Methylbutynol Conversion as a Probe of Sulfated Zirconia Surface Acidity

Abstract

It reveals the potential of in-situ FTIR studies of the catalytic conversion of methylbutynol in resolving the catalytic acidity of the test catalyst

Full text

References:
1. Ecormier et al, J. Catal. 215.1 (2003): 57-65.
2. A. Osatiashtiani et al, Catalysis Science & Technology 4(2) (2014) 333-342.
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Acknowledgements:
The Egyptian governmental mission
for financial support.
The supervisors ▪Prof. Adam. F. Lee
Minia University ▪Aston University
Methylbutynol Conversion as a Probe of Sulfated Zirconia Surface Acidity
A.I.M.Rabee1, Gamal A.H. Mekhemer1, Karen Wilson2*, M. I. Zaki1
1Chemistry Department, Faculty of Science, Minia University, 61519 El-Minia, Egypt
2European Bioenergy Research Institute, Aston University, Aston Triangle, Birmingham, B4 7ET, UK
*corresponding author:k.wilson@aston.ac.uk
Aston University - Surfaces,
Materials & Catalysis Group
Calcination of 2wt%-SZr(OH)4at 550 oC generates the optimal B/L ratio
with the highest acidic strength.
Calcination of Zr(OH)4at 450 oC results in ZrO2with high amphoteric
surface properties.
Methylbutynol catalytic isomerization into PRENAL is a credible probe
reaction for the establishment of catalytic acidity on sulfated zirconias
Main product formed is HMB calcined Zr(OH)4is amphoteric.
Maximum HMB yield when Zr(OH)4is calcined at 400 - 500oC
MBOH is s a reactive probe to study the surface activity of solid catalysts
which may exhibit acid, base or amphoteric characteristics.[3]
Catalyst development requires improved understanding of the acid –base
properties of SZ.
The use of methylbutynol MBOH to probe the acid-base properties of pure
(Zr) and sulfated (SZ) zirconias using in-situ FTIR studies is reported.
Esterification
Esterification
Trans-Esterification
Isomerization
Dehydration
SZ
Up-grading bio-oils
Biodiesel synthesis
5-HMF
Bi-functional [2]
CxHyO +nH2O
B. Sulfated Zirconia
A. Zirconia
Sulfated zirconia (SZ) catalysts show great promise for converting renewable
feedstocks to fuels and chemicals.[1]
All calcined SZ catalysts decompose MBOH into MBYNE and Acetone,
therefore, expose acidic and basic sites bifunctional catalyst.
Calcination of SZ >450 C leads to PRENAL (1702 cm-1) formation.[4]
PRENAL formation requires strong Brӧnsted-Lewis acid pair-sites[5] to
isomerise MBOH.
The formation of PRENAL is a credible probe for the optimal catalytic
acidity of test catalysts.
0
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100
110
300 400 500 600 700
Initail rate/mmole.h-1.g-1
Conversion/%
Calcination temperature/oC
Pure and sulphate-doped (2 wt %-S)
Zr(OH)4(Sigma Aldrich) were
calcined 350 - 650 oC.
A. Preparation
B. Techniques
XRD
BET In-situ FTIR Pyridine adsorption.
MBOH gas phase reaction.
The calcination of Zr(OH)4at 350 oCis shown to produce m-ZrO2with a
detectable proportion of t-ZrO2. Calcination at ≥650 oC produces m-ZrO2.
Sulfate stabilizes t-ZrO2towards thermal recrystallisation into m-ZrO2.
Zr(OH)4
The absorption of LPy and BPy species
increases with calcination up to 550oC
then weaken upon calcination at higher
temperatures.
The B/L site ratio after evacuation at
100oC, decreases with increasing
calcination temperature.
Comparing the B/L ratio at two different
evacuation temperatures show that
calcination of SZ at 550oC increases the
Brönsted acidic strength.
Increased B/L ratio after outgassing at
200oC attributed to desorption of
weakly bound pyridine at Lewis sites.
In-situ FTIR spectra of Pyridine
adsoroption on calcined SZ.
2SZr(OH)4
C. Characterization
Reaction conditions:
50 mg catalyst, degassing at 400oC for 30 min
cooling
Dosing of 13 torr MBOH spectrum at RT
Heating at 200oC for 5 min spectrum at 200
Absorption subtraction [(spec)RT –(spec)200]
quantitative calculations conv.%