Mesoporous ZSM-5 Research Articles

Mesoporous Cu-doped ZSM-5 zeolite for efficient radical-mediated decarboxylative silylation

Vinylsilane compounds are essential chemical feedstocks and intermediates in organic synthesis. A heterogeneous Cu-containing mesoporous ZSM-5 zeolite catalyst developed through an in-situ doping method can be used for preparing vinylsilane compounds via decarboxylative coupling with remarkable catalytic efficiency. The mesoporous structure along with the appropriate surface area and pore volume of the catalyst is likely to be responsible for facilitating mass transfer in the reaction process. Additionally, due to the suitable Brønsted and Lewis acid active sites, adsorption and activation of reactant molecules can be readily triggered to promote the generation of alkoxyl radicals, which is the crucial species to complete the catalytic cycle. Importantly, the transformation exhibits high efficiency, broad substrate scope, and good reusability for at least six cycles.

Zeolite Crystallization Inside Chemically Recyclable Ordered Nanoporous Co3O4 Scaffold: Precise Replication and Accelerated Crystallization.

The synthesis of mesoporous zeolites has garnered attention with regard to improving their catalytic and adsorption performances. While the hard-templating method provides opportunities to design precisely controlled hierarchical micro- and mesoporous structures, synthesizing mesoporous zeolites without external precipitation requires significant work. This is mainly due to the absence of usable templates other than carbon with hydrophobic surfaces. Herein, it is demonstrated that the Co3O4 template is valuable in preparing mesoporous silicalite-1 and ZSM-5 with a precisely controlled porous structure through hydrothermal synthesis. Unlike conventional carbon templates, the Co3O4 template is relatively hydrophilic, effective in suppressing external precipitation, and is reusable by dissolving in an acidic solution. The crystallization process also differs from that of the carbon template, as the silicate precipitates on a 3D ordered nanoporous Co3O4 scaffold, followed by crystallization and crystal growth. Furthermore, it is unexpectedly observed that the zeolite crystallization is accelerated in the Co3O4 template. The synthetic approach utilizing nanoporous metal oxides opens new doors for the control of the hierarchical structure of zeolites, as well as for the design of metal oxide-zeolite nanocomposite catalysts, due to the potential extensibility of the combination of metal oxides and zeolites.

In Situ Growth of Mn-Co3O4 on Mesoporous ZSM-5 Zeolite for Boosting Lean Methane Catalytic Oxidation

The low-temperature oxidation of methane gas in coal mine exhaust gas is important for reducing the greenhouse effect and protecting the environment. Unfortunately, the carbon–hydrogen bonds in methane molecules are highly stable, requiring higher reaction temperatures to achieve effective catalytic oxidation. However, metal oxide-based catalysts face the problem of easy sintering and the deactivation of active components at high temperatures, which is an important challenge that catalysts need to overcome in practical applications. In this work, a series of Mn-Co3O4 active components were grown in situ on ZSM-5 zeolite with mesoporous pore structures treated with an alkaline solution via a hydrothermal synthesis method. Due to the presence of polyethylene glycol as a structure-directing agent, manganese can be uniformly doped into the Co3O4 lattice. The large specific surface area of ZSM-5 zeolite allows the active component Mn-Co3O4 to be uniformly dispersed, effectively preventing the sintering and growth of active component particles during the catalytic reaction process. It is worth mentioning that the Mn-Co3O4/meso-ZSM-5-6.67 catalyst has a methane conversion rate of up to 90% at a space velocity of 36,000 mL·g−1·h−1 and a reaction temperature of 363 °C. This is mainly due to the mesoporous ZSM-5 carrier with a high specific surface area, which is conducive to the adsorption and mass transfer of reaction molecules. The active component has an abundance of oxygen vacancies, which is conducive to the activation of reaction molecules and enhances its catalytic activity, which is even higher than that of noble metal-based catalysts. The new ideas for the preparation of metal oxide-based low-temperature methane oxidation catalysts proposed in this work are expected to provide new solutions for low-temperature methane oxidation reactions and promote technological progress in related fields.

