IR study of water and 2-propanol adsorption on alumina

1988 ◽  
Vol 53 (4) ◽  
pp. 743-748 ◽  
Author(s):  
L. V. Malysheva ◽  
Vladimír Morávek ◽  
E. A. Paukshtis ◽  
E. N. Yurchenko
Keyword(s):  
Low Temperature ◽  
Ir Spectroscopy ◽  
Acid Sites ◽  
Molecular Water ◽  
Lewis Acid Sites ◽  
Irreversible Adsorption ◽  
Oh Groups ◽  
Adsorption Of Water ◽  
Adsorption Of Co ◽  
Ir Study

The adsorption of water and 2-propanol on alumina has been studied by means of IR spectroscopy. Low temperature adsorption of CO has revealed that evolution of Lewis acid sites begins at 80 °C in vacuo when still about 40% of molecular water is present on the surface. The thermodesorption of water proceeds by recombination of neighbouring OH groups. The adsorption of 2-propanol increases the concentration of the nonisolated OH groups and decreases the concentration of isolated ones. The irreversible adsorption influences mostly the C-O and Cβ-H bonds in 2-propanol.

scholarly journals Effect of the calcination temperature of cerium–zirconium mixed oxides on the structure and catalytic performance of WO3/CeZrO2 monolithic catalyst for selective catalytic reduction of NOx with NH3

RSC Advances ◽  
2017 ◽  
Vol 7 (39) ◽  
pp. 24177-24187 ◽  
Author(s):  
Haidi Xu ◽  
Mengmeng Sun ◽  
Shuang Liu ◽  
Yuanshan Li ◽  
Jianli Wang ◽  
...  
Keyword(s):  
Low Temperature ◽  
Selective Catalytic Reduction ◽  
Lewis Acid ◽  
Mixed Oxides ◽  
Catalytic Reduction ◽  
Catalytic Performance ◽  
Acid Sites ◽  
Lewis Acid Sites ◽  
Reduction Of Nox ◽  
Calcined Temperature

The calcined temperature of the carrier obviously affected SCR activity of catalysts, WO3/Ce0.68Zr0.32O2-500 showed the best low-temperature NH3-SCR activity due to its more Lewis acid sites and stronger redox property.

scholarly journals The Keggin Structure: An Important Factor in Governing NH3–SCR Activity Over the V2O5–MoO3/TiO2 Catalyst

2018 ◽  
Vol 148 (4) ◽  
pp. 1228-1235 ◽  
Author(s):  
Rui Wu ◽  
Ningqiang Zhang ◽  
Xiaojun Liu ◽  
Lingcong Li ◽  
Liyun Song ◽  
...  
Keyword(s):  
Low Temperature ◽  
Catalytic Reduction ◽  
Physicochemical Characteristics ◽  
Acid Sites ◽  
Keggin Structure ◽  
Lewis Acid Sites ◽  
Nh3 Scr ◽  
Strong Acidity ◽  
Ft Ir ◽  
Brønsted And Lewis Acid

Abstract Heteropolyacids and their salts have been effectively used in selective catalytic reduction because of the Keggin structure and extraordinarily strong acidity. Catalysts with and without the Keggin structure were synthesized to further investigate the effects of heteropolyoxometallate on low temperature NH3–SCR. XRD, BET, Raman, H2–TPR, NH3–TPD, FT-IR, and SO2–TPD techniques were used to characterize the physicochemical characteristics of the catalysts. Results indicate that catalysts with the Keggin structure had more surface Brönsted and Lewis acid sites, and these catalysts had significantly improved performances in the SCR reaction and in SO2 poisoning resistance. Graphical Abstract

Amine-reactive surface chemistry of zinc phosphate glasses

1995 ◽  
Vol 10 (8) ◽  
pp. 2120-2127 ◽  
Author(s):  
L.S. Hersh ◽  
E.C. Onyiriuka ◽  
W. Hertl
Keyword(s):  
Lewis Acid ◽  
Softening Point ◽  
Zinc Phosphate ◽  
Acid Sites ◽  
Phosphate Glasses ◽  
Polymer Chains ◽  
Lewis Acid Sites ◽  
Oh Groups ◽  
Chemical Studies ◽  
Glass Surfaces

Surface chemical studies on zinc phosphate glasses were carried out with an ammonia probe using FTIR and XPS. Low softening point zinc phosphate glasses can be co-extruded with high softening point polymers to form polymer filled blends. NH3 reacts with P-OH groups (Br⊘nsted acid sites) to form bound NH4+ and with the zinc ions (Lewis acid sites) to form coordinately bound NH3. Bulk nitridation reactions, forming various P-N bonds to >100 nm, occur concurrently. The glass surfaces were depleted in Zn compared to the batch compositions. Exposure to ambient water vapor removed Lewis acid bound ammonia; aqueous washing removed both types. Di- and tri-methyl amines also reacted with surface Br⊘nsted and Lewis acid sites. These amine reactions have the potential for binding polymer chains to the glass surface.

