Isobutane Conversion Research Articles

Deactivation mechanism of acetone to isobutene conversion over Y/Beta catalyst

Deactivation mechanism of acetone to isobutene conversion over Y/Beta catalyst

Shape selection of alkane hydroisomerization over one-dimensional zeolite supported Pt catalyst: Pt/ZSM-48 versus Pt/ZSM-22

Hydroisomerization of long-chain n-alkanes plays a vital role in petrochemical and coal chemical industries, because it can produce high-quality hydrocarbon fuels and lubricant base oils. ZSM-48 (0.56 × 0.53 nm) and ZSM-22 (0.57 nm × 0.46 nm) are characteristic of one-dimensional 10-member ring zeolites suitable for n-alkanes hydroisomerization reaction. Here, the effect of the structure difference between ZSM-48 and ZSM-22 zeolites on hydroisomerization is titrated by the isobutane and n-dodecane. The product distribution of hydroisomerization of isobutane to n-butane shows the reaction pathway on Pt/ZSM-48 and Pt/ZSM-22, in which the monomolecular hydroisomerization of isobutane is involved within the active sites in zeolite channels, while the polymerization-cracking bimolecular reaction occurs on the pore-mouth of zeolite. Pt/ZSM-48 zeolite, possessing larger channel and aperture size than those of Pt/ZSM-22, is more conducive to the diffusion of butane molecules and bimolecular polymerization. Therefore, the isobutane conversion (14 %) on Pt/ZSM-48 produces less C1+C2 (1.7 wt% vs. 3.4 wt%) and more C3+C5+C8 (19.2 wt% vs. 16.9 wt%). For the hydroisomerization of n-dodecane, the iso-dodecane selectivity of Pt/ZSM-48 (43.3 wt%) is significantly higher than that of Pt/ZSM-22 (12.4 wt%) at the similar n-C12 conversion (40 %). Compare with the isomers of Pt/ZSM-22, the mono-branched isomers with methyl near the middle of the chains and multi-branched isomers are more easily formed on Pt/ZSM-48, which is conducive to the “key-lock” catalysis mechanism. The larger pore size of ZSM-48 is conducive to n-C12 insertion into zeolite pores, methyl migration and isomer diffusion, and its adjacent pores are more compatible with double-branched isomers. In addition, a high selectivity of C4∼C5 alkanes (53.2 wt%) on Pt/ZSM-22 and a high selectivity of C6∼C9 alkanes (44.7 wt%) on Pt/ZSM-48 show obvious difference in cracking product distribution, implying different position of methyl groups in i-C12 isomers on Pt/ZSM-22 and Pt/ZSM-48 samples, respectively. The present comparison between Pt/ZSM-48 and Pt/ZSM-22 benefits the selection and development of one-dimensional zeolitesupported metal catalyst in a wide range of hydro-processing reactions.

Oxygen carrier prepared by solvent-free grinding and biomass based oxygenates for chemical looping oxidative dehydrogenation of isobutane

The chemical looping oxidative dehydrogenation of isobutane is an effective and novel strategy for producing isobutene. It is extremely necessary but challenging to design excellent oxygen carriers for this strategy. Here, a solvent-free grinding approach is presented to prepare ZnMo0.45V0.55Ox oxygen carrier with tailorable oxygen vacancy content via biomass based oxygenate as carbothermal reductive agent. As a result, ZnMo0.45V0.55Ox-0.3 vitamin C oxygen carrier demonstrates a much higher isobutane conversion of 17.61 % and isobutene selectivity of 82.55 %, whereas it is 7.99 % of isobutane conversion and 22.66 % of isobutene selectivity for ZnMo0.45V0.55Ox without vitamin C addition. The performance for the ZnMo0.45V0.55Ox-0.3 vitamin C is closely related to the surface area and the metal-oxygen bond strength. Large surface area can provide more accessible active sites, which can facilitate the isobutane's diffusion, adsorption and activation. High oxygen vacancy content results in weak metal-oxygen bond strength, which leads to high mobility of lattice oxygen.

