Nickel-containing catalyst composition having enhanced acidity for autothermal reforming processes

Abstract

Modified red mud catalyst compositions, methods for production, and methods of use in autothermal reforming, the composition comprising: red mud material produced from an alumina extraction process from bauxite ore; and nickel oxide, the nickel oxide present at between about 5 wt. % to about 40 wt. % of the modified red mud catalyst composition.

Claims

1. A method for autothermal reforming over a modified red mud catalyst composition, the method comprising the steps of: providing a methane feed with oxygen and carbon dioxide to react in an autothermal reforming reaction over the modified red mud catalyst composition at a temperature between about 500° C. to about 1000° C. and a pressure between about 5 bar and about 20 bar to produce synthesis gas comprising H.sub.2 and CO, the modified red mud catalyst composition comprising: red mud material produced from an alumina extraction process from bauxite ore with a weight ratio of aluminum oxide to iron oxide of about 1:0.74 and a weight ratio of aluminum oxide to titanium oxide of about 1:0.27; and nickel oxide, the nickel oxide present at between about 5 wt. % to about 40 wt. % of the modified red mud catalyst composition.

2. The method according to claim 1, where the temperature is between about 600° C. to about 800° C.

3. The method according to claim 1, where the temperature is about 750° C.

4. The method according to claim 1, where the pressure is between about 10 bar and about 15 bar.

5. The method according to claim 1, where the pressure is about 14 bar.

6. The method according to claim 1, where gas hourly space velocity of the methane feed with oxygen and carbon dioxide is between about 1000 h.sup.−1 to 10000 h.sup.−1.

7. The method according to claim 1, where the composition includes at least one component selected from the group consisting of: Fe.sub.2O.sub.3, Al.sub.2O.sub.3, SiO.sub.2, Na.sub.2O, CaO, and TiO.sub.2.

8. The method according to claim 1, where the modified red mud catalyst composition comprises particles and where a majority of the particles of the modified red mud catalyst composition have a particle size of less than about 70 μm.

9. The method according to claim 1, where the nickel oxide is present at between about 10 wt. % to about 30 wt. % of the modified red mud catalyst composition.

10. The method according to claim 1, where the nickel oxide is present at between about 15 wt. % to about 25 wt. % of the modified red mud catalyst composition.

11. The method according to claim 1, where the nickel oxide is present at about 20 wt. % of the modified red mud catalyst composition.

12. The method according to claim 1, where methane conversion is greater than at least about 40% for at least about 6 hours.

13. The method according to claim 1, where a molar ratio is about 2:1:1 for CH.sub.4:CO.sub.2:O.sub.2.

14. The method according to claim 1, where produced H.sub.2 is at least about 25 mol. % of produced products from the reaction for at least about 5 hours.

15. The method according to claim 1, where the Brunauer-Emmett-Teller (BET) surface area of the modified red mud catalyst composition is between about 50 m.sup.2/g and about 90 m.sup.2/g.

16. The method according to claim 1, where the composition includes between about 2 wt. % and about 10 wt. % CaO, and between about 5 wt. % and about 20 wt. % SiO.sub.2.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) These and other features, aspects, and advantages of the present disclosure will become better understood with regard to the following descriptions, claims, and accompanying drawings. It is to be noted, however, that the drawings illustrate only several embodiments of the disclosure and are therefore not to be considered limiting of the disclosure's scope as it can admit to other equally effective embodiments.

(2) FIG. 1 is a graph showing conversion percentage for CH.sub.4 in an autothermal reforming process for unmodified red mud (RM) used as a catalyst and for acid nickel-modified red mud (ANMRM) used as a catalyst.

(3) FIG. 2 is a graph showing mol. % of H.sub.2 out of the total products produced from autothermal reforming of CH.sub.4 in an autothermal reforming process for unmodified red mud used as a catalyst and for ANMRM used as a catalyst.

