Carbon Silica Composites‘2 different approaches’
A) Two step synthesis (CSM): - Carbon deposition in silica template material
B) One step synthesis: - Co-precipitation of silica and carbon source
Synthesis of composites: Partner 1 (Prof. B. Sels, Prof P.A. Jacobs)
In situ polymerisation of FA graphitic carbon T , inert atmosphere
Pyrolysis
Characterisation of composites: Partner 1 & 2 (Prof. Sels, Prof Jacobs // Prof. Hofkens)
CSM nanostructure research: 1) Raman spectroscopy 2) XRD analysis Hypothesis
Observation (HRTEM)
ID/IG size crystallites (length)La = 11 nm
Debye SherrerLc = 0,9 nm → 3 layers graphene
Sorption: Partner 8 & 1 (Prof. Baron, Prof. Denayer // Prof. Sels, Prof Jacobs)
zeolieten
Bipom
CSC
M41s MOF
de Clippel et al.Chemical Communications, 2009
(10.1039/b918864a)
• Molecular probing study of the composite’s pore system– Separation of linear and branched paraffins at low conc.
(pulse chromatography)– Separation of paraffin mixture at high conc. (breaktrough chromatography)– Capacity determination (gravimetric sorption)
Cis-3-hepteenCis-cyclo-octeen
Catalysis: - Shape selectivity: Epoxidation- Polarity Influence Carbon environment: Esterification- Bi-functional catalysts: conversion of dihydroxyaceton- Type & Strength Catalytic Sites: Dimerisation
Epoxidation ofcis-cyclo-octene / cis-3-heptene mixture (competitive experiment)
Critical Parameters: * Amount of carbon deoposition * Pyrolysis Temperature
Reagens selectivity
Catalytic Experiments: Partner 1 (Prof. Sels, Prof Jacobs)
/
1) Shape selectivity
Principle: Carbon acts as selective screen
2) Polarity carbon environment
3) Bi-functional catalysts
O
OH+ CH3OH
O
OCH3 + H2OH+
- Stable- Highly active - Carbon based Acidic Catalyst
Li Peng et al.Catalysis Today, 2009
(doi:10.1016/J.cattod.2009.07.066)
- Composite: 2 components different activation procedures - Example: * Sn grafting (SILICA): Lewis Acidic Sites * H2SO4 treatment (CARBON): Bronsted Acid sites
Weak BronstedAcid
Strong BronstedAcid
Lewis Acid
3) Strength catalytic site (Brönstedt Acid)
Strong Brönsted acid
Weak Brönsted acid
Unsaturated dimer
Saturated dimer
Acid strength of sulfonic acid groups: - Influenced by electron distribution (polyaromatic carbon backbone)- Controllable (# carbon, conditions H2SO4 treatment)
Catalyst Surface area
M² /g
Acid density mmol H+/g
Conversion (%) Selectivity for unsaturated dimers (%)
sugar catalyst
NR50
CBV-720
H2SO4
Si/C50/50-SO3H
< 5
-
780
-
428
0.7
0.8
1.0
20.4
0.33
trace
70
90
100
90
trace
58
36
2.3
91
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