Novel, highly efficient, eco-friendly processes for converting CO.SUB.2 .or co-rich streams to liquid fuels and chemicals

Abstract

The invention provides a process for preparing liquid fuels and chemicals, which process comprises feeding carbon monoxide and hydrogen to a hydrogenation reactor, wherein the molar ratio CO:H.sub.2 is in the range of 1:0.5 to 1:0.9, catalytically hydrogenating said carbon monoxide in said hydrogenation reactor, condensing the effluent of said hydrogenation reactor to recover one or more organic liquid(s) and an aqueous solution, feeding a non-condensable component of said effluent into an oligomerization reactor; condensing an effluent discharged from the oligomerization reactor to obtain an additional organic liquid and an additional gaseous stream, separating said additional organic liquid, and either combusting said additional gaseous stream to produce heat and electricity, or processing same to obtain recyclable gaseous streams utilizable in said process.

Claims

1. A process for preparing liquid fuels and chemicals, which process comprises feeding carbon monoxide and hydrogen to a hydrogenation reactor, wherein the molar ratio CO:H.sub.2 is in the range of 1:0.5 to 1:0.9, catalytically hydrogenating said carbon monoxide in said hydrogenation reactor to produce a hydrogenation effluent, condensing the effluent of said hydrogenation reactor to recover one or more organic liquid(s) and an aqueous solution, feeding a non-condensable component of said effluent into an oligomerization reactor; condensing an effluent discharged from the oligomerization reactor to obtain an additional organic liquid and an additional gaseous stream, separating said additional organic liquid, and either combusting said additional gaseous stream to produce heat and electricity, or processing said additional gaseous stream to obtain recyclable gaseous streams utilizable in said process, wherein the carbon monoxide and hydrogen feedstock is supplied by dry reforming carbon dioxide with natural gas or co-electrolysis of carbon dioxide and steam, wherein the process further comprises splitting the additional gaseous component generated in the oligomerization reaction into a carbon monoxide stream and carbon monoxide-depleted, carbon dioxide-rich stream, recycling said carbon monoxide stream to the hydrogenation reactor; dividing said carbon monoxide-depleted, carbon dioxide-rich stream into two subsidiary streams, wherein one subsidiary CO.sub.2-containing stream is used to supply CO.sub.2 to said dry reforming reaction or said co-electrolysis, and the other CO.sub.2-containing stream is reacted with hydrogen in reverse water gas shift reactor to produce CO and water, following which the effluent of said RWGS reactor is separated into water and CO-containing stream which is used to supply CO to the hydrogenation reaction.

2. A process for preparing liquid fuels and chemicals, which process comprises feeding carbon monoxide and hydrogen to a hydrogenation reactor, wherein the molar ratio CO:H.sub.2 is in the range of 1:0.5 to 1:0.9, catalytically hydrogenating said carbon monoxide in said hydrogenation reactor to produce a hydrogenation effluent, condensing the effluent of said hydrogenation reactor to recover one or more organic liquid(s) and an aqueous solution, feeding a non-condensable component of said effluent into an oligomerization reactor; condensing an effluent discharged from the oligomerization reactor to obtain an additional organic liquid and an additional gaseous stream, separating said additional organic liquid, and either combusting said additional gaseous stream to produce heat and electricity, or processing said additional gaseous stream to obtain recyclable gaseous streams utilizable in said process, comprising producing a mixture of carbon monoxide and hydrogen either by means of dry reforming carbon dioxide or co-electrolysis of carbon dioxide and steam, separating hydrogen in part from said mixture, to form syngas feedstock, feeding said syngaswherein the molar ratio CO:H.sub.2 is in the range of 1:0.5 to 1:0.9 to a hydrogenation reactor, catalytically hydrogenating said carbon monoxide in said hydrogenation reactor to produce a hydrogenation effluent, condensing the effluent of said hydrogenation reactor at a first temperature to obtain a first organic liquid and a first gaseous stream, separating said first organic liquid and collecting same; condensing said first gaseous stream at a second temperature to obtain a second liquid, which consists of an organic phase and an aqueous phase, and a second gaseous stream; separating said second liquid into a second organic liquid and an aqueous phase; feeding said second gaseous stream into the oligomerization reactor; condensing the effluent discharged from the oligomerization reactor to obtain a third organic liquid and a third gaseous stream, separating and collecting third organic liquid, splitting said third gaseous component into a carbon monoxide stream and carbon monoxide-depleted, carbon dioxide-rich stream, recycling said carbon monoxide stream to said hydrogenation reactor; dividing said carbon monoxide-depleted, carbon dioxide-rich stream into two subsidiary streams, wherein one subsidiary CO.sub.2-containing stream is used to supply CO.sub.2 to said dry reforming reaction or said co-electrolysis, and the other CO.sub.2-containing stream is reacted with hydrogen in reverse water gas shift (RWGS) reactor to produce CO and water, following which the effluent of said RWGS reactor is separated into water and CO-containing stream which is used to supply CO to said hydrogenation reaction, hydrotreating one or more organic products collected in the process to form premium liquid fuels, and converting oxygenates in the aqueous solution into olefins which are fed to the oligomerization reactor.

