ZSM-5 Phase Research Articles

Characterization of Zeolite ZSM-5 Synthesized from Kaolin and TPABr Using X-Ray Diffraction and Infrared Spectroscopy

Kaolin with alumina and silica content is used as the main material in this research to study the synthesis of ZSM-5 zeolite. The hydrothermal process was carried out through different aging times, namely 12, 24 and 36 hours. Tetrapropyl ammonium bromide (TPABr) was used as a template for the Mobile Five-1 (MFI) structure guide. X-ray diffraction (XRD) and infrared spectroscopy (FTIR) instruments were used to characterize the ZSM-5 zeolite formed from the synthesis results. This was done to identify the phase change from kaolin to zeolite ZSM-5. The results of the analysis using XRD for all samples showed a characteristic peak of the ZSM-5 zeolite at 2θ around 7.88°; 8.72° ;23.09°; 23.84° and 24.32°. However, samples with an aging time of 12 hours also showed peaks at 2θ around 15.84° and 26.03° which indicated an analsim phase. The absorption bands from the FTIR characterization for all samples are seen at wave numbers around 453, 542, 793, 1088 and 1221 cm−1 which are the characteristic peak points of ZSM-5 zeolite. The longer the aging time indicates that the crystallinity of the ZSM-5 zeolite is increasing. The highest crystallinity was obtained from ZSM-5 zeolite samples which were aged for 36 hours. This indicates an increasing number of ZSM-5 crystal nuclei with high purity because there is no other phase besides the ZSM-5 phase.

Thiolation behaviors of methanol catalyzed by bifunctional ZSM-5@t-ZrO2 catalyst

The catalytic properties of bifunctional ZSM-5@t-ZrO2 catalyst for methanol thiolation were revealed by using methanol and H2S as probe molecules. Taking the ZSM-5/t-ZrO2 physically-blended catalyst, pure ZSM-5 and t-ZrO2 as control catalysts, we investigated the characteristics of adsorption and transformation of different reaction molecules on or over different catalysts by combination of in-situ diffuse reflectance Fourier transform infrared spectroscopy (Drifts) and a variety of techniques including XRD, XPS, XRF, FT-IR, N2 adsorption-desorption, CO2/NH3-TPD, and DSC. The results showed that the synergistic effect of acid sites between ZSM-5 phase and t-ZrO2 phase in the bifunctional catalyst enhanced the adsorption and dissociation of methanol molecules, while the base sites in t-ZrO2 phase were mainly responsible for the adsorption and dissociation of H2S molecules. Due to the small specific surface area of pure t-ZrO2 catalyst, precursor species for sulfur deposition and carbon deposition were easily formed. Presulfurization could improve the initial activity of methanol thiolation and shorten the induction period. The dissociation of H2S at the base sites was the rate-determining step of the bimolecular reaction, and the appropriate increase of base sites in the bifunctional components could construct the matching formation rate of sulfhydryl and methoxy groups. At the same time, the special composite structure and meso-microporous system of ZSM-5@t-ZrO2 could effectively reduce the formation rate of carbon and sulfur deposits.

Creation of cross directing intergrowth MOR/ZSM-5 with high catalytic activity: Insights into the role of crystallization time

A series of MOR/ZSM-5 intergrowth zeolites were hydrothermally synthesized by employing ethylenediamine (EDA) as template. The physical and chemical properties of the zeolite intergrowths were characterized by using XRD, N2 adsorption-desorption, SEM, TEM, NH3-TPD, FT-IR and Py-IR, respectively. Variation in the crystallization time played a vital role during zeolite synthesis. The results revealed that the crystalline products switched from ZSM-5 phase to intergrowth MOR/ZSM-5 and finally to MOR phase with the extending of crystallization time from 24 h to 96 h. Moreover, the catalytic performances of the zeolite intergrowths in the reaction of toluene disproportionation and n-Butane isomerization were investigated. The MOR/ZSM-5 sample with 72 h of crystallization time was found to exhibit superior performance, which suggested its great potential to act as highly effective heterogeneous catalyst.

