Commercial ZSM-5 Research Articles

Sustainable Catalytic Process for Fructose Dehydration using Dicationic Ionic Liquid Assisted ZSM-5 Zeolite

ABSTRACT In this work, a uniquely designed imidazolium-based dicationic ionic liquid (IL) was synthesized as a greener template and applied for the synthesis of ZSM-5 zeolite as a heterogeneous catalyst for the dehydration of fructose to 5-hydroxymethylfurfural (HMF). Characterization results confirmed that due to the presence of dicationic IL as template, effective interactions and structural alterations occurred during the construction of zeolitic framework wherein the vertices of ZSM-5 consisting of Al or Si and O elements were assumed to be bonded between the vertices of dicationic IL-assisted zeolite ZSM-5 catalyst. This resulted in superior structural advantages such as highly crystalline nature and stability as well as variation in mesopores when compared to commercial ZSM-5. Additionally, various reaction variables were investigated wherein synthesized dicationic IL-assisted ZSM-5 zeolite catalyst in the presence of [BMIm][Cl] as solvent demonstrated 95% conversion of fructose and 67.2% yield of HMF at 110°C within 90 min. The altered surface area and porous nature of synthesized ZSM-5 due to the presence of dicationic IL as template was responsible for the enhanced catalytic performance under mild reaction conditions. Most significantly, being a solid catalyst, the newly developed dicationic IL-assisted zeolite ZSM-5 catalyst showed recyclability for four recycles.

Gas-phase etherification of cyclopentanol with methanol to cyclopentyl methyl ether catalyzed by zeolites

Symmetric ethers can be synthesized through the acid-catalyzed self-etherification of biomass-derived alcohols. However, synthesis of asymmetric ethers via catalytic cross-etherification of alcohols is limited by poor selectivity. Herein, we developed an efficient zeolite-catalyzed one-step synthesis of valuable asymmetric cyclopentyl methyl ether (CPME) using gas-phase reaction of bio-based cyclopentanol and methanol. Among different medium- (FER, MCM-22, ZSM-5) and large-pore (BEA, MOR, USY) aluminosilicate zeolites, commercial ZSM-5 catalysts with 2D system of intersecting channels are markedly more selective to CPME. The targeted CPME was produced with a selectivity of 83 % and a yield higher than 80 % over the ZSM-5 catalysts with Si/Al ratios ranging from 15 to 40. Decrease in Si/Al ratio in ZSM-5 enhanced the conversion value, while not affecting the selectivity. FTIR study of the step-by-step adsorption of both reactants in ZSM-5 evidenced the Rideal-Eley mechanism with cyclopentanol adsorbed on acid sites. Therefore, heterogeneously catalyzed gas-phase cross-etherification of renewable cyclopentanol and methanol is a promising process for large-scale applications thanks to its mild operating conditions, high yields and selectivity when using commercial ZSM-5 zeolites as catalysts.

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.

Fast and Selective Solvent-Free Branching of Unsaturated Fatty Acids with Hierarchical ZSM-5

Branched fatty acids are of great interest in the oleochemical industry for many high-end applications due to their interesting physicochemical properties. In the last decades, research has focused mainly on the use of ferrierite (FER) as catalyst for the isomerization of fatty acids into these branched fatty acids. With the use of FER, high yields of branched fatty acids can be obtained. FER is however expensive, and additives are necessary to obtain a high selectivity toward branched fatty acids. In this letter, we focus on the use of ZSM-5, a much cheaper zeolite, which has been extensively studied in the past for other reactions. Five commercial ZSM-5 samples and one hierarchical ZSM-5 sample were tested for the isomerization of fatty acids into branched fatty acids. The results clearly show that the accessibility of Bronsted acid sites is of utmost importance for their catalytic activity. Thanks to the introduction of mesopores in the zeolite crystals of ZSM-5, creating a hierarchical zeolite, a superior catalyst was obtained with a multifold activity increase, without compromising in branched fatty acid selectivity, that is capable of competing against the state-of-the-art FER zeolite.