3. A process for preparing liquid fuels and chemicals, which process comprises feeding carbon monoxide and hydrogen to a hydrogenation reactor, wherein the molar ratio CO:H.sub.2 is in the range of 1:0.5 to 1:0.9, catalytically hydrogenating said carbon monoxide in said hydrogenation reactor to produce a hydrogenation effluent, condensing the effluent of said hydrogenation reactor to recover one or more organic liquid(s) and an aqueous solution, feeding a non-condensable component of said effluent into an oligomerization reactor; condensing an effluent discharged from the oligomerization reactor to obtain an additional organic liquid and an additional gaseous stream, separating said additional organic liquid, and either combusting said additional gaseous stream to produce heat and electricity, or processing said additional gaseous stream to obtain recyclable gaseous streams utilizable in said process, wherein the carbon monoxide and hydrogen feedstock is supplied from waste gases characterized by having H.sub.2/CO molar ratio of <0.5, the process comprises subjecting said waste gas to water gas shift (WGS) reaction to convert part of the CO so that the H.sub.2/CO molar ratio increases, and separating excess hydrogen in a membrane so that the H.sub.2/CO molar ratio of the stream fed to CO hydrogenation reactor is adjusted to about 0.6-0.8, and hydrogenating the product of said WGS reaction.

4. A process for preparing liquid fuels and chemicals, which process comprises feeding carbon monoxide and hydrogen to a hydrogenation reactor, wherein the molar ratio CO:H.sub.2 is in the range of 1:0.5 to 1:0.9, catalytically hydrogenating said carbon monoxide in said hydrogenation reactor, to produce a hydrogenation effluent, condensing the effluent of said hydrogenation reactor to recover one or more organic liquid(s) and an aqueous solution, feeding a non-condensable component of said effluent into an oligomerization reactor; condensing an effluent discharged from the oligomerization reactor to obtain an additional organic liquid and an additional gaseous stream, separating said additional organic liquid, and either combusting said additional gaseous stream to produce heat and electricity, or processing said additional gaseous stream to obtain recyclable gaseous streams utilizable in said process, wherein the carbon monoxide and hydrogen feedstock is supplied from waste gases characterized by having H.sub.2/CO molar ratio of >0.9, the process comprises subjecting said waste gas to RWGS reaction, condensing the product of the RWGS reaction to obtain water and non-condensable component, separating water from the gaseous component and separating hydrogen therefrom, and directing the gaseous stream to the hydrogenation reaction.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the drawings:

(2) FIG. 1 displays the design of the process of the invention that reacts CO.sub.2 and natural gas, combining together the dry reforming, CO hydrogenation and oligomerization reaction.

(3) FIG. 2 displays the design of the process of the invention employing waste gas containing H.sub.2/CO<0.7, e.g., combining together WGS reaction, CO hydrogenation and oligomerization reaction.

