Abstract
A process for the production of methanol (CH.sub.3OH) from carbon dioxide (CO.sub.2) and hydrogen (H.sub.2), wherein CO.sub.2 is reacted with H.sub.2 over a manganese-promoted molybdenum(IV) sulfide catalyst; as well as a catalyst for such a process and a production process for the catalyst.
Claims
1. A process for the production of methanol (CH.sub.3OH) from carbon dioxide (CO.sub.2) and hydrogen (H.sub.2), characterized in that CO.sub.2 is reacted with H.sub.2 over a manganese-promoted molybdenum(IV) sulfide catalyst.
2. A process according to claim 1, characterized in that the reaction takes place at a pressure of ≥10 bar.
3. A process according to claim 1 or claim 2, characterized in that the partial pressure ratio of CO.sub.2 to H.sub.2 is about 1:2.5 to 3.5, preferably approximately 3.
4. A process according to any of claims 1 to 3, characterized in that, while CO.sub.2 is reacted with H.sub.2 over the manganese-promoted molybdenum(IV) sulfide, an inert gas is additionally present.
5. A process according to any of claims 1 to 4, characterized in that the manganese-promoted molybdenum(IV) sulfide catalyst has a composition Mn(0.1 to 0.50)MoS.sub.2.
6. A process according to any of claims 1 to 5, characterized in that the reaction takes place at a temperature between 160° C. and 240° C.
7. A process according to any of claims 1 to 6, characterized in that the source of CO.sub.2 is flue gas.
8. The use of a manganese-promoted molybdenum(IV) sulfide catalyst for the production of methanol (CH.sub.3OH) from carbon dioxide (CO.sub.2) and hydrogen (H.sub.2).
9. A catalyst comprising molybdenum(IV) sulfide promoted with manganese, wherein the manganese-promoted molybdenum(IV) sulfide catalyst has a composition Mn(0.1 to 0.50)MoS.sub.2.
10. A catalyst according to claim 11, characterized in that the catalyst consists of Mn(0.1 to 0.50)MoS.sub.2, preferably Mn(0.2 to 0.4)MoS.sub.2.
11. A process for the production of a manganese-promoted molybdenum(IV) sulfide catalyst, characterized by the steps of: (i) forming a mixture of water, ammonium molybdate ((NH.sub.4).sub.6Mo.sub.7O.sub.24.4H.sub.2O), thiourea (CH.sub.4N.sub.2S) and a water-soluble manganese(II) salt in the desired molar ratio; (ii) raising the temperature of this mixture in an autoclave to 150-250° C. and increasing the pressure to such a level that part of the water remains liquid, maintaining the temperature and pressure until the thiourea decomposes; (iii) washing the mixture from step (ii); (iv) drying the washed mixture from step (iii); (v) calcining the dried and washed mixture from step (iv) under inert gas to obtain the manganese-promoted MoS.sub.2 catalyst.
12. A process according to claim 11, characterized in that, prior to the step (v) of calcining, the mixture is mixed with a carrier.
13. A process according to claim 12, characterized in that the carrier is precipitated from a precursor compound during step (ii).
14. A catalyst for the reaction of carbon dioxide (CO.sub.2) and hydrogen (H.sub.2) to form methanol (CH.sub.3OH), characterized in that the catalytically active part of the catalyst consists of Mn(0.1 to 0.5)MoS.sub.2, preferably Mn(0.2 to 0.4)MoS.sub.2.
15. A catalyst according to claim 14, characterized in that the catalyst has a carrier, with the carrier preferably comprising AlO(OH) and/or Al.sub.2O.sub.3.
Description
DETAILED DESCRIPTION OF THE INVENTION
[0037] Further advantages and details of the invention are shown in the accompanying figures and are explained in further detail in the following description.
[0038] FIG. 1 shows the reaction yield of methanol from the reaction of CO.sub.2 with H.sub.2 over a MoS.sub.2 catalyst promoted with manganese as a function of temperature in a process according to the invention.
