Commercial ZSM-5 Zeolite Research Articles

Tuning the morphology and textural properties of ZSM-5 additive for co-cracking of waste plastics with vacuum gas oil to light olefins

Typical cracking catalysts, called equilibrium catalyst (E-Cat) are ultra-stable Y (USY) zeolite often used with 15% commercial ZSM-5 zeolite additive (ZSM-5(COM)) to boost olefin yield. In this study, similar additive zeolites with different pore sizes and acidic character were synthesized by rapid ageing of precursor solution and used in the co-cracking of low-density polyethylene (LDPE) and heavy vacuum gas oil (HVGO). Three ZSM-5 zeolites additives with Si/Al ratio 25 (ZSM-5(25)), 50 (ZSM-5(50)) and 75 (ZSM-5(75)) were synthesized and combined with E-Cat to form E-Cat/ZSM-5(25), E-Cat/ZSM-5(50) and E-Cat/ZSM-5(75) respectively. The E-Cat/ZSM-5(50) has slightly better endothermic conversion (cracking) of a mixture of dissolved LDPE and HVGO into H2, C1 to C4 gases and C2-C4 light olefins (total conversion of E-Cat 80.0%, E-Cat/ZSM-5(COM) 75.0% and E-Cat/ZSM-5(50) 83.7% respectively), with different gas, liquid and coke distributions. The E-Cat/ZSM-5(75) has 81% conversion, and highest yield of light olefins (38.4%). Structural (surface area, pore size) and chemical (acid sites) characteristics of the synthetized ZSM-5(75) zeolite explain the observed higher light olefin selectivity by different and competing catalytic routes. The ZSM-5(75) has demonstrated to be a good zeolite additive for converting dissolved plastic in HVGO into light olefins.

Hydrocracking of hydrotreated light cycle oil for optimizing BTEX production: a simple kinetic model

Abstract The effect of the experimental conditions on the hydrocracking (HCK) of a hydrotreated light cycle oil (HDT LCO) was studied in this work. The catalyst tested was a 50/50 weight mixture of nickel-molybdenum-phosphorous on alumina (NiMo/Al2O3) and a commercial ZSM5 zeolite (HCK 50/50). The experimental conditions tested were 340, 350, 360, and 370 °C; 7.5 MPa; 0.9, 1.2, 1.5, and 1.8 h−1 LHSV, and H2/HC of 752 m3/m3. Two phases: gas and liquid, were obtained as HDK products. The gas phase consisted mostly of C1–C5 paraffins, iso-paraffins, and olefins. The liquid phase was characterized by GC-PIONA and was distributed in lumps as follows: NAPA by C11 to C13-naphthalenes; TET by C11 to C13-tetralins; IND by C9 to C13-indanes and indenes; AKB by C9 to C13-alkylbenzenes; BTEX by benzene, toluene, ethylbenzene, and xylenes; NAPE by C9 to C13-naphthenes; and PIP by C3 to C14 paraffin, iso-paraffin, and olefin type hydrocarbons. Using this classification, the results showed that increments in temperature and decrements in LHSV produced increments in the formation of gases, PIP, BTEX, and NAPE. At the same conditions, AKB, TET, NAPA, and IND decreased sharply. TET and NAPA derivatives were no longer present at high temperatures (360–370 °C). It seemed to be a limit of the BTEX formation directly related to the TET and IND presence, and it did not seem to depend on the transalkylation process of AKB hydrocarbons. Instead, AKB hydrocarbons were directly correlated to NAPE hydrocarbon formation by hydrogenation. A kinetic model was prepared. The model presented correlation coefficients higher than 98 %. The kinetic model that was made predicted that neither increasing the temperature nor lowering the LHSV would improve the BTEX formation when departing from this feedstock.

Analyzing the Effect of Zr, W, and V Isomorph Framework Substitution on ZSM-5 and Beta Zeolites for Their Use as Hydrocarbon Trap.

This work evaluates the effect on the adsorption and desorption kinetics of propene and toluene (used as probe molecules for vehicle cold-start emissions) of the isomorph framework substitution of Zr, W, and V on commercial ZSM-5 and beta zeolites. TG-DTA and XRD characterization data indicated that: (i) Zr does not modify the crystalline structure of the parent zeolites, (ii) W develops a new crystalline phase, and (iii) V causes the breakdown of the zeolite structure during the aging step. The CO2 and N2 adsorption data revealed that the substituted zeolites present a narrower microporosity than pristine zeolites. As a consequence of all these modifications, the modified zeolites feature different adsorption capacity and kinetics of HCs, so, different hydrocarbon trapping ability than pristine zeolites. However, a clear correlation is not observed between the changes in the porosity/acidity of zeolites and the adsorption capacity and kinetics, which depends on: (i) the zeolite (ZSM-5 or BEA), (ii) the hydrocarbon (toluene or propene), and (iii) the cation to be inserted (Zr, W, or V).

