Metal carbide nanomaterial catalysts and production method thereof

Abstract

A catalyst that includes heterogeneous metal carbide nanomaterials and a novel preparation method to synthesize the metal carbide nanomaterials under relatively mild conditions to form an encapsulated transition metal and/or transition metal carbide nanoclusters in a support and/or binder. The catalyst may include confined platinum carbide nanoclusters. The preparation may include the treatment of encapsulated platinum nanoclusters with ethane at elevated temperatures. The catalysts may be used for catalytic hydrocarbon conversions, which include but are not limited to, ethane aromatization, and for selective hydrogenation, with negligible green oil production.

Claims

1. A method for synthesizing a catalyst for catalytic hydrogenation of alkynes and alkadienes to olefins, which comprises steps of: step (1): mixing a support with an aqueous solution of a platinum precursor, to form a mixture; step (2): drying the mixture to form a dry product; step (3): calcinating the dry product obtained after the drying; step (4): reducing a dry product obtained after the calcination to form a catalyst precursor comprising multiple encapsulated platinum nanoclusters within the support; and step (5): activating the catalyst precursor obtained in step (4) in an ethane atmosphere to form the catalyst comprising a plurality of platinum carbide nanoclusters encapsulated in a plurality of micropores of the support; wherein in step (5), the catalyst obtained in step (4) is activated as follows: the catalyst precursor obtained in step (4) is purged with an inert gas, and an ethane activation occurs at temperatures between 300-750° C., for a certain period, cooled to 100° C. in ethane flow, and further cooled to room temperature in an inert atmosphere, wherein the support is an aluminosilicate zeolite and the catalyst comprises 300-25000 ppm of platinum.

2. The method according to claim 1, further comprising after reducing the dry product obtained after the calcination, a step of cooling the catalyst precursor obtained in step (4) in a hydrogen atmosphere.

3. The method according to claim 1, wherein the calcinating comprises an air calcination.

4. The method according to claim 3, wherein the calcinating occurs at a temperature between 300-800° C., for a certain period.

5. The method according to claim 1, wherein the catalyst contains between 300-500 ppm of platinum.

6. The method according to claim 1, wherein the dry product obtained after the calcination is reduced in hydrogen between 300-800° C. for a certain period.

7. The method according to claim 1, wherein an inert binder can be added before or after the calcinating step.

8. The method according to claim 1, wherein the encapsulated platinum nanoclusters have a size close to 1 nm.

9. The method according to claim 1, wherein the catalyst has a platinum dispersion greater than 90%.

10. The method according to claim 1, wherein the catalyst comprises the encapsulated platinum carbide nanoclusters having a size close to 1 nm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The accompanying drawings herein are used to provide further understanding of the invention and constitute a part of the description. The accompanying drawings together with the following embodiments serve to explain the invention, but do not constitute a limitation to the invention. In the accompanying drawings:

(2) FIG. 1 is a schematic representation of the process for forming the metal nanomaterial catalyst.

(3) FIG. 2 is a graph of a comparison of the dynamic CO chemisorption data of a prior art catalyst (Pt/Al.sub.2O.sub.3 after reduction) and a catalyst embodied by a first aspect of the invention after in-situ hydrogen reduction at 630° C. (Pt/ZSM-5 after reduction).

(4) FIG. 3 is graph of a comparison of the CO-DRIFT spectra of a prior art catalyst (Pt/Al.sub.2O.sub.3 after reduction), a catalyst embodied by the first aspect of the invention (Pt/ZSM-5 after reduction), a catalyst embodied by a second aspect of the invention (Pt/ZSM-5 after ethane activation); and a prior art catalyst after ethane activation (Pt/Al.sub.2O.sub.3 after ethane treatment).

(5) FIG. 4 is a graph illustrating the FTIR spectra of a catalyst embodied by the first aspect of the invention (Pt/ZSM-5 after reduction) and a catalyst embodied by the second aspect of the invention (Pt/ZSM-5 after ethane activation).