Fabrication and catalytic performance of meso-ZSM-5 zeolite encapsulated ferric oxide nanoparticles for phenol hydroxylation

An encapsulation-structured Fe2O3@meso-ZSM-5 (Fe@MZ5) was fabricated by confining Fe2O3 nanoparticles (ca. 4 nm) within the ordered mesopores of hierarchical ZSM-5 zeolite (meso-ZSM-5), with ferric oleate and amphiphilic organosilane as the iron source and meso-porogen, respectively. For comparison, catalysts with Fe2O3 (ca. 12 nm) encapsulated in intra-crystal holes of meso-ZSM-5 and with MCM-41 or ZSM-5 phase as the shell were also prepared via sequential desilication and recrystallization at different pH values and temperatures. Catalytic phenol hydroxylation performance of the as-prepared catalysts using H2O2 as oxidant was compared. Among the encapsulation-structured catalysts, Fe@MZ5 showed the highest phenol conversion and hydroquinone selectivity, which were enhanced by two times compared to the Fe-oxide impregnated ZSM-5 (Fe/Z5). Moreover, the Fe-leaching amount of Fe@MZ5 was only 3% of that for Fe/Z5. The influence of reaction parameters, reusability, and · OH scavenging ability of the catalysts were also investigated. Based on the above results, the structure-performance relationship of these new catalysts was preliminarily described.

Fabrication and properties of βTCP/Zeolite/Gelatin scaffold as developed scaffold in bone regeneration: in vitro and in vivo studies

Synthetic scaffolds, as an alternative to allograft and xenograft scaffolds, are suitable for bone regeneration. This study aimed to synthesize a composite biomaterial of zeolite and beta-tricalcium phosphate (βTCP) to obtain a biocompatible material with physical and mechanical properties in bone regeneration. One scaffold without zeolite (βZG 0) and two scaffolds with different amounts of zeolite (βZG 1 and βZG 2) were synthesized. The scaffolds were evaluated by FTIR, XRD, compressive strength test, MTT assay, and radiographic and histological analyses. The XRD results confirmed the presence of βTCP and ZSM-5 phases in the composite scaffolds and also, indicated that the addition of gelatin decrease the crystallinity of composite scaffolds. FTIR revealed the gelatin, β-TCP and ZSM-5 functional groups in the composite structure. βZG 2 group had the maximum porosity among the scaffolds (74%) ranging in size from 61-600 µm. Compressive strength test showed that the Young’s modulus changed from 23 MPa to 59 MPa, and the zeolite nanostructure was the most influential factor responsible for this change. The MTT assay showed the superiority of βZG 2, and the macroscopic and microscopic results at 4, 8, and 12 weeks revealed the maximum bone regeneration and formation of bone trabeculae in the βZG 2 and βZG 1 groups, respectively. The zeolite scaffold showed the superior mechanical, radiographic and histological properties compared with the control and non-zeolite scaffold. βTCP/ Zeolite/ Gelatin scaffold can be an appropriate candidate for medical application in bone regeneration.

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.

High selectivity in methanethiol synthesis over a coated composite comprising ZSM-5 with t-ZrO2

Abstract The ZSM-5@t-ZrO2 coated composite with t-ZrO2 as a shell phase, was fabricated using polyelectrolyte-based layer by layer assembly strategy, to enhance the selectivity of methanethiol by the confinement effect of base sites distributed on the shell layer. The study showed that polyelectrolyte functionalization of the t-ZrO2 surface was crucial to avoid phase separation during the hydrothermal coating process. The fully coated composite obtained via polyelectrolyte modification in order of PDDA+/PSS−/PDDA+ exhibited superior catalytic performance toward methanethiol selectivity of up to 95% and methanol conversion rate close to 90%. Methanethiol selectivity increased by approx. 20% compared with the unmodified composite. The interfacial interaction between the ZSM-5 and t-ZrO2 phases was related to the coated structure, which subsequently caused a series of favorable alterations to the composite's physicochemical properties. Moreover, the confinement effect produced by the fully coated structure with t-ZrO2 as the shell phase primarily contributed to enhancement of methanethiol selectivity of ZSM-5@t-ZrO2 in the thiolation of methanol with H2S to methanethiol.

Effect of desilication on the textural properties, acidity and catalytic activity of zeolite ZSM-23 synthesized with different structure-directing agents

