Title of Invention

"AN IMPROVED STEAM REFORMING CATALYST AND PROCESS FOR PRODUCTION THEREOF"

Abstract

In the steam reforming catalysts for hydrocarbons according to the present invention, the active catalytic component is supported on a carrier material which is selected from a group consisting of zirconia, alumina, magnesia, silica, calcium oxide, lanthana, ceria and compounds or mixtures thereof. The catalyst can be operated with a wide range of hydrocarbon feed stocks, for instance natural gas to kerosene at various temperature and steam to carbon ratio. The catalyst in which zirconia is added as one of the support materials was most effective for adiabatic steam reforming of light and heavy hydrocarbon feed stocks upto kerosene. The zirconia containing catalyst exhibited higher activity, lower carbon deposition, high thermal stability and high retained mechanical strength even for operation with heavy feed stocks in the inlet temperature range 400-550°C and lower steam to carbon ratios. Presence of cobalt or palladium exhibited a promoting effect towards improving the activity in the inlet temperature range 380-420°C.

Full Text

FIELD OF INVENTION This invention relates to a NICKEL containing catalyst for pre-reforming Background of the invention Light and heavy hydrocarbon feed stocks upto kerosene can be reformed with steam at low as well as high temperature/steam to carbon ratio. The main reactions occuring during the production of hydrogen rich gases are steam reforming , water gas shift, methanation and several carbon forming reactions. The carbon forming reactions are detrimental for the performance of the catalyst. The activity of the catalyst is reduced due to blockage of active sites by carbon deposition. In addition to this, the pore structure of the catalyst is damaged resulting in weakening of the pellets which leads to pressure drop across the catalyst bed. Hence choice of suitable supports and promoters play a vital role in controlling activity and coke resistance properties of the catalyst. Prior publication disclose a combination of nickel oxide and various supports have been extensively investigated for steam hydrocarbon reforming. A refractory carrier material selected from the group consisting of alumina, magnesia, titania, silica, zirconia, beryllia, thoria, lanthana, calcium oxide and compounds or mixtures thereof has been used for the preparation of supported nickel catalyst for steam reforming to produce hydrogen or carbon monoxide rich gases.(US 5595719, US 5595517). A method of contacting hydrocarbon with a two part catalyst comprising a dehydrogenation portion and an oxide ion conducting portion to form an oxide was reported . Ceria is the oxide ion conduction material and platinum is the hydrogen dissoving material. Other oxide ion conducting materials such as zirconia, bismuth oxides and perovskite type compounds are also referred (US 5929286). Catalyst metal-rhodium, ruthenium, palladium and platinum or mixture of these items supported on yttria stabilised zirconia exhibits higher reaction efficiency and suppresses carbon deposition even when steam to carbon ratio is low. It is recommended that this catalyst is more suitable for internal reforming fuel cell than conventional type reforming catalysts because catalyst metal is supported on zirconia carrier which contains yttria as a stabiliser. Partially stabilised zirconia has a high oxygen ionic conductivity which may be related to the activation of oxygen ions in water or to the effect to suppress coking. Steam reforming catalyst for hydrocarbon with high mechanical strength can be obtained if yttria stabilised zirconia is used as a support (US 5075277). Indian Patent 675/DEL/98 discloses a catalyst having nickel as the active component and a carrier selected from alumina, silica, magnesia, lanthana and ceria. OBJECTS OF INVENTION An object of this invention is to propose an improved nickel catalyst for pre-reforming. Description of the invention According to this invention there is provided a steam reforming catalysts for hydrocarbons, the active catalytic component being nickel supported on a carrier material comprising a mixture of two or more metals selected from cobalt, palladium, zirconia, alumina, magnesia, silica, calcium oxide, lanthana and ceria but excluding a mixture selected from alumina, silica, magnesia, lanthana and ceria .compounds or mixtures thereof. The catalyst can be operated with a wide range of hydrocarbon feed stocks, for instance natural gas to kerosene at various temperatures and steam to carbon ratio. The catalyst in which zirconia is added as one of the support materials was most effective for the steam reforming of light and heavy hydrocarbon feed stocks upto kerosene. The zirconia containing catalyst exhibited higher activity, lower carbon deposition, high thermal stability and high retained mechanical strength even for operation with heavy feed stocks at high temperature and low steam to carbon ratio. Presence of cobalt or palladium exhibited a promoting effect towards improving