IR study of the low temperature adsorption of CO on tetragonal zirconia and sulfated tetragonal zirconia

1998 ◽  
Vol 126 (1-2) ◽  
pp. 107-128 ◽  
Author(s):  
Claudio Morterra ◽  
Giuseppina Cerrato ◽  
Silvia Di Ciero
Keyword(s):  
Low Temperature ◽  
Tetragonal Zirconia ◽  
Adsorption Of Co ◽  
Ir Study

scholarly journals The H2O Effect on Cu Speciation in Cu-CHA-Catalysts for NH3-SCR Probed by NH3 Titration

Catalysts ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 759
Author(s):  
Roberta Villamaina ◽  
Federica Gramigni ◽  
Umberto Iacobone ◽  
Shaojun Liu ◽  
Isabella Nova ◽  
...  
Keyword(s):  
Low Temperature ◽  
Acid Sites ◽  
Lewis Acid Sites ◽  
Nh3 Scr ◽  
Scr Catalysts ◽  
Nh3 Adsorption ◽  
Dry Conditions ◽  
Dry And Wet Conditions ◽  
Hydrolysis Of ◽  
Cu Ions

The present work is focused on the effect of water on NH3 adsorption over Cu-CHA SCR catalysts. For this purpose, samples characterized by different SAR (SiO2/Al2O3) ratios and Cu loadings were studied under both dry and wet conditions. H2O adversely affects NH3 adsorption on Lewis acid sites (Cu ions) over all the tested catalysts, as indicated by the decreased NH3 desorption at low temperature during TPD. Interestingly, the NH3/Cu ratio, herein regarded as an index for the speciation of Cu cations, fell in the range of 3–4 (in the presence of gaseous NH3) or 1–2 (no gaseous NH3) in dry conditions, in line with the formation of different NH3-solvated Cu species (e.g., [CuII(NH3)4]2+ and [CuII(OH)(NH3)3]+ with gaseous NH3, [Z2CuII(NH3)2]2+ and [ZCuII(OH)(NH3)]+ without gaseous NH3). When H2O was fed to the system, on the contrary, the NH3/Cu ratio was always close to 3 (or 1), while the Brønsted acidity was slightly increased. These results are consistent both with competition between H2O and NH3 for adsorption on Lewis sites and with the hydrolysis of a fraction of Z2CuII species into ZCuIIOH.

scholarly journals Bulk tungsten-substituted vanadium oxide for low-temperature NOx removal in the presence of water

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Yusuke Inomata ◽  
Hiroe Kubota ◽  
Shinichi Hata ◽  
Eiji Kiyonaga ◽  
Keiichiro Morita ◽  
...  
Keyword(s):  
Low Temperature ◽  
Vanadium Oxide ◽  
Acid Sites ◽  
Bronsted Acid ◽  
Brønsted Acid ◽  
Lewis Acid Sites ◽  
Brønsted Acid Sites ◽  
Brönsted Acid ◽  
Brönsted Acid Sites ◽  
Bronsted Acid Sites

AbstractNH3-SCR (selective catalytic reduction) is important process for removal of NOx. However, water vapor included in exhaust gases critically inhibits the reaction in a low temperature range. Here, we report bulk W-substituted vanadium oxide catalysts for NH3-SCR at a low temperature (100–150 °C) and in the presence of water (~20 vol%). The 3.5 mol% W-substituted vanadium oxide shows >99% (dry) and ~93% (wet, 5–20 vol% water) NO conversion at 150 °C (250 ppm NO, 250 ppm NH3, 4% O2, SV = 40000 mL h−1 gcat−1). Lewis acid sites of W-substituted vanadium oxide are converted to Brønsted acid sites under a wet condition while the distribution of Brønsted and Lewis acid sites does not change without tungsten. NH4+ species adsorbed on Brønsted acid sites react with NO accompanied by the reduction of V5+ sites at 150 °C. The high redox ability and reactivity of Brønsted acid sites are observed for bulk W-substituted vanadium oxide at a low temperature in the presence of water, and thus the catalytic cycle is less affected by water vapor.

Behaviour of CoNaA zeolites in interaction with water

1980 ◽  
Vol 45 (1) ◽  
pp. 9-16 ◽  
Author(s):  
Blanka Wichterlová ◽  
Ludmila Kubelková ◽  
Pavel Jírů
Keyword(s):  
Catalytic Activity ◽  
Infrared Spectroscopy ◽  
Adsorbed Water ◽  
The State ◽  
Molecular Water ◽  
Oh Groups ◽  
Adsorption Of Water ◽  
Stretching Vibrations

The influence of dehydration and adsorption of water on the coordination of cations, the state of adsorbed water, and stretching vibrations of CoNaA and NaA zeolites was investigated by means of electronic and infrared spectroscopy. Complexes of Co2+ change their symmetry from octahedral through tetrahedral to planar trigonal. The role of ligands play both skeletal oxygens and molecular water. The formation of OH groups either on skeleton or on Co2+ ions was not found; the existence of these groups was assumed in the literature to explain the catalytic activity of CoNaA zeolites in the isomerization of butenes.

The Effect of Acidity of Al and Fe Silicates with MFI Structure on Benzene and Toluene Alkylation with Isopropyl Alcohol

1996 ◽  
Vol 61 (8) ◽  
pp. 1115-1130 ◽  
Author(s):  
Jiří Čejka ◽  
Naděžda Žilková ◽  
Blanka Wichterlová
Keyword(s):  
Kinetic Study ◽  
Molecular Sieves ◽  
Isopropyl Alcohol ◽  
Acid Sites ◽  
Transport Rate ◽  
Reaction Products ◽  
Oh Groups ◽  
Benzene Alkylation ◽  
Toluene Alkylation ◽  
Low Strength

Kinetic study of toluene and benzene alkylation with isopropyl alcohol on alumo- and ferrisilicates of MFI structure has shown that the alkylation activity does not follow the acidity (both the number and strength of bridging OH groups) of these molecular sieves. The rate of the overall reaction is controlled by the desorption/transport rate of bulky, strongly adsorbed cymenes and cumene. A higher concentration of n-propyltoluenes compared to n-propylbenzene, both undesired reaction products, formed via a bimolecular isomerization of isopropyl aromate with benzene or toluene, was due to the higher reactivity of isopropyltoluene with toluene in comparison with that of cumene with benzene. It is concluded that ferrisilicates of MFI structure possessing low strength acid sites appear to be promising catalysts for achieving both a high isopropyl- and para-selectivity in toluene alkylation to p-cymene.

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