Search Results (22)

In the dimethyl ether (DME)-to-olefin (DTO) reaction over 20 types of P-loaded ferrierite zeolites with different P loading amounts, the synthesis of n-butenes such as 1-butene, trans-2-butene, and cis-2-butene was investigated to maximize the n-butene yield by optimizing the P loading amount. The zeolites were characterized using X-ray diffractometry (XRD), N₂ adsorption-desorption isotherms, and NH₃ temperature-programmed desorption (NH₃-TPD). Micropore and external surface areas, total pore and micropore volumes, and weak and strong acids affected the DTO reaction’s characteristics. The P-loaded ferrierite zeolite with a P loading of 0.3 wt.% calcined at 500 °C exhibited an n-butene yield of 35.7 C-mol%, which exceeds the highest yield reported to date (31.2 C-mol%). Multiple regression analysis using the obtained data showed that the strong acid/weak acid ratio and total pore volume had a high correlation with the n-butene yield, with a contribution rate of 64.3%. Based on the multiple regression analysis results, the DTO reaction mechanism was discussed based on the proposed reaction model involving the dual-cycle mechanism. Full article

The zeolite-catalyzed conversion of DME into chemicals is considered environmentally friendly in industry. The periodic density functional theory, statistical thermodynamics, and the transition state theory are used to study some possible parallel reactions about the hydrogen-bonded DME over zeolite ferrierite. The following are the key findings: (1) the charge separation probably leads to the conversion of a hydrogen-bonded DME into a dimethyl oxonium ion (i.e., DMO⁺ or (CH₃)₂OH⁺) with a positive charge of about 0.804 e; (2) the methylation of DME, CH₃OH, H₂O, and CO by DMO⁺ at the T2O6 site of zeolite ferrierite shows the different activated internal energy (∆E^≠) ranging from 18.47 to 30.06 kcal/mol, implying the strong methylation ability of DMO⁺; (3) H-abstraction by DMO⁺ is about 3.94–15.53 or 6.57–18.16 kcal/mol higher than DMO⁺ methylation in the activation internal energy; (4) six DMO⁺-mediated reactions are more likely to occur due to the lower barriers, compared to the experimental barrier (i.e., 39.87 kcal/mol) for methyl acetate synthesis; (5) active intermediates, such as (CH₃)₃O⁺, (CH₃)₂OH⁺, CH₃CO⁺, CH₃OH₂⁺, and CH₂=OH⁺, are expected to appear; (6) DMO⁺ is slightly weaker than the well-known surface methoxy species (ZO-CH₃) in methylation; and (7) the methylated activity declines in the order of DME, CH₃OH, H₂O, and CO, with corresponding rate constants at 463.15 K of about 3.4 × 10⁴, 1.1 × 10², 0.18, and 8.2 × 10⁻² s⁻¹, respectively. Full article

Methyl acetate (MA) has a wide range of applications as an important industrial chemical. Traditional MOR zeolite for carbonylation of DME to MA accumulated carbon easily because of a 12-membered ring (12 MR) channel. In this work, we innovatively developed the method of recrystallization ferrierite (FER) zeolite using special chelating ligand sodium oleate which can affect ions other than alkali metals. The characterization results of N₂ adsorption, transmission electron microscopy (TEM), and Fourier transform infrared spectroscopy (FT-IR) show that hydrothermal recrystallization of ferrierite using sodium oleate resulted in a higher Si/Al ratio, a bigger specific surface area and a larger number of Brønsted acid sites in the eight MR channels, which was more efficient in the reaction of carbonylation of dimethyl ether than ordinary alkali treatment. Full article

Various ferrierite zeolites were investigated as catalysts for the dimethyl ether (DME)-to-olefin (DTO) reactions to efficiently synthesize n-butene, such as 1-butene, trans-2-butene, and cis-2-butene except for iso-butene using a fixed-bed flow reactor. Twenty P-loaded ferrierite zeolites with different structural parameters and acidic properties were prepared by the impregnation method by varying the P content and the temperature of air calcination as a pretreatment. The zeolites were characterized by X-ray diffraction (XRD), N₂ adsorption-desorption, and NH₃ temperature-programmed desorption (NH₃-TPD). Micropore surface area, external surface area, total pore volume, micropore volume, and weak and strong acid sites affected the DTO reaction behavior. A high n-butene yield (31.2 C-mol%) was observed, which is higher than the previously reported maximum yield (27.6 C-mol%). Multiple regression analysis showed that micropore surface area and strong acid sites had a high correlation with n-butene yield. Based on our findings, we explained the reaction mechanism for selective n-butene synthesis except for iso-butene in the DTO reaction by the dual cycle model. Full article

