ZSM-5 Catalysts Research Articles

Synthesis of Rh nanoparticles encapsulated in ZSM-5 and its application for methanol to olefin over acid sites with simultaneous production of hydrogen over Rh

Metal-loaded zeolites possess metal and solid acid catalysis and therefore can be applied for complex reactions where different reactions proceed on different type of active sites. The optimization of each active sites, such as amount and strength of active sites, are indispensable to improve the yield of the desired product in complex reaction. On the other hand, in metal-loaded zeolite catalysts, the acid site amount is still difficult to be controlled independently because metal particles may be located on the acid sites, leading to the decrease in the acidity. To realize independent control of the each active sites of metal-loaded zeolite, we herein synthesized Rh nanoparticles encapsulated in ZSM-5 catalysts (Rh@ZSM-5) in a water-in-oil microemulsion solution by modifying the synthesis method for metal nanoparticles encapsulated in zeolite in our previous literature. In this method, the formation of metal nanoparticles encapsulated in amorphous silica was followed by the transformation of amorphous silica into zeolite and thus the amounts of solid acid and metal active sites are expected to be controlled independently. Rh@ZSM-5 was found to possess Rh nanoparticles inside of zeolite and the metal particle size and the amount of the solid acid sites were almost independent of the Rh loadings. Reaction of methanol over Rh@ZSM-5 was carried out to elucidate the bifunctional catalysis and its effect on the product selectivity. During the methanol conversion over Rh@ZSM-5, methanol to olefin reaction over solid acid sites and methanol decomposition over Rh metal proceeded in parallel. Rh@ZSM-5 exhibited the larger yield of propylene and butenes than ZSM-5. It could be because that hydrogen atoms produced in situ over Rh@ZSM-5 effectively inhibited the formation of aromatic intermediates to produce ethylene and aromatic compounds.

Biogasoline production from linoleic acid via catalytic cracking over nickel and copper-doped ZSM-5 catalysts

Catalytic cracking of vegetable oil mainly processed over zeolites, and among all the zeolites particularly HZMS-5 has been investigated on wide range for renewable and clean gasoline production from various plant oils. Despite the fact that HZSM-5 offers a higher conversion degree and boost aromatics yield, the isomerate yield reduces due to high cracking activity and shape selectivity of HZSM-5. Hence, to overcome these problems, in this study the transition metals, such as nickel and copper doped over HZSM-5 were tested for its efficiencies to improve the isoparaffin compounds. The catalysts were screened with linoleic acid in a catalytic cracking reaction conducted at 450 ᵒC for 90 min in an atmospheric condition in batch reactor. Then, the gasoline composition of the organic liquid product (OLP) was analysed in terms of paraffin, isoparaffin, olefin, naphthenes and aromatics (PIONA). The results showed that Cu/ZSM-5 produced the highest liquid yield of 79.1%, at the same time reduced the production of gas and coke to 18.8% and 0.7%. Furthermore, the desired isoparaffin composition in biogasoline increased from 1.6% to 6.8% and at the same time reduced the oxygenated and aromatic compounds to 15.4% and 59.7%, respectively. The linoleic acid as model compound of rubber seed oil, in the catalytic cracking reaction provides a clearer understanding of the process. Besides, the water gas shift (WGS) reaction in catalytic cracking reaction provides insitu hydrogen production to saturate the branched olefin into the desired isoparaffin and the aromatics into naphthenes.

Simultaneous Desulfurization and Denitrification Using La-Ce-V-Cu-ZSM-5 Catalysts in an Electrostatic Precipitator.

