LOW TEMPERATURE NH3-REFORMING UNDER ELEVATED PRESSURE

Abstract

The present invention relates to a process for the reforming of ammonia, wherein the process comprises (i) providing a reactor containing a catalyst comprising Ru supported on one or more support materials, wherein the one or more support materials display a BET surface area of 20 m.sup.2/g or more, and wherein the catalyst contains 1 wt.-% or less of Ni and Co; (ii) preparing a feed gas stream comprising NH.sub.3; (iii) feeding the feed gas stream prepared in (ii) into the reactor and contacting the feed gas stream with the catalyst at a pressure of greater than 10 bara and at a temperature in the range of from 200 to 750 C.; (iv) removing an effluent gas stream comprising H.sub.2 and N.sub.2 from the reactor.

Claims

1.-15. (canceled)

16. A process for the reforming of ammonia, wherein the process comprises (i) providing a reactor containing a catalyst comprising Ru and one or more support materials, wherein Ru is supported on the one or more support materials, wherein the one or more support materials display a BET surface area of 20 m.sup.2/g or more, and wherein the catalyst contains 1 wt.-% or less of Ni and Co calculated as the respective element and based on 100 wt.-% of the catalyst; (ii) preparing a feed gas stream comprising NH.sub.3; (iii) feeding the feed gas stream prepared in (ii) into the reactor provided in (i) and contacting the feed gas stream with the catalyst, wherein contacting is performed at a pressure of greater than 10 bara, and at a temperature in the range of from 200 to 750 C.; (iv) removing an effluent gas stream from the reactor, the effluent gas stream comprising H.sub.2 and N.sub.2.

17. The process of claim 16, wherein in (i), the one or more support materials display a pore volume in the range of from 0.2 to 3 ml/g.

18. The process of claim 16, wherein in (i), the one or more support materials are selected from the group consisting of metal oxides.

19. The process of claim 16, wherein in (i), the one or more support materials contain substantially no CaO and/or MgO.

20. The process of claim 16, wherein in (i), the catalyst comprises Ru in an amount in the range of from 0.5 to 15 wt.-% based on 100 wt.-% of the total amount of the one or more support materials.

21. The process of claim 16, wherein in (i), the catalyst further comprises one or more alkali metal and/or alkaline earth metal hydroxides, wherein the one or more alkali metal and/or alkaline earth metal hydroxides are supported on the one or more support materials supporting Ru.

22. The process of claim 21, wherein the catalyst comprises the one or more alkali metal hydroxides in an amount in the range of from 0.5 to 15 wt.-% based on 100 wt.-% of the total amount of the one or more support materials.

23. The process of claim 16, wherein in (i), the catalyst is in the form of a molding and/or in powder form.

24. The process of claim 16, wherein the feed gas stream prepared in (ii) comprises from 100 to 50,000 ppmv of H.sub.2O.

25. The process of claim 16, wherein the total amount of NH.sub.3, N.sub.2, and H.sub.2 comprised in the feed gas stream prepared in (ii) is in the range from 90 to 100 wt.-%.

26. The process of claim 16, wherein the process is for the reforming of ammonia and hydrocarbons, wherein the feed gas stream prepared in (ii) further comprises one or more hydrocarbons, and one or more of CO.sub.2 and H.sub.2O, and wherein the effluent gas stream removed in (iv) further comprises CO.

27. The process of claim 26, wherein the feed gas stream prepared in (ii) further comprises CO.sub.2 and one or more hydrocarbons.

28. The process of claim 26, wherein the feed gas stream prepared in (ii) further comprises H.sub.2O and one or more hydrocarbons.

29. The process of claim 26, wherein the feed gas stream prepared in (ii) further comprises CO.sub.2, H.sub.2O, and one or more hydrocarbons.

30. The process of claim 26, wherein the one or more hydrocarbons are selected from the group consisting of alkanes and mixtures thereof.