(6) FIG. 5 is a graph illustrating the in-situ XANES spectra of a catalyst embodied by the first aspect of the invention (Pt/ZSM-5 after reduction) and a catalyst embodied by the second aspect of the invention (Pt/ZSM-5 after ethane activation), as well as Pt foil as a reference.

(7) FIG. 6 is a graph illustrating the catalytic performance in terms of acetylene conversion over a prior art catalyst (Pt/Al.sub.2O.sub.3 after reduction), of a catalyst embodying the first aspect of the invention (Pt/ZSM-5 after reduction), and a catalyst embodying the second aspect of the invention (Pt/ZSM-5 after ethane activation), in the selective acetylene hydrogenation reaction.

(8) FIG. 7 is a graph showing the green oil selectivity over a prior art catalyst (Pt/Al.sub.2O.sub.3 after reduction), a catalyst embodying the first aspect of the invention (Pt/ZSM-5 after reduction), and a catalyst embodying the second aspect of the invention (Pt/ZSM-5 after ethane activation), in the selective acetylene hydrogenation reaction.

(9) FIG. 8 is a graph showing Temperature-Programmed Surface Reaction data of ethane over a catalyst embodying the first aspect of the invention (Pt/ZSM-5 after reduction), at a temperature range of 250-620° C.

(10) FIG. 9 is a graph showing Temperature-Programmed Surface Reaction data of ethane over a catalyst embodying the second aspect of the invention (Pt/ZSM-5 after ethane activation), at a temperature range of 250-620° C.

(11) FIG. 10 is a graph displaying the methane and BTX yields as a function of reaction temperatures over a catalyst embodying the first aspect of the invention (Pt/ZSM-5 after reduction), and a catalyst embodying the second aspect of the invention (Pt/ZSM-5 after ethane activation).

(12) In the various figures, similar elements are provided with similar reference numbers. It should be noted that the drawing figures are not necessarily drawn to scale, or proportion, but instead are drawn to provide a better understanding of the components thereof, and are not intended to be limiting in scope, but rather provide exemplary illustrations, and graphs are drawn to present the relevant data.

DETAILED DESCRIPTION OF THE INVENTION

(13) The embodiments of the invention will be described below in detail with reference to the accompanying drawings. It should be understood that embodiments described herein are only for illustration and explanation of the invention, but not for limitation to the invention.

(14) The present invention relates to a method for synthesizing supported catalysts, where the active phase is at the surface or within pores of the solid support, where the novel supported catalysts are capable of delivering selective hydrogenation performance with high olefin-gain selectivity and low selectivity to green oil (oligomers) and/or saturates, and to catalysts obtained from this method. In so doing, the present invention at least has the benefits of the increase in life expectancy of the catalysts and/or increased catalytic activity.

(15) As seen in FIG. 1, in one embodiment of the invention, a method is provided for synthesizing the novel heterogenous catalyst that comprises at least some of the following steps: Step 1 (S1): mixing a support and/or binder in a solution of metal precursor, preferably metal nitrate, to form a mixture; Step 2 (S2): drying the mixture to form a dry product; Step 3 (S3): calcinating the dry product; Step 4 (S4): reducing the dry product; Step 5 (S5): forming a catalyst comprising encapsulated metal nanoclusters within the support and/or binder; and Step 6 (S6): preferably, but not necessarily, activating the catalyst in an ethane atmosphere.

(16) Specifically, in the mixing step S1, the support and/or binder is selected from inorganic oxides, silicon carbide, silicon nitride, boron nitride, carbon, zeolites and combinations thereof, where preferably, the support is an aluminosilicate zeolite, which includes but is not limited to, ZSM-5, ZSM-11, ZSM-12, ZSM-23, ZSM-35, MOR, Ferrierite, Faujacite, Chabacite, beta zeolite (BEA), Y zeolite, X zeolite, SSZ-13, titanium silicalite-1 (TS-1), Amicite, Barrerite, Clinoptilolite, Harmotome, Laumontite, Paulingite, Pollucite, and mesoporous silica (e.g., MCM41), preferably ZSM-5, having a silica to alumina ratio of between 10:1 to 80:1, preferably between 20:1 to 45:1, and most preferably 30:1. The support and/or binder is mixed with an aqueous solution, which contains metal precursor, preferably platinum nitrate, which includes salts and complexes of platinum, where the mixture is mixed at moderate temperatures, e.g., 10-100° C., preferably 80° C., and ambient pressures, e.g., standard atmospheric pressure 101.3 kPA.

