous at standard room conditions such as a temperature of 25 °C and a pressure of one atmosphere, especially if used a catalyst with a catalytic cobalt component. In a hydrocarbon synthesis process with a fluidized bed, all the products are steam or gas at the reaction conditions. In solid bed and slurry processes, the reaction products will include hydrocarbons that are both liquid and gaseous under the reaction conditions. Slurry hydrocarbon synthesis processes are sometimes preferred because of their superior heat (and mass) transfer characteristics for the highly exothermic synthesis reaction and because they are capable of producing relatively high molecular weight paraffinic hydrocarbons when a cobalt catalyst is used. In a hydrocarbon synthesis slurry process, a synthesis gas comprising a mixture of H2 and CO is bubbled up as a third phase through a slurry in a reactor comprising a particulate Fischer-Tropsch type hydrocarbon synthesis catalyst dispersed and suspended in a liquid slurry comprising hydrocarbon products of the synthesis reaction which are liquid at the reaction conditions. The molar ratio of hydrogen to carbon monoxide in the synthesis gas can vary widely from about 0.5 to 4, but is more typically within the range of from about 0.7 to 2.75 and preferably from about 0.7 to 2.5. The stoichiometric mole ratio for a Fischer-Tropsch hydrocarbon synthesis reaction is 2.0, but it can be increased to obtain the amount of hydrogen desired by the synthesis gas for other than the hydrocarbon synthesis reaction. In a hydrocarbon synthesis slurry process, the molar ratio of H2 to CO is typically about 2.1/1. The reaction conditions effective for the various hydrocarbon synthesis processes will vary somewhat, depending on the type of process, catalyst composition and desired products. Typical conditions effective to provide hydrocarbons comprising predominantly C5+ paraffins (e.g. C5+-C200) and preferably C10+ paraffins, in a slurry process using a catalyst comprising a cobalt component on a support include, for example, respectively tempera -trips, pressures and gas space velocities per hour in the range from 160-315 °C, 5.5-41 bar and 100-40,000 V/hr/V, expressed as standard volumes of the gaseous CO and H2 mixture

(0°C, 1 atm) per hour per volume catalyst. These conditions can nominally also be applied to the other processes.

Hydrocarbons produced by a hydrocarbon synthesis process in accordance with the practice of the invention are typically upgraded to more valuable products by subjecting all or part of the C5+ hydrocarbons to fractionation and/or conversion. By conversion is meant one or more operations where the molecular structure of at least part of the hydrocarbon is changed and includes both non-catalytic process treatment (e.g. steam cracking) and catalytic processes (e.g. catalytic cracking) where a fraction comes into contact with a suitable catalyst. If hydrogen is present as a reactant, such process steps are typically referred to as hydroconversion and include, for example, hydroisomerization, hydrocracking, hydrowaxing, hydrorefining, and the more stringent hydrorefining referred to as hydrotreating, all conducted under conditions well known in the hydroconversion literature hydrocarbon feeds, including hydrocarbon feeds rich in paraffins. Illustrative, but not limiting, examples of more valuable products obtained by conversion include one or more of a synthetic crude oil, liquid fuel, olefins, solvents, lubricating industrial and medical oils, waxy hydrocarbons, nitrogen and oxygen containing compounds, and the like. Liquid fuel includes one or more of motor gasoline, diesel oil, jet fuel, and kerosene, while lubricating oil includes, for example, automotive, jet, turbine, and metalworking oils. Industrial oils include drilling mud, oils for agricultural purposes, fluids for heat transfer and the like.

The invention will be further understood with reference to the examples below.

EXAMPLES

Example 1 (Silica carrier)

A commercially available silica gel known as KCKG #4 (manufactured by the Salavat Catalyst Factory of the Salavat Petrochemical Complex, Salavant, Russia), 2-4 mm diameter, was ground and sieved to obtain a 0.106-0.250 mm size fraction. This material was then calcined in an air stream at 450°C for 5 hours to provide the support for the catalysts prepared below.

Example 2 (Catalyst A precursor)

A solution of 5.18 g of Co(NO 3 ) 2<*>6H 2 O in distilled water was prepared. This solution was added to 21 ml (8.38 g) of the calcined silica support from Example 1 with stirring to provide a catalyst precursor. The catalyst precursor was then dried on a steam bath. At this stage, the catalyst precursor contained nominally 11% by weight of cobalt and is catalyst A precursor.

