Number Of Strong Acid Sites Research Articles

Exploring the efficient catalytic decomposition behavior of AsH3 over HZSM-5 molecular sieve based on in situ DRIFTS characterization

Existing processes for transforming arsine (AsH3) into toxic arsenic oxides (AsxOy) through catalytic oxidation do not meet economic requirements. In contrast, the catalytic decomposition method stands out due to its ability to both remove AsH3 and obtain elemental arsenic (As0) as a valuable product. A series of blank molecular sieves (HZSM-5, 13X, MCM-41, and TS-1) was applied to the catalytic decomposition performance of AsH3. At a catalytic decomposition temperature of 100 ℃, the HZSM-5 zeolite exhibited exceptional performance, achieving a D90% value (the duration for which the AsH3 removal efficiency remained above 90 %) exceeding 40 h. Moreover, up to 83.1 % of the product was As0. Comprehensive characterization revealed that the surface of the HZSM-5 zeolite contained a large number of strong acid sites, which played a key role in As0 generation. In situ diffuse reflectance infrared spectroscopy further revealed the activation behavior of O2 at the Brønsted acid sites on HZSM-5. To assess its suitability in industrial applications, the AsH3 removal performance of the HZSM-5 molecular sieve was investigated in the presence of actual gas components (CO, H2S, PH3). This study provides new ideas for the effective catalytic decomposition of AsH3 and the recovery of valuable products in industry.

Synthesis of hierarchical mordenite by solvent-free method for dimethyl ether carbonylation reaction.

A series of hierarchical mordenite (MOR) catalysts were synthesized by adding soft templates via the solvent-free method. The influence of different kinds of soft templates on the structure, morphology and acid sites of mordenite were systematically characterized. The characterization results revealed that the addition of soft templates could successfully introduce hierarchical structure into the system while maintaining good crystallinity. The specific surface area and pore volume became larger. Surfactants could also affect the amount and distribution of acid sites, which in turn would affect the dimethyl ether carbonylation activity. Compared with cationic and nonionic surfactants, the addition of anionic surfactants such as sodium dodecyl benzene sulfonate could result in more Al species to preferentially enter into the 8 member ring, thus enhancing the amount of active sites for the carbonylation reaction while weakening the strength. Meanwhile, the addition of sodium dodecyl benzene sulfonate could also reduce the number of strong acid sites in the 12 member ring and obviously improve the carbonylation performance.

Performance of manganese-based catalyst comprising zinc oxide obtained from spent dry batteries for hydrocarbon oxidation

This study explores the potential of using spent dry batteries (SDBs) as catalysts to reduce environmental damage. The SDBs were separated into black mass (BM) and zinc rod (ZR), and the ZR material was treated with sulfuric acid to produce zinc oxide (ZO). Manganese (Mn)/ZO catalysts were synthesized with different Mn loadings and tested in the removal of o-xylene, toluene, and benzene. The results show that increasing Mn loading on ZO from 5.0 wt% to 30.0 wt% increased the catalytic decomposition of pollutants. The Mn species were well-dispersed on the ZO surface and existed in the oxidation states of Mn2+, Mn3+ and Mn4+, as confirmed by STEM/EDS and XPS, respectively. As Mn loading amount increased, the number of strong acid sites and the ratio of lattice oxygen to adsorbed oxygen (O 1sla/O 1sad) on the surface of the Mn/ZO catalyst increased, and the reduction temperature by H2 decreased. These surface properties had a significant impact on the catalytic activity. This study proposes a promising method that can contribute to both waste management and air quality improvement by recovering catalytic materials from SDBs and using them as catalysts for hydrocarbon removal.

Numerical and statistical determinations of the controlling factors in biomass-derived alcohol dehydration over La-incorporated γ-Al2O3 catalysts