Oxidative Carbonylation of Methane to Acetic Acid over Commercial Rodium-Modified ZSM-5 Zeolites

Oxidative Carbonylation of Methane to Acetic Acid over Commercial Rodium-Modified ZSM-5 Zeolites

Exhaust emission control of SI engines using ZSM-5 zeolite supported bimetals as a catalyst synthesized from coal fly ash

This paper synthesizes ZSM-5 zeolite from coal fly ash and uses it as a catalyst for reduction of NOx emissions in gasoline powered engine. It suggests a mono and bimetallic doped zeolite coated in honeycomb structure cordierite monolith for effectively reducing the NOx emissions. The synthesized ZSM-5 zeolite was subjected to SEM, XRF and XRD analysis and compared with commercial ZSM-5 zeolite. The experimental study of measuring emissions using AVL DI-gas analyzer on a Tata nano twin-cylinder spark ignition engine clearly indicated that in-house made bimetallic of Ce.Cu-ZSM5 and Ce.Fe-ZSM5 were able to reduce the NOx by 69 % and 75 % at 16 kW. The NOx reductions were much better than those of the commercial catalytic converters.

Counting the Acid Sites in a Commercial ZSM-5 Zeolite Catalyst.

This work investigates the acid sites in a commercial ZSM-5 zeolite catalyst by a combination of spectroscopic and physical methods. The Brønsted acid sites in such catalysts are associated with the aluminum substituted into the zeolite lattice, which may not be identical to the total aluminum content of the zeolite. Inelastic neutron scattering spectroscopy (INS) directly quantifies the concentrations of Brønsted acid protons, silanol groups, and hydroxyl groups associated with extra-framework aluminum species. The INS measurements show that ∼50% of the total aluminum content of this particular zeolite is extra framework, a conclusion supported by solid-state NMR and ammonia temperature-programmed desorption (TPD) measurements. Evidence for the presence of extra-framework aluminum oxide species is also seen in neutron powder diffraction data from proton- and deuterium-exchanged samples. The differences between results from the different analytical methods are discussed, and the novelty of direct proton counting by INS in this typical commercial catalyst is emphasized.

Stabilization of Extra-Large-Pore Zeolite by Boron Substitution for the Production of Commercially Applicable Catalysts.

Stable extra-large-pore zeolites are desirable for industrial purposes due to their ability to accommodate bulky reactants and diffusion through channels. Although there are several extra-large pore zeolites reported, stable ones are rare. Thus, their stabilization is a feasible strategy for industrial applications. Here, an extra-large-pore zeolite EWT with boron substitution is presented, and the resulting zeolite B-RZM-3 increased the thermal stability from 600 °C in its silica form to 850 °C. The crystal structure, determined by combining continuous rotation electron diffraction (cRED) and powder X-ray diffraction (PXRD), shows that B atoms preferentially substitute the interrupted (HO)T(OT)3 (Q3 ) sites and are partially converted into 3-coordination to relax framework deformation upon heating. After Al-reinsertion post-treatment, Al-B-RZM-3 shows higher ethylbenzene selectivity and ethylene conversion rate per mol acid site than commercial ZSM-5 and Beta zeolite in benzene alkylation reaction. Synthesizing extra-large-pore zeolite in borosilicate form is a potential approach to stabilize interrupted zeolites for commercial applications.

Direct synthesis of aluminosilicate ITH zeolite in the presence of a small organic template

Despite very successful synthesis of many pure silica or germanosilicate zeolites, there are still challenges for direct synthesis of their aluminosilicate forms. As a typical example, it is easy to synthesize germanosilicate ITH, but difficult for direct synthesis of its aluminosilicate form. Recently, cationic oligomer has been successfully templated for direct formation of aluminosilicate ITH, but relatively complex steps for controlling molecular weight of the cationic oligomer strongly hinder the practical production of zeolite products. Herein, it is shown an alternative route for direct synthesis of aluminosilicate ITH zeolite in the presence of a small organic template with both structural directing ability for the ITH structure and strong interaction ability to aluminum species. Characterizations of the zeolite products with Si/Al ratios from 46 to 148 show high crystallinity, nanosheet-like crystal morphology, large microporous surface area (338 m2/g), high micropore volume (0.16 cm3/g), four-coordinated Al species, controllable acidic sites, and extraordinary hydrothermal stability (hydrothermal aging at 800 °C for 5 h with 10% water steaming). Catalytic tests in methanol-to-propylene (MTP) show that the aluminosilicate ITH zeolite has higher selectivity for propylene than that of commercial ZSM-5 zeolite with similar Si/Al ratio, which provides a candidate catalyst for MTP reaction in the near future.

