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Co-based catalysts are promising alternatives to replace expensive Pt- and toxic Cr-based catalysts for propane dehydrogenation (PDH), while the catalytic stability and propylene selectivity have been subjected to the diversity of Co speciations. Given the situation, uniformly stable hydroxylated Co2+ silicate sites (depicted as {OH–Si–(OH)–Co–O–Si-(OH) 3 }) are successfully embedded into the silicalite-1 zeolite framework located in the straight and intersection channels (Co@S-1) with the assistance of Co precursors and geminal silanols via a facile hydrothermal synthesis, as revealed by detail characterizations. Under comparable conditions, a superior catalytic PDH performance with attractive propylene formation rate of 14.6 mmol·g cat −1·h−1, propylene selectivity higher than 93% and very low deactivation rate of 0.0206 h−1 after 7 h is achieved over the Co@S-1(EDA) catalyst. Furthermore, the catalytic performance can be restored to the same as that of the fresh catalyst after 3 successive regenerations. In situ FTIR spectra analysis further reveals the dynamic changes in the characteristic absorption bands associated with the hydroxylated Co2+ silicate sites and the intermediate product (2-propyl) during the PDH reaction and a reaction mechanism is proposed accordingly. This work provides a new insight for designing high-efficiency nonprecious metal PDH catalysts. [Display omitted] • Coordination environments of Co precursor complexes were precisely modulated. • Hydroxylated Co2+ silicate sites were fabricated with the assistance of Co precursors and geminal silanols. • Co@S-1(EDA) catalyst exhibited superior catalytic performance in PDH reaction. • A possible reaction mechanism was proposed from in situ FTIR spectra. [ABSTRACT FROM AUTHOR]

A highly stable bimetallic-sites catalyst of Ni-Zn anchored in the silicalite-1 zeolite framework is facilely fabricated by ligand-protected strategy, synergistically boosting propane dehydrogenation to propylene. [Display omitted] • Bimetallic Ni-Zn site anchored in the silicalite-1 zeolitic framework are fabricated. • Superior catalytic performance on the 0.2Ni0.06Zn-S-1 for PDH is achieved. • High stability and activity of catalyst are remained after regeneration for 4 cycles. • Synergistic effect between Ni-Zn sites favors propylene desorption to reduce coke deposition. Propane dehydrogenation (PDH) is a prospective benign process for the production of propylene, but generally depends on high-price Pt and toxic Cr(VI) catalysts that often suffer from the rapid deactivation derived from metal sintering and severe coke deposition. To overcome these problems, the breakthroughs in an alternative catalyst design with efficient, low-cost and eco-friendly play a crucial role in successfully developing this process. Here, we facilely fabricate the bimetallic-site catalyst of Ni-Zn anchored in the zeolitic framework of silicalite-1 (depicted as NiZn-S-1) by employing ligand-protected strategy, which performs high temperature stability. Under comparable conditions, the NiZn-S-1 catalyst with high Ni/Zn molar ratio of 3:1 (named 0.2Ni0.06Zn-S-1) exhibits superior catalytic activity (initial propane conversion of 32.5 % and actual TOF propane of 28.5 min−1) with low deactivation rate (0.0778 h−1) and great propylene selectivity (>90%) after 30 h on stream. In particular, the catalytic performance on this catalyst almost keeps same as that of fresh catalyst after 4 successive oxidation–reduction cycles. Multiple characterizations further demonstrate that the enhancement of PDH performance ought to be attributed to the synergistic effect between bimetallic Ni-Zn sites, which favors the selective activation of C–H bond and propylene desorption to reduce the formation of coke species with high graphitization degree, boosting the improvement of catalyst stability. The design of novel bimetallic-sites catalyst can give a new idea on the development of alternative PDH catalysts with economical- and environment-friendly in the future. [ABSTRACT FROM AUTHOR]

[Display omitted] • Coordination environments of Ni precursor complexes were precisely controlled. • Bifunctional Ni@S-1 catalysts developed from the evolution of hydroxylated Ni phyllosilicate. • Superb CO 2 -CH 4 reforming behavior benefited from the synergy of tailored metal–acid sites. • A benign balance between formation and elimination of "process carbon" species was established. Ni-based catalysts using siliceous materials as the supports have suffered from two challenging issues of sintering and carbon deposition for dry reforming of methane (DRM), resulted from a weak metal-support interaction. Given these, a novel metal–acid bifunctional Ni@S-1 zeolite catalyst is tailored from the evolution of hydroxylated nickel phyllosilicates that are formed by subtly controlling the coordination environments of Ni precursor complexes in the silicalite-1 (S-1) zeolite. The developed Ni 0.44 @S-1 catalyst renders almost equivalent CH 4 and CO 2 conversions (85.1 % and 88.7 %), high H 2 /CO molar ratio (about 1) and superb long-term stability during 100 h with no activity loss at 750 °C with a WHSV of 100 L·g cat −1·h−1, outperforming other control catalysts under investigation. Such superior catalytic behavior benefits from the synergy between highly uniform Ni nanoparticles (3–5 nm) confined in the micropores of zeolite and substantially formed Lewis acid sites due to coordinatively unsaturated Ni2+ sites located at the reduced 2:1 nickel phyllosilicate, as revealed by detailed characterizations. Meanwhile, it further discloses that a benign balance between formation and elimination of "process carbon" species is responsible for improving the carbon resistance of catalyst during the DRM reaction. The present design broadens a new insight for the development of new Ni-based catalysts with simultaneous coking- and sintering-resistant for the DRM application. [ABSTRACT FROM AUTHOR]

