METHOD FOR CATALYTIC AMMONIA SYNTHESIS UNDER CONCENTRATED SOLAR ENERGY AND CATALYSTS

Abstract

A method for catalytic ammonia synthesis under concentrated solar energy and related catalysts. The method includes placing a catalyst in a reaction apparatus, feeding nitrogen and hydrogen into the reaction apparatus, and controlling a surface temperature of the catalyst to reach about 300 C. to 550 C. under irradiation of concentrated sunshine, to synthesize ammonia. The catalyst includes an amorphous and electron-rich black nano TiO.sub.2-z (0<z<2) with a disordered surface serves as a carrier material, and an elemental nano-crystal of Fe or Ru serves as an active ingredient. The active ingredient is loaded on the carrier material. Sunshine is used as the energy during ammonia synthesis reaction, and light in the whole wave band can be utilized sufficiently. Ammonia can be synthesized under solar energy with a high efficiency, and no fossil energy or electrical energy is needed. A synergetic catalytic effect of optical energy and thermal energy can be obtained.

Claims

1. A method for catalytic ammonia synthesis with nitrogen and hydrogen under concentrated solar energy, comprising: placing a catalyst in a reaction apparatus; feeding nitrogen and hydrogen into the reaction apparatus; and controlling a surface temperature of the catalyst to reach about 300 C. to 550 C. under irradiation of concentrated sunshine, so that ammonia can be synthesized with nitrogen and hydrogen.

2. The method according to claim 1, wherein the catalyst comprises an amorphous and electron-rich black nano TiO.sub.2-z (0<z<2) with a disordered surface serves as a carrier material, and an elemental nano-crystal of Fe or Ru serves as an active ingredient; and wherein the active ingredient is loaded on the carrier material.

3. The method according to claim 2, wherein the catalyst further comprises a promoter loaded on the carrier material, the promoter comprises alkali metal or alkaline earth metal of K, Rb, Cs, Mg, Ca, Sr, or Ba, and an atom ratio of the promoter to the active ingredient ranges from 10:1 to 1:100.

4. The method according to claim 3, wherein the promoter is hydroxide, nitrate, carbonate, or bicarbonate of K, Rb, Cs, Mg, Ca, Sr, or Ba.

5. The method according to claim 1, wherein a volume ratio of nitrogen to hydrogen is 1:3.

6. The method according to claim 2, wherein when the active ingredient is an elementary substance of Fe, a use amount thereof accounts for 5 wt % to 50 wt % of the carrier material; and wherein when the active ingredient is an elementary substance of Ru, a use amount thereof accounts for 1 wt % to 8 wt % of the carrier material.

7. A catalyst comprising an amorphous and electron-rich black nano TiO.sub.2-z (0<z<2) with a disordered surface serves as a carrier material, and an elemental nano-crystal of Fe or Ru serves as an active ingredient, wherein the active ingredient is loaded on the carrier material.

8. The catalyst according to claim 7, wherein when the active ingredient is an elementary substance of Fe, a use amount thereof accounts for 5 wt % to 50 wt % of the carrier material; and wherein when the active ingredient is an elementary substance of Ru, a use amount thereof accounts for 1 wt % to 8 wt % of the carrier material.

9. The catalyst according to claim 7, further comprising a promoter loaded on the carrier material, wherein the promoter comprises alkali metal or alkaline earth metal of K, Rb, Cs, Mg, Ca, Sr, or Ba, and an atom ratio of the promoter to the active ingredient ranges from 10:1 to 1:100.

10. A method for producing the catalyst according to claim 7, wherein an impregnation method, high-temperature hydrogen reduction or liquid phase reduction, and promoter load method is used.