DETAILED DESCRIPTION

(4) So that the manner in which the features and advantages of the embodiments of compositions of nickel-modified red mud along with systems and methods for autothermal reforming with such compositions and for producing such compositions, may be understood in more detail, a more particular description of the embodiments of the present disclosure briefly summarized previously may be had by reference to the embodiments thereof, which are illustrated in the appended drawings, which form a part of this specification. It is to be noted, however, that the drawings illustrate only various embodiments of the disclosure and are therefore not to be considered limiting of the present disclosure's scope, as it may include other effective embodiments as well.

(5) As noted, red mud is a caustic waste material generated during alumina extraction from bauxite ore. Red mud includes a mixture of transition metals, for example as listed in Table 1.

(6) TABLE-US-00001 TABLE 1 Example composition ranges for global red mud. Component Fe.sub.2O.sub.3 Al.sub.2O.sub.3 SiO.sub.2 Na.sub.2O CaO TiO.sub.2 Approx. 30-60% 10-20% 3-50 % 2-10% 2-8% 10% Weight Percentage

(7) Red mud was modified with nickel to be utilized and tested as a catalyst for autothermal reforming as follows. The unmodified red mud used as a catalyst precursor contained no detectable nickel. Saudi Arabian red mud from Ma'aden Aluminium Company, based at Ras Al Khair, Saudi Arabia was used to prepare a modified catalyst composition. Table 2 shows the weight percent for certain components in the unmodified Saudi Arabian red mud composition.

(8) TABLE-US-00002 TABLE 2 Certain component weight percentages in unmodified Saudi Arabian red mud (RM) catalyst/catalyst support composition. Component Fe.sub.2O.sub.3 Al.sub.2O.sub.3 SiO.sub.2 Na.sub.2O CaO TiO.sub.2 Weight 18.75% 25.22% 18.88% 11.77% 7.97% 6.89% Percentage

(9) The untreated red mud exhibited a Brunauer-Emmett-Teller (BET) surface area of about 16 m.sup.2/g.

(10) Table 3 shows an example composition for one embodiment of produced ANMRM for use as a modified catalyst.

(11) TABLE-US-00003 TABLE 3 Example composition for a produced ANMRM used as a catalyst. Component Fe.sub.2O.sub.3 Al.sub.2O.sub.3 SiO.sub.2 Na.sub.2O CaO TiO.sub.2 NiO Weight 32% 12.4% 8.5% 0.08% 3.8% 15% 24% Percentage

(12) Because red mud is a highly variable waste material, elemental composition will vary between samples and test results.

(13) Catalyst Preparation. An acid nickel-modified red mud (ANMRM) catalyst with 18.6 wt. % nickel metal was prepared using a homogeneous precipitation process. Using an unmodified red mud catalyst precursor, 20 wt. % of nickel was targeted to be loaded in the red mud to enhance autothermal reforming activity, and 18.6 wt. % of nickel was confirmed by X-ray fluorescence (XRF) analysis (about 24% nickel oxide, also referred to as NiO). Depending on the catalyst application, nickel oxide can be loaded to a red mud precursor from between about 1 wt. % to about 50 wt. %. Nickel can be combined with red mud to result in nickel(II) oxide, NiO, in addition to or alternative to nickel(III) oxide, Ni.sub.2O.sub.3.

(14) BET surface area analysis showed unmodified red mud surface area was about 16 m.sup.2/g. BET surface area for acid modified red mud was about 170 m.sup.2/g. BET surface area for acid modified red mud with nickel in addition to or alternative to molybdenum loading is, in some embodiments, between about 50 m.sup.2/g and about 90 m.sup.2/g, for example about 63 m.sup.2/g or about 89 m.sup.2/g.