Abstract The synthesis of ZSM-23 zeolite was studied using isopropylamine, ethylene glycol, pyrrolidine and N,N-dimethylformamide as structure-directing agents, followed by post-synthesis treatment. The samples were characterized by X-ray diffraction (XRD), dispersive energy X-ray spectroscopy (EDX), thermal analysis, adsorption-desorption of nitrogen, temperature programmed desorption of ammonia (TPD-NH3) and scanning electron microscopy (SEM). ZSM-23 was obtained with all organic molecules tested, and the sample synthesized with isopropylamine presented a higher crystallinity. EDX measurements indicated parent zeolites with SiO2/Al2O3 ratio ≥66. Thermal analysis curves showed that the parent sample prepared with isopropylamine presented lower mass loss, corroborating the crystallinity results and indicating a greater efficiency of this compound in the ZSM-23 synthesis. Micrographs of the parent samples synthesized with isopropylamine, ethylene glycol and N,N-dimethylformamide illustrated the characteristic morphology of ZSM-23 as “needles”, whereas the sample obtained with pyrrolidine showed the coexistence of ZSM-23 and ZSM-5 phases. TPD-NH3 results demonstrated that the post-synthesis treatment promoted, in all cases, a decrease in the weak acid sites and an increase in the strong and total acid sites densities for the samples from the isopropylamine and N,N-dimethylformamide series. Adsorption-desorption of nitrogen showed an increase in pore volume and specific surface area values for the modified samples compared to the parent materials. Modified zeolites presented higher catalytic activity and better deactivation resistance in n-heptane catalytic cracking in comparison to the precursor samples, with all catalysts showing excellent selectivity for propene and ethene.

Ethylene oligomerization over H- and Ni-form aluminosilicate composite with ZSM-5 and MCM-41 structure: Effect of acidity strength, nickel site and porosity

Abstract The micro-mesoporous aluminosilicates with composite structure of ZSM-5 phase encapsulated in MCM-41 structure were prepared. The corresponding H- and Ni-form composites were characterized and compared with the ZSM-5, MCM-41 to investigate the influence of acid strength and porosity on the catalytic performance of ethylene oligomerization. Their acidity increases with the increased ZSM-5 components incorporated in the MCM-41 structure. After loading Ni species the amount of weak acid site increases and that of strong acid site decreases. The interaction between the exchanged Ni-ion and the support is improved by the increased strength of acidity of zeolite. The catalytic character of the ZSM-5 and MCM-41 phase exhibited in the products distribution was studied under two typical reaction conditions for α-olefins and liquid fuel productions. The synergetic effect of Ni-ions and acid sites with different acid strength zeolite structure shows that the Ni-ion on MCM-41 is superior for ethylene conversion and determines the Anderson-Schultz-Flory products distribution at 523 K, and the strong acid site from microporous ZSM-5 is preponderant for ethylene conversion and dominates products distribution at 723 K. The nickel species are not only favorable to dimerization of α-olefins at 523 K, but also to dehydrogenation for aromatics generation at 723 K.

Evaluation of silanization of Fe-silicalite-1, Na-Fe-ZSM-5 and solvent concentration on the oxidation of n-octane to C8 oxygenates

The synthesis of Na-Fe-Silicalite-1(80), Na-Fe-Silicalite-1(128), Na-Fe-ZSM-5(78) and Na-Fe-ZSM-5(126) was conducted using the isomorphic substitution method. These catalysts were further modified by the process of silanisation to yield Na-Fe-Silicalite-1(80:Sil), Na-Fe-Silicalite-1(128:Sil), Na-Fe-ZSM-5(78:Sil), and Na-Fe-ZSM-5(126:Sil) (The numbers in brackets represent the Si/Fe molar ratio and Sil represents silanization). The XRD analyses show that only the ZSM-5 phase was present in all the catalysts. These catalysts were tested in the oxidation of n-octane in MeCN using H2O2 as an oxidant. It was found that the selectivity to terminal products increased with increasing the volume of MeCN. Thus, e.g. terminal C8 selectivities could be improved from 17 to 28% using the Na-Fe-Silicalite-1(80) catalyst by increasing the volume of solvent. Furthermore, the Na-Fe-Silicalite-1(80), Na-Fe-Silicalite-1(80:Sil), Na-Fe-Silicalite-1(128) and Na-Fe-Silicalite-1(128:Sil) show terminal selectivities of 28.1, 14.3, 17.6 and 12.3% respectively. In contrast Na-Fe-ZSM-5(78), Na-Fe-ZSM-5(126), Na-Fe-ZSM-5(78:Sil), and Na-Fe-ZSM-5(126:Sil) show terminal selectivities of 24.5, 25.7, 21.3 and 27.3% respectively. Results also showed that the Na-Fe-ZSM-5 catalyst has better selectivity to terminal products than Na-Fe-Silicalite-1.

