PLASMA CONVERSION REACTOR OF C02 WITH C1 TO C4 HYDROCARBON TO C1 TO C5 OXYGENATE AND METHOD THEREOF

Abstract

An apparatus for forming a C1 to C5 oxygenate from carbon dioxide and a C1 to C4 hydrocarbon is described. The apparatus comprises: a dielectric barrier discharge, DBD, device arranged to generate a plasma; and a passageway having an inlet for the carbon dioxide and the C1 to C4 hydrocarbon and an outlet for the oxygenates. In one example the passageway includes therein a catalyst. The passageway extends, at least in part, through the DBD device wherein, in use, the carbon dioxide in reacted with the C1 to C4 hydrocarbon in the generated plasma, thereby forming the oxygenates from at least some of the carbon dioxide and the C1 to C4 hydrocarbon. The DBD device comprises a conducting liquid as a ground electrode. A method and a use are also described.

Claims

1. An apparatus for forming a C1 to C5 oxygenate from carbon dioxide and a C1 to C4 hydrocarbon, the apparatus comprising: a dielectric barrier discharge, DBD, device arranged to generate a plasma; and a passageway including an inlet for the carbon dioxide and the C1 to C4 hydrocarbon and an outlet for the oxygenates, wherein the passageway extends, at least in part, through the DBD device wherein, in use, the carbon dioxide and the C1 to C4 hydrocarbon are reacted in the generated plasma, thereby forming the C1 to C5 oxygenate from at least some of the carbon dioxide and the C1 to C4 hydrocarbon and wherein the DBD device comprises a conducting liquid electrode.

2. The apparatus according to claim 1, wherein the C1 to C4 hydrocarbon is selected from methane, ethane, propane and mixtures thereof, preferably wherein the C1 to C4 hydrocarbon is methane.

3. The apparatus according to any preceding claim, wherein the liquid electrode is a water electrode or a sodium chloride electrode, preferably wherein the liquid electrode is a water electrode.

4. The apparatus according to any preceding claim, wherein the apparatus comprises a transition metal catalyst, preferably wherein the apparatus comprises a transition metal oxide catalyst selected from zinc oxide, copper oxide, cerium oxide, iron oxide and nickel oxide.

5. The apparatus according to claim 4, wherein the transition metal catalyst is held on a support, preferably wherein the support is selected from the group consisting of SiO.sub.2, TiO.sub.2, Al.sub.2O.sub.3, CeO.sub.2, ZrO.sub.2, ZnO, Cr.sub.2O.sub.3, carbon nanotubes, Ga.sub.2O.sub.3, In.sub.2O.sub.3 and zeolite.

6. The apparatus according to any of claims 1 to 3, wherein the apparatus comprises a catalyst selected from the group consisting of TiO.sub.2, CeO.sub.2, SiO.sub.2, Al.sub.2O.sub.3, ZrOs, ZSM-5 and SAPO.

7. A method of forming a C1 to C5 oxygenate from carbon dioxide and a C1 to C4 hydrocarbon, the method comprising: generating a plasma using a dielectric barrier discharge, DBD, device; and reacting the carbon dioxide and the C1 to C4 hydrocarbon in the generated plasma, thereby forming the C1 to C5 oxygenate from at least some of the carbon dioxide and the C1 to C4 hydrocarbon; wherein the DBD device comprises a liquid electrode.

8. The method according to claim 7, wherein reacting the carbon dioxide and the C1 to C4 hydrocarbon comprises reacting the carbon dioxide and the C1 to C4 hydrocarbon at approximately ambient temperature.

9. The method according to claim 7 or 8, wherein reacting the carbon dioxide and the C1 to C4 hydrocarbon comprises reacting the carbon dioxide and the C1 to C4 hydrocarbon at approximately ambient pressure.

10. The method according to any of claims 7 to 9, wherein generating the plasma using the DBD device comprises generating a stable plasma in a time in a range of from 1 to 60 minutes, preferably in a range of from 2 to 45 minutes, more preferably in a range of from 3 to 30 minutes, most preferably in a range of from 4 to 20 minutes.