This study aimed to develop a sustainable and renewable production process for linear α-olefins (LAOs) through the dehydration of alcohols. Lanthanum (La)-incorporated γ-Alumina (Al2O3) was selected as the catalyst, with a loading of up to 10 wt%. The addition of La modified the properties of Al2O3, including its acidity and basicity. The prepared catalysts were then used to dehydrate 1-octanol, resulting in the selective production of 1-octene due to the suppression of isomerization activity by lanthanum oxide (La2O3) species anchored on Al2O3, which caused a significant decrease in the number of strong acid sites of Al2O3. The effects of temperature and La loading on the dehydration and isomerization rates were also investigated. The results revealed that the reaction temperature had a stronger influence on the isomerization rate, while the La loading had a greater impact on the dehydration rate. The addition of 5% La to Al2O3 enabled the selective formation of 1-octene with high yield (90.9%), purity (92.3%), productivity (69.9 mmol1-octene gcat–1h−1), and moderate separation energy (317 kJ mol–1h−1) to achieve 99% 1-octene purity. At a comparable 1-octene productivity of 66–67 mmol1-octene gcat–1h−1, the addition of 5 wt% La resulted in a lower separation energy (290.3 kJ mol–1h−1) than that of Al2O3 (349.4 kJ mol–1h−1). This finding is particularly beneficial in the production of poly α-olefins that requires high purity LAOs.

Design and identify the confinement effect of active site position on catalytic performance for selective catalytic reduction of NO with NH3 at low temperature

In heterogeneous catalysis, the migration and aggregation of active nanoparticles has always been a challenging problem in catalyst design. Two types of confined catalysts, including the pore confined Pore-CeW/OMT and framework confined FW-CeW/OMT were successfully designed for NH3-SCR process in this work. Experimental results revealed that the framework confined structure could effectively prevent the migration and aggregation of highly dispersed nanoparticles on catalyst. Benefiting from the structural advantages of ordered mesopores TiO2 (OMT), large specific surface area as well as abundant active sites could be supplied for catalytic reaction. It should be noted that citric acid pretreatment was essential for confined catalyst activation. The activation treatment could dramatically enhance catalyst surface acidity, especially a large number of strong acid sites were supplemented, resulting in significantly enhancement of catalytic activity at high temperature. Furthermore, it could also accelerate reduction of Ce4+ to Ce3+ and generate more active oxygen species, which resulted in a significant improvement in its low-temperature catalytic activity. Owning with strong surface acidity as well as framework confinement effect, the unique ordered mesoporous TiO2 framework could inhibit SO2 adsorption and protect active sites from SO2 attacking. Thus, the framework confined FW-CeW/OMT exhibited wide operating temperature window, good thermal stability, as well as strong sulfur resistance in NH3-SCR process.

The Influence of Inserted Metal Ions on Acid Strength of OH Groups in Faujasite

The number and the strength of acid sites in catalysts have paramount importance on their efficiency. In zeolites chemistry, increased content of framework Al in zeolites gives a higher number of strong acid sites. Their strength can be a disadvantage in catalytic reactions (e.g., methanol to olefins conversion) due to undesired secondary reactions of coke formation. Here, the Faujasite type of zeolite with higher content of Al has been used for investigating the role of defects in structure and inserted (wet impregnation and thermal treatment) metal cations (Mg, Co, Ni, Zn) on the strength of OH acid sites. Desorption of deuterated acetonitrile, as a probe molecule, was used for OH groups acid strength measurements at different temperatures (150, 200, and 300 °C).

Reaction regeneration cycle of Mo/HZSM-5 catalyst in methane dehydroaromatization with the addition of oxygen-containing components

Reaction regeneration cycle of methane dehydroaromatization (MDA) with oxygen-containing gas components was studied. XRD, BET, Raman, NH3-TPD, O2-TG/DTG, TEM and 27Al-NMR were used to monitor textural structure, Mo species, and acid sites of catalyst before and after regeneration. Addition of oxygen components can extend reaction time per pass but cannot prevent the deactivation of regenerated catalyst. MoO3 species, acidity, and texture properties of Mo/HZSM-5 was identical after first regeneration, which may account for complete recovery of methane conversion and aromatic formation. During regeneration, the inevitable increase in Mo species size disrupts carbon deposition and significantly reduces methane dissociation. The crystallinity and number of strong acid sites of Mo/HZSM-5 catalyst decreased to a stable level before the collapse of zeolite framework without hindering aromatic formation. The recovered large-sized Mo species may accelerate the collapse of zeolite framework, irreversibly destroying Mo/HZSM-5 catalyst.