RETRACTED ARTICLE: Study on Methylation of Naphthalene with Methanol over ZSM-5 (core)/SAPO-11(shell) Composite Molecular Sieve

ZSM-5 (core)/SAPO-11 (shell) composite molecular sieve was synthesized by the hydrothermal method in order to combine the advantages of ZSM-5 and SAPO-11 for the methylation of naphthalene with methanol. For comparison, the mechanical mixture was prepared through the blending of ZSM-5 and SAPO-11. The characterization results indicated that ZSM-5/SAPO-11 composite molecular sieve exhibited a core–shell structure, with the ZSM-5 phase as the core and the SAPO-11 phase as the shell. The pore size of the composite was between that of ZSM-5 and SAPO-11. The composite had fewer acid sites than ZSM-5 and mechanical mixture while more acid sites than SAPO-11. The experimental results indicated that the composite exhibited high catalytic performances for the methylation of naphthalene with methanol.

High-temperature and short-time hydrothermal fabrication of nanostructured ZSM-5 catalyst with suitable pore geometry and strong intrinsic acidity used in methanol to light olefins conversion

High temperature hydrothermal synthesis method was developed to preparation of nanostructured ZSM-5 molecular sieves at short crystallization time. A series of catalysts were synthesized at various temperatures and crystallization times for achievement of pure ZSM-5 phase with MFI structure. The synthesized catalysts were investigated with XRD, FESEM, EDX, BET-BJH, FTIR and TPD-NH3 techniques. The results revealed that hydrothermal synthesis conditions generally affected the nucleation rate, particle size, textural properties and acidic nature of ZSM-5 catalysts. It was found that pure ZSM-5 materials with high crystallinity could be obtained at specific crystallization conditions of about 300 °C for 1.5 h and also 350 °C for 0.5 h. Increasing the hydrothermal temperature to 350 °C and decreasing the crystallization time to 0.5 h led to the formation of small particles with high specific surface area of 392 m2/g. Furthermore, ammonia TPD spectra showed that ZSM-5(300-1.5) catalyst contained higher amount of acid sites and less acid strength compared to ZSM-5(350-0.5) catalyst. The catalytic performance of samples was studied for conversion of methanol to light olefins under different reaction conditions. Interestingly, the proper pore geometry along with the strong intrinsic acidity resulted in a tendency for excessive production of light olefins for ZSM-5(350-0.5) catalyst. The selectivity of light olefins over this catalyst was increased about 94% in the long time on stream (2100 min). Also, the possible reaction pathway for ZSM-5 synthesis at high temperatures was discussed in details.

ZSM-5 synthesis by the assistance of biomass and biomass-derivate compounds

ZSM-5 zeolites with tailored properties were successfully synthesized in the presence of biomass-derivative compounds following conventional hydrothermal route. The strategy consisted of introducing, along with silica and alumina precursors, either sugar cane bagasse itself or biomass-derivate compounds obtained by hydrolysis of the sugar cane. As-prepared ZSM-5 catalysts were thoroughly characterized by XRD, XRF, SEM, nitrogen sorption and H/D isotope exchange techniques. The catalysts were evaluated both in the cracking of n-hexane and the methanol conversion into hydrocarbons. Our approach yielded solely ZSM-5 phase with broad differences in their intrinsic properties: external surface area (between 51 and 153 m2 g−1); 8 < Si/Al < 29, thus leading up to high Brønsted acid sites density; crystal size (from 0.3 to 13 μm) and peculiar morphologies. The high Al-content ZSM-5 led to achieve the higher n-hexane cracking activity. The ZSM-5 with the highest external area and higher Si/Al (SAR) converted methanol mainly into light olefins, whilst, the ZSM-5 material with the lower external area and lower SAR yielded gasoline formation.

Influence of initial Si/Al ratios on the structural, acidic and catalytic properties of nanosized-ZSM-5/SBA-15 analog composites prepared from ZSM-5 precursors