The promoting role of framework Ti(IV) in enhancing the hydrodeoxygenation performance of palmitic acid over a mesoporous TS-1 supported Ni catalyst

Developing a highly efficient Ni-based hydrodeoxygenation catalyst is crucial for the production of renewable biodiesel. Herein, a mesoporous TS-1 zeolite supported Ni catalyst (Ni/TS-1-M) exhibited exceptional hydrodeoxygenation (HDO) activity and achieved 100 % yield of deoxygenated hydrocarbons (97.3 % pentadecane vs 2.7 % hexadecane), outperforming other catalysts such as Ni on mesoporous ZSM-5 (Ni/ZSM-5-M), mesoporous Silicalite-1 (Ni/Silicalite-1-M) and TiO2 (Ni/TiO2). The Ti(IV) atoms in the form of TiO4 and TiO6 can transfer its electron to nearby metal Ni, leading to the increase in electron density of metal Ni, which enhanced the hydrogenation activity and facilitated the C–C bond cleavage of the hexadecanal to produce pentadecane. Furthermore, the framework Ti(IV) species accelerated the esterification process to generate palmityl palmitate, which was easily hydrogenolyzed to the main intermediate of hexadecanol under the synergistic effect of metal Ni and Ti(IV) on Ni/TS-1-M catalyst. The formed hexadecanol mainly underwent successive dehydrogenation/decarbonylation process to transform into pentadecane.

Solid-conversion synthesis of three-dimensionally ordered mesoporous ZSM-5 catalysts for the methanol-to-propylene reaction

Solid-conversion synthesis of three-dimensionally ordered mesoporous ZSM-5 catalysts for the methanol-to-propylene reaction

Catalytic pyrolysis of high-density polyethylene (HDPE) over hierarchical ZSM-5 zeolites produced by microwave-assisted chelation-alkaline treatment

A new microwave (MW) assisted chelation-alkaline strategy was developed to produce hierarchical ZSM-5 zeolites (with external surface area of 203 m2/g) in minutes, leading to the formation of heterogeneous structure with a high-silica shell and aluminium-rich core (silicon-to-aluminium ratios of 49.2 and 37.6, respectively). The zeolites were assessed comparatively by catalytic pyrolysis of high-density polyethylene (HDPE). Compared to the mesoporous ZSM-5 zeolite prepared by the conventional alkaline treatment (via desilication by the NaOH aqueous solution), the hierarchical zeolite by the MW-assisted method showed comparable kinetics in catalytic pyrolysis of HDPE, but with the improved stability in the cyclic pyrolysis-regeneration tests. The improved stability could be due to the better-preserved structural integrity thanks to the relatively milder surface etching by the MW-assisted chelation dealumination method. In addition, compared to the parent ZSM-5, the product distribution of HDPE catalytic pyrolysis over the hierarchical ZSM-5 zeolite showed a higher portion of oil products (i.e., 12 wt% vs. 6.9 wt%) and an improved alkane-to-olefin ratio in the oil products (2.22 vs. 1.86, respectively) due to the reduced acidity and improved hydrogen transfer ability. The MW-assisted chelation-alkaline treatment could be a new strategy to regulate the trade-off between stability and activity of zeolites for catalytic applications.

Sustainable biofuel synthesis from non-edible oils: a mesoporous ZSM-5/Ni/Pt catalyst approach.

This work examines the hydrodeoxygenation (HDO) activity of non-edible oils using a high surface area catalyst. The HDO activity was thoroughly examined and contrasted using the high surface area catalyst Ni/Pt-ZSM-5 as well as other supports like MCM-48 and H-beta. Ni/Pt bimetals supported on mesoporous ZSM-5 were created via reverse order impregnation to facilitate HDO of non-edible oils. Techniques such as XRD, FT-IR, BET, HR-TEM, HR-SEM, TPD, and TGA were used to characterize the produced catalysts. The synthesized catalysts considerably influenced the hydrodeoxygenation activities for the synthesis of lengthy chain hydrocarbons in a stainless-steel reactor with a high-pressure fixed bed between 300 and 375 °C under 10-40 bar hydrogen pressure. High levels of Ni/Pt-ZSM-5 acidity, textural, and H2 consumption qualities were discovered. Distributions of the products were also reviewed, along with comparisons of the structure-activity connections.

Synergistic catalysis by Brønsted acid and Pd species on a mesoporous ZSM-5 zeolite for the oxidative homocoupling of terminal alkynes

The Brønsted acid and Pd species on Pd@MZSM-5 synergetically catalyzed the oxidative homocoupling of terminal alkynes, where the Brønsted acid promote the alkyne chemisorption and benefit the formation of the alkynyl-palladium(ii) complex.