Isobutane Dehydrogenation on CrO<sub><i>x</i></sub>/Al<sub>2</sub>O<sub>3</sub> Nanoparticles, Prepared by Laser Synthesis in Various Gases

The catalytic properties of nCrOx/Al2O3 nanoparticles (n = 4.8 ± 0.05 wt %) tested in the isobutane dehydrogenation reaction which were obtained by laser synthesis in various gases are studied in detail for the first time. Laser synthesis of 4.8% CrOx/Al2O3 nanopowders was carried out by the vaporization of 5.0% Cr : α-Al2O3 ceramic targets using cw CO2 laser irradiation in an inert, oxidizing and reducing gaseous environment in a vaporization chamber: in an Ar medium; Ar with addition of O2, H2 and CH4 at concentrations of 20, 30, and 13 vol. %, respectively. The role of the gas medium during the synthesis of 4.8% CrOx/Al2O3 nanopowders in their catalytic properties (activity, selectivity, conversion, and stability in the reaction) was determined. A comprehensive study of the physicochemical properties of the obtained nanocatalysts was carried out using XRD, TEM, UV-Vis DRS, and Raman techniques. According to XRD data the phase composition is predominantly consists of γ-Al2O3 with the beginning of the transition to δ-Al2O3. According to the TEM results, the shape of nanoparticles is spherically symmetric with an average particle size dm = 15 nm. Using the UV-Vis DRS method, charge states of Crq+ (q = 3, 6) in different coordination (Cr6+(Td) and Cr3+(Oh)) and its different ratios depending on the gas atmosphere used in the process of laser vaporization were revealed in the obtained 4.8% CrOx/Al2O3 nanopowders. Nanosized 4.8% CrOx/Al2O3 catalyst prepared in an atmosphere (Ar + H2) demonstrated the highest values of isobutane conversion (39%) and isobutylene selectivity (90.7%); the lowest corresponding values of conversion (18.8%) and selectivity (85.6%) were typical for the sample obtained in the atmosphere (Ar + CH4). Thus, the most active and selective in the isobutane dehydrogenation reaction was the 4.8% CrOx/Al2O3 nanocatalyst synthesized in the (Ar + H2) medium, and the presence of methane during vaporization led to the initial surface carbonization, which prevents the access of reacting molecules to it.

Theoretical investigation of catalytic n-butane isomerization over H-SSZ-13

Hybrid density functional theory calculations are used to investigate different mechanisms of the isomerization of n-butane to isobutane via intermediate formation of olefins. The monomolecular mechanism for isomerization of butene and isobutene is found to be prevalent, with a Gibbs free energy barrier of 155 kJ/mol at 400°C, compared to the bimolecular mechanism (190 kJ/mol) due to less favorable entropy for the latter. Hydrogen transfer reactions that convert olefins into alkanes (and vice versa) are also included in the investigations, and show a free energy barrier of 203 kJ/mol for conversion of isobutene to isobutane. Additionally, a methyl transfer mechanism is discussed as a possible pathway for formation of C3 and C5 side products, in comparison to the bimolecular mechanism; the highest barrier of the initial methyl transfer is calculated to be 227 kJ/mol. We discuss the influence of entropy and anharmonicity on all mechanisms, stating that through the uncertainties in computational methods when calculating these systems, the calculated reaction barriers are likely to be overestimated here.

Isobutene isomerization via metal-organic coordination polymer catalyst

One-dimensional, two-dimensional and three-dimensional Ni-containing metal-organic coordination polymer (1D-Ni, 2D-Ni and 3D-Ni MOCP) catalysts were solvothermally synthesized and used for isomerization of isobutene. These catalysts showed the same conversion of isobutene and selectivity for 2-butene as homogeneous catalysts. At the same time, 1D-Ni catalyst evacuated at 100 °C revealed the conversion of isobutene and selectivity to 2-butene were up to 89.2% and 100.0%, respectively. Moreover, the results demonstrated that the conversion of isobutene was different depending on metal coordination mode, dimension of coordination polymer, and the reaction pressure. In addition, The MOCP catalysts were relatively environmentally friendly, and easily recovered and recycled. Finally, the mechanism of metal hydride addition elimination was proposed.

