Green Synthesis of Veratraldehyde Using Potassium Promoted Lanthanum-Magnesium Mixed Oxide Catalyst

Article abstract of DOI:10.1021/acs.oprd.7b00127

Veratraldehyde is an important chemical used in perfumery, agrochemical, and pharmaceutical industries. Current processes of manufacture of veratraldehyde use homogeneous catalysts, which make them highly polluting, creating problems of disposal of effluents and product purity. In the current work, veratraldehyde was synthesized from O-alkylation of vanillin with an environmentally benign reagent, dimethyl carbonate. A series of potassium loaded La₂O₃-MgO were prepared by the incipient wetness impregnation method, and their performance was evaluated vis-à-vis MgO, La₂O₃, La₂O₃-MgO, and a series of 1-4 wt % K/La₂O₃-MgO. All catalysts were characterized by different techniques, such as N₂ adsorption/desorption, XRD, TGA-DSC, FT-IR, CO₂-TPD, and SEM techniques. The effect of different loadings (1-4 wt %) of potassium on La₂O₃-MgO was studied, among which 2 wt % K/La₂O₃-MgO showed the best activity and selectivity due to high dispersion of potassium and high basicity in comparison with the rest. The activity of 2 wt % K/La₂O₃-MgO in O-methylation of vanillin with dimethyl carbonate (DMC) was closely associated with basicity. Various parameters were studied to achieve the maximum yield of the desired product. The maximum conversion was found with catalyst loading of 0.03 g/cm³ and mole ratio of vanillin and DMC of 1:15 at 160 °C in 2 h. The reaction follows pseudo-first-order kinetics for the O-methylation of vanillin. The energy of activation was found to be 13.5 kcal/mol. Scale-up was done using the kinetic model to observe that the process could be scaled up using the process parameters. The overall process is clean and green.

Full text of DOI:10.1021/acs.oprd.7b00127

Subscriber access provided by CORNELL UNIVERSITY LIBRARY
Full Paper
Green synthesis of veratraldehyde using potassium
promoted lanthanum-magnesium mixed oxide catalyst
Jayaram Molleti, and Ganapati D. Yadav
Org. Process Res. Dev., Just Accepted Manuscript • Publication Date (Web): 23 May 2017
Downloaded from http://pubs.acs.org on May 23, 2017
Just Accepted
“Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted
online prior to technical editing, formatting for publication and author proofing. The American Chemical
Society provides “Just Accepted” as a free service to the research community to expedite the
dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts
appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been
fully peer reviewed, but should not be considered the official version of record. They are accessible to all
readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered
to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published
in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just
Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor
changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers
and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors
or consequences arising from the use of information contained in these “Just Accepted” manuscripts.
Organic Process Research & Development is published by the American Chemical
Society. 1155 Sixteenth Street N.W., Washington, DC 20036
Published by American Chemical Society. Copyright © American Chemical Society.
However, no copyright claim is made to original U.S. Government works, or works
produced by employees of any Commonwealth realm Crown government in the course
of their duties.

Page 1 of 34
Organic Process Research & Development
1
2
3
4
Organic Process Research & Development
5
6
7
Manuscript ID: opꢀ2017ꢀ00127k
Revised: May 19, 2017
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Green synthesis of veratraldehyde using potassium
promoted lanthanumꢀmagnesium mixed oxide catalyst
Jayaram Molleti and Ganapati D. Yadav*
Department of Chemical Engineering
Institute of Chemical Technology
Nathalal Parekh Marg, Matunga
Mumbaiꢀ400 019, India
*Author to whom correspondence be addressed.
Email: gd.yadav@ictmumbai.edu.in
Ph: +91ꢀ22ꢀ3361ꢀ1001; F: +91ꢀ22ꢀ3361ꢀ1020
ACS Paragon Plus Environment
1

Organic Process Research & Development
Page 2 of 34
1
2
3
4
Table of Content (TOC) Graphic
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
ACS Paragon Plus Environment
2

Page 3 of 34
Organic Process Research & Development
1
2
3
4
ABSTRACT
5
6
7
8
9
Veratraldehyde is an important chemical used in perfumery, agrochemical and pharmaceutical
industries. Current processes of manufacture of veratraldehyde use homogeneous catalysts which
make them highly polluting creating problems of disposal effluents and product purity. In the
current work, veratraldehyde was synthesized from Oꢀalkylation of vanillin with an
environmentally benign reagent, dimethyl carbonate. A series of potassium loaded La2O3ꢀMgO
were prepared by incipient wetness impregnation method and their performance was evaluated
visꢀàꢀvis MgO, La2O3, La2O3ꢀMgO and a series of 1ꢀ4 wt % K/ La2O3ꢀMgO. All catalysts were
characterized by different techniques such as N2 adsorption/desorption, XRD, TGAꢀDSC, FTꢀIR,
CO2ꢀTPD and SEM techniques. Effect of different loadings (1ꢀ4 wt %) of potassium on La2O3ꢀ
MgO was studied among which 2 wt % K/La2O3ꢀMgO showed the best activity and selectivity
due to high dispersion of potassium and high basicity in comparison with the rest. The activity
of 2 wt % k/ La2O3ꢀMgO in Oꢀmethylation of vanillin with dimethyl carbonate (DMC) was
closely associated with basicity. Various parameters were studied to achieve maximum yield of
the desired product. The maximum conversion was found with catalyst loading of 0.03 g/cm3 and
mole ratio of vanillin and DMC of 1:15 at 160 °C in 2 h. The reaction follows pseudo first order
kinetics for the Oꢀmethylation of vanillin. The energy of activation was found to be 13.5
kcal/mol. Scaleꢀup was done using the kinetic model to observe that the process could be scaled
up using the process parameters. The overall process is clean and green.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
KEYWORDS: Vanillin; Dimethyl carbonate; Oꢀmethylation; Strong base; Veratraldehyde;
La2O3ꢀMgO; K/ La2O3ꢀMgO
ACS Paragon Plus Environment
3

