Effect Of Dealumination Research Articles

NON-OXIDATIVE METHANE CONVERSION STUDY ON GRANULATED Mo-CONTAINING ZEOLITE CATALYSTS

The results of the study of the influence of the method of forming granular Mo-containing zeolite catalysts on their physicochemical and catalytic properties in the process of non-oxidative conversion of methane are presented. There is shown a higher catalytic activity of granular catalysts with a hierarchical porous structure, obtained without using binders, compared to a granular catalyst obtained by a conventional method of mixing powdered zeolite with pseudobemite, followed by granulation and calcination. The texture and acid characteristics of granulated zeolites and Mo-containing catalysts based on them have been studied. The effect of dealumination of granular zeolites with a hierarchical porous structure on their texture and acid characteristics, as well as on their catalytic activity in the process of methane conversion is shown. The HRTEM method shows a difference in the distribution of the active Mo-containing phase in the granulated zeolite catalysts depending on the method of their preparation. Particles with a wide size distribution (2-30 nm), which are the crystalline phase of molybdenum carbide (β-Mo2C), and Mo-containing clusters in zeolite channels are present on the surface of granular samples that do not contain a binder. The catalyst prepared with the addition of the binder is micron agglomerates consisting of sub-micron sized zeolite particles and alumina sufficiently uniformly covering the surface of the zeolite. According to elemental mapping using energy dispersive X-ray spectroscopy, it was found that the active component is uniformly distributed over the catalyst surface, but the molybdenum signal on the alumina is significantly higher, which is explained by its higher specific surface area and the availability of particles. It has been found that the method of preparing granular Mo-containing zeolite catalysts has an effect on their catalytic activity, selectivity and stability in the process of non-oxidative conversion of methane to aromatic hydrocarbons. For citation: Stepanov A.A., Korobitsyna L.L., Vosmerikov A.V., Gerasimov E.Yu., Ishkildina A.Kh. Non-oxidative methane conversion study on granulated Mo-containing zeolite catalysts. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2024. V. 67. N 8. P. 85-94. DOI: 10.6060/ivkkt.20246708.7t.

Dealumination Effect on ZSM-5 as a Bimetal Fe-Co Support for The Oxidative Desulfurization Process Catalyst

Petroleum fuel is still the main energy source today but causes environmental problems such as SOx gas emissions. The Oxidative Desulfurization (ODS) method removes sulfur from fuel under mild conditions. ZSM-5 is a catalyst framework considered promising in the ODS process but the small pores cause a steric barrier. The hydrophobic, mesoporous Fe-Co/ZSM-5Hierarchy catalyst was designed using the dealumination method with steam treatment to overcome the steric barrier and biphasic hindrances which are problems in this ODS process. The Fe-Co/ZSM-5Hierarchy catalyst is effective for the ODS process at a temperature of 45 °C, 45 min, the amount of catalyst used is 0.2 g, oxidant at an O/S ratio of 2, and without mass transfer agents. The embedded Fe-Co ratio shows effective mass activity by providing a TOF number of 205 h-1 on the Fe-Co(5)/ZSM-5 Hierarchy and 157 h-1 on the Fe-Co(15)/ZSM-5 Hierarchy catalyst.

H-Beta Zeolite as Catalyst for the Conversion of Carbohydrates into 5-Hydroxymethylfurfural: The Role of Calcination Temperature

H-Beta zeolite is a solid acid catalyst commonly utilized in the catalytic conversion of biomass resources. In this study, H-Beta zeolite was calcined at different temperatures (350, 550, 750, and 1000 °C) to explore the effects of high temperature-induced dealumination on its physicochemical properties and its catalytic ability to convert glucose into 5-hydroxymethylfurfural (HMF). It was shown that as the calcination temperature increased, the Si-O-Al bond of H-Beta zeolite was broken and its dealumination effect was enhanced. Dealumination led to the collapse of the framework of H-Beta zeolite and a reduction in the number of acid sites, which in turn reduced its catalytic performance and the efficiency of HMF formation from glucose. Furthermore, H-Beta zeolite exhibited an extraordinary catalytic ability for the production of HMF from carbohydrates. Using glucose and cellulose as substrates, superior HMF yields of 91% and 46%, respectively, were achieved under optimal reaction conditions. Further, calcination removes carbon deposits in the recovered H-Beta zeolite, but it affects the cycling stability of the catalyst. Meanwhile, the by-products formed during the synthesis of HMF from glucose catalyzed by H-Beta zeolite catalyst were also clearly detected.