In-situ constructed ultrathin hydrotalcite derivative supported PtIn catalyst for isobutane direct dehydrogenation

The stable and ultrathin hydrotalcite nanosheets with thickness of ca. 1.0 nm have been built on the surface of Al2O3 by sharing Al element and using layer growth inhibitor formamide. Based on the topological transformation characteristics of hydrotalcite and the structural memory effect of calcined product, the supported PtIn bimetallic catalyst was achieved by stepwise incipient wetness impregnation method followed by calcination and reduction, and evaluated in isobutane direct dehydrogenation (IDH) to isobutene. The derived ultrathin bimetallic catalyst possesses excellent IDH activity under extreme conditions, in which the isobutane conversion and isobutene selectivity can remain above 63% and 92% respectively, and the turnover frequency is as high as 13.45 s−1. The excellent activity can be attributed to the formation of ultrathin hydrotalcite precursor, which can greatly enhance the specific surface area, interaction among metal components, surface acidity of weak- and medium-acid sites and surface In3+/In0 ratio, and further effectively inhibit carbon deposition and improve dispersion and stability of active Pt species in the corresponding derivative.

Molybdenum-based oxygen carrier for chemical looping oxidative dehydrogenation of isobutane

Compared with steam cracking, oxidative dehydrogenation of isobutane to produce isobutene has advantages, but its application is limited by capital intensive air separation needed to provide O2. A chemical looping oxidative dehydrogenation strategy for isobutane to isobutene is proposed to tackle this problem, in which the oxygen carrier provides lattice oxygen. The synthesis of the oxygen carrier from the perspective of electronic structure and metal–oxygen bond strength is highly desirable to enhance the performance of the chemical looping oxidative dehydrogenation of isobutane. Herein, the electronic structure and metal–oxygen bond strength of a Mo-based oxygen carrier are regulated by doping Zn, V and Mg. The results show that Mg0.2Zn0.8Mo0.45V0.55Ox with 35% isobutane conversion and 82% isobutene selectivity is superior to MoO3, ZnMoOx and ZnMo0.45V0.55Ox. It indicates that the electronic structure and metal–oxygen bond strength via doping Zn, V and Mg are responsible for the promoted performance of Mg0.2Zn0.8Mo0.45V0.55Ox. This study provides important insights for the oxygen carrier design and optimization through regulating electronic structure and metal–oxygen bond strength.

Selective peroxidation of isobutane with molecular oxygen over molybdenum oxide catalyst for direct synthesis of di-tert-butyl peroxide

The direct conversion of isobutane to high value-added chemicals is important for utilization of C4 hydrocarbon resources. This work proposed a novel route of isobutane peroxidation with molecular oxygen for green synthesis of di-tert-butyl peroxide (DTBP), widely used as polymerization initiating/crosslinking agent and diesel additive. For the first time, MoO3 was demonstrated as selective catalyst for isobutane peroxidation to DTBP. The results indicated that, the reactivity depended on the oxygen adsorption capacity of MoO3 catalyst, and the selectivity to DTBP was determined by the amount of surface Mo = O sites. During the reaction, tert-butyl hydroperoxide (TBHP) was generated from isobutane peroxidation as intermediate product, and subsequently converted to DTBP on Mo = O active sites. Under the optimized conditions, a high oxygen conversion (>95%) and stable product selectivities (DTBP ∼ 20 wt%, TBHP ∼ 13 wt%) were obtained during continuous catalyst re-usage runs. This work provides an environmental route for both C4 hydrocarbon utilization and DTBP production.

Supported Metal Sulfate Catalysts FexZny/SiO2 for Selective Dimerization of Isobutene in Mixed C4 to Isooctenes

AbstractIsobutene dimerization is an important route to properly utilize mixed C4 and further produce isooctane with a high‐octane number to replace MTBE in gasoline. A highly selective catalyst, which is effective for isobutene dimerization but ineffective for other olefins in the C4 mixture, is necessary for industrial implementation. In this work, a series of supported metal sulfate catalysts FexZny/SiO2 were prepared and characterized by XRD, SEM, N2 physical adsorption‐desorption, NH3‐TPD, Py‐FTIR, and XPS. Fe0.2Zn1.8/SiO2 can achieve isobutene conversion up to 89 % with 0 % conversion of n‐butene, and the selectivity of isooctenes (C8=) product is 57 % (10 h on stream). Furthermore, isobutene conversion can sustain above 80 % after 50 h. It is found that these supported catalysts contain Zn2+, Zn+, Fe3+, and Fe2+ species, and there is a synergetic effect between Zn2+ and Fe2+. Zn2+ is beneficial to improve the conversion of isobutene, and Fe2+ facilitates the formation of C8=, resulting in a high C8= yield.

