Liquid phase synthesis of ethyl-tert-butyl ether: The relationship between acid, adsorption and catalytic properties of zeolite catalysts

Vlasenko, N. A.; Kochkin, Yu. N.; Puziy, Alexander M.

doi:10.1016/j.molcata.2006.03.041

Cited by 25 publications

(18 citation statements)

References 21 publications

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“…We have shown previously [12] that the presence of weak acid centers are necessary for the synthesis of ethyl tert-butyl ether (ETBE) from ethanol and isobutene. A correlation was observed between the rate of formation of ETBE and the concentration of acid centers characterized by a mean value for the heat of absorption of NH 3~7 0-75 kJ/mol.…”

Section: Resultsmentioning

confidence: 99%

Changes in the acidic properties of the zeolite H-ZSM-11 under the influence of hydrogen and water

Vlasenko

Kochkin

2006

Theor Exp Chem

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The nature of the effect of hydrogen and water on the spectrum of acidity of H-ZSM-11 zeolite has been studied. An explanation of the observed changes is proposed and a prognosis has been made on the relative effect of transformation of the functional groups of the surface on the catalytic properties of H-ZSM-11 in various reactions of acid type.Thanks to their characteristic physico-chemical properties zeolites are widely used in a variety of acid-base catalytic processes such as hydration and dehydration, esterification, cracking, hydrogenation, etc. Presentations on the nature of the active centers of the catalyst, their concentration, and their distribution with respect to strength are extremely important.The acid properties of zeolites are determined by two basic types of centers: protonic (Brönsted) and aprotonic (Lewis). Brönsted acidity is determined by the presence of different types of hydroxyl groups -structural or bridging hydroxyl groups, OH groups found on the outer surfaces of zeolite crystals, OH groups localized on polyvalent cations and OH groups localized on nonstructural particles of aluminum [1]. As a rule the catalytic properties of zeolites are connected to siloxy bridged hydroxyl groups. However in recent times activity has been noted of weakly acidic silanol OH groups in a series of catalytic reactions which occur under mild conditions [2].The distribution of acid centers by type, concentration, and strength forms a spectrum of acidity which may change under the influence of various factors. This is especially important for zeolite catalysts working at high temperatures and subjected to the effects of components of the reaction media. It is well known that the effect of high temperatures leads to a decrease in the Brönsted acidity and an increase Lewis acidity [3]. The presence of water molecules contained in the starting materials or evolved during the process reactions can facilitate the conversion Lewis acid centers of the zeolite into Brönsted centers which leads to a change in catalytic atcivity in a number of cases. Data show that hydrogen in the atmosphere over the zeolite surface may form protonic acid centers [4].Thus in the process of catalyst formation and the subsequent effects of the reaction media the spectra of acidity of zeolites may undergo important changes, understanding the nature of which may permit the favorable formation of functional characteristics of the surface of zeolites for the creation of effective catalysts for various processes proceeding by an acid-base mechanism.The objective of the present was to investigate the character of changes in the spectrum of acidity of the zeolite H-ZSM-11 under the influence of hydrogen and water vapor. 2660040-5760/06/4204-0266

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Section: Resultsmentioning

confidence: 99%

Changes in the acidic properties of the zeolite H-ZSM-11 under the influence of hydrogen and water

Vlasenko

Kochkin

2006

Theor Exp Chem

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“…Acid and base properties of the samples were defined using the Quasi‐Equilibrium ThermoDesorption (QE‐TD) method, using ammonia and carbon dioxide as probe molecules. Experiments were carried out in a thermogravimetric apparatus with a quartz spring balance of the McBain type, measuring the amount of NH 3 (acidity) or CO 2 (basicity) sorption in quasi‐equilibrium mode (stepwise ammonia or carbon dioxide thermodesorption keeping an adsorption equilibrium state at each step).…”

Section: Methodsmentioning

confidence: 99%

“…Ammonia and carbon dioxide adsorption heats were calculated with the CONTIN method, adapted by Vlasenko et al for processing QE‐TD experiment data.…”

Section: Methodsmentioning

confidence: 99%

Methanol carboxylation over zirconium dioxide: Effect of catalyst phase composition on its acid‐base spectrum and direction of catalytic transformations

et al. 2016

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The effect of ZrO 2 calcination temperature on its structure and acid-base characteristics was investigated to elucidate their relation to catalytic behaviour in methanol carboxylation. Varying the calcination temperature causes changes in ZrO 2 phase composition and acid-base characteristics. The base properties of ZrO 2 play a prominent role in dimethyl carbonate synthesis. Strong base sites (E CO2 > 78 kJ/mol) are needed to activate СО 2 . Tetragonal modification of zirconium dioxide has a higher basicity than the monoclinic. Thus, the greater the contribution of t-ZrO 2 in the catalyst, the greater its ability to activate СО 2 and therefore result in higher catalytic activity for methanol carboxylation. DMC selectivity was determined by the ratio of catalyst base site to acid site concentration.

