ZSM-5 Nanoparticles Research Articles

Performance of hierarchical ZSM-5 supported cobalt catalyst in the Fischer-Tropsch synthesis

Uniform ZSM-5 nanoparticles (around 180 nm) were synthesized by steam assisted crystallization method (SAC), which have a hierarchically porous structure, composed of abundant open mesopores from the stacking of ZSM-5 particles and micropores in the ZSM-5 crystallites. The hierarchical ZSM-5 supported cobalt catalyst, with a cobalt loading of 15%, was then prepared through incipient impregnation and used in Fischer-Tropsch synthesis (FTS). The hierarchical ZSM-5 support and Co-based catalyst were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and N2 sorption. The results indicate that the hierarchical ZSM-5 supported cobalt catalyst performs excellently in FTS, since the mesoporous structure in the hierarchical ZSM-5 support can enhance the mass transfer of the reaction products and the acid sites on the microporous ZSM-5 framework can promote the hydrocracking of long chain hydrocarbon products. In comparison with the cobalt catalysts supported on bulk ZSM-5 and commercial ZSM-5, the hierarchical ZSM-5 supported cobalt catalyst exhibits much higher activity in FTS, lower selectivity to CH4, and higher selectivity to C5–20 hydrocarbons (68.9%).

Simultaneous electrochemical determination of hydrazine and hydroxylamine by CuO doped in ZSM-5 nanoparticles as a new amperometric sensor

In this work, a novel electrochemical sensor using a carbon paste modified electrode with CuO doped in ZSM-5 nanoparticles (CuO/ZSM-5 NPs/CPE) is successfully fabricated for simultaneous determination of hydrazine (HY) and hydroxylamine (HA).

Synthesis of micro-mesoporous aluminosilicates on the basis of ZSM-5 zeolite using dual-functional templates at presence of micellar and molecular templates

Micro-mesoporous aluminosilicates consisting of agglomerates of the ZSM-5 nanoparticles were obtained using dual-functional templates [C6H13–N+(CH3)2–C6H12–N+(CH3)2–C6H13](Br−)2 (C6–6–6Br2), [C8H17–N+(CH3)2–C6H12–N+(CH3)2–C8H17](Br−)2 (C8–6–8Br2). Aluminosilicates with randomly oriented flake-like particles built from ZSM-5 layers were obtained using [C16H33–N+(CH3)2–C6H12–N+(CH3)2–C6H13](Br−)2 (C16–6–6Br2). Use of С8–6–8Br2 and additive of cetyltrimethylammonium bromide CTAB (CTAB concentration is lower than the first critical micelle concentration, CMC1) leads to an increase of the total specific surface area, mesopore surface area and the mesopore size uniformity in the product, as well as the concentration of Brønsted acid sites accessible for bulk molecules. It is assumed that CTAB role is to limit the zeolite crystals growth. Addition of CTAB to С16–6–6Br2 (CTAB concentration is also lower than CMC1) promotes the formation of micro-mesoporous aluminosilicate possessing disordered lamellar mesostructure stable upon calcination which is characterized by a higher total specific surface area and better mesopores uniformity than ZSM-5 obtained in the presence of С16–6–6Br2. The additive of a molecular template tetrapropylammonium hydroxide (TPAOH) shifts the structure formation toward zeolite and leads to an increase in the ratio of concentrations of Brønsted and Lewis acid sites for the obtained aluminosilicates. The addition of small amounts of TPAOH into the reaction mixture (TPAOH/C16–6–6Br2 = 6.5·10−3) leads to formation of self-pillared aluminosilicate. In this material the nanoparticles act as “pillars” between the layers of ZSM-5 and thus contribute to retention of low-ordered lamellar mesostructure after calcination, leading to increase of the total specific surface area and improving mesopores uniformity.

Gas separation in mixed matrix membranes based on polyurethane containing SiO2, ZSM-5, and ZIF-8 nanoparticles

In this study, inorganic silica nanoparticle, ZSM-5 and ZIF-8 were used as dispersed particles inside polyurethane matrix in order to separate two gases of carbon dioxide and methane. The distribution of suspension particle size in the solution is investigated by DLS, FTIR, and SEM. MMMs were subjected to permeability test both in pure and in mixed gases of methane and carbon dioxide. The prepared polyurethane/ZIF-8 membranes with a permeability of 74.6 barrer and selectivity 19.1 showed the best separation performance because of proper pore size and better compatibility between ZIF-8 with polyurethane.

