Available online at www.sciencedirect.com
Biomass and Bioenergy 26 (2004) 473 – 483
The use of catalytic hydrogenation to intercept carbohydrates in
a dilute acid hydrolysis of biomass to eect a clean separation
from lignin
J. Michael Robinson
a;∗
, Caroline E. Burgess
b
, Melissa A. Bently
a
, Chris D. Brasher
a
,
Bruce O. Horne
a
, Danny M. Lillard
a
, JosÃe M. Macias
a
, Hari D. Mandal
a
,
Samuel C. Mills
a
, Kevin D. O’Hara
a
, Justin T. Pon
a
, Annette F. Raigoza
a
,
Ernesto H. Sanchez
a
, JosÃe S. Villarreal
a
a
The University of Texas of the Permian Basin, Chemistry Department, 4901 E. University Blvd., Odessa, TX79762, USA
b
Energy Institute, 209 Academic Projects Bldg., Penn State University, University Park, PA 16802, USA
Received 21 April 2003; received in revised form 3 September 2003; accepted 3 September 2003
Abstract
Biomass carbohydrates are fractionated very cleanly (¿ 99%) from unreacted insoluble lignin by a dilute acid hydrolysis
(0.35–1.5% H
3
PO
4
), wherein the incipient aldoses are intercepted by catalytic hydrogenation (Ru/C) to produce a solution
of C
5
–C
6
polyols (xylitol, sorbitol) and anhydro polyols (sorbitan) in which no phenols could be detected (¡ 100 ppm). A
screen removes granular catalyst and lignin is simply ÿltered from the product slurry. This “intercepted dilute acid hydrolysis”
(IDAH) of biomass to polyols aords high conversion for a variety of biomass types within 3–6 h at ∼ 185
◦
C. Minimum
polyols cost (not including catalyst cost) is calculated to range from $0.055 –$0:070 kg
−1
. Polyols, rather than aldoses, are
required for subsequent chemical conversion into hydrocarbon fuels.
? 2003 Elsevier Ltd. All rights reserved.
Keywords: Biomass; Carbohydrate; Dilute acid hydrolysis; Catalytic hydrogenation; Polyol; Xylitol; Sorbitol; Sorbitan; Fuel; Cost
1. Introduction
Obtaining a clean fractionation [1] of biomass
polysaccharides has been a dicult task. Ultimately,
utilization of biomass to produce liquid fuels econom-
ically must solve this challenge. Many government
agencies [2], national labs [3], industry [4,5] and
∗
Corresponding author. Tel.: +1-432-552-2237;
fax: +1-432-552-2236.
E-mail address: robinson
m@utpb.edu (J. Michael Robinson).
academia [6–8] have attempted to solve this prob-
lem by almost as many methods and improvements.
The reactive nature of the monomeric carbohydrates
generated in situ unfortunately provides for contin-
ued reactions (degradation). The rate of digestion of
polysaccharides and the rate of undesirable side reac-
tions of aldoses have to be delicately balanced in order
to achieve a reasonable yield.
Herein, a strategy is deÿned which provides for
trapping the reactive carbonyl carbohydrates as they
are hydrolyzed from biomass polysaccharides. Incipi-
ent aldoses are rapidly hydrogenated to almost 100%
0961-9534/$ - see front matter ? 2003 Elsevier Ltd. All rights reserved.
doi:10.1016/j.biombioe.2003.09.005