Organic Process Research & Development
Page 4 of 34
1
2
3
4
INTRODUCTION
5
6
7
8
Lignocellulosic biomass, abundantly available everywhere, is a source of renewable chemicals
and fuels.1 Biomass is converted to obtain phenolic compounds, sugars, and fine chemicals via
gasification, anaerobic digestion, fermentation, pyrolysis, and transesterification.2
Lignocellulosic biomass mainly contains cellulose, hemiꢀcellulose and lignin. Lignin is main
renewable source for chemicals such as guaiacol, vanillic acid, phenol, benzene, acetic acid and
methanol.3 Vanillin is also one of the important chemicals obtained from lignin by condensation
of guaiacol with glyoxylic acid.4 Heterogeneous catalysis has tremendous scope for conversion
of biomass into value addedꢀchemicals.5
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Veratraldehyde is present in Cymbopogon jevenensis essential oil. It is extensively used in
perfume compounds, food aromatizers, odorants and pharmaceutical intermediates.6
Veratraldehyde can be obtained from Oꢀmethylation of vanillin with alkylating agents. The
traditional synthesis of Oꢀmethylation reactions involved harmful alkylating agents like dimethyl
8
9
sulfate,7 methyl halides, and diazomethane, or nontoxic alkylating agents under harsh
condition, using a solvent like dimethyl formamide.10 These reagents are hazardous which
produce a large amount of waste. These reactions are also reported with methanol as alkylating
11
agent which require a strong acid
or zeolite as catalyst. Usually, they require higher
temperature and produce various side products.12 Hence, development of a green process for the
synthesis of veratraldehyde is essential.
Dimethyl carbonate (DMC) is a sustainable, nonꢀtoxic, and biodegradable reagent.13 It can be
used either as a methoxycarbonylating agent (˂120 °C) or as a methylating agent (˃120 °C). In
recent years, various applications of DMC were reported.14 DMC was used in methylation of
ACS Paragon Plus Environment
4

Page 5 of 34
Organic Process Research & Development
1
2
phenols,15 indoles,16 and anilines17 as well as methylation of active methylene groups.18 It is an
alternative for hazardous alkylating agents.
3
4
5
6
7
8
9
Generally, methylation reaction by DMC requires high temperatures (˃160 °C) and long
reaction times. In order to attain reasonable conversion, strong organic15,19 or inorganic bases
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
20,21
have been used in excess quantities which need to be neutralized at the end of reaction
leading to dissolved solids in the effluent. It also adds to impurities in the desired product. The
synthesis of veratraldehyde by Oꢀmethylation of vanillin with DMC as a methylating agent has
been reported using homogeneous catalysts. Chern et al.22 reported 78 % yield to veratraldehyde
using K2CO3 as a base. Nelson et al.23 reported 96 % yield to veratraldehyde over a base K2CO3
and 18ꢀcrownꢀ6 using CH3I as a methylating agent.
Recently Thomas24 demonstrated this reaction with 77 % yield to veratraldehyde using 1,3ꢀ
dimethylimadazoliumꢀ2ꢀcarboxylate (DMIꢀCO2) catalyst in ~3h at 160 °C. The homogenous
catalysts showed high catalytic performance but there are several problems such as homogeneous
catalysts have to be neutralized and cannot be recycled, thereby making the process polluting.
From Green Chemistry point of view, the replacement of homogeneous catalysts by
heterogeneous is most desirable since the catalyst can be easily recovered, reused and also a
variety of reactor configurations are possible bringing flexibility in operation. Besides,
heterogeneous catalysts have many more advantages such as they present fewer disposal
problems, allow easier separation and recovery of the products. They are nonꢀcorrosive and offer
environmentally benign processes for the synthesis of fine chemicals. Cheaper materials of
constructions can be used. Hence, there is heterogeneous catalysts are superior and needed to
overcome those problems associated with homogeneous catalysts.
Over the last decades, mixed oxides have been extensively used due to their distinctive
physical and chemical properties. 25 Lanthanum oxide (La2O3) is a strongest basic oxide, but the
activity of is low due to its low surface area. Its activity increased when it mixed with
26,27
magnesium oxide (MgO) due to increasing basicity.
La2O3ꢀMgO mixed oxide have been
widely used in several chemical reactions such as Wittig reaction,28 Michael addition reaction,29
WadsworthꢀEmmons reaction,30 synthesis of glycerol carbonate,31 epoxidation of an olefin 32 and
ACS Paragon Plus Environment
5

