Insight into the active site nature of zeolite H-BEA for liquid phase etherification of isobutylene with ethanol

Vlasenko, N. A.; Kochkin, Yuri N.; Tel’biz, G. M.; Швец, А. В.; Strizhak, P. E.

doi:10.1039/c9ra07721a

Cited by 17 publications

(10 citation statements)

References 114 publications

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“…Following this argument, the share of Brønsted acid sites is assumed to increase with the weight percentage of HPA. As NH 3 -TPD is unable to distinguish between different types of acid sites and specific sensor molecule IR techniques (e.g., pyridine-IR 52 ) are unsuited for HPAs due to their decomposition under the needed conditions, no quantification and determination of the actual acid sites were performed.…”

Section: Resultsmentioning

confidence: 99%

From CO₂ to DME: Enhancement through Heteropoly Acids from a Catalyst Screening and Stability Study

et al. 2023

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The direct synthesis of dimethyl ether (DME) via CO2 hydrogenation in a single step was studied using an improved class of bifunctional catalysts in a fixed bed reactor (T R: 210–270 °C; 40 bar; gas hourly space velocity (GHSV) 19,800 NL kgcat –1 h–1; ratio CO2/H2/N2 3:9:2). The competitive bifunctional catalysts tested in here consist of a surface-basic copper/zinc oxide/zirconia (CZZ) methanol-producing part and a variable surface-acidic methanol dehydration part and were tested in overall 45 combinations. As dehydration catalysts, zeolites (ferrierite and β-zeolite), alumina, or zirconia were tested alone as well as with a coating of Keggin-type heteropoly acids (HPAs), i.e., silicotungstic or phosphotungstic acid. Two different mixing methods to generate bifunctional catalysts were tested: (i) a single-grain method with intensive intra-particular contact between CZZ and the dehydration catalyst generated by mixing in an agate mortar and (ii) a dual-grain approach relying on physical mixing with low contact. The influence of the catalyst mixing method and HPA loading on catalyst activity and stability was investigated. From these results, a selection of best-performing bifunctional catalysts was investigated in extended measurements (time on stream: 160 h/7 days, T R: 250 and 270 °C; 40 bar; GHSV 19,800 NL kgcat –1 h–1; ratio CO2/H2/N2 3:9:2). Silicotungstic acid-coated bifunctional catalysts showed the highest resilience toward deactivation caused by single-grain preparation and during catalysis. Overall, HPA-coated catalysts showed higher activity and resilience toward deactivation than uncoated counterparts. Dual-grain preparation showed superior performance over single grain. Furthermore, silicotungstic acid coatings with 1 KU nm–2 (Keggin unit per surface area of carrier) on Al2O3 and ZrO2 as carrier materials showed competitive high activity and stability in extended 7-day measurements compared to pure CZZ. Therefore, HPA coating is found to be a well-suited addition to the CO2-to-DME catalyst toolbox.

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Section: Resultsmentioning

confidence: 99%

From CO₂ to DME: Enhancement through Heteropoly Acids from a Catalyst Screening and Stability Study

et al. 2023

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“…More recently, Vlansenko et al [89,90] explored the behavior of beta zeolites with different Si/Al ratio for the ETBE synthesis carried out in a continuous flow reactor, in both liquid and gas phase. A good correlation between the rate of ETBE synthesis and the concentration of weak acid sites has been observed.…”

Section: Etherification Reaction: Mtbe and Etbe Synthesismentioning

confidence: 99%

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

Hulea¹

2022

Comptes Rendus. Chimie

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Isobutene (IB), the most reactive molecule in the C4 raffinate, is a raw material of great industrial significance. It is extensively used in the manufacturing process of rubber, fuel additives, fine chemicals, agricultural chemicals, plastics and antioxidants. Heterogeneous catalysts and particularly zeolites are playing a major role in these applications. The aim of this review is to examine the relevant processes involving IB as reagent and zeolites as acid catalysts. The following reactions are successively covered: Prins condensation, IB dimerization, IB-methanol/ethanol etherification, IB-glycerol etherification, IB amination, and phenol tert-butylation. While reasonably comprehensive and broad, the present survey is not necessarily exhaustive. The mechanistic aspects of the titled reactions, the role of zeolite catalysts and their topology/active sites on the product selectivity are mainly explored.