Different catalysts were loaded onto the collecting plate of an electrostatic precipitator to achieve the simultaneous removal of multiple pollutants from coal-fired gas. The synergistic desulfurization and denitrification effect of the catalyst and the effect of corona discharge on the activity of the catalyst were studied. The La(6%)–Ce(8%)–V(7%)–Cu(8%)–ZSM-5 catalyst prepared by successive impregnation methods had the optimum simultaneous desulfurization and denitrification efficiency at a roasting temperature of 600 °C. The desulfurization and denitrification rates reached 97.09 and 83.30%, respectively. BET and SEM characterization results showed that the loading of active components and additives improved the pore structure of the molecular sieve, which contributed to the high stability of the catalyst’s internal structure and large surface area, as well as better desulfurization and denitrification efficiency. Corona discharge can significantly improve the catalytic effect.

Controllable alkylation of benzene with mixed olefins for producing C8-C15 aromatics in jet fuel

C8-C15 aromatics are used widely as key components of jet fuel, whereas effectively producing these aromatic components remains a big challenge. We reported the oriented synthesis of C8-C15 aromatic components in jet fuel by alkylation of benzene with mixed ethylene and propylene in vapor-phase over nanosize ZSM-5 (N-ZSM-5) catalyst. The selectivity and yield of aromatics, mainly of carbon number ranging from 8 to 15, could be enhanced by decreasing the particle size of ZSM-5, owing to the faster mass transfer and shorter intraparticle diffusion route for reactants and target products during the reaction process, as well as by increasing the acid strength via decreasing the Si/Al molar ratio, thus improving the alkylation performance conspicuously. In addition, mesopore volume of N-ZSM-5 zeolite showed an increase tendency with decreased particle size, contributing to the carbon chain growth and diffusion of target products. The resultant N-ZSM-5 catalyst showed superior benzene conversion of 40.3%, ethylene and propylene conversion of 99.5% and 99.2%, with aromatic C8-C15 selectivity and yield of 94.8% and 54.9%, respectively, under the optimized reaction conditions.

Ab initio enhanced sampling kinetic study on MTO ethene methylation reaction

The methylation reaction of ethene with methanol over the Brønsted acidic ZSM-5 catalyst is one of the prototype reactions within zeolite catalysis for which experimental kinetic data is available. It is one of the premier reactions within the methanol-to-olefins process and has been the subject of extensive theoretical testing to predict the reaction rates. Herein, we apply, for the first time, first principle molecular dynamics methods to determine the intrinsic reaction kinetics taking into account the full configurational entropy. As chemical reactions are rare events, enhanced sampling methods are necessary to obtain sufficient sampling of the configurational space at the activated region. A plethora of methods is available which depend on specific choices like the selection of collective variables along which the dynamics is enhanced. Herein, a thorough first principle molecular dynamics study is presented to determine the reaction kinetics via various enhanced MD techniques on an exemplary reaction within zeolite catalysis for which reference theoretical and experimental data are available.

Direct synthesis of b-axis oriented H-form ZSM-5 zeolites with an enhanced performance in the methanol to propylene reaction

A b-axis oriented microsized H-form ZSM-5 zeolite with a thinness of approximately 300–500 nm along the b-axis direction was prepared for the methanol to propylene (MTP) reaction by a two stage hydrothermal crystallization method with ammonium hydroxide as the base source and glucose as an additive. Ammonium hydroxide contributed to the direct synthesis of H-form ZSM-5 zeolite after calcination to remove the template and decompose the NH 4 + -form zeolite, thus removing the need for further ion-exchange and calcination steps. Glucose was beneficial to the formation of the thin hierarchical b-axis oriented ZSM-5 zeolites. The b-axis oriented H-form ZSM-5 catalyst exhibited a longer catalyst lifetime and a higher propylene selectivity in the MTP reaction compared to that of ZSM-5 made by a conventional method. The better catalytic performance was ascribed to the relatively low content of strong acid sites especially those on the external surface of the b-axis oriented microsized ZSM-5 catalyst. • B-axis oriented H-form ZSM-5 zeolite was directly prepared by a two-stage crystallization method. • The ion-exchange and further calcination steps for the preparation of H-form ZSM-5 were omitted. • Newly prepared ZSM-5 catalyst exhibited longer catalyst lifetime and higher propylene selectivity.