[0039] FIG. 2 shows the yield of the reaction of CO with H.sub.2 over a MoS.sub.2 catalyst promoted with manganese as a function of temperature.
[0040] FIG. 3 shows the reaction yield of methanol from the reaction of CO.sub.2 with H.sub.2 as a function of temperature in a process according to the invention over a MoS.sub.2 catalyst promoted with manganese without potassium (.square-solid.) and with potassium (.circle-solid.).
[0041] FIG. 4 shows a comparison of the reaction yields of methanol or, respectively, CH.sub.4 from the reaction of CO.sub.2 with H.sub.2 as a function of temperature in a process according to the invention over a MoS.sub.2 catalyst promoted with manganese without potassium (.square-solid.) and with potassium (.circle-solid.).
[0042] FIG. 5 shows the comparison of the reaction yield with a cobalt-promoted MoS.sub.2 catalyst with potassium starting from CO.sub.2 and H.sub.2.
[0043] FIG. 6 shows the comparison of the reaction yield with a cobalt-promoted MoS.sub.2 catalyst with potassium starting from CO and H.sub.2.
[0044] FIG. 7 shows different catalysts in the reaction of CO.sub.2 with H.sub.2 as a function of temperature.
[0045] FIG. 8 shows a comparison of the reaction yields of methanol or, respectively, CO and CH.sub.4 from the reaction of CO.sub.2 with H.sub.2 in a process according to the invention over various MoS.sub.2 catalysts promoted with manganese with different proportions of Mn and Mo.
[0046] FIG. 9 shows a comparison of the reaction yields of methanol or, respectively, CO and CH.sub.4 from the reaction of CO.sub.2 with H.sub.2 over a Mn(0.30)MoS.sub.2 catalyst in the presence of 20% helium (on the left) and without helium (on the right).
[0047] FIG. 10 shows a comparison of the reaction yields of methanol or, respectively, CO and CH.sub.4 from the reaction of CO.sub.2 with H.sub.2 over a Mn(0.25)MoS.sub.2 catalyst without a carrier (on the left), a MoS.sub.2 catalyst with an AlO(OH) carrier (in the middle) and a Mn(0.25)MoS.sub.2 catalyst with an AlO(OH) carrier (on the right).
[0048] FIG. 11 shows a comparison of the reaction yields of methanol from the reaction of CO.sub.2 with H.sub.2 as a function of temperature over a MnMoS.sub.2 catalyst and a cobalt-promoted MoS.sub.2 catalyst.
[0049] FIG. 12 shows a comparison of the reaction yields of methanol from the reaction of CO with H.sub.2 as a function of temperature over a MnMoS.sub.2 catalyst and a cobalt-promoted MoS.sub.2 catalyst.
[0050] The reaction conditions in the examples shown in the figures at the beginning of the reaction, the way how the gas mixture is passed over the catalyst, are summarized in Table 1.
TABLE-US-00001 Partial Partial Partial Partial Total pressure pressure pressure pressure FIG. pressure CO.sub.2 CO H.sub.2 He FIG. 1 21 bar 20% 0 60% 20% FIG. 2 21 bar 0% 20% 60% 20% FIG. 3 21 bar 20% 0 60% 20% FIG. 4 21 bar 20% 0 60% 20% FIG. 5 21 bar 20% 0 60% 20% FIG. 6 21 bar 0% 20% 60% 20% FIG. 7 21 bar 20% 0 60% 20% FIG. 8 21 bar 20% 0 60% 20% FIG. 9 21 bar 20% 0 60% 20% 21 bar 25% 0 75% 0% FIG. 10 21 bar 20% 0 60% 20% FIG. 11 21 bar 20% 0 60% 20% FIG. 12 21 bar 20% 0 60% 20%
[0051] The total flow of the gas mixture as it is passed over the catalyst is:
[00001]
[0052] In this formula, “ml N” stands for millilitres under normal or standard conditions, i.e., at 273.15 K or 0° C. and 1 bar pressure. The normalization to normal conditions is carried out because, under 21 bar, 1 ml would have a higher molar number than under 1 bar; therefore, the flow is converted and related to the volume flow under normal conditions.
