G Model
MOLCAA-9694; No. of Pages7
ARTICLE IN PRESS
C.J.A. Mota et al. / Journal of Molecular Catalysis A: Chemical xxx (2015) xxx–xxx
2
Scheme 3. Hydrogenolysis of glycerol to propene.
Hence, a technological route to propene from glycerol, relying on
sustainable metal catalysts, can be of great relevance for developing
a biorefinery process based on oils and fats.
Scheme 1. Main industrial routes to propene from fossil sources (oil, coal and nat-
ural gas).
2. Experimental
Biodiesel is an important biofuel used mainly in Europe and
South America. In Brazil, there is a mandatory blend of 7% biodiesel
in the regular diesel and an increase in this percentage is being
considered for the next years. The transesterification of oils and
fats is the main industrial process for the production of biodiesel
The catalysts were prepared by successive impregnation of the
metals over an activated carbon (AC) support. Initially, molyb-
denum was impregnated by a slurry method [19]. About 10 g of
activated carbon were placed in a 250 mL Erlenmeyer and 1.5 g
(10.6 mmol) of MoO3 were mixed together with 100 mL of deion-
ized water. The system was kept stirring at room temperature for
[
6]. It involves the reaction of a triglyceride with excess methanol,
◦
in the presence of a basic catalysts, to afford three molecules of
fatty acid methyl esters, the biodiesel, and a molecule of glycerol,
which accounts approximately to 10 wt% of the total mass of the
system (Scheme 2). The use of glycerol as a renewable feedstock
in biorefinery processes has motivated many studies in the recent
years [7–10]. Hydrogenolysis of glycerol is one of the main stud-
ied processes. Different metal catalysts can be used, with 1,2 and
24 h and then, the water was evaporated at 70 C under reduced
pressure. In the sequence, a specific mass of Ni(NO3)2·6H2O, Zn
(NO3) 2·6H2O, Cu(NO3)2·3H2O or Fe (NO3)3·9H2O, corresponding to
6.93 mmol of the metals, were dissolved in the minimum amount
of deionized water and put in contact with the solid obtained upon
the Mo impregnation of the AC. Then, a solution of about 150 mL of
30 wt% ammonium hydroxide were added dropwise to precipitate
the metal hydroxide. At the end, the system was stirred at room
temperature for 24 h and then subjected to water evaporation at
1
,3-propanediols being the main target products [11–13]. Some
studies reported that, at more severe conditions, isopropanol and
n-propanol could also be observed [14,15]. This fact could open a
possibility of developing a glycerol to propene route, because dehy-
dration of propanols over acidic catalysts would afford propene as
major product.
◦
◦
70 C and reduced pressure. The final solid was calcined at 450 C
◦
−1
for 2 h (rate of 10 C min ). The atomic ratio of the catalysts were
0.4 considering the amount of the metal divided by the amount of
the metal plus Mo.
Aiming to develop a technological route to produce propene
from renewable raw materials, we have began an extensive study
on glycerol hydrogenolysis, which ultimately led to the develop-
ment of bimetallic catalysts for the selective production of propene.
The initial results were published on the patent literature [17,18].
Thereafter, Yu et al. reported a selective glycerol hydrogenolysis to
n-propanol over Iridium supported catalysts. The coupling of this
metal catalyst with acidic ZSM-5 zeolite may provide a technologi-
cal route to produce propene from glycerol, in high conversion and
selectivity [16]. Nevertheless, Iridium is considered an endangered
element and faces serious threat, due to limited availability and
increasing use. In addition, the process is carried out in two steps,
using two different catalysts, which may increase the operational
costs. Thus, the development of an Ir-based catalyst may not be
economically and environmentally feasible for the production of
green propene, a major chemical commodity.
The catalysts were characterized by temperature programmed
reduction (TPR), X-ray diffraction (XRD), N2 physisorption and acid-
ity, which was measured by n-butylamine termodesorption (TPD),
according to a previous publish method [20]. The chemical compo-
sition was measured by X-ray fluorescence (FRX).
The catalysts were evaluated in a fixed bed flow unit at
atmospheric pressure. The catalysts were initially reduced on
−
1
◦
◦
−1
40 mL min
of H2 at 550 C for 30 min (rate of 10 C min ).
◦
Then, the temperature was decreased to 300 C and a solution
of 90 vol% of glycerol in water was introduced into the H2 gas
flow (40 mL min ) by means of a syringe pump. The weight hour
−
1
−
1
space velocity (WHSV) in relation to the glycerol was 5.4 h
in
many experiments. The products were analyzed by on-line capil-
lary gas chromatography equipped with a methyl silicone column
(100m × 0.15 mm × 0.5 m) using a flame ionization detector.
Commercial Pd and Ru supported catalysts were also tested in
the hydrogenolysis of glycerol. These catalysts were kindly pro-
vided by Evonik and have 5 wt% of the metal supported over
activated carbon.
Here, we report the original history behind the development of
the iron/molybdenum-based catalyst for the selective hydrogenol-
ysis of glycerol to propene, as reported in the previous patents
[
17,18] (Scheme 3). Molybdenum is highly used in oil refining, as
a major component of hydrotreating catalyst to remove sulfur and
nitrogen from diesel and kerosene, but there is no serious danger
of supply of this element in the forthcoming years. Iron is the main
catalyst for ammonia production and highly abundant on Earth.
3. Results
We began the studies toward a selective process of glycerol
hydrogenolysis to propene using the commercial Ru and Pd cat-
Scheme 2. Transesterification of triglycerides to produce biodiesel and glycerol.
Mota, Claudio J.A.