11. The method of claim 10, comprising loading the active ingredient on a substrate material, obtaining active ingredient/TiO.sub.2-z through high-temperature hydrogen reduction or liquid phase reduction, and loading the promoter thereon according to actual needs

12. The method of claim 11, comprising: mixing nano TiO.sub.2 and sodium borohydride (a mass ratio thereof ranging from 1:0.5 to 1:8), grinding the mixture to be uniform, heating the mixture in a closed Muffle furnace to 370 C. to 420 C., taking the mixture out and quenching, and obtaining the carrier material TiO.sub.2-z (0<z<2) through post-treatments; and impregnating the carrier material into a precursor solution of Fe or Ru with a certain amount, drying after ultrasonic mixing, obtaining active ingredient/TiO.sub.2-z through high-temperature hydrogen reduction or liquid phase reduction of the sample, and impregnating the sample obtained therein into an promoter solution so as to obtain a catalyst sample after drying in an oxygen-free atmosphere or in vacuum.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The accompanying drawings illustrate one or more embodiments of the invention and together with the written description, serve to explain the principles of the invention. Wherever possible, the same reference numbers are used throughout the drawings to refer to the same or like elements of an embodiment.

[0037] FIG. 1 is an X-Ray diffraction pattern of TiO.sub.2-z;

[0038] FIG. 2 is a high resolution transmission electron microscope picture of TiO.sub.2-z;

[0039] FIG. 3 is an electron paramagnetic resonance spectrum of TiO.sub.2-z, wherein g is an electron paramagnetic resonance factor;

[0040] FIG. 4 shows transmission electron microscope pictures of ammonia synthesis catalyst Ru/TiO.sub.2-z, wherein the left picture shows that Ru nano particles are loaded on the carrier TiO.sub.2-z uniformly, and the right picture shows one single Ru nano particle;

[0041] FIG. 5 is a near infrared-visible light-ultraviolet absorption spectrum of K/Ru/TiO.sub.2-z ammonia synthesis catalyst;

[0042] FIG. 6 schematically shows a temperature rising curve of K/Ru/TiO.sub.2-z ammonia synthesis catalyst under concentrated sunshine and a temperature dropping curve thereof without sunshine irradiation; and

[0043] FIG. 7 is a transmission electron microscope picture of K/Ru/TiO.sub.2-z after 6 times of circular reaction.

DETAILED DESCRIPTION OF THE INVENTION

[0044] The present invention is more particularly described in the following examples that are intended as illustrative only since numerous modifications and variations therein will be apparent to those skilled in the art. Various embodiments of the invention are now described in detail. Referring to the drawings, like numbers indicate like components throughout the views. As used in the description herein and throughout the claims that follow, the meaning of a, an, and the includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein and throughout the claims that follow, the meaning of in includes in and on unless the context clearly dictates otherwise. Moreover, titles or subtitles may be used in the specification for the convenience of a reader, which shall have no influence on the scope of the present invention.

[0045] As used herein, around, about or approximately shall generally mean within 20 percent, preferably within 10 percent, and more preferably within 5 percent of a given value or range. Numerical quantities given herein are approximate, meaning that the term around, about or approximately can be inferred if not expressly stated.

[0046] As used herein, the terms comprising, including, carrying, having, containing, involving, and the like are to be understood to be open-ended, i.e., to mean including but not limited to.

[0047] The description will be made as to the embodiments of the present invention in conjunction with the accompanying drawings in FIGS. 1-7. In accordance with the purposes of this invention, as embodied and broadly described herein, this invention, in one aspect, relates to a technology for catalytic ammonia synthesis with nitrogen and hydrogen under concentrated solar energy and related catalysts.

Embodiment 1

[0048] The present embodiment shows the manufacturing of a catalyst with alkali metal or alkaline earth metal as promoter, and with Ru as active ingredient, which is loaded on black TiO.sub.2-z and the synthesizing of ammonia under a catalytic effect of concentrated sunshine.

