Mesoporous ZSM-5 Catalysts Research Articles

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

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.

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

Tailoring ZSM-5 zeolite porosity and acidity for efficient conversion of municipal solid waste to fuel

Municipal solid waste contains essential building blocks of transportation fuel but is often deposited into landfills. Available conversion processes are still in their infancy; thus, requiring foundational knowledge to control reaction pathways and transform waste macromolecules into desired products. Active, robust, and low-cost catalysts with highly accessible active sites are needed for selective cleavage of certain bonds. The rapid deactivation and diffusion limitations are the major challenges to date which can be controlled by the catalyst pore structure and acidity. In this paper, we developed novel mesoporous ZSM-5 catalysts to maximise levoglucosan conversion, the dominant product of cellulose pyrolysis, into furfural. The concentration of levoglucosan dropped from 12.1% to 3.8% over the mesoporous ZSM-5. Furthermore, the pyrolysis of plastic materials that existed in the waste provided supplementary hydrogen, which synergistically contributed to the hydrodeoxygenation of some compounds like 5-hydroxymethylfurfural and 4-methyl-1,2-Benzenediol. The total amount of non-oxygenated compounds over the mesoporous catalyst reached 77% compared to 59.7% in non-catalytic pyrolysis based on 13 C NMR results. The integration of 13 C NMR and GC-MS results provided an effective tool in identifying key reaction pathways and linking that to the catalyst's textural and acidic properties. • Co-pyrolysis of biomass and polyethylene was catalysed by core-shell hierarchical ZSM-5. • The conversion of levoglucosan, the dominant product from cellulose, reached 68.3% over meso-ZSM-5. • Desired compounds including aliphatic C–C and hydrodeoxygenated products were obtained. • Accessible zeolite active sites were produced due to mesoporous networks enabling conversion of bulky sugar compounds.

Mesoporous ZSM-5 catalysts for the synthesis of clean jet-fuels by 1-hexene oligomerization

Zeolite is one kind of the solid acid catalysts for the oligomerization process but surfers from rapid deactivation. In this specific study, a series of mesoporous ZSM-5 catalysts have been synthesized and evaluated in the 1-hexene oligomerization. XRD, BET, SEM, TEM, 27Al MAS NMR, 29Si MAS NMR, NH3-TPD, Py-FTIR and TGA analysis were used to characterize the physicochemical properties of zeolites. The synthesized mesoporous zeolites were found to be more stable in the reaction and the initial activity increase significantly compared with the common ZSM-5 zeolite. Moreover, the catalytic activity of mesoporous ZSM-5 zeolite is found to be closely related to the number and the distribution of acid sites. The mesoporous ZSM-5 zeolites with the lower amount of acid sites, moderate strength of Brønsted acid sites inhibiting the cracking and coke products. High L/B ratio enhanced the dimers formation. The efficiency was further highlighted by a high space–time yield (STY) of 557 mg·gcat−1h−1 in the average stage at 260 °C. Compared to conventional ZSM-5 catalyst, the synthesized catalyst displayed excellent resistance to coke deposit.

Effect of Mesopores in ZSM-5 on the Catalytic Conversion of Acetic Acid, Furfural, and Guaiacol

Biomass can be converted into renewable aromatic hydrocarbons through catalytic pyrolysis using ZSM-5 catalysts. Recent studies have found that the mesoporous ZSM-5 catalyst has a higher catalytic efficiency than the conventional microporous catalyst. To further investigate the effect of mesopores in ZSM-5 on the catalytic pyrolysis of biomass, three types of bio-oil model compounds (acetic acid, furfural, and guaiacol) are selected for conversion on synthetic mesoporous and commercial microporous ZSM-5 catalysts. Results show that the mesoporous catalyst exhibits a higher catalytic efficiency for aromatics production compared to the microporous catalyst, especially for guaiacol. However, the carbon yield of benzene, toluene, and xylene decreases as the molecular weight of the reactant increases. Large mesopores (16–45 nm) in the mesoporous catalyst provide more channels for the transportation of phenolic reactants, which can generate aromatics and also coke deposition through multistage cracking in the small mesopores (2–5 nm). Additionally, the reactants undergo condensation reactions on the microporous catalyst surface directly to form coke and block the pore inlet. This study indicates that the mesoporous structure in the ZSM-5 catalyst mainly improves the catalytic conversion efficiency of macromolecules. Therefore, exploring a better structure of hierarchical mesopores suitable for the catalytic conversion of biomass will be the focus of future work.