(17) The mixture is then dried at step S2 to obtain a dry product, where the dry product is then air calcinated at elevated temperatures at step S3, for example, between 300-800° C., and preferably at 550° C., for a certain period, preferably 0.5 to 24 hours, more preferably four hours. It is appreciated that during the air calcination step S3, inert binders such as silica powder and/or alumina powder can be added before or after the air calcination step to improve the catalyst strength. After air calcination, the product is in-situ reduced in hydrogen in step S4 at elevated temperatures, for example, 300-800° C., and preferably at 630° C., for a certain period, preferably 0.5 to 24 hours, more preferably one hour, and then cooled to room temperature, e.g., between 20-25° C. in a hydrogen atmosphere, to provide the synthesized catalyst in step S5.

(18) Optionally, after the in-situ reduction, at step S6, the product is cooled down to 100-650° C., preferably to 300-500° C., more preferably to 400° C., in the hydrogen atmosphere, which is followed by purging with an inert gas, e.g., nitrogen, at a temperature between 300-500° C., preferably 400° C., and activation in an atmosphere comprising at least one carbon-containing molecule, e.g., CO.sub.x, CS.sub.x, C.sub.xH.sub.y, C.sub.xH.sub.yCl.sub.z, C.sub.xH.sub.yF.sub.z, C.sub.xH.sub.yBr.sub.z, C.sub.xH.sub.yI.sub.z, C.sub.xH.sub.yO.sub.z, and preferably ethane, and nitrogen (e.g., 50% balanced in nitrogen) at a temperature between 100-750° C., and preferably between 300-750° C., more preferably at 400° C., for a certain period of time. After the activation, the catalyst is cooled down to between 80-150° C., preferably to 100° C., using the carbon-containing molecule atmosphere, and then further cooled down to room temperature in an inert atmosphere, e.g., in nitrogen.

(19) The resulting hydrogenation catalyst is a heterogeneous catalyst that includes the metal nanoclusters on the support and/or binder, and more preferably platinum or platinum carbide nanoclusters on an aluminosilicate zeolite, where the metal or metal carbide nanoclusters are confined or encapsulated in micropores of the zeolite. For example, the metal or metal carbide nanoclusters have sizes close to 1 nm, e.g., +/−10%, to be encapsulated in the zeolite. In one embodiment of the invention, the catalyst contains between 300-25000 ppm of platinum, and most preferably 500 ppm of platinum, where the platinum has a metal dispersion greater than 90% and preferably between 95-100%.

(20) The inventive method and catalyst will be further illustrated with respect to specific Examples that are only intended to demonstrate the invention, but not limit it in any way.

Comparative Example 1

(21) 5 grams of Al.sub.2O.sub.3 powder was mixed with an amount of a Pt(NO.sub.3).sub.2 containing solution. The mixture was stirred at room temperature for 1 hour and then heated to 80° C. for 1 hour in a rotary evaporator to obtain a dry product, followed by air calcination at 550° C. for 4 hours. The powder was then in-situ reduced in hydrogen at 630° C. for 1 hour, and cooled down to room temperature in a hydrogen atmosphere. The powder was then pressed and sized to 20×40 mesh. The obtained product is denoted as Catalyst A, which contains 500 ppm Pt. Catalyst A was then subjected to characterization measurements to determine its features.

Example 1

(22) 5 g of ZSM-5 powder (having a silica to alumina ratio of 30) was mixed with a certain amount of Pt(NO.sub.3).sub.2 in solution. The mixture was agitated at room temperature for 1 hour and then heated to 80° C. in a rotary evaporator to obtain a dry product, which was followed by air calcination at 550° C. for 4 hours. The powder was then in-situ reduced in hydrogen at 630° C. for 1 hour, and cooled down to room temperature (e.g., between 20-25° C.) in a hydrogen atmosphere. The powder was then pressed and sized to 20×40 mesh. The obtained product is denoted as catalyst B, which contains 500 ppm Pt. Catalyst B was then subjected to characterization measurements to determine its features.