A mechanistic model on catalyst deactivation by coke formation in a continuous stirred tank reactor (CSTR) has been developed in the paper. Catalyst deactivation by coke formation was treated as a surface reaction. Four reaction mechanisms representing coke formation through different routes were proposed. The evolved system of ordinary differential equations (ODEs) was solved numerically using MATLAB. This approach was validated by applying it to the skeletal isomerization of 1-pentene over ferrierite. Simulation results were compared qualitatively to those obtained from the literature. Simulation results indicated that coke formation is an extremely rapid process with fast formation of coke components on the strongest acid sites leading to final coke. The coke deposition is slower at higher residence times resulting in more stable product formation and weaker deactivation. The results obtained from this work revealed that the developed model is indeed able to successfully demonstrate the most essential features of catalyst deactivation by coke formation and are in agreement with the findings in the literature. Future work is aimed to extend the study to different reactors such as a plug flow reactor, in addition to analysis of the reaction system’s sensitivity to variables such as temperature and pressure. Full article

Wellbore-plugging materials are threatened by challenging plugging and abandonment (P&A) conditions. Hence, the integrity and resilience of these materials and their ability to provide sufficient zonal isolation in the long-term are unknown. The present work focuses on investigating the potential to use zeolites as novel additives to the commonly used Class-H cement. Using four different zeolite–cement mixtures (0%, 5%, 15% and 30%, by weight of cement) where samples were cast as cylinders and cured at 90 °C and 95% relative humidity, the unconfined compressive strength (UCS) testing showed a 41% increase with the 5% ferrierite addition to the Class-H cement in comparison to neat Class-H cement. For triaxial compression tests at 90 °C, the highest strength achieved by the 5% ferrierite-added formulations was 68.8 MPa in comparison to 62.9 MPa for the neat Class-H cement. The 5% ferrierite formulation also showed the lowest permeability, 13.54 μD, which is in comparison to 49.53 μD for the neat Class-H cement. The overall results show that the 5% ferrierite addition is the most effective at improving the mechanical and petrophysical properties based on a water/cement ratio of 0.38 when tested after 28 days of curing in 95% relative humidity and 90 °C. Our results not only demonstrate that zeolite is a promising cement additive that could improve the long-term strength and petrophysical properties of cement formulations, but also provide a proposed optimal formulation that could be next utilized in a field trial. Full article

The direct hydrogenation of CO₂ into dimethyl-ether (DME) has been studied in the presence of ferrierite-based CuZnZr hybrid catalysts. The samples were synthetized with three different techniques and two oxides/zeolite mass ratios. All the samples (calcined and spent) were properly characterized with different physico-chemical techniques for determining the textural and morphological nature of the catalytic surface. The experimental campaign was carried out in a fixed bed reactor at 2.5 MPa and stoichiometric H₂/CO₂ molar ratio, by varying both the reaction temperature (200–300 °C) and the spatial velocity (6.7–20.0 NL∙g_cat⁻¹∙h⁻¹). Activity tests evidenced a superior activity of catalysts at a higher oxides/zeolite weight ratio, with a maximum DME yield as high as 4.5% (58.9 mg_DME∙g_cat⁻¹∙h⁻¹) exhibited by the sample prepared by gel-oxalate coprecipitation. At lower oxide/zeolite mass ratios, the catalysts prepared by impregnation and coprecipitation exhibited comparable DME productivity, whereas the physically mixed sample showed a high activity in CO₂ hydrogenation but a low selectivity toward methanol and DME, ascribed to a minor synergy between the metal-oxide sites and the acid sites of the zeolite. Durability tests highlighted a progressive loss in activity with time on stream, mainly associated to the detrimental modifications under the adopted experimental conditions. Full article

In this study, 1 wt% platinum (Pt) nanoparticles were incorporated into five types of zeolites (HY, Beta, mordenite, ZSM-5, and ferrierite) with an impregnation technique. The synthesis strategy included the use of water as a solvent for the applied Pt source. Moreover, the incorporation process was performed at ambient conditions followed by calcination at 450 °C. The five prepared materials were characterized by different physical and chemical characterization techniques and the obtained results confirmed the formation of Pt nanoparticles with an average size of 5–10 nm. The catalytic performance of the prepared materials was evaluated in the hydrogenation of cyclohexene under a solvent-free system at room temperature. Pt nanoparticles supported on ZSM-5 zeolite exhibited the best catalytic performance. Moreover, the optimization of operational conditions such as temperature, pressure, and catalyst amount was investigated and the obtained results showed the possibility to convert 100% of cyclohexene within 35 min over Pt-ZSM-5. Finally, the reusability of the Pt-ZSM-5 catalyst was investigated in four consecutive runs without treatment and the obtained results showed a negligible activity loss. Full article