A green approach for template free synthesis of Beta zeolite incorporated in ZSM-5 zeolite to enhance catalytic activity in MTG reaction: Effect of seed nature and temperature

A new composite zeolite, ZSM-5/Beta, was developed by incorporating Beta zeolite into the synthesis gel of ZSM-5 zeolite. Beta and ZSM-5 zeolite have been prepared from rice husk ash without using an organic template. First, the effect of synthesis temperature and seeding agent on structural properties of Beta zeolite was investigated. Then, prepared Beta zeolite was added to the ZSM-5 structure with the hydrothermal method. The prepared samples were characterized by X-ray diffraction, field emission scanning electron microscopy, N2 physical adsorption, and temperature-programmed ammonia desorption techniques. Results indicated that the synthesis at a temperature of 150 °C and using Na-Beta seeds showed suitable crystallinity as well as textural properties. Furthermore, the crystalline structure of ZSM-5 wasn't damaged by the addition of Beta zeolite. The incorporation of Beta zeolite into the ZSM-5 structure increased the total pore volume by 45%. The micropore volume and the mesopore volume also increased by 2% and 300%, respectively. Using composite zeolite led to tuning the catalyst acidity. The catalytic activity of this new ZSM-5/Beta composite structure was evaluated in the MTG process at 400 °C, WHSV of 20 h−1 and atmospheric pressure. The results illustrated that over this composite catalyst, the selectivity to alkylated aromatics increased by almost 13% compared to the initial ZSM-5 zeolite. Furthermore, gasoline production yield and catalyst lifetime also increased by 9% and 61% respectively compared to the initial ZSM-5 zeolite. The better performance of the composite zeolite can be ascribed to its higher mesoporous volume and lower acidity. The composite catalyst has a lower number of acid sites, especially the number of strong acid sites that are one of the main factors in coke deposition.

Enhancing aromatics and olefins yields in thermo-catalytic pyrolysis of LDPE over zeolites: Role of staged catalysis and acid site density of HZSM-5

The present work deals with the thermo-catalytic pyrolysis of LDPE (low-density polyethylene) in lab-scale one- and two-stage test rigs over HZSM-5 catalysts featuring different acid site densities. In the first part of this work, the influence of catalyst-to-feed ratio and temperature (in conjunction with the acid site density of HZSM-5) on the product distribution was studied with an aim to identify the optimum operating conditions for the enhanced production of aromatics and light olefins. For this purpose, one-stage thermo-catalytic pyrolysis was performed in which catalysts were mixed with LDPE pellets for in-situ catalysis. In the one-stage catalytic pyrolysis, the catalyst sample with the highest acid site density gave the highest concentration of aromatics (ca. 55%) in the pyrolysis oil with a mono-aromatics fraction of over 50% that consisted mainly of BTEX (benzene, toluene, ethylbenzene and xylenes) compounds. The highest C2-C4 olefins concentration (ca. 65%) in the pyrolysis gas was obtained when the sample with the lowest acid site density was used. In the two-stage catalytic pyrolysis (ex-situ catalysis), the concentration of aromatics in the pyrolysis oil reached over 77% with a mono-aromatics fraction of ca. 72% that contained mainly BTEX compounds, when the most acidic catalyst was used. When the catalyst with the lowest number of strong acid sites was employed, the high content of C2-C4 olefins in the pyrolysis gas remained almost independent of the reactor configuration. These findings might provide important new insights for the chemical recycling of plastic wastes.

Tuning Metal‐Support Interaction and Surface Acidic Sites of Ni/Al2O3 by Dopamine Modification for Glycerol Steam Reforming

AbstractIn this work, a universal dopamine modification strategy is used to improve the catalytic performance of Ni/Al2O3 for hydrogen production in glycerol steam reforming (GSR). Ni/Al2O3 showed poor catalytic stability with rapid deactivation after 8 h of reaction in GSR. Glycerol conversion and hydrogen selectivity were significantly higher for dopamine‐modified Ni/Al2O3 (by 98 % and 95 %, respectively) and this improved performance was maintained well for 21 h in the stability test. The protective carbon shell derived from dopamine was formed easily on the Ni/Al2O3 surface, the aggregation of Ni nanoparticles was inhibited, and the dispersion of Ni nanoparticles was improved. The electron‐donating effect of amino group to Ni2+ weakened the Ni‐Al2O3 interaction, and then promoted the reduction of the Ni species. In addition, the decrease in the number of strong acidic sites reduced the amount of carbon deposition on dopamine‐modified Ni/Al2O3. The moderate metal‐support interaction was more conducive to the formation of filamentous carbon, which collectively contributed to the increased catalytic stability of dopamine‐modified Ni/Al2O3. The facile dopamine‐modified method significantly improves the catalytic performance and can be generalized to other catalytic reaction that involve sintering and carbon deposition issues.