Example 2

(23) A powder was prepared using the same procedure for Catalyst B from Example 1, but after the reduction in the hydrogen atmosphere, the powder was cooled to 400° C. in a hydrogen atmosphere, followed by a an inert gas purge at 400° C. for 10 minutes and then activated in ethane (50% balance in nitrogen) at a temperature between 300-500° C. After the ethane activation, the powder was cooled down to 100° C. under ethane flow, and further cooled to room temperature in an inert gas atmosphere, e.g., in nitrogen. The obtained product is denoted as catalyst C, which also contains 500 ppm platinum.

(24) Catalysts A, B, and C were then characterized by testing and analyzing the catalysts for the platinum dispersion in the catalyst by dynamic CO chemisorption measurements (chemical adsorption), where the evolution of the platinum species was also studied by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and X-ray absorption near edge structure (XANES). As will be discussed below, the characterization data show for catalyst B, after reduction, the platinum forms encapsulated Pt small nanoclusters. Additionally, after ethane activation (catalyst C), these Pt nanoclusters are transformed to novel encapsulated Pt carbide nanoclusters, PtC.sub.x/ZSM-5. The data also shows that adding inert binder does not affect such transformation, in other words does not affect the formation of Pt nanoclusters to Pt carbide nanoclusters.

(25) FIG. 2 shows the dynamic CO chemisorption data of catalyst A (curve 200) after in-situ hydrogen reduction at 630° C. and catalyst B (curve 220) after in-situ hydrogen reduction at 630° C. The Pt dispersion and average particle size determined from the dynamic CO chemisorption are listed in Table 2. FIG. 2 and Table 2 show that for catalyst A, Pt/Al.sub.2O.sub.3, after hydrogen reduction, Pt dispersion is approximately 21%, and Pt mainly forms nanoparticles with the average particle size at 6 nm. On the other hand, for catalyst B after reduction, the data shows that the Pt dispersion is at ˜100%, and the platinum forms small nanoclusters with the cluster size close to 1 nm. Moreover, the data shows that catalyst B has much larger peak widths which indicates that these nanoclusters are located within micropores of the zeolite. In other words, the data shows that after reduction, catalyst B includes encapsulated platinum nanoclusters in the zeolite support.

(26) FIG. 3 shows the CO-DRIFT spectra of catalyst A after reduction (Pt/Al.sub.2O.sub.3 after reduction) (curve 300), catalyst B after reduction (Pt/ZSM-5 after reduction) (curve 320), and catalyst C (Pt/ZSM-5 after ethane activation) (curve 340), as well as an example of catalyst A after the ethane treatment (“modified catalyst A”) (curve 360). In the case of catalyst A and catalyst B, the sample was first reduced with hydrogen at 630° C., and then cooled down to room temperature in a helium atmosphere, followed by the CO-DRIFTS measurements at room temperature. In the case of catalyst C and modified catalyst A, after the same treatment, the catalysts were cooled down to 100° C. in ethane, followed by further cooling down to room temperature in helium. CO-DRIFTS measurements at room temperature were performed after an additional helium purge for 30 min.