[0049] Nano titanium oxide (1 g) and sodium borohydride (2 g) are ground fully and mixed together. The mixture is placed in a Muffle furnace, in which the temperature is raised to 370 C. at a speed of 10 C./min. The crucible is taken out of the Muffle furnace at 370 C., and is put in an air environment at room temperature so that the temperature thereof drops rapidly. The solid product is placed in a beaker, and 100 ml deionized water is added to the beaker. Then, the beaker stays for 1 hour. The solid obtained therein is filtered and is washed with deionized water. The solid is dried in a vacuum drying oven at 100 C. for 4 hours, so that the carrier, i.e., black TiO.sub.2-z solid can be obtained. An X-Ray diffraction spectrum of the carrier TiO.sub.2-z is shown in FIG. 1. There is no apparent peak in the X-Ray diffraction spectrum, which shows that the material has a poor crystallinity or has no crystallinity. A high resolution transmission electron microscope picture of the carrier TiO.sub.2-z is shown in FIG. 2. It can be seen from the disordered lattice fringes in FIG. 2 that, the crystallinity of the material is poor, and the material is in a disordered state on the whole. An electron paramagnetic resonance spectrum of the carrier material is shown in FIG. 3. As shown in FIG. 3, there is a peak at g being about 2.0, which shows that the material contains abundant oxygen vacancies. Because of the disordered structure of the carrier material and the oxygen vacancies contained therein, the carrier material is electron-rich.

[0050] Black TiO.sub.2-z carrier (1 g) and a prepared tetrahydrofuran solution or acetone solution of triruthenium dodecacarbonyl, which is 3 wt % (changing in a range from 1 wt % to 8 wt %) of the carrier material measuring by Ru element, are mixed and dried. The black solid obtained therein is dried in vacuum in a tube furnace for 1 hour. The solid is placed in a reactor, and the catalyst is reduced for 1 hour in a hydrogen atmosphere (N.sub.2:H.sub.2 being 1:3, and a volume flow thereof being 10 ml/min) with a surface temperature of the catalyst at about 400 C. under concentrated sunshine. In this manner, the Ru/TiO.sub.2-z catalyst can be obtained, and the catalyst shows a black color or a dark gray color. FIG. 4 shows transmission electron microscope pictures of Ru/TiO.sub.2-z ammonia synthesis catalyst, wherein a left picture shows that Ru nano particles are loaded on the carrier TiO.sub.2-z uniformly, and a right picture shows one single Ru nano particle. It can be seen through a transmission electron microscope that, a size of the Ru particle ranges from 1 nm to 20 nm.

[0051] The above prepared Ru/TiO.sub.2-z catalyst (1 g), and ethanol solution of KOH (an atom ratio of the promoter to the active ingredient ranges from 10:1 to 1:100) are mixed fully and placed in a reactor. The mixture is dried under concentrated sunshine in an inert atmosphere (nitrogen or mixture of nitrogen and hydrogen, 20 ml/min) at about 100 C. The sample obtained therein is the ammonia synthesis catalyst, and a specific surface area of the catalyst is 84 m.sup.2/g.

[0052] A catalyst in which Ru is loaded on TiO.sub.2-z can also be produced by aqueous solution of RuCl.sub.3 or Ru(NO.sub.3).sub.3. When a precursor containing Cl is used, the catalyst produced therein should be washed with deionized water for multiple times so as to remove the Cl ions, and dried in vacuum or dried in an inert atmosphere under concentrated sunshine. Then, the promoter is loaded on the catalyst. Aqueous solution, ethanol solution or ethylene glycol solution of hydroxide, nitrate, carbonate, or bicarbonate of K, Rb, Cs, Mg, Ca, Sr, or Ba can also be used as the promoter, and thus catalyst with different kinds of promoter can be produced.

[0053] The ammonia synthesis experiment will be illustrated hereinafter.

