Generation of protonic acid sites originating from molecular hydrogen over H-ZSM-5

1992 ◽  
Vol 48 (1) ◽  
pp. 17-22 ◽  
Author(s):  
Junpei Tsuji ◽  
Kohki Ebitani ◽  
Hideshi Hattori ◽  
Hideaki Kita
Keyword(s):  
Molecular Hydrogen ◽  
Acid Sites ◽  
Protonic Acid

scholarly journals On the Role of Protonic Acid Sites in Cu Loaded FAU31 Zeolite as a Catalyst for the Catalytic Transformation of Furfural to Furan

Molecules ◽  
2021 ◽  
Vol 26 (7) ◽  
pp. 2015
Author(s):  
Łukasz Kuterasiński ◽  
Małgorzata Smoliło-Utrata ◽  
Joanna Kaim ◽  
Wojciech Rojek ◽  
Jerzy Podobiński ◽  
...  
Keyword(s):  
Active Sites ◽  
Acid Sites ◽  
Bronsted Acid ◽  
Brønsted Acid ◽  
Brønsted Acid Sites ◽  
Protonic Acid ◽  
Brönsted Acid ◽  
Brönsted Acid Sites ◽  
Bronsted Acid Sites

The aim of the present paper is to study the speciation and the role of different active site types (copper species and Brønsted acid sites) in the direct synthesis of furan from furfural catalyzed by copper-exchanged FAU31 zeolite. Four series of samples were prepared by using different conditions of post-synthesis treatment, which exhibit none, one or two types of active sites. The catalysts were characterized by XRD, low-temperature sorption of nitrogen, SEM, H2-TPR, NMR and by means of IR spectroscopy with ammonia and CO sorption as probe molecules to assess the types of active sites. All catalyst underwent catalytic tests. The performed experiments allowed to propose the relation between the kind of active centers (Cu or Brønsted acid sites) and the type of detected products (2-metylfuran and furan) obtained in the studied reaction. It was found that the production of 2-methylfuran (in trace amounts) is determined by the presence of the redox-type centers, while the protonic acid sites are mainly responsible for the furan production and catalytic activity in the whole temperature range. All studied catalysts revealed very high susceptibility to coking due to polymerization of furfural.

ISOMERIZATION OF C5-C7 LINEAR ALKANES OVER WO3-ZRO2 UNDER HELIUM ATMOSPHERE

2015 ◽  
Vol 75 (6) ◽  
Author(s):  
Sugeng Triwahyono ◽  
Aishah Abdul Jalil ◽  
Hairul Amiza Azman ◽  
Che Rozid Mamat
Keyword(s):  
High Activity ◽  
Surface Area ◽  
Tetragonal Phase ◽  
Atomic Hydrogen ◽  
Acid Sites ◽  
Helium Atmosphere ◽  
Ftir Study ◽  
Protonic Acid ◽  
Catalytic Isomerization ◽  
Linear Alkanes

The effect of WO3 on the properties and catalytic isomerization of C5-C7 linear alkanes over ZrO2 was studied under helium atmosphere. The WO3-ZrO2 was prepared by impregnation of Zr(OH)4 with an aqueous (NH4)6[H2W12O40], followed by calcination at 1093 K for 3 h in air. The amount WO3 was 10 wt%. XRD and BET studies showed that the introduction of WO3 stabilizes the tetragonal phase of ZrO2, leading to larger surface area and stronger acidity of ZrO2. Pyridine FTIR study verified the interaction of WO3 with ZrO2 formed strong Lewis and Bronsted acid sites. The presence of WO3 increased the catalytic isomerization of C5-C7 linear alkanes. The conversion of C5, C6 and C7 reached 1.3, 2.6 and 5.1 %, respectively. While the selectivity of isopentane, isohexane and isoheptane reached 15.6, 20.5 and 19.5 %, respectively. The high activity of WO3-ZrO2 was due to the ability of WO3 to adsorb and dissociate linear alkane to form hydrogen and alkane radical in which the atomic hydrogen underwent to the formation of protonic acid sites and hydride. The presence of protonic acid sites and hydride determined the activity of WO3-ZrO2.