Optimizing lattice oxygen mobility and acidity of heteropoly acid catalysts for oxidation of isobutane to methacrylic acid

In this paper, a series of heteropoly acids, (Cs2.2Cu0.26V0.38)xPMo12O40 (x = 1.3, 1.1, 1.0, 0.88), are prepared, characterized and examined as the catalysts for the oxidation of isobutane to MAA. Under the employed reaction condition, Cs2.23Cu0.26V0.38PMo12O40 exhibits an isobutane conversion of 20% and a MAA selectivity of 51% at 335 °C, giving a MAA yield of 0.68 mmolMAA·h−1·gcatalyst−1. Lattice oxygen mobility and acidity of (Cs2.2Cu0.26V0.38)xPMo12O40 catalysts play key roles. A fast migration rate and a moderate release rate of lattice oxygen are beneficial to the selective oxidation of isobutane to MAA. Cs2.2Cu0.26V0.38PMo12O40 exhibits strong acid sites facilitating MAA desorption and surface sites strongly binding MAA, causing MAA polymerization which blocks the active sites and decreases the long-term catalytic activity. These results demonstrate that the optimization of lattice oxygen mobility and surface acidity is an effective strategy to fabricate efficient heteropoly acid catalysts for the oxidation of isobutane to MAA.

Thermodynamic Study of One-step Production from Isobutene to Methyl Methacrylate

Methyl methacrylate (MMA) has emerged as an essential industrial monomer. However, the toxic by-production and shortage supply of MMA in the global market has gained great attention. Herein, a one-step synthesis to produce MMA from isobutene via a direct oxidative esterification process has been demonstrated to curb the aforementioned downsides. Thermodynamic analysis via Gibbs free energy minimization method proved the feasibility of this route via the equilibrium constant. Despite tert-butanol and isobutane showed higher equilibrium constant than isobutene, they should be avoided. Isobutane is highly flammable while the precursor of tert-butanol is exorbitant. Thus, isobutene was selected for the equilibrium compositions screening. Isobutene conversion was 90% and 15% MMA yield at 700 °C and IBN: O2: MeOH ratio with 1:7:1. This route is mainly limited by the generation of side reactions from the reaction of CH3OH and O2. By varying the feedstock ratio at 1:2:1, the MMA yield increased to ~25%. Copyright © 2022 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Zeolite-based catalysis for isobutene conversion into chemicals and fuel additives. A review

Zeolite-based catalysis for isobutene conversion into chemicals and fuel additives. A review

Alkali metal halide-coated perovskite redox catalysts for anaerobic oxidative dehydrogenation of n-butane.

Oxidative dehydrogenation (ODH) of n-butane has the potential to efficiently produce butadiene without equilibrium limitation or coke formation. Despite extensive research efforts, single-pass butadiene yields are limited to <23% in conventional catalytic ODH with gaseous O2. This article reports molten LiBr as an effective promoter to modify a redox-active perovskite oxide, i.e., La0.8Sr0.2FeO3 (LSF), for chemical looping–oxidative dehydrogenation of n-butane (CL-ODHB). Under the working state, the redox catalyst is composed of a molten LiBr layer covering the solid LSF substrate. Characterizations and ab initio molecular dynamics (AIMD) simulations indicate that peroxide species formed on LSF react with molten LiBr to form active atomic Br, which act as reaction intermediates for C─H bond activation. Meanwhile, molten LiBr layer inhibits unselective CO2 formation, leading to 42.5% butadiene yield. The redox catalyst design strategy can be extended to CL-ODH of other light alkanes such as iso-butane conversion to iso-butylene, providing a generalized approach for olefin production.

