Facile single step synthesis of an acid functionalized nano porous carbon composite as an efficient catalyst for tertiary butylation of phenol

Article abstract of DOI:10.1039/c4ra11190g

Here we report a simple synthesis method for the preparation of an acid functionalized nano porous nanocomposite of carbon for the first time from petroleum waste by a simultaneous carbonisation and sulfonation method. The material exhibited the highest ever reported catalytic activity towards liquid phase tertiary butylation of phenol up to several reaction cycles.

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DOI: 10.1039/C4RA11190G
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ARTICLE TYPE
Facile single step synthesis of acid functionalized nano porous carbon
composite as efficient catalyst for tertiary butylation of phenol †
ab
ab
Devaki Nandan and Nagabhatla Viswanadham *
DOI: 10.1039/b000000x
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Here we report a simple synthesis method for the preparation
of acid functionalized nano porous nano composite of carbon
for the first time from petroleum waste by a simultaneous
biodiesel synthesis. Bioꢀoil, produced from biomass via fast
pyrolysis also can be further processed for the production of fuels
and chemicals. Bioꢀchar, a byꢀproduct from this process has
carbonisation and sulfonation method. The material exhibited 60 proven to be a promising raw material for the production of
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highest ever reported catalytic activity towards liquid phase
tertiary butylation of phenol up to the several reaction cycles
activated carbons because of its availability at a low price . All
these studies indicate the importance and scope in using various
types of low value carbon sources for the production of
catalytically active carbon materials. Petroleum waste coal tar is
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The combinatorial approach of immobilizing homogenous
catalysts on to heterogeneous support has recently gained 65 another cheaper source material for this purpose as it is easily
importance to get the advantage of high Ka values of homogenous
catalysts and the easyꢀtoꢀseparate handling of the heterogeneous
catalysts. But, such catalysts suffer from leaching out problem of
weakly attached active sites on the support at the real reaction
conditions.
Acid functionalization of solid materials such as sulfonation of
active carbon and its composite materials is an interesting area of
origin that aims to take advantage of higher Ka values of liquid
acids and the nonꢀcorrosive, easyꢀtoꢀseparate property of solids
available and suitable for further treatments with acid for
obtaining functionalized carbon material for catalytic applications.
This way, the utilization of low cost fossil source provides an
economic and environment friendly process for high quality
70 material production.
The present study is aimed to explore the possible conversion
of petroleum waste into functionalized active carbon material. The
key factor in achieving high acidꢀbearing porous carbon material
lies in balancing the extent of carbonization and sulfonization
for catalytic applications. The methods such as sulfonation of 75 reactions. Generally, these materials are synthesized in two step
activated carbon resin and metallic oxide has come up to solve the
problem of acid density, but the procedure is time consuming and
procedure involving carbonization of the carbon source followed
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by its acid functionalization. The twoꢀstage method has the
drawback of obtaining highly carbonized material with less active
centres required for acid functionalization and less porosity.
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involves several preparation steps.
Moreover, the
immobilization of acidic functional group is difficult and also
yields low acid density. Further the usability of recyclable solid 80 Since, acidity and porosity are the two important functions
materials as replacement to homogeneous acid catalysts is usually
limited due to the low density and strength of the acid sites on the
solid surface.
essential for the catalytic activity, the applications of such
materials exhibited limitations in the studied reactions. Hence, the
challenge lies in the synthesis of functionalized carbon materials
is to create high density of acid sites along with porosity,
Carbon based solid sulfonic acid catalysts were first described
3
by Hara and coꢀworkers. In their work, a carbonꢀbased acid 85 especially in the range of nano pores.
catalyst composed of small polycyclic aromatic carbon sheets
Herein we report a simple oneꢀstep method for the synthesis of
with attached sulfonic acid groups (–SO H) was obtained by
a high acid bearing, nano porous carbon (NPC) nano material
facilitated by the simultaneous carbonization and sulfonation of
petroleum waste. The new class of this carbon material possessing
3
heating aromatic compounds (e.g., naphthalene) in concentrated
sulphuric acid. Lately, they employed glucose and sucrose as a
carbon precursor to prepare carbonꢀbased sulfonic acid catalysts 90 hydrophobic carbon moiety with hydrophilic ꢀSO H, ꢀOH and ꢀ
3
4
–6
and investigated their catalytic properties.