[0054] A catalyst is placed in a reactor, and nitrogen and hydrogen (a volume ratio of nitrogen and hydrogen being 1:3) is fed into the reactor, wherein a surface temperature of the catalyst reaches a predetermined temperature under irradiation of concentrated sunshine, so that ammonia can be synthesized with nitrogen and hydrogen. A volume flow of the reaction gas (N.sub.2:H.sub.2 being 1:3) is 6 ml/min, and a use amount of the catalyst is 0.1 g.

[0055] A catalyst with Fe or Ru as active ingredient is reported by related document, but the catalyst has no catalytic effect in ammonia synthesis reaction. The specific result is shown in Table 1.

[0056] According to the present disclosure, the use amount of the precursor can be adjusted during the producing of catalyst, so that catalyst with different active ingredient content can be obtained. Specifically, a use amount of Ru accounts for 1 wt % to 8 wt % of the carrier material. The influence of different Ru loading amount on the reaction activity of the catalyst is shown in Table 2. As shown in Table 2, when the loading amount of the active ingredient Ru is increased, the reaction activity of the catalyst is increased accordingly.

[0057] The promoter used in the catalyst can be changed, and thus catalyst with different kinds of promoter can be obtained. The influence of different kinds of promoter on the reaction activity of the catalyst is shown in Table 3. As shown in Table 3, the promoting order of different kinds of promoter on the catalytic performance of the catalyst is Rb>Ba>Cs>K>Sr>Ca>Mg>without promoter.

[0058] The loading amount of the active ingredient does not change, and the using amount of promoter is adjusted. The influence of different amount of promoter on the activity of the catalyst is shown in Table 4. As shown in Table 4, when the using amount of promoter is increased, the reaction activity of the catalyst is increased accordingly.

[0059] The influence of temperature on the catalytic activity of the catalyst is shown in Table. 5. As shown in Table. 5, with respect to one catalyst, when the reaction temperature rises, the catalytic activity of the catalyst increases.

[0060] In order to research lifetime of the catalyst, circular experiment is performed for 6 times with K/3% Ru/TiO.sub.2-z (K:Ru being 1:1) as the catalyst, and each experiment occurs for 7 hours. The experiment result is shown in Table 6. It can be seen from Table 6 that, the circular performance of the catalyst is good under the reaction condition.

[0061] In order to compare the performance of concentrated sunshine catalysis with traditional heat catalysis, the ammonia synthesis comparative experiment is performed with different kinds of catalysts, i.e., the concentrated sunshine catalyst with K as promoter (K: Ru being 1:1), and Ru (Ru accounting for 3 wt % of the carrier material) being loaded on black TiO.sub.2-z, and the traditional catalyst being loaded on Al.sub.2O.sub.3, MgO, and activated carbon respectively. The result is shown in Table 7, which shows that the ammonia synthesis effect of the catalyst under concentrated sunshine according to the present disclosure is apparently better than that of the traditional heat catalyst.

[0062] The catalyst prepared according to the above steps has a black color or a dark gray color. A specific surface area of the catalyst ranges from 50 m.sup.2/g to 100 m.sup.2/g. The catalyst can absorb infrared, visible light, and ultraviolet of sunshine, and a near infrared-visible light-ultraviolet absorption spectrum of K/3% Ru/TiO.sub.2-z (K: Ru being 1:1) is shown in FIG. 5. A surface temperature of the catalyst can rise to 300 C. to 500 C. within 1 to 3 minutes under concentrated sunshine, and the requirement for temperature during ammonia synthesis reaction can be met. The black TiO.sub.2-z is an electron-rich material with a disordered surface, and the disordered surface can provide sites for Ru loading, whereby Ru can be dispersed in the carrier material in a uniform manner. After Ru is loaded thereon, since Ru can contact with Schottky of the substrate, electrons in the black TiO.sub.2-z can transfer to Ru. Therefore, the catalyst has a high activity during ammonia synthesis reaction. However, the catalyst that is reported by related document does not have a catalytic effect during ammonia synthesis reaction (the result is shown in Table 1). FIG. 6 schematically shows a temperature rising curve of the catalyst under concentrated sunshine and a temperature dropping curve thereof without sunshine irradiation. It can be seen from FIG. 6 that, the temperature of the catalyst according to the present disclosure can rise rapidly under concentrated sunshine so as to meet the requirement for temperature during ammonia synthesis reaction, and the temperature thereof can drop rapidly without sunshine irradiation. The disordered structure of TiO.sub.2-z can be maintained due to TiO.sub.2-z being reduced in hydrogen atmosphere under light excitation, the rapid temperature rising of the catalyst under light irradiation, rapid temperature dropping thereof without light irradiation, and the promoter contained therein. Therefore, the catalyst has a relatively long lifetime. The specific result is shown in FIG. 7. It can be seen through the transmission electron microscope picture that, the carrier material TiO.sub.2-z still has a disordered surface after 6 times of circular reaction. The particle size of the active ingredient Ru does not change apparently compared with the sample before reaction (as shown in FIG. 2), which shows that the carrier material has a good stability and thus the catalyst has a long lifetime.

