Oxidative dehydrogenation of ethane over boron-containing chabazite

Abstract

Disclosed herein are processes of oxidative dehydrogenation of ethane to ethylene that involve the use of boron-containing chabazite. Systems for performing the processes are also disclosed.

Description

[0001] OXIDATIVE DEHYDROGENATION OF ETHANE OVER BORON-CONTAINING CHABAZITE

[0002] CROSS-REFERENCE TO RELATED APPLICATION

[0003] This application claims priority to United States Provisional Application No. 63 / 522,503, filed June 22, 2023, and the contents of which are incorporated herein by reference in their entireties for all purposes.

[0004] FIELD

[0005] The present disclosure relates to processes of oxidative dehydrogenation of ethane to ethylene that involve the use of boron-containing chabazite. Systems for performing the process are also disclosed.

[0006] GOVERNMENT SUPPORT

[0007] The present disclosure was supported, in whole or in part, by National Science Foundation Grant No. 1908982 and 2134471. The United States government has certain rights to the subject matter disclosed herein. BACKGROUND

[0008] Ethylene is the largest organic intermediate in the chemical industry with a global production capacity of 214 million metric tons in 2021. Ethylene production is also the second largest source of greenhouse gas emissions in the chemical industry, producing over 1 ton of CC -equivalent emissions per ton of ethylene. This stems from the fact that ethylene production uses non-oxidative and non- catalytic processes, such as ethane steam cracking, which require a high reaction temperature (>1073 K) to overcome the thermodynamic limitations of this highly endothermic reaction. The expanding global demand for ethylene further drives interest in developing novel catalytic routes to ethylene production, and the oxidative dehydrogenation of ethane (ODHE) is an attractive alternative due to its low energy demand and the in-situ carbon-deposits removal by the oxygen present in the feed. Unfortunately, the poor selectivity caused by the overoxidation of reactants and products into carbon oxides is a barrier that has yet to be overcome.

[0009] Both reducible and non-reducible metal oxides have been widely investigated for ODHE. Morales and Lunsford reported that Li+ / MgO catalysts achieve 75 % ethylene selectivity at 40 % ethane conversion at 600 °C in 1989 (Morales, E.; Lunsford, A. H., "Oxidative Dehydrogenation of Ethane over a Lithium-Promoted Magnesium Oxide Catalyst", J. Catal., 989', Vol. 118, pp 255- 281 ). ODHE over vanadium and nickel oxides is also promising (Najari, S.; Saeidi, S.; Concepcion, P.; Dionysiou, D. D.; Bhargava, S. K.; Lee, A. F.; Wilson, K., "Oxidative Dehydrogenation of Ethane: Catalytic and Mechanistic Aspects and Future Trends", Chem. Soc. Rev., 2021 , 50 (7), 4564-4605.). Linde and Clariant have developed ODHE processes with M1 catalysts, resulting in a combined selectivity (ethylene and acetic acid) of 93 % (A.M. Gaffney, Catal. Today 285 (2017) 159-165; D. Melzer, P. Xu, D. Hartmann, Y. Zhu, N.D. Browning, M. Sanchez-Sanchez, J. A. Lercher, Angew. Chem. Int. Ed. 55 (2016) 8873-8877; U.S. Patent 8,519,210). This process has been demonstrated at a commercial scale. Boron-containing heterogeneous catalysts, such as hexagonal boron nitride ( / 7-BN), metal borides, and supported boron oxides, also catalyze the oxidative dehydrogenation of propane (ODHP) with high propene selectivity. Grant et al. first reported ODHP over / 7-BN with 79 % propene selectivity at 14 % propane conversion (J.T. Grant, C.A. Carrero, F. Goeltl, J. Venegas, P. Mueller, S.P. Burt, S.E. Specht, W.P. McDermott, A. Chieregato, I. Hermans, Science 354 (2016) 1570-1573). Zhou et al. presented a boron MFI zeolite with a combined selectivity (propene and ethylene) of 81 % at 41 % propane conversion (H. Zhou, X. Yi, Y. Hui, L. Wang, W. Chen, Y. Qin, M. Wang, J. Ma, X. Chu, Y. Wang, X. Hong, Z. Chen, X. Meng, H. Wang, Q. Zhu, L. Song, A. Zheng, F.S. Xiao, Science 372 (2021 ) 76-80). For ODHE over / 7-BN, 79 % and 68 % ethylene selectivity at 36 % and 44 % ethane conversions were achieved over activated / 7-BN at 575°C and 590°C, along with 80 % ethylene selectivity at 20 % ethane conversion over commercial / ?-BN at 600°C. Moreover, supported boron oxides showed 17% ethylene yield at 19% ethane conversion over 30 % B2O3-AI2O3.

[0010] The / 7-BN catalyst catalyzes ODHP through an Eley-Rideal mechanism that combines surface and gas-phase reaction networks including surface initiation and free-radical gas-phase propagation. These reaction kinetics have Langmuir adsorption dependence on the oxygen partial pressure (P02) and second-order dependence on the propane partial pressure (PCSHS), a universal feature of the / ?-BN catalyst. The second-order dependence on PCSHS suggests that propane reacts directly from the gas phase with active oxygen species, in agreement with a mixed surface-gas mechanism.

[0011] The borosilicate catalyst with MFI zeolite framework also shows Langmuir adsorption dependence on po2 but first-order dependence on pc3H8 in ODHP. To explain this difference in catalytic kinetics, Zhou et al. proposed a propane-oxygen co-activation mechanism in which the reaction pathways occur at the surface without gas-phase involvement. Tian et al. investigated the influence of spatial confinement on the kinetics of boron oxide supported on mesoporous silicas with different pore diameters, revealing that the propane reaction order could vary from 1 to 3 depending on the pore size of the support, B2O3 loading, and pc3H8 (H. Tian, Y. Liu, B. Xu, Catal. Today (2023) 114048).

[0012] Grant et al. first proposed that an oxygen-terminated armchair edge of BN (>B-O-O-N<) works as the active site for the ODHP reaction. Venegas et al. further suggested that BO* species formed by the cleavage of >B-O-O-B< can react with oxygen to form the free radical HOO* over h-B N , leading to the mixed surface and gas-phase propane H abstraction (J.M. Venegas, Z. Zhang, T.O. Agbi, W.P. McDermott, A. Alexandrova, I. Hermans, Angew. Chem. Int. Ed. 59 (2020) 16527- 16535). Tian et al. proposed that the reaction between boron and oxygen forms the boron peroxyl radical (BOO*), which initiates gas-phase propagation in fi-BN- catalyzed ODHP (H. Tian, B. Xu, Chin. J. Catal. 43 (2022) 2173-2182). On the other hand, Zhou et al. reported a novel isolated active site of -B[OH...O(H)-Si]2 in the MFI zeolite framework, showing exceptional olefin selectivity in ODHP without gas-phase chemistry, which is very different from fi-BN mechanism.

[0013] Chabazite-type (CHA) catalysts are used commercially in the methanol-to- olefins process and the selective catalytic reduction of NOx with ammonia. For example, CHA zeolite is a CHA catalyst that is formed by cages accessed only through 8-ring windows of ~3.9 A in diameter. These windows are sufficiently large for the facile diffusion of ethane, ethylene, and smaller molecules; however, propane diffusion into CHA zeolite is considerably slower than ethane by a factor of over 104, with a Dc2 / Dc3 ~ 3.7 x 106and 5.6 x 104at 30 °C and 80 °C respectively. There are six 8-ring windows per cage and the cage is formed by 36 T-atoms (T— TO4 / 2, where T is Si or B) and is ~7.4 A in diameter. CHA zeolite is structurally simple because the crystallographic asymmetric unit contains only one SiO4 / 2 tetrahedron while MFI has twelve, simplifying the interpretation of CHA zeolite spectroscopic results. CHA zeolite also has a large microporous volume (-0.30 cm3g-1), a high surface area (-500 m2g-1), and abundant internal Si-OH group. Heats of adsorption of ethane and ethylene in siliceous CHA are low and have been found to be dominated by van der Waals forces (28.9 kJ mol-1and 27.2 kJ mol-1respectively).