11. The method according to any of claims 7 to 10, wherein the conversion of carbon dioxide and/or conversion of C1 to C4 hydrocarbon is in a range from 10 to 50%, preferably in a range from 30 to 50%.

12. The method according to any of claims 7 to 11, wherein the selectivity of methanol is in a range from 20 to 70%, preferably in a range from 30 to 70%, most preferably in a range from 50 to 70%.

13. The method according to any of claims 7 to 12, wherein the molar ratio of carbon dioxide to C1 to C4 hydrocarbon is 1:1.

14. The method according to any of claims 7 to 13, wherein the method comprises supplying a specific energy input in a range of 15 to 60 kJ/L.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0077] For a better understanding of the invention, and to show how exemplary embodiments of the same may be brought into effect, reference will be made, by way of example only, to the accompanying diagrammatic Figures, in which:

[0078] FIGS. 1A and 1B show a schematic diagram of experimental setup;

[0079] FIGS. 2A to 2D show the effect of specific energy input (SEI) on the synthesis of methanol;

[0080] FIGS. 3A to 3D show the effect of different residence times on the reaction;

[0081] FIGS. 4A to 4D shows the effect of different CH.sub.4/CO.sub.2 ratios on the reaction;

[0082] FIGS. 5A to 5D show the effect of catalyst on the synthesis of liquid products;

[0083] FIGS. 6A to 6D show the effect of different SiO2 packed sizes (mesh) on the reaction;

[0084] FIG. 7A shows conversion of CO.sub.2 and CH.sub.4; FIG. 7B shows selectivity of CO and H.sub.2; FIG. 7C shows selectivity of C2-C4 hydrocarbons; and FIG. 7D shows selectivity of liquid products (M/AI refers to the metal oxides loading on Al.sub.2O.sub.3); and

[0085] FIG. 8 shows an XRD analysis of various catalysts.

EXAMPLES

[0086] The experiments were conducted in a coaxial DBD reactor with a special and novel electrode design, as shown in FIGS. 1A and 1B. Compared to traditional DBD reactors using metal as a ground electrode, this reactor used circulating water as both a ground electrode and cooling of the reactor. A cooling circulation bath (Grant LT Ecocool 150) was used to control the temperature of the discharge at 20° C. The length of the discharge region was 50 or 30 mm and the discharge gap was 3 or 2 mm. The DBD reactor was connected to an AC high voltage power supply with a peak voltage of up to 30 kV. The DBD discharge power maintained at 20 W and the frequency was fixed at 9.2 kHz. CO.sub.2 and CH.sub.4 were used as reactants at a total flow rate of 40 or 30 mL/min and a 1:1 molar ratio was used.

[0087] The applied voltage of the DBD was measured by a high-voltage probe (TESTEC, HVP-15HF), while the current was recorded by a current monitor (Bergoz, CT-E0.5). The voltage on the external capacitor was used to measure the charge formed in the DBD. All the electrical signals were sampled by a four-channel digital oscilloscope (Tektronix, MDO 3024). A custom system was used to monitor and control the discharge power of the DBD in real-time. The gas temperature in the discharge area near the catalyst bed was measured using a fiber optical thermometer (Omega, FOB102).

[0088] The gaseous products were analyzed using a gas chromatograph (Shimadzu GC-2014) equipped with a thermal conductivity detector (TCD) and a flame ionized detector (FID). A water/ice mixture bath was placed at the exit of the DBD reactor to condense liquid products. The oxygenates were qualitatively analyzed using a gas chromatography-mass spectrometer (GC-MS, Agilent GC 7820A and Agilent MSD 5973) and quantitatively analyzed using a gas chromatograph (Agilent 7820) equipped with a FID with a DB-WAX column. The change of the gas volume before and after the reaction was measured using a soap-film flow meter. Sampling and measurements started after running the reaction for 1 h and lasted for 3 h. Each measurement was repeated three times, and the measurement error was less than 4%.