Description

DESCRIPTION OF THE FIGURES

[0155] FIG. 1 displays the results of NH.sub.3 reforming at a GHSV of 2000 h.sup.1, p(NH.sub.3)=30 bara and cofeeding of 10,000 ppm-vol of H.sub.2O. The catalysts were tested between 350 and 650 C. The results obtained for 5 wt.-% of Ru on ZrO.sub.2, without (Catalyst from Example 1) and with (Catalyst from Example 2) 5 wt.-% KOH promotion is shown, as well as the results obtained with the MgAl-spinel support loaded with 2.5 wt. % Ru and promoted with 4.5 wt. % LiOH according to Example 3.

[0156] FIG. 2 displays the results of NH.sub.3 reforming for the catalyst according to Example 2 at GHSV of 8000 h.sup.1, p(NH.sub.3)=10 bara and co-feeding of 5,000 ppm-vol of H.sub.2O. The catalyst was tested between 300 and 600 C.

[0157] FIG. 3 displays the XRD pattern of the catalyst of Example 3, wherein the Mg, Al-spinel structure is clearly identified as constituting support material.

EXPERIMENTAL SECTION

[0158] The present invention is further illustrated by the following examples.

Example 1: Preparation of Ru (5 wt.-%) Supported on ZrO.SUB.2

[0159] Ru supported on ZrO.sub.2 was prepared according to Example 8 of WO 2015/086639 by impregnation of a ruthenium salt solution onto a zirconium oxide powder (D9-89, BASF, BET surface area: 78 m.sup.2/g, pore volume: 0.84 ml/g), for obtaining Ru supported on ZrO.sub.2 at a loading of 5 wt.-%. The catalyst was then extruded to form extrudates having a diameter of 3 mm.

Example 2: Preparation of Ru (5 wt.-%) and KOH (5 wt.-%) Supported on ZrO.SUB.2

[0160] A 5 g sample of the 5 wt.-% Ru on ZrO.sub.2 extrudates as obtained from example 1 was subject to impregnation with a KOH solution. To this effect, 5 g of the extrudates obtained from Example 1 were split to form fractions in the range of 315 to 500 microns, which was then impregnated via incipient wetness impregnation with 0.25 g of KOH dissolved in 1.65 ml of water. The sample was then dried at 120 C. and subsequently calcined under inert atmosphere at 500 C. for 2 hours.

Example 3: Preparation of Ru (2.5 wt.-%) and LiOH (4.5 wt.-%) Supported on MgAl.SUB.2.O.SUB.4 .Spinel

[0161] A hydrotalcite precursor (Pural MG30 from Sasol) was calcined at 950 C. for 1 hour and used as support. 10 g of the support as split fractions of 315-500 microns were impregnated with 1.41 g of Ru(NO)(NO.sub.3).sub.3 solution (19.7 wt.-% Ru in the solution), wherein prior to impregnation the solution was further mixed with 9.5 g of water and 1.38 g of Li(NO.sup.3). The solution was then impregnated on the support, dried at 120 C. for 2 h and calcined at 500 C. for 2 h under synthetic air consisting of 21 vol.-% O.sub.2 and 79 vol.-% N.sub.2.

Example 4: Catalytic Tests in NH.SUB.3.-Reforming Under High Pressure

[0162] Prior to testing, the catalysts were activated in a reducing atmosphere of 5% H.sub.2 in Ar at a temperature of 30 C. (dwell time 1 h, heating rate 2 C./min). After activating the catalysts, the feed was applied (see tables below, NH.sub.3+H.sub.2O+5 vol.-% of Ar). In the respective tests, the pressure p(NH.sub.3) was set to 1, 10, 30, and 50 bara. The gas hourly space velocity (GHSV) with respect to the NH.sub.3 content was set to 2,000, 4,000, 8,000, or 16,000 h.sup.1. The temperatures were varied between 300 and 650 C.

[0163] A 650 C. dwell time of 36 h served as an aging step to monitor the stability of the catalysts. The reference conversion at 450 C. was then measured after said aging step. As may be taken from the results shown in Table 1, the deactivation was below 10% of the initial activity.