Catalytic selective oxidation of isobutane in a decoupled redox-process

The catalytic selective oxidation of isobutane to methacrolein (MAC) and methacrylic acid (MAA) is known to proceed via a Mars-Van Krevelen mechanism. When the reaction is performed in a common reactor with co-feeding of the reactant and oxygen, reactive oxygen species are present on the catalyst surface whereby non-selective oxidation reactions occur. In this work, we studied the possibility to decouple the redox mechanism meaning to separate the reactant oxidation step and the catalyst re-oxidation step for the selective oxidation of isobutane (IBAN) to MAC and MAA. For this purpose, two reactor configurations were employed: a periodic reactor and a two-zone fluidized bed reactor (TZFBR). Whereas the periodic reactor allows the temporal separation of the two steps, the TZFBR enables the spatial separation.A Cs-based Keggin type heteropolycompound was employed as catalyst and characterized before and after reaction by XRD, Raman and XPS to better understand the structural and chemical changes during the periodic operation. The effect of the oxygen/IBAN concentration on the performance was studied. For the periodic reactor it was found that the conversion of isobutane and the formation of products decreased with the consumption of available oxygen species in the catalyst during a period. For the whole periodic tests, low concentration of oxygen injected into the reoxidation part of the cycles led to a high selectivity to the desired products (MAC+MAA).

SEAL PRODUCTS AND THEIR ROLE IN THE PROCESS OF CONVERSION OF ISOBUTENE ON A HIGH SILICA ZEOLITE CATALYST

Conversion of isobutene on a high silica zeolite catalyst in the temperature interval (473-773 K) has been studied. The formation of liquid reaction products is observed at the temperature 473 K, whereas gaseous products form after 523K. Maximum yield of liquid products is observed at the temperature 573 K and makes up 67 %. With increase of contact time the yield of liquid reaction products shifts towards high temperatures. Formation of aromatic hydrocarbons is observed at the reaction temperature higher than 573 K. At the temperature 673 K the main mass of liquid products consists of aromatic hydrocarbons. The activity of H-form of HSZ (HHSZ) in the process of conversion of isobutene in the formation of liquid reaction products occurs only when 6-8% of seal products accumulate on its surface. By the method of ammonia adsorption on the initial and coked catalyst their acidic properties have been studied. It was shown that at the beginning of the process decrease in acidic properties of the catalyst occurs due to accumulation of seal products on it. Key words: catalyst, activity, isobutene, zeolite, seal products, temperature, heterogen, chromatography, spectroscopy.

Synergistic effect of low valence manganese ions in manganese-based catalysts for non-oxidative dehydrogenation of isobutane

A series of manganese-based catalysts supported on γ-Al2O3 with low loading amount of manganese from 0.5% to 2.0% were prepared by incipient impregnating method. All catalysts were tested on non-oxidative dehydrogenation of isobutane at 600 °C. In order to explore physicochemical properties of all catalysts, various characterizations including XRD, H2-TPR, XPS, UV-vis, NH3-TPD and TG were carried out on manganese-based catalysts. The experimental results indicated that MnOx species were highly dispersed on γ-Al2O3 support, and both Mn2+ and Mn3+ ions are main active species for isobutane dehydrogenation. The reduced catalyst 1.5%Mn/γ-Al2O3 exhibited the most optimal dehydrogenation performance among all catalysts, reaching at isobutane conversion of 36% and isobutene selectivity of 79%. The main reasons for the excellent activity and selectivity of 1.5%Mn/γ-Al2O3 were related to the high proportion of low valence manganese ions including Mn2+ and Mn3+ as well as the high concentration of medium strong acid sites and weak strong acid strength.

Investigation of isobutane dehydrogenation on CrOx/Al2O3 catalyst in a membrane reactor

