Transcript MS PowerPoint - Catalysis Eprints database

Transesterification Reaction by using Lewis acid based
solid catalyst
T.M.SankaraNarayanan
National Centre for Catalysis Research
04.04.2009
What is BIODIESEL?
BIOFUELS or BIODIESEL
Biodiesel is the name of a clean burning alternative fuel
derived from plant or vegetable oils (vegetable derived esters
or VDE) that can be used as a blend with or as a total
substitute for petroleum diesel. It can be used in compressionignition (diesel) engines even without any engine
modifications.
• Biodiesel is a variety of ester-based oxygenated fuels made from
vegetable oils or animal fats.
• It is indigenous, renewable, biodegradable, and a nontoxic diesel
fuel substitute.
• The first diesel engine was powered using peanut oil by Rudolf
Diesel in 1895.
• He demonstrated the engine in 1900 at the World Exposition in
Paris where he took the highest prize.
RAW MATERIALS
•Rapeseed
•Sunflower oil ( Italy and Southern France)
•Soybean oil (USA & Brazil)
•Palm oil (Malaysia)
•lard, used frying oil (Austria), Jatropha
(India,Nicaragua & South Americas)
Advantages
• Alternative fuel for diesel engines
• Made from vegetable oil or animal fat
• Meets health effect testing (CAA)
• Lower emissions, High flash point (>300F), Safer
• Biodegradable, Essentially non-toxic.
• Chemically, biodiesel molecules are mono-alkyl esters produced usually
from triglyceride esters
• Can be mixed in any ratio with petroleum diesel fuel or can be used
100%.
• Produces less particulates, soot, carbon monoxide, and hydrocarbon
emissions than petroleum diesel fuel.
• Known to provide a substantial reduction in cancer risks.
• Produces pleasant exhaust odor unlike petroleum diesel.
• Has very good lubricity properties. Used as lubricity additive in
severely hydro-treated diesel fuel.
• Oral toxicity effects are similar to those associated with laxatives.
Relative Greenhouse Gas Emissions
B100
B100 = 100% Biodiesel
B20 = 20% BD + 80% PD
Electric
Diesel Hybrid
B20
Ethanol 85%
Diesel
LPG
CNG
Gasoline
0
20
40
60
80
100
120
140
Data from “A Fresh Look at CNG: A Comparison of Alternative Fuels”,
Alternative Fuel Vehicle Program, 8/13/2001
160
Catalyst for transesterification Reactions
People are working on both homogeneous and Heterogeneous
Catalysis.
We are going to focus only heterogeneous catalyst
This talk mainly focused on Lewis acid based
hydrophobic solid acid catalysts transesterification
reactions
P.Rathnasamy et al Applied Catalysis A: General 314 (2006) 148–159
P.Rathnasamy et al. Journal of Catalysis 241 (2006) 34–44
Double-metal cyanide (DMC) complexes possess zeolite-like cage
structures
Now a days have gained considerable attention for their interesting
magnetic, electrochromic, magneto- optic, photomagnetic and
nanomagnetic properties
These Prussian blue-analogues are insoluble in most of the organic
solvents and even in aqua regia.
They are currently used as catalysts for the copolymerization of
epoxides andCO2
Catalyst preparation
K4[Fe(CN)6]
0.01 mol
40 mL of double-distilled water
solution 1
ZnCl2
A 15-g sample of
tri-block copolymer
0.1 mol
100 mL of distilled water
and 20 mL of tert-butanol
Solution 2
2 mL of distilled water
and 40 mL of tert-butanol
solution 3
Solution 2 was added to solution 1 slowly over 1 h at 323 K under vigorous stirring. A white solid
was precipitated. Solution 3 was then added to the above reaction mixture over 5–10 min, and
stirring was continued for another1 h.
