scholarly journals Zirconia catalysed acetic acid ketonisation for pre-treatment of biomass fast pyrolysis vapours

2018 ◽  
Vol 8 (4) ◽  
pp. 1134-1141 ◽  
Author(s):  
Hessam Jahangiri ◽  
Amin Osatiashtiani ◽  
James A. Bennett ◽  
Mark A. Isaacs ◽  
Sai Gu ◽  
...  
Keyword(s):  
Acetic Acid ◽  
Lewis Acid ◽  
Fast Pyrolysis ◽  
Acid Sites ◽  
Active Species ◽  
Acid Base ◽  
Lewis Acid Sites ◽  
Base Pairs ◽  
Pre Treatment ◽  
Biomass Fast Pyrolysis

Weak Lewis acid sites (and/or resulting acid–base pairs) on monoclinic ZrO2 are identified as the active species responsible for acetic acid ketonisation to acetone.

scholarly journals Ga/HZSM-5 Catalysed Acetic Acid Ketonisation for Upgrading of Biomass Pyrolysis Vapours

Catalysts ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 841 ◽  
Author(s):  
Hessam Jahangiri ◽  
Amin Osatiashtiani ◽  
Miloud Ouadi ◽  
Andreas Hornung ◽  
Adam F. Lee ◽  
...  
Keyword(s):  
Acetic Acid ◽  
Carboxylic Acids ◽  
Lewis Acid ◽  
Energy Content ◽  
Vapour Phase ◽  
Acid Sites ◽  
Active Species ◽  
Biomass Pyrolysis ◽  
Lewis Acid Sites ◽  
Bio Oil

Pyrolysis bio-oils contain significant amounts of carboxylic acids which limit their utility as biofuels. Ketonisation of carboxylic acids within biomass pyrolysis vapours is a potential route to upgrade the energy content and stability of the resulting bio-oil condensate, but requires active, selective and coke-resistant solid acid catalysts. Here we explore the vapour phase ketonisation of acetic acid over Ga-doped HZSM-5. Weak Lewis acid sites were identified as the active species responsible for acetic acid ketonisation to acetone at 350 °C and 400 °C. Turnover frequencies were proportional to Ga loading, reaching ~6 min−1 at 400 °C for 10Ga/HZSM-5. Selectivity to the desired acetone product correlated with the weak:strong acid site ratio, being favoured over weak Lewis acid sites and reaching 30% for 10Ga/HZSM-5. Strong Brønsted acidity promoted competing unselective reactions and carbon laydown. 10Ga/HZSM-5 exhibited good stability for over 5 h on-stream acetic acid ketonisation.

THE USE OF THE COMBINATION OF FTIR, PYRIDINE ADSORPTION, 27Al AND 29Si MAS NMR TO DETERMINE THE BRÖNSTED AND LEWIS ACIDIC SITES

2016 ◽  
Vol 78 (6) ◽  
Author(s):  
Djoko Hartanto ◽  
Lai Sin Yuan ◽  
Sestriana Mutia Sari ◽  
Djarot Sugiarso ◽  
Irmina Kris Murwarni ◽  
...  
Keyword(s):  
Lewis Acid ◽  
Aluminum Atom ◽  
Xrd Analysis ◽  
Acid Sites ◽  
Mas Nmr ◽  
Molar Ratio ◽  
Pyridine Adsorption ◽  
Lewis Acid Sites ◽  
27Al Mas Nmr ◽  
Pre Treatment

Lewis and Brönsted acidity were studied on ZSM-5 with combination of pyridine adsorption and FTIR vibration, ZSM-5 synthesized using kaolin Bangka Indonesia with an increase in the molar ratio of Si/Al 30-60 without pre-treatment and without organic templates and with seeds silicalite. Interestingly, the intensity of the infrared showed an increase of band vibration pyridine as absorbed Brönsted and Lewis acid sites in a molar ratio increase of Si/Al in ZSM-5, indicating an increase in the number of silanol (Brönsted acid) and deformed silica (Lewis acid) because the amount of Aluminum in ZSM-5 decrease with increase Si/Al but amount acidity increase. 29Si and 27Al MAS NMR analysis was supported by the results of infrared to indicate that all of the aluminum atom is coordinated with their neighbors are the same in ordering the ZSM-5 framework and 27Al MAS NMR showed a sharp peak of all the variations of Si/Al except the Si/Al 30 shows a low peak area. XRD analysis supported that the ZSM-5 structure formed is pure and crystal and a decrease in crystallinity proven for more than Si/Al 50, that defects silica occurs in ZSM-5, this corresponds to the growing number of Lewis acid sites caused by defects silica described the infrared results.