Isobutene is an important raw material for the production of additives that increase the octane number of gasoline and reduce emissions, some polymeric materials and pharmaceuticals. Isobutane dehydrogenation, which is widely used in the production of isobutene, is an equilibrium-limited endothermic reaction. In this study, it was aimed to overcome the equilibrium conversions by using membrane reactor. First, Al2O3 supported chromium-based catalysts were prepared by the impregnation technique. Characterization studies of catalysts were carried out by DR..........-UV–vis, N2 adsorption/desorption, XRD and SEM/EDS analyses. Catalysts (6% Cr by mass) were prepared at three different values of the contact time - 24, 48, 72 h mixing times. The highest amount of monochromate was observed in the catalyst prepared during the mixing time of 48 h. Catalysts containing 6%, 8%, and 10% Cr by mass (mixing time: 48 h) were also synthesized. When the chromium concentration increased above 8%, a decrease in the amount of monochromate was observed. Then, reactions were performed with a catalyst containing 8% by mass of Cr, which was prepared in a mixing time of 48 h with the highest amount of monochromate. The reactions were carried out in a Pd based membrane reactor system with pure isobutane feed. The effect of reactor temperature was investigated at 550 °C and 600 °C (WHSV:0.3h−1). While no significant difference was observed between the conversion values at both reactor temperatures (⁓90%), isobutene selectivity values were higher (⁓85%) at 600 °C. It was observed that the high isobutene selectivity values determined at 600 °C were due to the high endothermic nature of the reaction. The reaction was also carried out by changing the weight hourly space velocity at 600 °C (WHSV:0.5h−1). Although the isobutane conversion values were close to each other (⁓90%), higher isobutene selectivity values (⁓90%) were determined at 0.3h−1. The presence of less hydrogen in the environment decreased the formation of the hydrogenation reaction of isobutane. This situation enhanced an increase in isobutene selectivity values. The shift of the reaction towards the products also increased the selectivity of isobutene. It was observed that although the amount of carbon (3 times more) formed at high retention times caused negative effects such as a decrease in the surface area and closure of the pores, the active monochromate species preserved in the catalyst structure. It was determined that the formed amorphous carbon did not cause the rapid decreases in activity and selectivity. The results of the study showed that the equilibrium limitation could be overcome by removing hydrogen from the reactor medium (equilibrium conversions:73% at 600 °C, 53% at 550 °C). The results of the modeling studies carried out in the membrane reactor were found to be compatible with the experimental results.

Preparation of supported Fe2O3‐Cl/β‐zeolite catalyst and its application in the selective oligomerization reaction of isobutene in mixed C4

AbstractBACKGROUNDIsobutene oligomerization is a very promising reaction, and it has always been a research hotspot in the separation of mixed C4. A supported catalyst is a promising olefin oligomerization catalyst. In the work reported, a supported Fe2O3‐Cl/β‐zeolite molecular sieve catalyst was synthesized by changing the loading amount of various active components, and its catalytic effect on the selective oligomerization of isobutene was studied. The catalyst was characterized using various techniques. The experiments were carried out in a fixed bed reactor, and the effects of Fe loading, temperature and reaction space airspeed were studied.RESULTSThe catalyst has a good catalytic effect on this reaction with the load at 3%, the temperature at 70 °C, the pressure at 1 MPa and the reaction airspeed at 2 h−1.CONCLUSIONSThe conversion of isobutene was above 90%, the selectivity of C8 was around 80% and the loss of n‐butene was very small. © 2022 Society of Chemical Industry (SCI).

WHEN CHOOSING CATALYSTS FOR THE CONVERSION OF ISOBUTYLENE PRINCIPLES OF QUALITY AND QUANTITY

Catalysts play an extremely important role in wildlife and industry. Today it is difficult to describe chemistry and petrochemistry without catalytic processes. Catalytic processes account for 80-85% of oil refining. Therefore, the problem of choosing a catalyst is of interest both from the point of view of quality and quantity. In this paper, the activity of a high silicon zeolite catalyst used in the conversion of isobutene was studied at various temperatures, and it was determined that a sample of the zeolite catalyst during the process initially had no catalytic activity during the conversion of isobutene. The release of liquid products is observed only after the formation of 5-8% of compaction products (PM) on the surface within 25-30 minutes from the beginning. Consequently, modifiers have a positive effect on catalytic activity. In this case, the number and strength of the acid sites of the catalyst changes. The study of isobutene conversion process showed that the formation of liquid products is observed at 150°C. It was shown that in this case in the temperature range 150°C-300°C liquid products of isobutene reaction consist of primarily from aliphatic and at 350°C- 450°C from aromatic hydrocarbons. The process of conversion of hexane-1 on the high-silica zeolite catalyst is studied and it was shown that the decomposition of hexene-1 into ethene and propene is occure at the beginning, at 250°C and then the process takes place in a mixture of the two olefins. It was shown by the using of XRD, TG/DTA methods, that the formed products of seals in the conversion of isobutene and 1-hexene over the high silica zeolite catalyst,is composed of two phases that differ from each other in thermal stability. The obtained liquid products during the conversion of isobutene at 150°C-300°C can be used as high-octane gasoline fractions as motor fuel component. The adsorbed NH3 probe molecules method showed that during the conversion of propene, isobutene and hexene-1, the amount of acid sites of spent catalysts is reduced by 43-50%. In this state, the catalyst exhibits high catalytic activity. Keywords: catalyst, activity, isobutene, zeolite.