(27) The CO-DRIFTS measurements in FIG. 3 shows that for catalyst A after reduction, Pt forms metallic nanoparticles, which is consistent with the dynamic CO chemisorption measurements in FIG. 2. However, for catalyst B after reduction, CO-DRIFTS and dynamic CO chemisorption data show that the majority of the platinum forms Pt small nanoclusters encapsulated within micropores of zeolite. Furthermore, CO-DRIFT spectra also show that after ethane activation, the peak related to Pt nanoclusters completely disappears, while a new double peak feature in the range from 2250 cm.sup.−1 to 2150 cm.sup.−1 appears. Similar double peak feature has been reported in CO-DRIFTS study of molybdenum carbide materials (ACS Applied Materials & Interfaces, 9 (2017) 9815-9822). Thus, it is understood that in combination with other characterizations listed below, this double peak feature may be related to the presence of platinum carbide nanoclusters. Therefore, it can be concluded that the encapsulated Pt nanoclusters presented in Pt/ZSM-5 after reduction were transformed to encapsulated Pt carbide nanoclusters in catalyst C, Pt/ZSM-5 after ethane activation. On the other hand, FIG. 3 also shows that for catalyst A after similar ethane treatment, there is no presence of such double peak feature as catalyst C indicating that large Pt metallic nanoparticles cannot be transformed to Pt carbide species upon ethane treatment.

(28) FIG. 4 shows the FTIR spectra of catalyst B after reduction, (Pt/ZSM-5 after reduction) (curve 420) and catalyst C (Pt/ZSM-5 after ethane activation) (curve 440). In the case of catalyst B, after reduction, the sample was cooled down to room temperature in helium, followed by the FTIR measurements at room temperature. In the case of catalyst C, after ethane activation, the sample was first cooled down to 100° C. in ethane, and then was further cooled down to room temperature in helium, followed by helium purge at room temperature for 30 min, prior to FTIR measurements.

(29) As seen in FIG. 4, the FTIR spectra in the Pt—C stretching range for catalyst B shows clearly, after reduction, there is no peak associated with Pt—C bonds. However, after ethane activation, there are several peaks associated with the Pt—C bonds for catalyst C, as reported in the literature (Chemical Physics Letters, 560 (2013) 42-48). Thus the in-situ FTIR data shows that upon ethane activation, there are Pt carbide species in catalyst C.

(30) FIG. 5 shows the in-situ XANES spectra of catalysts B after reduction, (Pt/ZSM-5 after reduction) (curve 520) and catalyst C (Pt/ZSM-5 after ethane activation) (curve 540), as well as a Pt foil as a reference (curve 580). In the case of catalyst B, after reduction, the sample was cooled down to room temperature in helium, followed by XANES measurements at room temperature. In the case of catalyst C, after ethane activation, the sample was first cooled down to 100° C. in ethane, and then was further cooled down to room temperature in He, followed by He purge at room temperature for 30 min, prior to XANES measurements.

(31) The XANES data in FIG. 5 further supports that encapsulated Pt carbide nanoclusters are formed after ethane activation. For example, after reduction, the XANES spectrum of catalyst B is different than the Pt metallic foil, where a high intensity white line is present in the case of Pt/ZSM-5 after reduction. Similarly, such XANES spectra with a high intensity white line has been observed in a published study of canonic Pt small nanoclusters encapsulated within micropores of MCM-22 (Nature Materials, 16 (2017) 132-138). Thus, the XANES spectra also suggests that after reduction, Pt forms small nanoclusters in catalyst B. Moreover, after ethane activation, a new pre-edge peak between 11530-11560 eV appears in the XANES spectrum of catalyst C. A similar pre-edge peak of Pt has been reported in a published study of atomically dispersed Pt embedded in carbon matrix, and was attributed to the electronic effect on Pt caused by the presence of Pt—C bonds of confined Pt species (Science Advance, 4 (2018) eaao6657). It is very likely that the appearance of the pre-edge peak in catalyst C is also due to the electronic effect on Pt caused by the formation of Pt—C bonds. Thus, the XANES data also supports the conclusion on the transformation of Pt nanoclusters to Pt carbide nanoclusters upon ethane activation.

(32) That is, the characterizations of these catalytic materials are shown in FIG. 2 to FIG. 5 and Table 2 (below).

