High-silica zeolite Y (SiO2/Al2O3 = 20.4) was synthesized in high yield (ca. 60%) via a top-down strategy using TBAOH and TMAOH as organic structure-directing agents, yielding nanocrystals (50-100 nm) with ultralow Na content (Na/Al = 0.02) and homogenous framework Al distribution that demonstrated enhanced catatytic performance for dimethoxymethane carbonylation.

n-Butane dehydrogenation (BDH) provides an on-purpose route to produce 1,3-BD. However, design of highly active and selective catalysts targeting BDH to 1,3-BD remains challenging because the activation barrier for the dehydrogenation of 1-butene (a primary product of BDH) is high and 1-butene readily isomerizes. Here, we report a bimetallic Co-O-Zn active site with the structure of ≡SiO-Co-O-Zn-OSi≡ prepared by reacting Co ions with ≡SiOZn-OH nests on dealuminated zeolite BEA (DeAlBEA), showing 3- and 34-fold activity advantages over monometallic Co and Zn counterparts, respectively. Co-O-Zn sites exhibit a high BDH rate of 354 mol·molCo-1·h-1 and a 1,3-BD productivity of 110 mol·molCo-1·h-1 (and selectivity to 1,3-BD of 31%) at 823 K. The forward rate coefficient for BDH is superior to state-of-the-art non-noble-metal catalysts and comparable to Pt-based catalysts. A kinetics investigation suggests that the Co-O-Zn interactions promote n-butane adsorption and activation of the C-H bond during both BDH and 1-butene dehydrogenation. Our work demonstrates a promising pathway for producing 1,3-BD via BDH using a catalyst that is free of expensive noble metals.

Ethanol dehydrogenation process contributes significantly to the ethanol-based chemical industry which is expected to grow up in the forthcoming future. Cu-based catalysts are highly active for this process, while the poor stability of which limits its practical application. Encapsulating Cu species into zeolites exhibits great potential in creating and stabilizing Cu nanoparticles. The present investigation reports the synthesis of Cu@Silicalite-1 (Cu@S-1) catalysts with high Cu loading up to 10 wt% and finely distributed nanoparticles of 2.5-5 nm by a modified steam-assisted strategy. Cu@S-1 presents robust and stable catalytic performance for the dehydrogenation of ethanol to acetaldehyde, remarkably superior to Cu/SiO2. No aggregation of Cu species could be observed after three cycles of harsh reaction-oxidative regeneration-reductive activation or long-term reaction. Kinetic investigation reveals that the rates of ethanol dehydrogenation exhibit a Langmuir dependence on ethanol partial pressure. The rate coefficient for rate-limiting C-H cleavage over Cu@S-1 is about 2.4 times higher than that over Cu/SiO2 at 523 K, in consistency with its superior dehydrogenation performance. Furthermore, Cu@S-1 possesses lower apparent activation energy and ethanol adsorption enthalpy compared with Cu/SiO2. In situ infrared and X-ray photoelectron spectroscopy investigation prove that the Cu@S-1 catalyst with rich amount of Cu+ is kinetically favorable for ethanol dehydrogenation.

An eco-friendly and cost-effective approach for the fast synthesis of SSZ-13 with tunable Al distribution has been developed by utilizing coal gangue as an inorganic source under the assistance of embryonic CHA zeolite. The proportion of Al species with close spatial proximity (Alpairs and Alclose) in SSZ-13 can reach as high as 73 %. The Al pairs-enriched Cu/SSZ-13 (named Cu/GS6) facilitates the formation of hydrothermally stable Cu2+-2Z species and shows a broad NH3-SCR working temperature window (T90: 175-600 degrees C, GHSV = 300,000 h-1) and robust resistance to hydrothermal aging at 800 degrees C. Both framework Al distribution and structural integrity are demonstrated to be key factors determining the catalytic activity and hydrothermal stability of Cu/SSZ-13. The (Alpairs and Alclose) species are more efficient than isolated Al species for the migration of active Cu species, contributing to the superior low-temperature activity of Cu/GS6. Moreover, it is revealed that structural defects in zeolites lead to aggravated framework dealumination during Cu-based catalyst preparation and hydrothermal aging, which should be minimized to enhance the catalyst stability. The efficient utilization of industrial solid waste for controllable synthesis of SSZ-13 and the insights into the synthesis-property-performance relationships are expected to prompt the development of high-performance NH3-SCR catalysts and their application.

