Patent Application
20230149915
The present disclosure relates to a catalyst for oxidative coupling of methane, the catalyst comprising palladium supported on a cerium palladium solid solution, and a method for oxidative coupling using the same and, more specifically, to a catalyst having palladium supported on a solid solution formed of cerium oxide and palladium oxide, a catalyst produced by subjecting the same to a leaching treatment, and a method for oxidative coupling of methane using the same.
The present disclosure was made with the support of the Ministry of Science and ICT in Korea under Project No. 2019000551, which was carried out in the program entitled “(EZBARO) Development of noble metal single atom-based heterogeneous catalyst for selective direct oxidation of methane (2019)” in the project named “Source technology development business” by the Korea Advanced Institute of Science and Technology under management of the National Research Foundation of Korea, from 1 Jan. 2019 to 31 Dec. 2019.
The present patent application claims priority to and the benefit of Korean Patent Application No. 10-2019-0121114 filed in the Korean Intellectual Property Office on 30 Sep. 2019, the disclosure of which is incorporated herein by reference.
The concerns about the depletion of petroleum resources and the abundant reserves of shale gas are increasing interest in the selective conversion of methane gas as a main component thereof. Therefore, studies on the conversion of methane to another useful higher value-added compound (ethane, ethylene, methanol, or the like) are actively being conducted.
However, methane has a stable molecular structure (inertness) and strong C—H bonds, and thus existing methane conversion processes have the limitation of being an inefficient process since the activation of methane is attained in the process conditions of high temperatures (>1000 K) and high pressures (>30 bar) [Accounts Chem. Res. 2017, 50, 418-425].
Moreover, selective methane oxidation has many difficulties since a compound, such as methanol or ethane, as a product, is easily oxidized compared with methane [Nat. Mater. 2017, 16, 225-229].
Pd/CeO2 catalyst in which Pd nanoparticles are dispersed on cerium oxide (ceria) has been widely used in the oxidation, such as Co oxidation, benzyl alcohol oxidation, and methane combustion. The Pd surface can be easily oxidized, and the formed PdO may act as an oxidation catalyst. The interface between Pd and cerium oxide often acts as an efficient active site for oxidation at low temperatures. It has been specifically reported that Pd can be highly oxidized on cerium oxide in which the ratio of Pd to O is smaller than 1. The methane activation of Pd has been studied, and it was found that the energy barrier was lower in PdO rather than the metal Pd.
A method for stably producing C2 compounds for a long time through oxidative coupling of methane (hereinafter, OCM) at low temperatures by using a highly oxidative Pd/CeO2 catalyst has been provided, but the catalyst is easily reduced (inactivated) due to a limitation of oxygen activation in a catalytic reaction, resulting in a low rate of production of ethane.
The present inventors had made efforts for developing a method for stably producing C2 compounds for a long time by using methane at low temperatures. As a result, the present inventors had developed a method for producing C2 compounds through oxidative coupling of methane (hereinafter, OCM) at low temperatures by using highly oxidative Pd/CePdO and CePdO catalysts.
An aspect of the present disclosure is to provide a method for producing a catalyst for oxidative coupling of methane, the method including:
mixing a cerium oxide precursor solution and a palladium oxide precursor solution; and
subjecting a product of the mixing to calcination.
Another aspect of the present disclosure is to provide a catalyst for oxidative coupling of methane (OCM), the catalyst comprising palladium supported on CePdO solid solution.
Still another aspect of the present disclosure is to provide a method for oxidative coupling of methane, the method including adding to methane a catalyst for oxidative coupling of methane (OCM) to form a hydrocarbon compound comprising two or more carbon atoms from the methane, the catalyst comprising palladium supported on CePdO solid solution.
Still another aspect of the present disclosure is directed to use of a catalyst comprising palladium supported on CePdO solid solution for inducing oxidative coupling from methane.
The present disclosure relates to a catalyst for oxidative coupling of methane, the catalyst comprising palladium supported on a cerium palladium solid solution, and a method for oxidative coupling using the same.
