To achieve palm oil conversion along with a high yield of long-chain alkane, a series of NiFe layered double oxide catalysts were prepared and employed in the deoxygenation of palm oil. The layered structure of these catalysts was confirmed by XRD and SEM analyses, and Ni and Fe species existed primarily in the forms of Ni2+ and Fe3+, respectively. It was found that Ni/Fe molar ratio influenced the H2 reducibility and surface properties of NiFe catalysts. Specifically, Ni2Fe-LDO and Ni3Fe-LDO exhibited higher reducibility under H2 atmosphere. Moreover, the Ni2Fe-LDO catalyst contained a higher concentration of surface oxygen species (Osurf). Deoxygenation results demonstrated that the Ni2Fe-LDO catalyst achieved superior palm oil conversion, higher liquid product yield and enhanced selectivity toward C15-C18 hydrocarbons compared to other catalysts. This improved performance was attributed to its higher hydrogen dissociation activity and enhanced adsorption capacity for palm oil molecules. Furthermore, reaction condition studies revealed that palm oil was completely converted, yielding 86.8% liquid product with 81.8% selectivity of C15-C18 hydrocarbons at 350 degrees C under 7 MPa H2 pressure. This finding provides an insight into the development of efficient catalysts for the deoxygenation of fatty compounds to biofuels.

Adsorptive separation, which relies on the size, polarity, and affinity of guest molecules, is an efficient, eco-friendly, and cost-effective method. Zeolite-based adsorbents, known for their uniform pore size and regenerability, have exhibited exceptional performance in many challenging adsorption processes, such as the separation of n-paraffin/i-paraffin and xylene isomers. Ion exchange, as an essential piece in the fabrication of zeolite-based adsorbents, significantly affects overall performance. In this review, we survey the recent key developments and issues within ion exchange research of zeolite-based adsorbents, including the solution pH, solution concentration, ion-exchange cycles, ion-exchange temperature, ion-exchange time, calcination temperature, and discuss the mechanisms of their influence on zeolite adsorption. This review also elaborates on the negative effects of improper ion exchange on incomplete cation exchange, cation migration, collapse of the zeolite structure, and blockage of zeolite pores. Other parameters that lack research but have been proven to affect ion exchange are also mentioned. We hope to generate interest in the wider community and encourage others to make use of ion exchange in tackling challenges of adsorption separation science and engineering.

Hierarchical SAPO-11, featuring both micropore and mesopore channels, demonstrates an outstanding performance in high-octane gasoline production. In this work, we propose an economic and effective approach to directly fabricate hierarchical SAPO-11 molecular sieve from natural kaolin, eliminating the need for mesoporogens. The systematic characterization results show that the kaolin-derived SAPO-11 possesses abundant micro-mesoporous structure and more Brønsted (B) acid sites on the external surface in contrast with the conventional SAPO-11 prepared employing silica sol as silicon source as well as SAPO-11 synthesized with the assist with of poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (F127). The analysis of the formation process reveals that the kaolin not only provides silicon source for the SAPO-11 crystal growth, but also offers confined environment for crystal growth along the preferential orientation, resulting in the generation of the microporous and mesoporous structure. Benefiting from these unique properties, the kaolin-derived Pt/SAPO-11 exhibits considerably improved selectivity for di-branched C8 isomers in n-octane hydroisomerization.

The SO2 poisoning of a heterobimetallic FeCu-SSZ-13 in selective catalytic reduction of NO with NH3 (NH3-SCR) was systematically investigated in this study. It was shown that when SO2 is involved in the feeding flue gas, the losses in the redox ability of active metals (primary contributor to deactivation) and in the number of Bronsted acid sites both inhibit the formation of NH4NO2 intermediate, resulting in the rapid deactivation of FeCu-SSZ-13. The SO2 poisoning of FeCu-SSZ-13 at low temperature is more serious than at high temperature, because of the more severe loss of redox ability of active metals. Unlike that of monometallic Cu-/Fe-CHA, the SO(2 )poisoning of the bimetallic one is saliently featured by that partial SO2 is oxidized to SO3 and partial Bronsted acid sites are destroyed due to the formation of H2SO4. This work may provide a fundamental understanding on the SO2 poisoning of heterobimetallic zeolite-based NH3-SCR catalysts.