Organic Process Research & Development
Page 6 of 34
1
2
transesterification reaction.33 Several researchers demonstrated that the use of potassium
precursors such as KF.34 K2CO3, 35 KNO3, 36,37 and KOH 38 can help the formation of super base.
A number of base catalyzed reactions using hydrotalcites, supported hydrotalcites, mixed metal
oxides and supported mixed oxide have been studied for industrially important reactions in our
laboratory.39–44 Very recently, Yin et al.45 demonstrated Knoevenagel condensation reaction
over 10 wt % KOH/La2O3 as a solid super base.
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Here in this report, an efficient and environmentally friendly process for solventless Oꢀ
methylation of vanillin with DMC over 2 % K/La2O3ꢀMgO catalyst. The fresh and spent 2 % K/
La2O3ꢀMgO has been fully characterized by different techniques. The catalyst activity was
compared with the different solid base catalysts such as MgO, La2O3, and different loadings of
potassium on La2O3ꢀMgO support. The effect of different kinetic parameters was studied to
explore the activity of catalyst in the reaction of vanillin with DMC. Plausible reaction kinetics,
reaction mechanism and catalyst reusability were studied.
EXPERIMENTAL SECTION
Chemicals
Magnesium nitrate, Lanthanum nitrate, urea and potassium carbonate were procured from
Thomas Baker Chemicals, Mumbai. Vanillin, dimethyl carbonate and nꢀdecane were obtained
from SD Fine chemicals limited, Mumbai.
Preparation of catalyst
Lanthanumꢀ magnesium mixed oxide (La2O3ꢀMgO) with different mole ratio of La and Mg
were prepared by hydrothermal method using urea as a precipitating agent.42 The role of urea as
a precipitating agent is well described by Ogawa et al.46 The typical process for synthesis of Laꢀ
ACS Paragon Plus Environment
6

Page 7 of 34
Organic Process Research & Development
1
2
3
4
5
6
7
8
9
Mg with 1:3 molar ratio is as follows, 2.1 g of La (NO3)3.9H2O, 3.86 g of Mg (NO3)3.H2O and 6
g of urea were dissolved in 150 mL distilled water stirred for 1 h until the solution become
homogeneous. Then it was transferred into Teflon lined bomb reactor and heated 160 ºC for 12 h
in muffle furnace. After cooling the reactor to room temperature obtained solid material was
washed with distilled water. After filtration, the solid material was dried at 120 ºC. MgO and
La2O3 catalyst were prepared by same procedure and were used after calcined at 750 ºC for 4 h.
Similarly, we used same method for the preparation of La2O3, and MgO catalysts.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
The potassium modified La2O3ꢀMgO was prepared by wet impregnation method. The requisite
quantity of K2CO3 was dissolved in 2 mL of water. The resultant solution was added to 1 g of
La2O3ꢀMgO via wet impregnation technique, under vigorous agitation at 80 ºC. On completion
of adsorption of Potassium solution onto the surface of mixed oxide, the resultant material dried
at 120 ºC for 10 h then calcined at 750 ºC for 4 h in air. Here we prepared 1 to 4 wt % K on
La2O3ꢀMgO by taking appropriate amount of precursor and catalyst were named as 1wt % K/
La2O3ꢀMgO, 2 wt % K/ La2O3ꢀMgO, 3 wt % K/ La2O3ꢀMgO and 4 wt % K/ La2O3ꢀMgO,
respectively.
General procedure for O-methylation of vanillin
A stainlessꢀsteel Amar autoclave (Mumbai, India) of 100 mL equipped with a 4 blade pitch
turbine impeller was used for the reaction. The agitation speed was maintained at ±5 rpm of the
experimental value. Calculated amount of reactants were taken in the autoclave. The autoclave
was tightened and desired temperature was set, after attaining the temperature zeroꢀminute
sample was removed. A typical standard experiment, 0.02 mole of vanillin, 0.3 mole of DMC
and 0.2 mL of nꢀdecane as an internal standard with a catalyst loading of 0.03 g/ cm3 against
ACS Paragon Plus Environment
7

Organic Process Research & Development
Page 8 of 34
1
2
total volume (30 cm3) of the liquid. The reaction mass was heated at 160 °C with speed of
agitation 800 rpm for 2 h.
3
4
5
6
7
8
9
Method of analysis
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Samples were withdrawn periodically and analysed by GC (Chemito Model 1000 with FID
detector) using a capillary column BPꢀ1 (length 30 m and inner diameter 0.32 mm). The injector
and detector temperature were programmed from 60 to 300 °C with a ramp rate of 10 °C/min.
The results were based on the decrease in conversion of the limiting reagent, vanillin. Product
was confirmed by GCꢀMS (Perkin Elmer, Clarius model 500) on Eliteꢀ1 capillary column (length
30 m and inner diameter 0.25 mm).
After completion of the reaction, the autoclave was cooled to room temperature and the
catalyst separated from the reaction mixture by filtration. The catalyst was washed with methanol
(4 mL x 2) to confirm that no product is adsorbed on the catalyst. The filtrate was collected and
solvent was evaporated at reduced pressure to obtain oily product, which was confirmed by GCꢀ
MS. The isolated yield was 89 % because of loss of product during the isolation procedure.
Characterization methodology
Catalysts were characterized by different techniques. The detailed description of
characterization methodology is published in recent literature.47 Details is also provided in
supplementary.
RESULTS AND DISCUSSION
Catalyst characterization
XRD
ACS Paragon Plus Environment
8