Catalytic pyrolysis of Asbuton into liquid fuel with Zeolite as catalyst

Natural Buton Asphalt (Asbuton) is a naturally occurring asphalt that is contained in rock deposit located in Buton Island, Indonesia. Asbuton is mostly used as a mixture of bitumen since it has the potential to be cracked into hydrocarbon and produced as a liquid fuel for energy consumption. The present study aims to investigate the effect of pyrolysis temperature and the mass ratio of the Asbuton with catalyst on the Asbuton conversion. The pyrolysis process is carried out on a batch using vacuum reactor with various temperatures and mass ratios of catalyst to Asbuton. The gas coming out of the process is passed through the condenser, where the condensed gas (liquid product) is collected in the flask, whereas the uncondensed gas (gas product) is collected in a gas holder and the yield is analyzed upon the pyrolysis process completion. The respond parameter of the catalytic pyrolysis are oil flammability, yield, and oil density. The synthesized ZSM-5 catalyst is more effective for the Asbuton bitumen cracking process as opposed to the Natural Zeolite. Furthermore, it is investigated that the most optimum operating condition throughout this experiment was 70.07% and obtained at 350 °C with 9% ZSM-5 catalyst. In terms of product characterization, the liquid product can be ignited during the flame test. From the S.G. and API gravity values, it is suggested that the products belong to crude oil range, and thus, confirming that Asbuton has great potentials to be developed into alternative fuel.

Improved biofuel quality in catalytic cracking of triglyceride-rich biomass over nanocrystalline and hierarchical ZSM-5 catalysts

Improved biofuel quality in catalytic cracking of triglyceride-rich biomass over nanocrystalline and hierarchical ZSM-5 catalysts

Competitive adsorption of oxygenates and aromatics during the initial steps of the formation of primary olefins over ZSM-5 catalysts

Aromatics present during the early stages of MTO conversion compete for active sites with the educts, oxygenates (methanol, DME), in primary olefin formation over ZSM-5 catalysts. This competitive adsorption is investigated using TPD and TPSR in a TAP reactor. DME induces methanol desorption at lower temperatures. Diphenylethane desorbs at higher temperatures than toluene. Microkinetic simulations show that toluene, methanol, diphenylethane and DME have activation energies of desorption of 107, 112, 119 and 121 kJmol−1 on strongest binding sites respectively. DME has the highest surface coverage and is suggested as the key surface oxygenate responsible for direct primary olefin formation.

One-step synthesis of glycidol from glycerol in a gas-phase packed-bed continuous flow reactor over HZSM-5 zeolite catalysts modified by CsNO3

In this work we report the pioneering gas-phase conversion of glycerol into glycidol in one-step over Cs–ZSM-5 zeolite catalyst with SiO2/Al2O3 = 1500. The structure and catalytic performance of catalysts synthesized by wet impregnation method with different Cs loadings were studied. The catalysts were characterized by ICP–MS, XRD, N2 physisorption, STEM–EDX, SEM, pyridine-DRIFT, CO2–TPD, NH3–TPD, and TGA techniques. The reaction was carried out in a packed-bed continuous flow reactor under atmospheric pressure. The highest achieved glycidol yield was 40.4 mol% over 20 wt% Cs–ZSM-5(1500) catalyst with 10 wt% glycerol in the feed at 350 °C reaction temperature and GHSVtotal = 1250 h−1. The glycidol selectivity was increasing steadily from 41.4 to 64.3 mol% during 27 h time-on-stream. This catalyst showed relatively high stability and selectivity, which was attributed to the presence of a suitable amount of basic sites and the strong CsNO3/HZSM-5 support synergetic interaction. Based on the identified reaction products, we propose the reaction mechanism of the catalytic glycerol conversion to glycidol over the tested catalysts. It was revealed by SEM and XRD that Si species partly dissolved from HZSM-5 framework after impregnation with CsNO3. Furthermore, we showed that the catalyst deactivation depends on the amount of CsNO3 active phase (basic sites) and the coke formation. The catalytic results demonstrate that at the beginning the glycerol conversion dropped down when CsNO3 was partly decomposed during the reaction, while the second deactivation stage with a slow decrease of catalyst performance corresponded to the coke formation.