Catalytic reforming of cellulose pyrolysis volatiles over hierarchical HZSM-5: Mechanism of a protective effect of tetrapropylammonium (TPA+) during alkali treatment

A series of HZSM-5 with hierarchical pores was obtained by using a modified NaOH treatment method. This modification incorporated the use of tetrapropylammonium bromide. Furthermore, their catalytic performance for reforming of cellulose pyrolysis volatiles at 600 °C was investigated. TPAB-assisted alkali treatment increased the mesoporosity, relative crystallinity, and surface integrity of ZSM-5. Additionally, a significant portion of the acidic sites was preserved. The 0.1TPAB-0.2AT, treated with 0.1 M TPAB and 0.2 M NaOH, yielded the highest light aromatics at 156.9 mg/g. The coking resistance of the catalyst was also improved. Tetrapropylammonium (TPA+) achieves surface protective desilication by selectively adsorbing Si(0Al) on the zeolite. Subsequently, the continuous adsorption of TPA+ leads to mesopore formation within the zeolite. This continuous restriction on desilication limits the increase in mesopore volume, resulting in a relatively abundant and uniform distribution of smaller mesopores on ZSM-5. This mechanism holds promise for future synthesis of highly mesoporous ZSM-5.

Oxidation of 1,2-diarylalkynes to 1,2-diketones on acidic mesoporous ZSM-5 supported palladium catalyst

1,2-diketones are important compounds in natural products and bioactive molecules. Current synthesis methods are involved the use of various environmentally hazardous additives and expensive organic ligands in homogeneous catalysis, which limited their practical application. Acidic mesoporous ZSM-5 zeolite supported palladium (Pd/HMZSM-5) was found to be able to transform 1,2-diarylalkynes to 1,2-diketones without any additives. The CC bond of 1,2-diarylalkyne coordinated with PdII sites to form a metal-π complex that was easily nucleophilic attacked by DMSO to form final product. The acidic sites on the catalyst can promote the adsorption and coordination of 1,2-diarylalkyne with PdII and improve the reaction activity.

Influence of the Mesoporosity of Hierarchical ZSM-5 in Toluene Alkylation by Methanol.

Among the different strategies to design highly shape-selective ZSM-5 to obtain para-xylene through toluene alkylation with methanol, the introduction of mesopores to increase reactant and product diffusion has been proposed but barely studied. In this study, we prepared mesoporous ZSM-5 catalysts, named ZSM5-MT(x), from commercial ZSM-5 (Si/Al = 15), using a two-step micelle-templating procedure with octadecyltrimethylammonium bromide as a surfactant in basic medium (x = NaOH/Si). These materials were used as catalysts for the alkylation of toluene by methanol at a low contact time to avoid thermodynamic equilibrium of the xylene isomers. Compared to the parent ZSM-5, the mesoporous ZSM5-MT(x) catalysts did not improve the para-xylene selectivity, revealing that the strategy of increasing diffusion in the catalyst is not a good strategy to follow. However, ZSM5-MT(0.5) showed less deactivation on stream than the parent ZSM-5. Therefore, introducing mesopores to ZSM-5 could be interesting to explore, combined with another strategy of shape selectivity, such as the passivation of the external surface acidity.

Study on synthesis of mesoporous ZSM-5 zeolite using carboxymethyl cellulose mesopore directing agent for re-arrangement of epoxide

This current work presents a study on using carboxylmethyl cellulose (CMC) as mesopore directing agent for synthesis of mesoporous ZSM-5 zeolite. The results showed that CMC, a cellulose derivative can be used as potential mesopore directing agent for synthesis of mesopore zeolite material. The obtained ZSM-5 zeolite was characterized by XRD, SEM methods and was used as catalyst for the isomerization of epoxide to synthesize aldehyde. The synthesized ZSM-5 catalyst exhibited a high catalytic activity and selectivity in the reaction. The highest conversion of about 98,2% was obtained when the isomerization of styrene carried out at suitable reaction conditions.

Comparing the effects of hollow structure and mesoporous structure of ZSM-5 zeolites on catalytic performances in methanol aromatization

Comparing the effects of hollow and mesoporous structures over ZSM-5 zeolites on catalytic behaviors in methanol aromatization was done. Hollow zeolites possessing larger voids, increasing Bronsted acid sites and more framework Al in channel crossings promoted higher benzene, toluene and xylene (BTX) selectivity. Zero-length column (ZLC) desorption of cyclohexane stated that higher diffusion rate was observed over mesopores zeolite and hollow zeolite. However, lower effective diffusion constants (Deff) and higher activation energy of hollow zeolite demonstrated that mass transfer was not only limited by microporosity but by surface barriers resulting from surface defects and pore blockage. The highest diffusion rate of cyclohexane over hollow zeolite was presented indicating that surface barrier was not dominant in diffusion limitation. The stability of hollow ZSM-5 was lower compared to mesoporous ZSM-5 as a result of more strong acid sites and higher external silanol groups, which favored to carbon deposition. Additionally, the collapse of hollow structures with thinner shells also contributed to higher deactivation rate.