Zeolite-confined Rh-based catalysts have emerged as promising heterogeneous candidates for olefin hydroformylation. However, they face challenges of reactant- and product-induced Rh leaching and aggregation. Herein, zeolite framework-anchored Rhδ+-(O-Zn)x sites were designed and are shown to have remarkable activity and stability for gas-phase ethylene hydroformylation. The bimetallic catalysts were synthesized by coencapsulating Rh and Zn species into Silicalite-1 zeolite, and the Rhδ+-(O-Zn)x sites were in situ constructed during the induction period of the hydroformylation process through the interaction between mobile Rh-carbonyl species and framework ≡SiOZn-O(H). The change of the Zn/Rh molar ratio significantly affects the dispersion of Rh and the proportion of highly active Rhδ+. The optimal 0.2Rh@Zn3-S-1 catalyst achieves a propanal turnover frequency as high as 148 h-1 at 363 K and shows no sign of deactivation during the 40 h test. In contrast, zinc-free 0.2Rh@S-1 suffers rapid deactivation due to Rh aggregation. In situ Fourier transform infrared (FTIR) spectroscopy reveals that the transfer desorption of propanal from Rh to Zn-O contributes to the redispersion of Rh during the construction of Rhδ+-(O-Zn)x structures. Moreover, the observed HRh(CO)2 species together with the enrichment of Rhδ+-propionyl intermediates on the catalyst indicates that the hydrogenation of acyl species is the rate-limiting step of ethylene hydroformylation, which is further supported by kinetic analysis. This study presents a new strategy for designing stable and efficient gas-phase ethylene hydroformylation catalysts using zeolite-anchored metal species as inorganic ligands for Rhδ+ centers and provides insights into the hydroformylation mechanism occurring on the bimetallic sites.

Low-carbon process for resource utilization of polycyclic aromatic hydrocarbons(PAHs)in zeolite-catalyzed processes,geared to carbon neutrality-a prominent trend throughout human activities,has been bottlenecked by the lack of a complete mechanistic understanding of coking and decoking chem-istry,involving the speciation and molecular evolution of PAHs,the plethora of which causes catalyst deactivation and forces regeneration,rendering significant CO2 emission.Herein,by exploiting the high-resolution matrix-assisted laser desorption/ionization Fourier-transform ion cyclotron resonance mass spectrometry(MALDI FT-ICR MS),we unveil the missing fingerprints of the mechanistic pathways for both formation and decomposition of cross-linked cage-passing PAHs for SAPO-34-catalyzed,indus-trially relevant methanol-to-olefins(MTO)as a model reaction.Notable is the molecule-resolved sym-metrical signature:their speciation originates exclusively from the direct coupling of in-cage hydrocarbon pool(HCP)species,whereas water-promoted decomposition of cage-passing PAHs initiates with selective cracking of inter-cage local structures at 8-rings followed by deep aromatic steam reform-ing.Molecular deciphering the reversibly dynamic evolution trajectory(fate)of full-spectrum aromatic hydrocarbons and fulfilling the real-time quantitative carbon resource footprints advance the fundamen-tal knowledge of deactivation and regeneration phenomena(decay and recovery motifs of autocatalysis)and disclose the underlying mechanisms of especially the chemistry of coking and decoking in zeolite catalysis.The positive yet divergent roles of water in these two processes are disentangled.These unprecedented insights ultimately lead us to a steam regeneration strategy with valuable CO and H2 as main products,negligible CO2 emission in steam reforming and full catalyst activity recovery,which further proves feasible in other important chemical processes,promising to be a sustainable and potent approach that contributes to carbon-neutral chemical industry.