Synthesis and purification of glycolic acid from the mixture of methyl levulinate and methyl glycolate via acid-mediated hydrolysis reactions and extraction

Biomass-derived methyl glycolate (MG) contains methyl levulinate (MLE). Herein, MLE was separated from MG through acid-mediated hydrolysis reactions and liquid–liquid extraction. H-form β zeolite (Hβ) exhibited higher MLE conversions up to 87.7% compared to other acids. In contrast, MG was much less converted on Hβ. The product levulinic acid could be readily extracted with dimethyl carbonate. The overall content and recovery rate of glycolic acid reached 99.59 wt% and 92.7%, respectively. Control experiments, FTIR, contact angle, and TG-MS results proved that MLE was preferentially adsorbed on slightly hydrophobic Hβ, and DFT calculations verified that the MLE hydrolysis reaction energy barriers were smaller by 2–12 kJ/mol compared to MG. Both effects promoted the transformation of MLE on Hβ. Hβ could be reused at least six times and be regenerated by calcination. Due to dealumination, the number of acid sites on the regenerated Hβ was decreased by 67% while number of strong acid sites was elevated. This paper can shed light on the separation techniques of carboxylic esters via reactive strategies.

High-performance composite H-ZSM-5/alumina catalyst for the methanol-to-ethylene conversion

A series of extruded H-ZSM-5/alumina composite catalysts were prepared and characterized using N2 sorption isotherm, transmission electron microscopy, scanning electron microscopy, infrared spectroscopy, X-ray diffraction, NH3-TPD, and pyridine adsorption. The methanol conversion over the as-prepared catalyst as well as its components was studied at 500 °C. The catalysts with H-ZSM-5/alumina ratio 3/1 and 1/1 (by mass) catalyst exhibited the highest ethylene selectivity (up to 44%) and the ethylene/propylene ratio up to 10/1, whereas zeolite H-ZSM-5 demonstrated the propylene selectivity up to 30% and the ethylene/propylene ratio 1/8. In contrast, the catalyst with the H-ZSM-5/alumina ratio 1/3 demonstrated no activity toward olefins synthesis. The as-prepared H-ZSM-5/alumina catalysts have a long lifetime in the methanol-to-hydrocarbons conversion, which is several times higher compared to pure zeolite H-ZSM-5. The catalyst regeneration results in recovering the initial catalytic activity. The obtained findings reveal that embedding microporous zeolite in the mesoporous alumina matrix facilitates the mass transfer limitations and decreases the number of strong acid sites. These factors govern an essential performance of the as-prepared catalyst in the methanol-to-ethylene reaction.

Nitrogen Monoxide and Soot Oxidation in Diesel Emissions with Platinum–Tungsten/Titanium Dioxide Catalysts: Tungsten Loading Effect

Compared with Pt/TiO2, tungsten-loaded Pt–W/TiO2 catalysts exhibit improved activity for NO and soot oxidation. Using catalysts prepared by an incipient wetness method, the tungsten loading effect was investigated using Brunauer–Emmett–Teller surface areas, X-ray diffraction, transmission electron microscopy (TEM), CO pulse chemisorption, H2 temperature-programmed reduction, NH3 temperature-programmed desorption (NH3-TPD), and pyridine Fourier transform infrared (FT-IR) spectroscopy. Loading tungsten on the Pt/TiO2 catalyst reduced the platinum particle size, as revealed in TEM images. CO pulse chemisorption showed that platinum was covered with tungsten and the dispersion of platinum decreased when 5 wt.% or more of tungsten was loaded. The NH3-TPD and pyridine-FT-IR results demonstrated that the number of strong acid sites and Brønsted acid sites in the catalyst were increased by the presence of tungsten. Therefore, a catalyst containing an appropriate amount of tungsten increased the dispersion of platinum, thereby increasing the number of active sites for NO and soot oxidation, and increased the acidity of the catalyst, thereby increasing the activity of soot oxidation by NO2

Eu3+ ions doped Bi2SiO5 as a novel solid acid catalyst for methyl oleate production: Ultrasonic hydrothermal synthesis, characterization, catalytic activity and kinetics