(4) FIG. 3 displays the design of the process of the invention employing waste gas containing H.sub.2/CO>0.7, combining together RWGS reaction, CO hydrogenation and oligomerization reaction.

(5) FIG. 4 depicts a schematic description of an experimental set up for CO hydrogenation.

(6) FIG. 5 shows the distillation curve of the organic liquid produced by CO hydrogenation.

(7) FIG. 6 shows the distillation curve of the organic liquid produced by oligomerization.

(8) FIG. 7 depicts a schematic description of an experimental set up for RWGS reaction with carbon dioxide and hydrogen in a fixed bed reactor.

DETAILED DESCRIPTION

EXAMPLES

Example 1

(9) Carbon Monoxide Reaction with Hydrogen in a Fixed Bed Reactor

(10) A schematic description of the experimental set-up used for running the hydrogenation of carbon monoxide is shown in FIG. 4. Catalyst activation was done by in-situ reduction in hydrogen at 20 cm.sup.3/min*gram.sub.cat at temperature of 450 C. and atmospheric pressure in reactor (2), for 4 h.

(11) CO was contacted with H.sub.2 by passing a mixture of CO and H.sub.2 streams (indicated by numerals (51) and (52), respectively) at a molar ratio 1:0.7 through a tubular reactor (2) (16 mm ID, 250 mm long) packed with 6 gram of the extrudates of Preparation 1 and heated up to 275 C. at a total pressure of 40 atm. All gaseous reactants are fed via line (53) to the reactor (2).

(12) With the aid of a cooler (54A), the reaction products were cooled down to a temperature T.sub.1 (T.sub.1>120 C.) to form a mixture consisting of non-condensable and liquid products. The mixture is separated in a first gas-liquid separator (55A) into a first liquid component (56) and a gaseous component (57).

(13) The liquid component consists of a heavy organic phase. It is collected in a vessel through stream (56), constituting the first organic product obtained by the experiment.

(14) The gaseous component is cooled down with the aid of a second cooler (54B) to a temperature T.sub.2 (30<T.sub.2<60 C.), undergoing condensation to form a mixture consisting of non-condensable materials and liquid products. This mixture is then separated in a second gas-liquid separator (55B) into a liquid component and a gaseous component. The liquid component is separated into organic and aqueous phases, which are collected through lines (59) and (60), respectively. This organic phase constitutes the second organic product obtained by the experiment.

(15) The non-condensable components flowing in line (61) consist of CO.sub.2, CO, light hydrocarbons and residual H.sub.2 generated by the water gas shift reaction. This gaseous stream enters the oligomerization reactor (3) packed with 6 grams of commercial catalyst heated up to 250 C. and total pressure of 40 atmospheres.

(16) The products of the oligomerization reaction are cooled in a cooler (62) down to T.sub.3<10 C., e.g., 0<T.sub.3<5 C., undergoing condensation to a light organic liquid component which is separated from the non-condensable component in a gas-liquid separator (63). The light organic liquid (64) thereby collected constitutes the third organic product obtained by the experiment.

(17) Gas products (65) were analyzed in online Agilent 7890A Series Gas Chromatograph equipped with 7 columns and 5 automatic valves using helium as a carrier gas. The liquid organic products (56, 59 and 64) were analyzed by GC-MS (Agilent Technologies 6890N network GC system equipped with 5973 Network mass-selective detector) as described in more detail below. Aqueous phase (60) was analyzed for Total Organic Carbon in Shimadzu TOC-V.sub.CPN Analyzer.

(18) In the tables below, the capital letters X and S stand for conversion and selectivity, respectively. The weight selectivity to CH.sub.4, C.sub.2-C.sub.4 olefins (olefins are abbreviated in the tables below C.sub.2.sup.= and C.sub.3-C.sub.4.sup.=), C.sub.2-C.sub.4 paraffins and C.sub.5+ hydrocarbons was calculated on the carbon basis as S.sub.i=[C.sub.i/C.sub.i*100%, where C.sub.i is the amount of carbon (gram) contained in product (i) produced at period of time, C.sub.iamount of carbon (gram) contained in all hydrocarbons produced over the same period of time. The selectivity to CO.sub.2, S.sub.CO2F.sub.CO2/(F.sub.CO,0F.sub.CO), was calculated as the moles of CO.sub.2 produced per moles of CO reacted.