TABLE-US-00001 TABLE 1 Results from catalyst testing demonstrating the stability of the Ru/ZrO.sub.2 system. Sample from Sample from Example 2 Example 1 (Ru + KOH/ZrO.sub.2) (Ru/ZrO.sub.2) Temperature 5,000 ppmvol H.sub.2O 5,000 ppmvol H.sub.2O (after aging GHSV = 8000 h.sup.1 GHSV = 8000 h.sup.1 at 650 C.) p(NH.sub.3) = 30 bar p(NH.sub.3) = 30 bar 450 C. 94% 92%

[0164] Table 2 shows the results from the experiment at a gas hourly space velocity (GHSV) of 2,000 h.sup.1 at p(NH.sub.3)=30 bara for the catalysts from Example 1-3, respectively. The H.sub.2O content in the feed was set 10,000 ppmvol. The temperature was increased in steps of 50 C. The NH.sub.3-conversion is given in %. As may be taken from the results from testing displayed in FIG. 1, at 550 C. the catalysts approached equilibrium conversion, wherein the most active catalyst from Example 2 approaches equilibrium conversion already at 450 C.

TABLE-US-00002 TABLE 2 Results for the conversion of ammonia over the Ru-based catalysts of Examples 1 to 3. Example 3 Example 2 (Ru + LiOH/ (Ru + KOH/ Example 1 spinel) ZrO.sub.2) (Ru/ZrO.sub.2) Temperature GHSV H.sub.2O p(NH.sub.3) x(NH.sub.3) x(NH.sub.3) x(NH.sub.3) C. h.sup.1 ppm vol bara [%] [%] [%] 350 2,000 10,000 30 4.86 45.75 10.01 450 2,000 10,000 30 38.36 89.60 60.42 500 2,000 10,000 30 73.86 93.73 89.26 550 2,000 10,000 30 91.09 96.26 96.10 600 2,000 10,000 30 93.74 97.68 97.52 650 2,000 10,000 30 96.45 98.48 98.39

[0165] Table 3 shows the NH.sub.3 conversion at a GHSV of 2,000 h.sup.1 at two reference temperatures at p(NH.sub.3)=30 and 50 bara. The water content in the feed was set to 10,000 ppmv.

TABLE-US-00003 TABLE 3 Results for the conversion of ammonia at 30 and 50 bara p(NH3) of the catalysts of Examples 1 and 2. Sample from Sample from Example 2 Example 1 (Ru + KOH/ZrO.sub.2) (Ru/ZrO.sub.2) 10,000 ppmv H.sub.2O 10,000 ppmv H.sub.2O Temperature GHSV = 2,000 h 1 GHSV = 2,000 h 1 C. p(NH.sub.3) = 30 bara p(NH.sub.3) = 50 bara 450 89.6 84.3 550 96.3 94.1

[0166] Table 4 shows the NH.sub.3 conversion of the most active 5 wt.-% Ru on ZrO.sub.2 promoted with 5 wt.-% of KOH. The experiments were conducted at 1, 10 and 30 bara of ammonia p(NH.sub.3). The temperatures were varied between 300 and 600 C. at a GHSV of 8000 h.sup.1. The water content in the feed was set to 5000 ppmv. As may be taken from the results from testing displayed in FIG. 2, equilibrium conversion was reached by the catalyst according to Example 2 at 450 C., wherein almost 80% of NH.sub.3 conversion was already reached at 400 C.

