Modification Of Zeolite Research Articles

Modulation of ODH Propane Selectivity by Zeolite Support Desilication: Vanadium Species Anchored to Al-Rich Shell as Crucial Active Sites.

The commercially available zeolite HY and its desilicated analogue were subjected to a classical wet impregnation procedure with NH4VO3 to produce catalysts differentiated in acidic and redox properties. Various spectroscopic techniques (in situ probe molecules adsorption and time-resolved propane transformation FT-IR studies, XAS, 51V MAS NMR, and 2D COS UV-vis) were employed to study speciation, local coordination, and reducibility of the vanadium species introduced into the hierarchical faujasite zeolite. The acid-based redox properties of V centres were linked to catalytic activity in the oxidative dehydrogenation of propane. The modification of zeolite via caustic treatment is an effective method of adjusting its basicity—a parameter that plays an important role in the ODH process. The developed mesopore surface ensured the attachment of vanadium species to silanol groups and formation of isolated (SiO)2(HO)V=O and (SiO)3V=O sites or polymeric, highly dispersed forms located in the zeolite micropores. The higher basicity of HYdeSi, due to the presence of the Al-rich shell, aided the activation of the C−H bond leading to a higher selectivity to propene. Its polymerisation and coke formation were inhibited by the lower acid strength of the protonic sites in desilicated zeolite. The Al-rich shell was also beneficial for anchoring V species and thus their reducibility. The operando UV-vis experiments revealed higher reactivity of the bridging oxygens V-O-V over the oxo-group V=O. The (SiO)3V=O species were found to be ineffective in propane oxidation when temperature does not exceed 400 °C.

Ethanol Dehydration in Fixed Bed Column Using Pellet Adsorbent From Natural Zeolite Lampung

This research is motivated by the reduced reserves of fossil fuels in Indonesia, so that fossil fuel substitutes are needed, one of which is ethanol. It's just that to make ethanol as a fuel substitute for fossil fuels, a 99% concentration is required, while the ethanol on the market only has a concentration of 96%. One of the processes that can be used to purify ethanol is the adsorption process. In this study, activation of Natural Zeolite Lampung (ZAL) was carried out to increase its adsorption ability to water contained in an ethanol-water solution. This zeolite modification process begins with ZAL pre-treatment, formation of ZAL in the form of pellets, then ZAL activation by calcination, the results of this modification are characterized through the FTIR, XRD, XRF, SEM, and BET mechanisms. ZAL has been successfully formed into pellets, this can be seen when ZAL is immersed and the ethanol-water solution is flowed, it does not change shape. The highest R2 value was obtained in the Adam Bohart equation model at a flow rate of 10 ml/minute with an R2 value of 0.9742 with the highest concentration achieved at a concentration of 98.797%.

The ‘chimie douce’ process towards the modification of natural zeolites for removing drugs and pesticides from water

AbstractBACKGROUNDDrugs and pesticides are emerging contaminants, and their presence in surface and groundwater have been increasing. Therefore, this work aims to study the modification of natural zeolite to remove these contaminants from water.RESULTSAmong the modifications carried out, hydrothermal treatment in the presence of surfactant (CTAB) was highlighted. The hydrothermal treatment with surfactant provided a structural rearrangement. As a result, the zeolite became more hydrophobic, with a smaller specific area and a more significant amount of mesopores and macropores. Changes in textural and chemical characteristics resulted in a significant increase in the removal of the evaluated pesticides and drugs. In order to evaluate the potential of zeolites to remove emerging contaminants under conditions closer to reality, the modified samples were evaluated in the adsorption process of simulated contaminated water. The maximum adsorption capacities obtained were 28.24, 3.07, and 20.06 mg g−1 for 2,4‐D, diuron, and diclofenac, respectively, using HT‐H2O_CTAB under conditions closer to real water treatment (30 °C and natural pH of the solution).CONCLUSIONThe results demonstrate that hydrothermal modification with CTAB is a promising ‘chimie douce’ technique to use natural zeolites to remove emerging contaminants. © 2022 Society of Chemical Industry (SCI).