(19) The Hydrogenation Reaction:

(20) The reaction of carbon monoxide with hydrogen in reactor (2) to produce hydrocarbons was run under the following specific conditions:

(21) WHSV.sub.CO=0.90 h.sup.1, temperature 275 C., total pressure at the reactor 40 atm, H.sub.2/CO=0.7 mol/mol. The time on stream was 1100 hours. The results are shown in Table 1.

(22) TABLE-US-00001 TABLE 1 Oxygen. H.sub.2/CO s.sub.C1 s.sub.C2-C4 s.sub.C2 = s.sub.C3 = s.sub.C4 = s.sub.C5+ in water S.sub.CO2 at x.sub.CO, % X.sub.H2, % wt % wt % wt % wt % wt % wt % wt % mole % outlet 75 72 6.0 8.3 2.7 8.2 6.8 67.5 0.5 47 0.7

(23) Over a period of 70 hours, 42.4 grams of organic liquid and 2.5 grams of aqueous solution were collected. The organic liquids (56, 59) collected in the two separators (55A, 55B, respectively) were mixed and analyzed. The composition of the organic liquid (56+59) is listed in Table 2 while the composition of the aqueous solution (60) is listed in Table 3. The distillation curve of the organic liquid is shown in FIG. 5.

(24) TABLE-US-00002 TABLE 2 % Total % C4 Olefins 0.4 4.3 Paraffins Oxygenates 3.9 C5 Olefins 2.1 3.6 Paraffins Oxygenates 1.5 C6 Olefins 2.7 6.5 Paraffins 2.6 Oxygenates 1.2 C7-C10 non Olefins 8.0 37.8 Olefins 13.5 non n-Paraffins 2.2 n Paraffins 9.7 Iso-Paraffins 1.3 Cyclo-Paraffins 0.9 Aromatics 0.2 Oxygenates 2.0 C11-C22 non Olefins 10.1 41.8 Olefins 8.9 non n-Paraffins 3.3 n Paraffins 16.0 Iso-Paraffins 2.0 Cyclo-Paraffins 1.3 Aromatics Oxygenates 0.2 >C23 Olefins 0.3 6.0 Paraffins 5.7

(25) TABLE-US-00003 TABLE 3 Percentage in Oxygenates Compounds Organic compound [% wt] C2-C8 Alcohol 71.8 C2-C4 Carboxylic acid 24.4 C2-C9 Carboxylic acid & Ester 0.7 (Acetate ester) C2-C10 Ketone 3.1

(26) The Oligomerization Reaction

(27) The oligomerization reaction (3) to produce hydrocarbons was run under the following specific conditions:

(28) WHSV.sub.olefins=0.03 h.sup.1, temperature 250 C., total pressure at the reactor 40 atm. The time on stream was 1050 hours.

(29) The conversion of the light olefins to C.sub.5+ hydrocarbons was 75%. The composition of the organic liquid is listed in Table 4. The distillation curve is shown in FIG. 6.

(30) TABLE-US-00004 TABLE 4 C4-C16 Component % Olefins -Olefins 0.1 (43.6%) Non -Olefins 9.3 Monoalkyl olefins 13.8 Dialkyl olefins 14.8 Trialkyl olefins 5.6 Paraffins n-paraffins 6.7 (19.6%) Monoalkylparaffins 12.0 Dialkyl olefins 0.9 Naphthenes Naphthenes 9.1 Aromatics Aromatics 12.6 Oxygenates Oxygenates 15.1

Example 2

(31) Carbon Monoxide Hydrogenation in a Fixed Bed Reactor Fed with a Mixture Containing 21 Molar % Carbon Dioxide

(32) This experiment was conducted in a mini-pilot plant with a similar design as in Example 1 schematically described in FIG. 4. The tubular reactor (16 mm ID, 500 mm long) of the mini-pilot was packed with 20 gram of the extrudates of Preparation 1.