Page 9 of 34
Organic Process Research & Development
1
2
3
4
5
6
7
8
9
The XRD patterns of La2O3ꢀMgO and K/ La2O3ꢀMgO with 1ꢀ 4 wt % loading of potassium are
showed in Figure 1. La2O3ꢀMgO (Figure 1(a)) catalyst depicted the presence of La2MgOX
(JCPDS: 42ꢀ339), La2O3 (JCPDS: 40ꢀ1281) and MgO (JCPDS: 27ꢀ759). The existence of
La2MgOX confirms the interaction between the La2O3 and MgO constituents during the synthesis
of La2O3ꢀMgO.27,48
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
All potassium loaded catalysts showed similar XRD patterns of La2O3ꢀMgO because
potassium can be well dispersed on the La2O3ꢀMgO support. Figure 1(b), (c), (d), (e) and (f)
shows no typical diffraction peaks corresponding to the K2CO3 (2θ =12°,25°, 32°,38°and 41°),
which suggest that the potassium carbonate has completely decomposed. With the loading of
potassium, there was disappearance of La2O3 peak at 2θ=30.36° and the detection of new peak
attribute to K2O (JCPDS: 27ꢀ431).49,50 This K2O phase may be the origin of basicity and high
catalytic activity. The crystalline size of the La2O3ꢀMgO and 2 wt % K/ La2O3ꢀMgO was
calculated using Scherrer’s formula. The average crystallite size of La2O3ꢀMgO and 2 wt % K/
La2O3ꢀMgO was 15.16 nm and 30.89 nm respectively. The XRD pattern of 2 wt % K/ La2O3ꢀ
MgO and reused catalysts were compared and XRD patterns are almost same which confirms
that prepared catalyst is stable.
ACS Paragon Plus Environment
9

Organic Process Research & Development
Page 10 of 34
1
2
3
4
5
6
7
(f)
8
9
(e)
(d)
(c)
(b)
(a)
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
10
20
30
40
50
60
70
80
2-Theta-Scale
Figure 1. XRD of pattern of (a) La2O3ꢀMgO, (b) 1 wt % K/ La2O3ꢀMgO, (c) 2 wt % K/ La2O3ꢀ
MgO, (d) 3 wt % K/ La2O3ꢀMgO, (e) 4 wt % K/ La2O3ꢀMgO and (f) reused 2 wt % K/ La2O3ꢀ
MgO catalyst
FT-IR
Figure 2 shows FTꢀIR spectra of La2O3ꢀMgO, 1 wt % K/ La2O3ꢀMgO, 2 wt % K/ La2O3ꢀMgO,
3 wt % K/ La2O3ꢀMgO, 4 wt % K/ La2O3ꢀMgO and reused 2 wt % K/ La2O3ꢀMgO catalyst. The
strong band at 650 cmꢀ1, which is attributable to the lattice vibration of Lanthanum oxide bond.
The band at 3560 cmꢀ1indicates the presence of hydroxide species of adsorbed water molecule
and two bands at 1460 and 1380 cmꢀ1 due to the carbonate species. The weak band at 1080 cmꢀ1
indicates the presence of symmetric (CO3)2ꢀ. The band at 1460 cmꢀ1 reveals that the inclusion of
potassium promotes the formation of basic sites and the adsorption of carbon dioxide on the
surface of La2O3ꢀMgO. FTꢀIR spectra virgin and used catalysts were signifying that there were
no structural changes. It also indicates that there were no externally adsorbed species on the
surface of the 2 wt % K/ La2O3ꢀMgO catalyst.
ACS Paragon Plus Environment
10

Page 11 of 34
Organic Process Research & Development
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Figure 2. FTIR of (a) La2O3ꢀMgO, (b) 1 wt % K/ La2O3ꢀMgO, (c) 2 wt % K/ La2O3ꢀMgO, (d) 3
wt % K/ La2O3ꢀMgO, (e) 4 wt % K/ La2O3ꢀMgO and (f) reused 2 wt % K/ La2O3ꢀMgO catalyst
Surface area and pore size analysis
The BET N2 adsorption/desorption isotherms of La2O3ꢀMgO and different loadings of
potassium (1ꢀ4 wt %) on La2O3ꢀMgO are shown in Figure 3. All catalysts showed a type IV
isotherm and type H3 hysteresis loop, indicative of the formation of mesoporous material. The
surface area, pore volume and average pore diameter of La2O3ꢀMgO catalyst are 48 m2 gꢀ1, 0.13
cm3 gꢀ1 and 11 nm, respectively (Table 1). After the introduction of potassium, there is a decline
in surface area as well as pore volume. Diez and coworkers51,52 reported that the introduction of
alkali metals on MgO would result in a decrease in surface area and pore volume. The decline in
pore volume and surface area upon potassium loading observed over La2O3ꢀMgO and K/ La2O3ꢀ
MgO catalysts are in good agreement with the results of SEM and CO2ꢀTPD analysis. The
ACS Paragon Plus Environment
11

Organic Process Research & Development
Page 12 of 34
1
2
3
4
5
6
porous parameters of 2 wt % K/ La2O3ꢀMgO and reused 2 wt % K/ La2O3ꢀMgO catalysts were
observed almost same.
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Table 1. Surface properties of various synthesized catalysts for Oꢀmethylation of vanillin
Average
pore
diameter
(nm)
BJH pore
volume
(cm3/g)
BET surface
area (m2/g)
No.
Catalysts
1
2
3
4
5
6
La2O3ꢀMgO
48
22
20
18
13
11
25
28
21
23
26
0.13
0.12
0.11
0.09
0.07
0.10
1 wt % K/ La2O3ꢀMgO
2 wt % K/ La2O3ꢀMgO
3 wt % K/ La2O3ꢀMgO
4 wt % K/ La2O3ꢀMgO
Reused 2 wt % K/ La2O3ꢀMgO 19
(f)
(e)
(d)
(c)
(b)
(a)
0
0.2
0.4
0.6
0.8
1
Relative Pressure (P/P0)
ACS Paragon Plus Environment
12