The role of Lewis acid–base pair sites in ZnO–ZnCr2O4 catalysts for cyclization via dehydrogenative condensation of crude glycerol and 1,2-propanediamine for the synthesis of 2,6-dimethylpyrazine

2017 ◽  
Vol 41 (18) ◽  
pp. 9875-9883 ◽  
Author(s):  
Krishna Vankudoth ◽  
A. Hari Padmasri ◽  
Reema Sarkari ◽  
Vijay Kumar Velisoju ◽  
Naresh Gutta ◽  
...  
Keyword(s):  
Lewis Acid ◽  
Base Pair ◽  
Spectroscopic Data ◽  
Crude Glycerol ◽  
Acid Sites ◽  
Acid Base ◽  
Lewis Acid Sites

DRIFT spectroscopic data revealed the role of surface Lewis acid sites on the synthesis of 2,6-dimethylpyrazine.

scholarly journals Glucose Conversion into 5-Hydroxymethylfurfural over Niobium Oxides Supported on Natural Rubber-Derived Carbon/Silica Nanocomposite

Catalysts ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 887
Author(s):  
Rujeeluk Khumho ◽  
Satit Yousatit ◽  
Chawalit Ngamcharussrivichai
Keyword(s):  
Natural Rubber ◽  
Lewis Acid ◽  
Value Added ◽  
Acid Sites ◽  
Superior Performance ◽  
Lewis Acidity ◽  
Lewis Acid Sites ◽  
Niobium Oxides ◽  
Silica Nanocomposite ◽  
Loading Amount

5-Hydroxymethylfurfural (HMF) is one of the most important lignocellulosic biomass-derived platform molecules for production of renewable fuel additives, liquid hydrocarbon fuels, and value-added chemicals. The present work developed niobium oxides (Nb2O5) supported on mesoporous carbon/silica nanocomposite (MCS), as novel solid base catalyst for synthesis of HMF via one-pot glucose conversion in a biphasic solvent. The MCS material was prepared via carbonization using natural rubber dispersed in hexagonal mesoporous silica (HMS) as a precursor. The Nb2O5 supported on MCS (Nb/MCS) catalyst with an niobium (Nb) loading amount of 10 wt.% (10-Nb/MCS) was characterized by high dispersion, and so tiny crystallites of Nb2O5, on the MCS surface, good textural properties, and the presence of Bronsted and Lewis acid sites with weak-to-medium strength. By varying the Nb loading amount, the crystallite size of Nb2O5 and molar ratio of Bronsted/Lewis acidity could be tuned. When compared to the pure silica HMS-supported Nb catalyst, the Nb/MCS material showed a superior glucose conversion and HMF yield. The highest HMF yield of 57.5% was achieved at 93.2% glucose conversion when using 10-Nb/MCS as catalyst (5 wt.% loading with respect to the mass of glucose) at 190 °C for 1 h. Furthermore, 10-Nb/MCS had excellent catalytic stability, being reused in the reaction for five consecutive cycles during which both the glucose conversion and HMF yield were insignificantly changed. Its superior performance was ascribed to the suitable ratio of Brønsted/Lewis acid sites, and the hydrophobic properties generated from the carbon moieties dispersed in the MCS nanocomposite.

On the nature of framework Brønsted and Lewis acid sites in ZSM-5

Zeolites ◽  
1997 ◽  
Vol 19 (4) ◽  
pp. 288-296 ◽  
Author(s):  
G.L. Woolery ◽  
G.H. Kuehl ◽  
H.C. Timken ◽  
A.W. Chester ◽  
J.C. Vartuli
Keyword(s):  
Lewis Acid ◽  
Acid Sites ◽  
Lewis Acid Sites ◽  
Brønsted And Lewis Acid

Ethylene polymerization on lewis acid sites of a reduced V2O5/Al2O3 catalyst

1992 ◽  
Vol 46 (1) ◽  
pp. 199-207 ◽  
Author(s):  
S. Ishida ◽  
S. Imamura ◽  
F. Ren ◽  
Y. Tatematsu ◽  
Y. Fujimura
Keyword(s):  
Lewis Acid ◽  
Ethylene Polymerization ◽  
Acid Sites ◽  
Lewis Acid Sites ◽  
Al2o3 Catalyst
Sign in / Sign up

Export Citation Format

Share Document