Enhancement of the strong Brønsted acidity and mesoporosity: Zr4+ promoted framework modification of Zeolite Y

Brønsted acid of zeolite Y plays an important role in catalytic cracking reaction. However the proportion of strong Brønsted acid in conventional zeolite Y is small which limits the efficiency of transformation. This work described a way to achieve the goal of significant increasing the density of strong Brønsted acid via introducing Zr4+ into the framework of zeolite Y. The density of strong Brønsted acidity increased from 0.085 (HY) to 0.208 mmol/g ([Zr,Al]-HY). Systematic characterization results showed that the introduction of Zr4+ could produce more Si(1Al) but less Si(3Al) and Si(2Al) species in zeolite which was responsible for the high density of Brønsted acid. And abundant mesopores were also formed during the Zr4+ implanting. For the catalytic cracking results of n-octane, the conversion on [Zr,Al]-HY was 1.67 times of that on conventional HY. The apparent activation energy of cracking n-octane on [Zr,Al]-HY was reduced to 73.3%, which indicated that the increase of strong Brønsted acid had significant effect on catalytic cracking. On the other hand, a large number of mesoporous structures of [Zr,Al]-HY provided a good foundation for the catalytic cracking of steric hindered 1.3.5-triisopropylbenzene (1,3,5-TIPB).

The effect of acid treatment and calcination on the modification of zeolite X in diesel fuel hydrodesulphurization

AbstractFaujasite (X, Y) zeolites are considered the main and important catalysts in hydrorefining processes. In order to obtain zeolites with higher acidity and volume of mesopores, post‐synthesis modification, dealumination by different pickling techniques (using ethylenediamine tetraacetic acid [EDTA] chelating agent), and thermal treatment (calcination) were employed. The dealumination process led to the removal of the aluminum atoms from the zeolite structure and a rise in acidity while maintaining the zeolite crystalline lattice. X‐ray diffraction (XRD), atomic absorption spectrometry (AAS), Fourier‐transform infrared (FT‐IR), field‐emission scanning electron microscopy (FE‐SEM), Brunauer–Emmett–Teller (BET), and temperature‐programmed desorption of ammonia (NH3‐TPD) analyses were performed to study the physicochemical characteristics of the zeolite and catalysts prepared. Atomic absorption spectroscopy showed an increase in the Si/Al ratio in the modified zeolites. Measuring the surface area of zeolite and the volume of the pores through BET‐BJH and t‐plot methods indicated a reduction in the surface area and an increase in the volume of the pores. Under the influence of the dealumination process, the volume of the mesopores in the modified zeolites increased from 0.056 cm3 g−1 in the initial zeolite (Na‐X) to 0.2105 cm3 g−1 (zeolite X1). The acidity of the modified zeolites (X1) increased from 0.32–0.95 mmol NH3/g. The application of the catalysts containing X1 zeolite in the hydrodesulphurization (HDS) process yielded a product with less sulphur (conversion = 87.5%).

Enhanced light olefins production via n-pentane cracking using modified MFI catalysts

n-pentane catalytic cracking was studied over a series of MFI zeolites with varying SiO2/Al2O3 ratios (30, 80, 280, 500, and 1500) using a fixed-bed reactor operated at temperature 550–650 °C. Other MFI zeolites (SiO2/Al2O3 = 280) with various crystal morphology and size (such as large crystal and nano size) were also synthesized and tested for n-pentane cracking. The effects of MFI zeolite modification with ammonia and phosphorus on its physiochemical properties and catalytic activity were investigated. Among the parent MFI zeolites, MFI (280) demonstrated high selectivity (51%) towards light olefins (C3=/C2= = 0.7) at 650 °C with undesired C1–C4 alkanes (38%). Surface modified MFI (280) zeolites of different crystal size and morphology showed improvement towards propylene selectivity by suppressing undesired reactions. Phosphorous-modified MFI zeolite with a large crystal size was found to improve light olefin selectivity (52.2%) with C3=/C2= = ∼1.3 and reduce undesired C1–C4 alkanes (8%) formation due to suppressed strong acidic sites. The characterization and evaluation results for the modified MFI (280) revealed that the incorporation of phosphorous created moderate acidic sites, which were stabilized by some non-framework aluminum species, thereby leading to suppressing the formation of undesired C1–C4 alkanes with improved light olefins selectivity.