Composite
COOH groups with its high acidity and nano porous properties, is
not only suitable for further functionalization with acid or metal
ions but also expected to provide good mechanical and thermal
stability for catalytic applications. The material exhibited superior
sulfonated porous carbon materials were also synthesized and
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used as solid acid catalysts as well.
Recent studies using
sulfonated carbonꢀbased acid catalysts prepared from aromatic
hydrocarbons, carbohydrates and glycerol revealed that these are 95 catalytic performance in the bulky molecular tansformation of terꢀ
1
2ꢀ20
promising materials for the production of biodiesel.
Shu et
butylation of phenol in terms of higher conversion, higher
selectivity to 2ꢀ,4ꢀTBP and stability in the studied period of 4
reaction cycles. The catalytic activity observed here is highest
ever reported in the liquid phase reaction over functionalized
00 carbon materials.
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1
al. reported the use of inexpensive vegetable oil asphalt for the
preparation of a sulfonated carbonꢀbased catalyst useful for the
a
Academy of Scientific and Innovative Research (AcSIR) at CSIR-Indian
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Institute of Petroleum Dehradun-248005 (Uttarakhand), India
Herein we used petroleum waste coal tar as a cheaper and
green carbon precursor alternative to the commonly used high cost
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Refining Technology Division, Indian Institute of Petroleum, Council of
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resins, ionic surfactants and P123 block coꢀpolymers. In order to
avoid the limitations involved in functionalization of organic
05 moiety in two step partial carbonization and sulfonation methods
Scientific and Industrial Research, Dehradun-248005, Indi,. Fax: 91-135-
2
525702, Tel: 91-135-2525856, E-mail: nvish@iip.res.in
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†Electronic supplementary information (ESI) available: Experimental
details, XRD, EDX etc.
reported in known prior art,
herein we
adopted the
simultaneous carbonization and sulfonation method in a single
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DOI: 10.1039/C4RA11190G
step. The synthesis procedure is very simple that involves drop by
drop addition of sulphuric acid (55 gm) to 10 gm of coal tar
obtained from petroleum waste followed by its treatment at 100 ºC
for 24 h and then carbonization of the resultant mixture in
nitrogen atmosphere at 300 ºC to facilitate the decomposition and
transformation of the petroleum waste to hydrophobic carbon
residue bearing sulfonyl groups. The catalyst material was left for
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hours in boiling water followed by washing with cold water to
remove the weakly bound acid sites and carbon before using as a
catalyst.
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The wide angle XRD pattern (Fig. 1 ESI) of the sample shows
the ordered amorphous nature of the material. The morphology
and internal structure of the material analysed by SEM, TEM and
HRTEM images (Fig. 1) indicates the formation of porous carbon
matrix consists of interconnected nano particles of about 10 nm.
The HRTEM image of the material shows the nano porous
structure of the carbon with uniform pore size. The porous nature
of the material is further supported by N adsorption desorption
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isotherm (Fig 2A). The BJH pore size distribution of the sample
clearly shows that the major contributions of pores are between
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.7 to 2.6 nm (Fig 2B). The IR spectra of the sample (Fig. 3A)
ꢀ
1
shows broad band centred around 3,400 cm representing the OH
stretching along with peaks around 2929 cm and 2860 cm
related to C–H stretching vibrations. The other band appeared
around 1715 cm is due to ꢀC=O stretching and that of 1606 cm
is related to ꢀOH bending. The peaks related to ꢀSO H stretching
and O=S=O stretching are appeared at ꢀ1207 cm and 1040 cm
ꢀ
1
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ꢀ
1
ꢀ1
Fig. 1 A) SEM, B &C) TEM and D: HRTEM images of material.