[0014] Though many catalysts have been investigated for ODHE, the problem of overoxidation of ODHE reactants and products, along with high greenhouse gas emissions, is still a prevalent problem. Thus, to address this problem, the present disclosure provides novel boron-containing chabazite catalysts that can be used in ODHE processes to reduce the amount of greenhouse gas production and overoxidation.

[0015] SUMMARY

[0016] Disclosed herein is a process of oxidative dehydrogenation of ethane to ethylene, the process including ( / .e., comprising) contacting an input feed gas including ethane with an oxidative dehydrogenation catalyst including a boron- containing zeolite in the presence of an oxygen, wherein the contacting occurs at a reaction temperature in the range of 450 to 650°C and at a pressure in the range of 0.5 to 20 atm, for a suitable amount of residence time to oxidatively dehydrogenate at least a portion of the ethane to produce a product stream including ethylene, wherein the boron-containing zeolite contains pores bounded by eight tetrahedral Si and / or B atoms.

[0017] Also disclosed herein is a system for producing ethylene by oxidative dehydrogenation of ethane, the system including one or more of: (i) a reactor including (a) one or more inlets configured to receive one or more input feed gases; (b) an oxidative dehydrogenation catalyst including a boron-containing zeolite configured to communicate with one or more input feed gases, wherein the boron- containing zeolite contains pores bounded by eight tetrahedral Si and / or B atoms; and (c) an outlet configured to release a product stream from the reactor, wherein the product stream includes ethylene and residual ethane; (ii) a temperature controller unit configured to control the temperature inside the reactor in a temperature range of 450-650 °C; (iii) a flow controller configured to control a flow rate and a residence time of one or more input feed gases and at least one product stream; (iv) a pressure controller unit configured to control a pressure inside the reactor in a range of 0.5-20 atm; and an optional separations unit configured to receive a first product stream and separate ethylene from the first product stream.

[0018] BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Other features and advantages of the compositions, devices and methods disclosed herein will be apparent to those skilled in the art reading the following detailed description in conjugation with the exemplary embodiments illustrated in the drawings, wherein:

[0020] FIG. 1 depicts an XRD pattern of an exemplary fresh hexagonal boron nitride catalyst.

[0021] FIG. 2 depicts an SEM image of an exemplary fresh hexagonal boron nitride catalyst.

[0022] FIG. 3 depicts an N2 sorption isotherm of an exemplary fresh hexagonal boron nitride catalyst.

[0023] FIG. 4 depicts the XRD patterns of exemplary fresh and spent boron chabazite catalysts.

[0024] FIG. 5 depicts SEM images of exemplary boron chabazite catalysts and the particle size distribution of an exemplary fresh boron chabazite catalyst. (A) depicts the SEM images of the exemplary fresh boron chabazite catalyst. (B) depicts the SEM images of an exemplary spent boron chabazite catalyst after 20 hours into an ODHE reaction. (C) depicts the SEM images of an exemplary spent boron chabazite catalyst after 60 hours into an ODHE reaction. (D) depicts the particle size distribution of the exemplary fresh boron chabazite catalyst.

[0025] FIG. 6 depicts the N2 sorption isotherms of an exemplary fresh boron chabazite catalyst and exemplary spent boron chabazite catalysts.

[0026] FIG. 7 depicts the XPS, B XPS and Si XPS spectra of an exemplary fresh boron chabazite catalyst. (A) XPS, (B) B XPS, and (C) Si XPS.

[0027] FIG. 8 depicts the XPS, B XPS and Si XPS spectra of an exemplary spent boron chabazite catalyst after 20 hours into an ODHE reaction. (D) XPS, (E) B XPS, and (F) Si XPS. FIG. 9 depicts the XPS, B XPS and Si XPS spectra of an exemplary spent boron chabazite catalyst after 60 hours into an ODHE reaction. (G) XPS, (H) B XPS, and (I) Si XPS.

[0028] FIG. 10 depicts the ethylene selectivities plotted against ethane conversions over exemplary hexagonal boron nitride (h-BN) and boron chabazite (B-CHA) catalysts. The stars represent reported data of known ODHE catalysts used in the art. ODHE reaction conditions: catalyst 125-750 mg, 500-600°C, gas feed 15 mimin'1, 20 vol% C2H6, 12 vol% O2, He balance, 0.1 MPa.

[0029] FIG. 11 depicts a comparison of the product selectivity between exemplary h-BN and B-CHA catalysts. ODHE reaction conditions: catalyst 250 mg, 600°C, gas feed 15 mL min-1, 20 vol% C2H6, 12 vol% O2, He balance, 0.1 MPa.

[0030] FIG. 12 depicts the ethane conversion and ethylene selectivity of an exemplary B-CHA catalyst plotted against various ODHE reaction temperatures. ODHE reaction conditions: catalyst 750 mg, 500-600°C, gas feed 15 mL min'1, 20 vol% C2H6, 12 vol% O2, He balance, 0.1 MPa.

[0031] FIG. 13 depicts the ethane conversion, oxygen conversion and product selectivities of an exemplary B-CHA catalyst plotted against various ODHE reaction temperatures. ODHE reaction conditions: catalyst 750 mg, 500-600°C, gas feed 15 mL min'1, 20 vol% C2H6, 12 vol% O2, He balance, 0.1 MPa.

[0032] FIG. 14 depicts the ethane conversion and ethylene selectivity of an exemplary B-CHA catalyst plotted against various ODHE reaction time points. ODHE reaction conditions: catalyst 750 mg, 580 °C, gas feed 15 mL min-1, 20 vol% C2H6, 12 vol% O2, He balance, 0.1 MPa.

[0033] FIG. 15 depicts the ethane conversion, oxygen conversion and product selectivities of an exemplary B-CHA catalyst plotted against various ODHE reaction time points. ODHE reaction conditions: catalyst 750 mg, 580 °C, gas feed 15 mL min'1, 20 vol% C2H6, 12 vol% O2, He balance, 0.1 MPa.

[0034] FIG. 16 depicts the ODHE ethane consumption rates for an exemplary B- CHA catalyst at different catalyst masses.

[0035] FIG. 17 depicts the apparent activation energy (Eapp) of an ODHE reaction over an exemplary B-CHA catalyst. The short-dashed line represents the linear fitting result. FIG. 18 depicts the dependence of -rc2H6 on po2 (reaction rate and partial oxygen pressure) over an exemplary B-CHA catalyst (A), the dependence of -rc2H6 on pc2H6 over the exemplary B-CHA catalyst (B), and the reaction orders of C2H6 of ODHE over the exemplary B-CHA catalyst (C) over various ODHE reaction temperatures. The short-dashed lines represent the simulated Langmuir adsorption isotherms in (A). The short-dashed lines represent the linear fitting results in (C). The dependences of -rc2H6 on pc2H6 and P02 were determined by changing ethane (1-3.6 mL min-1) and oxygen flow rate (0-3 mL min-1) (total flow rate = 15 mL min-1).

