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Direct and selective production of C 3+ olefins from bioethanol remains a critical challenge and important for the production of renewable transportation fuels such as aviation biofuels. Here, we report a Cu−Zn−Y/Beta catalyst for selective ethanol conversion to butene-rich C 3+ olefins (88% selectivity at 100% ethanol conversion, 623 K), where the Cu, Zn, and Y sites are all highly dispersed. The ethanol-to-butene reaction network includes ethanol dehydrogenation, aldol condensation to crotonaldehyde, and hydrogenation to butyraldehyde, followed by further hydrogenation and dehydration reactions to form butenes. Cu sites play a critical role in promoting hydrogenation of the crotonaldehyde CC bond to form butyraldehyde in the presence of hydrogen, making this a distinctive pathway from crotyl alcohol-based ethanol-to-butadiene reaction. Reaction rate measurements in the presence of ethanol and acetaldehyde (543 K, 12 kPa ethanol, 1.2 kPa acetaldehyde, 101.9 kPa H 2 ) over monometallic Zn/ Beta and Y/Beta catalysts indicate that Y sites have higher C−C coupling rates than over Zn sites (initial C−C coupling rate, 6.1 × 10 −3 mol mol Y −1 s −1 vs 1.2 × 10 −3 mol mol Zn −1 s −1 ). Further, Lewis-acidic Y-site densities over Cu−Zn−Y/Beta with varied Y loadings are linearly correlated with the initial C−C coupling rates, suggesting that Lewis-acidic Y sites are the predominant sites that catalyze C−C coupling in Cu−Zn−Y/Beta catalysts. Control experiments show that the dealuminated Beta support is important to form higher density of Lewis-acidic Y sites in comparison with other supports such as silica, or deboronated MWW despite similar atomic dispersion of Y sites and Y−O coordination numbers over these supports, leading to more than 9 times higher C−C coupling rate per mole Y over dealuminated Beta relative to other supports. This study highlights the significance of unique combination of metal sites in contributing to the selective valorization of ethanol to C 3+ olefins, motivating for exploring multifunctional zeolite catalysts, where the presence of multiple sites with varying reactivities and functions allows for controlling the predominant molecular fluxes toward the desired products in complex reactions.

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the ability to produce a substantial fraction of "stranded," or uneconomic, natural gas resources. [1] Furthermore, low value gases, such as CH 4 , are often flared or vented at remote oil production sites. Stranded, flared, and/or vented gases cause environmental harms, and represent losses of energy and economic opportunities. Therefore, transformative CH 4 conversion technology is required to upgrade CH 4 to value-added chemicals and fuels to eliminate environmental emissions, and to increase energy source utilization and economic growth.Current state-of-the-art CH 4 upgrading process is based on Fischer-Trøpsch (FT) conversion of syngas (a mixture of carbon monoxide (CO) and H 2 ). [2][3][4][5] Process steps include an air separation unit, gasification, or steam methane reforming (SMR) to make syngas, followed by FT synthesis of higher hydrocarbons. Multiple process steps, large-scale operation, and high capital cost are characteristics of this technology, which is not cost competitive to deploy for stranded or smaller, distributed gas fields. [2,6,7] Conversion of CH 4 to ethylene (C 2 H 4 ) through the oxidative coupling of methane (OCM) is promising for direct one-step methane upgrading, but this process suffers from constrained C 2 H 4 yield and substantial waste as large amounts of CH 4 feed leaves the system as fully or partially oxidized carbon species (CO and carbon dioxide (CO 2 ), i.e., CO x ). [8][9][10][11][12] Direct nonoxidative methane conversion (DNMC) is another potential process for one-step CH 4 upgrading to C 2 (acetylene (C 2 H 2 ), C 2 H 4 and ethane (C 2 H 6 )) hydrocarbons and aromatics (e.g., benzene, toluene, and naphthalene), with coproduction of H 2 . [6,[13][14][15][16][17][18] This process is much simpler than the syngas one, which means lower investment costs, and high potential for widespread deployment for diverse natural gas sources. [2,6,7] DNMC over conventional metal/zeolite catalysts typically occurs at temperature below 1023 K due to the instability of catalyst structures. Unfortunately, the commercialization of DNMC is constrained by low CH 4 equilibrium conversion (≈16% at 1023 K) and high rate of catalyst deactivation due to carbon deposition. [14,[19][20][21][22] Additionally, the DNMC reaction is highly endothermic, and heat supply becomes a technical challenge.Research efforts have focused on the development of membrane reactors comprised of DNMC activation catalysts Direct nonoxidative methane conversion (DNMC) transforms CH 4 to higher (C 2+ ) hydrocarbons and H 2 in a single step, but its utility is challenged by low CH 4 equilibrium conversion, carbon deposition (coking), and its endothermic reaction energy requirement. This work reports a heat-exchanged autothermal H 2 -permeable tubular membrane reactor composed of a thin mixed ionicelectronic conducting SrCe 0.7 Zr 0.2 Eu 0.1 O 3-δ membrane supported on a porous SrCe 0.8 Zr 0.2 O 3-δ tube in which a Fe/SiO 2 DNMC catalyst is packed, that concurrently tackles all of these challenges. The H 2 -permeation flux ...