Facile adjusting the concentration of siliceous seed to obtain ZSM-5 for cycloaddition reaction of styrene oxide and CO2

Cyclic carbonate is an important organic synthesis intermediate in the fine chemistry. The cycloaddition reaction which catalyzed by the nanosized ZSM-5 zeolites can reach a high selectivity of cyclic carbonates. In this study, a facile seed-assisted strategy for synthesis of ZSM-5 zeolites with different sizes was presented. A nano-sized zeolite and another two different sized zeolites with the size range of 4–5 μm were obtained by only changing the seed precursor. The three zeolites all had the MFI structure and a single chemical condition. Moreover, the ZSM-5 zeolites were applied to the cycloaddition of styrene oxide and CO2 in different reaction conditions, and a suitable reaction condition was obtained. In the suitable condition, the catalytic effects of ZSM-5 catalysts were compared, and the final results demonstrated the smallest one had a highest yield, which was 57.6%.

Catalytic Cracking of High Density Polyethylene Pyrolysis Vapor over Zeolite ZSM-5 towards Production of Diesel

The upsurge in the amount of plastic pollution has drawn the attention of various researchers in finding the best solution for plastic waste treatment. Pyrolysis of high density polyethylene using ZSM-5 catalyst has been investigated using two-staged reactors consisting of a pyrolysis reactor and a catalytic fixed bed reactor. The effect of the heating rate (2 °C/min, 6 °C/min, 10 °C/min, 14 °C/min, 18 °C/min) of the pyrolysis reactor and reaction time (75 min, 90 min, 105 min) were studied on the yield of products and the quality of pyrolytic oil products. The quality of pyrolytic oil produced was evaluated based on the gross calorific values (GCV) and the paraffin, olefin, naphthenic and aromatic (PONA) compounds distribution, which were used to compare with conventional fuel. The highest yield of oil product was obtained at a reaction time of 75 minutes, where it was 61.05 wt.%, with solid product yield of 0.41wt.% and gas product yield of 38.54wt.%, at a heating rate of 2°C/min. The GCV of oil products were within the range of that of conventional diesel (44 – 45 MJ/kg). The pyrolytic oil products contained mainly C10 to C24 hydrocarbon compounds, which were diesel range hydrocarbon. In terms of the PONA distribution, the composition of paraffin was larger for most of the products, while the composition of naphthenes and aromatic were relatively small with respect to the range for conventional diesel.

A viable system for carbon dioxide (CO2) methanation over fibrous silica ZSM-5 for substitute natural gas (SNG)

Catalytic CO2 methanation offers an attractive and sustainable way for the production of substituted natural gas (SNG), which may be used as a clean alternative energy source than fossil fuels. A metal-free fibrous silica ZSM-5 catalyst (FS@ZSM-5) was synthesized via the microemulsion technique to conduct catalytic CO2 methanation. The FESEM, BET, and FTIR characterization techniques were used to investigate the surface morphology, pore structure of the catalysts. It was noticed that the commercialized ZSM-5 showed 37% CH4 selectivity with a rate of methane formation 0.067 mmol m−2s−1. While FS@ZSM-5 exhibited high CH4 selectivity of 66 % with rate of methane formation 0.108 mmol m−2s−1 using same conditions (T = 500 °C and GHSV = 36,000 mL h−1 g−1). Therefore, the FS@ZSM-5 was proved an efficient and active catalyst for CO2 methanation activity.

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.