Design of ZSM-5 encapsulating FeMnK nanocatalysts for light olefins synthesis with enhanced carbon utilization efficiency

Light olefins are important basic chemical materials, and the synthesis of light olefins from syngas via mild and efficient Fischer-Tropsch catalytic process is attractive. However, the application of technology is still plagued by the carbon utilization efficiency in CO conversion to target products. Therefore, both hydrocarbon distribution regulation and CO2 by-products reduction are desirable. Here, FeMnK oxide encapsulated by the hollow mesoporous ZSM-5 zeolite nanostructures with adjustable Si/Al ratio were constructed via a “dissolution-recrystalization” strategy, denoted as FeMnK@HM-Z-5(x), where x represents Si/Al ratio of ZSM-5 (x=∞, noted as FeMnK@HM-S-1). In catalytic performance, FeMnK@HM-Z-5(x) presented controlled regulation on hydrocarbon distribution and CO2 selectivity, compared with the supported or microporous coating structures, due to the distinct synergistic catalytic effect between FeMnK and ZSM-5. Carbon utilization efficiency reaches the maximum over FeMnK@HM-Z-5(200) with a space–time-yield of 22.7 μmol C2-C4∙gFe∙S-1 at similar CO conversion, due to the harmonization of light olefins selectivity improvement and CO2 suppression with the modulation of Si/Al ratio. With the aid of ethylene pulse experiment, C2H4-TPD, H2-TPD, in situ DRIFTS experiment, it confirmed that the change of light olefins and CO2 selectivity is mainly due to the variety of hydrogenation capacity, which is closely related to the Brønsted acid strength of the catalysts. CO2 pulse experiments further verified that the FeMnK@HM-Z-5(x) catalysts were endowed with different CO2 hydrogenation capacity. This study provides a new strategy for the precise regulation of the products distribution in CO / CO2 hydrogenation to enhance the carbon utilization.

Catalytic conversion of model compounds of plastic pyrolysis oil over ZSM-5

Mechanistic investigation of the catalytic conversion of model compounds for plastic pyrolysis oil (1-octene, octadiene, octane, and toluene) over ZSM-5 in a fixed-bed reactor was studied. 1-Octene breaks down into smaller olefins, which undergo further cracking, oligomerization, cyclization, and hydrogen transfer to eventually produce benzene, toluene, xylene (BTX), coke, and hydrogen. The effect of contact time on 1-octene conversion was further investigated and compared with thermodynamics analyses to elucidate the reaction network. Under the reaction conditions (500 °C, 1 atm), octadiene undergoes thermal coking, significantly contributing to reactor fouling. The products from octane cracking are similar to the products from 1-octene conversion whereas toluene undergoes disproportionation, dealkylation and coking. The analysis of spent catalyst showed long-chain hydrocarbons created by oligomerization reactions filled the pores and covered the surface of the catalyst. When mesoporous ZSM-5 is used instead of conventional, product selectivity is maintained for 70 h in time-on-stream experiments.

Simultaneous hydrodesulfurization of thiophene and benzothiophene over NiMoS catalysts supported on γ-Al2O3 composites containing ZSM-5

Alumina composites containing microporous ZSM-5 (Z-5) and mesoporous ZSM-5 (MZ-5), corresponding to xZA and xMZA, were developed by incorporating Z-5 and MZ-5 into γ - Al2O3, respectively. The two series of NiMoS/xMZA and NiMoS/xZA catalysts were prepared with these two composites as supports, respectively, and were used for the simultaneous hydrodesulfurization (HDS) of thiophene (T) and benzothiophene (BT). The results show that NiMoS/xMZA series catalysts exhibit higher HDS activity than that of NiMoS/xZA and NiMoS/γ-Al2O3, and the HDS activity of NiMoS/xMZA catalysts increases with the increase of MZ-5. The high HDS activity can be mainly attributed to the synergistic effects of the efficient diffusing pore channels, high dispersion of type II NiMoS phases, suitable acidity, and moderate Mo-support interaction. Moreover, the product distribution of HDS shows that the NiMoS/xMZA catalysts possess the dominant direct desulfurization (DDS) selectivity and the selectivity increases with the increase of MZ-5 content due to more corner sites and suitable Brønsted (B) acid sites, whereas the NiMoS/xZA catalysts perform more excellent hydrogenation (HYD) selectivity, and the selectivity increases with the increase of Z-5 content because of the existence of more edge sites. Based on this, the possible reaction network for T and BT hydrodesulfurization over the catalysts are proposed.