The development of sustainable techniques to produce high-performance zeolite is essential to achieve green production in industry. Herein, we report an eco-friendly route to synthesizing hierarchical Beta zeolite from kaolinite and recycled mother liquor. The results reveal that the unutilized species (such as silicon species and Na+) in mother liquor stayed in a stable concentration during eleven recycled experiments. Moreover, the synthesized Beta zeolites still have comparable physicochemical properties and catalytic performance in the esterification of levulinic acid with ethanol over the initial zeolite although eleven recycled experiments. Life cycle assessment exhibits that the synthesis of Beta zeolite with recycled mother liquor can reduce global warming potential by 23% and resource depletion-water use by 36% compared to that without recycled mother liquor. This quantitatively demonstrates that the approach proposed in this work is really a sustainable one, extremely increasing the utilization efficiency of raw materials and decreasing the environmental burden.

Zeolite catalysts have found extensive applications in the synthesis of various fine chemicals. However, the micropores of zeolites impose diffusion limitations on bulky molecules, greatly reducing the catalytic efficiency. Herein, we explore an economic and environmentally friendly method for synthesizing hierarchical NaX zeolite that exhibits improved catalytic performance in the Knoevenagel condensation reaction for producing the useful fine chemical 2-cyano-3-phenylacrylate. The synthesis was achieved via a low-temperature activation of kaolinite and subsequent in-situ transformation strategy without any template or seed. Systematic characterizations reveal that the synthesized NaX zeolite has both inter-crystalline and intra-crystalline mesopores, smaller crystal size, and larger external specific surface area compared to commercial NaX zeolite. Detailed mechanism investigations show that the inter-crystalline mesopores are generated by stacking smaller crystals formed from in-situ crystallization of the depolymerized kaolinite, and the intra-crystalline mesopores are inherited from the pores in the depolymerized kaolinite. This synthesis strategy provides an energy-saving and effective way to construct hierarchical zeolites, which may gain wide applications in fine chemical manufacturing.

Designing a cost-effective and fast fabrication Cu-SSZ-13 with improved selective catalytic reduction of NO by ammonia (NH3-SCR) performance remains an open question. Here we report that LaCe-SSZ-13 zeolites were synthesized from spent fluid catalytic cracking catalyst within 12 h. After ion-exchanging with CuSO4 solution, the obtained LaCeCu-SSZ-13 catalysts exhibit significantly higher catalytic activity and hydrothermal stability than conventional Cu-SSZ-13. Various characterizations reveal that La and Ce modification not only facilitates the disperse of isolated Cu2+ species, but also effectively mitigates dealumination and inhibits copper species aggregation after hydrothermal aging. In-situ diffuse reflection infrared Fourier transform spectrum analyses demonstrate that La and Ce modification can accelerate the adsorption capacity for NH3 and NOx and promote the decomposition of NH4NO3 intermediate species on the catalyst, benefiting the improvement of low-temperature activity. The combination of experiments and theoretical calculations further demonstrate that the most stable positions of La and Ce are on different eight-membered rings in SSZ-13, and then Cu2+ ions tend to enter eight-membered rings to enhance the NH3 adsorption capacity and decrease the H2O adsorption capacity, which results in higher low-temperature activity and hydrothermal stability than Cu-SSZ-13. Our work provides a feasible strategy for preparing the efficient rare-earth-modified Cu-zeolite based NH3-SCR catalyst for nitrogen oxide abatement.

Platinum nanoparticles (Pt NPs) embedded in the multi-hollow silicalite-1 zeolite (Pt@MH-S-1) were prepared by the sequential alkali etching and recrystallization of parent microporous silicalite-1 zeolite. Then, toluene and acetone were employed as probe molecules to determine the catalytic behavior of Pt@MH-S-1 for the elimination of volatile organic compounds (VOCs). The results reveal that Pt@MH-S-1 with multi-hollow structure owns large external specific surface area for dispersing the Pt NPs, and abundant mesoporous channels for improving the accessibility of toluene to Pt NPs as well as high reactive oxygen content, excellent toluene adsorption capacity and moderate adsorption strength. Owing to these characteristics, Pt@MH-S-1 exhibits superior performance both in toluene and acetone catalytic oxidations as reflected by 100% conversion acquired at even a low temperature of 137 and 180 degrees C, respectively. Moreover, Pt@MH-S-1 also shows good stability toward the various conditions, signifying its superiority and potential in practical application for VOCs treatment.