the activity in the temperature range 380-420°C. The novelty of the nickel catalyst described in the present invention is the inclusion of zirconia in the range 2-20% along with alkaline earth oxides, rare earth oxides and alumina. Magnesium oxide and silica were replaced with oxides of calcium and aluminium with a view to impart extra mechanical strength to the catalyst. Zirconia is incorporated with the objective of improving the coke resistence properties and retained mechanical strength during operations with heavy hydrocarbon feed stocks at various temperatures and steam to carbon ratios. The nickel catalyst described in the present invention comprising of zirconia, rare earth oxides, calcium oxide and alumina exhibited high coke resistence property and higher retained mechanical strength during operation for keosene steam reforming in the inlet temperature range 400-550°C and at a steam to carbon ratio of 1.5. The zirconia is stabilised with ceria during the precipitation of zirconyl chloride with cerium nitrate . Zirconia stabilised with ceria imparts high thermal stability, higher sulfur resistance and coke resistence property to the supported nickel catalyst. Partially stabilised zirconia has a high oxygen ionic conductivity, which may be related to the activation of oxygen ions in water or to the effect to suppress coking. The replacement of magnesia and silica with calcium oxide and alumina has considerably improved the mechanical strength of the catalyst. The loss in surface area on hydrothermal treatment at 550°C or during operation was found to be the lowest for nickel catalysts containing ceria stabilised zirconia as a promoter. The crystallite growth on hydrothermal treatment at 550°C or during operation was found to be minimum for catalyst containing zirconia and rare earth oxides. Nickel catalyst containing rare earth oxides and zirconia exhibited the highest coke resistence property when coking test was carried out at 500°C, a liquid hourly space velocity of 2.0 using high aromatic naphtha (30% aromatics) at steam to carbon ratio of 1 and pressure of 1 kg/cm2. The said test indicated maximum coking time to reach pressure drop across the catalyst bed DELTA P of 3 psi. Time taken for coking to reach DELTA P of 3psi was taken a s an indication for the comparison of catalysts of the present invention. The acidity of the ceria stabilised zirconia was comparable to the reference catalyst without zirconia. The reducibility of the nickel catalyst containing ceria stabilised zirconia was also found to be better than the reference catalyst taken for comparison. The metal dispersion has also marginally improved when compared with the reference catalyst. Detailed description of the preferred embodiments This invention relates to a novel catalyst for application in the steam-reforming of hydrocarbons particularly for operating with low as well as heavier feed stocks upto kerosene at low steam to carbon ratio and at inlet temperatures in the range 400-550°C and at very high space velocities of hydrocarbon. The catalyst described in the present invention exhibits improvement with respect to activity, hydrothermal stability, sulphur tolerance, coke resistance and retained mechanical strength. According to this invention there is provided a novel catalyst and process for preparing an improved catalyst comprising reacting an aqueous solution of nitrates of nickel, rare earth elements and zyrconyl chloride with an aqueous alkali solution containing alumina to form a mixed precipitated slurry at ambient-80°C and pH -7-10, ageing the precipitated slurry for 1-4 hours, washing, drying and calcining the said precipitate. Calcined material is densified, granulated and tabletted to have the final composition in the range 50-75% Nickel oxide, 3-15% alkaline earth metal oxide, 10-40% alumina, 4-20% rare earth oxide and 2-20% zirconia. A number of catalysts are prepared by reacting together salts of nickel and lanthanides with alkali solution over alumina/silica/magnesia supports. Catalysts containing 2-5% Cobalt oxide or 100-5000 ppm palladium were also prepared by using cobalt nitrate during precipitation or by using palladium chloride for impregnation of catalyst pellets. The present invention will be detailed below with reference to the following working examples, but the present invention is by no means limited to these specific examples. The following metal salt solutions are used for the preparation of 1 kg of all the catalysts: Solution I 2500 g Ni(NO3)2.6H2O in 10 L deionized water Solution II 200 g Ce(NO3)3.6H2O in 1 L deionized water Solution III 200 g La(NO3)3.6H2O in 1 L deionized water Solution IV 2200 g sodium carbonate in 10 L deionized water Solution V 265 g ZrOCl2.8H20 in 2L deionized water Solution VI 235 g Co(NO3)3.6H2O in 2 L deionized water Solution VII 4.2 g PdCl2 in 250 mL deionized water The following supports were also used for the preparation of catalyst samples: 1. Silica containing 80% SiO2 and rest H2O 2. Activated alumina containing 70% A12O3 (micronised to particle size rest