(33) The effluent from reactor (2) flows directly to cooler (54B) where it is cooled down to a temperature T.sub.1 (80<T.sub.1<110 C.), undergoing condensation into a liquid component and a gaseous component. The liquid component is separated into organic and aqueous phases, which are collected through lines (59) and (60), respectively.

(34) The non-condensable components flowing in line (61) consist of CO.sub.2, CO, light hydrocarbons and residual H.sub.2 generated by the water gas shift reaction. This gaseous stream enters the oligomerization reactor (3) packed with 20 grams of commercial catalyst heated up to 250 C. and total pressure of 50 atmospheres.

(35) The reaction of carbon monoxide with hydrogen to produce hydrocarbons was run under the following specific conditions:

(36) WHSV.sub.CO=1.0 h.sup.1, temperature 275 C., total pressure at the reactor 50 atm, H.sub.2/CO=0.7 mol/mol and CO.sub.2/CO=0.46 mol/mol. The time on stream was 620 hours. The results are shown in Table 5.

(37) TABLE-US-00005 TABLE 5 Oxygen, H.sub.2/CO s.sub.C1 s.sub.C2-C4 s.sub.C2 = s.sub.C3 = s.sub.C4 = s.sub.C5+ in water S.sub.CO2 at x.sub.CO, % X.sub.H2, % wt % wt % wt % wt % wt % wt % wt % mole % outlet 76 73 6.8 7.9 2.4 0.5 2.3 78.6 1.5 46 0.8

(38) The composition of the organic liquid is listed in Table 6.

(39) The oligomerization reaction to produce hydrocarbons was run under the following specific conditions:

(40) WHSV.sub.olefins=0.04 h.sup.1, temperature 250 C., total pressure at the reactor 50 atm. The time on stream was 470 hours.

(41) The conversion of the light olefins to C.sub.5+ hydrocarbons was 71%. The composition of the organic liquid is listed in Table 7.

(42) TABLE-US-00006 TABLE 6 % Total % C4 Olefins 1.4 Paraffins Oxygenates 1.4 C5 Olefins 0.6 1.8 Paraffins Oxygenates 1.2 C6 Olefins 1.7 3.3 Paraffins 0.8 Oxygenates 0.8 C7-C10 non Olefins 4.9 31.3 Olefins 13.2 non n-Paraffins 1.9 n Paraffins 6.1 Iso-Paraffins 0.9 Cyclo-Paraffins 0.9 Aromatics 0.4 Oxygenates 3.0 C11-C22 non Olefins 14.9 56.3 Olefins 14.3 non n-Paraffins 5.6 n Paraffins 15.3 Iso-Paraffins 4.2 Cyclo-Paraffins 1.4 Aromatics Oxygenates 0.6 >C23 Olefins 0.4 5.9 Paraffins 5.5

(43) TABLE-US-00007 TABLE 7 C4-C16 Component % Olefins -Olefins 0.8 (37.1%) Non -Olefins 4.0 Monoalkyl olefins 12.8 Dialkyl olefins 15.3 Trialkyl olefins 4.2 Paraffins n-paraffins 8.4 (22.4%) Monoalkyl paraffins 14.0 Dialkyl olefins Naphthenes Naphthenes 14.5 Aromatics Aromatics 17.9 Oxygenates Oxygenates 8.1

Example 3

(44) RWGS Reaction with Carbon Dioxide and Hydrogen in a Fixed Bed Reactor

(45) A schematic description of the experimental set-up used for the production of carbon monoxide from carbon dioxide and hydrogen is shown in FIG. 7.

(46) The experimental unit consists of three 16 mm ID, 250 mm long tubular reactors in series, equipped with an electrical heater and a central thermowell, four coolers, four vapor-liquid separators, Brooks flowmeter for H.sub.2 and CO.sub.2, and a backpressure regulator. The axial temperature profile is measured by a movable thermocouple. Pressure is controlled by a backpressure regulator.