[0036] FIG. 19 depicts the dependence of -rc2H6 on pc2H60ver an exemplary h-BN catalyst at various ODHE reaction temperatures.

[0037] FIG. 20 depicts the 1 D29Si MAS NMR spectra of an exemplary as-made B- CHA catalyst.

[0038] FIG. 21 depicts the thermogravimetric analysis of an exemplary as-made B- CHA catalyst.

[0039] FIG. 22 depicts the 1 D29Si MAS NMR spectra of an exemplary fresh B-CHA catalyst.

[0040] FIG. 23 depicts the 1 D11B MAS NMR spectra of (A) an exemplary as-made B-CHA catalyst, (B) an exemplary fresh B-CHA catalyst, (C) an exemplary spent B- CHA catalyst that has reacted for 20 hours in an ODHE reaction, and (D) an exemplary spent B-CHA that has reacted for 60 hours in an ODHE reaction.

[0041] FIG. 24 depicts the 2D11B MQMAS NMR spectra of (A) an exemplary as- made B-CHA catalyst, (B) an exemplary fresh B-CHA catalyst, (C) an exemplary spent B-CHA catalyst that has reacted for 20 hours in an ODHE reaction, and (D) an exemplary spent B-CHA that has reacted for 60 hours in an ODHE reaction.

[0042] FIG. 25 depicts the schematic reaction network of an ODHE reaction with an exemplary B-CHA catalyst. The ethyl radical (C2Hs*) plays a central role in the reaction network by coupling the HOO* and HO* reaction cycles to form ethylene. DETAILED DESCRIPTION

[0043] One aspect of the present disclosure is a process of oxidative dehydrogenation of ethane to ethylene, the process including contacting an input feed gas including ethane with an oxidative dehydrogenation catalyst including a boron-containing zeolite in the presence of an oxygen, wherein the contacting occurs at a reaction temperature in the range of 450 to 650°C and at a pressure in the range of 0.5 to 20 atm, for a suitable amount of residence time to oxidatively dehydrogenate at least a portion of the ethane to produce a product stream including ethylene, wherein the boron-containing zeolite contains pores bounded by eight tetrahedral Si and / or B atoms.

[0044] As used herein, "residence time" refers to the amount of time the input gas remains in a reactor or within a reaction zone. Any reactor commonly used in the art to perform oxidative dehydrogenation reactions can be used in the processes disclosed herein. In exemplary embodiments, the reactor is about 10 mL in volume and configured to accept the input gas at a flow rate of about 15 mL / min.

[0045] In exemplary embodiments, the suitable amount of residence time to oxidatively dehydrogenate at least a portion of the ethane to produce a product stream including ethylene is about 1.5 min, from about 0.1 min to about 10 min, or about 1 minute to about 2 minutes. Those of ordinary skill will appreciate that the amount of residence time can vary based on the equipment used to perform the ODHE reaction, the rate of the ODHE reaction and the amount of input feed gas.

[0046] As used herein, " time on stream (TOS)" means the amount of time the oxidative dehydrogenation catalyst stays in a reactor or a reaction zone. Those of ordinary skill will appreciate that the TOS can vary based on the equipment used to perform the ODHE reaction, the rate of the ODHE reaction and the amount of input feed gas. Accordingly, those of ordinary skill would be readily capable of determining the appropriate reaction conditions needed to achieve a TOS of, for example, 1 hour, 5 hours, 10 hours, 20 hours, 30 hours, 40 hours, 60 hours or over 60 hours.

[0047] In exemplary embodiments, the boron-containing zeolite used in the process has a Type Code selected from the group consisting of CHA, RTH, DDR, LEV, and NON. These type codes are commonly used by those of ordinary skill in the art to classify the structural framework of zeolite structures and can be found on the Database of Zeolite Structures. Barrer (R.M. Barrer, Pure Appt. Chem. 51 , 1091 (1979)) and McCusker et al. (L.B. McCusker, F. Liebau and G. Engelhardt, Pure Appl. Chem. 73, 381 (2001)) also discuss the rules setup by the IUPAC Commission on Zeolite Nomenclature on how to classify zeolite catalyst structures. In exemplary embodiments, the boron-containing zeolite used in the process includes Zeolite RUB-13, Zeolite DDR, Zeolite RUB-1 , Zeolite Nonasil, Chabazite, or mixtures thereof.

[0048] In exemplary embodiments, the boron-containing zeolite used in the process is a boron chabazite.

[0049] In exemplary embodiments, the boron-containing zeolite used in the process is a boron chabazite that includes or has a composition represented by:

[0050] |(H+)h(M+)m(N2+)n|[(SiO2)l2-x(TO2)y(BO-2)z(WO-2)u], wherein T is Ge, Ti, Zr, Hf, or mixtures thereof; B is boron; W is Al, Ga, Fe, or mixtures thereof; H+is hydrogen ion; M+is an alkali metal ion including Li+, Na+, K+, Cs+, or mixtures thereof; N2+is an alkaline metal ion including Mg2+and / or Ca2+; 0<x<2; 0<y<0.5, or 0<y<0.1 , or 0<y<0.01 ; 0.01 <z<2, or 0.1<z<1.5, or 0.3<z<1 ;

[0051] 0<u<0.5 or 0<u<0.3 0<u<0.1 ; 0<h<2; 0<m<0.2, or 0<m<0.1 , or 0<m<0.01 ; and / or h+m+2n = z+u.

[0052] As used herein, the term "about" refers to a value that is ± 5% of the stated value. In addition, it is understood that reference to a range of a first value to a second value includes the range of the stated values, e.g., a range of about 1 to about 5 also includes the more precise range of 1 to 5. It is also understood that the ranges disclosed herein include any selected subrange within the stated range, e.g., a subrange of about 50 to about 60 is contemplated in a disclosed range of about 1 to about 100.

[0053] In exemplary embodiments, the process includes a step of heating the oxidative dehydrogenation catalyst to a temperature at or about 600°C, 650°C, or 700°C for a suitable amount of activity induction time, in the presence of an activityinduction feed gas including 10 to 30 vol% of oxygen, before the step of contacting ethane with the oxidative dehydrogenation catalyst. In exemplary embodiments, the activity-induction feed gas includes ethane.

[0054] In exemplary embodiments, the process includes a step of heating the oxidative dehydrogenation catalyst to a temperature ranging from about 500°C to 600°C. Surprisingly, an advantage of these exemplary embodiments is that the oxidative dehydrogenation catalyst is able to maintain good ethane to ethylene selectivity, stability and good reactivity. Subjecting the oxidative dehydrogenation catalyst to temperatures above 700°C has been shown to deteriorate its selectivity for ethylene production, stability and reactivity.

[0055] In exemplary embodiments, the input feed and / or the activity-induction feed gas includes a carrier gas, wherein the carrier gas includes one or more of helium, nitrogen, carbon dioxide, and steam.

[0056] In exemplary embodiments, the contacting of the input feed gas including ethane with the oxidative dehydrogenation catalyst including a boron-containing zeolite in the presence of the oxygen includes contacting the input feed gas including ethane with an effective amount of the oxidative dehydrogenation catalyst. In exemplary embodiments, the effective amount of oxidative dehydrogenation catalyst is at least 1 mg, at least 10 mgs, at least 50 mgs, at least 100 mgs, at least 125 mgs, at least 250 mgs, at least 300 mgs, at least 350 mgs, at least 400 mgs, at least 450 mgs, at least 500 mgs, at least 550 mgs, at least 600 mgs, at least 650 mgs, or at least 700 mgs. Those of ordinary skill in the art understand that the effective amount of oxidative dehydrogenation catalyst is dependent upon the effective rate of the ODHE reaction and are capable of adjusting the amount of the oxidative dehydrogenation catalyst accordingly.