Catalytic Properties of Fluorine Modified SmNa-Y Zeolites

1992 ◽  
Vol 57 (4) ◽  
pp. 781-787 ◽  
Author(s):  
Stanisłav Kowalak ◽  
Maria Pawłowska ◽  
Kenneth J. Balkus
Keyword(s):  
Catalytic Properties ◽  
Acid Sites ◽  
Y Zeolites ◽  
Cumene Cracking ◽  
Toluene Disproportionation ◽  
Zeolite Nay ◽  
Polyvalent Cations ◽  
Protonic Acid ◽  
Acid Catalyzed ◽  
Catalyzed Reactions

It is known that mild fluorination of zeolites, including those modified with polyvalent cations, increases their activity for acid catalyzed reactions. In this study we report the reactivity of fluorine modified Sm(III) exchanged zeolite NaY. Mild fluorination of SmNaY reduces the activity of strong protonic acid sites and increases the contribution of weak aprotic acid centres. Results for cumene cracking and toluene disproportionation as well as for 1-hexene isomerization are reported.

scholarly journals Effect of iridium loading on the formation of protonic acid sites over Ir/Pt-HZSM5

2013 ◽  
Vol 9 (1) ◽  
Author(s):  
S. Triwahyono ◽  
H.D. Setiabudi ◽  
A.A. Jalil ◽  
S.N. Timmiati ◽  
N.H.R. Annuar ◽  
...  
Keyword(s):  
Ftir Spectroscopy ◽  
Lewis Acid ◽  
Esr Spectroscopy ◽  
Acid Sites ◽  
Acidic Properties ◽  
Lewis Acid Sites ◽  
Brønsted Acid Sites ◽  
Protonic Acid ◽  
Concomitant Decrease ◽  
Brønsted And Lewis Acid

The Ir/Pt-HZSM5 with different iridium loading (0.3-1.0 wt%) was prepared by impregnation of iridium on Pt-HZSM5. The acidic properties of Ir/Pt-HZSM5 were studied by FTIR spectroscopy, while the activity of the catalysts was tested for n-pentane isomerization in a microcatalytic pulse reactor.The IR results of adsorbed 2,6-lutidine showed that all catalysts possessed strong Brönsted and Lewis acid sites in the outgassing at 473 K and below.When Ir/Pt-HZSM5 was heated in hydrogen, protonic acid sites were formed with concomitant decrease of Lewis acid sites. An increase in iridiumloading continuously decreased the Lewis and Brönsted acid sites and inhibited the formation of protonic acid sites induced by hydrogen. The formationof protonic acid sites induced by hydrogen was also confirmed by the formation of electron detected by ESR spectroscopy. Additionally for n-pentaneisomerization, an increase in iridium loading decreased the yield of isopentane due to the inhibition in the formation of protonic acid sites via hydrogenspillover phenomenon.

EFFECT OF SUPPORT ON MOLYBDENUM OXIDE ACIDITY FOR N-HEPTANE ISOMERIZATION

2016 ◽  
Vol 78 (8-3) ◽  
Author(s):  
Nor Aiza Abdul Fatah ◽  
Sugeng Triwahyono ◽  
Aishah Abdul Jalil
Keyword(s):  
Molybdenum Oxide ◽  
Lewis Acid ◽  
Molecular Hydrogen ◽  
Acid Sites ◽  
Mesostructured Silica ◽  
Catalyst Acidity ◽  
Effect Of Support ◽  
Mcm 41 ◽  
High Octane ◽  
Heptane Conversion

Skeletal isomerization of alkanes into the corresponding branched isomers has attracted many attentions as a reaction to produce clean fuel with high octane quality. In this study, molybdenum oxide (MoO3) catalyst supported on mesostructured silica nanoparticles (MSN), HZSM-5 and MCM-41 activity were being tested towards n-heptane isomerization at 623 K. The catalyst acidity was characterized by using FTIR pre-adsorb pyridine. The results showed that MoO3-MSN possesses highest Lewis acid and lowest Brönsted acid concentrations. The catalytic testing towards n-heptane isomerization showed that MoO3-MSN exhibited the highest n-heptane conversion of 18.7 % at 623 K. It was suggested that the high Lewis acid in the MoO3-MSN may facilitate the formation of active protonic acid sites from molecular hydrogen through hydrogen spillover mechanism and hence improves the n-heptane conversion.

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