As used herein, the term “solid solution” refers to a solid mixture having a continuously changing chemical composition within a predetermined range in the same crystal structure.
The present inventors had made efforts for developing a method for stably producing C2 compounds for a long time by using methane at low temperatures. As a result, the present inventors had developed a method for producing C2 compounds through oxidative coupling of methane (hereinafter, OCM) at low temperatures by using highly oxidative Pd/CePdO and CePdO catalysts.
As used herein, the term “Pd/CePdO catalyst” refers to a palladium catalyst supported on CePdO solid solution, and herein, the Pd/CePdO catalyst has the same meaning as Pd/CexPd1-xO2-y catalyst.
As used herein, the term “CePdO solid solution” refers to a solid mixture having a continuously changing chemical composition of Ce, Pd, and O within a predetermined range in the same crystal structure, and herein, the CePdO solid solution has the same meaning as CexPd1-xO2-y solid solution.
As used herein, the term “oxidative coupling” refers to a reaction in which two methane atoms are combined with each other to produce a hydrocarbon compound comprising C2, like in ethane or ethylene, or more carbon atoms.
As used herein, the term “hydrocarbon compound” refers to an organic compound composed of only carbon and hydrogen. The hydrocarbon compound includes aliphatic hydrocarbons (saturated hydrocarbons and unsaturated hydrocarbons), alicyclic hydrocarbons, and aromatic hydrocarbons.
As used herein, the term “C2 hydrocarbon compound” refers to a hydrocarbon compound having two carbon atoms. For example, the C2 hydrocarbon compound includes ethane, ethylene, acetylene, or the like, but is not limited thereto.
Hereinafter, the present disclosure will be described in detail.
In accordance with an aspect of the present disclosure, there is provided a method for producing a catalyst for oxidative coupling of methane (OCM), the method including:
mixing a cerium oxide precursor solution and a palladium oxide precursor solution; and
subjecting a product of the mixing to calcination.
As used herein, the term “calcination” refers to heating to high temperatures in air or oxygen. In the present disclosure, for oxidation of a catalyst at high temperatures through air, heat treatment, that is, calcination, was conducted.
The cerium oxide precursor solution may be an aqueous solution of (NH4)2Ce(NO3)6, Ce(NO3)3.6H2O, CeCl3, Ce(SO4)2, Ce(CH3CO2)3, Ce(OH)4, Ce2(C2O4)3 or a mixture of two or more thereof, and for example, (NH4)2Ce(NO3)6, but is not limited thereto.
The palladium oxide precursor solution is an aqueous solution of Pd(NO3)2, PdCl2, or a mixture of two or more thereof.
The palladium oxide precursor solution may further contain nitro ethane (C2H5NO2). The nitro ethane serves as a fuel in the calcination step at 350° C., thereby enabling the instant formation of a solid product together with flame.
The calcination step may be performed in the presence of air at 350-900° C., 600-900° C., or 600-800° C., and for example, 600-700° C., but is not limited thereto.
The calcination step may be performed for 12-48 hours, 12-36 hours, 12-24 hours, 12-18 hours, 16-48 hours, 16-36 hours, or 16-24 hours, and for example, 16-18 hours, but is not limited thereto.
In an embodiment of the present disclosure, when the calcination was conducted at a calcination temperature of 600-700° C. for 16-18 hours, PdO was sufficiently oxidized to show the highest reactivity.
The above method may further include a step of subjecting a product of the calcination step to a leaching treatment. For example, the leaching treatment may be conducted by immersing the product in nitric acid, but is not limited thereto.
As used herein, the term “leaching” refers to extracting a target component in a solid out of the solid through dissolution.
The leaching treatment step may be performed at 200-300° C., and for example, 225-275° C., but is not limited thereto.
The leaching treatment step may be performed for 1-3 hours, and for example, 1-2 hours, but is not limited thereto.
In an embodiment of the present disclosure, when the leaching treatment was performed at 225-275° C. for 1-2 hours, the Pd nanoparticles on the surface could be sufficiently leached.