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“…The concentration of the acid centers was determined from the sorption of NH 3 in a quasi-equilibrium regime (the QE-TD ammonia method) [15]. The samples were first heated under vacuum (0.133 Pa) to constant weight at a temperature determined by the thermal stability of the organic phase (150°C).…”

Section: Methodsmentioning

confidence: 99%

Catalytic Properties of Various Types of Sulfonated Cation-Exchange Resins in the Synthesis of Isopropyl Tert-Butyl Ether

et al. 2015

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The acidic and catalytic characteristics of various types of sulfonated cation-exchange resins, differing in the location of the active phase, in the synthesis of isopropyl tert-butyl ether (IPTBE) were studied. It was established that a sulfonated cation-exchange resin on a wide-pore silica gel support has the highest selectivity with respect to IPTBE (100%). It was shown that mineral-organic sulfonated cation-exchange resins have higher activity than bulk sulfonated cation-exchange resins due to the accessibility of their acid centers for the reagents.Key words: isopropyl tert-butyl ether, sulfonated cation-exchange resins, acidity.tert-Butyl ethers, such as methyl tert-butyl ether (MTBE) and ethyl tert-butyl ether (ETBE), are widely used as high-octane additives in reformulated gasolines. Isopropyl tert-butyl ether (IPTBE) has recently been examined as a prospective oxygen-containing additive for motor fuels [1][2][3][4][5]. In comparison with other tertiary ethers IPTBE has a higher octane number and is also less environmentally hazardous since it is characterized by lower vapor pressure and poor solubility in water [6].Isopropyl tert-butyl ether is obtained in the reaction of isopropanol with isobutylene in the presence of acidic catalysts at 40-80°C and at 1.5 MPa according to the following reaction [7-12]:(CH 3 ) 2 CHOH + (CH 3 )C=CH 2 « (CH 3 ) 3 COCH(CH 3 ).The process is characterized by low selectivity on account of the occurrence of side processes leading to the formation of diisobutylene, tert-butanol, diisopropyl and isopropyl sec-butyl ethers. In the presence of Bayer K2631 sulfonated cation exchanger at 30-80°C and 1.6 MPa the side products are diisobutylene and tert-butanol over the whole temperature range, while diisopropyl ether is formed at elevated temperatures (above 100°C) [10].Organic and mineral acid catalysts are used in the synthesis of alkyl tert-butyl ethers. In particular, in the synthesis of IPTBE at 1.6 MPa and 70-90°C the sulfonated cation exchangers Amberlyst 15, Amberlyst 35, CT275, and zeolites H-ZSM-5 (Z28, Z55, Z120) have practically identical selectivity with respect to IPTBE, but the zeolites have lower activity than the sulfonated cation-exchange resins [11]. The catalytic characteristics of the various types of sulfonated cation exchangers (gel-type and macroreticular) are determined by the sulfo groups [-SO 3 H], located both on the surface of the catalyst and in its volume. A gel-type sulfonated cation exchanger does not have a porous structure, and most of its acid centers are only 0040-5760/15/5102-0127

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Liquid phase synthesis of ethyl-tert-butyl ether: The relationship between acid, adsorption and catalytic properties of zeolite catalysts

Cited by 25 publications

References 21 publications

Changes in the acidic properties of the zeolite H-ZSM-11 under the influence of hydrogen and water

Changes in the acidic properties of the zeolite H-ZSM-11 under the influence of hydrogen and water

Methanol carboxylation over zirconium dioxide: Effect of catalyst phase composition on its acid‐base spectrum and direction of catalytic transformations

Catalytic Properties of Various Types of Sulfonated Cation-Exchange Resins in the Synthesis of Isopropyl Tert-Butyl Ether

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