[0053] In FIG. 1, the reaction yield of methanol as a function of temperature in a process according to the invention is shown, when CO.sub.2 is allowed to react with H.sub.2 over a simple molybdenum(IV) sulfide catalyst promoted with manganese. It can be seen very clearly that there is a maximum yield of methanol at around 200° C. to 210° C., while only a few by-products are formed at this temperature. With rising temperature, the formation of methane (CH.sub.4) increases, while the yield of methanol decreases. The amount of carbon monoxide (CO) formed also increases with rising temperature. The ideal temperature range is therefore around 180° C. to 220° C.
[0054] FIG. 2 shows, in comparison to the example of FIG. 1, that the reaction yield of methanol as a function of temperature is extremely low in a process in which CO is allowed to react with H.sub.2 over a molybdenum(IV) sulfide catalyst promoted with manganese. As the temperature rises, the formation of CO.sub.2 and CH.sub.4 begins. CO should therefore be irrelevant during the formation of methanol on said catalyst.
[0055] In FIG. 3, the reaction yields of the reaction CO.sub.2+2H.sub.2.fwdarw.CH.sub.3OH over a simple MoS.sub.2 catalyst promoted with manganese (.square-solid.; see example of FIG. 1) and over a MoS.sub.2 catalyst promoted with manganese further with potassium (.circle-solid.) as a function of temperature in the process according to the invention are compared. As already described in FIG. 1, in case of simple manganese-promoted molybdenum(IV) sulfide, the reaction processes show a maximum yield at around 200 to 210° C. In case of the manganese-promoted MoS.sub.2 catalyst with potassium, the maximum yield shifts to around 280° C. The addition of potassium therefore shifts the maximum yield towards higher temperatures, while a reduction in the yield (mol % based on the CO.sub.2 used) from just under 0.7% to approx. 0.4% can be observed at the same time. However, the disadvantage resulting from the use of the manganese-promoted MoS.sub.2 catalyst with potassium in the form of a lower yield combined with a higher ideal temperature range is accompanied by the advantage of a significant decrease in the formation of CH.sub.4, with CH.sub.4 being an undesirable by-product. This correlation is also illustrated in FIG. 4, where it is evident in this chart that, in case of simple (i.e., potassium-free) manganese-promoted molybdenum (IV) sulfide, the maximum yield of CH.sub.3OH is already associated with a significant increase in the yield of CH.sub.4 at approx. 200 to 210° C. In case of the manganese-promoted MoS.sub.2 catalyst with potassium, the methane yield is still low at the maximum yield for CH.sub.3OH at 280° C.
[0056] FIG. 5 shows the reaction yield of the reaction CO.sub.2+2H.sub.2.fwdarw.CH.sub.3OH as a function of temperature in a process over a MoS.sub.2 catalyst promoted with cobalt. The maximum yield occurs at around 280° C. It is not difficult to see that, in comparison to MoS.sub.2 catalysts promoted with manganese (with and without potassium), not only is the amount of CH.sub.4 formed comparatively high, but especially also the amount of CO formed is so high that this catalyst is mostly unselective for the formation of methanol. The yield of CO is higher by orders of magnitude than that of methanol already at approx. 200° C., and the yield of CH.sub.4 also increases significantly from around 280° C.
[0057] FIG. 6 shows, in comparison to the example of FIG. 5, the reaction yield of methanol as a function of temperature in a process in which CO reacts with H.sub.2 over a cobalt-promoted MoS.sub.2 catalyst with potassium. The yields of methanol and methane are slightly higher overall, but CO.sub.2 is the main product even at low temperatures and from about 300° C. the CH.sub.4 yield exceeds the amount of CH.sub.3OH formed.