Nano-ZSM-5/SBA-15 analog composites (ZSC) were prepared in a two-step process from ZSM-5 precursors with different Si/Al molar ratios (10–50) via high-temperature synthesis in mildly acidic media (200 °C, pH 3.5) aiming to evaluate the influence of the initial Si/Al ratio on their structural, acidic and catalytic properties. The resulting materials were characterized by SAXS, XRD, FTIR, TEM, N2 sorption, 27Al solid state-NMR, NH3-TPD, FTIR spectroscopy of adsorbed pyridine, AAS and ICP-AES. Under the applied synthesis conditions, a ZSC material with controlled distribution of nano-ZSM-5 and SBA-15 analog phases can be prepared from ZSM-5 precursors by adjusting the initial Si/Al ratio in the range of 20–30. Increasing the initial Si/Al ratio to 50, only ZSM-5 nanocrystals were obtained whereas reducing the initial Si/Al ratio to 10 led to the formation of a disordered mesoporous SBA-15 analog. The total acidity increases with the crystallinity of the ZSM-5 phase as varying the Si/Al ratio from 10 to 30 despite the decreased amount of incorporated aluminum. However, the acidity declines slightly when raising the Si/Al ratio to 50 because of the low incorporated aluminum. The catalytic performance of the ZSC materials compared to the reference materials, i.e. purely mesoporous Al-SBA-15 and purely microporous H-ZSM-5 was assessed in the gas phase cracking of cumene and 1,3,5-tri-isopropylbenzene (TIPB) as test reactions. The results show that a balanced ratio of nano-ZSM-5 and SBA-15 analog phases obtained by tuning the initial Si/Al ratio is crucial to achieve superior catalytic performance of the ZSC materials in the cracking of both cumene and TIPB.

ZSM-5/TiO2 Hybrid Photocatalysts: Influence of the Preparation Method and Synergistic Effect

In this work, the influence of the preparation method of ZSM-5/TiO2 hybrids on the photocatalytic performance for removal of formaldehyde (HCHO) or trichloroethylene (C2HCl3) in gas phase was analyzed. For this purpose, two methods for the synthesis of the hybrids, the incipient wetness impregnation (I) and the mechanical mixing method (M), were selected. The photocatalysts were characterized by N2 adsorption–desorption, TEM, UV–Vis spectroscopy, XRD and electrophoretic migration. Also, the adsorption ability of the individual materials and hybrids was analyzed. ZSM-5/TiO2 hybrids showed higher photocatalytic activity than bare TiO2, independently of the preparation method selected. Mechanical mixing is a simple and easily scalable method to prepare highly active photocatalyst with high amounts of titania. The internal diffusion processes of the reactants to the active sites could be improved due to the micro–mesoporous structure developed on these hybrids. Incipient wetness impregnation method leads to photocatalysts with higher photodegradation rates per active site. The hybrids synthetized by this method show TiO2 nanoparticles homogeneously dispersed on the ZSM-5 phase. The fraction of TiO2 exposed on the surface ca. 75 mol% was similar for materials prepared by both methods, explaining the similar adsorption and photocatalytic properties, independently of the TiO2 content. The nature of the pollutant has an important role in the adsorption and photocatalytic properties of the composites. Finally, the effect of the incorporation of the zeolite in the photocatalytic system was analyzed. For this purpose, the influence of the zeolite and titania arrangement in the sample holder on the photodegradation rate was analyzed. Although the incorporation of the zeolite induces a positive effect on the photocatalytic performance, independently of the position on the sample holder, a clear synergistic effect when both phases were in intimate contact such as in the ZSM-5/TiO2 hybrid was observed.

Peroxide oxidation of n-octane over Na-Fe-silicalite-1 and H-Fe-Silicalite-1 catalysts

The synthesis of the catalysts Na-Fe-silicalite-1(34), H-Fe-silicalite-1(34) and Na-Fe-silicalite-1(68) has been achieved by using the sol-gel method to incorporate the Fe as a T-atom in the zeolite framework (the values in brackets refer to Si/Fe molar ratios). Techniques that include FT-IR, XRD, SEM, TEM, ICP-OES, XRF, BET, TPR and TPD were used to characterize the catalysts. The XRD results show that only the ZSM-5 phase was present in all the synthesized catalysts. In addition, the TPR data showed a single peak assignable to Fe(III) species at 809.3, 806.5, and 777.9°C for Na-Fe-silicalite-1(34), H-Fe-silicalite-1(34) and Na-Fe-silicalite-1(68) respectively. The oxidation of octane over Na-Fe-silicalite-1(34) using H2O2 as an oxidant showed a direct dependence of conversion on temperature such that conversions of 9.6, 16.1 and 18% were recorded at 40, 60 and 80°C respectively. However, an inverse relationship was observed for the selectivity to terminal products (1-octanol and octanal). Selectivities of 30, 25 and 24% were recorded at 40, 60 and 80°C respectively. The H-Fe-silicalite-1(34) and Na-Fe-silicalite-1(68) catalysts were further tested at 80°C with the results showing that the H-Fe-silicalite-1(34) attained a terminal product selectivity of 26% at 19.8% conversion, while Na-Fe-silicalite-1(68) showed 27% selectivity to terminal products at 13.7% conversion. Only linear C8 products were observed under the conducted reaction conditions.

