Natural Zeolite Reactivity Towards Ozone: The Role of Acid Surface Sites

2011 ◽  
Vol 14 (2) ◽  
Author(s):  
Serguei Alejandro ◽  
Héctor Valdés ◽  
Claudio. A. Zaror
Keyword(s):  
Lewis Acid ◽  
Natural Zeolite ◽  
Noble Metals ◽  
Ground Level ◽  
Acid Sites ◽  
Air Pollutant ◽  
Lewis Acid Sites ◽  
Surface Sites ◽  
Gaseous Ozone

AbstractGround-level ozone is an air pollutant which interferes with plant photosynthesis, stunts overall growth of some plant species, and harms animal respiratory systems. Activated carbon, synthetic zeolites, metal oxides and noble metals have been used as catalysts to destroy ozone. However, the high costs of these materials impair their application at full-scale. Low cost natural zeolites could be an interesting option for ozone elimination. In this work, the influence of Chilean natural zeolite chemical surface properties on gaseous ozone removal was evaluated. Chemical modifications of Chilean natural zeolite showed the role of acid surface sites and the Si/Al ratio on gaseous ozone abatement. Samples were characterised by nitrogen adsorption at 77 K, elemental analyses, X-ray fluorescence (XRF), temperature-programmed desorption (TPD), and hygroscopic analyses. The influence of air humidity on gaseous ozone removal using natural and modified zeolite samples was also evaluated. The results showed that lower Si/Al ratio corresponds to a higher density of Lewis acid sites. It was found that increasing the zeolite surface area does not improve gaseous ozone removal. The conversion of Brønsted acid sites into Lewis acid sites at 823 K led to an increase on ozone removal.

scholarly journals Catalytic Ozonation of Toluene Using Chilean Natural Zeolite: The Key Role of Brønsted and Lewis Acid Sites

Catalysts ◽  
2018 ◽  
Vol 8 (5) ◽  
pp. 211 ◽  
Author(s):  
Serguei Alejandro-Martín ◽  
Héctor Valdés ◽  
Marie-Hélène Manero ◽  
Claudio Zaror
Keyword(s):  
Lewis Acid ◽  
Natural Zeolite ◽  
Acid Sites ◽  
Catalytic Ozonation ◽  
Lewis Acid Sites ◽  
Brønsted And Lewis Acid

scholarly journals Role of Lewis acid sites of ZSM-5 zeolite on gaseous ozone abatement

2013 ◽  
Vol 231 ◽  
pp. 281-286 ◽  
Author(s):  
Nicolas Brodu ◽  
Marie-Hélène Manero ◽  
Caroline Andriantsiferana ◽  
Jean-Stéphane Pic ◽  
Héctor Valdés
Keyword(s):  
Lewis Acid ◽  
Acid Sites ◽  
Lewis Acid Sites ◽  
Gaseous Ozone

Role of Zinc in Zn-Loaded ZSM-5 Zeolites in the Aromatization of n-Hexane

1999 ◽  
Vol 64 (1) ◽  
pp. 168-176 ◽  
Author(s):  
Edita Rojasová ◽  
Agáta Smiešková ◽  
Pavol Hudec ◽  
Zdenek Židek
Keyword(s):  
Solid State ◽  
Ion Exchange ◽  
Lewis Acid ◽  
Acid Site ◽  
Acid Sites ◽  
Partial Migration ◽  
Simultaneous Presence ◽  
Lewis Acid Sites ◽  
Strong Lewis Acid

Aromatization of n-hexane over zinc-modified ZSM-5 zeolites was investigated. It was shown that incorporation of zinc by ion exchange into cationic positions of NH4-ZSM-5 zeolite causes acid-site strength redistribution and generation of new relatively strong Lewis acid sites in zeolite increasing the selectivity of n-hexane aromatization in comparison with the parent NH4-ZSM-5 zeolite. Simultaneous presence of Lewis and Broensted acid sites in ZSM-5 zeolite does not affect the strength of Broensted acid sites in zeolite. For the activity/selectivity of aromatization of n-hexane on Zn-modified ZSM-5 zeolites, the amount of Zn and its localization in the cationic positions are decisive. The reaction of n-hexane can be also initiated by the Zn species alone in the cationic positions. ZnO species alone as an extraframework phase was found inactive in the catalyst for aromatization of n-hexane. The influence of ZnO addition on the performance of pure ammonium forms of ZSM-5 zeolites in n-hexane conversion is a result of partial migration of zinc into cationic positions of zeolite by solid-state ion exchange.

The role of weak Lewis acid sites for methanol thiolation

2019 ◽  
Vol 9 (2) ◽  
pp. 509-516 ◽  
Author(s):  
Manuel Weber-Stockbauer ◽  
Oliver Y. Gutiérrez ◽  
Ricardo Bermejo-Deval ◽  
Johannes A. Lercher
Keyword(s):  
Lewis Acid ◽  
Active Sites ◽  
Acid Sites ◽  
Lewis Acid Sites ◽  
Strong Base

Weak Lewis acid sites combined with strong base sites of Cs+ supported on WS2 and γ-Al2O3 are the active sites in the thiolation of methanol.

Dehydration of lactic acid to acrylic acid over lanthanum phosphate catalysts: the role of Lewis acid sites

2016 ◽  
Vol 18 (34) ◽  
pp. 23746-23754 ◽  
Author(s):  
Zhen Guo ◽  
De Sheng Theng ◽  
Karen Yuanting Tang ◽  
Lili Zhang ◽  
Lin Huang ◽  
...  
Keyword(s):  
Lactic Acid ◽  
Acrylic Acid ◽  
Lewis Acid ◽  
Acid Sites ◽  
Lewis Acid Sites ◽  
Lanthanum Phosphate ◽  
Lewis Acidic Sites ◽  
Acidic Sites ◽  
Nano Rods

Lewis acidic sites on the surface of lanthanum phosphate nano-rods play a crucial role on the catalytic dehydration of lactic acid to acrylic acid.

scholarly journals Solid Acids for the Reaction of Bioderived Alcohols into Ethers for Fuel Applications

Catalysts ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 172 ◽  
Author(s):  
Federica Zaccheria ◽  
Nicola Scotti ◽  
Nicoletta Ravasio
Keyword(s):  
Physical Properties ◽  
Lignocellulosic Biomass ◽  
Lewis Acid ◽  
Product Distribution ◽  
Acid Sites ◽  
Solid Acids ◽  
Lewis Acid Sites ◽  
Hydroxymethyl Furfural ◽  
Brønsted And Lewis Acid

The use of solids acids in the synthesis of ethers suitable to be used as fuels or fuel additives were reviewed in a critical way. In particular, the role of Brønsted and Lewis acid sites was highlighted to focus on the pivotal role of the acidity nature on the product distribution. Particular emphasis is given to the recently proposed ethers prepared starting from furfural and 5-hydroxymethyl furfural. Thus, they are very promising products that can be derived from lignocellulosic biomass and bioalcohols and possess very interesting chemical and physical properties for their use in the diesel sector.

Sign in / Sign up

Export Citation Format

Share Document