In accordance with another aspect of the present disclosure, there is provided a catalyst for oxidative coupling of methane (OCM), the catalyst comprising palladium supported on CePdO solid solution.
According to an embodiment of the present disclosure, the catalyst for oxidative coupling of methane is PdO/CexPd1-xO2-y in which x is 0<x<1 and y is 0≤y<2.
The palladium may be present as a particle on a surface of the catalyst, and may be present as an ion in the lattice of the catalyst.
In accordance with still another aspect of the present disclosure, there is provided a method for oxidative coupling of methane, the method including adding to methane a catalyst for oxidative coupling of methane (OCM) to form a hydrocarbon compound comprising two or more carbon atoms from the methane, the catalyst comprising palladium supported on CePdO solid solution.
According to the present disclosure, a hydrocarbon compound (for example, C2 hydrocarbon compounds, such as ethane) can be produced at low temperatures and a small amount of oxygen is used unlike a general methane oxidation reaction, leading to a significant reduction in costs in terms of a separation process.
According to an embodiment of the present disclosure, the hydrocarbon compound includes alkane, alkene, and alkyne compounds, wherein the alkane compound is a hydrocarbon compound of the molecular formula CnH2n+2, the alkene compound is a hydrocarbon compound of the molecular formula CnH2n, and the alkyne compound is a hydrocarbon compound of the molecular formula CnH2n-2.
According to another embodiment of the present disclosure, the hydrocarbon compound is an alkane compound.
According to an embodiment of the present disclosure, the hydrocarbon compound is an alkane C2 hydrocarbon compound, and may be for example ethane, but is not limited thereto.
The step of forming a hydrocarbon compound may be performed by adding methane, oxygen, and the catalyst for oxidative coupling into a reactor.
According to an embodiment of the present disclosure, the reactor is selected from the group consisting of a fixed bed reactor, a fluidized bed reactor, and a membrane reactor.
The step of forming a hydrocarbon compound from methane of the present disclosure is performed in a temperature range of 390° C. or lower. According to an embodiment of the present disclosure, the step of forming a hydrocarbon compound of the present disclosure is performed in a temperature range of 230-390° C.
According to an embodiment of the present disclosure, the step of forming a hydrocarbon compound is performed by adding a moisture adsorbent.
According to an embodiment of the present disclosure, the moisture adsorbent is zeolite.
According to an embodiment of the present disclosure, the moisture adsorbent is a heat-treated moisture adsorbent.
According to an embodiment of the present disclosure, the heat-treated moisture adsorbent is a moisture adsorbent heat-treated at 100-500° C. More specifically, the heat-treated moisture adsorbent is a moisture adsorbent heat-treated at 100-200° C., 100-300° C., 100-400° C., 200-300° C., 200-400° C., 200-500° C., 300-400° C., 300-500° C., or 400-500° C. According to an example of the present disclosure, the step of forming a hydrocarbon compound by adding zeolite heat-treated at 300-400° C. is performed to improve the C2H6 production yield
According to an embodiment of the present disclosure, the catalyst for oxidative coupling is 5-100 mg in weight.
According to an embodiment of the present disclosure, the catalyst for oxidative coupling has a weight of 5-25 mg, 10-25 mg, 10-50 mg, or 25-100 mg.
According to an embodiment of the present disclosure, the step of forming a hydrocarbon compound is performed in a condition not including water.
According to an embodiment of the present disclosure, the step of forming a hydrocarbon compound is performed in a condition including 0.5-4% of water. More specifically, the step of forming a hydrocarbon compound is performed in a condition including 0.5-3%, 0.5-2%, 0.5-1%, 1-4%, 1-3%, 1-2%, 2-4%, or 2-3% of water. Most specifically, the step of forming a hydrocarbon compound is performed in a condition including 0.7-1.1% of water. According to an example of the present disclosure, the C2H6 production yield of the catalyst appeared to be high in a condition not including moisture.