A kinetic study on the methanol conversion to dimethyl ether over H-ZSM-5 zeolite

The intrinsic kinetics of the methanol dehydration to dimethyl ether (DME) over commercial ZSM-5 zeolite is studied both theoretically and experimentally to establish the rate equation of the process. A set of kinetic models based on Langmuir–Hinshelwood (L–H) and Eley–Rideal (E–R) formalism is proposed for the methanol conversion to DME. The experimental verification of the developed models reveals an essential correspondence between the L–H kinetics and the experimental data. In contrast, E–R models provide an insufficient description of the methanol dehydration kinetics. In the frame of L–H formalism, it is shown that both, the associative and dissociative, mechanisms of the methanol dehydration are acceptable in the experimental scenario studied. The discrimination of the established models to choose the most realistic one is performed by comparing the estimated activation energies and adsorption enthalpies with the literature data.

Evaluation of post synthesis treatments over commercial ZSM-5 zeolite in the reaction route of oleic acid esterification with methyl acetate

The objective of this work was to evaluate the influence of post-synthesis treatments applied on high ratio Si/Al commercial ZSM-5 zeolite on its properties and catalytic activity in oleic acid esterification with methyl acetate. Treatments as acidification, desilication, ion exchange and mechanical and ultrasound-assisted impregnation tungsten oxide were applied. The catalysts were properly characterized and the esterification reactions were performed at 240 °C, 1:10 oleic acid:methyl acetate molar ratio and 10% (m/m) catalyst concentration. Properties of the catalysts were significantly changed by the applied treatments, resulting in different yields and isomers distribution of cis and trans esters. The highest ester yield, equal to 66.71%, was obtained with zeolite subjected to ion exchange. This catalyst also provided an equal distribution between the two isomers. It was proposed, based on kinetic experiments, a mechanism for the reaction consisting of isomerization of oleic acid to elaidic acid followed by esterification of both fatty acids.

Rapid direct synthesis of nano-H-ZSM-5 from leached illite via solid-like-state conversion-based crystallization

The direct synthesis of H-ZSM-5 catalysts from natural aluminosilicate clays is important for the conversion of raw clay resources to high-value-added products. Herein, the solid-like-state conversion was used to directly prepare nano-H-ZSM-5 with uniform morphology and particle size (~300 nm) from leached illite (ISR) as both Si and Al source. Crystallization kinetics indicated that the reactivity of ISR is similar to that of commercially fabricated products and ISR could be rapidly (within 5 h) converted into nano-H-ZSM-5, the crystallinity, morphology, and crystal size of which were strongly affected by the amount of tetrapropylammonium hydroxide (TPAOH). Additionally, the residual Al of ISR uniformly intruded the H-ZSM-5 framework to provide active sites for the methanol-to-aromatics reaction. The catalytic performance stability and BTX selectivity of nano-H-ZSM-5 for this reaction surpassed those of a commercial ZSM-5 catalyst because of the synergistic effect among the specific surface area and volume of micropores, uniform morphology and particle size, and homogeneously distributed acidic sites. This rapid, efficient, and cleaner synthesis reported herein was shown to have no necessity of ion exchange with ammonium salts, to be H-form of ZSM-5 as well as improve the productivity of HZSM-5 catalysts. And consequently, it is expected to reduce the cost of synthesis and provide an opportunity for the comprehensive development and utilization of illite clay resources.