[Display omitted] • HZSM-5 zeolites cross-linked with ultrathin siliceous layer are fabricated. • Catalytic cracking performance of n-butane on the silanization zeolites are largely enhanced. • Diffusion properties of n-butane on the zeolites are quantified by in situ FTIR spectroscopy. • Correlation between n-butane conversion rate per Brønsted acid site and diffusivity is negative. • HZSM-5 with siliceous monolayer intensifies catalytic performance and diffusivity of n-butane. A series of HZSM-5 zeolites are fabricated to make it cross-link with an external ultrathin siliceous layer by chemical liquid deposition and the corresponding thickness is measured by TEM and XPS analysis. In situ FTIR experiments disclose that the external surface acidic sites of HZSM-5 zeolite can be covered even by siliceous monolayer (0.7 ∼ 1.3 nm, HZ5-S1). In comparison to parent HZSM-5, the catalytic cracking performance of n-butane over the modified zeolites are evidently enhanced. In particular, the n-butane conversion rate per Brønsted acid site over the HZ5-S2 (16.02 min−1) at 550 °C is 2.82 times than that over the HZSM-5 (5.68 min−1). Meanwhile, the diffusion properties of n-butane over the zeolites are quantified by in situ FTIR spectroscopic analysis. Negative correlation between steady-state diffusivity and n-butane conversion rate per Brønsted acid site can be found, which unravels the origin of the progressive decrease in the catalytic stability. Under comparable conditions, more advantages can be greatly achieved by HZ5-S1 catalyst in the catalytic activity and the yields to light olefins due to the benign diffusivity and the elimination of external surface acidic sites. This study can provide a guidance for the understanding of diffusion intensification and the rational design of superior catalyst for the catalytic cracking reactions of alkanes. [ABSTRACT FROM AUTHOR]

The long-term and efficient treatment of shale gas wastewater is an inevitable tendency. This study employed the SEP@Fe-Mn/RGO composite membrane series for the membrane separation treatment of shale gas wastewater. Different proportions and different function of SEP@Fe-Mn/RGO composite membranes were obtained through the method of electrostatic self-assembly. This study researched the "Trade-off" issue of membranes separation through the analysis，resulting in membranes that best meets the separation requirements for shale gas wastewater. After two membrane separation, The oil-water separation efficiency (COD 2040 mg/L and TOC 487.14 mg/L) of shale gas wastewater was >99.3 %. The removal rate of the main salt component (Na 2 SO 4) reached 83.56 %, and the removal rate of major heavy metal ions (Fe3+, Cr3+, Ba2+) was above 60 %. Because of the continuous generation of in-situ bubbles by the reaction of MnO 2 with H 2 O 2 , and Fenton reactions on the membrane, which further accelerated the separation of pollutants. In a variety of harsh water environments, this membrane series remained stable within 12 h. Simple to prepare, cost-effective, low in energy consumption, and environmentally friendly, which makes it promising for wide applications in the field of petroleum water treatment. • Composite membranes with different functions were synthesized in a simple and economical way. • Through the experiment to established the oil-water separation model, explore the best proportion of the composite membrane to solve the "Trade-off" • After two membrane separations, all kinds of water pollution in shale gas wastewater can be effectively separated. [ABSTRACT FROM AUTHOR]

Three zeolites ZSM-5, ZSM-35 and ZSM-22 are applied in n -butane cracking to reveal the influence of regional differences in Brønsted acid sites on reaction pathways. The Brønsted acid sites located in the channels of ZSM-5 exhibit a higher catalytic activity and yields to light olefins (especially the ethylene), which can be attributed to more relative contribution of bimolecular pathway. In comparison, more Brønsted acid sites are situated on the external surface or micropore mouths of ZSM-35 and ZSM-22, which are beneficial to propylene production. Note-worthily, almost no propane production on the two zeolites implies the predomination of monomolecular pathway. In situ FTIR technique further discloses that the difference in the reaction pathways is tailored by adsorption configurations of n -butane at two types of Brønsted acid sites. Under comparable conditions, the ZSM-5 performs a relatively good catalytic stability through bimolecular pathway. Furthermore, the correlation between deactivation rate and light olefins reveals that the enhancement of propylene selectivity accelerates the deactivation of ZSM-35 and ZSM-22. While, promotion on the ethylene selectivity is a significant inducement for the deactivation of ZSM-5. Reaction pathways of n-butane cracking tailored by the influence of regional differences in Brønsted acid sites. [Display omitted] • Three typical 10-member ring zeolites ZSM-5, ZSM-35 and ZSM-22 are prepared. • Reaction pathways of n -butane cracking over the zeolites are investigated. • Regional differences in Brønsted acid sites tailor the selectivities to propylene and ethylene. • ZSM-5 zeolite exhibits high catalytic activity and stability compared to ZSM-35 and ZSM-22. • Catalyst deactivation mechanisms are revealed on different reaction pathways. [ABSTRACT FROM AUTHOR]