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ꢀ
1
ꢀ1
respectively. Overall, the FTIR spectra indicate the presence of ꢀ
COOH, ꢀOH, ꢀSO H and ꢀCH groups in the material. The
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elemental analysis and EDX analysis of the material further
confirms the presence of carbon, oxygen and sulphur (ESI table
1
). The origin of phenolic ꢀOH and ꢀCOOH groups can be
attributed to the openꢀair synthesis procedure adopted during the
simultaneous carbonization and sulfonation of the material.
The acidity of the functionalized material determined by
acidꢀbase titration method (Table 1, ESI) indicates significantly
high acid loading occurred on the material (as high as 4.03 m
mol/g) by the sulfonation method adopted in the present study.
The composition analysis of the material described above
indicates the contribution of three functional groups responsible
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Figure 2 A) N adsorptionꢀdesorption isotherms and B) The BJH pore size
distribution of the material
for this acidity, namely, ꢀSO H, ꢀCOOH and ꢀOH. Among these,
3
the ꢀSO H is observed to contribute 1.43 mmol/g of acidity
3
(determined by CHNS and EDX analysis). Rest of the acidity (2.6
mmol/g) can be ascribed to the combined contribution of ꢀCOOH
and ꢀOH groups. Overall, the presence of ꢀSO H, ꢀCOOH and
3
phenolic –OH groups in the material are observed to be
responsible for the creation of significantly high acidity in the
carbon material. Further, the hydrophilic nature of these
functional groups on the material is also expected to contribute to
the chemical interaction with the hydrophilic reactant molecules
75
Fig. 3 A) FTIR and B) DT/TGA spectra of the material
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to facilitate the reaction in an effective manner.
butylation of phenol reaction involving hydrophilic reactants has
been studied in the present work as it is expected to be encouraged 80 raw materials in polymer industry. In general, the tertiary
The tertiary
The alkylated phenols are very good antioxidants and important
by the hydrophilic acid functional groups present on the acid
functionalized carbon moiety.
The thermal stability of the material was determined by TGA
analysis (Fig. 3B) which shows the initial weight loss at three
places; 1) about 7 % weight loss at 190 ºC 2) about 3 % weight 85 reactions.
loss between 190ꢀ282 ºC and 3) major weight loss of 30 % at
above 282 ºC that can be ascribed to the removal of
water/moisture, weekly stable carbon moiety and carbon material
respectively. The high moisture and water content possessed by
butylation of phenol is conventionally carried out in vapour phase
reaction at higher reaction temperatures (above 140 ºC) (Table 2
ESI†). However, the recent developments in novel materials
giving opportunity for low temperature liquid phase catalytic
24ꢀ26
The material synthesized in the present study
exhibiting strong acidity is expected to be suitable for catalytic
applications involving alkylation reaction and the material is
tested for its performance in liquid phase butylation of phenol. We
have applied the synthesized material for solvent free liquid phase
the material can be ascribed to the presence of various hydrophilic 90 reaction in Parr reactor at 130 ºC for 5 h. The studies indeed
groups. The TGA/DT analysis indicates that the material is stable
up to 282 ºC and is suitable for catalytic applications.
indicated the promising catalytic functionality of the synthesized
material,
2
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DOI: 10.1039/C4RA11190G
a
Table 1 Catalytic performance of the NPC material
functionalized carbon materials to the best of our knowledge.
Moreover, the active material does not suffer from leaching
problems and can be efficiently reused in consecutive catalytic
cycles.