[0058] FIG. 7 shows a comparison of the yield of methanol formed in the reaction of CO.sub.2 with H.sub.2 over various catalysts. A nickel-promoted MoS.sub.2 catalyst with potassium (.box-tangle-solidup.) provides the lowest yields. A MoS.sub.2 catalyst promoted with cobalt shows only a slightly higher methanol yield (.circle-solid.). A MoS.sub.2 catalyst with K (.square-solid.) shows significantly better yields, but the highest yields can be found in the process according to the invention with manganese-promoted MoS.sub.2 with potassium (.Math.).
[0059] The chart of FIG. 8 shows the comparison of the reaction yields of methanol (MeOH) or, respectively, CO and CH.sub.4 from the reaction of CO.sub.2 with H.sub.2 in a process according to the invention over various manganese-promoted MoS.sub.2 catalysts with different proportions of Mn and Mo. The abscissa shows the molar proportion of manganese in relation to molybdenum. The maximum methanol yield is from 0.2 to 0.4. (Reaction conditions: 21 bar, 180° C., 20% CO.sub.2, 60% H.sub.2, 20% He, 300 mlN/(g.sub.catalyst*h)
[0060] The column chart of FIG. 9 illustrates the reaction yields of methanol, CH.sub.4 and CO from the reaction of CO.sub.2 with H.sub.2 over a Mn(0.30)MoS.sub.2 catalyst in the presence and absence of helium as an inert gas. The yields of a mixture of 20% CO.sub.2, 60% H.sub.2 and 20% He are illustrated in the left-hand chart, a mixture of 25% CO.sub.2 and 75% H.sub.2 is illustrated in the right-hand chart. It can be seen that the yield of methanol decreases only slightly in the presence of He, surprisingly, the yield of CO decreases at the same time by a significant amount. (The reaction conditions are in each case 21 bar, 180° C., 300 mlN/(g.sub.catalyst*h)).
[0061] The column chart of FIG. 10 illustrates the reaction yields of methanol, CH.sub.4 and CO from the reaction of CO.sub.2 with H.sub.2 over three different catalysts. The left-hand chart shows the yields over a manganese-promoted MoS.sub.2 catalyst (Mn(0.25)MoS.sub.2), the middle chart shows yields on a “simple” MoS.sub.2 catalyst, and the right-hand chart shows those on a manganese-promoted MoS.sub.2 catalyst (Mn(0.25)MoS.sub.2) applied to an AlO(OH) carrier. A significantly higher selectivity of the two manganese-promoted MoS.sub.2 catalysts with regard to methanol can be seen, the significantly lower yields of the undesired by-product CH.sub.4 are particularly striking (reaction conditions: in each case 21 bar, 180° C., 20% CO.sub.2 60% H.sub.2 20%, He 300 mlN/(g.sub.catalyst*h))
[0062] FIG. 11 shows the comparison of the reaction yields of methanol of a manganese-promoted MoS.sub.2 catalyst and a cobalt-promoted MoS.sub.2 catalyst with potassium from the reaction of CO.sub.2 with H.sub.2 as a function of temperature. The reaction yields with the manganese-promoted MoS.sub.2 catalyst are not only higher, but also shifted toward lower temperatures. (Reaction conditions: in each case 21 bar, 180° C., 20% CO.sub.2 60% H.sub.2 20% He, 300 mlN/(g.sub.catalyst*h).
[0063] Furthermore, FIG. 12 shows the comparison of the reaction yields of methanol of a manganese-promoted MoS.sub.2 catalyst and a cobalt-promoted MoS.sub.2 catalyst with potassium from the reaction of CO with H.sub.2 as a function of temperature. In this depiction, the selectivity of the manganese-promoted MoS.sub.2 catalyst can be seen even more clearly. (Reaction conditions: in each case 21 bar, 180° C., 20% CO 60% H.sub.2 20% He, 300 mlN/((g.sub.catalyst*h). Since flue gas can comprise residual amounts of CO, the high selectivity which occurs when flue gas is used as a source for CO.sub.2 constitutes an advantage over other catalysts.
[0064] In contrast to the prior art of sulfur-insensitive catalysts, the selective formation of methanol by means of CO.sub.2 hydrogenation on a manganese-promoted MoS.sub.2 (with or without potassium) catalyst is therefore significantly greater.