Assessing the effects of dealumination and bifunctionalization on 8-membered ring zeolite/zeo-type materials in the methanol-to-olefin catalytic process

C2–C4 shorter olefins, particularly ethylene and propylene, are crucial building blocks in modern petrochemical, polymer, and chemical industries.

Effects of dealumination on the methane-combustion activity of Pd/SSZ-13 catalysts

This study investigated the effects of dealumination on Pd/SSZ-13 catalysts for methane combustion. Pd(1)/SSZ-13 (HTA), prepared by treating the catalyst hydrothermally at 750 °C, displayed extremely low catalytic activity. In contrast, Pd(1)/SSZ-13 (DeAl), prepared by treating the SSZ-13 support hydrothermally followed by Pd impregnation, exhibited superior catalytic activity for methane oxidation. Catalytic properties, including zeolite hydrophobicity and Pd location and states, were investigated by using various characterization techniques to clarify the differences between the catalysts. Most Pd species in the Pd/SSZ-13 (HTA) catalyst existed as Pd ions, which were not very active for the reaction. On the contrary, most Pd species in the Pd(1)/SSZ-13 (DeAl) catalyst existed as PdO nanoparticles at the external surface, which were highly active for methane oxidation. The study results suggested that the amount of external PdO nanoparticles should be maximized in order to make Pd/SSZ-13 catalyst highly active for methane combustion, which was achieved by dealuminating the SSZ-13 support before Pd impregnation.

SYNTHESIS OF A NEW ADSORBENT BASED ON THE MILD DEALUMINATED BINDER FREE GRANULAR Y ZEOLITE

This study investigates, for the first time, the effects of dealumination of binder-free NaY type zeolite on the adsorption properties and porous structure characteristics. In this study, BF-Y zeolite was hydrothermally synthesized from kaolin and powder NaY. BF-Y was then treated with acid to increase Si/Al ratio. X-ray Diffraction (XRED), Thermal Gravimetric Analysis (TGA), Scanning Electron Microscope (SEM), and Energy Dispersive X-Ray (EDX) have been performed for the characterization. The modified zeolite granules MBF-Y were used as an adsorbent for the removal of methylene blue MB dye from water. The influence of initial MB concentration, contact time, temperature, and adsorbent dosage on adsorption capacity and dye removal percentage on MBF-Y was investigated. The maximum dye removal was attained at a concentration of (8 * 10-6 M) which was more than 93%, and an equilibrium contact time of 60 minutes. Well-known adsorption isotherms (Langmuir, Fruendlich, and Tempkin) were used to study the adsorption mechanism of MB onto MBF-Y.

Xylene and n-Hexane Adsorption Performance of a Waste Methanol-to-Propylene Catalyst under Acid-Base Treatment

Spent methanol-to-propylene (MTP) catalysts have a large specific surface area and high porosity but are usually directly disposed of in landfills, and recycling is rare. In this study, spent MTP catalyst was moderately dealuminized with acids and etched with an alkali solvent to increase its specific surface area. A novel adsorbent was obtained. XRD, SEM, FT-IR, XRD, XRF, and MAS-NMR characterization shows that the adsorbent maintains a typical ZSM-5 zeolite structure, and the dealumination effect of H2C2O4 is better than that of HCl. HCl mainly removes the framework aluminum of the molecular sieve; H2C2O4 not only removes the framework aluminum but also dissolves some of the nonframework aluminum, which increases the BET-specific surface area and pore diameter. The spent catalyst maintains an irregular ellipsoidal shape. After alkali treatment, the surface of the spherical particles becomes rough. With increasing alkali concentration, the damage degree increases. After treatment with 4 mol/L H2C2O4 and 0.1 mol/L NaOH, the p-xylene and n-hexane adsorption capacities reach the maximum, with values of 141.04 mg/g and 106.87 mg/g, respectively, 20.7% and 16.2% greater than those before treatment. These findings indicate that modified spent MTP catalyst has the potential for application in the removal of VOCs from the air.