Nowadays, fibrous minerals pose as significant health hazards to humans, and exposure to these fibers can lead to the development of severe pulmonary diseases. This work investigated the morphology, crystal structure, chemistry, and surface activity of fibrous ferrierite recently found in northern Italy through an integrated approach using scanning electron microscopy–energy dispersive spectroscopy, electron microprobe, inductively coupled plasma atomic emission spectrometry, X-ray powder diffraction, and electron paramagnetic resonance. Our results show that a notable amount of ferrierite fibers are breathable (average length ~22 µm, average diameter 0.9 µm, diameter-length ratio >> 1:3) and able to reach the alveolar space (average D_ae value 2.5 μm). The prevailing extra-framework cations are in the Mg > (Ca ≈ K) relationship, R is from 0.81 to 0.83, and the Si/Al ratio is high (4.2–4.8). The <T-O> bond distances suggest the occurrence of some degree of Si,Al ordering, with Al showing a site-specific occupation preference T1 > T2 > T3 > T4. Ferrierite fibers show high amounts of adsorbed EPR probes, suggesting a high ability to adsorb and interact with related chemicals. According to these results, fibrous ferrierite can be considered a potential health hazard, and a precautionary approach should be applied when this material is handled. Future in vitro and in vivo tests are necessary to provide further experimental confirmation of the outcome of this work. Full article

Zeolite catalysts that could allow the efficient synthesis of n-butene, such as 1-butene, trans-2-butene, and cis-2-butene, in the dimethyl ether (DME)-to-olefin (DTO) reaction were investigated using a fixed-bed flow reactor. The zeolites were characterized by N₂ adsorption and desorption, X-ray diffraction (XRD), thermogravimetry (TG), and NH₃ temperature-programmed desorption (NH₃-TPD). A screening of ten available zeolites indicated that the ferrierite zeolite with NH₄⁺ as the cation showed the highest n-butene yield. The effect of the temperature of calcination as a pretreatment method on the catalytic performance was studied using three zeolites with suitable topologies. The calcination temperature significantly affected DME conversion and n-butene yield. The ferrierite zeolite showed the highest n-butene yield at a calcination temperature of 773 K. Multiple regression analysis was performed to determine the correlation between the six values obtained using N₂ adsorption/desorption and NH₃-TPD analyses, and the n-butene yield. The contribution rate of the strong acid site alone as an explanatory variable was 69.9%; however, the addition of micropore volume was statistically appropriate, leading to an increase in the contribution rate to 76.1%. Insights into the mechanism of n-butene synthesis in the DTO reaction were obtained using these parameters. Full article

CO₂-derived methanol and dimethyl ether can play a very important role as fuels, energy carriers, and bulk chemicals. Methanol production from CO₂ and renewable hydrogen is considered to be one of the most promising pathways to alleviate global warming. In turn, methanol could be subsequently dehydrated into DME; alternatively, one-step CO₂ conversion to DME can be obtained by hydrogenation on bifunctional catalysts. In this light, four oxide catalysts with the same Cu and Zn content (Cu/Zn molar ratio = 2) were synthesized by calcining the corresponding CuZnAl LDH systems modified with Zr and/or Ce. The fresh ex-LDH catalysts were characterized in terms of composition, texture, structure, surface acidity and basicity, and reducibility. Structural and acid–base properties were also studied on H₂-treated samples, on which specific metal surface area and dispersion of metallic Cu were determined as well. After in situ H₂ treatment, the ex-LDH systems were tested as catalysts for the hydrogenation of CO₂ to methanol at 250 °C and 3.0 MPa. In the same experimental conditions, CO₂ conversion into dimethyl ether was studied on bifunctional catalysts obtained by physically mixing the ex-LDH hydrogenation catalysts with acid ferrierite or ZSM-5 zeolites. For both processes, the effect of the Al/Zr/Ce ratio on the products distribution was investigated. Full article