According to the present disclosure, the present disclosure is directed to a catalyst for oxidative coupling of methane, the catalyst comprising palladium supported on a cerium palladium solid solution, and a method for oxidative coupling using the same, wherein highly oxidative Pd/CePdO and CePdO catalysts can be used in the production of C2 hydrocarbon compounds through oxidative coupling of methane, hereinafter OCM) at low temperatures.
Hereinafter, the present disclosure will be described in more detail with reference to the following examples. However, these examples are given for illustrating the present disclosure, and the scope of the present disclosure is not limited thereto.
Throughout the present specification, the “%” used to express the concentration of a specific material, unless otherwise particularly stated, refers to (wt/wt) % for solid/solid, (wt/vol) % for solid/liquid, and (vol/vol) % for liquid/liquid.
PdO/CexPd1-xO2-y catalyst was typically synthesized by a solution-combustion method (
The mixture was stirred to make a homogenous solution and moved to a crucible, and then the crucible was introduced into a furnace maintained at 350° C. Initially, the solution was boiled with frothing and foaming, and ignited to burn with a flame, yielding a solid product. The solid was ground in a mortar, and calcined at 650° C. in air for 16 hours. The sample was named “Pd/CePdO”.
The calcined PdO/CexPd1-xO2-y was subjected to a leaching treatment with nitric acid to prepare CexPd1-xO2-y support.
Specifically, 0.1 g of PdO/CexPd1-xO2-y was immersed in nitric acid (SAMCHUN, 60%) at 250° C. for 1 hour, and filtered with deionized water to remove residual NO3− in the sample. This leaching process was repeated three times to obtain clear CexPd1-xO2-y support. The washed sample was dried at 80° C. overnight. Finally, CexPd1-xO2-y support was successfully prepared without PdO particles on the surface thereof. The final CexPd1-xO2-y sample was indicated as “CePdO”.
1-3. Synthesis of Pd/CeO2 Catalyst
CeO2 support as a comparative example was synthesized using a co-precipitation method. 1.0 g of Ce(NO3)3.6H2O (99.99%, Kanto chemical) was dissolved in 23.5 mL of deionized water with slow stirring. Ammonia water (25-30% NH4OH, Ducksan) was added dropwise until the pH of the solution reached 8.5. The produced yellow slurry was filtered, and the obtained precipitate was dried, and calcined at 773 K in air for 5 hours.
Pd/CeO2 was synthesized by using a deposition-precipitation method. 0.38 g of CeO2 powder was dispersed in 5 mL of deionized water. H2PdCl4 solution was prepared such that the molar ratio of PdCl2 (99%, Sigma-Aldrich) and HCl (35-37%, Samchun) in deionized water was 1:2. Na2CO3 solution was prepared by dissolving 0.53 g of Na2CO3 (99.999%, Sigma-Aldrich) in 10 mL of deionized water. H2PdCl4 solution (up to 1 mL) containing 0.016 g of Pd was dropped in CeO2 solution under rigorous stirring to produce 4 wt % of Pd/CeO2 catalyst. Na2CO3 solution was also added to adjust the pH of the solution to approximately 9.
The final solution was stirred for 2 hours, and then aged at room temperature for 2 hours without stirring. This solution was filtered, and dried in an oven at 353 K for 5 hours. The produced Pd/CeO2 catalyst was calcined at 750° C. in air for 25 hours.
2-1. Characterizations of Pd/CePdO and CePdO Support by CO-DRIFT
To remove Pd on the surface of existing Pd/CePdO catalyst, the catalyst was subjected to a leaching treatment by being immersed in nitric acid at 250° C. for 1 hour, thereby obtaining CePdO support. The presence or absence of Pd on the surface of the sample was observed through CO-DRIFT analysis, by which the surface of the sample could be confirmed.
Specifically, the in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS; Nicolet iS50, Thermo Scientific) measurement was carried out with an MCT detector and a diffuse reflectance assembly chamber having a KBr window. The sample was pretreated at 100° C. for 1 hour under Ar gas flow, and cooled to room temperature, and then a background spectrum was obtained. For CO adsorption, 1% CO/Ar gas flowed over the sample for 10 minutes to saturate CO.