Modification of Beta Zeolites and Their Application in Catalytic Oxidation of Propane

AbstractIn this manuscript, Beta zeolites are modified by liquid phase ion exchange method and high temperature roasting method to achieve the effect of catalytic degradation of propane. After modification by hydrochloric acid, nickel nitrate and zinc nitrate, the specific surface area, pore size and pore volume of Ni−Zn−H‐Beta zeolites catalyst increased, which greatly improved the catalytic degradation effect of propane. By high temperature roasting, the effect of conventional calcined catalyst is better than that of microwave calcined catalyst. When the gas composition is air and 1 % propane, the gas flow is 100 ml/min, the reaction temperature is 300 °C, the optimum preparation conditions of the catalyst are Ni: Zn=2 : 1, HCl pickling temperature is 70 °C, conventional roasting temperature is 500 °C, and the holding time is 60 min, the catalytic activity of Ni−Zn−H‐Beta zeolites is the best, and the degradation rate of propane is 79.6 %.

Influence of adding a modified zeolite-Y onto the NiMo/Al2O3 catalyst utilized to produce a diesel fuel with highly reduced sulfur content

In order to make a Na–Y zeolite with Si/Al ratio of 2.27 more acidic with a higher volume of mesopores, a combination of different and consecutive methods including; chemical (i.e.; utilizing different compounds, such as NH4F and EDTA) and thermal/hydrothermal (i.e.; implementing calcination/steaming) methods, were employed for modification and dealumination. The combination of acidic-hydrothermal dealumination method led to a further structural collapse compared to that of the acidic calcination. In comparison with the other dealumination methods, the fluorination strategy (i.e.; utilizing NH4F) resulted in a zeolite with higher crystallinity, acidity, and specific surface area. The modified and dealuminated zeolites were employed to prepare the catalyst support of FAU + Al2O3 for the HDS process. The sulfidation and performance evaluation of the prepared catalysts were carried out in a fixed bed microreactor. Then after, the effects of zeolite modification during the dealumination process, especially acidity and Si/Al ratio variations, upon the activity of NiMo/FAU + Al2O3 catalyst were understudied. Results indicated that, the enhanced performance of the catalysts containing the modified zeolites in removing of the sulfur containing aromatic compounds, as well as their longer observed lifetime in terms of lower coke deposition levels were obtained. The removal of the sulfur containing compounds increased with acidity so that the maximum removal (i.e.; of conversion = 93%) was determined using Cat-F-AT-Cal catalyst containing the zeolite modified by acid treatment-calcination together with fluorination. In addition, the highest performances in terms of removal of aromatic compounds and catalyst lifetime (i.e.; due to lower coke deposition) were shown by the Cat-AT-St and Cat-AT-Cal catalysts, respectively. These species contained the zeolite modified through the acid treatment-steaming and acid treatment-calcination methods, respectively.

Succinic Acid-Assisted Modification of a Natural Zeolite and Preparation of its Porous Pellet for Enhanced Removal of Ammonium in Wastewater Via Fixed-Bed Continuous Flow Column

Succinic Acid-Assisted Modification of a Natural Zeolite and Preparation of its Porous Pellet for Enhanced Removal of Ammonium in Wastewater Via Fixed-Bed Continuous Flow Column

Ion-Exchange Modification of Zeolite for the Controllable Catalytic Transformation of Diols and Selective Conversion of 1,2-Butanediol to Butanal

Ion-Exchange Modification of Zeolite for the Controllable Catalytic Transformation of Diols and Selective Conversion of 1,2-Butanediol to Butanal

HZSM-5 zeolite modification and catalytic reaction mechanism in the reaction of cyclohexene hydration.