TABLE-US-00004 TABLE 4 Results for the catalyst of Example 2 in the conversion of ammonia at 400 C. and 1, 10, and 30 bara of p(NH3) and at 10 bara and various temperatures. Sample from Example 2 (Ru + KOH/ZrO.sub.2) 5000 ppmv H.sub.2O 5000 ppmv H.sub.2O 5000 ppmv H.sub.2O Temperature GHSV = 8000 h.sup.1 GHSV = 8000 h.sup.1 GHSV = 8000 h.sup.1 C. p(NH.sub.3) = 1 bara p(NH.sub.3) = 10 bara p(NH.sub.3) = 30 bara 300 13.2 350 39.4 400 95.5 75.9 63.2 450 94.9 500 97.1 550 98.3 600 98.9

[0167] Thus, as may be taken from the results obtained from the testing of the respective catalysts, a process is provided by the present invention which surprisingly affords a highly effective decomposition of ammonia at high pressures. Furthermore and quite unexpectedly, the process affords a highly effective decomposition at low temperatures despite the high pressure involved. In addition thereto, it has quite unexpectedly been found that the inventive process also affords a highly effective process despite the harsh hydrothermal conditions under high pressure due to water present during the ammonia decomposition reaction when using industrial grade ammonia which contains small amounts of water for stabilization purposes.

Example 5: Preparation of Ru (5 wt.-%) and KOH (5 wt.-%; Corresponding to 3.5 wt.-% K) Supported on MgAl.SUB.2.O.SUB.4 .Spinel

[0168] A hydrotalcite precursor (Pural MG30 from Sasol) was calcined at a temperature in the range of from 850 to 980 C. and for a duration in the range of 1 to 3 h, then used as support. 93 g of the support as molding were impregnated with 27 g of Ru (NO)(NO.sub.3).sub.3 solution (19.7 wt.-% Ru in the solution). After drying at 180 C. for 4 h, the Ru containing molding were impregnated with 5.105 g of K (OH). The resulting material was then dried at 120 C. for 2 h and calcined at 500 C. for 2 h under synthetic air consisting of 21 vol.-% O.sub.2 and 79 vol.-% N.sub.2.

Example 6: Catalytic Tests in NH.SUB.3.-Reforming Under High Pressure

[0169] Prior to testing, the catalyst according to Example 4 was activated in a reducing atmosphere of 5% H.sub.2 in Ar at a temperature of 30 C. (dwell time 1 h, heating rate 2 C./min). After activating the catalyst, the feed was applied (see tables below, NH.sub.3+H.sub.2O+5 vol.-% of Ar). In the respective test, the pressure p(NH.sub.3) was set to 30 bara. The gas hourly space velocity (GHSV) with respect to the NH.sub.3 content was set to 4,000 h.sup.1. The temperatures were varied between 300 and 650 C.

[0170] Table 5 shows the results from the experiment. The H.sub.2O content in the feed was set 5,000 volume-ppm (ppmvol). The temperature was increased in steps of 50 C. The NH.sub.3-conversion is given in %. As may be taken from the results from testing displayed in Table 5, at 500 C. the catalyst approached equilibrium conversion.

TABLE-US-00005 TABLE 5 Results for the conversion of ammonia over the Ru-based catalyst of Example 5. Example 5 (Ru + KOH/ Temperature GHSV H.sub.2O p(NH.sub.3) spinel) C. h.sup.1 ppm vol bara x(NH.sub.3) [%] 300 4,000 5,000 30 4.56 350 4,000 5,000 30 21.80 400 4,000 5,000 30 49.98 450 4,000 5,000 30 81.19 500 4,000 5,000 30 93.30 550 4,000 5,000 30 95.91 600 4,000 5,000 30 97.37 650 4,000 5,000 30 98.26

[0171] As for the testing of the catalysts of Examples 1-3, it may be taken from the results obtained from the testing of the catalyst of Example 5 that a process is provided by the present invention which surprisingly affords a highly effective decomposition of ammonia at high pressures. Furthermore and quite unexpectedly, the process affords a highly effective decomposition at low temperatures despite the high pressure involved. In addition thereto, it has quite unexpectedly been found that the inventive process also affords a highly effective process despite the harsh hydrothermal conditions under high pressure due to water present during the ammonia decomposition reaction when using industrial grade ammonia which contains small amounts of water for stabilization purposes.

CITED PRIOR ART

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