[0057] In exemplary embodiments, the contacting of the input feed gas including ethane with the oxidative dehydrogenation catalyst including a boron-containing zeolite occurs under an oxygen partial pressure of about at least 0.1 kPa, at least 5 kPa, at least 10 kPA, at least 15 kPa, at least 20 kPa or at least 25 kPa. Those of ordinary skill in the art understand that the oxygen partial pressure is dependent upon the scale of the ODHE reaction and are capable of adjusting the oxygen partial pressure accordingly.

[0058] In exemplary embodiments, the contacting of the input feed gas including ethane with the oxidative dehydrogenation catalyst including a boron-containing zeolite occurs under an ethane partial pressure of at least 0.1 kPa, at least 5 kPa, at least 10 kPA, at least 15 kPa, at least 20 kPa, at least 25 kPa or at least 30 kPa. Those of ordinary skill in the art understand that the ethane partial pressure is dependent upon the scale of the ODHE reaction and are capable of adjusting the ethane partial pressure accordingly. In exemplary embodiments, the boron-containing zeolite used in the process is a boron chabazite that has a boron content in the range of 0.1 to 5%, or 0.3 to 3%, or 0.5 to 1.5%, by weight based on the total weight of the boron-containing chabazite.

[0059] In exemplary embodiments, the boron-containing zeolite used in the process is a boron chabazite that has a micropore volume in the range of 0.1 to 0.35 cm3 / g, or 0.15 to 0.32 cm3 / g, or 0.20 to 0.30 cm3 / g.

[0060] In exemplary embodiments, the boron-containing zeolite used in the process is a boron chabazite that has a BET surface area in the range of 300 to 600 m3 / g, or 350 to 570 m3 / g, or 400 to 550 m3 / g.

[0061] In exemplary embodiments, the boron-containing zeolite used in the process is a boron chabazite that has an average particle size in the range of 0.3 to 30 pm, or 0.4 to 20 pm, or 0.5 to 12 pm.

[0062] In exemplary embodiments, the contacting of the input feed gas including ethane with the oxidative dehydrogenation catalyst including a boron-containing zeolite in the presence of the oxygen includes contacting the input feed gas including ethane with the oxygen in a volumetric ratio of ethane to oxygen of 5:1 to 1 :1 , 3:1 to 3:2, or 5:2 to 5:3.

[0063] In exemplary embodiments, the contacting of the input feed gas including ethane with the oxidative dehydrogenation catalyst including a boron-containing zeolite in the presence of the oxygen occurs for at least 1 hour, at least 10 hours, at least 20 hours, at least 30 hours, at least 40 hours, at least 50 hours or at least 60 hours.

[0064] In exemplary embodiments, the contacting of the input feed gas including ethane with the oxidative dehydrogenation catalyst including a boron-containing zeolite in the presence of the oxygen occurs at a pressure in the range of 0.5 to 20 atm, or 0.6 to 10 atm, or 0.75 to 5 atm.

[0065] In exemplary embodiments, the contacting of the input feed gas including ethane with the oxidative dehydrogenation catalyst including a boron-containing zeolite in the presence of the oxygen includes providing the input feed gas into a reaction zone at a rate of about at least 10mL / min, about at least 15 mL / min, about at least 20 mL / min, about at least 25 mL / min or about at least 30 mL / min. Those ordinarily skilled in the art understand that the rate at which the input feed gas enters into the reaction zone depends upon the scale of the ODHE reaction and are capable of adjusting the input feed gas rate accordingly.

[0066] In exemplary embodiments, the input feed gas contains about 10 vol% ethane, about 20 vol% ethane, about 30 vol% ethane, about 40 vol% ethane or about 50 vol% ethane.

[0067] In exemplary embodiments, the boron-containing zeolite used in the process is a boron chabazite that exhibits ethylene selectivity of at least 70%, 80%, or 85% at an ethane conversion rate of at least 40%, 20% or 10%, respectively.

[0068] In exemplary embodiments, the product stream includes one or more of carbon monoxide, water vapor (steam), carbon dioxide, methane, and / or unreacted ethane.

[0069] Another aspect of the present disclosure is a system for producing ethylene by oxidative dehydrogenation of ethane, the system including one or more of: (i) a reactor including (a) one or more inlets configured to receive one or more input feed gases; (b) an oxidative dehydrogenation catalyst including a boron-containing zeolite configured to communicate with one or more input feed gases, wherein the boron-containing zeolite contains pores bounded by eight tetrahedral Si and / or B atoms; and (c) an outlet configured to release a product stream from the reactor, wherein the product stream includes ethylene and residual ethane; (ii) a temperature controller unit configured to control the temperature inside the reactor in a temperature range of 450-650 °C; (iii) a flow controller configured to control a flow rate and a residence time of one or more input feed gases and at least one product stream; (iv) a pressure controller unit configured to control a pressure inside the reactor in a range of 0.5-20 atm; and an optional separations unit configured to receive a first product stream and separate ethylene from the first product stream.

[0070] In exemplary embodiments, the reactor is configured to receive input feed gases including one or more of ethane, oxygen, and / or a carrier gas.

[0071] In exemplary embodiments, the outlet of the reactor is configured to release a product stream including ethylene and residual ethane.

[0072] In exemplary embodiments, the reactor is a fixed bed flow reactor. In exemplary embodiments, the boron-containing zeolite of the oxidative dehydrogenation catalyst in the reactor has a Type Code selected from CHA, RTH, DDR, LEV, or NON.

[0073] In exemplary embodiments, the boron-containing zeolite of the oxidative dehydrogenation catalyst in the reactor includes Zeolite RUB-13, Zeolite DDR, Zeolite RUB-1 , Zeolite Nonasil, Chabazite, or mixtures thereof.

[0074] In exemplary embodiments, the boron-containing zeolite of the oxidative dehydrogenation catalyst in the reactor is a boron chabazite.

[0075] In exemplary embodiments, the boron-containing zeolite of the oxidative dehydrogenation catalyst in the reactor is a boron chabazite having a composition represented by:

[0076] |(H+)h(M+)m(N2+)n|[(SiO2)l2-x(TO2)y(BO-2)z(WO-2)u], wherein T is Ge, Ti, Zr, Hf, or mixtures thereof; B is boron; W is Al, Ga, Fe, or mixtures thereof; H+is hydrogen ion; M+is an alkali metal ion including Li+, Na+, K+, Cs+, or mixtures thereof; N2+is an alkaline metal ion including Mg2+and / or Ca2+; 0<x<2; 0<y<0.5, or 0<y<0.1 , or 0<y<0.01 ; 0.01 <z<2, or 0.1<z<1.5, or 0.3<z<1 ; 0<u<0.5, 0<u<0.3, or 0<u<0.1 ; 0<h<2; 0<m<0.2, or 0<m<0.1 , or 0<m<0.01 ; and / or h+m+2n = z+u.

[0077] Without wishing to be bound by any particular theory, it is believed that the embodiments involving the use of a boron-containing chabazite catalyst are able to greatly reduce the over oxidation problem that commonly occurs during ODHE with their improved stability that results from their zeolite framework. This is unexpected given that zeolite catalysts similar to those disclosed herein are evaluated for their ability to convert propane to propylene and have not been extensively researched for their ability to convert ethane to ethylene. The zeolite framework of these catalysts allows for excellent ODHE reaction rates, with high ethylene selectivity in the disclosed temperature ranges. The catalytic rates of ODHE have been observed to increase over time on stream when boron-containing chabazite catalyst are used; thereby suggesting that the partial framework deboronation of these catalysts increases their number of active sites. The observed negligible decrease of boron content in these catalysts also suggests that a barrier to diffusion of boron species caused by the zeolite small pores enhances catalyst stability. This observation is surprisingly unexpected since in other B-catalysts e.g., boron nitride) the boron evaporates and comes out of the reactor.