Synthesizing zeolites, which are important materials used in the petroleum and chemical industries, from natural aluminosilicate minerals has been qualitatively recognized as a greener approach compared to that from traditional Si- and Al-containing chemicals; however, studies on the quantitative environmental impacts are still lacking. Herein, life cycle assessment (LCA) and green metrics (atom economy and environmental factor) were employed to comparatively assess the life cycle environmental impacts of zeolites synthesized from chemicals and natural minerals at the industrial scale. The values of seven LCA impact categories and sensitivity analysis between them were thoroughly compared. The results showed that, for each category, the synthesis from natural minerals has lower environmental impacts to varying degrees than that from chemicals. Further efficiency analysis of zeolite manufacturing technologies by green metrics indicated that the synthesis from natural minerals outperforms that from chemicals in terms of the resource utilization rate. The quantitative results indicate that significant benefits stem from the replacement of raw materials from chemicals to natural minerals. This work may provide a basis for the future selection and upgrade of zeolite production processes. Life cycle assessment and green metrics were used to comparatively assess the synthesis of zeolites from natural minerals and chemicals in which the former exhibits a better balance between efficiency and environmental impacts than the latter.

Correction for 'Comparative environmental assessment of zeolites synthesized from chemicals and natural minerals' by Xiaoling Chen et al., Green Chem., 2024, 26, 5273-5283, https://doi.org/10.1039/D3GC05146C.

FAU-type zeolites are an important class of porous aluminosilicate materials with a 3-dimiensional network of accessible micropores (0.74 nm), which primarily encompass X and Y zeolites. Typically, FAU zeolite with a framework SiO2/Al(2)O3 molar ratio between 2.0 and 3.0 is called X zeolite, and that is greater than 3.0 is classified as Y zeolite. Due to their distinctive structure and pore characteristics, FAU-type zeolites have emerged as one of the most widely used catalysts, catalyst carriers, and adsorbents in the chemical industry. However, the sole microporous channels of the conventional FAU-type zeolites not only make them difficult for the reactions involving bulky molecules to occur within pore channel, leading to insufficient contact between reactants with active sites of the zeolite, but also restrict the diffusion of product within the zeolite, thus affecting the activity and lifetime of the catalyst. Therefore, the key to improving the performance of FAU-type zeolites lies in alleviating the adverse effects of micropore diffusion on mass transfer. Introducing mesopores and/or macropores into microporous zeolites to construct hierarchical zeolites with a multi-modal pore structure is believed to be a promising approach. This modification not only can preserve the active sites from the microporous structure, but also significantly enhances the diffusion rate of guest molecules within the zeolites. Consequently, researchers have concentrated on the preparation and application of hierarchical zeolites. This article focuses on the current research status on the preparation of hierarchical X and Y zeolites based on "bottom-up" direct synthesis and "top-down" post-treatment methods. The direct synthesis method mainly comprises template and template-free methods. In terms of the template method, the pore structure of FAU zeolites can be tailored by altering the nature of the templating agent, synthesis conditions and so on. Differently, the template-free method enables the preparation of hierarchical FAU zeolites without the addition of any template. In particular, hierarchical X and Y zeolites have been successfully synthesized directly from natural aluminosilicate minerals without the use of organic templates, which not only reduces the synthesis cost of hierarchical zeolites from raw materials, but also contributes to environmental protection. This method provides a novel synthetic pathway for the preparation of hierarchical zeolites in a low-cost and green way. On the other hand, posttreatment method based on desilication and dealumination is the main method for the preparation of hierarchical Y zeolite, whereas few researchers have made use of post-treatment method to introduce meso/macroporous structures into X zeolite because of the poor chemical stability of X zeolite. In addition, the article introduces the application performance of hierarchical X and Y zeolites in adsorption, catalysis as well as other reaction processes. Despite the superior diffusion capabilities of hierarchical FAU-type zeolites, there are several problemsincluding high cost of organic templates and pollution emissions from the removal of template in the process of synthesizing hierarchical zeolites based on template method, limiting the industrial application of this method. As a result, designing cheap and recyclable templates is the key to realizing green and low-cost preparation of hierarchical FAU-type zeolite. Furthermore, post-treatment method cannot achieve the regulation of mesoporous size in hierarchical zeolites. Future research should deeply investigate the structureactivity relationship between the pore structure and reaction performance of hierarchical FAU-type zeolites, so as to further open pore channels, and enhance diffusion, thus promoting the development of hierarchical FAU-type zeolites in industrial applications.