Formation of non-oxygenated phase of bio-oil produced by copyrolysis of corn cobs and polypropylene plastic using zeolite catalysts at low heating rate

Thermal co-pyrolysis of corn cobs and polypropylene (PP) at low heating rate (thermal slow co-pyrolysis) has succeeded in separating bio-oil produced between oxygenated and non-oxygenated phases spontaneously. In co-pyrolysis, PP can sequester oxygen from bio-oil to convert part of bio-oil to non-oxygenated phase and can contribute partly non-oxygenated phase by PP carbon chain cracking. Catalytic fast co-pyrolysis has been commonly used to improve bio-oil yield and to improve non-oxygenated fraction of bio-oil. However, the catalytic fast co-pyrolysis is unable to obtain separate non-oxygenated fraction of bio-oil. In present work, zeolite catalyst was introduced in co-pyrolysis of corn cobs and PP at low heating rate to undertake catalytic slow co-pyrolysis in order to obtain synergistic effect of non-oxygenated fraction of bio-oil while obtaining separate non-oxygenated fraction of bio-oil. The present co-pyrolysis work was carried out in a stirred tank reactor at heating rate of 5 °C/min and maximum temperature of 500 °C. The composition of feed was varied at 0, 50 and 100%PP in the mixture of corn cob particles and PP granules. The experiment involved 3 catalytic configurations, i.e., no catalyst, ZSM5-38 and ZSM5-70, in which 38 and 70 represents the mole ratio of SI/Al in the catalysts. The results show that in slow co-pyrolysis of biomass-PP, the use of zeolite catalyst with high acidity suppressed the pyrolysis of PP to form wax and reduced bio-oil yield, and the synergistic effect was obtained as the co-pyrolysis used no catalyst and zeolite catalyst of ZSM5-70, while that using zeolite catalyst of ZSM5-38 reached negative synergistic effect. Utilization of catalyst generated high amount of aliphatic moieties, i.e. methyl, methine and methylene. With ZSM5 catalyst utilization, production of allyl decreased. Most of non-polar bio-oil fractions have similar or slightly higher heating values (HHVs) compared to those of commercial fuels. Branching index (BI) values of non-polar phase of bio-oil generated straight carbon chain with higher branches compared to those commercial fuels.

Biogasoline Production from Palm Oil: Optimization of Catalytic Cracking Parameters

Production of biogasoline from vegetable oil is one of the future directions in providing fuels for post-oil society. The catalytic cracking of refined bleached deodorized palm oil over a promoted ZSM-5 catalyst was carried out in a fixed-bed reactor. The fixed-bed catalytic process consists of three steps including reaction, stripping, and regeneration. The optimal catalytic cracking parameters were determined. The properties of catalyst were investigated by thermogravimetry analysis, differential scanning calorimetry, and N2 physisorption analysis while regeneration temperature effect toward catalyst acidity is being investigated by NH3 temperature programmed desorption technique. The apparent results show that the optimized reaction temperature was at 500 °C with a WHSV of 2.5 h−1 and the reaction time of 2 h. Meanwhile, the most effective regeneration temperature was found at 600 °C for three cycles of reaction–regeneration operation. During these cycles, 100% conversion of triglycerides and 48% selectivity to bio-naphtha can still be achieved.

Synthesis of ZSM-5 using different silicon and aluminum sources nature for catalytic conversion of lignite pyrolysis volatiles to light aromatics

ZSM-5 zeolites with different physicochemical property were synthesized using different silicon (Si) and aluminum (Al) sources by hydrothermal method with controlling Al and Si addition. Different crystal shapes were observed from three Si sources. Al sources can influence crystal formation during crystallinity. Al nature causes different amorphous species which affect zeolite activity by blocking the accessible pores. A feasible mechanism of Si and Al sources for crystallization of zeolite was proposed. The activity for lignite volatiles-to-aromatics (LVTA) reaction was investigated to obtain light aromatics. Zeolite using tetraethylortho silicate and aluminum sulfate octahydrate as Si and Al sources shows large surface area and more accessible pores which cause excellent BTEXN yield (23.7 mg/g). The tar yield in the process of LVTA reaction is associated with both porous and acid properties while excessive acidity may cause the formation of coke on the zeolite which causes the blockage. ZSM-5 with optimum and accessible acid sites and abundant pores give a high tar yield and low coke yield. This work provides a ZSM-5 catalyst with suitable acidity and pore property for LVTA reaction.