The spectra were observed during CO desorption by Ar flow with evacuation for 20 minutes at room temperature. Finally, adsorbed-CO spectra onto the sample were obtained. The oxidation state of Pd was investigated by X-ray photoelectron spectroscopy (XPS, K-Alpha, Thermo VG Scientific). Binding energies were calculated using the maximum intensity of the advantageous C 1s signal at 284.8 eV as a reference.
As can be confirmed in
The CO adsorption peak was observed in the Pd/CePdO catalyst, and thus in the Pd/CePdO catalyst, the CO molecules were adsorbed on single or ensemble Pd sites, showing the presence of Pd nanoparticles on the surface. While no peak for CO adsorption was observed in CePdO and CeO2. The CO molecules hardly chemisorbed on the surface of CePdO and CeO2, indicating that Pd nanoparticles were removed from CePdO.
2-2. Characterizations of Pd/CePdO and CePdO Support by TEM & EDS Mapping
The Pd/CePdO catalyst and the CePdO support in section 2-1 above were analyzed by transmission electron microscope (TEM) (
High angle annular dark field-scanning TEM (HAADF-STEM) images and energy-dispersive X-ray spectroscopy (EDS) mapping images were obtained using a Titan cubed G2 60-300 (FEI) with an accelerating voltage of 200 kV (
As can be confirmed in
As can be confirmed in
2-3. Characterizations of Pd/CePdO and CePdO Support by XPS
The Pd/CePdO catalyst and the CePdO support in section 2-1 above were analyzed by X-ray photoelectron spectroscopy (XPS). The oxidation state of surface Pd could be confirmed through XPS analysis.
As can be confirmed in
Whereas, as can be confirmed in
2-4. Characterizations of Pd/CePdO and CePdO Support by XRD
The Pd/CePdO catalyst and the CePdO support in section 2-1 above were analyzed by powder X-ray diffractometer (XRD, RIGAKU) in order to investigate crystalline structures before and after the leaching treatment.
As can be confirmed in
2-5. Characterizations of Pd/CePdO and CePdO Support by BET
The Pd/CePdO catalyst and the CePdO support in section 2-1 above were measured for BET surface area in order to investigate surface area change before and after the leaching treatment. Both of the Pd/CePdO and CePdO samples were concurrently analyzed to obtain results.
As can be confirmed in Table 1, both of the two samples similarly showed a low specific surface area of about 8 m2/g. It could be therefore seen that the change by a leaching treatment did not greatly affect the surface area.
2-6. Characterizations of Pd/CePdO and CePdO Support by XANES and EXAFS
The Pd/CePdO catalyst and the CePdO support in section 2-1 above were analyzed by X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) in order to investigate oxidation states and structures thereof.
The oxidation state of Pd could be confirmed by XANES analysis. XANES and EXAFS spectrum measurements were carried out at the 10C wide XAFS beam line of the Pohang Light Source (PLS). The energy of the storage ring electron beam was 2.5 GeV with a ring current of up to 360 mA. The incident X-ray was monochromatized by Si(111)/Si(311) double-crystals. The Pd K-edge spectra were obtained in a fluorescence mode using a passivate implanted planar silicon (PIPS) detector (Canberra). The spectrum for a reference Pd foil was also measured concurrently to calibrate each sample.
As can be confirmed from
The structure of the sample can be confirmed by EXAFS analysis. The EXAFS and XANES data were processed and fitted with ARTEMIS and ATHENA softwares. A coordination number was calculated by fixing the S02 to the values obtained from the reference Pd foil. The actual Pd amount in the catalysts was measured with an inductively coupled plasma optical emission spectrometer (ICP-OES, Agilent). The Pd content in the Pd/CePdO catalyst was about 1 wt %.