A seed-directed approach to synthesizing FeZSM-22 zeolite without organic structure directing agent (OSDA) was developed by using Fe-rich diatomite as all aluminum and iron sources. The FeZSM-22 zeolite with optimal crystallinity and purity can be obtained by systematically adjusting feed composition and synthesis conditions. Characterizations show that FeZSM-22 zeolite synthesized with OSDA-free owns high crystallinity, obvious thin needle-shaped morphology and high Bronsted/Lewis acid ratio. Significantly, when used for n-octane hydroisomerization reaction, its derived catalyst exhibits the best catalytic performance reflected by the highest selectivity to C8 isomers compared to the two reference catalysts prepared based on a Fe-containing and a Fe-free ZSM-22 synthesized through an OSDA-directed route from natural diatomite and conventional chemicals, respectively. This work provides an alternative route to sustainably synthesizing heteroatomic zeolites with high performance.

A sustainable defect-engineering strategy for the dealumination of Y zeolite is described. This strategy includes the green synthesis of a well-crystallized Y zeolite with point defects arising from the incorporation of Fe atoms by using Fe-containing perlite and the subsequent preparation of ultra-stable Y (USY) zeolite by efficient steaming dealumination. The systematic characterizations verify that Fe atoms originally existing in the perlite are incorporated into the as-synthesized Y zeolite and function as point defects, leading to the distortion of framework Al. The step-by-step investigation of dealumination process shows that vacancies are formed by the extraction of framework Fe in ammonium exchange, and the framework dealumination is promoted under the combined effect of the distorted framework Al and the formed vacancies during steaming treatment. The resulting USY zeolite owns excellent features in (hydro)thermal stability, pore structure and acid property, and exhibits outstanding catalytic performance in the cracking of n-octane and 1,3,5-triisopropylbenzene.

In order to develop a high-efficiency iron oxide catalyst for the slurry-phase hydrocracking of poor heavy oil, the mesoporous iron oxide was successfully synthesized by using the waste wood powder as a template, and the influence of alkali concentration in the resulting solution on crystal phase, morphology and pore structure of the synthesized samples was investigated. The crystal phase of the synthesized iron oxide transfers from alpha-Fe2O3 to gamma-Fe2O3, and their crystal sizes gradually decrease with an increase of alkali concentration based on the XRD and HRTEM results. Additionally, the iron oxide with mesoporous structure, larger surface area and pore volume is obtained at the higher concentration of alkali in solution confirmed by N2 adsorption-desorption analysis. The assessment result of the iron oxide catalyst employed in the slurry-phase hydrocracking of vacuum residue (VR) illustrates that the yields of gasoline and diesel distillates obtained over Fe-O-B20, Fe-O-B24 and Fe-O-B30 cata-lysts are higher compared with those over Fe-O-B2 and Fe-O-B14 catalysts, it can be attributed that more exposure Fe active sites derived from their larger surface area and pore volume availably improve the catalyst hydroge-nation activity, which can inhibit the over-cracking reaction of intermediate products and the condensation of polycyclic aromatic hydrocarbon in VR to enhance the yields of gasoline and diesel distillates.

Deep understanding of the formation mechanism is crucial to the rational design and controllable synthesis of zeolites with desired pore architecture and acidity. Herein, we take the synthesis of NaA zeolite from a submolten salt depolymerized kaolin (SMS-K) as an example to elucidate the formation mechanism of NaA zeolite. By using SMS-K as sole Si and Al sources, a highly pure and crystalline NaA zeolite with superior ion exchange ability was synthesized. By using various ex-situ and in-situ characterizations and studying the crystallization kinetics, a plausible formation mechanism of NaA zeolite via the mesoscale reorganization of SMS-K was proposed. The results indicate that the reorganization of SMS-K into NaA zeolite follows the solid-phase transformation route. Upon being mixed with H2O, SMS-K that is mainly composed of silicate monomers and chain/ring microstruc-tures is in-situ transformed rapidly into mesoscale intermediates containing double four-membered rings and beta cages, sufficient stirring during aging generates more mesoscale intermediates. During the subsequent crystal-lization process, the mesoscale intermediates are further self-assembled into NaA nanoparticles when theirs amount reaches a maximum, and finally the nanoparticles grow into well-shaped cubic NaA zeolite particles with smooth surfaces through layer spreading. Our work provides the theoretical foundation for the design and green synthesis of zeolites directly from the natural minerals.

