20
L. Nie, D.E. Resasco / Applied Catalysis A: General 447–448 (2012) 14–21
Table 3
(b) Cu/SiO2 and Pt–Fe/SiO2 are effective hydrogenation catalysts of
short aldehydes and ketones, respectively that can achieve sig-
nificant yields of the desired alcohols without converting the
aromatic ring of the phenolic compound. Using such selective
hydrogenation catalysts allows the implementation of two-bed
reactors, which might be an efficient way of combining hydro-
genation and alkylation reaction.
(c) H-Beta is an effective catalyst for the alkylation of m-cresol,
yielding ortho- and para- substituted alkylates (2I5MP and
4I3MP) as primary products. The meta-substituted product
(3I5MP) is formed by secondary isomerization of 2I5MP and
4I3MP.
Product distribution (% mol) for different feed and different catalysts. Carrier gas H2
60 ml/min. 200 ◦C. TOS = 15 min. Feed rate 0.2 ml/h.
Two beds
One bed
HBeta
Catalyst
100 mg Pt–Fe/SiO2
+ HBeta
Feed
Acetone
+ m-Cresol 4:1 (molar)
Acetone + 2-propanol
+ m-Cresol (2:2:1)
HBeta weight (mg)
30
60
60
Propylene
Acetone
m-Cresol
Alklate
2I5MP (thymol)
3I5MP
4I3MP
13.4
65.4
20.1
11.4
62.4
24.2
32.9
39.1
25.4
(d) Over H-Beta zeolite, the optimum reaction temperature for the
alkylation of meta-cresol is 200 ◦C, since higher temperatures
result in a more severe deactivation of the catalyst.
1.07
–
–
2.01
–
–
1.82
0.31
0.39
(e) Dehydration is a fast reaction compared to alkylation over the
H-Beta zeolite. Therefore, the dehydration product, propylene,
is the true alkylating agent. The dehydration of 1-propanol
is much slower than that of 2-propanol and so, at low W/F,
dipropyl ether is the dominant product when 1-propanol is
used as a feed. With 2-propanol as a feed, the highest alkyl-
ation yield is obtained due to the fast dehydration as well as the
evolution of concomitant amount of water that inhibits catalyst
deactivation.
m-Cresol conversion (%)
5.0
7.6
9.1
60
50
40
30
20
10
0
2-propanol + m-cresol 2:1 (molar)
Acknowledgments
Support
from
the
National
Science
Foundation
(EPSCoR0814361), US Department of Energy (DE-FG36GO88064),
Oklahoma Secretary of Energy and the Oklahoma Bioenergy Center
are greatly appreciated. The authors thank Drs. Trung T. Pham and
Xinli Zhu for their constructive suggestions.
2-propanol + acetone + m-cresol 2:2:1 (molar)
0
20
40
60
80
100
120
References
TOS/min
[1] S. Czernik, A.V. Bridgwater, Energy Fuels 18 (2004) 590–598.
[2] J.P. Diebold, A Review of the Chemical and Physical Mechanisms of the Storage
Stability of Fast Pyrolysis Bio-Oils, 2000, NREL/SR-570-27613.
[3] D. Mohan, C.U.P. Pittman Jr., P.H. Steele, Energy Fuels 20 (2006) 848–889.
[4] A.G. Gayubo, B. Valle, A.T. Aguayo, M. Olazar, J. Bilbao, J. Chem. Technol. Bio-
technol. 85 (2010) 132–144.
[5] C.A. Fisk, T. Morgan, Y. Ji, M. Crocker, C. Crofcheck, S.A. Lewis, Appl. Catal. A 358
[6] X. Yang, S. Chatterjee, Z. Zhang, X. Zhu, C.U. Pittman Jr., Ind. Eng. Chem. Res. 49
(2010) 2003–2013.
[7] T.Q. Hoang, X. Zhu, T. Sooknoi, D.E. Resasco, R.G. Mallinson, J. Catal. 271 (2010)
201–208.