[0078] Examples

[0079] The present disclosure will be described in more detail with reference to the following Examples, which shows exemplary embodiments in accordance with the present disclosure. The present disclosure is not limited to these exemplary embodiments.

[0080] Example 1 : Characterization of Exemplary Boron-containing Chabazite Catalysts and Evaluation of their Efficacies in ODHE

[0081] 1 . Structure and Properties of the Catalysts

[0082] According to an EDS analysis, fi-BN has a boron content of 44.9 wt%, while the ICP analysis shows that a fresh boron-containing chabazite catalysts (B-CHA) has a boron content of 1 .01 wt% (Table 1).

[0083] Table 1 : Boron contents and textural properties of fi-BN and B-CHA catalysts

[0084] Catalyst Boron content Micropore Mesopore BET surface

[0085] (wt%) volume0volume aread fi-BN 44.9a- 0.05 6

[0086] Fresh B-CHA 1.01b0.26 0.03 543

[0087] Spent B-CHA 0.98b0.24 0.03 496

[0088] (20 h ODHE)

[0089] Spent B-CHA 0.98b0.20 0.03 418

[0090] (60 h ODHE) aDetermined by EDS. bDetermined by ICP-OES. determined by f-plot method, determined by BET method.

[0091] The catalysts were characterized by XRD, SEM, N2 physisorption isotherms, and XPS (FIGs. 1-9). B-CHA diffraction patterns were indexed to the corresponding diffraction peaks of CHA, confirming the structure and the absence of any crystalline impurities (FIG. 4). FIG. 5 shows SEM images of B-CHA catalysts, revealing an average crystal size of 3.9 pm and a pseudo-cubic crystal morphology. The N2 physisorption results showed a type-l isotherm for the B-CHA catalysts (FIG. 6), and a large micropore volume (0.26 cm3g-1) and BET surface area (543 m2g-1) (Table 1 ) as expected from the structure of the zeolite.

[0092] Catalytic Properties of B-CHA

[0093] FIG. 10 plots the ethylene selectivity versus the ethane conversion for the h- BN and fresh B-CHA catalysts, with the B-CHA catalyst having better ethylene selectivity than most of the reported vanadium and nickel-containing catalysts, h- BN demonstrated high ethylene selectivity at different conversions, with 95% and 75% ethylene selectivity at 11 % and 43% ethane conversions, respectively. The B- CHA catalysts also displayed excellent ethylene selectivity as fi-BN, with 86% and 73% ethylene selectivity at 21 % and 42% ethane conversions, respectively. The product distribution of the fi-BN and B-CHA catalysts are compared in FIG. 11 at similar conversions and the same reaction temperatures. High ethylene selectivity was obtained with the B-CHA catalysts, with CO as the main byproduct (Xc2H6 = 14%, Sc2H4 = 87%, Sco = 8%, Sco2 = 3%, SCH4 = 2%). In the / ?-BN catalyzed reactions, ethylene was also the dominant product, with CO as the major byproduct, and no CO2 was observed (Xc2H6 = 14%, Sc2H4 = 94%, Sco = 4%, Sco2 = 0%, SCH4 = 2%). The similar product distribution for B-CHA and / ?-BN could suggest that a similar underlying reaction mechanism for these two boron- containing catalysts may be present.

[0094] Fresh B-CHA achieved 21 % and 42% ethane conversions at 580 and 600 °C, respectively (FIG. 12 and FIG. 13). The ODHE activity of fresh B-CHA was mainly due to the high micropore volume and surface area (high B site availability). Fresh B-CHA maintained high ethylene selectivity at reaction temperatures ranging from 500-600°C. The stability and structural integrity of the B-CHA catalyst after ODHE were analyzed using several techniques (FIG. 14 and FIG. 15). The B-CHA catalyst showed a small monotonic increase in conversion as a function of time on stream. The B-CHA catalyst also achieved a higher final conversion while maintaining high ethylene selectivity after a 60 hour ODHE reaction at 580 °C (t ~ 0, Xc2H6 = 22%, Sc2H4 = 87%; t ~ 60 h, Xc2H6 = 27%, Sc2H4 = 86%), demonstrating excellent stability. ICP analysis showed a small (0.03 wt%) decrease in boron content after about 20 hours into the ODHE reaction, which was negligible, but afterward, the boron content remained constant up to about 60 hours into the ODHE reaction (Table 1 ). The SEM images of the spent B-CHA catalyst showed nearly unchanged morphology after this period (FIG. 5), except for the presence of small particles on the CHA crystal surface, which were likely broken off from the CHA crystals as the crystal surface was also rougher. The micropore volume, however, decreased from 0.26 cm3g_1to 0.24 cm3g_1after about 20 hours into the ODHE reaction, and then to 0.20 cm3g_1after about 60 hours into the ODHE reaction (Table 1 ). No evidence of structural damage to the zeolite based on SEM images or analysis of the XRD patterns of spent catalysts was found. There was also no evidence of mesopore formation in the N2 adsorption isotherms. Specific reaction rates did increase over time on stream.

[0095] Kinetic Investigation of ODHE over the B-CHA Catalyst

[0096] Experiments with different catalyst amounts were carried out first to rule out any mass and diffusion transfer limitations (FIG. 16). Since -rc2H6 normalized by the catalyst mass of different catalyst amounts remained similar in all the measurements, it was concluded that the reactor operated under a kinetics- controlled regime (i.e., there were no substantial mass transfer limitations). Moreover, this result also showed that the reactor operated under near isothermal conditions. A catalyst weight of 125 mg was used to further study the differential reaction conditions in the reactor.

[0097] The Eappof ethane conversion was 126 kJ mol-1over the B-CHA catalyst (FIG. 17). The rate orders of -rc2H6 on pc2H6 and P02 were measured at three different temperatures (FIG. 18). At 560°C and 580°C, -rc2H6 over the B-CHA catalyst showed nearly zero-order dependence on P02 when P02 was higher than 5.4 kPa, with 1.21 and 1.42 ethane reaction orders, respectively. At 600°C, -rc2H6 exhibited similar dependence on P02, and the ethane reaction order increased to 1 .53. Although ODHE over the B-CHA catalyst displayed Langmuir adsorption dependence on P02 at all temperatures, the ethane reaction orders were unexpected because most boron-catalyzed ODHs have second-order dependence on the partial pressure of the alkane. At lower temperatures, the ethane reaction orders over the B-CHA catalyst resembled the propane reaction order of ODHP over B-MFI, and that over the V2O5 supported on amorphous AIPO4. First-order dependence may result from the microporous character of the B-CHA catalyst, leading to differences in catalytic kinetics from non-porous fi-BN, even if the reaction network may be similar.

[0098] For the B-CHA catalyst, ethane activation is likely to occur inside the zeolite micropores as observed with B-MFI since both catalysts showed first-order dependence on the alkane partial pressure. The increased ethane reaction order to 1 .53 at 600°C could indicate more activation in the gas phase outside the zeolite crystals (e.g., in the inter-particle space and void fraction of the reactor) at higher temperatures. This is different from the kinetics of / BN (FIG. 19), and could explain the sudden reactivity increase at 600°C, which is consistent with the higher reported Eappof fi-BN (283-344 kJ mol-1). Eappis usually higher when gas-phase radicals are involved in the mechanism and ethane activation happens mostly in the gas phase for / 7-BN catalyzed ODHE.