Ferrierites and their delaminated forms (ITQ-6), containing aluminum or titanium in the zeolite framework, were synthetized and modified with copper by an ion-exchange method. The obtained samples were characterized with respect to their chemical composition (ICP-OES), structure (XRD, UV-Vis DRS), textural parameters (N₂-sorption), surface acidity (NH₃-TPD), form and reducibility of deposited copper species (UV-Vis DRS and H₂-TPR). Ferrierites and delaminated ITQ-6 zeolites modified with copper were studied as catalysts for the selective catalytic oxidation of ammonia to dinitrogen (NH₃-SCO). It was shown that aggregated copper oxide species, which were preferentially formed on Ti-zeolites, were catalytically active in direct low-temperature ammonia oxidation to NO, while copper introduced into Al-zeolites was present mainly in the form of monomeric copper cations catalytically active in selective reduction of NO by ammonia to dinitrogen. It was postulated that ammonia oxidation in the presence of the studied catalysts proceeds according to the internal-selective catalytic reduction mechanism (i-SCR) and therefore the suitable ratio between aggregated copper oxide species and monomeric copper cations is necessary to obtain active and selective catalysts for the NH₃-SCO process. Cu/Al-ITQ-6 presented the best catalytic properties possibly due to the most optimal ratio of these copper species. Full article

As one of the most important porous materials, zeolites with intricate micropores have been widely employed as catalysts for decades due to their large pore volume, high surface area, and good thermal and hydrothermal stabilities. Among them, ferrierite (FER) zeolite with a two-dimensional micropore structure is an excellent heterogeneous catalyst for isomerization, carbonylation, cracking, and so on. In the past years, considering the important industrial application of FER zeolite, great efforts have been made to improve the synthesis of FER zeolite and thus decrease the synthesis cost and enhance catalytic performance. In this review, we briefly summarize the advances in the synthesis of FER zeolite including the development of synthesis routes, the use of organic templates, organotemplate-free synthesis, the strategies of morphology control, and the creation of intra-crystalline mesopores. Furthermore, the synthesis of hetero-atomic FER zeolites such as Fe-FER and Ti-FER has been discussed. Full article

The present studies were conducted to show the potential of 2D zeolites as effective and non-toxic carriers of drugs. Layered zeolites exhibit adjustable interlayer porosity which can be exploited for controlled drug delivery allowing detailed investigation of the drug release because the structure of the carrier is known exactly. This study was conducted with model drugs ciprofloxacin and piracetam, and ZSM-55 with ca 1 nm thick layers, in detemplated and pillared forms. The release profiles differed from the commercial, crystalline forms of drugs—the release rate increased for ciprofloxacin and decreased for piracetam. To understand the dissolution mechanisms the release data were fitted to Korsmeyer-Peppas equation, showing Fickian (for pillared) and anomalous (for detemplated sample) transport. FT-IR studies showed that strong interaction carrier-drug may be responsible for the modified, slowed down release of piracetam while better solubility and faster release of ciprofloxacin was attributed to formation of the protonated form resulting in weaker interaction with the zeolite than in the pure crystalline form. Two independent tests on L929 mice fibroblasts (ToxiLight and PrestoBlue) showed that ZSM-55, in moderate concentrations may be safely used as a carrier of drug molecules, not having negative effect on the cells viability or proliferation rate. Full article

The manufacturing of technical catalysts generally involves a sequence of different process steps, of which co-precipitation is one of the most important. In this study, we investigate how continuous co-precipitation influences the properties of Cu/ZnO/ZrO₂ (CZZ) catalysts and their application in the direct synthesis of dimethyl ether (DME) from CO₂/CO/H₂ feeds. We compare material characteristics investigated by means of XRF, XRD, N₂ physisorption, H₂-TPR, N₂O-RFC, TEM and EDXS as well as the catalytic properties to those of CZZ catalysts prepared by a semi-batch co-precipitation method. Ultra-fast mixing in continuous co-precipitation results in high BET and copper surface areas as well as in improved metal dispersion. DME synthesis performed in combination with a ferrierite-type co-catalyst shows correspondingly improved productivity for CZZ catalysts prepared by the continuous co-precipitation method, using CO₂-rich as well as CO-rich syngas feeds. Our continuous co-precipitation approach allows for improved material homogeneity due to faster and more homogeneous solid formation. The so-called “chemical memory” stamped during initial co-precipitation is kept through all process steps and is reflected in the final catalytic properties. Furthermore, our continuous co-precipitation approach may be easily scaled-up to industrial production rates by numbering-up. Hence, we believe that our approach represents a promising contribution to improve catalysts for direct DME synthesis. Full article