Evolution of the optimal catalytic systems for the oxidative dehydrogenation of ethane: The role of adsorption in the catalytic performance

Molten-Salt-Mediated Chemical Looping Oxidative Dehydrogenation of Ethane with In-Situ Carbon Capture and Utilization

The molten-salt-mediated oxidative dehydrogenation (MM-ODH) of ethane (C2H6) via a chemical looping scheme represents an effective carbon capture and utilization (CCU) method for the valorization of ethane-rich shale gas and concurrent mitigation of carbon dioxide (CO2) emissions. Here, stepwise experimentation with Li2CO3-Na2CO3-K2CO3 (LNK) ternary salts (i) assessed how each component of the LNK mixture impacted ethane MM-ODH performance and (ii) explored physicochemical and thermodynamic mechanisms behind melt-induced changes to ethylene (C2H4) and carbon monoxide (CO) yields. Of fifteen screened LNK compositions, nine exhibited ethylene yields greater than 50 % at 800 °C while maintaining C2H4 selectivities of 85 % or higher. LNK salts rich in Li2CO3 content yielded more ethylene and CO on average than their counterparts, and net CO2 capture per cycle reached a maximum of ~75 %. Extended MM-ODH cycling also demonstrated long-term stability of a high-performing LNK medium. Density functional theory (DFT) calculations and ab initio molecular dynamics (AIMD) simulations suggested that the molten salt does not directly activate C2H6. Meanwhile, an empirical model informed by experimental data and reaction thermodynamics adequately predicted overall MM-ODH performance from LNK composition and provided insights into the system's primary drivers.

Influence of the Au-Ti Active Site of the Titanosilicate MWW Zeolite on the Catalytic Activity of Ethane Dehydrogenation in the Presence of O2

The titanosilicate zeolite with a MWW topology structure was synthesized by the atom-planting method through the dehydrochlorination of the hydroxyl group in the deboronated ERB-1 zeolite (D-ERB-1) and TiCl₄, and Au was further loaded with the deposition precipitation method to apply for the ethane direct dehydrogenation (DH) and dehydrogenation of ethane in the presence of O₂ (O₂-DH). It was found that Au nanoparticles (NPs) below 5 nm exhibited good activity for ethane direct dehydrogenation and O₂-DH. The addition of titanium can not only anchor more Au but also make Au have a more dispersed homogeneous distribution. The ethane O₂-DH catalytic performances of Au-loaded Ti-incorporated D-ERB-1 (Ti-D-ERB-1) were compared to those of Au-loaded ZnO-D-ERB-1 and pure silicate D-ERB-1. The results confirm that ethane O₂-DH catalyzed by Au-Ti paired active sites is a tandem reaction of catalytic ethane DH and selective H₂ combustion (SHC) of generated H₂. According to the experimental results and calculated kinetic parameters, such as the activation energy of DH and SHC reaction heat of O₂-DH, SHC catalyzed by the Au/Ti-D-ERB-1 catalyst containing the Au-Ti active site can not only break the ethane dehydrogenation thermodynamic equilibrium limitation to improve the ethylene yield but also suppress the CO₂ and CO selectivity.

State-of-the-Art Review of Oxidative Dehydrogenation of Ethane to Ethylene over MoVNbTeOx Catalysts

Ethylene is mainly produced by steam cracking of naphtha or light alkanes in the current petrochemical industry. However, the high-temperature operation results in high energy demands, high cost of gas separation, and huge CO2 emissions. With the growth of the verified shale gas reserves, oxidative dehydrogenation of ethane (ODHE) becomes a promising process to convert ethane from underutilized shale gas reserves to ethylene at a moderate reaction temperature. Among the catalysts for ODHE, MoVNbTeOx mixed oxide has exhibited superior catalytic performance in terms of ethane conversion, ethylene selectivity, and/or yield. Accordingly, the process design is compact, and the economic evaluation is more favorable in comparison to the mature steam cracking processes. This paper aims to provide a state-of-the-art review on the application of MoVNbTeOx catalysts in the ODHE process, involving the origin of MoVNbTeOx, (post-) treatment of the catalyst, material characterization, reaction mechanism, and evaluation as well as the reactor design, providing a comprehensive overview of M1 MoVNbTeOx catalysts for the oxidative dehydrogenation of ethane, thus contributing to the understanding and development of the ODHE process based on MoVNbTeOx catalysts.

Light olefin synthesis from a diversity of renewable and fossil feedstocks: state-of the-art and outlook

Light olefins are important feedstocks and platform molecules for the chemical industry. Their synthesis has been a research priority in both academia and industry. There are many different approaches to the synthesis of these compounds, which differ by the choice of raw materials, catalysts and reaction conditions. The goals of this review are to highlight the most recent trends in light olefin synthesis and to perform a comparative analysis of different synthetic routes using several quantitative characteristics: selectivity, productivity, severity of operating conditions, stability, technological maturity and sustainability. Traditionally, on an industrial scale, the cracking of oil fractions has been used to produce light olefins. Methanol-to-olefins, alkane direct or oxidative dehydrogenation technologies have great potential in the short term and have already reached scientific and technological maturities. Major progress should be made in the field of methanol-mediated CO and CO₂ direct hydrogenation to light olefins. The electrocatalytic reduction of CO₂ to light olefins is a very attractive process in the long run due to the low reaction temperature and possible use of sustainable electricity. The application of modern concepts such as electricity-driven process intensification, looping, CO₂ management and nanoscale catalyst design should lead in the near future to more environmentally friendly, energy efficient and selective large-scale technologies for light olefin synthesis.

Mixed Metal Oxides of M1 MoVNbTeOx and TiO2 as Composite Catalyst for Oxidative Dehydrogenation of Ethane

Composite catalysts of mixed metal oxides were prepared by mixing a phase-pure M1 MoVNbTeOx with anatase-phase TiO2. Two methods were used to prepare the composite catalysts (the simple physically mixed or sol-gel method) for the improvement of the catalytic performance in the oxidative dehydrogenation of ethane (ODHE) process. The results showed that TiO2 particles with a smaller particle size were well dispersed on the M1 surface for the sol-gel method, which presented an excellent activity for ODHE. At the same operating condition (i.e., the contact time of 7.55 gcat·h/molC2H6 and the reaction temperature of 400 °C), the M1-TiO2-SM and M1-TiO2-PM achieved the space time yields of 0.67 and 0.52 kgC2H4/kgcat/h, respectively, which were about ~76% and ~35% more than that of M1 catalyst (0.38 kgC2H4/kgcat/h), respectively. The BET, ICP, XRD, TEM, SEM, H2-TPR, C2H6-TPSR, and XPS techniques were applied to characterize the catalysts. It was noted that the introduction of TiO2 raised the V5+ abundance on the catalyst surface as well as the reactivity of active oxygen species, which made contribution to the promotion of the catalytic performance. The surface morphology and crystal structure of used catalysts of either M1-TiO2-SM or M1-TiO2-PM remained stable as each fresh catalyst after 24 h time-on-stream tests.