Example 3 (Catalyst B precursor)

An aqueous solution of 4.9 g of ZrO(NO3)2<*>2H20 was added to 33.2 g of the calcined silica support from Example 1, in a volume of water sufficient to completely wet the silica, which was then dried over a steam bath, followed by calcination in an air stream for 1 hour at 450°C to a first composite. Then a solution of 75 g of Co (N0 3 ) 2*6H 2 O in 30 ml of water was added to the composite which was immersed for 2 hours at room temperature. The excess solution was decanted away and saved. The resulting second composite was dried on a steam bath and then calcined in an air stream for 2 hours at 450°C. After cooling, excess solutions that were saved were added to the second composite. The steps of immersion, decantation, drying and calcination were repeated until all of the Co(NO 3 ) 2<*>6H 2 O solution was impregnated into the composite to give the final catalyst precursor, which is catalyst B precursor. The catalyst B precursor thus formed contained 27% by weight of cobalt and 4.1% by weight of zirconium oxide.

Example 4 (Catalyst B reduction in H2)

The catalyst B precursor from Example 3 (20 ml) was mixed with 80 ml of 1-3 mm quartz particles and the mixture placed in a 25 mm ID quartz reactor. The catalyst/quartz mixture was held in place with glass wool at the bottom of the reactor, and a layer of 10 mm particles on top of the catalyst/quartz mixture. Hydrogen was then passed through the reactor at room temperature and atmospheric pressure at a gas hourly space velocity (GHSV) of 100 hr<-1> for 15 minutes. Before entering the reactor, the hydrogen was passed through a column of KOH pellets (pellet diameter nominally 3-5 mm) to remove impurities. The reactor temperature was increased to 450 °C over 40-45 minutes. This condition was maintained for 5 hours. The reactor was then allowed to cool down to room temperature in a hydrogen stream. After the reactor was cooled, the hydrogen stream was replaced with a stream of 2:1 H2:C0 synthesis gas at 100 hr"<1>GHSV, for 15 minutes at atmospheric pressure. As with the hydrogen, the synthesis gas was passed through a column of KOH pellets for removal of the contaminants The valves were then closed at the inlet and outlet of the reactor as the catalyst was stored under the synthesis gas.

Example 5 (Catalyst B reduction in H2 and then NH3/H2)

A 20 ml sample of the catalyst B precursor from Example 3 was mixed with 80 ml of 1-3 mm quartz particles and the mixture placed in a 25 mm ID quartz reactor. The catalyst/quartz mixture was held in place with glass wool in the bottom of the reactor, and a layer consisting of 10 ml of the 1-3 mm quartz particles was placed on top of the catalyst/quartz mixture. Hydrogen was then passed through the reactor at room temperature and atmospheric pressure at a gas per hour space velocity (GHSV) of 100 hr"<1> for 15 minutes. Before entering the reactor, the hydrogen was passed through a column of KOH pellets (pellet diameter nominally 3-5 mm) to remove contaminants and through a 3-necked flask containing NaOH pellets. The center neck of the 3-necked flask was fitted with a syringe for the addition of 29 wt% NH3/71 wt% H20 solution. NaOH' one in the 3-necked flask served to absorb the water from the NH3/H20 solution, releasing NH3 vapor, which is then flushed out of the flask and into the reactor.The reactor temperature was raised to 400°C over 40-45 minutes. In the preparation of the catalysts, the procedure used in Example 4 was used (where the reactor temperature was increased from room temperature to 450 °C over 40-45 minutes and held at 450 °C for 5 hours) until the reactor reached 450 °C in temperature. This was followed by 5 hour reduction (i) with H2 only for the first sample, (ii) with H2 followed by a mixture of H2 and NH3 for the next four samples and (iii) with a mixture of H2 and NH3 only for the fifth sample, as shown in Table 2 below. Ammonia addition to the H 2 gas to produce the H 2 /NH 3 reducing gas mixture was achieved by a continuous dropwise addition of the 29 wt % NH 3 /71 wt % H 2 O solution from the syringe. The nominal concentration of NH3 in the reducing gas during the addition of the NH3/H20 solution was 5 mol%. Regardless of whether the reduction was achieved with (i) only H2, (ii) H2 followed by H2/NH3, or (iii) only H2/NH3, the total reduction time was 5 hours as shown in Table 2. Following the reduction, the reactor was allowed to cool down to room temperature in a hydrogen stream. After the reactor was cooled, the hydrogen stream was replaced by a stream of 2:1 H2:CO synthesis gas at 100 hr"<1>GHSV for 15 minutes at atmospheric pressure. As with the hydrogen, the synthesis gas was passed through a column of KOH pellets to remove impurities The valves were then closed at the inlet and outlet of the reactor, the catalyst being stored under the synthesis gas.