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“…where A stands for the actual IR absorbance being measured, and A M is the maximum absorbance, which corresponds to θ = 1. It should thus be clear that after determining θ (or relative IR absorbance) as a function of T and p over a temperature range, equations (4) or (5) give direct access to the values of H 0 and S 0 that characterize the gas adsorption process. Worth of notice is that series of VTIR spectra should always be recorded over a sufficiently wide temperature range; otherwise spurious correlations between H 0 and S 0 can occur [21,22].…”

Section: Basesmentioning

confidence: 99%

“…By virtue of their [Si(OH)Al] units (see below) protonic zeolites show a distinctive Brønsted acidity which endows them with widespread application as solid acid catalysts in a wide range of chemical processes spanning the fields of selective reforming of hydrocarbons, methanol to olefin conversion, biomass upgrading and the manufacture of fine chemicals, to quote only a few examples [1][2][3][4][5].…”

Section: Introductionmentioning

confidence: 99%

Ranking the Bronsted Acid Strength of Protonic Zeolites with VTIR Spectroscopy --- An Overview of Current Research

2022

Optics and Spectroscopy

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Many industrial applications of protonic zeolites as solid-acid heterogeneous catalysts rely on the strength or their Br nsted acidity, which (together with zeolite topology) affects both, catalytic activity and selectivity. Therefore, the convenience to have an accurate (and simple) experimental technique for measuring Br nsted acid strength. The enthalpy change, Delta H0, corresponding to the hydrogen bonding interaction of a weak base (such as CO or dinitrogen) with their Br nsted acid [Si(OH)Al] hydroxyl groups should directly correlate with the zeolite acid strength. Nevertheless, because of simplicity, the bathochromic shift of the O-H stretching frequency, Deltaν(OH), is usually measured by IR spectroscopy at a low temperature, and correlated with acid strength, for ranking zeolite acidity. Herein the use of variable-temperature IR (VTIR) spectroscopy to determine simultaneously Delta H0 and Deltaν(OH) is demonstrated; followed by an abridged overview showing that direct correlation between Deltaν(OH) and Br.nsted acid strength can be misleading when ranking zeolite acidity. Keywords: VTIR spectroscopy, br nsted acidity, H-zeolites

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Insight into the active site nature of zeolite H-BEA for liquid phase etherification of isobutylene with ethanol

Abstract: The active sites of H-BEA zeolites for ETBE synthesis are the weak Brønsted acid sites representing internal silanol groups.

Cited by 17 publications

References 114 publications

From CO₂ to DME: Enhancement through Heteropoly Acids from a Catalyst Screening and Stability Study

From CO₂ to DME: Enhancement through Heteropoly Acids from a Catalyst Screening and Stability Study

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

Ranking the Bronsted Acid Strength of Protonic Zeolites with VTIR Spectroscopy --- An Overview of Current Research

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Insight into the active site nature of zeolite H-BEA for liquid phase etherification of isobutylene with ethanol

Abstract: The active sites of H-BEA zeolites for ETBE synthesis are the weak Brønsted acid sites representing internal silanol groups.

Cited by 17 publications

References 114 publications

From CO2 to DME: Enhancement through Heteropoly Acids from a Catalyst Screening and Stability Study

From CO2 to DME: Enhancement through Heteropoly Acids from a Catalyst Screening and Stability Study

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

Ranking the Bronsted Acid Strength of Protonic Zeolites with VTIR Spectroscopy --- An Overview of Current Research

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From CO₂ to DME: Enhancement through Heteropoly Acids from a Catalyst Screening and Stability Study

From CO₂ to DME: Enhancement through Heteropoly Acids from a Catalyst Screening and Stability Study