Various Ni supported on active carbon (Ni/AC) catalysts were acquired by reduced at different temperatures, among which Ni/AC-500 possesses the smallest particle sizes of metallic Ni species, favoring to more active sites exposed on the catalyst surface, and the suitable content of metallic Ni0, implying the high hydrogenolysis activity obtained. Additionally, the highest mesoporous volume of Ni/AC-500 promotes the diffusion of large molecules from lignin depolymerization. Therefore, Ni/AC-500 exhibits the higher lignin conversion and yields of liquid bio-oil and monomers, but the lower yield of bio-char in lignin hydrodepolymerization due to its higher hydrogenolysis activity compared with other catalysts.

Beta分子筛作为一种重要的催化材料,被广泛应用于石油化工、煤化工及环境保护等领域,但其常规的水热合成过程存在成本高、单釜产率低和废水排放量大等问题.本研究提出了一条基于天然矿物介尺度结构解聚-重组装的无溶剂绿色合成Beta分子筛的新路线,采用该路线所合成的Beta分子筛(Beta-Anhyd)含有丰富的介孔和大孔结构,且具有较商业Beta分子筛(Beta-Ref)更高的比表面积和更低的酸量,以其为载体,通过脱Al补Sn制备的Sn-Beta催化剂(Beta-Anhyd-Deal)在丙烷脱氢反应中表现出较参比催化剂(Beta-Ref-Deal)更加优异的催化性能.

The nature and distribution of Cu species in Cu-SSZ-13 play a vital role in selective catalytic reduction of NO by NH3 (NH3-SCR), but existing methods for adjusting the Cu distribution are complex and difficult to control. Herein, we report a simple and effective ion-exchange approach to regulate the Cu distribution in the one-pot synthesized Cu-SSZ-13 that possesses sufficient initial Cu species and thus provides a “natural environment” for adjusting Cu distribution precisely. By using this proposed strategy, a series of Cu-SSZ-13x zeolites with different Cu contents and distributions were obtained. It is shown that the dealumination of the as-synthesized Cu-SSZ-13 during the ion-exchange generates abundant vacant sites in the double six-membered-rings of the SSZ-13 zeolite for relocating Cu2+ species and thus allows the redistribution of the Cu species. The catalytic results showed that the ion-exchanged Cu-SSZ-13 zeolites exhibit quite different catalytic performance in NH3-SCR reaction but superior to the parent counterpart. The structure–activity relationship analysis indicates that the redistribution of Cu species rather than other factors (e.g., crystallinity, chemical composition, and porous structure) is responsible for the improved NH3-SCR performance and SO2 and H2O resistance. Our work offers an effective method to precisely adjust the Cu distribution in preparing the industrial SCR catalysts.

A green and novel strategy to construct single-crystal hierarchical zeolites has been developed by using a degradable polymer as a multiple-functional template. The obtained MFI zeolite shows excellent catalytic activity in bulky molecules cracking.

Aluminum-rich hierarchical MFI-type zeolites with high acidic-site density exhibit excellent activity and selectivity in bulky molecule-involved reactions. However, it is challenging to develop a facile and environmentally benign method for fabricating them. Herein, we employ a polymer that does not contain nitrogen and halogen elements to successfully synthesize aluminum-rich hierarchical ZSM-5 zeolite with a Si/Al ratio of 8 and a significant number of mesopores comprised of oriented-assembled nanocrystals. It is demonstrated that the nitrogen- and halogen-free polymer is instrumental in the formation of the ZSM-5 zeolite by serving as a template for constructing the hierarchical micro/mesoporous structure. Moreover, this polymer also acts as a crystal growth modifier to form a single-crystalline zeolite. Notably, the resultant zeolite shows a better catalytic performance in converting waste plastic into hydrocarbons than a commercial one. Our work enables the synthesis of high-quality hierarchical zeolites without requiring quaternary ammonium templates.