(33) TABLE-US-00002 TABLE 2 Sample Pt dispersion Particle size Catalyst B, 0.05 wt % Pt/ZSM-5 100% ~1 nm Catalyst A, 0.05 wt % Pt/Al.sub.2O.sub.3  21%   6 nm

(34) Such novel catalysts were found to be capable of delivering improved selective hydrogenation performance with high olefin-gain selectively and low selectivity to green oil and/or saturates during a hydrogen conversion process as known in the art. For example, hydrogen conversion processes as disclosed in U.S. Pat. Nos. 7,153,807 and 8,946,107 and U.S. publication 2018/0194701, which are incorporated herein by reference. In so doing, the benefits of the novel catalysts B and C include, but are not limited to, the extension of the lifetime performance of the catalyst and/or the extension of the operation cycle of the hydrogenation due to the reduction of green oil production.

(35) In one embodiment of the invention, the ethane aromatization is performed at temperatures between 300-750° C., preferably between 500-650° C., more preferably between 600-630° C. and/or at gas hourly space velocity (GHSV) of ethane between 500-5000 hr.sup.−1, preferably at GHSV of ethane at 1000 hr.sup.−1. Additionally, the selective hydrogenating of acetylene to ethylene is performed at temperatures between 20-200° C., preferably between 20-90° C. and/or at GHSV of acetylene between 10-1000 hr.sup.−1, and a H.sub.2/C.sub.2H.sub.2 ratio between 0.5 to 20, preferably between 2-6.

(36) The benefits of such novel catalysts B and C are discussed further below with respect to the catalytic performance of catalysts A, B, and C in hydrocarbon conversions as illustrated in the selective acetylene hydrogenation reaction, and ethane aromatization reactions, e.g., catalytic hydrogenation of alkynes and alkadienes to olefins and catalytic conversion of ethane to aromatics. Applicant notes that while discussion is made of the catalytic hydrocarbon conversion process to the selective hydrogenating of acetylene to ethylene, such conversion process is not limited to said selective hydrogenating of acetylene to ethylene, but can also include selective hydrogenation of 1,3-butadiene (C.sub.4H.sub.6) to butene (C.sub.4H.sub.8). The Pt dispersion in these catalysts were examined by dynamic CO chemisorption measurements. The active phase of these catalysts was studied by CO-DRIFTS, and XANES.

(37) FIG. 6 shows the catalytic performance in terms of acetylene conversion of catalyst A, (Pt/Al.sub.2O.sub.3 after reduction) (curve 700), catalyst B, (Pt/ZSM-5 after reduction) (curve 720), and catalyst C, (Pt/ZSM-5 after activation) (curve 740), in the selective acetylene hydrogenation reaction. As seen in FIG. 6, catalysts B and C are much more active than catalyst A. For example, at 70° C. with the same platinum loading, the acetylene conversion over catalyst C is ˜13%, while the conversion over catalyst B is less than 3%. At the same reaction conditions, the acetylene conversion over catalyst A is negligible. On the other hand, the ethylene selectivities of catalysts A, B, and C are similar, at approximately 65%, at the measured temperature range. In these measurements, the same amount of catalyst, 500 mg was used, and the total gas flow was 76 mL/min, with 2 mL/min acetylene, 6 mL/min hydrogen, 2 mL/min nitrogen, and 66 mL/min helium.

(38) FIG. 7 shows the green oil selectivity of catalyst A, (Pt/Al.sub.2O.sub.3 after reduction) (curve 800), catalyst B, (Pt/ZSM-5 after reduction) (curve 820), and catalyst C, (Pt/ZSM-5 after activation) (curve 840) in the selective acetylene hydrogenation reaction. Clearly, the green oil productivities of catalyst B and catalyst C are much lower than catalyst A. More significantly, the green oil productivity of catalyst C is zero or almost zero. As the presence of green oil products can significantly poison the hydrogenation catalysts, and decrease the lifetime of the catalysts, the reduction of the green oil productivity to a near zero or zero level is a great benefit of catalyst C.

(39) Based on the catalytic results shown in FIG. 6 and FIG. 7, it can be concluded that catalyst B (Pt/ZSM-5 after reduction) is much more active than catalyst A (Pt/Al.sub.2O.sub.3 after reduction) for the selective hydrogenation of acetylene to ethylene, with similar ethylene selectivity and reduced green oil productivity. However, catalyst C (PtC.sub.x/ZSM-5) shows even more improved catalytic activity towards acetylene hydrogenation, with similar ethylene activity and negligible green oil productivity. Overall, catalyst C having the features of this invention exhibits significantly improved catalytic performance in the selective acetylene hydrogenation reaction, in terms of activity and selectivity, compared to catalyst A (standard Pt/Al.sub.2O.sub.3 catalyst), e.g., the encapsulated platinum carbide nanoclusters are active and selective towards the selective hydrogenation of acetylene to ethylene.