Structural and Textural Characteristics of Zn-Containing ZSM-5 Zeolites and Application for the Selective Catalytic Reduction of NOx with NH3 at High Temperatures

Zinc-containing MFI-type ZSM-5 zeolites were synthesized with ammonia coordinated zinc solution as zinc source, n-butyl amine as template and ZSM-5 as seeds by a facile one-step hydrothermal method, which exhibited outstanding performance for selective catalytic reduction NO with NH3 over a wide temperature range. The powder X-ray diffraction detected results showed that there was no other crystalline phase except for ZSM-5 phase and IR analysis suggested that the zinc had successfully incorporated into the zeolite framework was the vibration absorption peak at 1080 and 1230 cm−1 were broadened, which were assigned to asymmetric stretching of Si–O–Si. With the amount of zinc increases, big changes of morphologies, specific area and pore volume occurred which were collected by scanning electron microscope and Brunauer Emmett Teller Method. And the content of zinc species in the synthesized system was able to coordinate the growth size of the crystal. Furthermore, the addition of seeds would basically effectively prohibit the twin growth among these Zn-containing ZSM-5 crystals was firstly brought forward. Schematic diagrams of (A) Mono-dispersed ZSM-5 particles (B) Twin growth ZSM-5 particles.

HYDROTHERMAL SYNTHESIS AND CHARACTERIZATION OF NANO SIZED ZSM-5 AND THEIR EFFECT ON THE DECOLORIZATION OF INDIGO CARMINE DYE

Silica sources can influence different effects of ZSM-5 crystallization and it leads to change in the properties of the final product. The crystallinity of nanosized ZSM-5 zeolite from precursors mixtures containing different silica sources, e.g. tetraethylorthosilicate (TEOS), colloidal silica (CS), silicic acid(SA) and fumed silica(FS) have been studied. The produced samples are investigated using XRD, SEM, FT-IR, pyridine adsorption and N2 adsorption measurements. XRD results show that the product obtained by different silica sources is nano sized ZSM-5 phase. SEM results show that silica sources influences on shape of the produced ZSM-5; the sample which was prepared by silicic acid crystallized in spherical shape crystals, the samples which was prepared by TEOS crystallized in cubical shape crystals, the sample which was prepared by colloidal silica crystallized in spherical shape crystals with smaller aggregated but the sample which was prepared by fumed silica crystallized in round shape crystals. N2 adsorption results show thatsilica sources influences on pore diameter and pore volume of the produced ZSM-5.The adsorption of indigo carmine dye by ZSM-5 has been studied. It was found that the synthesized zeolite by SA exhibited significantly higher adsorption capacity for indigo carmine than other ZSM-5 states due to the difference in morphological properties. The optimum ZSM-5 loading is 1 g at pH 4 after 180 min.

Cristalización de zeolita beta mediante conversión asistida por vapor: influencia de los parámetros de síntesis

In the present work, beta zeolites were prepared by an alternative route called steam-assisted conversion (SAC). Several zeolites were synthesized using amorphous dry gels with a low SDA concentration (0.09 mol, TEAOH). Temperature and crystallization time were the main parameters studied. X-ray diffraction (XRD), infrared spectroscopy (IR) and scanning electron microscopy (SEM) were the characterization techniques employed. The zeolites prepared showed mixed phases such as beta, MTW and ZSM-5 while only one sample treated at 150oC with 24 h of crystallization time showed a pure ZSM-5 phase (SAC-5). These preliminary results serve as a starting point for optimizing the synthesis of a specific type of zeolite using the SAC method.

A ZSM-5/MCM-48 based catalyst for methanol to gasoline conversion

A ZSM-5/MCM-48 aluminosilicate composite material as a catalyst for methanol to gasoline conversion was synthesised using a simple two step crystallisation process. The textural and structural properties of the composite were characterized using N2-adsoption, XRD, SEM and HRTEM techniques. It was revealed that the ZSM-5 phase was inter-connected with the meso-structured MCM-48 phase. The ZSM-5/MCM-48 composite catalyst was shown to possess high activity and stability with low formation of aromatic hydrocarbons in methanol to gasoline (MTG) conversion. The high activity and stability of the novel ZSM-5/MCM-48 composite were attributed to the enhanced the mass transfer properties and reduced diffusion limitations due to the widened pore size distribution and lowered pore surface acidity of the composite material.