Example 1

[0089] The conversion of CH.sub.4 and CO.sub.2 increases with the increase of SEI (in a range of 15-60 kJ/L). FIG. 2C shows that the distribution of oxygenates can be tuned tailored with the increase of the input powers. Higher power (SEI) leads to generate more gas products and less oxygenates. Methanol, ethanol, acetic acid and acetone are found as major liquid products. Compared to our previous work, the dominant liquid product has been changed from acetic acid to methanol in this study. The highest methanol selectivity reaches 38 % at the optimal SEI of 26.3 kJ/L, while the highest selectivity of acetic acid is 24% at a low SEI of 15 kJ/L.

[0090] The conversion of CO.sub.2 and CH.sub.4 is affected by the change of the residence time of the reactants. FIG. 3D shows the selectivity of methanol is not significantly affected by the change of the residence time.

[0091] FIGS. 4 shows CH.sub.4/CO.sub.2 molar ratio is an important parameter affecting the conversion. The highest selectivity of liquid products is obtained at a CH.sub.4/CO.sub.2 ratio of 1:1. The highest selectivity of methanol is 38%. Increasing CH.sub.4/CO.sub.2 ratio produces more hydrocarbons such as C2-C4 due to the presence of more methane in the feed.

Example 2

[0092] The conversion of CH.sub.4 and CO.sub.2, and their product selectivities could be significantly influenced by the catalysts. Methanol, ethanol and formic acid are found as major liquid products. The method using TiO.sub.2 as a catalyst achieves the highest liquid selectivity at 60.4 %, while it also shows the lowest conversion (FIGS. 5A to 5D).

[0093] The conversions of CO.sub.2 and CH.sub.4 are affected by the change of the packed sizes of the catalysts. Different sizes could considerably change the plasma properties in the discharge area, and thus influence the product selectivities.

[0094] FIGS. 6A to 6D show that the powder SiO.sub.2 has the best catalytic performance for liquid product synthesis.

Example 3

[0095] Compared to the reaction using plasma only (without a catalyst), the conversion of CH.sub.4 and CO.sub.2 increases when using different metal oxides (including Ni, Fe, Cu, and Zn) loaded on Al.sub.2O.sub.3. And, FeO.sub.x/Al.sub.2O.sub.3 catalyst could increase the conversion of CH.sub.4 and CO.sub.2 by around 5% and 10%, respectively. But there were slight decreases of both CH.sub.4 and CO.sub.2 when packing with CeO.sub.x/Al.sub.2O.sub.3.

[0096] FIGS. 7B and 7C show the selectivity of gaseous products for the DRM reaction. CO, H.sub.2 were confirmed as the main gaseous products, which could both reach a peak at around 22% when using Ce/Al catalyst. On the contrary, Fe/AI shows the lowest selectivity of gaseous products, but the highest liquid selectivity.

[0097] Methanol, ethanol, acetic acid and acetone are found as major liquid products. The highest methanol selectivity reaches 62 % at a SEI of 26.3 kJ/L.

[0098] BET results

TABLE-US-00001 Samples Metal loading (wt. %) Surface area (m.sup.2/g) Total pore volume (cm.sup.3/g) Al.sub.2O.sub.3 - 221 0.43 NiO.sub.x/Al.sub.2O.sub.3 5 191 0.37 FeO.sub.x/Al.sub.2O.sub.3 5 188 0.36 CeO.sub.x/Al.sub.2O.sub.3 5 175 0.33 CuO.sub.X/Al.sub.2O.sub.3 5 182 0.37 ZnO.sub.x/Al.sub.2O.sub.3 5 192 0.37

XRD Analysis

[0099] FIG. 8 shows the XRD patterns of metallic oxide catalysts, and it confirms that all of the loaded metal sites over the surface are metal oxides.

[0100] Attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

[0101] All of the features disclosed in this specification (including any accompanying claims and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at most some of such features and/or steps are mutually exclusive.

[0102] Each feature disclosed in this specification (including any accompanying claims, and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

[0103] The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.