This study investigated a three-phase (liquid–liquid–solid) reaction system of cyclohexene hydration where the catalyst was hydrophilic at the bottom of the water phase. Cyclohexene conversion was low since it was difficult for it to come into contact with the oil. The HCl-OTS-HZSM-5 catalyst was prepared by acid and alkylation modification, then subsequently characterized. Acid modification enabled HZSM-5 zeolite to remove some aluminum atoms, increasing specific surface area, pore volume, and acid sites. N-octyltrimethoxysilane (OTS) was grafted onto the HZSM-5 zeolite surface, i.e., alkylation modification, to improve the contact area between immiscible reactants. Consequently, cyclohexene conversion reached 24.07%. Cyclohexene hydration was calculated using the 34T cluster model, and bridging hydroxyl and water molecule adsorption sites were explored. Simulations confirmed that the reaction energy barrier for the HCl-OTS-HZSM-5 catalyzed hydration reaction = 46.67 kJ mol−1, considerably less than that with HZSM-5 zeolite (73.78 kJ mol−1). The theoretical results reasonably explain the experiments and provide guidance to prepare catalysts with high catalytic activity.

Hzsm-5 Zeolite Modification and Catalytic Reaction Mechanism

Hzsm-5 Zeolite Modification and Catalytic Reaction Mechanism

Stabilization of Pb, Cd, and Zn in soil by modified-zeolite: Mechanisms and evaluation of effectiveness

As a type of soil stabilization material, zeolite has good cation exchange ability and synchronous stabilization potential for multiple active heavy metal cations in soil. However, natural zeolite contains relatively high amounts of impurities, and has a single heavy metal stabilization mechanism, which limits its capacity to stabilize heavy metals in soil. To develop a stabilization material that could efficiently stabilize several heavy metals simultaneously, in the present study, modified zeolite (MZEO) was prepared via NaCl pretreatment, chitosan modification, modified chitosan loading, and CaSiO3 modification to enable Pb, Cd, and Zn stabilization in soil. The aim of the present study was to explore zeolite modification technologies, reveal the stabilization mechanism of polymetallic contaminated soil and evaluate the stabilization effects of MZEO. According to the results, the modification treatment increased the cation exchange capacity of MZEO nearly 8-fold, the specific surface area 3.4-fold, and its internal pore structure was richer, with more adsorption sites. The appearance of a -NH2 absorption bands confirmed the loading of chitosan successfully, and the modification enhanced the heavy metal stabilization mechanism. Upon the addition of MZEO to Baiyin soil, the chemical morphologies of heavy metals changed, which reduced the weak acid extracted forms of Pb, Cd, and Zn in the soil by 21%, 10%, and 19%, respectively. The potential mechanisms of free heavy metal reduction were ion exchange with Na in MZEO, heavy metal mineral formation by Al replacement in the crystal lattice, and bonding with SiO32− formed by the hydrolysis of MZEO-loaded synaptic CaSiO3 particles, to form silicate precipitation. MZEO application minimized heavy metal leaching risk in the soil and heavy metal biological/plant accessibility, with potential economic benefits. MZEO has promising applications in polluted soil remediation.

INVESTIGATION OF THE FEATURES OF NICKEL-MODIFIED MORDENITE ZEOLITES

Zeolites are wide used materials in a range of processes of chemical, petrochemical, and nutritional industry. They are the active catalysts and sorbents, in particular, zeolites are characterized by high efficiency towards extraction of heavy and radioactive metals from the aqua medium. An important factor of high zeolite catalyst activity is preserving the integrity of the crystal structure. The purpose of this research was to check out the features of MOR zeolite modifications with nickel by means of low temperature nitrogen adsorption/desorption, IR-spectroscopy, and X-Ray Diffraction (XRD). Using ion exchange and following calcination the hydrogen form of zeolite was obtained. The last was impregnated by nickel in quantity of 1, 5, and 15 wt. %. The investigations of nickel-modified samples demonstrated that MOR-type zeolite was relatively resistant to the used manipulations. However, the hysteresis loops of their isotherms are observed. The last can be connected with mesoporosity appearance. The degree of zeolite destruction is found out to increase with rise of nickel content in the samples. Based on IR spectra analysis by means of checking out the ratio between intensity of bands at 560 and 440 cm-1 using Gaussian function in Origin medium the same conclusions were drawn. Crystalline structure of mordenite was confirmed by using XRD method, but minor quantitative destruction cannot be recognized without application of methods of the internal and external standards.