As can be confirmed from
As can be seen from
3-1. Characteristic Comparison Between Pd/CePdO and Pd/CeO2
X-ray photoelectron spectroscopy (XPS) for Ce 3d and O 1s was performed on Pd/CePdO and Pd/CeO2. The change of oxygen vacancy sites were investigated through XPS analysis.
As can be confirmed from
Similarly, as can be confirmed from
3-2. Characteristic Comparison Between Pd/CePdO and Pd/CeO2 by BET
To observe the change in surface area of Pd/CePdO and Pd/CeO2, the BET surface area was measured.
As can be confirmed from Table 3, the surface Pd contents in Pd/CePdO and Pd/CeO2 were 0.5 wt % and 4 wt %, respectively, and the Pd dispersions thereof were 29.6% and 38.1%, respectively. The BET surface areas thereof were 7.8 and 32.4 m2/g, respectively.
aSurface Pd content in Pd/CePdO was 0.5 wt %, as measured by immersing in nitric acid at 250° C. The leaching solution with nitric acid was confirmed by ICP-OES analysis.
bPd dispersion was measured by pulsed CO chemisorption. Only surface Pd nanoparticles were considered. The CO-DRIFT results confirmed that CO was not adsorbed on CePdO and CeO2.
cChemSusChem 2020 13 677-681.
Pd/CePdO was analyzed by X-ray photoelectron spectroscopy (XPS). The oxidation state of surface Pd could be confirmed through XPS analysis.
As can be confirmed from
5-1. Investigation of Oxygen Transfer Ability of CeO2 and CePdO Supports and Pd/CeO2 and Pd/CePdO Catalysts
The oxygen transfer ability can be confirmed through O2-TPD analysis, and the higher the peak at low temperatures, the better the oxygen transfer ability.
Specifically, the O2-temperature programmed desorption (O2-TPD) spectra were performed on a BETCAT-B (BEL, Japan) equipped with high-sensitivity TCD. The signals from water flowing through a water trap were excluded. The O2-TPD spectra were obtained using 0.1 g of each catalyst. The catalysts were heated from room temperature to 900° C. with a ramping rate of 10° C. min−1 under He gas flow.
As can be confirmed from
In addition, when Pd/CePdO and Pd/CeO2 were compared, the low peak was shown in the Pd/CePdO sample, indicating that Pd/CePdO had high oxygen transfer ability.
Additionally, as can be confirmed from
The reactivity of Pd/CePdO catalyst was compared with that of Pd/CeO2 catalyst as a comparative example in actual methane reaction conditions.
Specifically, the reactivity of the catalysts was examined in a U-shaped quartz glass fixed-bed flow reactor at atmospheric pressure. The inlet gas was introduced with 6.8 scam of pure oxygen (99.995%, O2), 8.4 scam of pure nitrogen (99.999%, N2), and 90 sccm of pure methane (99.999% CH4). N2 gas was used as an internal standard. The amount of the catalyst used in the reaction was 10 mg. The reactor was heated at a ramping rate of 4° C. min−1 and the temperature thereof was maintained for 2 hours, thereby establishing normal state conditions.
Since Pd/CePdO catalyst has lower surface factor (up to 7.8 m2g−1) than Pd/CeO2 (see the results of Example 3-2), the C2H6 productivity per surface Pd atom was estimated to conduct a comparison of the turnover frequency for ethane (TOFC2H6).
The product gases (CO2, C2H6, and a very small amount of C2H4) was analyzed by a gas chromatograph (GC-6100 series, Younglin) with Molecular Sieve 5A and Porapak N columns (Sigma-Aldrich) equipped with thermal conductivity detector (TCD) and flame ionization detector (FID) as a methanizer.