Example 6 (Catalyst A reduction with NH3/H2

A 20 ml sample of the catalyst A precursor from Example 2 was mixed with 80 ml of 1-3 mm quartz particles and the mixture placed in a 25 mm ID quartz reactor. The catalyst/quartz mixture was held in place with glass wool at the bottom of the reactor and a layer consisting of 10 ml of the 1-3 mm quartz particles on top of the catalyst/quartz mixture. Hydrogen was then passed through the reactor at room temperature and atmospheric pressure at a gas hourly space velocity (GHSV) of 3,000 hr<-1> for 15 minutes. Before entering the reactor, the hydrogen was passed through a column of KOH pellets (pellet diameter nominally 3-5 mm) to remove impurities and through a 3-necked flask containing NaOH pellets. The center neck of the 3-neck flask was equipped with a syringe for the addition of a 29 wt% NH3/71 wt% H20 solution. The NaOH in the 3-necked flask served to absorb the water from the NH3/H20 solution, releasing NH3 vapor which was then flushed out of the flask and into the reactor. The reactor temperature was increased to 400°C over 40-45 minutes. After reaching 400°C, dropwise addition of the 29 wt% NH 3 /71 wt % H 2 O solution was started from the syringe. The rate of addition was varied to give a nominal concentration of NH 3 in the reducing gas of between 9 (H 2 only) and 3.0 mole %. This condition was maintained for 1 hour. The reactor was then allowed to cool down to room temperature in a hydrogen stream. After the reactor was cooled, the hydrogen stream was replaced with a stream of 2:1 H2:C0 synthesis gas at 100 hr"<1>GHSV for 15 minutes at atmospheric pressure. As with the hydrogen, the synthesis gas was passed through a column of KOH pellets to remove contaminants The valves were then closed at the inlet and outlet of the reactor, the catalyst being stored under the synthesis gas.

Example 7 (Test of Catalyst A)

The flow of synthesis gas into the reactor was resumed with the catalyst from Example 6 (Catalyst A reduced with H2+ NH3) at 100 hr"<1>GHSV and 1 atm. pressure. Before entering the reactor, the synthesis gas was passed through a column of KOH pellets (pellet diameter nominally 3-5 mm) for the removal of impurities. The composition of the synthesis gas was 2:1 H2:CO on a volume basis. The reactor temperature was raised from room temperature to 160 °C in about 40 minutes. This condition was maintained for 5 hours, and after this the reactor was cooled to room temperature in the flow of synthesis gas and the catalyst was stored under the synthesis gas as described in Example 6. The test was repeated the next day following the same procedure, except that the test temperature was

10 °C higher. This was repeated every day until the optimum operating temperature was found. The optimal operating temperature was defined as the temperature at which the yield of C5+ products is maximum, as measured in g C5+ products per standard cubic meters of synthesis gas fed into the reactor. Finding the optimum operating temperature involved increasing the reactor temperature in 10°C increments until the C5+ yield decreased from the previous trial. The temperature from the previous test is the optimum temperature. Catalyst performance was determined by measuring gas contraction, gas composition

of the product by gas chromatography, and the yield of liquid C5+ products. The liquid C5+ product was recovered from the reactor discharge using two traps. The first trap was water-cooled and the second was cooled with dry ice/acetone (-80 °C). The C5+ product in the first trap was weighed directly. The liquid product in the second trap was first heated

to room temperature to evaporate the C4 components before weighing. The combined weights of the liquid hydrocarbon product in both traps were used to determine the C5+ product yield. The C5+ product from the optimum temperature was further analyzed to determine hydrocarbon type and carbon chain length distribution. From time to time, the C5+ products from the non-optimal products were combined and analyzed. The catalyst precursor was not calcined prior to the reduction in these experiments. The results are shown in Table 1 below.

These results demonstrate the effect on catalyst performance of the NH3 concentration in the reducing gas used to convert the precursor to the catalyst. Up to about 2 mol % NH3 in the reducing gas, both the % CO conversion and the C5+ yields are good, with the peak of the C5+ selectivity at about 80%. Although the catalyst activity decreases when NH 3 was used in the reducing gas, the reduction is mainly of C 4 . gas products. The Schultz-Flory alpha also increased when the catalyst reducing gas contained NH 3 and remained practically constant from 0.5 to 3.0 mole % NH 3 in the reducing gas. These results show that the presence of NH3 in the reducing gas during the catalyst reduction enhanced the alpha of the hydrocarbon synthesis reaction. The biggest difference between having or not having NH3 in the reducing gas is seen in the run where the H2 reducing gas contained 0.5 mol% NH3. This produced a C5+ selectivity of 76%, with a high yield of C5+ hydrocarbons and only 9% methane produced. At 2 mol% NH3 the C5+ selectivity was even higher and the Cs+ yield, although lower, was still good.