TABLE-US-00001 TABLE 1 Ammonia synthesis performance of catalyst containing Fe or Ru active ingredient reported by related document Activity [ml Loading amount of ammonia/(per active ingredient Related gram of catalyst * Catalyst (%) document hour)] FeO.sub.x/Al.sub.2O.sub.3 2.5 Patent 0 (410 C.) (x = 0~2) CN104016825A RuO.sub.y/TiO.sub.2 2.5 Patent 0 (400 C.) (y = 0~3) CN104016825A

TABLE-US-00002 TABLE 2 The influence of Ru loading amount on ammonia synthesis performance of catalyst with K as promoter under concentrated sunshine Activity [ml ammonia/(per gram Catalyst Ru loading amount of catalyst * hour)] (K:Ru = 1:1) (wt %) (400 C.) K/Ru/TiO.sub.2z 1 0.9 2.5 2.9 3 3.5 5 5.0 8 7.5

TABLE-US-00003 TABLE 3 Ammonia synthesis performance of catalyst with alkali metal or alkaline earth metal as promoter, and Ru being loaded on black TiO.sub.2z (Ru being 3 wt % of the carrier material) under concentrated sunshine and influence of different promoters on activity of the catalyst Promoter:Ru Activity [ml (atom ratio) ammonia/(per gram (Ru loading of catalyst * hour)] Promoter amount 3 wt %) (400 C.) Rb 1:1 5.6 Ba 1:1 4.9 Cs 1:1 4.5 K 1:1 3.5 Sr 1:1 3.0 Ca 1:1 1.7 Mg 1:1 1 Without promoter 0 0.5

TABLE-US-00004 TABLE 4 The influence of atom ratio of K to active ingredient Ru on ammonia synthesis performance of catalyst with alkali metal K as promoter under concentrated sunshine Activity [ml Catalyst ammonia/(per gram (Ru loading K:Ru of catalyst * hour)] amount 3 wt %) (atom ratio) (400 C.) K/Ru/TiO.sub.2z 10:1 24.2 5:1 6.8 1:1 3.5 1:100 0.6

TABLE-US-00005 TABLE 5 The influence of temperature on activity of the catalyst with alkali metal K as promoter (K:Ru being 1:1) and Ru being loaded on black TiO.sub.2z (Ru being 3 wt % of the carrier material) Catalyst (Ru loading Activity [ml amount 3 wt %, Reaction ammonia/(per gram K:Ru being 1:1) temperature of catalyst * hour)] K/Ru/TiO.sub.2z 520 5.8 400 3.5 300 0.8

TABLE-US-00006 TABLE 6 Ammonia synthesis circular experiments of the catalyst with alkali metal K as promoter (K:Ru being 1:1) and Ru being loaded on black TiO.sub.2z (Ru being 3 wt % of the carrier material) under concentrated sunshine Activity [ml ammonia/(per gram of catalyst * hour)] (400 C.) (activity being average value during 7 hours) Times (each experiment goes on for 7 hours) Catalyst First Second Third Fourth Fifth Sixth K/Ru/TiO.sub.2z 3.5 3.7 3.4 3.6 3.7 3.5 (Ru loading amount 3 wt %, K:Ru being 1:1)