The Pd dispersion was measured through pulsed CO chemical adsorption, by using the modified Takeguchi's method. First, 25 mg of the Pd/CeO2 catalyst was heated in the 5% O2/He gas at 300° C. for 10 minutes, and then cooled to 50° C. while purging with He gas for 5 min. Thereafter, the catalyst was heated in 4.9% H2/Ar gas to 200° C., and cooled to 50° C. Next, the catalyst was treated under following conditions; 1) He gas for 5 minutes, 2) 5% O2/He gas for 5 minutes, 3) CO2 gas for 10 minutes, 4) He gas for 20 minutes, 5) 4.9% H2/Ar gas for 5 minutes. Finally, CO gas was pulsed every 1 minute in the He stream repeatedly until the adsorption of CO onto the catalyst was saturated.
C2H6 selectivity (%) was calculated by the following equation.
As can be confirmed from
The ethane production rate (TOFC2H6) was calculated by the following equation.
As confirmed in
As can be confirmed from
The H2-temperature programmed reduction (H2-TPR) spectra were obtained using BEL-CAT-II (BEL Japan Inc.) equipped with a thermal conductivity detector (TCD). 50 mg of each catalyst was heated for 1 hour at 200° C. in an Ar gas flow and cooled down to −90° C. using a cryogenic apparatus using liquid nitrogen. Then, the catalysts were exposed to a 5% H2/Ar gas flow and stabilized under the flow for 30 minutes. The temperature increased from −90° C. to 900° C. at a ramping rate of 10° C. min−1.
As can be confirmed from
The Pd/CePdO can maintain the oxidic Pd state in a reductive condition, and the CePdO support allows the Pd domain to maintain the oxidized state.
Since the oxidized Pd site was the active site for C2H6 production, the Pd/CePdO catalyst showed excellent TOFC2H6.
The H2-TPR results indicate that the C2H6 productivity gradually decreased in Pd/CePdO when the temperature was 350° C. or higher (see
8-1. Catalyst Weight and Moisture Condition Affecting C2H6 Yield
For maximization of C2H6 yield, the reaction was performed by adjusting the weight of the catalyst to 5, 10, 25, 50, and 100 mg. The amounts of gases used in the reaction were the same as the amounts used in Example 6.
As can be confirmed in
The ethane production rate was calculated by the following equation.
Ethane production (scam; mL/min)
P: Pressure (atm)
R: Gas constant (atm·L/mol/K)
T: Temperature (K)
Mpd: Amount of catalyst used (g)
In addition, the weight of the catalyst and the thermal gradient (temperature difference) by the degradation of the catalyst were investigated through tests. The amounts of gases used in the reaction were the same as those used in Example 6, and the amounts of the catalyst used were 10, 25, and 50 mg.
As can be confirmed from
To investigate the effect of moisture on catalyst activity, the reaction was performed by adjusting the amount of moisture to 0, 0.9, and 3.6 vol % in conditions containing 100 mg of a catalyst and 10 g of silica sand.
As can be confirmed from
The ethane production rate was calculated by the following equation.
8-2. Addition of Zeolite 13X for Maximizing C2H6 Yield
The thermal gradient (temperature difference) due to an excess of catalyst is known to be overcome when silica sand is added to the catalyst. Zeolite 13X (ThermoFisher Scientific, Massachusetts, USA) was used as a substance which takes the place of silica sand helpful in the reaction of the catalyst and adsorbs moisture.
The reaction conditions were controlled to 100 mg of catalyst and 53 sccm of total feed flow (with 73% CH4 and 18% O2). The Pd/CePdO catalyst and zeolite 13X were mixed, followed by reaction, and the pretreatment was performed at 200° C., 300° C., and 400° C. before the reaction was performed.
As can be confirmed from
Consequently, the Pd/Ce1-xPdxO2-y catalyst can be used for the purpose of ethane direct conversion from methane by promoting oxygen activation or transfer. Furthermore, the production of ethane using Pd/Ce1-xPdxO2-y catalyst can be performed in conditions of lower than 400° C. and atmospheric pressure. Furthermore, the yield of ethane was increased when Pd/Ce1-xPdxO2-y catalyst was used together with a moisture adsorbent (zeolite 13X).
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2019-0121114 | Sep 2019 | KR | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/KR2020/007046 | 5/29/2020 | WO |