Influence of ZSM-5 porosity and binder introduction on the coke formation in the cracking of 1,3,5-triisopropylbenzene

Hierarchical ZSM-5 catalysts with different pore sizes from micropore to macropore and their corresponding ZSM-5-based extrudates using SiO2 binders have been successfully prepared. The series of catalysts were used for exploring the influence of pore size as well as the addition of non-acidic SiO2 binders on the catalytic performance and coke formation in the cracking of 1,3,5-triisopropylbenzene (TIPB). It is demonstrated that the TIPB conversion and stability of catalysts improve with increasing the pore sizes of ZSM-5 catalysts. The hierarchical ZSM-5 catalyst including a macropore diameter of about 60 nm exhibited the highest TIPB conversion (98.6 %) and selectivities to propylene (34.2 %) and benzene (60.8 %) with the least amount of carbonaceous compounds, compared to the microporous and mesoporous ZSM-5 catalysts. Also, the addition of non-acidic SiO2 binders has a positive effect on limiting the deactivation of ZSM-5-based extrudates during the cracking of TIPB. Less poly-aromatic species are formed for the catalyst extrudates with SiO2 binders.

Conversion of delignified stem sorghum bicolor into levulinic acid using micro and mesoporous ZSM-5 catalysts

Sorghum bicolor stem is one of the biomass wastes that can be used as raw material for synthesizing platform chemicals. Levulinic acid is one of the chemicals that is currently a substance often synthesized or isolated. Levulinic acid can be catalytically synthesized from sorghum stem waste which is rich in cellulose. Cellulose in the sorghum stem is still bound to lignin and hemicellulose, therefore pretreatment is needed to reduce lignin. The method consists of pretreatment of biomass by delignification, manufacturing of micro and mesoporous ZSM-5 catalysts (double template method) and the reaction of the conversion of stem sorghum to levulinic acid is carried out in a mini reactor. Catalyst characterizations were conducted using FTIR, XRD, SEM EDX and product analysis by HPLC. The result of delignification is the cellulose content increased from 45.10 % to 76.66 %. The result of as-synthesized ZSM-5 showed the diffractogram patterns similar to the standard ZSM-5. SEM image showed a hexagonal coffin-like shape which is the characteristic of ZSM-5. The levulinic acid produced using meso-porous ZSM-5 catalyst was observed at the reaction time of 2–6 h, while the yield of levulinic acid using micro-porous ZSM-5 catalyst was observed at the end of the reaction time, i.e. 6–10 h. It can be concluded that the pore size of the catalyst and the duration of the conversion time influenced the yield of levulinic acid.

Effect of transition metals (Mo, Mn and Co) on mesoporous ZSM-5 catalyst activity in carbon dioxide reforming of methane

This paper investigates the effect of transition metals (Mo, Mn and Co) on mesoporous ZSM-5 support in carbon dioxide reforming of methane reaction. The mesoporous ZSM-5 support was synthesized by micro emulsion technique and the metals were loaded by wet impregnation method. It was observed that ZSM-5 supported Co catalyst had higher surface area in comparison to other catalysts, which could favour well dispersion and wider utilization of active component. In addition, the ZSM-5 supported Co catalyst exhibited the highest methane and carbon dioxide conversions of 69 % and 65 % respectively at 850°C. The Co species were more active to decompose methane and carbon dioxide compared to Mo and Mn loaded catalysts. Hence, loading Co on mesoporous ZSM-5 produce an active catalyst in carbon dioxide reforming methane reaction.

One-pot Synthesis of Hierarchical Mesoporous ZSM-5 from the Assembly of Nanocrystals Using Urea as Additive

A hierarchical mesoporous ZSM-5 catalyst with aggregated nanocrystals structure was one-pot hydrothermally synthesized by using urea as the additive. The crystalline phase, morphology and hierarchical architectures were characterized by the XRD, SEM, TEM and N2 adsorption/desorption analyses. The nano-aggregates showed MFI crystalline phase and were composed of connected nanoparticles. The samples had the high surface area and the pore volume from intercrystalline among the nanoparticles due to spontaneously stacking of nanocrystals. The pyridine-adsorbed FTIR and the catalytic performances in the alkylation of phenol and tert-butyl alcohol were applied to evaluate the accessibility of acid sites and the catalytic activities for the hierarchical mesoporous ZSM-5 samples. The samples possessed high accessibility of acid sites which resulted from their large amount of mesopores, and its catalytic activity was improved dramatically. The phenol conversion could reach up to 95.6%, and the corresponding selectivity of 4-TBP and 2,4-DTBP was 44% and 51.5%, respectively.

The effect of steam on maximizing light olefin production by cracking of ethanol and oleic acid over mesoporous ZSM-5 catalysts

Steam cracking significantly improved light olefin selectivity: mainly ethylene was obtained from ethanol and propylene from oleic acid.

