Search

The utilization of methane for chemical production, often considered as the future of petrochemistry, historically could not compete economically with conventional processes due to higher investment costs. Achieving sustainability and decarbonization of the downstream industry by integration with a methane-to-chemicals process may provide an opportunity to unlock the future for these technologies. Gas-to-chemicals is an efficient tool to boost the decarbonization potential of renewable energy. While the current implementation of carbon capture utilization and storage (CCUS) technologies is of great importance for industrial decarbonization, a shift to greener CO2-free processes and CO2 utilization from external sources for manufacturing valuable goods is highly preferred. This review outlines potential options for how a methane-to-chemicals process could support decarbonization of the downstream industry. [ABSTRACT FROM AUTHOR]

The utilization of methane for chemical production, often considered as the future of petrochemistry, historically could not compete economically with conventional processes due to higher investment costs. Achieving sustainability and decarbonization of the downstream industry by integration with a methane-to-chemicals process may provide an opportunity to unlock the future for these technologies. Gas-to-chemicals is an efficient tool to boost the decarbonization potential of renewable energy. While the current implementation of carbon capture utilization and storage (CCUS) technologies is of great importance for industrial decarbonization, a shift to greener CO2-free processes and CO2 utilization from external sources for manufacturing valuable goods is highly preferred. This review outlines potential options for how a methane-to-chemicals process could support decarbonization of the downstream industry. [ABSTRACT FROM AUTHOR]

Hierarchical zeolites presenting different pore domains have the potential to reduce problems associated with low diffusion in zeolites, thus holding great promise in a wide range of application fields. Nevertheless, efficient transfer between the different porous networks is required for the mesopores (2–50 nm) and macropores (>50 nm) to be effective in promoting the transit of molecules towards the micropores (<2 nm). In this work, the connectivity between the various pore domains in a class of hierarchical zeolites – denominated as nanoparticle aggregates – is investigated through 2D exchange spectroscopy (EXSY) 1H nuclear magnetic resonance (NMR) using paraxylene as a probe molecule. This approach allows to track whether the probe molecule visits distinct pore environments over time, providing unique insight into pore connectivity. The analysis of scanning curves through N 2 adsorption/desorption cycles completes the characterization of pore connectivity. Furthermore, electron microscopy and tomography are used as visual techniques to confirm the arrangement of the mesoporous and macroporous networks generated by the nanoparticle aggregates. • Hierarchical zeolites are analyzed using a broad spectrum of experimental methods • 2D exchange NMR is used to gain insight into pore connectivity • Scanning N 2 adsorption is combined with electron microscopy and tomography. [ABSTRACT FROM AUTHOR]

Zeolites have been game-changing materials in oil refining and petrochemistry over the last 60 years and have the potential to play the same role in the emerging processes of the energy and environmental transition. Although zeolites are crystalline inorganic solids, their structures are not perfect and the presence of defect sites – mainly Brønsted acid sites and silanols – influences their thermal and chemical resistance as well as their performances in key areas such as catalysis, gas and liquid separations and ion-exchange. In this paper, we review the type of defects in zeolites and the characterization techniques used for their identification and quantification with the focus on diffraction, spectroscopic and modeling approaches. More specifically, throughout the review, we will focus on silanol (Si–OH) defects located within the micropore structure and/or on the external surface of zeolites. The main approaches applied to engineer and heal defects and their consequences on the properties and applications of zeolites in catalysis and separation processes are highlighted. Finally, the challenges and opportunities of silanol defect engineering in tuning the properties of zeolites to meet the requirements for specific applications are presented. [ABSTRACT FROM AUTHOR]

Conventional and hierarchical faujasite zeolites, which are relevant to xylene separation by adsorption processes, are characterized using a broad set of complementary experimental techniques. In addition to a conventional faujasite zeolite, hierarchical faujasite zeolites consisting either of nanoparticle aggregates or of a layer-like zeolite are considered. For all samples, both the sodium and barium forms of these X zeolites are investigated. With the goal to predict and rationalize the efficiency of these materials for a given application, the fine characterization reported here aims at identifying key parameters such as their multiscale pore size distribution, pore connectivity/morphology, and external surface physical chemistry. X-ray diffraction is first used to probe the different crystalline phases and domain sizes coexisting in each sample. Electron microscopy at different scales (scanning and transmission microscopies) is also used to determine the morphology of the different porosity domains as well as to investigate the core-shell structure of the samples. N 2 adsorption and mercury intrusion are then combined to provide a consolidated multiscale pore size distribution of each sample. Furthermore, adsorption scanning curves are determined to analyze the topology/connectivity of the porosity domains. Finally, infrared spectroscopy and nuclear magnetic resonance are used to assess the chemistry of the samples with special focus on their external surface. The combination of these different techniques is found to provide a rich and detailed picture of these heterogeneous and multiscale solids that goes beyond standard routine characterization. Image 1 • Invasive and non-invasive techniques are used to characterize hierarchical zeolites. • Adsorption and porosimetry provide multiscale pore size distribution and connectivity. • Simple scaling is found between silanol groups and external surface area. • Particle texture is unraveled by coupling adsorption/diffraction/electron microscopy. [ABSTRACT FROM AUTHOR]

Natural gas will play a significant role in the transition from fossil to green(er) energy production. Its major component, methane (CH 4) is an attractive resource to co-generate hydrogen (H 2) and added value chemicals (important building blocks such as olefins and aromatics) for petrochemistry. We highlight the advantage of using a novel dual catalyst system containing a monofunctional Al-free metallic single site catalyst referred as S-Mo (Si/Al ∼ ∝) where Mo is atomically dispersed in the zeolitic framework and a monofunctional acidic H-ZSM-5 catalyst referred as S-Al (SiAl = 128) to achieve superior yields of high value products. Under severe reaction (850 ºC) and regeneration (700 ºC) conditions, the Mo-S catalyst is stable and does not suffer from irreversible structural damage by losing its Mo atomic dispersion, and deactivation by coke deposition, thus ensuring steady catalytic performances in multi-cycle catalytic tests. Conversely, the current bifunctional catalysts prepared by Mo impregnation on an acidic catalyst suffer from irreversible damage during coke combustion due to the formation of Al₂(MoO₄)₃ or AlMoO 6 Anderson entities. This new approach opens novel and promising pathways to develop methane upgrading processes based on the physical separation and operation of a non-deactivating metallic catalyst and a regenerable acidic catalyst. [Display omitted] • Catalytic systems involving single site Mo-MFI lead to a stable methane conversion and hydrocarbons production. • Best MDA performances are obtained with a dual bed configuration of two monofunctional single sites Mo-MFI and HZSM-5 catalysts. • The single site Mo-MFI in dual bed configuration displays no coke formation and a high thermal and hydrothermal stability. • Dual bed configuration allows managing separately the reactional temperature of both layers to find the best balance between activity and coke formation. [ABSTRACT FROM AUTHOR]

Still, the challenging questions are how to control hydroxyls in zeolites using different synthesis methodologies and how to identify them and relate them to the reactivity of zeolites. Optimizing the combination of alkali metal cations and organic cationic SDAs for obtaining new zeolites will be crucial for controlling the Al site distribution and performance of new zeolite catalysts by controlling the bridged hydroxyls. The ideal crystalline framework of zeolites is perturbed by hydroxyl groups. [Extracted from the article]