Highly efficient mesoporous ZSM-5 for trace olefin removal from aromatic stream

Steam cracking and reforming processes always produce aromatic streams containing trace amounts of olefins, which are harmful to certain processes and applications in the petrochemical industry. In the aromatics complex, clay is used to remove trace olefins. Unfortunately, it has a limited lifespan and must be replaced frequently. In this study, mesoporous ZSM-5 is investigated for its application in the removal of trace olefins. It is prepared using two templates: Tetrapropylammonium bromide and Dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride, resulting in a mesoporous structure with a high pore volume and external surface area. There is an optimum amount of DMOD necessary to achieve the desired degree of mesoporosity within a zeolite. Even though mesoporous ZSM-5 has a similar surface area to microporous ZSM-5, its external surface area is 1.3 to 2.0 times greater than conventional ZSM-5. Consequently, mesoporous ZSM-5 has a higher activity when it comes to removing trace olefins from an aromatic stream than microporous ZSM-5.

Fabrication of BTA-loaded mesoporous silica-encapsulated ZSM-5 molecular sieve for enhancing anti-corrosion performance of waterborne epoxy coatings

Anti-corrosion coatings have been widely applied to protect metals against corrosion attacks. To improve the corrosive resistance, it is an effective way to employ porous materials loaded with corrosion inhibitors as fillers of coatings. One of the critical challenges is to advance the inhibitor loading capability of porous fillers. In this study, the mesoporous silica encapsulation is introduced on the ZSM-5 molecular sieves through the hydrolysis-condensation of tetraethyl orthosilicate (TEOS), followed by calcinated for removing the residual templates. The porous SiO2@ZSM-5 particles are used as micro-nano containers to load corrosion inhibitor benzotriazole (BTA). The morphologies, structures and BTA releasing behaviors are thoroughly investigated. Subsequently, the as-prepared BTA-SiO2@ZSM-5 particles serve as fillers for waterborne epoxy resin (WER) to fabricate BTA-SiO2@ZSM-5/WER composite coatings with long-term anti-corrosion property. The corrosive resistance behavior and mechanism are emphatically tested and analyzed. The results demonstrate that the introduction of mesoporous silica on the ZSM-5 molecular sieves significantly increases the specific surface area and pore volume, which is highly beneficial for improving the BTA loading capability of fillers as well as the anti-corrosion performance of coatings. Moreover, the great dielectric, mechanical and UV light-shielding properties of the composite coatings are confirmed. This study presents an effective and practical route for fabricating long-term anti-corrosive composite coatings.

Synthesis of Green p-Xylene from Biomass-Derived Furans and Bioethanol using Mesoporous ZSM-5 Catalysts

Synthesis of Green p-Xylene from Biomass-Derived Furans and Bioethanol using Mesoporous ZSM-5 Catalysts

Repeatable catalyst, repeat customers

Mesoporosity was introduced into high-silica ZSM-5 zeolite (SiO2/Al2O3 = 417) by controlled desilication using the mixture of NaOH and TEAOH (tetraethylammonium hydroxide), and subsequent phosphorus modification was used to improve the structural stability and acidity reservation of the desilicated ZSM-5 samples during the procedure of severe steam aging treatment. The phosphorus modified mesoporous ZSM-5 sample along with parent ZSM-5, solo phosphorus modified ZSM-5 and mesoporous ZSM-5 were characterized by techniques of N2 adsorption-desorption, NH3-TPD (temperature programmed desorption), IR (infrared) spectroscopy of pyridine adsorption and 27Al & 31P MAS NMR spectroscopy. A mechanism for underlying chemistry of the combinative treatment was proposed. The aluminophosphate formed in the steam activation could interact with the framework aluminum on zeolite, thus achieved to the textural and acidity stabilization during the steam aging. The catalytic performance of these samples was tested by different hydrocarbon cracking reactions. It turned out that owing to its reduced diffusion limitation and stabilized acidity, the phosphorus modified mesoporous ZSM-5 sample exhibited the highest conversion in the bulky molecule cracking reaction. And in the 1-octene cracking reaction under harsh reaction conditions, the steamed phosphorus modified mesoporous ZSM-5 sample exhibited higher activity and more prolonged catalyst life compared to the other steamed catalysts, which could be attributed to the improved coke tolerance capability by mesoporosity introduction and the stabilized acid sites by phosphorus modification.