Preparation of mesoporous ZSM-5 catalysts using green templates and their performance in biomass catalytic pyrolysis

The micropores present in ZSM-5 are beneficial to the production of aromatic compounds in biomass catalytic pyrolysis, although the small pore size leads to severe coke deposition on the catalyst. In this study, a micro-mesoporous structured ZSM-5 zeolite catalyst was synthesized and modified with green templates (sucrose, cellulose, and starch) to introduce additional mesopores. It was found that the catalysts modified using the sucrose and cellulose templates only exhibited a slight increase in their micropore volumes, while the mesopore volume of ZSM-ST (modified with the starch template) reached up to 0.359 cm3/g. This increase promoted the cracking of bulky oxygenates and suppressed the polymerization reaction on the ZSM-5 surface, thereby producing a greater number of aromatic products. Moreover, the benzene, toluene, and xylene (BTX) yields exhibited a positive correlation with the catalyst mesopore volume, with the highest BTX yield of 91.84 mg/g being obtained with 10% starch addition.

Selective Cracking of Light Olefins to Ethene and Propene

Catalytic cracking of olefins is becoming a more crucial process to produce valuable platform chemicals in the chemical industry such as ethane and propene. Steam cracking and fluid catalytic cracking can no longer meet the required demand of propene and ethene. Previous research has found that catalytic cracking showed the best results when an acidic mesoporous ZSM-5 catalyst was used. This paper reports the use of ZSM-5 with Si/Al=15, 40 and 70 and post synthetically modified large crystal ZSM-5 and silylated large crystal ZSM-5 (Si/Al = 70). The different catalysts were tested using variable flowrates and temperatures.

Esterification of Benzyl Alcohol with Acetic Acid over Mesoporous H-ZSM-5

In this study, the performance of mesoporous ZSM-5 has been studied on the esterification of acetic acid (AA) with benzyl alcohol (BA). The mesoporous ZSM-5 catalyst has been synthesized with the variation of aging time i.e. 6, 12, and 24 hours at the same temperature, 70 °C. The cation exchange of Na-ZSM-5 to H-ZSM-5 was performed before the catalytic activity test. The acidity type and amount of solids were determined by FT-IR spectroscopy using pyridine as a probe molecule. The characterization by pyridine adsorption showed that at a higher mesoporous surface area, the number of Lewis acid was increased. The highest mesoporous surface area, Lewis, and Brönsted acid sites were obtained by sample which has the lowest crystallinity, i.e. 255.78 m2/g, 0.2732 mmol/g, and 0.20612 mmol/g, respectively. Influence of mesoporous volume was studied on the catalytic activity of the mesoporous ZSM-5 in the esterification reaction. Conversion of acetic acid in the esterification reaction for samples of HZ-6, HZ-12, and HZ-24 were obtained by titration methods, i.e. 39.59, 36.39, and 32.90 %, respectively. Hence, the reaction temperature of 393 K, molar ratio 1:4 (AA:BA) and catalyst loading 5 % were selected as an optimum reaction parameters.

Synthesis, characterization and catalytic activity of hierarchical ZSM-5 templated by carboxymethyl cellulose

Hierarchical ZSM-5 zeolite has been successfully synthesized using carboxymethyl cellulose (CMC) as a mesotemplate. The synthesized samples were characterized by using XRD, FT-IR, Al-NMR spectroscopy, SEM, TEM, TG, N2 adsorption–desorption and NH3-TPD. They exhibited characteristic MFI structure, which was confirmed by XRD and FT-IR analysis. 27Al MAS NMR spectra indicated the presence of tetrahedral co-ordinated Al in the hierarchical zeolite. SEM and TEM images of the sample showed significant mesoporosity. The N2 adsorption/desorption results supported the presence of mesopores. Catalytic activity of the prepared mesoporous ZSM-5 for the acetalization of cyclohexanone with methanol was examined. The effects of molar ratio, catalyst amount and time on cyclohexanone conversion were studied. It has been found that the catalytic activity of mesoporous ZSM-5 catalyst is superior to that of the conventional zeolite for the acetalization of cyclohexanone with methanol.

Efficient Conversion of Light Cycle Oil into High-Octane-Number Gasoline and Light Olefins over a Mesoporous ZSM-5 Catalyst

Producing high-octane-number (ON) gasoline and light olefins is a promising route to valorize light cycle oil (LCO). In this work, the LCO was mildly hydrogenated and then catalytically cracked to produce high-ON gasoline and light olefins. Mesoporous ZSM-5 zeolite (meso-ZSM-5) was prepared and, for the first time, was applied in this process to crack the hydrogenated LCO (hydro-LCO). The catalytic performance of meso-ZSM-5 was evaluated in detail under different reaction temperatures and weight hourly space velocities (WHSVs). The results showed that, in comparison to less than 64 wt % hydro-LCO conversion over the conventional ZSM-5 catalyst, the novel catalyst exhibited excellent performance in cracking hydro-LCO with quite a high conversion of 84.8 wt %, affording a gasoline yield of 56.4 wt % and light olefin yield of 19.3 wt % at 560 °C and 10 h–1. In addition, the conversion behaviors of hydro-LCO components were analyzed over both the conventional ZSM-5 and meso-ZSM-5 catalysts. Finally, on the ba...