Zeolite-encapsulated metal nanoclusters are at the heart of bifunctional catalysts, which hold great potential for petrochemical conversion and the emerging sustainable biorefineries. Nevertheless, efficient encapsulation of metal nanoclusters into a high-silica zeolite Y in particular with good structural integrity still remains a significant challenge. Herein, we have constructed Ru nanoclusters (-1 nm) encapsulated inside a high-silica zeolite Y (SY) with a SiO2/Al2O3 ratio (SAR) of 10 via a cooperative strategy for direct zeolite synthesis and a consecutive impregnation for metal encapsulation. Compared with the benchmark Ru/H-USY and other analogues, the as-prepared Ru/H-SY markedly boosts the yields of pentanoic biofuels and stability in the direct hydrodeoxygenation of biomass-derived levulinate even at a mild temperature of 180 degrees C, which are attributed to the notable stabilization of transition states by the enhanced acid accessibility and properly sized constraints of zeolite cavities owing to the good structural integrity.(c) 2023 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by ELSEVIER B.V. and Science Press. All rights reserved.

The applications of nanoporous crystalline materials are closely related to the mass transfer of guest molecules. However, the fundamental knowledge of mass transfer, and in particular the surface barriers controlled by the permeation of guest molecules through the external surfaces of materials, is still incomplete. The diversity of surface permeability at the single-crystal level, caused by the varying origins of surface transport resistance, hinders the rational materials design and needs better understanding. Herein, we probe the molecular transport in single zeolite crystals with fluorescent 4-(4-diethylaminostyryl-1-methylpyridinium iodide) (DAMPI) using super-resolution structured illumination microscopy (SIM). It showed that both the inter- and intra-crystal diversity of surface barriers could be monitored by detecting the diffusion behaviors on the center and surface planes in single crystals. This adds a new perspective for studying the origins of the surface barriers as well as the molecular transport mechanisms in nanoporous materials.

An efficient and long-term stable nano-sized N-H-ZSM-5 zeolite catalyst for the one-step aldol condensation reaction of formaldehyde and MAc to produce MA and AA is reported. Its total lifetime reaches up to 226 h by three regeneration runs.

Mesoporous high-silica zeolite Y with advantages of improved accessibility of acid sites and mass transport properties is highly desired catalytic materials for oil refinery, fine chemistry and emerging biorefinery. Here, we report the direct synthesis of mesoporous high-silica zeolite Y (named MSY, SiO2/Al2O3 ≥ 9.8) and their excellent catalytic cracking performance. The obtained MSY materials are mesoporous single crystals with octahedral morphology, abundant mesoporosity and excellent (hydro)thermal stability. Both the acid concentration and acid strength of H-form MSY are obviously higher than those of commercial ultra-stable Y (USY), which should be attributed to the uniform Al distribution of MSY zeolite. The H-MSY displays an obviously reduced deactivation rate and improved catalytic activity in the cracking reaction of bulky 1,3,5-triisopropylbenzene (TIPB), as compared with its mesoporogen-free counterpart and USY. In addition, H-MSY was investigated as catalyst for the cracking of industrial heavy oil. The MSY-based catalyst (after aging at 800 oC in 100% steam for 17 h) exhibits superior conversion (7.64% increase) and gasoline yield (16.37% increase) than industrial fluid catalytic cracking (FCC) catalyst under the investigated conditions.

The synthesis and catalytic performances of ZSM-48 were summarized. ZSM-48 was mainly applied in cracking reactions, shape selective reaction, methanol to hydrocarbons and showed excellent catalytic performance in hydroisomerization reaction.

The dynamic evolution of Al species in the hydrothermal dealumination process of CHA zeolite was investigated by multiple solid-state NMR methods. Two types of Al–OH species were clearly distinguished by 1 H– 1 H DQ-SQ MAS NMR.

Transport resistance in microporous zeolites has an important impact on their applications in catalysis. Relative to the well-known intracrystalline transport resistance, the significance of surface barriers on the catalytic performance of zeolites has not been well recognized. Herein, we report that the DME carbonylation reaction can be governed by surface barriers on zeolites, affecting both the catalyst activity and stability. The two MOR zeolites used for the investigation were synthesized by different organic structure-directing agents (OSDAs). They possess similar Si/Al ratios, diffusion lengths, Al distributions, and acidities but quite different diffusion properties. The MOR-C sample with severe transport limitations exhibits inferior apparent activity (similar to 50% lower) and poor stability in comparison compared with the MOR-T sample. Chemical etching of the outer layer of as-made MOR-C crystals has been proven to be an effective strategy to reduce surface barriers, enhance mass transport properties, and improve the activity and stability of the MOR catalyst. The carbonylation activity of etched MOR-C is indeed comparable to that of MOR-T. This work highlights the importance of controlling the synthetic strategy and surface barriers on zeolite crystals for the design/development of highly efficient catalysts.