(40) FIG. 8 shows Temperature-Programmed Surface Reaction data of ethane over catalyst B (Pt/ZSM-5 after reduction), at the temperature range of 250-620° C. (curve 900). The product concentrations (based on carbon) of ethane (curve 910), methane (curve 920), and BTX (curve 930) are monitored by a mass spectrometer (MS), and plotted on the Y axis.

(41) FIG. 9 shows Temperature-Programmed Surface Reaction data of ethane over catalyst C (Pt/ZSM-5 after activation), at the temperature range of 250−620° C. (curve 1000). The product concentrations (based on carbon) of ethane (curve 1010), methane (curve 1020), and BTX (curve 1030) are monitored by a mass spectrometer (MS), and plotted on the Y axis.

(42) FIG. 10 displays the methane and BTX yields as a function of reaction temperatures for catalyst B (curves 1120, 1125, respectively) and the methane and BTX yields as a function of reaction temperatures for catalyst C (curves 1140, 1145, respectively). The figure is plotted based on the data obtained from FIGS. 8 and 9.

(43) FIGS. 8, 9, and 10 show that catalyst C (PtC.sub.x/ZSM-5) is highly active for ethane aromatization. For catalyst B (Pt/ZSM-5), the data shows that the light-off temperature is approximately at 400° C., at which Pt carbide species start to form. As the characterization data shows, during ethane aromatization, Pt species are present as Pt carbide nanoclusters, thus an initial introduction period is needed to activate catalyst B. Whereas, for catalyst C, no introduction period is needed. Therefore, for catalyst C, the light-off temperature is approximately at 300° C., which is much lower than catalyst B. In addition, the initial BTX selectivity is much higher for catalyst C than the BTX selectivity for catalyst B. Such observations in combination with characterization data clearly show that in-situ formed confined Pt carbide nanoclusters are the active phase for Pt/ZSM-5 based catalyst in ethane aromatization, e.g., the encapsulated platinum carbide nanoclusters are active and selective towards ethane aromatization.

(44) The measurements also show that mixing the inert binder with Pt/ZSM-5 does not change the catalyst activity and selectivity in the case of catalyst B and catalyst C, for both acetylene hydrogenation and ethane aromatization reactions. Thus, the inert binder does not participate the catalytic reactions of hydrocarbon conversions

(45) In conclusion, the data shows that catalyst C (Pt/ZSM-5 after ethane activation) forms novel encapsulated Pt carbide nanoclusters, which has several benefits over the previous hydrogenation catalysts. For example, while not limiting the invention, the benefits include: 1. Metal carbide material can be synthesized at ambient pressure. 2. Metal carbide material can be synthesized at temperatures between 300-650° C. 3. Pt carbide material can be synthesized by using commercially available zeolite supports and Pt precursors, preferably Pt nitrate, without using expensive diamond support and laser heating. 4. Metal carbide can be formed as nanoclusters in the support.

(46) Accordingly, the above embodiments of the invention provided involve at least the following three approaches:

(47) 1. Preparation of catalysts with impregnation of zeolite with a metal solution, followed by calcination, reduction, and ethane activation.

(48) 2. Illustration of the high catalytic performance of prepared catalysts in catalytic hydrocarbon conversion reactions.

(49) 3. Identification of the active phase of the prepared catalysts through various in-situ characterizations.

(50) The above description is merely the various embodiments of the present invention, where the scope of the invention is not limited thereto, and changes or substitutions within the technical scope of the invention can be easily made by those persons skilled in the art and should be considered to be within scope of the present invention. Therefore, the scope of protection of the present invention is only subject to the scope of protection of the appended claims