Page 13 of 34
Organic Process Research & Development
1
2
3
4
5
6
7
8
9
Figure 3. N2 adsorptionꢀdesorption plot for the (a) La2O3ꢀMgO, (b) 1 wt % K/ La2O3ꢀMgO, (c) 2
wt % K/ La2O3ꢀMgO, (d) 3 wt % K/ La2O3ꢀMgO, (e) 4 wt % K/ La2O3ꢀMgO and (f) reused 2 wt
% K/ La2O3ꢀMgO catalyst
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
CO2-TPD
CO2ꢀTPD analysis was used to measure the basic nature of sites generated on the surface of the
samples. As showed in Figure 4 La2O3ꢀMgO catalyst CO2 desorption peaks were observed at 285
ºC and 470 ºC corresponds moderate /strong basic sites, and the quantity of CO2 was 0.36 and
0.38 mmolgꢀ1. The introduction of potassium results in increase in the desorption temperature
and enhancement in the amount of CO2 desorption. 2 wt % K/ La2O3ꢀMgO catalyst showed
desorption peaks at 106 ºC, 324 ºC, 498 ºC and 745 ºC corresponds to weak, moderate, strong
and super basic sites and the quantity of CO2 desorbed were 0.15, 0.21, 0.05 and 1.09 mmolgꢀ1,
respectively. The desorption peak at 745 ºC is a clear indication of super basic sites.53 Further
increasing concentration of potassium, there is a decline in the basicity of 3 and 4 wt % K/
La2O3ꢀMgO catalysts (Table 2). This is due to the coverage of excess potassium on the surface of
basic sites. The basicity of fresh and used catalyst shows almost similar results.
Table 2. CO2ꢀTPD analysis for various synthesized catalysts
CO2ꢀTPD analysis
No.
Basicity (mmol gꢀ1)
Catalysts
Weak
0.02
0.05
0.04
0.10
Moderate/strong Total
1
La2O3
0.25
0.31
0.70
0.88
0.27
0.36
0.74
0.98
2
3
4
MgO
La2O3ꢀMgO
1 wt % K/ La2O3ꢀMgO
ACS Paragon Plus Environment
13

Organic Process Research & Development
Page 14 of 34
1
2
3
4
5
6
7
8
9
5
6
7
8
2 wt % K/ La2O3ꢀMgO
3 wt % K/ La2O3ꢀMgO
4 wt % K/ La2O3ꢀMgO
Reused 2 wt % K/ La2O3ꢀMgO
0.15
0.09
0.08
0.13
1.35
1.17
1.05
1.33
1.50
1.26
1.13
1.46
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
0.12
0.1
0.08
0.06
0.04
0.02
0
50
150
250
350
450
550
650
750
Temperature (°C)
Figure 4. CO2ꢀTPD pattern of 2 wt % K/ La2O3ꢀMgO
TGA-DSC
TGAꢀDSC analysis of 2 wt % K/ La2O3ꢀMgO catalyst was carried out from 50 to 700 ºC
(Figure 5). Two endothermic peaks were observed in DSC curve; first peak was observed at 80
to 130 ºC due to removal of water (humidity) and resulted in 8 % weight loss. Second
endothermic peak between 320 °C and 400 ºC was due to evolution of CO2 and decomposition of
oxycarbonate corresponding to 12 % weight loss to get stable oxide forms. The overall analysis
shows around 20 % weight loss and the catalyst was stable after 450 ºC up to 700 ºC.
ACS Paragon Plus Environment
14

Page 15 of 34
Organic Process Research & Development
1
2
3
4
5
6
7
8
9
4.00
3.00
2.00
1.00
0.00
100
95
90
85
80
75
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
0
100
200
300
400
500
600
700
Temparature (°C)
Figure 5. TGAꢀDSC analysis of 2 wt % K/ La2O3ꢀMgO
SEM
The SEM images of La2O3ꢀMgO, 2 wt % K/ La2O3ꢀMgO catalysts are shown in Figure 6.
La2O3ꢀMgO catalyst forms a spherical and dendritic structure. There is no agglomeration takes
place after the introduction of 2 wt % potassium on La2O3ꢀMgO. Hence, it is assumed that with
low loading of potassium, a high dispersion was obtained and the La2O3ꢀMgO support intact its
original structure.
Figure 6. SEM images of (a) La2O3ꢀMgO and (b) 2 wt % K/ La2O3ꢀMgO
ACS Paragon Plus Environment
15

Organic Process Research & Development
Page 16 of 34
1
2
3
4
Catalytic reaction
5
6
7
8
The reaction of Oꢀmethylation of vanillin with DMC using 2 wt % K/ La2O3ꢀMgO catalyst
given in Scheme 1.
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Scheme 1. Oꢀmethylation of vanillin with DMC
Efficacy of various catalysts.
Activity of different solid base catalysts towards synthesis of veratraldehyde was studied
using vanillin and DMC. The reaction was carried out using vanillin to DMC mole ratio 1:15 at
800 rpm with catalyst loading of 0.03 g/cm3 on the basis of total volume (30 mL). A variety of
catalysts such as, MgO, La2O3, La2O3ꢀMgO with different loadings (1 to 4 wt %) of potassium
on La2O3ꢀMgO like 1 wt % K/ La2O3ꢀMgO, 2 wt % K/ La2O3ꢀMgO, 3 wt % K/ La2O3ꢀMgO and
4 wt % K/ La2O3ꢀMgO catalysts were studied for Oꢀmethylation reaction (Figure 7). It was
significant that no Cꢀmethylated byꢀproducts were identified and the selectivity to veratraldehyde
was always 100 % regardless of type of catalysts. From Table 2 the basicity of different catalyst
is in the following order: La2O3 (least) ˂MgO ˂La2O3ꢀMgO ˂1 wt % K/ La2O3ꢀMgO ˂4 wt %
K/ La2O3ꢀMgO ˂3 wt % K/ La2O3ꢀMgO ˂2 wt % K/ La2O3ꢀMgO (highest). The conversion and
activity of the catalyst follow the same trend as La2O3 (least) ˂MgO ˂La2O3ꢀMgO ˂1 wt % K/
La2O3ꢀMgO ˂4 wt % K/ La2O3ꢀMgO ˂3 wt % K/ La2O3ꢀMgO ˂2 wt % K/ La2O3ꢀMgO
(highest). Thus, it is concluded that basicity of catalyst plays a major role in conversion and
ACS Paragon Plus Environment
16