(15) First, 10 g of Saudi Arabian red mud from Ma'aden Aluminium Company, based at Ras Al Khair, Saudi Arabia was modified by dissolving dried, unmodified red mud in 100 mL of deionized water, and then the pH was neutralized using 40.5 mL of 37 wt. % hydrochloric acid. Afterward, 10 g of nickel(II) nitrate hexahydrate was dissolved in 50 mL of ethanol. The two solutions were mixed, and the final solution was precipitated by slowly adding between about 20 mL to about 30 mL aqueous ammonia with stirring until pH reached 8. Then, the mixed solution was filtered, dried in an oven at 105° C., and calcined at 600° C. for 4 hours. The final ANMRM product was ground to have a particle size of less than about 70 μm. The step of drying in an oven can last from about 2 to about 24 hours.

(16) Other nickel-containing compounds can be used in addition to or alternative to nickel nitrate, including any nickel-containing compounds soluble in ethanol or other organic or inorganic alcohols, or in aqueous ammonia. Nickel can be combined with red mud to result in nickel(II) oxide, NiO, in addition to or alternative to nickel(III) oxide, Ni.sub.2O.sub.3.

(17) Catalyst testing. Several tests on red mud catalytic activity and ANMRM catalytic activity for autothermal reforming were experimentally conducted. Red mud was tested as received without any modifications. It was placed in in a Micromeritics® PID Eng & Tech brand microactivity reactor designed for catalyst activity and selectivity analysis, and the same was done for the prepared ANMRM catalyst. The results are compared, for example, in FIGS. 1 and 2. Results show that ANMRM catalytic activity for autothermal reforming is advantageously improved over non-modified red mud catalytic activity for autothermal reforming.

(18) FIG. 1 is a graph showing conversion percentage for CH.sub.4 in an autothermal reforming process for unmodified red mud (RM) used as a catalyst and for ANMRM used as a catalyst. Effects of nickel addition to red mud were studied. Experimental conditions in the autothermal reforming reactor included temperature at about 750° C., pressure at about 14 bar, and gas hourly space velocity (GHSV) at about 3517 h.sup.−1. The test was conducted for 7 hours. The feed was 50 mol. % methane, 25 mol. % CO.sub.2, and 25 mol. % O.sub.2 for both catalysts tested. The GHSV was calculated for the mixed feed. GHSV generally measures the flow rate of the feed gases divided by the catalyst volume, which indicates the residence time of the reactants on the catalyst. For autothermal reforming, the feed composition can comprise, consist of, or consist essentially of CH.sub.4, CO.sub.2, and 02. Based in part on thermodynamics, the molar ratio can be about 2:1:1 for CH.sub.4:CO.sub.2:O.sub.2.

(19) Methane conversion illustrated in FIG. 1 shows ANMRM catalyst outperformed its counterpart, the untreated red mud. Methane conversion by ANMRM reached up to about 65%. On the other hand, unmodified red mud methane conversion maxed out at about 40%. Slight conversion activity of unmodified red mud could be attributed to the existence of several transition metals within red mud, and the greater conversion rate of ANMRM can be attributed to the addition of nickel and synergies of the nickel with the existing transition metals in the red mud.

(20) FIG. 2 is a graph showing mol. % of H.sub.2 out of the total products produced from autothermal reforming of CH.sub.4 in an autothermal reforming process for unmodified red mud used as a catalyst and for ANMRM used as a catalyst. Hydrogen production illustrated in FIG. 2 shows that untreated red mud produced low amounts of hydrogen, whereas ANMRM catalyst produced up to about 35 mol. % hydrogen. Nickel modification of red mud has enhanced the performance significantly.

(21) The singular forms “a,” “an,” and “the” include plural referents, unless the context clearly dictates otherwise. The term “about” when used with respect to a value or range refers to values including plus and minus 5% of the given value or range.

(22) In the drawings and specification, there have been disclosed example embodiments of the present disclosure, and although specific terms are employed, the terms are used in a descriptive sense only and not for purposes of limitation. The embodiments of the present disclosure have been described in considerable detail with specific reference to these illustrated embodiments. It will be apparent, however, that various modifications and changes can be made within the spirit and scope of the disclosure as described in the foregoing specification, and such modifications and changes are to be considered equivalents and part of this disclosure.