Pore Blocking by Phenolates as Deactivation Path during the Cracking of 4-Propylphenol over ZSM-5

Cracking of propyl side chains from 4-propylphenol, a model compound for lignin monomers, is studied for a commercial ZSM-5 zeolite catalyst. The decline of 4-propylphenol conversion with time on stream can be delayed by co-feeding water. FTIR spectroscopy shows the formation of chemisorbed phenolates during reactions and significant amounts of phenolics are detected by GC-MS of the extract from the spent catalysts. Thus, chemisorbed phenolates are identified as the main reason for deactivation in the absence of water. Regardless of the amount of co-fed water, substituted monoaromatics and polyaromatic species are formed. Comprehensive characterization of the spent catalysts including Raman and solid-state 27Al NMR spectroscopy, and thermogravimetric analysis points to a combination of deactivation processes. First, phenolates bind to Lewis acid sites within the zeolite framework and hinder diffusion unless they are hydrolyzed by water. In addition, light olefins created during the cracking process react to form a polyaromatic coke that deactivates the catalyst more permanently.

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.

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.

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.

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.

Seed-Assisted Synthesis and Catalytic Performance of Nano-sized ZSM-5 Aggregates in a One-Step Crystallization Process

Hierarchical nano-sized ZSM-5 aggregates were successfully synthesized via a seed-assisted method in the presence of cetyltrimethylammonium bromide (CTAB) through a facile one-step crystallization process. Commercial ZSM-5 zeolites with a SiO2/Al2O3 ratio comparable to that of ZSM-5 products were treated with alkali and used as the seed particles. The influences of crystallization conditions were investigated, and the possible synthesis mechanism was proposed. ZSM-5 zeolites with different amounts of CTAB added were characterized using many techniques and evaluated in toluene alkylation with methanol. The results showed that a trace amount of CTAB significantly promoted the crystallization of ZSM-5 zeolite, with the morphology changing from hexagonal-shape crystals to uniform spherical aggregates. CTAB may act as the structure-directing agent and assemble the primary crystallites to generate hierarchical ZSM-5 aggregates. The ZSM-5 zeolite with the smallest primary particles of 50–80 nm exhibited large specific surface area, abundant mesopores, and the greatest microporosity. The hierarchical nano-sized ZSM-5 aggregate showed higher toluene conversion and a longer lifetime without compromising the selectivity to xylene and p-xylene in toluene alkylation with methanol.

Hydrotreating of Guaiacol and Acetic Acid Blends over Ni2P/ZSM-5 Catalysts: Elucidating Molecular Interactions during Bio-Oil Upgrading.

Catalytic hydrodeoxygenation (HDO) is an effective technology for upgrading pyrolysis bio-oils. Although, in the past years, this process has been extensively studied, the relevance of the cross-reactivity between the numerous chemical components of bio-oil has been scarcely explored. However, molecular coupling can be beneficial for improving the bio-oil characteristics. With the aim of gaining a better understanding of these interactions, this work investigates the catalytic hydrodeoxygenation of mixtures of two typical components of pyrolysis bio-oils: guaiacol and acetic acid. The catalytic tests were carried out employing a bifunctional catalyst based on nickel phosphide (Ni2P) deposited over a commercial nanocrystalline ZSM-5 zeolite. The influence of both hydrogen availability and temperature on the activity and product distribution, was evaluated by carrying out reactions under different H2 pressures (40–10 bar) and temperatures (between 260 and 300 °C). Using blends of both substrates, a partial inhibition of guaiacol HDO occurred because of the competence of acetic acid for the catalytic active sites. Nevertheless, positive interactions were also observed, mainly esterification and acylation reactions, which could enhance the bio-oil stability by reducing acidity, lowering the oxygen content, and increasing the chain length of the components. In this respect, formation of acetophenones, which can be further hydrogenated to yield ethyl phenols, is of particular interest for biorefinery applications. Increasing the temperature results in an increment of conversion but a decrease in the yield of fully deoxygenated molecules due to the production of higher proportion of catechol and related products. Additional experiments performed in the absence of hydrogen revealed that esterification reactions are homogeneously self-catalyzed by acetic acid, while acylation processes are mainly catalyzed by the acidic sites of the zeolitic support.