Page 17 of 34
Organic Process Research & Development
1
2
3
4
5
6
selectivity. We have also plotted CO2 uptake and conversion for different catalysts which further
supports that basicity of catalysts is the governing parameter (Figure 7).
7
8
9
The obvious reason for excellent conversion of vanillin is the maximum basicity of catalyst
observed at loading of 2 wt % potassium on La2O3ꢀMgO. It is due to increase of moderate and
strong basic sites. The further increase in the loading of potassium leads to decrease in the
conversion possibly due to blocking of pores by excess amount of potassium. The activity of
MgO, La2O3 catalysts was found to be less due to lack of strong basic sites. The optimum
loading of potassium is 2 wt %, which is good agreement with the results of CO2ꢀTPD (Table 1)
and BET surface area (Table 2). Hence, 2 wt % K/ La2O3ꢀMgO was selected as superior catalyst
for detailed kinetics.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
100
80
60
40
20
0
1.8
1.5
1.2
0.9
0.6
0.3
0
Conversion
CO2 uptake
Catalysts
ACS Paragon Plus Environment
17

Organic Process Research & Development
Page 18 of 34
1
2
3
4
5
6
7
8
9
Figure 7. Effect of various catalysts and CO2 uptake on conversion of vanillin: vanillin 0.02
mol, DMC 0.3 mol, speed of agitation 800 rpm, temperature 160 ºC, total volume 30 cm3,
reaction time 2 h, catalyst loading 0.03 g/cm3
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Effect of speed of agitation.
The agitation speed was studied at 400, 600, 800 and 1000 rpm at 160 °C in order to
understand the effect of external mass transfer resistance on the rate of reaction (Figure 8). It is
clear that beyond 800 rpm there is no effect on the conversion of vanillin signifying that the mass
transfer resistance was absent. Thus, further experiments were carried out 800 rpm. Also,
theoretical calculations were done as reported earlier to calculate mass transfer rate.47,54 The
calculated mass transfer rates were found to be very high in comparison of the reaction rate
which confirms that there is no effect of external mass transfer resistance at and beyond 800 rpm.
100
80
60
40
20
0
0
20
40
60
80
100
120
Time (min)
Figure 8. Effect of speed of agitation on conversion of vanillin: vanillin 0.020 mol, DMC 0.3
mol, catalyst 2 wt % K/ La2O3ꢀMgO, temperature 160 ºC, total volume 30 cm3, reaction time 2 h,
catalyst loading 0.03 g/cm3. (♦) 400 rpm, (■) 600 rpm, (▲) 800 rpm, (x) 1000 rpm
ACS Paragon Plus Environment
18

Page 19 of 34
Organic Process Research & Development
1
2
3
4
Effect of catalyst loading.
5
6
7
8
The influence of catalyst loading on conversion of vanillin was studied from 0.01 to 0.04 g/cm3
(Figure 9). Vanillin conversion increases with the increase in catalyst loading which is due to
proportional increase in number of active sites. Catalyst loading from 0.03ꢀ0.04 g/cm3 there is no
appreciable changes in the conversion of vanillin. It is due to surpassing the number of active
sites available for reaction than the number of vanillin molecules actually present for the
reaction. Therefore, further reaction was performed on 0.03 g/cm3 catalyst loading. Figure10
shows initial rate of reaction increases linearly with the catalyst loading which confirms absence
of mass transfer resistance. WieszꢀPrater criterion or modulus (CWP) was also calculated at 0.03
g/cm3 to find that the Oꢀmethylation of vanillin reaction was free from intra ꢀparticle diffusion
limitation. The details related to these can be easily found in our earlier literature.52 In this case,
CWP value was found to be 3.15× 10ꢀ3 which is very less than unity and hence there is no role of
intraꢀparticle diffusion resistance on the overall rate of reaction.
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
ACS Paragon Plus Environment
19

Organic Process Research & Development
Page 20 of 34
1
2
3
4
5
6
7
8
9
100
80
60
40
20
0
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
0
20
40
60
80
100
120
Time (min)
Figure 9. Effect of catalyst loading on conversion of vanillin: vanillin 0.020 mol, DMC 0.3
mol, catalyst 2 wt % K/La2O3ꢀMgO, temperature 160 ºC, total volume 30 cm3, reaction time 2 h,
speed of agitation 800 rpm. (♦) 0.01 g/cm3, (■) 0.02 g/cm3, (▲) 0.03 g/cm3, (x) 0.04 g/cm3
0.025
y = 0.5433x
R² = 0.98
0.02
0.015
0.01
0.005
0
0
0.01
0.02
0.03
0.04
0.05
Catalyst loading (g/cm3)
ACS Paragon Plus Environment
20