After activating at453 K for 4 h
Fe–Zn-1
Synthesis of Fe/Zn DMC catalysts
Tentative structure of double metal cyanide Fe–Zn complex
Catalyst characterization
XRF analyses
Elemental analyses
X-ray Diffraction
Diffuse reflectance Infrared Spectroscopy
Diffuse reflectance UV–vis spectroscopy
Temperature Programmed Desorption
Influence of the method of preparation
X-ray Diffraction
X-ray Diffraction
Scanning electron micrographs
of Fe–Zn-1 catalyst
Diffuse reflectance Infrared Spectroscopy
Diffuse reflectance UV–vis spectroscopy
Methanolysis of sunflower oil over various double-metal cyanide
catalysts effects of catalyst composition, method of preparation,
polymer surfactant and catalyst reuse
Reaction conditions: catalyst = 3 wt% of sunflower oil; oil = 5 g;
oil:methanol = 1:15 mol/mol; temperature, =443 K; reaction time = 8 h.
a Oil converion was estimated based on the isolated yield of glycerol.
Identification and Quantification of Lewis Acid sites
By using FTIR and TPD.
Correlation Acid sites by using of FTIR and TPD
DRIFT spectroscopy of adsorbed pyridine on Fe–Zn double-metal cyanide complexes at (a) 323 K
and (b) 448 K. (c) NH3-TPD of Fe–Zn complexes. Panel (d)shows the deconvolution plot of the
NH3-TPD curve for Fe–Zn-1.
Diffuse reflectance Infrared Spectroscopy
DRIFT spectra of adsorbed pyridine on Fe–Zn double metal cyanide catalysts.
The deconvolution plot of the NH3-TPD curve for Fe–Zn-1.
Influence of free fatty acids (FFA)
(a) amount of the catalyst,
(b) alcohol-to-oil molar ratio,
Influence of reaction parameters
(c) reaction temperature
(d) reaction time on ethanolysis of
margarine oil over Fe–Zn-1 catalyst
Reaction conditions: catalyst (Fe–Zn-1), 3 wt% of oil; oil, 15 g; CH3OH, 8.2 g; oil:CH3OH(mol) =
1:15; temperature, =443 K; reaction time, 8 h; reactor type, closed autoclave (100 ml). a Except
Safflower (Kardi) and margarine rest all are unrefined (raw) vegetable oils.
Influence of the type of alcohol on the tranesterification of
rubber seed and margarine oils over Fe–Zn-1 catalyst.
Reaction conditions: catalyst, 3 wt%of oil; oil, 5 g; oil:alcohol = 1:15 mol/mol; temperature, 443
K; reaction time, 8 h.
Methanolysis of sunflower oil in the presence of added water over
double-metal cyanide Fe–Zn catalyst (Fe–Zn-1)
Reaction conditions: catalyst (Fe–Zn-1), 3 wt% of oil; unrefined sunflower oil, 5 g; CH3OH, 2.75
g; oil:CH3OH (mol) = 1:15; temperature, =443 K; reaction time, 8 h; reactor type, closed autoclave
(100 ml).a Conversion of oil was estimated based on the glycerol recovered.
Correlation of esterification (oleic acid) and transesterification
(sunflower oil) activities over different double-metal cyanide
catalysts
Reaction conditions: catalyst, 3 wt% of acid or oil; oleic acid or oil, 5 g; temperature, 443 K. For
esterification reaction—oleic acid:CH3OH = 1:2 mol/mol and reaction time, 45 min. For
transesterification reactions—oil:CH3OH = 1:15 mol/
mol and reaction time = 8 h.
Active sites for transesterification of sunflower oil with
methanol: structure–activity relationship
NH3-desorption in the region 353–473 K due to Lewis acid sites (Fig. 5d).
Relative intensity of the 1490 cm1 band characteristic of Lewis acid sites in the IR spectra
of adsorbed pyridine per mol of Zn2+ ions (Fig. 5a)
Reaction conditions: catalyst, 3 wt% of oil; sunflower oil (average molecular weight = 890), 5 g;
oil:CH3OH (mol) = 1:15; temperature, =443 K; reaction time,
8 h; reactor type, closed autoclave (100 ml).