Using the ash of common water reeds as a silica source for producing high purity ZSM-5 zeolite microspheres

Abstract Utilizing of ash extracted from Iraqi common water reeds as an inexpensive effective silica source in the preparation of ZSM-5 zeolite was investigated for the first time in the present work. This study was conducted using a hydrothermal treatment at autogenous pressure. The molar content of silica (17.84–26.76), sodium oxide (1.71–2.4), water (76.92–304.6), organic template (0.55–2.73), organic solvent (23.46–140.76), and synthesis conditions (crystallization time (24–72 h) and temperature (130–180 °C)) were investigated to obtain high purity ZSM-5 zeolite microspheres. The zeolite samples were characterized using X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive Analysis by X-Ray (EDAX), N2 adsorption/desorption isotherms, Thermogravimetric Analyzer (TGA), and Fourier transform infrared spectroscopy (FTIR). XRD pattern of all synthesized samples was compared to XRD pattern of the commercial ZSM-5 zeolite. This work allows using locally available solid waste resulted from a dry natural plant as an inexpensive silica source without using an external source of silica. Also, this is the first report of the direct synthesis of a high purity ZSM-5 zeolite microspheres from common water reeds ash containing highly reactive silica. A gel composition of 2Na2O: 26.76SiO2: Al2O3: 2.73TPAOH: 23.46EtOH: 304.6H2O gave an outstanding final product of ZSM-5 zeolite microspheres at 180 °C and 27 h. This high crystallinity ZSM-5 zeolite porous microspheres possess Si/Al ratio of 17, a crystal size of 61.419 nm, BET surface area of 277.482 m2/g, a total pore volume of 0.1659 cm3/g, micropore volume of 0.1131 cm3/g, pore width of 5.28 nm, and hierarchical factor of 0.14.

Platelike MFI Crystals with Controlled Crystal Faces Aspect Ratio.

Zeolite crystals offering a short diffusion pathway through the pore network are highly desired for a number of catalytic and molecule separation applications. Herein, we develop a simple synthetic strategy toward reducing the thickness along the b-axis of MFI-type crystals, thus providing a short diffusion path along the straight channel. Our approach combines preliminary aging and a fluoride-assisted low-temperature crystallization. The synthesized MFI crystals are in the micrometer-size range along the a- and c-axis, while the thickness along the b-axis is a few tens of nanometers. The synthesis parameters controlling the formation of platelike zeolite are studied, and the factors controlling the zeolite growth are identified. The synthesis strategy works equally well with all-silica MFI (silicalite-1) and its Al- and Ga-containing derivatives. The catalytic activity of platelike ZSM-5 in the methanol-to-hydrocarbons (MTH) reaction is compared with a commercial nanosized ZSM-5 sample, as the platelike ZSM-5 exhibits a substantially extended lifetime. The synthesis of platelike MFI crystals is successfully scaled up to a kilogram scale.

Upgrading of biomass-derived liquids in a biorefinery context: Hydroisomerization and fluid catalytic cracking of heavy naphtha on bench and pilot scale

The development of efficient processes for the upgrading of low value bio-derived liquid intermediates to high added value products in biorefineries is critical for the establishment of a robust and competitive bio-based economy. We show in this paper that low quality surrogate heavy naphtha, representative of biofuels from thermochemical biomass conversion processes, can be efficiently converted to high quality fuel and chemicals (olefins) via hydroisomerization and catalytic cracking, respectively. Hydroisomerization over a low loading 0.1 wt% Pt/ZSM-5 catalyst leads to the conversion of normal paraffins to C5-C8 isoparaffins with limited cracking, and produces a fuel with higher octane and lower cetane number, suitable for use in future powertrains such as HCCI engines. Catalytic cracking of the naphtha on a commercial ZSM-5 based FCC catalyst results in the production of a significant amount of olefins at 600 °C, primarily propylene followed by ethylene, n-butene, pentene and i-butene. Both processes are validated on pilot scale. Some differences observed between bench and pilot scale results are due to scalability phenomena and different reaction conditions. Still, excellent agreement with regards to the composition of the products at similar conversion level exists, demonstrating the scalability and applicability of these upgrading processes in thermochemical biorefineries.

