Acidic sites in beta zeolites in dependence of the preparation methods

Dimitrova, R.; Gündüz, Gönül; Dimitrov, L.; Tsoncheva, Tanya; Yialmaz, S.; Urquieta‐González, Ernesto A.

doi:10.1016/j.molcata.2003.12.019

Cited by 24 publications

(13 citation statements)

References 19 publications

(25 reference statements)

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Higher amounts of HRTPs, products of terpinenes and terpinolenes disproportionation, are registered on HPW/MCM-41 in comparison with the ones obtained in presence of MCM-41 sample. The results support the statement that at high α-pinene conversion, the formed limonene (being a more reactive molecule than α-pinene) isomerizes to terpinolenes and terpinenes, that further are transformed into HRTPs products (Dimitrova et al, 2006;Dimitrova et al, 2004). The conversion of methanol on MCM-41 and HPW/MCM-41 samples is presented in Figure 6a.…”

Section: Catalystsupporting

confidence: 84%

“…The silica mesoporous MCM-41 comprises silanol OH groups (external silanol groups, bridging hydroxyl groups, silanol nests, hydroxyl pairs), which are slightly acidic. Methanol conversion and αpinene isomerization are appropriate reactions and have been successfully applied as model reactions for the evaluation of acid site activity and for following the intermediates of the catalytic transformation in heterogeneous conditions (Dimitrova et al,2006;Dimitrova et al, 2004). However, studies concerning the data on the catalytic properties of zeolite-like materials, such as the meso molecular sieve MCM-41, are still rather scared.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Catalytic Activity of Heteropolytungstic Acid Encapsulated into Mesoporous Material Structure

Gunduz¹,

Dimitrova²

2007

International Journal of Chemical Reactor Engineering

View full text Add to dashboard Cite

The paper presents a spectroscopic and catalytic study of encapsulated Keggin type heteropoly acid (12-tungstophosphoric acid, HPW) in the mesopores of MCM-41 molecular sieves. Nitrogen physisorption, FTIR, SEM, XRD and catalytic methods have been used to characterize and compare the properties of the samples. Methanol conversion, ?-pinene isomerization and ethyl acetate oxidation have been applied as model reactions for the evaluation of acid site activity. The combined physicochemical and catalytic investigations clearly show that the introduction of 12-tungstophosphoric acid into MCM-41 causes significant changes in the properties of the sample.

show abstract

Section: Catalystsupporting

confidence: 84%

Section: Introductionmentioning

confidence: 99%

Catalytic Activity of Heteropolytungstic Acid Encapsulated into Mesoporous Material Structure

Gunduz¹,

Dimitrova²

2007

International Journal of Chemical Reactor Engineering

View full text Add to dashboard Cite

show abstract

“…Wang et al [116] studied composite zeolites with Beta zeolite cores and Y zeolite polycrystalline shells (BFZ) and overgrowing Beta zeolite on the core Y crystal (FAU-BEA), showing that the acidity (as Lewis/Brønsted ratio) of the composites, and hence their activity and selectivity, can be tuned by controlling the synthesis conditions. In addition, they stated that the increase in methanol conversion could also be due to the composite's unique crystal structure, which facilitated not only mass but also heat transfer in the exothermic reaction of methanol dehydration, as previously reported by Dimitrova et al [117].…”

Section: Zeolites Based Catalystssupporting

confidence: 55%

Silica-Related Catalysts for CO2 Transformation into Methanol and Dimethyl Ether

et al. 2020

View full text Add to dashboard Cite

The climate situation that the planet is experiencing, mainly due to the emission of greenhouse gases, poses great challenges to mitigate it. Since CO2 is the most abundant greenhouse gas, it is essential to reduce its emissions or, failing that, to use it to obtain chemicals of industrial interest. In recent years, much research have focused on the use of CO2 to obtain methanol, which is a raw material for the synthesis of several important chemicals, and dimethyl ether, which is advertised as the cleanest and highest efficiency diesel substitute fuel. Given that the bibliography on these catalytic reactions is already beginning to be extensive, and due to the great variety of catalysts studied by the different research groups, this review aims to expose the most important catalytic characteristics to take into account in the design of silica-based catalysts for the conversion of carbon dioxide to methanol and dimethyl ether.

show abstract

“…Subsequently, the adsorbed volume amount rises significantly at P/P 0 = 0.9, evidencing an appreciable amount of secondary porosity, as a result of the interparticular porosity [29]. In addition, the type H 1 hysteresis curve also indicates the existence of the capillary condensation in the range of P/P 0 = 0.4-0.5 assigned be from to framework mesoporosity while those of type H 3 hysteresis appears near to complete saturation and could be assigned to interparticle mesoporosity, as for zeolites [30]. Previously, this is shown by SEM and TEM measurements.…”

Section: Porosity Studiesmentioning

confidence: 88%

Binary Oxides with Defined Hierarchy of Pores in the Esterification of Glycerol

et al. 2016

View full text Add to dashboard Cite

Abstract:Various porous binary oxides with elevated textural properties were obtained in this work. The as-synthesized solids were calcined or modified by reflux and extraction processes. Characterizations through SEM, nitrogen physisorption and TEM techniques demonstrated the formation of porous metal oxide networks over all solids. XRD, thermal analyses and FTIR measurements showed the existence of nanosized rutile TiO 2 , tetragonal ZrO 2 , SiO 2 and γ-Al 2 O 3 phases on the solids. The structure and texture of the as-synthesized SiAl sol-gel derived solid resulted in the formation of well-dispersed nanoparticles on the support. The removal of the organic compounds by ethanol extraction or reflux from SiAl resulted in the presence of structures with defined hierarchy of pores. Among the solids studied, the catalytic results in the esterification of glycerol with acetic acid indicated that best performances were obtained over SiAl sample when submitted to extraction and reflux treatments. This was due to the creation of accessible pores, which facilitated the reaction occurrence at glycerol to acetic acid molar ratio = 1:3 and T = 80 • C for 20 h using 75 mg of catalyst. The solids can be reused three times without complete loss of their catalytic performance.

show abstract

Acidic sites in beta zeolites in dependence of the preparation methods

Cited by 24 publications

References 19 publications

Catalytic Activity of Heteropolytungstic Acid Encapsulated into Mesoporous Material Structure

Catalytic Activity of Heteropolytungstic Acid Encapsulated into Mesoporous Material Structure

Silica-Related Catalysts for CO2 Transformation into Methanol and Dimethyl Ether

Binary Oxides with Defined Hierarchy of Pores in the Esterification of Glycerol

Contact Info

Product

Resources

About