Page 21 of 34
Organic Process Research & Development
1
2
3
4
5
6
7
8
9
Figure 10. Plot of initial rate on conversion of vanillin: vanillin 0.020 mol, DMC 0.3 mol,
catalyst 2 wt % K/ La2O3ꢀMgO, temperature 160 ºC, total volume 30 cm3, reaction time 2 h,
speed of agitation 800 rpm.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Effect of mole ratio
Mole ratio of vanillin to DMC was studied at 1:5, 1:10, 1:15 and 1:20 to know its effect on the
rate of reaction by keeping the total reaction volume constant (Figure 11). The conversion of
vanillin increases with increase in mole ratio. The conversion of vanillin at 1:5 mole ratio is 50
% which increased to 96 % at 1:15 mole ratio. There was no significant change in conversion in
between 1:15 to 1:20 mole ratio. Therefore it is concluded that 1:15 mole ratio is ideal parameter
for this reaction and used for further reactions.
100
80
60
40
20
0
0
20
40
60
80
100
120
Time (min)
Figure 11. Effect of mole ratio on conversion of vanillin: vanillin 0.02 mol, catalyst 2 wt % K/
La2O3ꢀMgO, temperature 160 ºC, total volume 30 cm3, reaction time 2 h, speed of agitation 800
rpm. (♦) 1:05, (■) 1:10, (▲) 1:15, (x) 1:20.
ACS Paragon Plus Environment
21

Organic Process Research & Development
Page 22 of 34
1
2
3
4
Effect of temperature
5
6
7
8
The effect of temperature was studied at 140, 150, 160 and 170 °C (Figure 12) to see its effect
and to prove that the reaction is only kinetically controlled and all other resistance have been
successfully avoided. The increase in temperature resulted in increase in the initial rate of
reaction and conversion substantially which suggested that reaction was kinetically controlled.
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
100
80
60
40
20
0
0
20
40
60
80
100
120
Time (min)
Figure 12. Effect of temperature on conversion of vanillin: vanillin 0.02 mol, DMC 0.3 mol,
catalyst 2 wt % K La2O3ꢀMgO, speed of agitation 800 rpm, total volume 30 cm3, reaction time 2
h, catalyst loading 0.03 g/cm3. (♦) 140 ºC, (■) 150 ºC, (▲) 160 ºC, (x) 170 ºC
Reaction mechanism and mathematical model.
ACS Paragon Plus Environment
22

Page 23 of 34
Organic Process Research & Development
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Scheme 2. Reaction mechanism of Oꢀmethylation of vanillin with DMC
The plausible Oꢀmethylation mechanism of vanillin with DMC on basic sites of 2 wt % K/
La2O3ꢀMgO catalyst is depicted in Scheme 2. Oꢀmethylation of vanillin (A) with DMC (B)
occurs by strong adsorption of vanillin on basic sites leading to the formation of veratraldehyde.
The detail mathematical model was developed using LHHW mechanism as same reported in
recent literature.45,52 The detail derivation steps are provided in supplementary. The rate of
reaction of vanillin can be given as:
dCA
dt
dX A
dt
−rA = −
= CA
= kR wCA 1− X
C
(1)
(
)
A
B0
0
2
0
ACS Paragon Plus Environment
23

Organic Process Research & Development
Page 24 of 34
1
2
3
4
5
6
7
8
9
C >C
DMC was taken in molar excess over vanillin (
equation which can be integrated as follows:
−ln 1− X = k wt
A ), it becomes a pseudoꢀfirst order
B
0
0
(
)
A
1
(2)
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Where
is the pseudoꢀfirst order constant.
k1 = CBok
R2
A plot of ꢀln (1ꢀXA) against time was made at a various temperature to get excellent fit, there
by supporting the model. This is an overall pseudo first order reaction (Figure 13). Energy of
activation was calculated by plotting Arrhenius plot of ln k against time (Figure 14) and energy
of activation was found to be 13.5 kcal/mol, which supports the fact that reaction is intrinsically
kinetically controlled.
0.7
y = 0.024x
R² = 0.99
0.6
0.5
y = 0.0181x
R² = 0.99
0.4
y = 0.0128x
R² = 0.99
0.3
0.2
y = 0.0072x
R² = 0.99
0.1
0
0
5
10
15
20
25
30
35
Time (min)
Figure 13. Kinetics plots for various temperatures: vanillin 0.02 mol, DMC 0.3 mol, catalyst
2 wt % K/ La2O3ꢀMgO, speed of agitation 800 rpm, total volume 30 cm3, reaction time 2 h,
catalyst loading 0.03 g/cm3. (♦) 140 ºC, (■) 150 ºC, (▲) 160 ºC, (x) 170 ºC
ACS Paragon Plus Environment
24

Page 25 of 34
Organic Process Research & Development
1
2
3
4
5
6
7
8
9
-3
-3.5
-4
y = ꢀ6929.5x + 12.331
R² = 0.98
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
-4.5
-5
-5.5
0.0023
0.00235
0.0024
0.00245
0.0025
1/T (K-1)
Figure 14. Arrhenius plot
Reusability of catalyst
The reusability of the 2 wt % K/ La2O3ꢀMgO catalyst was tested four times in case of Oꢀ
methylation of vanillin. After each reaction, the catalyst was separated by filtration and washed
with methanol and then dried at 120 ºC. We have make up the catalyst during reaction. It was
observed that 2 wt % K/ La2O3ꢀMgO shows the very small difference in activity after third time
use. In case of fourth time reuse there is a 6 % conversion difference compare to fresh catalyst
(Figure 15). These results clearly show the stability of 2 wt % K/ La2O3ꢀMgO catalyst. Further,
we also characterized the used catalyst by different techniques and discussed above. The
morphology and the surface area analysis confirmed that there was no much difference in fresh
and used catalyst and hence the prepared catalyst was stable and reusable in the reaction.
ACS Paragon Plus Environment
25