Dealuminated and Desilicated Natural Zeolite as a Catalyst for Hydrocracking of Used Cooking Oil into Biogasoline

<p align="justify">The modification of natural zeolite has been conducted by dealumination and desilication using HCl and NaOH treatments as a catalyst for hydrocracking of used cooking oil into biogasoline. This research aimed to study the effect of dealumination and desilication on the natural zeolite activity and selectivity of a hydrocracking process. A variety of catalysts was prepared by applying 3, 6, and 9 M HCl in the dealumination of natural zeolite to produce DNZ(3-1), DNZ(3-2) DNZ(3-3), DNZ(6-1), DNZ(6-2), DNZ(6-3), DNZ(9-1), DNZ(9-2), and DNZ(9-3) catalysts and NaOH in the desilication of natural zeolite to obtain NZB catalyst. The results showed that the dealumination and the desilication treatments affected the liquid product conversion of used cooking oil from catalytic hydrocracking. The hydrocracking of used cooking oil with NZB catalyst produced the highest gasoline fuel conversion of 94.87%. </p><p align="justify"> </p><p align="justify"> </p>

Insight into hydrothermal aging effect on deactivation of Pd/SSZ-13 as low-temperature NO adsorption catalyst: Effect of dealumination and Pd mobility

Pd/SSZ-13 samples with the same Pd loading (1 wt.%) but different Si/Al ratio (6 and 13) were hydrothermally aged at 800, 850, and 900 ºC, respectively. The Pd/SSZ-13 with a lower Si/Al ratio suffers a more severe deactivation. The Pd/SSZ-13 with a Si/Al ratio of 6 experiences structural damage due to dealumination, while the structure of the sample with a Si/Al ratio of 13 remains intact. The agglomeration of Pd2+ ions to large PdO particles on the external surface of zeolite causes the deactivation. The Pd cations are mobile during aging. Besides dealumination, the Pd2+ ions might be hydrolyzed and have a high mobility, which also results in the Pd2+ ions agglomeration. The severe dealumination causes the deactivation after aging at 900 ºC. However, the Pd mobility might be the primary reason for the decline of NO adsorption capacity of Pd/SSZ-13 after aging at 800 and 850 °C.

Removal of Saturated Monoglyceride in Biodiesel Using Adsorption and Its Effect on Low-Temperature Properties of Biodiesel Blends

Saturated monoglyceride (SMG) is a main cause of precipitate formed above cloud point of biodiesel (B100), which leads to filter plugging in diesel engine. In this work, we studied the effect of SMG content (0.1–0.7 wt%) of palm biodiesel (PO-B100) on the cloud point (CP) of diesel fuels blended with PO-B100 at different concentrations (B0, B7, B10 and B20). Euro 4 and Euro 5 diesels with a high and low aromatic content were used, respectively. The effect of SMG concentration on CP of biodiesel blends was more pronounced in case of a low aromatic Euro 5 diesel. An extent of CP change was also affected by the initial SMG concentration of PO-B100 and biodiesel blending ratios since they determined the SMG content of the final biodiesel blends. An adsorptive removal of SMG in PO-B100 was investigated by using natural zeolite as much cheaper adsorbents than commercial magnesium silicate (MS) and silica gel. The crystalline structure of natural zeolite and MS was studied by X-ray diffraction. Both MS and silica gel exhibited higher performance than natural zeolite in the SMG removal at 45 °C. To improve the SMG adsorption capacity, the natural zeolite was treated with 1 M nitric acid solution at 60 °C. The resulting modified zeolite had an increased SiO2 content, as measured by X-ray fluorescence spectroscopy, due to dealumination effect. Moreover, it showed an improved adsorption performance: the capacity of SMG adsorption was 31.5 mgSMG g-1, corresponding to a decrease of SMG content of PO-B100 from 0.7 wt% to 0.35 wt%, when using 10 wt% adsorbent loading at 45 oC for 50 min. As a result, an increase in the cloud point of biodiesel blends was significantly retarded.