(47) CO.sub.2 was contacted with H.sub.2 by passing a mixture of CO.sub.2 and H.sub.2 streams (indicated by numerals (201) and (202) respectively) at a molar ratio 1:1 through the first tubular reactor (301) packed with 2.5 gram of the TiO.sub.2Au(1%) extrudates and heated up to 400 C. at a total pressure of 8 atm. All gaseous reactants are fed via line (203) to the reactor (301).

(48) With the aid of a cooler (304), the reaction products are cooled down to 60 C., undergoing condensation to form a mixture consisting of non-condensable and water generated by the reverse water gas shift reaction. The mixture (204) is separated in a gas-liquid separator (308) into gas phase and water which are collected through line (205).

(49) The gaseous component flows (206) to the second tubular reactor (302) packed with 2.5 gram of TiO.sub.2Au(1%) extrudates and heated up to 400 C.

(50) With the aid of the second cooler (305), the reaction products are cooled down to 60 C. (207) to separate the water (208) generated from the second reactor (302) in a gas-liquid separator (309).

(51) The gaseous stream flows (209) to the third tubular reactor (303) packed with 2.5 grams of TiO.sub.2Au(1%) extrudates catalyst and heated up to 400 C.

(52) The products of the third reactor are cooled in cooler (306) down to 60 C. condensing to a water (211) component which is separated from the non-condensable component (212) in a gas-liquid separator (310).

(53) The gaseous phase is further cooled in cooler (307) down to 5 C. and separated into water (213) and a gaseous component consisting of CO.sub.2, H.sub.2, CO and residual CH.sub.4 generated by the methanation reaction.

(54) The gas products were analyzed in online Agilent 7890A Series Gas Chromatograph equipped with 7 columns and 5 automatic valves using helium as a carrier gas.

(55) In the table below, the capital letters X and S stand for conversion and selectivity, respectively. The weight selectivity to CO and CH.sub.4 was calculated on the carbon basis as S.sub.i=C.sub.i*100%, where C.sub.i is the amount of carbon (gram) contained in product (i) produced at period of time, C.sub.i is the amount of carbon (gram) contained in all gaseous produced over the same period of time.

(56) The reaction of carbon dioxide with hydrogen to carbon monoxide was run under the following specific conditions:

(57) WHSV.sub.CO2=3.7 h.sup.1, temperature 400 C., total pressure at the reactor 8 atm, H.sub.2/CO.sub.2=1.0 mol/mol. The time on stream was 114 hours. The results are shown in Table 8.

(58) TABLE-US-00008 TABLE 8 H2/CO molar X.sub.CO2, X.sub.H2, S.sub.CO S.sub.CH4 ratio at % % wt % wt % outlet 31.5 31.9 99.9 0.1 2.1
Preparation 1
Preparation of Potassium-Promoted Fe.sup.2+(Fe.sup.3+.sub.yAl.sup.3+.sub.1-y).sub.2O.sub.4, Silica-Containing Extrudates (y=0.47)