[8] G.W. Huber (Ed.), Breaking the Chemical and Engineering Barriers to Lignocel-
lulosic Biofuels: Next Generation Hydrocarbon Biorefineries, National Science
Foundation, Washington, DC, 2008, 180 p.
[9] D.C. Elliott, Energy Fuels 21 (2007) 1792–1815.
[10] A. Gangadharan, M. Shen, T. Sooknoi, D.E. Resasco, R.G. Mallinson, Appl. Catal.
A 385 (2010) 80–91.
[11] X. Zhu, L.L. Lobban, R.G. Mallinson, D.E. Resasco, J. Catal. 281 (2011) 21–29.
[12] T.Q. Hoang, X. Zhu, L.L. Lobban, D.E. Resasco, R.G. Mallinson, Catal. Commun.
11 (2010) 977–981.
Fig. 11. Conversion of m-cresol with and without cofeeding acetone. W/F = 0.3 h.
Carrier gas H2 60 ml/min. H-Beta catalyst, 200 ◦C.
relatively low alkylation conversions compared to those obtained
with 2-propanol, indicate that the presence of unconverted ace-
tone suppresses the alkylation reaction, probably via adsorption
competition over the acid sites. To quantify the inhibiting effect
of acetone a separate experiment with a mixed feed over H-Beta
was conducted in the one-bed reactor. Here again, the inhibition
by acetone is clearly apparent. Furthermore, as shown in Fig. 11
when the alkylation of m-cresol is compared in the absence and
presence of acetone, the activity is seen to drop by more than a
factor of 4. An important conclusion from this result is that when a
sequential strategy is followed, a full hydrogenation of the carbonyl
compounds to alcohols is needed in order to preserve the alkylation
reaction.
[13] F. Masaki, I. Hakuai, Chem. Lett. 6 (1987) 1205–1208.
[14] J. Bedia, R. Ruiz-Rosas, J. Rodríguez-Mirasol, T. Cordero, J. Catal. 271 (2010)
33–42.
[15] A.V. Krishnan, K.Keka Ojha, N.Narayan C. Pradhan, Org. Process Res. Dev. 6
(2002) 132–137.
4. Conclusions
The following conclusions are drawn from this study:
[16] M. Selvaraj, S. Kawi, Microporous Mesoporous Mater. 109 (2008) 458–469.
[17] M. Selvaraj, P.K. Sinha, J. Mol. Catal. A 264 (2007) 44–49.
[18] C.T. O’Connor, G. Moon, W. Böhringer, J.C.Q. Fletcher, Collect. Czech. Chem.
Commun. 68 (2003) 1949–1968.
[19] T.T. Pham, L.L. Lobban, D.E. Resasco, R.G. Mallinson, J. Catal. 266 (2009) 9–14.
[20] J. Bedia, R. Ruiz-Rosas, J. Rodriguez-Mirasol, T. Cordero, J. Catal. 271 (2010)
33–42.
[21] G.C. Laredo, J. Castillo, H. Armendariz-Herrera, Appl. Catal. A: Gen. 384 (2010)
115–121.
[22] G. Girotti, F. Rivetti, S. Ramello, L. Carnelli, J. Mol. Catal. A 204–205 (2003)
571–579.
(a) One can envision a combined upgrading strategy of two bio-
oil fractions, one rich in small oxygenates and the other rich in
phenolics as follows. The carbonyl compounds are first selec-
tively hydrogenated to alcohols on a metal catalyst that leaves
the aromatic rings unconverted; then the corresponding alco-
hols can alkylate the phenolic compounds on an acidic zeolite.
The coupled deoxygenation and alkylation can be achieved at
relatively low temperatures (e.g. 200 ◦C).
[23] G. Kostrab, M. Lovic, I. Janotka, M. Bajus, D. Mravec, Appl. Catal. A 323 (2007)
210–218.