Synergistic effect of dealumination and ceria impregnation to the catalytic properties of MOR zeolite

MOR zeolite has been extensively employed as a catalyst in industries. However, high Brønsted acidity in MOR leads to rapid deactivation due to coke deposition on the pore mouths; thus, the surface acidity of MOR needs to be moderated. Herein, we report a modification of MOR chemical composition via acid treatment and deposition of ceria nanoparticles using a wet impregnation method. The acid treatment successfully increases the Si/Al ratio of MOR from 8.39 to 11.58 and reduces the total acid site concentration of MOR from 990 μmol/g to 752 μmol/g. The acidity of MOR is decreased when the Si/Al ratio is increased since the quantity of Brønsted acid sites is proportional to the number of Al framework. In addition, the acid treatment also improves the external surface area of MOR. Furthermore, ceria particles were successfully deposited on the MOR surface using wet impregnation method. The ceria content of parent MOR sample is lower compared to that of preceded by the acid treatment, which may be attributed to the formation of more terminal silanol groups. Finally, catalytic test on Friedel–Crafts alkylation of toluene with benzyl alcohol shows that the synergy between dealumination and the impregnation of ceria significantly improves the activity of MOR zeolite.

Effect of dealumination on the acidity of zeolite Y and the yield of glycerol mono stearate (GMS)

Research on the production of Glycerol Monostearate from glycerol using dealuminated Zeolite Y catalysts has been carried out. Optimization of the dealumination process is conducted using the help of statistical software 10, where the variables used are acid concentration (5–7 M), temperature of dealumination (55–70 °C) and time of dealumination (2–6 h). The acidity characterization test of dealuminated Zeolite Y using ammonia and pyridine solution. Glycerol Monostearate yield was obtained by GC-MS test that was carried out on 2 samples zeolite Y catalyst with the highest value of total and surface acidity of zeolite Y which produced 2.18% and 4% yield of Glycerol Monostearate. The two samples showed that the greater the acidity, the GMS yield was also greater. Compared to previous studies it was found that ZSM-5 catalyst has a higher acidity value than zeolite Y so that the yield of Glycerol Monostearate is higher with the use of ZSM-5 than Zeolite Y.

Effect of dealumination of HZSM-5 by acid treatment on catalytic properties in non-hydrocracking of diesel

A series of modified HZSM-5 zeolites with different types of acid and different HCl concentrations treatments were synthesized, respectively. The crystal morphology, textural property and acidic property of the catalysts were characterized by XRD, N2 adsorption–desorption, NH3‐TPD, Py-IR and 27Al MAS NMR spectroscopy. The influences of acid treated types and acid solution concentrations in the pore structure, acidity and non-hydrocracking activity were investigated. The results showed that mesopores were successfully induced to HZSM‐5 zeolites after dealumination by HCl and H3PO4 treatment and the acid sites were redistributed. The acidic analysis revealed that the increase of LAS/BAS value was conducive to improving the non-hydrocracking cracking activity and gasoline yield of the samples. It was also observed that an appropriate amount of HCl treatment can not only play the role of dredge the channel of the zeolites, also introduce some new mesoporous. The hydrochloric acid treated sample (HZ-1.0HA) showed the best diesel non-hydrocracking cracking activity and gasoline yield.

Effect of dealumination on the catalytic performance of Cr-containing Beta zeolite in carbon dioxide assisted propane dehydrogenation

New active and selective catalysts for propane to propene dehydrogenation in assistance of CO2 (CO2-PDH) were prepared by chromium incorporation in siliceous SiBeta. The Cr-containing SiBeta zeolite catalysts were obtained by two-step postsynthesis preparation procedure which consist, in the first step, removal of aluminum from TEABeta zeolite with Si/Al of 17 by treatment with nitric acid solution to obtain an aluminium-free SiBeta support with Si/Al ratio of 1000 and, in the second step, various amounts of Cr were introduced into the siliceous SiBeta zeolite structure by wet impregnation. The well correlation between the number of redox Cr sites and propene yield up to 2 wt % of Cr has been determined. Comparing of catalytic activity of Cr-containing Beta zeolite catalysts with the identical Cr content (2 wt % of Cr) supported on SiBeta and AlBeta revealed that the dealumination has great impact on catalytic properties. Low acidity of SiBeta is suitable for achieving high selectivity to propene (above 80 %) while high acidity of starting AlBeta promotes propane cracking to lighter hydrocarbons. Moreover, in switch operation mode between propane dehydrogenation in presence and absence of CO2 the formation rate of propene raises in mode with CO2 only over Cr-containing SiBeta zeolite catalyst, while over Cr-containing AlBeta zeolite catalyst a negative effect on the rate of propene formation was observed.