H2O 3. Activated magnesia containing 85% MgO and rest H2O/CO2 4. Calcined Calcium Oxide. Example-1 A mixture of solutions I, II and III was slurried with 25g precipitated silica, 30g activated magnesia and 400g of activated alumina and precipitated with solution IV. The final pH of the mixture was 8-9 and the temperature during the precipitation was maintained in the range 40-80°C. The precursor obtained was processed to a finished product after ageing, washing, filtration, drying, mixmulling, granulation, tabletting and final calcination and the catalyst is designated as A. An improvement in retained mechanical strength under reducing and hydrothermal conditions and increase in nickel oxide reducibility and therefore improvement in steam hydrocarbon reforming activity is expected for this preparation. Example-2 Precipitation for preparation without silica and magnesia, catalyst B, was done by the same method of example - I, except that alumina addition during precipitation was reduced to 150g. The dried and calcined precipitate was mixed with 150g of oxides of calcium and aluminium (in the ratio of 4.0) and tabletted, dried, steam autoclaved and calcined. A decreased metal support interaction of the active phase with this support leads to an improved reduction of nickel oxide and increase in activity is expected. Example-3 Catalyst C was prepared by the same method used in example-2 except that zirconyl oxychloride solution (Solution V) was mixed with solutions I, II & III before precipitation. Addition of zirconia is expected to improve the steam reforming activity, retained mechanical strength, coking and sulfur tolerance properties. Example-4 Catalyst D was prepared by the same method used in example-2 except that cobalt nitrate solution (Solution VI) was mixed with other solutions I, n and III before precipitation. Addition of cobalt is expected to improve the reducibility and low temperature steam reforming activity. Example-5 Catalyst E was prepared by the same method used in example-2 except that the calcined tablets were impregnated with palladium chloride solution (Solution VII) and further calcined. Doping of palladium is expected to improve the reducibility and the low temperature steam reforming activity. Example-6 Commercially proven catalyst for comparison: Reference catalyst F was prepared by precipitating solution VI with a mixture of solutions I, II and III which is preslurried with 50g precipitated silica, 60g activated magnesia and 150g. of activated alumina. The precipitate was processed to tablets by the method used in example-1. Example-7 The catalyst A-F were analysed for the chemical composition and the percentage weight ratio of nickel oxide to other metal oxides was found to be in the range 1.0 - 1.1. ExampIe-8 The catalysts of methods A and E and the reference catalyst F were evaluated for kerosene-steam reforming activity in a high pressure flow reactor after reducing 20mL of sized particle of the catalyst with hydrogen at 450°C for 18hrs at a space velocity of 2000h~1 and at atmospheric pressure and further reduction at 10kg/cm2 for 2hours. Reaction was carried out at a liquid hourly space velocity of 5.0, steam/carbon mol ratio of 1.5, temperature 380-420°C, pressure 10kg/cm2. Sulphur in the feed was 0. Ippm. The product gas contains 0.1 - 0.6% carbon monoxide, 18-22% carbon dioxide and 58-64% methane and balance hydrogen. Based on the performance for a period of 24 hours on stream, as indicated in Fig.l, kerosene steam reforming activity of the catalysts follow the order E~D~C>B>A>F. Example-9 Kerosene steam reforming activity was carried out by the same procedure as in example-8, except that the temperature of reaction was 550°C. Sulphur in the feed was 0. Ippm. The product gas contains 2-3% carbon monoxide, 10-14% carbon dioxide, 35-40% methane and rest hydrogen. Based on the performance for a period of 24 hours on stream, the kerosene steam reforming activity of the catalysts follow the order OE~D>B>A>F Exanmple-10 Kerosene reforming activity was carried out by the same method as in example-9 except that the sulfur in the feed was 5ppm. Reforming activity was reduced by about 5-10%. Based on the performance for a period of 24 hours on stream, the kerosene steam reforming activity of the catalyst follow the order OE~D>B>A>F. Example-11 Coking test was carried out by measuring pressure drop across the bed after subjecting the catalyst to kerosene steam reforming at low steam/carbon ratio and high temperature. Sized particle (8 x 12 mesh) of the catalyst was tested for naphtha steam reforming at 500°C, liquid hourly space velocity 2, steam/carbon= 1.0, and pressure 1 kg/cm2. The coking time to reach delta pressure of 3 psi across the bed was taken as a measure of the coke resistance property; more the coking time, higher will be coke resistance property of the catalyst. Based on the coking time for kerosene steam reforming at low steam/carbon ratio, coke resistance property of the catalysts follow the order OD~E>B~A>F. Example-12 Thermal stability of catalyst was evaluated