nanoscaled metal fluorides in heterogeneous …...acid fluoride to a partly hydroxylated one through...
TRANSCRIPT
Nanoscaled metal fluorides in
heterogeneous catalysis
Simona M. Coman
Department of Organic Chemistry, Biochemistry and
Catalysis, Faculty of Chemistry,
University of Bucharest
TIMISOARA
25-28 Aprilie 2016
https://sites.google.com/site/materialscatalysis
Magnetic core/shell
nanoparticles
Metal oxides versus metal fluorides synthesis
Hydrolytic sol-gel approach
M-OR + H2O M-OH + ROH (1)
M-OR + M-OH [M-O-M]n + ROH (2a)
M-OH + M-OH [M-O-M]n + H2O (2b)Chem. Rev., 90 (1990) 33
Metal oxides versus metal fluorides synthesis
Fluorolytic sol-gel approach
Angew. Chem. Int. Ed., 42 (2003) 4251 Prof. E. Kemnitz
Metal oxides versus metal fluorides synthesis
Fluorolytic/hydrolytic sol-gel approach
Coman et al., Eur. Pat. Appl, (2007) EP 07 020 498.7
Coman et al, Chem. Eur. J., 14 (2008) 11488
XRD BET
Coman et al., Catal. Today, 152 (2010) 2 Coman et al, Chem. Eur. J., 14 (2008) 11488
Coman et al, Chem. Eur. J., 14 (2008) 11488
Coman et al., Catal. Today, 152 (2010) 2 Coman et al, Chem. Eur. J., 14 (2008) 11488
Fine chemicals synthesis
Pure Appl. Chem., 72 (2000) 1233
Vitamin E, K1 and K1-chromanol synthesis
Coman et al., Eur. Pat. Appl, (2007) EP 07 020 498.7
Coman et al., Adv. Synth. & Catal., 350 (2008) 2517
Coman et al., ChemCatChem, 2 (2010) 92
Fluorolytic/hydrolytic sol-gel approach
Dry, at
100°C or
150°C,
vacuum
HAuCl4
AuCl3(1.0% or 4.0% Au)/MgF2
Incipient wetness impregnation procedure
S. M. Coman and co-workers, Angew. Chem., Int. Ed. Engl., 2010, 49, 8134
k2-weighted EXAFS spectra of the Au catalysts
Sample CN R (Å) σ2
(10–3 Å2)
Filtered
r-range
(Å)
R-factor
Au-100 3.6±0.6 Cl 2.281±0.006 2±1 1.4–2.3 0.056
Au-150 1.3±0.3 Cl
6±1 Au
2.26±0.01
2.883±0.005
3±2
6±1
1.3–3.3 0.124
Au foil 12 Au 2.884 1.8–3.3
HAuCl4: CN- 6 Cl; R (Å) - 2.286 Å
-The precursor preservation after
the thermal treatment at 100 °C.
-The reduced number of Cl
neighbours indicates a Cl-defective
structure of the precursor, but also
small precursor particles.
One-pot synthesis of menthol
Pure Appl. Chem., 72 (2000) 1233
MgF2-71
C = 95.0%
S = 87.0%
d.s. = 84.7%
AlF3-50
C = 97.4%
S = 92.3%
d.s. = 91.7%
Coman et al., Chem.Commun., (2009) 460
Coman et al., Angew. Chem., 49 (2010) 8134
Au4Mg-100
C = 99%
S = 92.5%
d.s. = 87.8%
100 mg catalyst, 1.0 mL citronelal, 5 mL toluen, 80C, 15 atm H2, 22h.
Biomass Valorisation
Fluorolytic/hydrolytic sol-gel approach
Coman et al., ACS Catalysis, 5 (2015) 3013
Coman et al., ChemSusChem, 5 (9) (2012) 1708
xNb@AlF3-y
Nb
O
F FF Al
OF
FFF
AlF
FO
F
Al
F
FF
F
O
H
H
FF
Nb
O
F FAl
F
OOO
H
Al
O
FF
Nb
O
FF Al
FF
FOF
AlF
FO
F
FF
Nb
O
FO
AlO
O
F
FF
Nb@AlF3 Nb@AlF3-T (0C)
Lewis acid sitesLewis acid site
air
T (0C)
Bronsted acid site - vacancy
H H
Bronsted acid site
Lactic acid synthesis
Coman et al., ACS Catalysis, 5 (2015) 3013
Catalysts performances
xNb@AlF3-y
Catalysts stability
ICP-OES measurement Conductivity measurements
xNb@AlF3-y
CONCLUSIONS
The fluorolytic sol-gel synthesis of nanoscopic metal fluorides has given access to new
metal fluoride based catalysts: highly Lewis acidic solids and bi-acidic hydroxide
fluorides with tunable Lewis to Brønsted acidity.
These compounds can be obtained by altering the structure of conventional pure Lewis
acid fluoride to a partly hydroxylated one through a one-pot sol-gel fluorination method.
The nanoscaled metal fluorides and hydroxide fluorides represent not only new,
catalytically active classes of compounds with very high surface areas but are also
excellent candidates to be used as supports for active components like precious (e.g.,
Au) or non-precious (e.g., Nb) metals deposition by incipient wetness impregnation or by
in-situ incorporation during the fluorolytic sol gel synthesis.
The presented catalytic results support their unique behaviour in a organic reactions as
e.g. fine chemicals synthesis or bio-chemicals synthesis from renewable raw materials.
Irrespective of the synthesis approach, the use of nanoscopic fluorides as catalysts or
catalytically functional support offers not only improved efficiency but also additional
green elements in completely agreement with the current trends of 21th century
chemistry.
University of Bucharest Faculty of Chemistry
Prof. Vasile I. Parvulescu Lector Madalina Sandulescu Lector Bogdan Jurca Lector Alina Tirsoaga Asist. Dr. Natalia Candu Dr. Marian Verziu PhD St. Alina Negoi
National Institute of Materials Physics
Dr. Dan Macovei Dr. Cristian Teodorescu Dr. Nicoleta Gheorghe
Dr. Victor Kuncser
Humboldt-Universität zu Berlin, Institut für Chemie
Prof. Erhard Kemnitz
University of Munich (LMU) Department of Chemistry
Dr. Stefan Wuttke
Financial support
Proposed mechanism
II. The conversion of glucose to
lactic acid, glycolic acid and 2-
hydroxybutanoic acid (2-HBA)
HOOH
OH OH
OH O
HO
OH
OH
OH
H
OH
O
Fructose Glucose
HO
OH
O
OH
O
OH
O
O
H2O
H2OO
OH
OH
Lactic acid
HCHO+HO
O
HO
OH
O
ox
Glycolic acid
HCHO
O
O
HO - H2O/2H
O
O
O
OH
OH2-HBA
H2O
LA
LA
BA
LA
BA
I. The two-step
homogeneous/heterogeneous
mechanism of the hydrolysis of
cellulose to glucose
Au3+ H2
H+
Au3+
H
CH2
CH3
R
R =
OH
Au3+
HCH
2
CH3
R
Au3+
H2C
CH3
R
H+
CH3
CH3
R
H2
Au+
2 H-
2H.O2