Highly efficient selective oxidation of 2-methylnaphthalene to vitamin K3 over mesoporous Al/Ti-SBA-15 catalysts: The effect of acid sites and textural property

Catalytic oxidation of 2-methylnaphthalene to 2-methyl-1,4-naphthoquinone (vitamin K3) is a significant pathway to produce vitamin groups K. High pollution and low-productivity of the traditional method require a greener catalyst and process. In this work, Al/Ti-SBA-15 with different nSi/nAl and nSi/nTi ratios were hydrothermally prepared in mild acidic condition and tested in partial oxidation of 2-methylnaphthalene. Commercial zeolites NaY, β and ZSM-5 were applied to investigate the influence of mass transfer resistance and acidity on catalytic performance. Catalysts were characterized by XRD, N2 adsorption-desorption, TEM, NH3-TPD, FTIR and Py-FTIR. We have found that the 2-methylnaphthalene conversion and vitamin K3 selectivity depend strongly on the mesoporous structure as well as Brönsted acid concentration and strength. Irregular micropores and strong acidity will accelerate the cleavage of C = C in aromatic rings, leading to the production of phthalic anhydride. DFT calculation reveals that incorporation of aluminum in SBA-15 can reduce the energy gap, facilitating the electron transfer. And as a consequence of the substitution of Al in tetrahedral positions in SBA-15, Al-SBA-15 (10) gives the best result with 72% yield to vitamin K3. This catalyst markedly reduces the activation energy due to the modified activated center. Repeated experiments recommend that Al-SBA-15 is a steady and high-efficiency catalyst for the production of vitamin K3.

Characterization of ZSM-5 monolith as solid sorbent for Ni2+ removal

Solid wastes exhibit excellent prospects in the removal of heavy metals from contaminated water. However, raw solid waste materials usually show mediocre uptake efficiency, it is imperative to functionalize or transform them into new solid waste-based materials. The present work provides a novel technique by utilization of silica fume waste for Ni2+ removal from wastewater. The sorbent was prepared by in-suit conversion of amorphous silica fume based geopolymer into monolithic ZSM-5 via polycondensation and seed-induced hydrothermal treatment process. The adsorption behavior of Ni2+ in aqueous solution onto the as-synthesized monolithic ZSM-5 was investigated. The adsorption experiment data fitted well with the pseudo-second-order kinetic model and Langmuir isotherm model. Thermodynamic parameters including ΔH, ΔG and ΔS were calculated from the temperature-dependent sorption isotherms. All the results confirmed that the sorption of Ni2+ onto monolithic ZSM-5 was a spontaneously endothermic chemisorption process, demonstrating the removal of Ni2+ from wastewater using monolithic ZSM-5 was feasible. The adsorption capacity of Ni2+ onto monolithic ZSM-5 was 13.22 mg/g at 25 °C, which was a competitive result compared with similar adsorbents and commercial ZSM-5 powders.

The synthesis of Cu/SAPO-34 catalysts and evaluation ability of NOx treatment by NH3-SCR with Cu/ZSM-5 catalyst using commercial ZSM-5 as support

SAPO-34 molecular sieves were synthesized under hydrothermal conditions using different combinations of tetraethyl ammonium hydroxide (TEAOH), morpholine (Mor), and triethylamine (TEA) as organic structure-directing agents and economical silicon source by colloidal silica LUDOX AS-30. The products were characterized by X-ray diffraction, Field Emission Scanning Electron Microscopes, Energy-dispersive X-ray spectroscopy, NH3 temperature - programmed desorption, N2 adsorption-desorption. Electron paramagnetic resonance technique was applied to identify isolated Cu2+ ions in the framework. Although materials with the same chabazite framework structure are obtained, they possess different physicochemical properties, especially crystal size and acidity. Catalytic performances of Cu/SAPO-34 and Cu/ZSM-5 using commercial ZSM-5 as support with the loading of 3 wt% prepared by liquid ion-exchange method was performed for selective catalytic reduction (SCR) of NOx with NH3.