Methanol to olefins conversion: state of the art and prospects of development

The production of olefins by catalytic transformation of methanol on zeolites and zeotypes is of great interest to scientists and specialists in various fringe areas of national economy. Due to implementation of this process on industrial level, the attention gradually shifts from scientific studies devoted to the synthesis and modification of zeolites and zeotypes with different structure to investigation of pilot and industrial plants and determination of the main economic and environmental characteristics of both the existing and the future plants. In 2019, the development of 26 production sites in China with the annual output of 14 million tons of ethylene and propylene was licensed and 14 plants with the total capacity of 7.67 million tons of ethylene and propylene were launched. The created plants provide a complete cycle of coal processing, which consists of coal gasification units yielding syngas, units for the synthesis of methanol and olefins, their refinement and production of polyethylene and polypropylene. The total output of ethylene and propylene at the launched plants was more than 21 million tons. The paper presents a review of publications on the development and modification of catalysts as well as the technological, economic and environmental aspects of olefins production from methanol, which appeared in foreign journals in the recent five years.

Modified Zeolite as Purification Material in Wastewater Treatment: A Review

Natural zeolite is a hydrated aluminosilicate substance that has excellent ion exchange and adsorption properties and is environmentally and economically friendly. This review describes the current application and modification of zeolite in wastewater treatment using acid and surfactants, zeolite composites (such as zeolite membranes), permeable reactive barriers and photocatalysts. The properties of zeolite as well as the regeneration and desorption of cast-off zeolite are briefly reviewed. Modifications are made to improve the capability of zeolite in wastewater treatment facilities. Furthermore, this review proposes the integration of zeolite and other available technologies to treat emerging pollutants in wastewater. Different types of zeolite (natural and synthetic zeolite of different origins) are compared, and their properties are evaluated. Different type of pollutants and treatment methods involving zeolite are also discussed. Zeolite is enhanced to solve the problem of various pollutants in wastewater.

Modification of zeolite with metallic ions improves the immobilization of phytase

Phytase is an enzyme applied in several fields, but its wider use is still limited due to its high cost and poor stability, which can be overcome using immobilization techniques. Zeolites are promising support materials for enzyme immobilization, due to their attractive properties, including the capacity for modification using a simple ion exchange procedure, enabling better chemical interaction with proteins. In this work, investigation was made of the immobilization of phytase onto zeolites modified with metallic ions (Ag, Cd, Zn, Cu, Ca, Mg, and Ni). The zeolite modified with nickel reached immobilization yield of 66%, while the recovered activity (150%) indicated activation of the catalytic activity due to the presence of the metallic ion. The immobilized phytase showed excellent performance under conditions of acidic pH, reaching a relative activity up to 7 times higher than observed for its free form. Furthermore, it was possible to recover and reuse effectively the zeolite-Ni/Phytase derivative in at least 4 consecutive cycles of phytate hydrolysis reaction. The phytase immobilized onto zeolite modified with nickel presented improved properties, expanding the range of potential applications of this important enzyme. These findings demonstrate an efficient and simple protocol for enzyme immobilization onto zeolites modified with metallic ions.