External surface phenomena in dealumination and desilication of large single crystals of ZSM-5 zeolite synthesized from a sustainable source

Abstract Zeolite dealumination and desilication are common methods, which improve accessibility of the active sites located inside the zeolite crystallites and tune the zeolite acidity. The exact mechanism of these post-synthesis zeolite treatments remains under discussion. In this paper, a series of dealuminated and desilicated ZSM-5 zeolites are prepared using single or combined post-synthesis dealumination and desilication of large zeolite single crystals with oxalic acid and sodium hydroxide. The ZSM-5 zeolite has been synthesized using silica extracted from fly ash. Zeolite desilication results in the potholes, leaf-type structures and other clearly visible defects on the surface of zeolite crystallites, while the effect of dealumination is less pronounced. The low temperature nitrogen adsorption suggests the formation of mesopores in the zeolites formed by the voids between and in the irregular zeolite crystallites produced during post-synthesis treatments. 27Al and 29Si MAS NMR in combination with XRD data are indicative of only minor modifications of the bulk zeolite structure during dealumination and desilication. The total Bronsted acidity only slightly decreases and is not affected by the type of zeolite post-synthesis treatment. After desilication of large single crystals of ZSM-5, noticeable enhancement of the Bronsted acidity on the zeolite external surface has been detected by FTIR of adsorbed collidine. The zeolites with higher acidity on the external surface have shown higher activity in the anisole acylation with hexanoic acid. A combination of characterization techniques suggests that the dealumination and desilication of the large crystals of ZSM-5 zeolite using post-synthesis treatments respectively with acid and alkali selectively starts at the zeolite external surface.

Perengkahan n-Butana Menggunakan Katalis Nanopartikel Zeolit Alam Klaten

Increasing demand on olefins, high energy consumption of thermal cracking and oil depletion are the driving force to find new process to produce olefins. Catalytic cracking of n-butane is promising route to produce olefins. In this paper, we synthesized nanoparticle from natural zeolites by ball milling-recrystallization method and studied the effect of acid dealumination over the nanozeolites on the catalytic properties. Particle size was evaluated visually by using scanning electron microscope. X-Ray Diffraction analysis was performed to study zeolites phase and its crystallinity. Acid dealumination effect over nanosized mordenite on the acidity were evaluated by ammonia TPD and pyridine FTIR. Textural properties of zeolites were characterized by nitrogen physisorption at -196 oC. The catalysts were tested in a fixed bed reactor for n-butane cracking to olefins product. Various temperature conditions were applied ranging from 350 oC to 650 oC for n-butane cracking in a fixed bed reactor. Conversions of n-butane were 15% and 90% at 350 oC and 650 oC, respectively. Selectivity to olefins was increase from 1% at 350 oC to 47% at 650 oC.

Enhancement of Catalytic Performance of H-Clinoptilolite in Toluene Abatement from Polluted Air via Controlled Dealumination Method

AbstractIn this study, the effect of clinoptilolite dealumination on the total oxidation of toluene was reported for the first time. To avoid excess decrease of catalyst crystallinity, chemical modification of zeolite was carried out using a mild acid like oxalic acid. The catalysts were characterized by XRD, XRF, SEM, BET and TPD analyses. It was found that dealumination resulted in a significant enhancement of toluene conversion when 0.050 M acid oxalic was used for a treatment period of 2 h. Dealumination substantially changed the distribution of the concentration of acid sites of different strength and increased the surface area and porosity, so that the temperature corresponding to the maximum conversion shifts around 50 °C towards lower temperatures (in case of CLP 050). The effect of dealumination on the activity of the zeolite samples and the total oxidation of toluene was discussed in terms of Si/Al ratio, crystallinity, distribution of acid site strength and textural characteristics of the samples.