The effect of hierarchical single-crystal ZSM-5 zeolites with different Si/Al ratios on its pore structure and catalytic performance

Hierarchical single-crystal ZSM-5 zeolites with different Si/Al ratios (Hier-ZSM-5-x, where x = 50, 100, 150 and 200) were synthesized using an ordered mesoporous carbon-silica composite as hard template. Hier-ZSM-5-x exhibits improved mass transport properties, excellent mechanical and hydrothermal stability, and higher catalytic activity than commercial bulk zeolites in the benzyl alcohol self-etherification reaction. Results show that a decrease in the Si/Al ratio in hierarchical single-crystal ZSM-5 zeolites leads to a significant increase in the acidity and the density of micropores, which increases the final catalytic conversion. The effect of porous hierarchy on the diffusion of active sites and the final catalytic activity was also studied by comparing the catalytic conversion after selectively designed poisoned acid sites. These poisoned Hier-ZSM-5-x shows much higher catalytic conversion than the poisoned commercial ZSM-5 zeolite, which indicates that the numerous intracrystalline mesopores significantly reduce the diffusion path of the reactant, leading to the faster diffusion inside the zeolite to contact with the acid sites in the micropores predominating in ZSM-5 zeolites. This study can be extended to develop a series of hierarchical single-crystal zeolites with expected catalytic performance.

A Cationic Oligomer as an Organic Template for Direct Synthesis of Aluminosilicate ITH Zeolite

There are a large number of zeolites, such as ITH, that cannot be prepared in the aluminosilicate form. Now, the successful synthesis of aluminosilicate ITH zeolite using a simple cationic oligomer as an organic template is presented. Key to the success is that the cationic oligomer has a strong complexation ability with aluminum species combined with a structural directing ability for the ITH structure similar to that of the conventional organic template. The aluminosilicate ITH zeolite has very high crystallinity, nanosheet-like crystal morphology, large surface area, fully four-coordinated Al species, and abundant acidic sites. Methanol-to-propylene (MTP) tests reveal that the Al-ITH zeolite shows much higher selectivity for propylene and longer lifetime than commercial ZSM-5. FCC tests show that Al-ITH zeolite is a good candidate as a shape-selective FCC additive for enhancing propylene and butylene selectivity.

Modified seeding method to produce hierarchical nanocrystalline ZSM-5 zeolite

A series of ZSM-5 nano-zeolites with hierarchical porosity was prepared by a modified seed-induced method using a mixture of silicate-1 and commercial Na-ZSM-5 zeolite as a seed to reduce the production cost. The XRD and FTIR results proved that the pure ZSM-5 phase with a high degree of crystallinity was crystallized. Furthermore, the synthesized samples using a mixture of silicate-1 and commercial ZSM-5 as a seed exhibited more dealumination during the hydrothermal aging process, resulting in a higher Smeso/SBET ratio than other samples and the highest ratio of Brönsted/Lewis acid sites among all the samples. The SEM and BET results also confirmed that the final pH after the synthetic process extensively affected the morphology, specific area and pore volume of products. The purposed method by employing a lower amount of the organic template and silica source might lead to a more economical and environmentally friendly approach for the hierarchical ZSM-5 zeolite production to benefit the relevant industries.

Naphthalene and Alkyl Naphthalene from Catalytic Fast Pyrolysis of Biomass Over ZSM-5 Aggregates

Seed-induced synthesis of ZSM-5 aggregates was carried out without organic templates. The prepared ZSM-5 aggregates were used upgrading polar sawdust-derived pyrolytic vapors for the selective production of naphthalene and alkyl naphthalene. Pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) experiments were conducted to analyze the pyrolytic product distribution and evaluate the catalyst performance. Due to the mesopores and proper acidities of ZSM-5 aggregates, the yield of naphthalene and methylnaphthalene over ZSM-5 aggregates were 36.0 and 123.7 mg/g, which were 2.7 and 2.6 times of those respectively over the commercial ZSM-5. The total selectivities of naphthalene and alkyl naphthalene could reach 61.56%.