TABLE-US-00007 TABLE 7 Comparative experiments of ammonia synthesis reaction of the catalyst with alkali metal K as promoter (K:Ru being 1:1) and Ru being loaded on black TiO.sub.2z (Ru being 3 wt % of the carrier material) under concentrated sunshine and traditional heat catalyst that is loaded on Al.sub.2O.sub.3, MgO, and activated carbon respectively Catalyst (Ru loading K/Ru/TiO.sub.2x K/Ru/activated amount 3 wt %, Concentrated K/Ru/Al.sub.2O.sub.3 K/Ru/MgO carbon K:Ru being 1:1) sunshine catalysis Heat catalysis Heat catalysis Heat catalysis Activity [ml 3.5 0.1 0.9 1.8 ammonia/(per gram of catalyst * hour)] (400 C.)

Embodiment 2

[0063] The present embodiment shows the manufacturing of a catalyst with alkali metal or alkaline earth metal as promoter, and with Fe as active ingredient, which is loaded on black TiO.sub.2-z, and the synthesizing of ammonia under a catalytic effect of concentrated sunshine.

[0064] Nano titanium oxide (1 g) and sodium borohydride (1.5 g) are ground fully and mixed together. The mixture is placed in a Muffle furnace, in which the temperature is raised to 410 C. at a speed of 10 C./min. The crucible is taken out of the Muffle furnace at 410 C., and is put in an air environment at room temperature so that the temperature thereof drops rapidly. The solid product is placed in a beaker, and 100 ml deionized water is added to the beaker. Then, the beaker stays for 1 hour. The solid obtained therein is filtered and is washed with deionized water. The solid is dried in a vacuum drying oven at 100 C. for 4 hours, so that the carrier, i.e., black TiO.sub.2-z solid can be obtained. The TiO.sub.2-z is an amorphous and electron-rich material, which has a disordered surface and contains oxygen vacancies therein.

[0065] Black TiO.sub.2-z carrier (1 g) and a prepared aqueous solution of ferric chloride, which is 30 wt % (changing in a range from 5 wt % to 50 wt %) of the carrier material, are mixed and added into a beaker. The mixture is dried by an infrared light in a nitrogen atmosphere, and the solid obtained therein is compacted in a mortar and ground fully. The solid is placed in a reactor and maintained for 1 hour in an inert atmosphere with a surface temperature of the catalyst at about 350 C. under concentrated sunshine. Then, the solid is reduced. There are two reduction methods. First, high-temperature hydrogen reduction method: the solid obtained therein is reduced for 1 hour in a hydrogen atmosphere (N.sub.2:H.sub.2 being 1:3, and a volume flow thereof being 20 ml/min) with a surface temperature thereof at about 320 C. under concentrated sunshine; and the product is suction filtrated and cleaned with deionized water and ethanol after cooling, and dried by an infrared light in an inert atmosphere. Second, liquid phase reduction method: the solid (1 g) obtained therein is added to aqueous solution of NaBH.sub.4 (6 g sodium borohydride is dissolved in 1 L water), and the solution stays for 2 hours; and the solution is filtered and washed fully so as to remove Cl ions, and dried in vacuum or by an infrared light in a nitrogen atmosphere so as to obtain Fe/TiO.sub.2-z catalyst.

[0066] Ethanol solution of KOH (an atom ratio of the promoter to the active ingredient ranges from 10:1 to 1:100) is prepared. The promoter and the catalyst are mixed fully and placed under concentrated sunshine. The sample is dried by an infrared light in an inert atmosphere (nitrogen or mixture of nitrogen and hydrogen, 20 ml/min). The sample obtained therein is the ammonia synthesis catalyst K/Fe/TiO.sub.2-z, and a specific surface area of the catalyst is 62 m.sup.2/g.