[0099] High Concentration of Silanol Groups for B-CHA Catalysts

[0100] The29Si MAS NMR spectra of the B-CHA catalysts contained signals from - 93 to -102 ppm and from -109 to -113 ppm that are assigned to Q3and Q4Si atoms. The spectrum of the as-made B-CHA catalyst revealed that the framework of this sample was highly defective, with a Q3 / (Qs+Q4) ratio of 0.44 (FIG. 20 and Table 2), reflecting the presence of a network of hydrogen-bonded siloxy groups balancing the positive charge of the structure-directing agent (SDA).

[0101] Table 2: 1 D29Si MAS NMR parameters of the B-CHA catalysts.

[0102] Catalyst 5iS0(ppm) Coordination Relative intensity (%)

[0103] As-made B-CHA -98.42 Q344

[0104] -108.5 Q456

[0105] Fresh B-CHA -100.8 Q325

[0106] -109.9 Q475

[0107] Spent B-CHA (20 h ODHE) -100.5 Q324

[0108] -109.9 Q476

[0109] Spent B-CHA (60 h ODHE) -101.5 Q331

[0110] -110.1 Q469

[0111] The TGA trace of the as-made B-CHA catalyst showed there is one SDA per CHA cage (FIG. 21). Calcination of the air to remove the organic SDA condensed many of these silanol groups, reducing the Qs / (Q3+Q4) ratio to 0.25 (FIG. 22). This number was high since the working catalyst can have 3-4 silanol groups per cage, an important consideration in view of their role as anchors of B sites (boron sites). The amount of B in the sample was low and nominally dilute (Si / B—18), equivalent to a B concentration of 3.6 mmol (cm3)-1in crystal volume. The high concentration of silanol groups of B-CHA led to even distribution of boron on the surface area and sufficient exposure of boron species.

[0112] Active Boron Species

[0113] A solid-state NMR study of the fresh and spent B-CHA catalysts, including 1 D11B MAS and 2D11B MQMAS NMR, was undertaken to investigate the structure and evolution of boron species in these catalysts (FIG. 23 and FIG. 24). As clearly shown in 2D11B MQMAS NMR (FIG. 24), at least three boron species were present in the fresh B-CHA catalyst, and the same boron species were found in the spent B-CHA catalyst, although the relative intensity changed after ODHE. This finding allowed deconvolution of 1 D11B MAS NMR spectra to produce the11B isotropic chemical shift 8jSo (ppm), quadrupolar coupling constant CQ (MHZ), asymmetry parameter (h), and the relative intensity (%) of the three major boron sites found in the corresponding 2D11B MQMAS. The fresh B-CHA catalyst had three observed boron species with 8iS0at -1.6, 14.0, and 16.3 ppm, and the spent B-CHA catalysts after about 20 hours and after about 60 hours into the ODHE reaction also had three boron species with 8iS0at -1.8, 11.1 and 17.4 ppm and 8iso at -1 .6, 10.2 and 15.8 ppm.

[0114] The strong peak at -1 .6 ppm in the fresh B-CHA and those at -1 .8 and -1 .6 ppm in the spent B-CHA catalyst were assigned to the tetracoordinated boron (B[4]), denoted as species A (Table 3).

[0115] Table 3: Structure of the boron species in the fresh and spent B-CHA catalysts as determined from 1 D11B MAS NMR spectra.

[0116] Site

[0117] Structure

[0118] Species A may result from the reversible conversion of the trigonal boron (B[3]) that is anchored in the framework with three B-O-Si bonds. The peak at 14.0 ppm in the fresh B-CHA catalyst and those at 11 .1 and 10.2 ppm in the spent B- CHA catalyst could be assigned to B(OSi)2(OH) or B(OSi)2(OB), due to the downfield shift in observed 5iS0compared to the fully incorporated B in the chabazite framework. However, considering that boron in the samples was so dilute (Si / B~18), that diffusion of B(OH)s through 8-ring windows are sterically constrained but required to form B-O-B linkages with B groups in other cages, and that the presence of trigonal extra-framework boron was not supported by 1 D11B MAS NMR spectra, the presence of B(OSi)2(OB) moieties was ruled out and the peaks were thus assigned to B(OSi)2(OH), denoted as species B. The fact that Co of species B was much larger than that of species A, indicating the high molecular symmetry observed in species A no longer existed in species B, supported this assignment. The weak peak at 16.3 ppm in the fresh B-CHA catalyst and those at 17.4 and 15.8 ppm in the spent B-CHA catalysts could be assigned to B(OSi)(OH)x(OB)2-x (x = 1-2). For the same reasons stated above, the presence of B-O-B linkages in the samples were highly unlikely and the signals were then assigned to B(OSi)(OH)2, denoted as species C. Extra-framework boron (18-19 ppm), such as B(OH)s, was absent in the spent catalyst, indicating negligible leaching of framework boron sites after ODHE.

[0119] The comparison of the relative intensities of each species across time showed that the relative intensities of species A and B decreased and that of species C increased after about 20 and after about 60 hours into the ODHE reaction. The decrease of species A (51 % to 40% after about 20 hours into the ODHE reaction and to 37% after about 60 hours into the ODHE reaction) resulted from the hydrolysis of framework B-O-Si groups by water produced under ODHE conditions, causing the formation of B(OSi)2(OH) (species B), and further to B(OSi)(OH)2 (species C). B(OSi)(OH)2 is also suggested as the isolated active site in boron-catalyzed ODHP. The monotonic increase of the relative intensity of species C was consistent with the increasing reactivity over time (FIG. 14), suggesting that species C was responsible for initiating the ODHE activity in the B- CHA catalysts. Also, the amount of species C was likely to reach a steady state as time on stream got longer, and it was shown that steam treatments could shorten the time needed to reach the steady state.

[0120] The mechanism of ethane dehydrogenation in the B-CHA catalyst could follow the mechanism proposed by Annamalai et al. for propane dehydrogenation by NO (L. Annamalai, Y. Liu, P. Deshlahra, ACS Catalysis 9 (2019) 10324-10338). In this example, the source of radical initiators was mediated by the interaction of the zeolite boron sites with dioxygen, and the dehydrogenation proceeded through ethane hydrogen abstraction by the HO* to form ethyl radicals. These then rapidly reacted with abundant O2 to form ethylene and HOO* radicals. The hydroperoxy radical could then react with ethane (albeit more slowly); however, as also suggested by Annamalai et al., it could react with HO* to form water and O2 (FIG. 25). If this reaction was mediated by B sites, it could lead to a pseudo equilibrium of the reaction HOO* + HO* H2O + O2, explaining the positive effect of water on dehydrogenation rates of propane for fi-BN.

[0121] Conclusion:

[0122] The above experimental example demonstrates that the boron-chabazite zeolite catalysts disclosed herein are capable of catalyzing the ODHE reaction with high rates and with high ethylene selectivity at temperatures ranging from 500- 600°C. The large micropore volume, high surface area and abundant OH groups in the B-CHA catalysts contribute to their excellent performance. The catalytic rates of ODHE increased over time on stream, thereby suggesting that partial framework deboronation of these catalysts increased their number of active sites. The negligible decrease of boron content in the spent boron-chabazite zeolite catalyst also suggests that a barrier to diffusion of boron species caused by the zeolite's small pores enhances catalyst stability. The dependence of ethane consumption rate (-rc2H6) on the ethane partial pressure (pc2H6) and oxygen partial pressure (P02) changed with temperature (560-600 °C), which is consistent with the change of ethane activation pathways. The kinetic study with ethane reaction orders from 1 .21 -1 .53 was used to identify the transition of surface initiation to gas-phase initiation mechanism.