Organic Process Research & Development
Page 26 of 34
1
2
3
4
5
6
7
8
9
Further, the hot filtration test was also conducted to study leaching of active sites, if any.
Reaction was stopped after 30 min and the catalyst filtered. The reactor was washed to get rid of
any traces of catalyst. The reaction was continued further for 2 h. The slight increase in
conversion was noticed from 41 to 43 % conversion which was an experimental error. This
confirmed the strong interaction between K2O and support i. e. La2O3ꢀMgO. As reported by
Noiroj et al.47 who claimed that nature or type of support plays an important role to prevent a
leaching of active species. In the current work La2O3ꢀMgO not only plays a role of base catalyst
but also acts as a good support to prevent leaching of potassium.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
100
80
60
40
20
0
Fresh
1st Reuse
2nd Reuse
3rd Reuse
4th Reuse
Figure 15. Catalyst reusability: vanillin 0.02 mol, DMC 0.3 mol, catalyst 2 wt % K/ La2O3ꢀ
MgO, speed of agitation 800 rpm, temperature 160 ºC, total volume 30 cm3, reaction time 2 h,
catalyst loading 0.03 g/cm3
Large-scale synthesis
From equation (2), the fractional conversion is theoretically given as follows:
ACS Paragon Plus Environment
26

Page 27 of 34
Organic Process Research & Development
1
2
3
4
X A = 1− e−k wt
1
(3)
5
6
7
8
9
The viability of the present method was also studied for a somewhat scaledꢀup experiment with
vanillin (21 g; 0.14 mol), DMC (176 g; 2.1 mol) and 1.4 mL of nꢀdecane as an internal standard
with optimized catalyst loading of 0.03g/cm3 (6.3 g)against a total volume (210 cm3) of the
liquid. The reaction mass heated at 160 °C with speed of agitation 800 rpm for 2 h. The reaction
was monitored. The conversion was 92 % in 2 h and the isolated yield 88 %. Also the fractional
conversion X A−experimental was plotted against X A− predicted value as given in Figure 16. The parity
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
plot shows that there is an excellent match. This experiment demonstrated the efficiency of the 2
wt % K/La2O3ꢀMgO for the largeꢀscale production as well.
1
0.8
0.6
0.4
0.2
0
0
0.2
0.4
0.6
0.8
1
XA predicted
Figure 16: Parity plot of experimental values against predicted values for a large scale
experiment.
CONCLUSION
ACS Paragon Plus Environment
27

Organic Process Research & Development
Page 28 of 34
1
2
3
4
5
6
7
8
9
Synthesis of veratraldehyde using a catalytic green process is desirable in today’s
environmentally conscious world. Therefore a new process was devised in this work using a
novel catalyst using mixed metal oxides. Different loadings of potassium promoted on La2O3ꢀ
MgO (1ꢀ4 wt %) catalysts were synthesized and characterized by various techniques. The
activity of catalyst was studied in the reaction of vanillin with DMC for the synthesis of
veratraldehyde in comparison with several other catalysts such as MgO, La2O3, La2O3ꢀMgO, 1
wt % K/ La2O3ꢀMgO, 2 wt % K/ La2O3ꢀMgO, 3 wt % K/ La2O3ꢀMgO and 4 wt % K/ La2O3ꢀ
MgO. Potassium promoted mixed oxides showed much higher catalytic activity than the
corresponding pure La2O3ꢀMgO mixed oxide, due to increase in moderate, strong, super basic
sites. Moreover, loading of potassium on La2O3ꢀMgO changes the structural properties like pore
volume and surface area, and it gives higher conversion towards the desired product. 2 wt % K/
La2O3ꢀMgO is the best and gives 96 % of conversion at mole ratio of 1:15 of vanillin to DMC
and 0.03 g/cm3 catalyst loading at 160 °C. By using this catalyst, we studied various parameters
systematically to establish kinetics. The catalyst is reusable up to four cycles. The energy of
activation for Oꢀmethylation of vanillin was found to be 13.5 kcal/mol. A scale up was also
attempted. Experimental and theoretical values matched very well. The process is green and
clean.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
ASSOCIATED CONTENTS
Supporting Information
Supporting information for this article contains catalyst characterization methodology and
development of kinetic model.
ACS Paragon Plus Environment
28

Page 29 of 34
Organic Process Research & Development
1
2
3
4
AUTHOR INFORMATION
5
6
7
Corresponding Author
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
*Ganapati D. Yadav. Eꢀmail: gd.yadav@ictmumbai.edu.in, Phone: +91ꢀ22ꢀ3361ꢀ1001, Fax:
+91ꢀ22ꢀ3361ꢀ1020; +91ꢀ22ꢀ3361ꢀ1002
NOTES
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
Jayaram Molleti acknowledges the support provided by University Grants Commission as
SRF. G.D. Yadav acknowledges support from R.T. Mody Distinguished Professor Endowment
and J.C. Bose National Fellowship of Department of Science and Technology, Govt. Of India.
NOMENCLATURE
A
reactant species, vanillin
reactant species, DMC
chemisorbed vanillin
B
AS
BS
C
chemisorbed DMC
product species C, veratraldehyde
vacant site
S
CA
concentration of vanillin in mol/cm3
ACS Paragon Plus Environment
29