High efficiency of toluene adsorption over a novel ZIF-67 membrane coating on paper-like stainless steel fibers

A novel microporous ZIF-67 membrane coating on paper-like stainless steel fibers (ZIF-67 membrane/PSSF) was successfully synthesized by a wet layup papermaking-sintering method followed by the seed-induced growth method. The effects of key factors such as crystallization temperature, synthesis time and Hmim/Co2+ (2-methylimidazole/cobalt chloride) molar ratio on the morphology structure of the samples were studied by the modern characterization techniques including SEM, EDX, TEM, XRD, BET, FTIR and TGA, respectively. The experimental result indicated that the as-synthesized ZIF-67 membrane/PSSF was extremely compact with the average membrane thickness of 4.8 μm. And the sample exhibited high BET surface area (440.9 m2/g), uniform pore size (1.881 nm) and large pore volume (0.2096 cm3/g). The adsorption breakthrough experiment of toluene was performed on different bed reactors filled with ZIF-67 membrane/PSSF and granular ZSM-5 zeolites, respectively. The experiment data was well fitted by Yoon–Nelson model, where the values of rate constant in the fixed bed with ZIF-67 membrane/PSSF increased by 32.2% compared with that of commercial ZSM-5 zeolites at the flow rate of 100 mL/min. And the bed pressure drop and length of unused bed (LUB) were dramatically reduced by 39.6% and 16.8% in 3 cm ZIF-67 membrane/PSSF fixed bed. In conclusion, mass transfer efficiency was significantly enhanced based the structured ZIF-67 membrane/PSSF fixed bed, and this new material is a promising adsorptive material for VOCs removal.

Fast synthesis of submicron ZSM-5 zeolite from leached illite clay using a seed-assisted method

Abstract A seed-assisted method enabled the fast synthesis of submicron ZSM-5 from acid-leached illite without the use of any organic templates. In addition, the effects of illite activation temperature, synthesis temperature, synthesis time, Na2O/SiO2 ratio, SiO2/Al2O3, and the amount of commercial seed were investigated. The synthesized zeolite materials were characterized by X-ray diffraction, scanning electron microscopy, and NH3 temperature-programmed desorption. Under these study conditions, submicron-sized ZSM-5 zeolites were synthesized in a relatively short time of 3 h. The relative crystallinity of the ZSM-5 zeolite obtained was up to 115%, and the quartz impurity was kept to a minimum. Aluminium in the framework of zeolite is capable of providing acidic sites. The prepared ZSM-5 zeolite showed a slightly better catalytic performance in toluene disproportionation than ZSM-5 seeds. In addition, different commercial ZSM-5 zeolites could be utilized as seeds, including self-made zeolite crystals.

Selective conversion of methane to aromatic hydrocarbons on large crystallite zeolite catalysts with mesoporous structure

Large crystallite mesoporous MFI (ZSM-5) zeolite was synthesized by using carbon nano-powder as a secondary template. The surface properties, morphological and phase composition of the synthesized material and of the commercial ZSM-5 (Zeolyst) zeolite were studied by nitrogen porosimetry, XRD and scanning electron microscopy. The results showed that the volume of mesopores volume increases with development of a secondary mesoporosity in the structure of zeolite. The obtained zeolite supports were used to prepare molybdenum-containing catalysts for the methane aromatization by solid phase preparation technique. Based on the XPS data, molybdenum particles in these catalysts are characterized by more uniform size distribution. The formation of a secondary pore structure restrains the carbon deposit formation as well as increases the methane conversion and the yield of the aromatic compounds.

Catalytic performance of commercial Cu-ZSM-5 zeolite modified by desilication in NH3-SCR and NH3-SCO processes

In the presented manuscript an influence of the mesoporosity generation in commercial ZSM-5 zeolite on its catalytic performance in two environmental processes, such as NO reduction with ammonia (NH3-SCR, Selective Catalytic Reduction of NO with NH3) and NH3 oxidation (NH3-SCO, Selective Catalytic Oxidation of NH3) was examined. Micro-mesoporous catalysts with the properties of ZSM-5 zeolite were obtained by desilication with NaOH and NaOH/TPAOH (tetrapropylammonium hydroxide) mixture with different ratios (TPA+/OH- = 0.2, 0.4, 0.6, 0.8 and ∞) and for different durations (1, 2, 4 and 6 h). The results of the catalytic studies (over the Cu-exchanged samples) showed higher activity of this novel mesostructured group of zeolitic materials. Enhanced catalytic performance was related to the generated mesoporosity (improved Hierarchy Factor (HF) of the samples), that was observed especially with the use of Pore Directing Agent (PDA) additive, TPAOH. Applied desilication conditions did not influence significantly the crystallinity of the samples (X-ray diffraction analysis (XRD)), despite the treatment for 6 h in NaOH solution, which was found to be too severe to preserve the zeolitic properties of the samples. The modified porous structure and accessibility of acid sites (increased surface acidity determined by temperature programmed desorption of ammonia (NH3-TPD)) influenced the red-ox properties of copper species introduced by ion-exchange method (temperature programmed reduction with hydrogen (H2-TPR). Increased acidity of the micro-mesoporous samples, as well as the content of easily reducible copper species resulted in a significant improvement of Cu-ZSM-5 catalytic efficiency in the NH3-SCR and NH3-SCO processes.