[0123] Partially bonded boron species B(OSi)2(OH) and B(OSi)(OH)2 were identified as the active sites using the NMR technique. Solids-state11B MAS NMR and FTIR spectroscopy investigations showed that catalytic rates increased as the number of B-OH groups in the catalyst grew, a result consistent with the structural characterizations and the catalyst stability test.

[0124] In view of this data, it could be inferred that the high concentration of Si-OH groups shown in the29Si MAS NMR facilitates the distribution of boron species on the high surface area of the boron-chabazite zeolite catalyst, thus leading to high ODHE activity.

[0125] Methods used in Example 1

[0126] Materials

[0127] Boric acid (B(OH)3) and tetraethylorthosilicate (TEOS, 98 wt%) were obtained from Sigma-Aldrich. Trimethyladamantylammonium hydroxide solution (TMAdaOH, 25 wt%) was purchased from Sachem Inc (aqueous technical grade). Carbosil M5 fumed silica was supplied by Cabot Inc. Hexagonal boron nitride ( / ?- BN, 99.5% (metal basis), product number: 11078) was supplied by Fisher Scientific. Hydrofluoric acid (HF, 48-51 %) was supplied by Acros Organics. Ethane, oxygen, and helium gases (>99%) were supplied by Keen Compressed Gas Co. These raw materials were used as received without further treatment.

[0128] Material Synthesis

[0129] The boron-containing chabazite was synthesized as follows. First, 17.2 g trimethyladamantylammonium hydroxide solution (TMAdaOH, 25 wt%) was added to 20.7 g deionized (DI) water. Then, 0.413 g boric acid was dissolved in the solution with stirring for 30 min. Finally, 5.03 g Carbosil M-5 was added to the solution while being stirred. The mixture was stirred for another 30 minutes to afford a gel. The gel was transferred to an autoclave and heated at 160 °C for 3 days under rotation. The product was washed with DI water and centrifuged, then dried at 80 °C overnight. The as-made zeolite was calcined at 580°C in flowing air for 8 h with a ramping rate of 2 °C min-1to remove the organic template. The powder after calcination is denoted as B-CHA.

[0130] The siliceous chabazite was synthesized as follows. First, a solution of 11 .78 g tetraethylorthosilicate (TEOS, 98 wt%) and 23.87 g trimethyladamantylammonium hydroxide solution (TMAdaOH, 25 wt%) was stirred for 24 hours at room temperature. With continuous stirring, the solution was heated to evaporate 13.4 g water and 10.4 g ethanol (23.8 g total), resulting in a final H2O:SiC>2 ratio of 3. Finally, 1.18 g hydrofluoric acid (HF, 48-51 %) was added. The thick paste was transferred to an autoclave and heated at 150°C for 2 days under rotation. The product was washed with DI water, filtered, then dried at 80 °C overnight. The as- made zeolite was calcined at 550°C in flowing air for 8 h with a ramping rate of 3 °C min-1. The powder after calcination is denoted as Si-CHA.

[0131] Characterization

[0132] Powder X-ray diffraction (XRD) patterns were obtained using a Bruker powder diffractometer (D8 XRD) with a Cu Ka radiation (40 kV, 40 mA) as the X-ray source, with a step size of 0.04° and 1 s per step. The catalyst samples' morphologies and elemental mappings were determined using a scanning electron microscope (SEM, Auriga-60, ZEISS) and energy-dispersive X-ray spectroscopy (EDS) spectra, respectively. Prior to the SEM measurement, the samples were coated with gold / palladium alloy. Textural properties of all catalysts were obtained by employing N2 physisorption experiments at 77 K on a 3Flex surface characterization analyzer (Micromeritics). Before the physisorption experiments, all the samples were degassed at 300°C overnight under vacuum. The boron and silica contents of the calcined zeolite samples were determined by inductively coupled plasma optical emission spectrometry (ICP-OES) analysis (Galbraith Laboratories, TN).

[0133] All the NMR measurements were performed on a Bruker AVANCE-III 500 MHz spectrometer operating at the resonance frequency of 160.46 MHz and 99.347 MHz for the11B and29Si nucleus, respectively, with a Bruker 4.0 mm multinuclear HX MAS probe at a spinning rate of 10 kHz within ± 3 Hz. A broad background boron signal from the MAS stator materials was removed using a DEPTH pulse sequence with a small tippling angle & corresponding to a rf pulse length of 1 .9 ps. The effectiveness of boron background removal was verified by a rotor packed with glycine. A 3-pulse (5.7 ps, 1 .9 ps, and 20 ps) pulse program with a z-filter was used to acquire 2D MQMAS spectra. The number of scans was set to 900 with 64 increments in evolution dimension. A 2D MQMAS spectra was processed by first applying Fourier transform to both dimensions followed by a shearing transformation. A 2-s recycle delay was used for all11B experiments and a 30-s recycle delay was used for all29Si experiments. All11B NMR spectra were referenced to a sharp resonance of NaBH4 at -42.01 ppm as a secondary external reference.

[0134] Fourier transform infrared (FTIR) spectra were collected on an Agilent CARY 660 spectrometer equipped with an MCT detector. First, the sample (~50 mg) was pressed into a thin disk and placed in the cell quipped with KBr windows. The samples were heated to 550 °C for 1 h under vacuum for dehydration to remove adsorbed molecules and cooled down to each measurement temperature. The spectra were collected by averaging 32 scans with a resolution of 4 cm'1against the background spectrum taken with an empty cell. X-ray photoelectron spectroscopy (XPS) spectra were collected using a Thermo Fisher K-Alpha+ system. Thermogravimetric analysis (TGA) was conducted on Discovery TGA instrument.

[0135] Catalytic Reactions and Kinetic Measurements

[0136] ODHE was measured in a fixed-bed quartz reactor (I.D. = 4 mm, O.D. = 6 mm, length = 536 mm). The catalyst (20-40 mesh) was fixed using glasswool. A thermocouple was placed adjacent to the catalyst beds. The reactor was heated to 600°C with a ramping rate of 5°C min-1under 20 vol% O2 / 80 vol% He. After the temperature stabilized, catalysts were treated with 20 vol% C2H6 / 12 vol% O2 / 68 vol% He (total flow rate = 15 mL min'1) for 12 hours before data was collected for all experiments. The temperature was then step-wise cooled down (20°C / step) for the temperature-dependent experiment. The reactor effluent was injected into an online gas chromatograph (GC) (Agilent 7890) equipped with FID (with an RT-Q-BOND column for CF analysis) and TCD (with a HayeSep Q and Molseive 13X column for C2H6, O2, C2H4, CO, and CO2 analysis) detectors after going through a condenser. Ethane and oxygen conversions (Xc2H6, X02), product selectivity (Si), carbon balance (C.B.), and ethane consumption rate (-rc2H6 (mmolc2H6 gcat'1IT1)) were calculated as follows:

[0137] Where Fc2H6,in / Fo2,in and Fc2H6,out / Fo2,out represent molar flow rate of C2H6 / O2 at the inlet and outlet of the reactor, i represents C2H4, CO, CO2, CH in the effluent gas, ni is the number of carbon atoms of i, ,out is molar flow rate of i at the outlet of the reactor and meat is catalyst weight.