SN RT
h)
Conversion
of phenol
Selectivity to alkylation products ( wt% )
(
(
wt% )
2
ꢀTBP 4ꢀTBP 2,4ꢀDTBP Unidentified
1
2
3
4
5
5
5
5
85.0
84.0
84.5
83.0
14.5
14.0
13.5
14.5
14.0
64.4
62.0
63.0
65.0
7.1
7.5
6.5
6.0
60
We acknowledge the CSIR for the research funding of the
project under 12 FYP. Authors are thankful to the director, IIP,
for his encouragement. DN thankful to CSIR, New Delhi, for
awarding senior research fellowship and Deepak Rohilla for
helping in reaction studies. We are thankful to XRD, IR and SEM,
groups at IIP for analysis.
Th
17.0
16.0
15.0
a
Catalyst: 0.5 g (5 wt. % of Phenol+TBA), Reaction temperature:
ο
1
30 C, pressure: 1 bar N
molar ratio).
2
; reaction time: 5 h; Phenol/ TBA = 1 : 2.5
65
(
where, the catalyst exhibited as high as 85% conversion based on
phenol (>97% conversion based on alcohol) with product
selectivity of 64.5%, 14.5% and 14% to 2,4ꢀditertiary butyl
phenol (2,4ꢀDTBP), 4ꢀtertiry butyl phenol (4ꢀTBP) and 2ꢀtertiary
butyl phenol (2ꢀTBP) respectively (Table 1 ). The results indicate
higher conversion, higher selectivity to bulky 2, 4ꢀDTBP product
and better performance in terms of low temperature operation and
reaction times of the present catalyst when compared to the
reported results (Table 2&3 ESI†). The higher performance of the
catalyst observed in the present study can be ascribed to the high
acid density of the nano porous carbon material obtained in the
single step carbonization and functionalization adopted during the
synthesis. The present material also exhibited much higher
Notes and reference
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M. Toda, A. Takagaki, M. Okamura, J. N. Kondo, S. Hayashi, K.
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5 M. Kitano, D. Yamaguchi, S. Satoshi, K. Nakajima, H. Kato, S.
Hayashi and M. Hara, Langmuir, 2009, 25, 5068.
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S. Suganuma, K. Nakajima, M. Kitano, D. Yamaguchi, H. Kato, S.
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catalytic activity when compared to the –SO H containing
3
8
9
P. Gupta and S. Paul, Green Chem., 2011, 13, 2365.
K. Komura, Y. Nakano and M. Koketsu, Green Chem., 2011, 13, 828.
supports reported in the literature (Table 2&3 ESI). This may be
due to the coꢀpresence of the hydrophilic –COOH and phenolic –
OH groups in the material of the present study that is expected to
play an important role in promoting the effective interaction
between hydrophilic reactants and the active sites of the catalyst.
10 S. Van de Vyver, L. Peng, J. Geboers, H. Schepers, F. de clippel, C. J.
Gommes, B. goderis, P. A. Jacobs and B. F. Sels, Green Chem., 2010,
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2
Thus the presence of acidic SO H groups along with hydrophilic
3
groups (ꢀCOOH & ꢀOH) present in hydrophobic carbon of present
study provides a beneficial factor for the development of the
catalytic process for alkylation reactions, and the catalyst also
exhibits constant phenol conversion up to the 4 reaction cycles
90
14X. H. Mo, E. Lotero, C. Q. Lu, Catal. Lett., 2008, 123, 1.
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spent catalyst with ethanol and drying at 120 ºC between
consecutive reaction cycles.
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1
6J. A. MaciáꢀAgulló, M. Sevilla, M. A. Diez, A. B. Fuertes,
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In conclusion, we have demonstrated a facile and single step
synthesis method for the preparation of high acidic nano porous
carbon material through simultaneous carbonization and
sulfonation of petroleum waste. The method is cheaper and
produces thermally stable material suitable for catalytic
applications involving bulky organic transformations. Here we
have achieved as high as 4.03 mm/g acidity responsible for as
high as 85% phenol conversion in the alkylation reaction. The
porous nature of the material also reflected in the production of
high amount of bulky 2,4ꢀDTBP (65%). The phenol conversion
and the selectivity towards 2,4ꢀDTBP on the present catalyst
system are observed to be highest ever reported on the
1
1
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