To the best of our knowledge, the Eu3+ ions doped Bi2SiO5 catalysts (Eu3+/BS30) synthesized by means of ultrasonic-assisted hydrothermal method as solid catalysts for oleic acid esterification with methanol has not yet been reported till now. The effect of Eu3+ ions doping on the physicochemical and optical properties of Bi2SiO5 catalyst was investigated by the XRD, HR-TEM, BET, NH3-TPD and UV–vis/DR techniques. Further, the catalyst doped with the highest Eu3+ ions loading (0.07Eu3+/BS30) not only showed the smallest particle size but also possessed the longest nano-rod particle compared to the other catalysts. It was noteworthy that the BET surface area of 0.07Eu3+/BS30 catalyst was about 79% larger than the undoped one (BS30). Interestingly, the 0.07Eu3+/BS30 catalyst not only exhibited the largest acidity but also possessed the largest number of strong acid sites compared to the other catalysts. It was observed that the esterification conversion of Bi2SiO5 catalyst at optimized reaction conditions increases significantly from 92% to a maximum of 99% with an increase of Eu3+ ions loading from 0.01 to 0.07 mol. Ultimately, the 0.07Eu3+/BS30 catalyst was showed an excellent reusability as it preserved activity of 94% after five catalytic runs without considerable loss in activity.

Effects of alkali metal poisoning and cobalt modification on the NH3 adsorption behavior on the MnxOy/Ni (1 1 1) surface: A DFT-D study

The effects of alkali metal (potassium and sodium) poisoning and cobalt modification on the NH3 adsorption behavior on the MnxOy/Ni (1 1 1) surface were studied using a density functional theory. Alkali metals have strong inhibition on the activity of catalyst because they can cover the Mn sites to block the NH3 adsorption, which can also decrease the activity of the Mn sites on the catalyst surface. In addition, since potassium atom is easier to adsorb on the catalyst surface than sodium atom, the inhibitory effect of potassium is larger than that of sodium. After cobalt modification, the adsorption energies of potassium atom are decreased and activity of Mn sites on the poisoned catalyst surface is recovered. Cobalt can provide a number of strong acid sites for NH3 adsorption, which is favorable to promoting the NOx conversion of Co modified foam nickel supported manganese-based catalyst under alkali metal poisoning conditions. The calculated results are consistent with the experimental results.

Effect of Phosphorus Modification of Zeolites Y and ZSM-5 on the Cracking of Hydrotreated Vacuum Gas Oil and a Vacuum Gas Oil–Sunflower Oil Mixture

The effect of the preliminary impregnation of zeolites HREY and HZSM-5 with ammonium phosphate before introducing them into the composition of dual-zeolite catalysts has been studied. It has been found that the modification leads to a change in the main textural characteristics of the zeolites. Both the specific surface area and the meso- and micropore volume of the zeolites decrease. The total acidity of HREY and HZSM-5 and the number of strong acid sites in them also decrease. Tests on the conversion of hydrotreated vacuum gas oil and a vacuum gas oil–sunflower oil mixture under catalytic cracking conditions have shown that the modification of the zeolites leads to an increase in the total yield of the propane–propylene and butane–butylene fractions with a high olefin content in them, even with a decrease in the feedstock conversion.

Tungsten-titanium mixed oxide bronzes: Synthesis, characterization and catalytic behavior in methanol transformation

Tungsten oxide bronze-based materials show extremely adaptive structural and compositional features that make them suitable for functional properties modulation. Herein we report the preparation of a series of Ti-containing tungsten oxide catalysts presenting a hexagonal tungsten bronze-type structure. The insertion of Ti4+ within the structure (likely in the octahedral framework of the hexagonal tungsten bronze) leads to an increase in the number of strong acid sites, and the disappearance of W5+ surface species found in the undoped tungsten oxide. With the aim of studying the acid-redox properties of the titled catalysts, the catalytic transformation of methanol has been carried out in the presence and the absence of O2 in the feed. Both catalytic activity and the acid-redox properties of these catalysts are highly dependent on catalyst composition and reaction conditions applied (i.e. in the presence or in the absence O2 in the feed). Aerobic experiments show the depletion of the redox functionality (i.e. no formaldehyde detected in the products) when Ti4+ is incorporated in the framework (i.e. 100% selectivity to dimethyl ether). On the other hand, all the catalysts show the loss of the redox function and a decrease in the catalytic activity when anaerobic conditions are used. In the absence of oxygen, the catalysts are still active in the dehydration of methanol to dimethyl ether, i.e. they maintain their acid functionality even when oxygen is not present in the feed. The results are discussed in terms of the available surface active sites present in each case.