Seed-assisted synthesis of high-silica zeolite Y with good (hydro)thermal stability, abundant strong acid sites and excellent catalytic cracking performance.

Given the increase in global carbon emissions, efficiently converting syngas into one single C2+ hydrocarbon product with low CO2 selectivity is important but still challenging. Herein, we report a dual-bed catalyst system, which can highly convert syngas into propane with lower CO2 emissions. Propane in hydrocarbon products can reach 79% at CO conversion of 96% with 12% CO2 selectivity. The selectivity of methane is lower than 6% at the same time. Furthermore, up to 66% propane yield is achieved, which can significantly increase the efficiency of carbon utilization compared with traditional methods. The catalytic performance of the dual-bed reaction system also exhibits an excellent stability during the 200 h test on stream. The dual-bed reaction system is configured with a syngas-to-dimethyl ether (DME) CuZnAlOx + ZSM-5 catalyst in the upper bed and a DME-to-propane SSZ-13 zeolite catalyst in the lower bed. The higher strength of the acid sites for SSZ-13 benefits the formation of propane and helps to limit the coke deposition. Probing experiments and DFT calculations imply that syngas-to-propane reaction includes methanol-to-olefin processes and subsequent conversion of lower olefins in high-pressure H2. The generated intermediate propylene hydrogenation over SSZ-13 leads to a high propane selectivity. This strategy offers a scenario to promote the syngas-to-hydrocarbon performance with low CO2 emissions.

A low-pressure SiCl4 treatment (LPST) strategy to selectively relocate zeolite framework aluminum atoms into the desired positions is reported in the Research Article by Zhengxi Yu, Zhongmin Liu, and co-workers (e202116990). After treatment, the undesired framework aluminum atoms in the 12-MR channels of a mordenite zeolite migrate to the desired T3 sites to increase the number of favorable active sites.

High-silica zeolite Y (FAU) plays a vital role in (petro)chemical industries. However, the slow nucleation and growth kinetics of the high-silica FAU framework limit its direct synthesis and the improvement of framework SiO 2 /Al 2 O 3 ratio (SAR). Here, a facile strategy is developed to realize the fast crystallization of high-silica zeolite Y, which involves the combination of high crystallization temperature, ultra-stable Y (USY) seeds and efficient organic-structure directing agent (OSDA). The synthesis can be finished in 5–16 h at 160 °C and with tunable SAR up to 18.2, and the key factors affecting crystallization kinetics and phase purity are elucidated. Moreover, the crystallization process was monitored to reveal the fast crystal growth mechanism. The high-silica products possess high (hydro)thermal stability and abundant strong acid sites, which endow them excellent catalytic cracking performance, obviously superior to commercial USY.

Controlling the location of aluminum atoms in a zeolite framework is critical for understanding structure–performance relationships of catalytic reaction systems and tailoring catalyst design. Herein, we report a strategy to preferentially relocate mordenite (MOR) framework Al atoms into the desired T 3 sites by low-pressure SiCl 4 treatment (LPST). High-field 27 Al NMR was used to identify the exact location of framework Al for the MOR samples. The results indicate that 73 % of the framework Al atoms were at the T 3 sites after LPST under optimal conditions, which leads to controllably generating and intensifying active sites in MOR zeolite for the dimethyl ether (DME) carbonylation reaction with higher methyl acetate (MA) selectivity and much longer lifetime (25 times). Further research reveals that the Al relocation mechanism involves simultaneous extraction, migration, and reinsertion of Al atoms from and into the parent MOR framework. This unique method is potentially applicable to other zeolites to control Al location.

Na+-free Cu-SSZ-13 zeolites have been rationally synthesized via a cooperative strategy, which has the advantages of rapid crystallization (9-48 h), high yield (86-94%) and adjustable Cu content. The NH3-SCR catalytic performance and hydrothermal stability of the calcined materials were studied and correlated with their physicochemical properties.