(59) The catalytically active compound was prepared by co-precipitation from an aqueous solution of Fe and Al nitrates, induced by the addition of aqueous ammonium hydroxide solution. 27.0 gram of Al(NO.sub.3).sub.3.9H.sub.2O and 57.9 gram of Fe(NO.sub.3).sub.3.9H.sub.2O were dissolved in 60 cm.sup.3 of distilled water each. The solutions were then mixed together and the pH of the combined solution was adjusted to 8 by adding 250 cm.sup.3 of aqueous NH.sub.4OH solution with concentration of ammonium hydroxide of 5 wt %. The obtained solid was filtered and washed with distilled water and further dried at 110 C. for 24 hours. In the present example the atomic ratio of Fe:Al in the precipitating solution was 2:1. The dried spinel material was grinded using a ball mill to particle size <180 m, and mixed-kneaded with SiO.sub.2 precursor (Ludox HS-30) at a weight ratio spinel/SiO.sub.2 70/30 in a horizontal mixing kneader machine equipped with two Z-type blades, heating mantle and a cover for closing it hermetically (The SiO.sub.2 precursor was brought to pH=7 in a vessel by few drops of 5M solution of HNO.sub.3 in water before addition to kneader; the spinel powder was added to the kneader after addition of SiO.sub.2 precursor with adjusted pH). The obtained mixture was mixed-kneaded in the hermetically closed kneader at temperature of 40 C. for 5 h. The obtained gel was discharged from the kneader and formed into pellets by extrusion through a die with openings diameter of 2.5 mm, followed by cutting the extruded wire into extrudates with a length of 15 mm (a single-screw extruder was used). The extrudates were aged in air at room temperature for 24 hours. The aged extrudates were dried in air at 110 C. for 6 hours followed by calcination in air at 350 C. for period of 6 hours. No Fe.sub.2O.sub.3 hematite phase was formed after calcination at 350 C. The calcined extrudates had diameter of 1.6 mm and length of 6-10 mm. An aqueous solution of K.sub.2CO.sub.3 was added by incipient wetness impregnation. The solid was further dried in air at 110 C. for 4 hours followed by calcination in air at 450 C. for period of 3 h. No change in the shape and size of the extrudates was detected at the impregnation step. The material had the following weight ratio of metal components (EDAX): Fe:Al:K=100:24:14.6, surface area 203 m.sup.2/gram, pore volume 0.31 cm.sup.3/gram and average pore diameter 6.1 nm.

(60) Preparation 2

(61) (Catalyst for Use in Dry Reforming)

(62) Ni-substituted hexaaluminate catalyst with the general formula BaNi.sub.xAl.sub.11-xO.sub.19- was prepared by co-precipitation from a solution of the corresponding metal nitrate salts by addition of ammonium carbonate at pH=7.5-8.0. Metal nitrates were dissolved separately in deionized water at 60 C. The clear solutions of metal nitrates (with the exception of aluminum nitrate) were then mixed together, followed by adjusting the pH value to 1 with the aid of nitric acid, before adding the aluminum nitrate solution into the metal nitrate mixture. The resulting solution was then poured at 60 C. with vigorous stirring into an aqueous solution containing a large excess of (NH.sub.4).sub.2CO.sub.3 to form the hexaaluminate precursor precipitate. During the precipitation, a large amount of CO.sub.2 was released while the pH value of the solution was maintained between 7.5 and 8.0. The resulting slurry was aged with continuous stirring at 60 C. for 3 h followed by filtration and washing with deionized water. The obtained cake was then dried at 110 C. in air overnight. The powder was further calcined at 500 C. for 2 h, followed by calcination at 1300 C. and 1400 C. for 3-5 h.

(63) The resulting powder was crushed and sieved to collect the fraction smaller than 160 m. XRD analysis yielded the following phases: Ba.sub.0.69Ni.sub.0.48Al.sub.6.36O.sub.11 95%, -Al.sub.2O.sub.3-5%. The BET surface area is 12 cm.sup.2/g.

(64) Preparation 3

(65) (Catalyst for Use in RWGS)

(66) The catalyst was prepared by inserting the gold into titania by adsorption method. 0.054-0.382 g hydrogen tetrachloroaurate (III) dihydrate (HAuCl.sub.4.2H.sub.2O, Alfa Aesar 99.9%) were dissolved in 300 ml of distilled water and the pH was adjusted to 10 by adding droplets of 1.0 M NaOH water solution under vigorous stirring and monitored with a pH meter. The resulting solution was heated to 65 C., then 10.0 g TiO.sub.2 (Saint-Gobain NorPro Co.) was added. The mixture was stirred for 2 h while 0.1M NaOH water solution was added into the slurry to adjust the pH value to 9.0. The as-received precipitate was collected by filtration, washed with 1 L of distilled water, and dried in air overnight at 100 C. followed by calcination under 1.8 Lih.Math.g O.sub.2 flow by ramping the temperature at 5 C./min and O.sub.2 flow and kept for 1 hr at 300 C.

(67) While the present disclosure has been illustrated and described with respect to a particular embodiment thereof, it should be appreciated by those of ordinary skill in the art that various modifications to this disclosure may be made without departing from the spirit and scope of the present disclosure.