Example 8 (Catalyst B test after reduction with H2

and then with H2+ NH3)

The flow of synthesis gas was resumed in the reactor with the catalyst from Example 5 (Catalyst B reduced first with H2 and then with H2+ NH3) at 100 hr"<1>GHSV and 1 atm. pressure. Before entering the reactor, the synthesis gas had passed through a column with KOH pellets (pellet diameter nominally 3-5 mm) to remove impurities. The composition of the synthesis gas was 2:1 H2: CO by volume. The reactor temperature was increased from room temperature to 160 °C for about 40 minutes. This condition was maintained for 5 hours, and then the reactor was cooled to room temperature in the flowing synthesis gas and the catalyst stored under the synthesis gas. Testing was resumed the next day following the same procedure, except that the test temperature was 10 °C higher. This was repeated every day until the operating temperature was 190 °C. At 190 °C, the catalyst performance was determined by measuring the gas contraction, the gas composition of the product by gas chromatography, and the yield of liquid C5+ products. skein was recovered from the reactor's discharge by using two traps. The first trap was water-cooled, and the second was cooled with dry ice/acetone (-80 °C). The C5+ product in the first trap was weighed directly. The liquid product in the second trap was first warmed to room temperature to vaporize the C4. the components before weighing. The combined weights of the liquid hydrocarbon products in both traps were used to determine the yield of the C5+ product. The C5+ product from the optimum temperature was further analyzed to determine the hydrocarbon type and chain length distribution for the carbon. From time to time, the C5+ products from the non-optimal temperature samples were combined and analyzed. The catalyst precursor used in these experiments was calcined prior to the reduction. It should be noted that while the cobalt oxide formed in the calcination is converted to metal during the reduction, the zirconium component remains as the oxide and is not reduced to metal. The results at 190 °C are shown in Table 2 below.

Table 2 shows how, at a constant reducing time of 5 hours, the performance of Catalyst B is influenced by the presence of NH3 in the H2 reducing gas, when it is sequentially reduced with H2 followed by H2+NH3, and also when it was only reduced in H2+NH3. It should be noted that the tests revealed optimal catalytic properties for the catalyst reduced under hydrogen at a hydrogen synthesis gas ratio of 100 hr"<1>GHSV and was achieved at a reduction time of 5 hours. This is why the total reduction of 5 hours was chosen in this experiment. Thus, an active catalyst existed before the contact with the hydrogen and ammonia reducing gas, for the runs in Table 2 above, in which the contact time with hydrogen was 1, 2, 3 and 4 hours. In the last run in the table, there was a precursor which was in contact with the hydrogen and ammonia mixture for 5 hours Thus, this last run and the first run with only hydrogen reduction are not within the scope of the invention and are presented only for the sake of comparison.

As Table 2 shows, in the second to fifth runs, the precursor was at least partially reduced prior to contact with the hydrogen and ammonia mixture. With 4 hours on H2 followed by just 1 hour on H2 and NH3, you got a sharp increase in the C5+ yield and selectivity and a simultaneous sharp drop in methane produced. Thus, increasing the reduction time with H2+NH3 caused the C5+ yield, C5+ selectivity, and Schulz-Flory's alpha to peak, after between 2 and 4 hours of H2+NH3 reduction. Although the catalyst activity falls with increasing H2+NH3 reduction time, the drop in activity is taken from the C4 gas, as the yield of C5+ is left approximately constant up to three hours of H2/NH3 treatment. After more than three hours, the C5+ yield and selectivity decreased, but the alpha of the reaction remained high. This shows that the introduction of NH3 into the reducing gas during at least part of the catalyst reduction is effective in improving the catalyst's performance.

It is understood that various other embodiments and modifications in the practice of the invention will be apparent to, and can be readily made by, those skilled in the art without departing from the spirit and scope of the invention described above. Accordingly, it is not intended that the scope of the claims appended hereto be limited to the precise description set forth above, but rather that the claims be construed to include all features of patentable novelty inherent in the present invention, including all features and the embodiments which will be treated as equivalent to these by those skilled in the art to which the invention relates.