In-situ Upgrading of Napier Grass Pyrolysis Vapour Over Microporous and Hierarchical Mesoporous Zeolites

This study presents in-situ upgrading of pyrolysis vapour derived from Napier grass over microporous and mesoporous ZSM-5 catalysts. It evaluates effect of process variables such catalyst–biomass ratio and catalyst type in a vertical fixed bed pyrolysis system at 600 °C, 50 °C/min under 5 L/min nitrogen flow. Increasing catalyst–biomass ratio during the catalytic process with microporous structure reduced production of organic phase bio-oil by approximately 7.0 wt%. Using mesoporous catalyst promoted nearly 4.0 wt% higher organic yield relative to microporous catalyst, which translate to only about 3.0 wt% reduction in organic phase compared to the yield of organic phase from non-catalytic process. GC–MS analysis of bio-oil organic phase revealed maximum degree of deoxygenation of about 36.9% with microporous catalyst compared to the mesoporous catalysts, which had between 39 and 43%. Mesoporous catalysts promoted production olefins and alkanes, normal phenol, monoaromatic hydrocarbons while microporous catalyst favoured the production of alkenes and polyaromatic hydrocarbons. There was no significant increase in the production of normal phenols over microporous catalyst due to its inability to transform the methoxyphenols and methoxy aromatics. This study demonstrated that upgrading of Napier grass pyrolysis vapour over mesoporous ZSM-5 produced bio-oil with improved physicochemical properties.

Coeffect of Na+ and Tetrapropylammonium (TPA+) in Alkali Treatment on the Fabrication of Mesoporous ZSM-5 Catalyst for Methanol-to-Hydrocarbons Reactions

This investigation focused on the study of formation mechanism for highly mesoporous ZSM-5 under the introduction of tetrapropylammonium hydroxide (TPAOH) during NaOH treatment. Determined based on N2 sorption, transmission electron spectroscopy, scanning electron spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, inductively coupled plasma atomic emission spectroscopy, and 29Si magic-angle spinning nuclear magnetic resonance characterizations, increased mesoporosity, crystallinity, and surface integrity for the desilicated ZSM-5 were found after TPAOH introduction. This protective effect of tetrapropylammonium (TPA+) on desilication was reflected by increased surface SiO2/Al2O3 ratios with increased concentrations of TPA+. TPA+ was first confirmed to be mainly adsorbed on the Si(4Si, 0Al) sites to provide a protective effect. Na+ played an indispensable role in the induced desilication during alkali treatment. The co-effect of protective desilication from TPA+ and preferential desilicatio...

Study on the synthesis and application of mesoporous nanocrystal HZSM-5 for the catalytic cracking of used cooking vegetable oil in Vietnamese restaurants for green diesel

Mesoporous nanocrystal HZSM-5 were successfully synthesized by hydrothermal crystallization during 24 h, at 130 °C with CTAB and TPABr as the templates. The template removing process of as-synthesized sample was studied by TG/DSC. Characterization by modern techniques as XRD, SEM, TEM and TPD-NH3 has showed that the obtained catalyst is highly crystalline with uniformly nanocrystal size. This product has mesoporous sieves which are neatly ordered with diameters around 30 A high BET surface area of 495 m2/g and great acidity. These advantages give the mesoporous nanocrytal ZSM-5 catalyst the applicability in the process of cracking waste oil for green fuel due to the shape—selective advantage for large size molecules in waste vegetable oil. The results of waste vegetable oil catalytic cracking reaction has officially confirmed this identification. The production of green diesel has good quality, meets the technical and environmental standards.

Effect of (Si+Al)/CTAB ratio on crystal size of mesoporous ZSM-5 structure over methanol-to-olefin reactions

Mesoporous ZSM-5 catalysts were prepared with different (Si+Al)/CTAB (cetyltrimethylammonium bromide) molar ratios and their applications in methanol-to-olefin (MTO) reactions were studied at various reaction conditions. It was found that methanol conversion and selectivity to light olefins showed a volcano-type dependency on (Si+Al)/CTAB molar ratios. The highest initial methanol conversion and selectivity of light olefins, catalyst stability were obtained over (Si+Al)/CTAB molar ratio of 15 due to its moderate crystal size with hierarchical structure. A higher C3=/C2= ratio was obtained over mesoporous ZSM-5 catalysts, which was ascribed to high Si/Al ratio and low diffusion hindrance of hierarchical structure.