Effects of dealumination on the performance of Ni-containing BEA catalysts in bioethanol steam reforming

The effects of dealumination of BEA zeolite on the formation of nickel active sites and the performance of Ni-containing BEA zeolite catalysts in the steam reforming of ethanol have been studied. Ni-containing BEA zeolite catalysts were prepared by the impregnation of unmodified and dealuminated BEA zeolites with Ni(NO3)2 precursor. The properties of Ni10HAlBEA and Ni10SiBEA zeolite catalysts were studied by means of X-ray diffraction, 1H, 27Al and 29Si magic-angle spinning nuclear magnetic resonance, Fourier-transform infrared and Raman spectroscopy, transmission electron microscopy, temperature-programmed reduction, temperature-programmed ammonia and hydrogen desorption methods. High initial activity and selectivity of Ni10HAlBEA to hydrogen and carbon dioxide with unmodified BEA zeolite support in the steam reforming of ethanol reaction performed at 500 °C was observed. However, fast deactivation of Ni10HAlBEA catalyst, manifested in the decrease of water conversion, drop of selectivity to H2 and CO2, and increase in the selectivity to ethylene with the time-on-stream, was observed. In contrast, Ni10SiBEA zeolite catalyst showed lower initial activity but higher durability and resistance for carbon deposition. It was stated that dealumination of BEA zeolite led to the slight structural changes and simultaneously pronounced decrease of acidity. Formation of the large nickel crystallites was hindered on Ni10SiBEA zeolite catalyst. TEM and Raman spectroscopy studies indicated that deactivation of Ni10HAlBEA was related to formation of nickel mediated filamentous, graphitic and amorphous carbon deposits. Much smaller amounts of filamentous carbons were observed on the Ni10SiBEA zeolite catalyst prepared by the use of dealuminated zeolite support.

MODIFIKASI ZEOLIT ALAM SEBAGAI ADSORBEN AMMONIUM HIDROKSIDA (NH4OH)

Natural zeolite is a mineral that are widely available in Indonesia. Among many other benefits, the natural zeolite can be used as an adsorbent to reduce water pollutant caused by ammonia compounds and combination of derivatives. This research aimed to study the effect of natural zeolite dealumination on the adsorption properties of ammonium hydroxide (NH4OH). Dealumination effect was studied by varying the concentration of HNO3 (0.5 N, 5 N and 10 N). The adsorption process of NH4OH was observed by studying the adsorption time with amount of NH4OH adsorbed on the surface of the zeolite. In addition, also studied the effect of heating (calcination) after dealumination to the NH4OH uptake. In this study, NH4OH adsorbed on zeolite surface was observed by Fourier Transform Infrared (FTIR). Results were showed that the amount of NH4OH adsorbed on H- zeolite has a maximum (80.8%) at 5 N HNO3. From the calcination process, it was noted that H-zeolite undergo calcination process has higher NH4OH adsorption capacity than that of the H-zeolite without a calcination process. FTIR analysis was showed that NH4OH adsorbed on the surface of H- zeolite on BrA¸nsted acid peak.

Effects of Dealumination and Desilication of Beta Zeolite on Catalytic Performance in n-Hexane Cracking

Catalytic cracking of n-hexane to selectively produce propylene on Beta zeolite was carried out. The H-Beta (HB) (Si/Al = 77) zeolite showed higher catalytic stability and propylene selectivity than the Al-rich HB (Si/Al = 12), due to its smaller number of acid sites, especially Lewis acid sites (LAS). However, catalytic stability and propylene selectivity in high n-hexane conversions were still not satisfactory. After dealumination with HNO3 treatment, catalytic stability was improved and propylene selectivity during high n-hexane conversions was increased. On the other hand, catalytic stability was not improved after desilication with NaOH treatment, although mesopores were formed. This may be related to the partially destroyed structure. However, propylene selectivity in high n-hexane conversions was increased after alkali treatment. We successfully found that the catalytic stability was improved and the propylene selectivity in high n-hexane conversions was further increased after the NaOH treatment followed by HNO3 treatment. This is due to the decrease in the number of acid sites and the increase in mesopores which are beneficial to the diffusion of coke precursor.