Turnover frequency (TOF) = mmol of sunflower oil converted per mmol of Zn2+ ions per
hour.
Numbers in parentheses are normalized values.
Transesterification of propene carbonate with various alcohols
over double metal cyanide Fe–Zn catalyst (Fe–Zn-1)
a) Reaction conditions: Fe–Zn-1 (pre activated at 453 K for 4 h), 0.25 g; PC, 10 mmol; ROH, 100
mmol; reaction temperature, 443 K; reaction time, 8 h. b) Product isolated by column chromatography.
Isolated yield is reported. 1,2-propene glycol was formed in an equivalent amount.
c)TON = moles of PC converted per mole of catalyst.
Reaction of dimethyl carbonate with various alcohols
over Fe–Zn-1 catalyst
Reaction of dimethyl carbonate with various alcohols over Fe–
Zn-1 catalyst
Reaction conditions: Fe–Zn-1, 0.25 g; DMC, 10 mmol; ROH, 100 mmol; reaction temperature,
443 K; reaction time, 8 h.
Transesterification of propene carbonate (PC) with
methanol
Transesterification of propene carbonate (PC) with methanol. Influence of (a) reaction
temperature, (b) CH3OH to PC ratio and (c) amount of catalyst on DMC yield. Reaction
conditions for (a): catalyst Fe–Zn-1 (activated at 453 K for 4 h), 0.25 g; PC, 10 mmol; methanol,
100 mmol, reaction time, 8 h. Reaction conditions for (b): catalyst Fe–Zn-1 (activated at 453 K for
4 h), 0.25 g; reaction temperature, 443 K; PC, 10 mmol; reaction time, 8 h. Reaction conditions for
(c): PC, 10 mmol; methanol, 100 mmol; reaction temperature, 443 K; reaction time, 4 h.
Run no.
ROH
Dialkyl carbonate yield
(mol%)
TON
1
Methanol
86.6
26
2
Methanol (recycle-1)
83.2
25
3
Methanol (recycle-2)
83.5
25
4
Methanol (recycle-3)
84.9
25
5
Methanol (recycle-4)
83.2
25
6
Methanol (recycle-5)
82.6
25
7
Ethanol
79.4
24
8
Propanol
77.5
23
9
Butanol
69.3
21
10
Hexanol
62.5
19
11
Benzyl alcohol
77.8
23
Tentative reaction mechanism for transesterification of propene
carbonate with alcohols (ROH) over Lewis acid Zn2+ cations in
Fe–Zn double metal cyanide catalysts.
Conclusions
A novel application of double-metal cyanide (DMC) complexes as highly active,
heterogeneous catalysts for production of biofuels and lubricants from vegetable oil
esterification/transesterification reactions is reported.
These catalysts are Lewis acidic, hydrophobic (at reaction temperatures of about 443 K)
and insoluble in most of the solvents including aqua regia.
A catalyst containing of Fe2+–Zn2+ and tert-butanol in its
(K4Zn4[Fe(CN)6]36H2O2(tert-BuOH); Fe–Zn-1) was superior to others.
composition
The role of surfactant molecules in the synthesis is probably to increase surface area and
acid sites density thereby enhancing catalytic activity in both the esterification
andtransesterification reactions.
There is a correlation between catalytic activity and the concentration of acid sites as
measuredby NH3 or pyridine adsorptions.Coordinatively unsaturated Zn2+ are the
probable active (Lewis acid) sites for both the esterification and transesterification
reactions.
References:
•An Overview of Biodiesel and Petroleum Diesel Life Cycles
•Presentation at the NH Science Teacher Association
(NHSTA) Annual Conference, Session 15, March 22, 2005,
Philips Exeter Academy. Exeter, NH
Thank you