Phosphorus-modified b-axis oriented hierarchical ZSM-5 zeolites for enhancing catalytic performance in a methanol to propylene reaction

In this work, a b-axis oriented hierarchical ZSM-5 zeolite was prepared with glucose as an additive and further modified by phosphorus to improve the propylene selectivity and prolong the lifetime of the catalyst in a methanol to propylene (MTP) reaction. The physiochemical properties were characterized by XRD, low-temperature N2 sorption, SEM, TEM, XPS, solid-state NMR, FTIR, and NH3-TPD analyses. The b-axis oriented ZSM-5 (Z5-C) zeolite exhibited a microsized hexagonal lamellar structure with a thickness of approximately 220 nm. Analyzing the MTP reactions revealed that the newly prepared Z5-C catalyst exhibited a higher propylene selectivity of 53.01 % and a longer lifetime of 45 h compared to those of a conventional nanosized ZSM-5 catalyst (propylene selectivity of 43.97 % and lifetime of 10 h). In addition, the phosphorus modification remarkably increased the lifetime of the b-axis-oriented ZSM-5 catalyst to 79 h.

A green route for the synthesis of nano-sized hierarchical ZSM-5 zeolite with excellent DTO catalytic performance

Nano-sized hierarchical ZSM-5 zeolite with high crystallization was prepared by a novel green strategy, that is, the consecutive freezing and vacuum drying route. In comparison with the traditional synthesis process, only 1/5 amount of TPAOH (tetrapropylammonium hydroxide) template was involved. Moreover, hierarchical structured zeolites can be formed even in the absence of mesoporous template (e. g. cetyltrimethylammonium bromide, CTAB). Moreover, the hierarchical ZSM-5 with a wide range of SiO2/Al2O3 ratio (25–200) can be modulated. The effects of the consecutive freezing and vacuum drying methods on the formation process, pore characteristics, crystallinity, morphology and acidity of the ZSM-5 zeolites were explored. It is noted that the abundant intra-crystal mesopores and nanoparticles structure were generated from the porous structure on the surface of the freeze-dried powder. The constructed nano-sized and hierarchical ZSM-5 catalyst exhibits a prolonged lifetime of 110 h in dimethyl ether-to-olefin (DTO) reaction, which is around 3.7-fold lifetime compared to the conventional microporous ZSM-5.

Catalytic upgrading of heavy oil over mesoporous HZSM-5 zeolite in the presence of atmospheric oxygen flow

Alkaline treated ZSM-5 zeolite was used in heavy oil upgrading process under atmospheric oxygen flow. Alkaline treatment was employed to induce mesopores in ZSM-5 catalyst structure to alleviate the mass transfer and reduce diffusion limitations. XRD, BET and XRF analyses were employed to investigate the effect of alkaline treatment. Effect of oxygen atmospheric flow, supplied by air stream, on heavy oil catalytic cracking process was investigated in a fixed bed reactor. Obtained liquids were analyzed by FTIR and GC/SIMDIS. Results revealed that percent of light oil (naphtha + kerosene) produced was nearly doubled in the presence of 5 wt% oxygen in the feed. Conversion of heavy oil (content with the BPT higher than 370 °C) was enhanced from 45.7% up to 58.1% by applying air stream. Viscosity reduction was elevated from 40% in nitrogen atmosphere to 53% in presence of 5 wt% oxygen content. Spent catalysts were characterized by TGA, XRD and BET analyses in order to determine coke deposition and catalyst structural stability. Oxidative cracking increased the amount of coke production over the catalyst, however, structural stability of the catalyst was not altered compared to conventional cracking process and crystalline structure of the catalyst was preserved after 5 h time on stream.