[0067] According to the above method, a catalyst in which Fe is loaded on TiO.sub.2-z can also be produced by aqueous solution of FeCl.sub.3 or Fe(NO.sub.3).sub.3. When a precursor containing Cl is used, the catalyst produced therein should be washed with deionized water for multiple times so as to remove the Cl ions, and dried in vacuum or dried in an inert atmosphere under concentrated sunshine. Then, the promoter is loaded on the catalyst. Aqueous solution, ethanol solution or ethylene glycol solution of hydroxide, nitrate, carbonate, or bicarbonate of K, Rb, or Cs can also be used as the promoter, and thus catalyst with different kinds of promoter can be produced. The influence of Fe loading amount on catalytic performance of the catalyst is shown in Table 8. The ammonia synthesis effect of catalysts with different kinds of promoter is shown in Table 9. The influence of the content of promoter K on catalytic performance of the catalyst is shown in Table 10.

[0068] The catalyst prepared according to the above steps has a black color. The catalyst can absorb infrared, visible light, and ultraviolet of sunshine. A surface temperature of the catalyst can rise to 300 C. to 500 C. within 1 to 3 minutes under concentrated sunshine, and the requirement for temperature during ammonia synthesis reaction can be met. The black TiO.sub.2-z is an electron-rich material with a disordered surface, and the disordered surface can provide sites for Fe loading. In this manner, electrons in the black TiO.sub.2-z can transfer to Fe, and thus the catalyst has a high activity during ammonia synthesis reaction. The disordered structure of TiO.sub.2-z can be maintained due to TiO.sub.2-z being reduced in hydrogen atmosphere under light excitation, rapid temperature dropping of the catalyst without light irradiation, and the promoter contained therein. Therefore, the catalyst has a relatively long lifetime.

TABLE-US-00008 TABLE 8 The influence of Fe loading amount on ammonia synthesis performance of catalyst with K as promoter Fe Activity [ml ammonia/ loading (per gram of catalyst * Catalyst amount hour)] (400 C., space (promoter:Fe = 1:10) (wt %) velocity 3600 per hour) K/Fe/TiO.sub.2z 5 0.8 10 2.8 30 9 50 17

TABLE-US-00009 TABLE 9 Ammonia synthesis performance of catalyst with alkali metal or alkaline earth metal as promoter, and Fe being loaded on black TiO.sub.2z as active ingredient under concentrated sunshine Promoter:Fe Activity [ml ammonia/ (atom ratio) (per gram of catalyst * (Fe loading hour)] (400 C., space Promoter amount 30 wt %) velocity 3600 per hour) Rb 1:10 13.5 Cs 1:10 11.4 K 1:10 9 Without promoter 0 1.2

TABLE-US-00010 TABLE 10 The influence of promoter content on ammonia synthesis performance of 30% Fe/TiO.sub.2x catalyst with alkali metal K as promoter Catalyst Activity [ml ammonia/ (Fe loading (per gram of catalyst * amount K:Fe hour)] (400 C., space 30 wt %) (atom ratio) velocity 3600 per hour) K/Fe/TiO.sub.2z 10:1 32.2 1:10 9 1:100 1.4

[0069] The foregoing description of the exemplary embodiments of the invention has been presented only for the purposes of illustration and description and is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Many modifications and variations are possible in light of the above teaching.

[0070] The embodiments are chosen and described in order to explain the principles of the invention and their practical application so as to activate others skilled in the art to utilize the invention and various embodiments and with various modifications as are suited to the particular use contemplated. Alternative embodiments will become apparent to those skilled in the art to which the present invention pertains without departing from its spirit and scope. Accordingly, the scope of the present invention is defined by the appended claims rather than the foregoing description and the exemplary embodiments described therein.