Direct Synthesis of Dimethyl Ether from Syngas Over Hybrid Catalyst with Hierarchical ZSM-5 as the Methanol Dehydration Catalyst

Commercial ZSM-5 zeolites were submitted to alkaline treatment in order to prepare hierarchical ZSM-5 zeolites with hierarchical porosity and moderate acidity. Hybrid bifunctional catalyst comprising a CuO-ZnO-Al₂O₃ (CZA) and zeolite was prepared by physical mixing method, used for the direct synthesis of dimethyl ether (DME) from syngas. The correlation between the textural and acid properties of the zeolite and the catalytic performance of hybrid catalyst has been assessed from the combined results of N₂ physisorption, FTIR of adsorbed pyridine, elemental analysis ICP, online-GC and other characterization techniques. The results indicate that the hybrid catalyst with hierarchical ZSM-5 zeolite exhibits higher activity and stability than that with parent ZSM-5 zeolite due to the synergy effect of moderated acidity and enhanced mass transport capability of the hierarchical ZSM-5 sample. Under 260 °C, 2.0 MPa and 3600 h-1, the conversion of CO and the DME selectivity to DME over hybrid catalyst CZA-ZSM-5(25)-A achieved 65.2% and 67.8%, respectively.

Preparation of HZSM-5 catalysts with different ratios of structure directing agents and their effects on the decomposition of exo-tetrahydrodicyclopentadiene under supercritical conditions and coke formation

Zeolite catalysts (ZSM-5) were synthesized using different ratios of structure directing agents (SDA) and Si/Al, and the synthesized ZSM-5 samples were used in the endothermic decomposition reaction of exo-tetrahydrodicyclopentadiene (exo-THDCP). The ZSM-5 synthesized with a 6.0:100 SDA/SiO2 ratio and Si/Al ratio of 20 (S20/P6.0) showed higher mesoporosity than those of the other synthesized and commercial ZSM-5 catalysts. The decomposition reaction of exo-THDCP using the S20/P6.0 catalyst yielded the highest conversion of 58.4% after 65 min, whereas the commercial catalyst rapidly became deactivated and exhibited only 31.2% conversion, which was the same conversion obtained without the catalyst. The coke analysis results indicated that the ratio of mesopore to micropore volume of the catalyst was a major factor in determining the amount of internal and external coke produced in the catalyst. Moreover, the mesopore/micropore volume ratio affected the composition of soluble coke.

In-situ production of valuable aromatics via pyrolysis of waste polypropylene using commercial catalyst ZSM-5

Waste polypropylene has been subjected to pyrolysis followed by in-situ aromatization in a specially designed semi batch reactor at the temperature ranging from 500 - 800°C. The molecules of interest are valuable aromatics benzene, toluene, ethyl benzene and xylene (BTEX) which appeared highest amount in the liquid mixture. The catalyst used is commercial ZSM-5 (30:1). The catalytic pyrolysis of PP is studied in a semi batch reactor in two different phases, keeping the catalyst in the liquid phase (L-type) and liquid and vapor phase/multiphase (M-type), respectively. The BTEX yield is enhanced significantly using multiphase catalytic pyrolysis of polypropylene. The catalytic performance of ZSM-5 catalyst for PP pyrolysis is evaluated with respect to target aromatics BTEX. The thermal pyrolysis of PP produced maximum liquid yield of 80.56 wt. % at a temperature of 700°C. The commercial catalysts ZSM-5 produced highest liquid yield of 86.3 wt. % for liquid phase (L-type) pyrolysis. The BTEX yield is significantly increased from 30.9 wt.% for thermal pyrolysis to 53.09 wt. % for catalytic multiphase/M-type pyrolysis. Almost 72 % increase in BTEX yield is recorded for catalytic multiphase/M-type pyrolysis in comparison to thermal process. The pyrolysis oil is analyzed using GC-FID, carbon residue test and other fuel testing methods to examine the suitability of its end use and aromatic content.