[0138] C.B.s were above 90% in all but one experiment (89% at 42% conversion and 600 °C). The blank reactions were excluded by experiments with quartz sand. The B-CHA catalyst was used in the temperature-dependent experiment for about 20 hours and denoted as B-CHA (20 h ODHE). B-CHA (60 h ODHE) went through the temperature-dependent experiment but ran for about 60 hours at 580°C for the stability test. Data points were collected for about 60 hours and selected from the GC traces with similar time intervals but not exactly 3 hours. The rate was measured at differential conversion (<12%) for kinetic investigations. The apparent activation energy (Eapp) was determined at 500-600°C. It will be appreciated by those skilled in the art that the present disclosure can be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The presently disclosed embodiments are therefore considered in all respects to be illustrative and not restricted. The scope of the disclosure is indicated by the appended claims rather than the foregoing description and all changes that come within the meaning and range and equivalence thereof are intended to be embraced therein.

Claims

CLAIMS:1 . A process of oxidative dehydrogenation of ethane to ethylene, the process comprising: contacting an input feed gas comprising ethane with an oxidative dehydrogenation catalyst comprising boron-containing zeolite in the presence of an oxygen, wherein the contacting occurs at a reaction temperature in the range of 450 to 650°C, or 475 to 625°C, or 500 to 600°C, and at a pressure in the range of 0.5 to 20 atm, or 0.6 to 10 atm, or 0.75 to 5 atm, for a suitable amount of residence time to oxidatively dehydrogenate at least a portion of the ethane to produce a product stream comprising ethylene, wherein the boron-containing zeolite contains pores bounded by eight tetrahedral Si and / or B atoms.

2. The process according to claim 1 , wherein the boron-containing zeolite has a Type Code selected from the group consisting of CHA, RTH, DDR, LEV, and NON.

3. The process according to claim 1 or claim 2, wherein the boron-containing zeolite comprises Zeolite RUB-13, Zeolite DDR, Zeolite RUB-1 , Zeolite Nonasil, Chabazite, or mixtures thereof.

4. The process according to any one of claims 1-3, wherein the boron- containing zeolite is a boron chabazite.

5. The process according to claim 4, wherein the boron chabazite has a composition represented by:|(H+)h(M+)m(N2+)n|[(SiO2)l2-x(TO2)y(BO-2)z(WO-2)u] wherein:T is Ge, Ti, Zr, Hf, or mixtures thereof,B is boron,W is Al, Ga, Fe, or mixtures thereof,H+is hydrogen ion,M+is an alkali metal ion comprising Li+, Na+, K+, Cs+, or mixtures thereof, N2+is an alkaline metal ion comprising Mg2+and / or Ca2+, 0<x<2, 0<y<0.5, or 0<y<0.1 , or 0<y<0.01 , 0.01<z<2, or 0.1<z<1.5, or 0.3<z<1 , 0<u<0.5, or 0<u<0.3 0<u<0.1 , 0<h<2, 0<m<0.2, or 0<m<0.1 , or 0<m<0.01 , and h+m+2n = z+u.

6. The process according to any of claims 1-5, comprising a step of heating the oxidative dehydrogenation catalyst to a temperature at or about 600°C, 650°C, or 700°C for a suitable amount of activity induction time, in the presence of an activityinduction feed gas comprising 10 to 30 vol% of oxygen, before the step of contacting ethane with the oxidative dehydrogenation catalyst.

7. The process according to claim 6, wherein the activity-induction feed gas comprises ethane.

8. The process according to claim 6 or 7, wherein the input feed and / or the activity-induction feed gas further comprises a carrier gas, wherein the carrier gas comprises one or more of helium, nitrogen, carbon dioxide, and steam.

9. The process according to any one of claims 4-8, wherein the boron- containing chabazite has a boron content in the range of 0.1 to 5%, or 0.3 to 3%, or 0.5 to 1 .5%, by weight based on the total weight of the boron-containing chabazite.

10. The process according to any one of claims 4-9, wherein the boron- containing chabazite has a micropore volume in the range of 0.1 to 0.35 cm3 / g, or 0.15 to 0.32 cm3 / g, or 0.20 to 0.30 cm3 / g.

11. The process according to any one of claims 4-10, wherein the boron- containing chabazite has a BET surface area in the range of 300 to 600 m3 / g, or 350 to 570 m3 / g, or 400 to 550 m3 / g.

12. The process according to any one of claims 4-11 , wherein the boron- containing chabazite has an average particle size in the range of 0.3 to 30 pm, or 0.4 to 20 pm, or 0.5 to 12 pm.

13. The process according to any one of claims 1-12, wherein the contacting comprises a volumetric ratio of ethane to oxygen of 5:1 to 1 :1 , 3:1 to 3:2, or 5:2 to 5:3.

14. The process of claim 13, wherein the boron-containing chabazite exhibits ethylene selectivity of at least 70%, 80%, or 85% at an ethane conversion rate of at least 40%, 20% or 10%, respectively.

15. The process according to any one of claims 1-14, wherein the product stream further comprises one or more of carbon monoxide, water vapor (steam), carbon dioxide, methane, and unreacted ethane.

16. The process according to any one of claims 1-15, comprising a step of separating ethylene from the product stream.

17. A system for producing ethylene by oxidative dehydrogenation of ethane, comprising:(i) a reactor comprising:(a), one or more inlets configured to receive one or more input feed gases;(b). an oxidative dehydrogenation catalyst comprising a boron- containing zeolite configured to communicate with one or more input feed gases, wherein the boron-containing zeolite contains pores bounded by eight tetrahedral Si and / or B atoms, and(c.) an outlet configured to release a product stream from the reactor;(ii) a temperature controller unit configured to control a temperature inside the reactor in a temperature range of 450-650 °C or 500-600 °C;(iii) a flow controller configured to control a flow rate and a residence time of one or more input feed gases and at least one product stream;(iv) a pressure controller unit configured to control a pressure inside the reactor in a range of 0.5-20 atm, 0.6-10 atm, or 0.75 to 5 atm; and an optional separations unit configured to receive a first product stream and separate ethylene from the first product stream.

18. The system according to claim 17, wherein the reactor is a fixed bed flow reactor.

19. The system according to claim 17 or claim 18, wherein the boron-containing zeolite has a Type Code selected from the group consisting of CHA, RTH, DDR, LEV, and NON.

20. The system according to any one of claims 17-19, wherein the boron- containing zeolite comprises Zeolite RUB-13, Zeolite DDR, Zeolite RUB-1 , Zeolite Nonasil, Chabazite, or mixtures thereof.

21. The system according to any one of claims 17-20, wherein the boron- containing zeolite is a boron chabazite.

22. The system according to claim 21 , wherein the boron chabazite has a composition represented by:|(H+)h(M+)m(N2+)n|[(SiO2)l2-x(TO2)y(BO-2)z(WO-2)u] wherein:T is Ge, Ti, Zr, Hf, or mixtures thereof;B is boron;W is Al, Ga, Fe, or mixtures thereof;H+is hydrogen ion;M+is an alkali metal ion comprising Li+, Na+, K+, Cs+, or mixtures thereof; N2+is an alkaline metal ion comprising Mg2+and / or Ca2+; 0<x<2;0<y<0.5, or0<y<0.1, or0<y<0.01;0.01<z<2, or0.1<z<1.5, or0.3<z<1;0<u<0.5, or0<u<0.30<u<0.1;0<h<2; 0<m<0.2, or 0<m<0.1 , or 0<m<0.01 ; and h+m+2n = z+u.

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