Amphiphilic organosilane and seed assisted hierarchical ZSM-5 synthesis: Crystallization process and structure

The synthesis, characterization, and catalytic applications of hierarchical zeolite has drawn a lot of research interest. During hierarchical zeolite synthesis, different products can be formed due to the difference in crystallization mechanism. Here we detail the crystallization process and structure of the hierarchical ZSM-5 synthesized with amphiphilic organosilane and seed. First, the effects of synthesis parameters on zeolite products were studied in detail to optimize the hierarchical zeolite synthesis process. Dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride (TPOAC), seed and rotation are the required conditions for the synthesis of high quality hierarchical ZSM-5 with both high micropore and mesopore volume. The obtained hierarchical zeolite samples were then subjected to detailed structural analysis including XRD, SEM, TEM, nitrogen sorption and a sonication fragmentation method. Hierarchical ZSM-5 synthesized herein was a mesoporous aggregate of ZSM-5 nanoparticles with a core/shell structure based on the characterization results. The core part is hierarchical ZSM-5 with a higher degree of connectivity between zeolite nanoparticles or even the so-called mesoporous zeolite single crystal. The shell component is the hierarchical ZSM-5 aggregate with loosely packed ZSM-5 nanoparticles. The formation process and structure change was finally investigated by monitoring the morphology, crystallinity, and porosity of samples obtained with different crystallization times. The results indicated that hierarchical ZSM-5 is a kinetically controlled product in ZSM-5 crystallization process through a nanoparticle-oriented aggregation mechanism. The TPOAC, seed, and crystallization time are the conditions kinetically controlling the crystallization process.

A New Practical Route to ZSM‐5 Nanoparticles and Optimization of Synthetic Parameters through D‐optimal Design of Experiments

AbstractA D‐optimal experimental design with three levels of SiO2/Al2O3, template/SiO2, H2O/SiO2, Na2O/SiO2 and TPABr/TPAOH ratio parameters has been used to optimize the experimental parameters by an analysis of variances (ANOVA). The effects of these ratios in the initial synthetic mixture on the size of the ZSM‐5 zeolite nanoparticles have been studied. XRD and FE‐SEM analyses were used to characterize synthetic samples. Fischer test results showed that H2O/SiO2 and TPABr/TPAOH ratios are the most and least effective parameters, respectively, in the range studied. The most important two‐way interaction variables were the interaction of template/SiO2 and TPABr/TPAOH molar ratios. The average particle size was in the 34–79 nm range. Furthermore, a mathematical model for the synthesis of ZSM‐5 zeolite nanoparticles was derived using experimental results. The optimized gel composition is as follows: SiO2/Al2O3=91.20, template/SiO2=0.16, H2O/SiO2=40.42, Na2O/SiO2=0.0147 and TPABr/TPAOH=0.

The role of supercritical water on the rapid formation of ZSM-5 nanocatalyst

We herein report a rapid (30min) and effective route for the synthesis of ZSM-5 nanocrystals with well-defined morphology (rounded shapes and hexagonal forms) in supercritical water (SCW) by single and two-step procedures where in case of the latter, the precursor was aged for 120min in 80°C before carrying to supercritical state (T=450°C). The effect of parent composition with different ratio of NaOH/Al2O3 and SiO2/Al2O3 were investigated comprehensively on crystallinity and morphology of product through powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), field emotion scanning electron microscopy (FE-SEM), and transmission electron microscopy (TEM) analyses. Compared with the low temperature hydrothermal (LTH) synthesis method with high duration (two days), the product obtained from SCW exhibited considerable increase in BET surface area. To the best of our knowledge, this development was attributed to the modification in thermodynamic (solvation and dispersion effects) and transport properties of solution in supercritical state. Considering the advanced liquid-base mechanism of zeolites formation at low temperature, such modifications in properties of SCW can increase the liquid-bulk gel interface and transport of nutrients (e.g., Na+) through the amorphous gel network, which they have significant effect on the establishment of zeolite building, namely protozeolite. The high nucleation and diffusion rates of protozeolite nuclei in SCW, from the amorphous gel network to the bulk liquid, then lead to the high efficient formation of fine ZSM-5 nanoparticles with the large BET surface area.

Hydrophobic zeolites coated with microporous organic polymers: adsorption behavior of ammonia under humid conditions

ZSM-5 nanoparticles coated with microporous organic polymers showed 88% retention of ammonia adsorption capacity at 43% RH.

Mixed templates application in ZSM-5 nanoparticles synthesis: Effect on the size, crystallinity, and surface area

ZSM-5 nanoparticles of 50–100nm size were synthesized by simultaneously adding tetrapropylammonium hydroxide and bromide using the following stoichiometry: NaAlO2: 25 SiO2: x TPAOH: y TPABr: 0.033 Na2O: 1000 H2O in which x+y is equal to 9.The synthesized samples were characterized by X-ray diffraction, field emission scanning electron microscope, transmission electron microscopy and Brunauer–Emmett–Teller surface area analysis. Impacts of various ratios of tetrapropylammonium hydroxide to tetrapropylammonium bromide, on size, crystallinity and surface were examined and it was found that in 6 tetrapropylammonium bromide to 3 tetrapropylammonium hydroxide mixed templates optimized ratio, the smallest size with the biggest surface and high crystallinity was achieved. Using tetrapropylammonium bromide template only for synthesis of ZSM-5 in high molar stoichiometry ratio (9 tetrapropylammonium bromide) in synthesis gel lead to get amorphous particles because of the synthesis gel sharp pH drop during crystallization.