Claims (20)

1. Process for improving the performance of a hydrocarbon synthesis catalyst comprising contacting said catalyst comprising at least one catalytic metal component with a reducing gas comprising a mixture of hydrogen and ammonia, under catalyst reducing conditions. 2. Process according to claim 1 wherein during the hydrocarbon synthesis, said improved catalyst exhibits at least one property selected from the group consisting of (i) a C5+ selectivity greater than it would otherwise be if said catalyst had not been improved with said hydrogen and ammonia reducing gas mixture, (ii) a hydrocarbon synthesis reaction alpha greater than it would otherwise be if said catalyst had not been enhanced with said hydrogen and ammonia reducing gas, and (iii) methane produced reduced to a level lower than it would otherwise be if said catalyst had not had been improved with said hydrogen and ammonia reducing gas. 3. Process according to claim 2 in which said catalyst comprises a Fischer-Tropsch type hydrocarbon synthesis catalyst. 4. Process according to claim 3 in which a part of at least one catalytic metal component is reduced to the catalytically active metal form, as a result of said contact with said hydrogen and ammonia reducing gas. 5. Process according to claim 4 in which said catalyst also comprises a metal oxide as carrier component and in which said catalytic metal component comprises at least one Group VIII metal. 6. Process according to claim 5 in which a part of said at least one catalytic metal component is reduced to the catalytically active metal form, as a result of the reduction in hydrogen without said ammonia. 7. Process according to claim 6 in which said ammonia is present in said hydrogen reducing gas in an amount of from 0.01 to 15 mol% of the total reducing gas composition. 8. Process according to claim 7 in which the hydrogen to ammonia molar ratio in said reducing gas comprising a mixture of hydrogen and ammonia varies from 1000:1 to 5:1. 9. Process according to claim 8 in which said catalytic metal component comprises at least one of Co and Ru and in which said carrier component comprises at least one selected from the group consisting of aluminum oxide, silica, aluminosilicates and titanium dioxide. 10. Catalyst produced according to the process in claim 1. 11. Process for synthesizing hydrocarbons from a synthesis gas comprising a mixture of H2 and CO, wherein said gas is contacted with an improved Fischer-Tropsch hydrocarbon synthesis catalyst under reaction conditions effective for said H2 and CO in said gas to react and form hydrocarbons , wherein said improved catalyst comprises at least one catalytic metal component, and where said catalyst has been improved by contact between said catalyst and a reducing gas comprising a mixture of hydrogen and ammonia under reducing conditions for the catalyst. 12. Process according to claim 11 wherein, during the hydrocarbon synthesis, said improved catalyst exhibits at least a property selected from the group consisting of (i) a C5+ selectivity greater than it would otherwise be if said catalyst had not been enhanced with said hydrogen and ammonia reducing gas mixture, (ii) a hydrocarbon synthesis reaction alpha greater than it would otherwise be if not said catalyst had been enhanced with said hydrogen and ammonia reducing gas mixture, and (iii) produced methane reduced to a level lower than it would otherwise be if said catalyst had not been enhanced with said hydrogen and ammonia reducing gas mixture. 13. Process according to claim 12 in which said catalyst also comprises a metal oxide as carrier component and in which said catalytic metal component comprises at least one Group VIII metal. 14. Process according to claim 13 in which a part of said at least one catalytic metal component is reduced to the catalytically active metal form, as a result of said contact with said hydrogen and ammonia reducing gas. 15. Process according to claim 14 in which a part of said at least one catalytic metal component is reduced to the catalytically active metal form, as a result of a reduction in hydrogen without said ammonia. 16. Process according to claim 15 in which said ammonia is present in said hydrogen reducing gas in an amount of from 0.01 to 15 mol% of the total reducing gas mixture and where said hydrogen to ammonia molar ratio in said reducing gas varies from 1000:1 to 5:1. 17. Process according to claim 16 where said carrier component includes at least one selected from the group consisting of aluminum oxide, silica, aluminosilicates and titanium dioxide. 18. Process according to claim 19 in which said activated catalyst is in a fluidized bed, a solid bed or dispersed in a liquid slurry during said hydrocarbon synthesis and in which at least part of said synthesized hydrocarbons is upgraded in one or more operations comprising fractionation and/ or one or more conversion operations. 19. Process according to claim 18 in which at least part of said hydrocarbons which are upgraded are solid under standard conditions with regard to room temperature and pressure. 20. Slurry hydrocarbon synthesis process according to claim 19 in which said catalytic metal component comprises at least one of Co and Ru.