Phosphoric Acid Modification of Hβ Zeolite for Guaiacol Hydrodeoxygenation

Regulating the acid property of zeolite is an effective strategy to improve dehydration of intermediate alcohol, which is the rate-determining step in hydrodeoxygenation of lignin-based phenolic compounds. Herein, a commercial Hβ (SiO2/Al2O3 = 25) was modified by phosphoric acid, and evaluated in the catalytic performance of guaiacol to cyclohexane, combined with Ni/SiO2 prepared by the ammonia evaporation hydrothermal (AEH) method. Incorporating a small amount of phosphorus had little impact on the morphology, texture properties of Hβ, but led to dramatic variations in acid property, including the amount of acid sites and the ratio of Brønsted acid sites to Lewis acid sites, as confirmed by NH3-TPD, Py-IR, FT-IR and 27Al MAS NMR. Phosphorus modification on Hβ could effectively balance competitive adsorption of guaiacol on Lewis acid sites and intermediate alcohol dehydration on Brønsted acid sites, and then enhanced the catalytic performance of guaiacol hydrodeoxygenation to cyclohexane. By comparison, Hβ containing 2 wt.% phosphorus reached the highest activity and cyclohexane selectivity.

Microwave synthesis of zeolites and their related applications

Zeolites are an emerging class of crystalline, nanoporous, inorganic material with regular micropores and highly tunable functionalities. Zeolites have been proposed as ideal materials for applications in catalysis, adsorption, and biomedicine due to their notable intrinsic features such as accessible void space, large surface area, and strong acidity. Microwave radiation is a robust technology that can quickly and efficiently prepare uniform and controllable zeolites that enable remarkable functions. We first review the current research progress in, and the fabrication of, zeolites using microwave technologies, and the related application. After a brief introduction to microwave theory and modification of zeolites, the discussion focuses on the five main microwave technologies for the synthesis of zeolites, that include microwave irradiation, microwave assisted hydrothermal synthesis, microwave assisted aging synthesis, microwave assisted ionothermal synthesis, and other microwave related methods. Some critical applications such as catalysis (NO x reduction, CO 2 reduction, and Fenton), gas sensing and CO 2 capture, and biomedicine are selected and discussed in detail. Finally, a summary and perspectives on research that may lead to the future development of this blossoming field. • Discuss the microwave theory and modification of zeolites. • Highlight recent achievements in manufacturing zeolites via microwave synthesis. • Some applications of such zeolites in catalysis, gas sensing and CO 2 capture, and biomedicine follow. • Comment on remaining challenges and provide prospects for further developments in this blossoming field.

A new Method for the Removal of Ammonium from Drinking Water Using Hybrid Method of Modified Zeolites / Catalytic Ozonation

Introduction: Ammonia in form of ammonium ions is toxic and could decrease the dissolved oxygen in water and endanger the aquatic life. The aim of this study is the removal of ammonium using oxidation and adsorption by catalytic ozonation and clinoptilolite zeolite, respectively. Methods: The research method is Experimental. First, optimal pH of ammonium adsorption on carbon catalyst (5 g/L), Garmsar and Firoozkooh zeolites and oxidation were determine. Then, in catalytic ozonation process, the effect of other variables on ammonium removal efficiency such as the concentration of carbonic catalyst (0.5- 50 g/L) and the reaction time were investigated. Then the effect of retention time and adsorbent concentration on adsorption of the remaining ammonium and nitrate produced by the oxidation process using zeolites and their modifications were determined. Resuts: The results showed that optimum pH for the ammonium adsorption process by carbon catalyst, catalytic ozonation and zeolite was 8, 9 and 8, respectively. However, the optimum pH 4 was determined for nitrate removal. The highest ammonium absorption capacity was related to natural Firoozookh zeolite and 18.5 mg/g, and the effect of ligand and acid modification decreased 12 and 14% of absorbed capacity, respectively. It is also, the highest nitrate removal efficiency was related to Garmsar ligand modified zeolite (98%) and an absorption capacity of 11.2 mg/g. In the COP/absorption process the concentration of ammonium was decreased to 0.6 m /L. Conclusion: This method effectively eliminates ammonium, and the modification of zeolite with cationic surfactant increases the efficiency of nitrate removal and the concentrates of all pollutants are brought below standards.