A novel mesoporous molecular sieves-based electrochemilumenescence sensor for sensitive detection of azithromycin

A new mesoporous molecular sieves-based electrochemiluminescence (ECL) sensor was developed for the quantitative detection of azithromycin (AZM). Zeolite Socony Mobile-Five (ZSM-5) nanoparticles were synthesized by a hydrothermal method. Electrochemical and ECL behaviors of the Ru(bpy)32+/ZSM-5/Nafion multilayer film-modified electrodes were investigated. The ECL sensor was used to detect AZM and showed a wide linear range from 0.0038 to 62.5μM, with a detection limit of 1.27nM (S/N=3). The high sensitivity and stability was mainly attributed to the large surface-to-volume ratios and superior adsorption capacity of ZSM-5 nanoparticles. Moreover, the ECL sensor was applied for detection of AZM in azithromycin dispersible tablets sample, and the results were satisfactory with the recoveries of 96.0–102.8%. The proposed signal amplification strategy for the preparation of ECL sensor could be easily attained and be promising for ultrasensitive drug assay.

Novel template confinement derived from polybenzoxazine-based carbon xerogels for synthesis of ZSM-5 nanoparticles via microwave irradiation

Polybenzoxazine, a new class of phenolic resin, has been successfully synthesized via a facile quasi-solventless method and used as a starting material for producing nano-porous carbon with pore sizes of about 40–200nm. This porous carbon is prepared via a sol–gel process, using dioxane as a solvent (CXDI) and is used as a hard template confinement to produce crystalline nanosized MFI or ZSM-5 with a molar composition of 10Na2O:200SiO2:Al2O3:20TPABr:12,600H2O via hydrothermal microwave irradiation technique within 6h of synthesis time. The XRD patterns show a well-ordered crystalline phase of nanosized ZSM-5. In addition, FTIR result shows the weak absorption band at 550cm−1, indicating the presence of nanosized ZSM-5. Particle size distribution obtained from dynamic light scattering and TEM images reveal that the crystal size of ZSM-5 synthesized using CXDI as a hard template (ZSM-5-CXDI) is in the range of 27–70nm. ZSM-5-CXDI also shows large external surface area of 217m2/g.

Mixed-matrix membranes composed of Matrimid ® and mesoporous ZSM-5 nanoparticles

Mixed-matrix membranes were prepared from Matrimid ® and mesoporous ZSM-5 nanoparticles containing crystalline ZSM-5. The ideal selectivity for H 2/N 2 separation increased from 79.6 for pure Matrimid ® to 143 at 10% loading, while the selectivity of O 2/N 2 increased from 6.6 for pure Matrimid ® to 10.4 at 20% loading. The ideal H 2/CH 4 separation factor increased from 83.3 to 169 at 20% loading. The results suggest that the mesopores of the ZSM-5 material provide good contact between the nanoparticles and the polymer, since the polymer chains can penetrate into the mesopores. The micropores of ZSM-5 crystals provide size and shape selectivity.

Preparation of magnetic hollow ZSM-5/Ni composite spheres

This paper presents a method for the preparation of magnetic hollow ZSM-5/Ni composite spheres. ZSM-5/Ni/PS spheres were firstly synthesized by assembling ZSM-5 nanoparticles on the surfaces of Ni/PS spheres, followed by hydrothermal treatment to form a compact ZSM-5 layer. Magnetic hollow ZSM-5/Ni spheres were subsequently obtained by calcination and reduction of the ZSM-5/Ni/PS spheres. The samples were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), thermogravimetry (TG), energy dispersive X-ray spectroscopy (EDX), temperature-programmed reduction (TPR) and a vibrating sample magnetometer (VSM). A continuous ZSM-5 layer with a thickness of 400 nm was formed on the surface of Ni/PS spheres after one cycle of adsorption of ZSM-5 nanoparticles and hydrothermal treatment at 80 °C for 36 h. By changing the hydrothermal treatment time, the thickness of zeolite layer can be controlled. The hollow ZSM-5/Ni spheres inherited magnetic property from the nickel layer and their magnetization value could be adjusted by varying the thickness of the nickel layers.

Preparation of ZSM-5 nanoparticles supported on carbon substrate

Influences of the pore structure and the surface functionality of carbon substrates on the formation of ZSM-5 nanoparticles were studied. The inorganic substance formed on these carbons were identified as ZSM-5 by X-ray diffraction, which also revealed the presence of an amorphous silica phase. The fraction of crystalline phase, which was evaluated from XRD, was not affected by the pore structure; however, inorganic content depended on the pore structure of carbon: i.e. 14–17% for non- and microporous carbons, and 40–55% for mesoporous carbons. TEM observation revealed that the ZSM-5 deposited on these carbon substrates was in the form of nanoparticles with 10–20 nm of diameters. The influence of the surface functionality on the formation of ZSM-5 nanoparticles was also studied with an activated carbon, of which surface functionality was modified by heat-treatment and nitric acid-treatment. A strong dependence of the fraction of crystalline phase on the treatments was observed; i.e. the heat-treatment increased the fraction and the acid-treatment decreased it. Finally, we clarified the controlling factors for the formation of ZSM-5 on carbon materials; the mesoporous surface area of carbon strongly affects the inorganic content and the total acidity of carbon influences the selectivity to ZSM-5 formation.