Effect of Mg/Al2O3 and Calcination Temperature on the Catalytic Decomposition of HFC-134a

This paper evaluated the effect of calcination temperature and the use of Mg/Al2O3 on the decomposition of HFC-134a. Two commercialized catalysts, Al2O3 and Mg/Al2O3, were calcined at two different temperatures (500 and 650 °C) and their physicochemical characteristics were examined by X-ray diffraction, Brunauer–Emmett–Teller analysis, and the temperature-programed desorption of ammonia and carbon dioxide analysis. The results show that, in comparison to Al2O3, 5% Mg/Al2O3 exhibited a larger Brunauer–Emmett–Teller surface area and higher acidity. The relative amount of strong acid sites of the catalysts decreased with increasing calcination temperature. Although a more than 90% decomposition rate of HFC-134a was achieved over all catalysts during the sequential decomposition test of HFC-134a using a vertical plug flow reactor connected directly to a gas chromatography/mass spectrometry system, the lifetime of the catalyst differed according to the catalyst type. Compared to Al2O3, Mg/Al2O3 revealed a longer lifetime and less coke formation due to the increased Brunauer–Emmett–Teller surface area and weak Lewis acid sites and basic sites arising from Mg impregnation. Higher temperature calcination extended the catalyst lifetime with the formation of less coke due to the smaller number of strong acid sites, which can lead to severe coke formation. A valuable by-product, trifluoroethylene, was formed as a result of the decomposition. Based on the experimental results, a reaction is proposed which reasonably explains the decomposition reaction.

Impact of acidity in ZrO2-TiO2-Al2O3 composite oxides on the catalytic activity and coking behaviors during n-decane cracking

Mn, Fe, Mo or W as a promotor was introduced into ZrO2-TiO2-Al2O3 (ZTA) composite oxides by impregnation method, in order to examine the influence of these promotors on catalytic activity and coking behaviors during n-decane cracking. The as-prepared catalysts were characterized by several different techniques: N2 adsorption –desorption, X-ray diffraction (XRD), temperature programmed desorption of ammonia (NH3-TPD), in situ infrared spectroscopy (IR) and X-ray photoelectron spectroscopy (XPS). The characterization results revealed that the incorporation of these metal oxides enhanced the total amount of acid sites and gave rise to the formation of much stronger acid sites, especially Mo. Moreover, Mo-promoted ZTA catalyst was found to be the most efficient one for n-decane cracking (conversion 88.4%, heat sink 3.79 MJ/kg at 750 °C) due to an optimum balance between the number of strong acid sites (0.24 mmol NH3/g) and the total amount of acid sites (0.59 mmol NH3/g). Besides, the temperature programmed oxidation (TPO) results showed that Mo-modified ZTA catalyst exhibited more desirable anti-coke capacity in comparison to the others owing to its appropriate acid property.

Propane catalytic cracking on pretreated La-ZSM-5 zeolite during calcination for light olefins production

The purpose of this study was to increase light olefins yield and selectivity in catalytic cracking of propane. Pretreatment of ZSM-5 zeolite was performed during calcination. First, lanthanum was loaded on the catalyst by wet impregnation method and then the effect of parameters, such as temperature (400–800 °C), time (120–480 min) and type of stream, on La-ZSM-5 zeolite was examined during calcination using central composite design (CCD) method. Based on the proposed models, the optimized condition for maximizing selectivity of light olefins for air stream was 680 °C and 310 min and for the nitrogen stream was 735 °C and 173 min that under these conditions, selectivity amount increased 24% for nitrogen stream and 19% for air stream as compared with H-ZSM-5 catalyst. The synthesized catalysts were characterized by X-ray diffraction (XRD) and temperature-programmed desorption (TPD) techniques. According to the results of NH3-TPD, as the temperature increased, the number of strong acid sites (specially Bronsted acid sites) reduced and resulted in increased production of light olefins as well as catalyst stability. Accordingly, stability of the samples calcined with nitrogen stream was higher than the samples calcined with the air stream.