from the loss in surface area on subjecting the catalyst to high temperature calcination at 700°C. Evaluation of loss in surface area on high temperature calcination indicated the lowest drop in BET surface area about 5% for catalyst C which contains zirconia as a promoter. All other catalysts exhibited comparable stability having drop in surface area around 10-20%. The surface area of all fresh catalysts are in the range 150-200m2/g. Example-13 Nickel oxide crystallite growth of the catalyst was determined subjecting to hydrothermal treatment in an autoclave at 250°C and 45 bar pressure. Zirconia containing catalyst exhibited the highest hydrothermal stability as indicated by the low crystallite growth for catalyst C. All other catalysts exhibited comparable stability. The. crystallite size of NiO in fresh catalyst was in the range 3 0-40A and that for hydrothermally treated catalyst is in the range 60-70A Example-14 Mechanical strength was determined after subjecting the catalyst pellets to hydrothermal treatment at 250°C and 45 bar pressure. Percentage retained mechanical strength with respect to fresh catalyst after subjecting the catalyst to hydrothermal treatment, follows the order OE~D~B>A>F. Example-15. Mechanical strength was determined after subjecting the catalyst pellets for hydrothermal treatment using steam and N2(80:20) at 600°C, 20kg/cm2 pressure and total hourly space velocity of 15000 for 16 hours. Percentage retained mechanical strength with respect to fresh catalyst after subjecting to hydrothermal treatment, follows the order OE~D~B>A>F Example-16 Mechanical strength was determined after subjecting the catalyst pellets to hydrothermal treatment for 16hours under reducing conditions at 850°C, steam/hydrogen mole ratio of 4 and pressure 20kg/cm2. Percentage retained mechanical strength with respect to fresh catalyst after subjecting to hydrothermal treatment, follows the order: OE~D~B>A>F Example-17 Mechanical strength was determined after subjecting the catalyst pellets to kerosene steam reforming activity as indicated in example-9. Percentage retained mechanical strength with respect to fresh catalyst after subjecting to kerosene steam reforming, follows the order: OE~D~B>A>F Example-18 Studies on temperature programmed reduction in the temperature range ambient-600°C for the catalysts indicated the following order for reducibility of nickel oxide: E>D>C>B>A>F. Reducibility of nickel oxide is in the catalysts is in the range 30-50% at 450°C. Example-19 Studies on temperature programmed desorption of ammonia in the temperature range Ambient-600°C for the catalysts indicate comparable acidity for all the catalysts described here. Majority of the acid sites, around 70-75%, are weak in nature as indicated by ammonia desorption in the temperature range 100-250°C. We claim: 1) A steam reforming catalysts for hydrocarbons, the active catalytic component being nickel supported on a carrier material comprising a mixture of two or more metals selected from cobalt, palladium, zirconia, alumina, magnesia, silica, calcium oxide, lanthana and ceria but excluding a mixture selected from alumina, silica, magnesia, lanthana and ceria .compounds or mixtures thereof/ 2) The steam reforming catalyst of claim 1 wherein the catalyst is comprising from about 50-75% nickel oxide, alkaline earth oxide from about 3-15% , from about 10-40% of alumina and 4-20% of rare earth oxide promoter and from about 2-20% of zirconia. 3) The steam reforming catalyst of claim 1 wherein the alkaline earth oxide comprises calcium oxide and magnesium oxide, more preferably calcium oxide. 4) The steam reforming catalyst of claim 1 wherein zirconia and rare earth oxides are added as promoters. 5) The steam reforming catalyst of claim 1 wherein zirconium oxide and calcium oxide are used instead of silica and magnesia. 6) The steam reforming catalyst of claim 1 wherein cobalt oxide is added as a promoter in the range 1-5%. 7) The steam reforming catalyst of claim 1 wherein palladium is used as a promoter in the range 100-5000ppm. 8) The steam reforming catalyst of claim 1 wherein calcium oxide and alumina are used as compounds or mixtures thereof. 9) The adiabatic steam reforming catalyst comprising of 50-75% nickel oxide, 3-15% calcium oxide, 10-30% of alumina, 2-10% of zirconia and 4-20% of lanthana of claim 1 exhibits higher sulphur tolerance for operation with heavy feed stocks upto kerosene containing 0.05 - 5ppm sulphur. 10) A steam reforming catalyst substantially as herein described.

Documents:

1123-del-2001-abstract.pdf

1123-del-2001-assignments.pdf

1123-del-2001-claims-07-04-2008.pdf

1123-del-2001-claims.pdf

1123-del-2001-correspondence-others-07-04-2008.pdf

1123-del-2001-correspondence-others.pdf

1123-del-2001-description (complete).pdf

1123-del-2001-description (complete)07-04-2008.pdf

1123-del-2001-drawings.pdf

1123-del-2001-form-1.pdf

1123-del-2001-form-18.pdf

1123-del-2001-form-2-07-04-2008.pdf

1123-del-2001-form-2.pdf

1123-del-2001-form-3.pdf

1123-del-2001-form-6.pdf

1123-del-2001-gpa.pdf