catalysts

Article
Bio-Oil Steam Reforming over a Mining Residue
Functionalized with Ni as Catalyst: Ni-UGSO
Amine Bali, Jasmin Blanchard, Mostafa Chamoumi and Nicolas Abatzoglou * ID

Department of Chemical Engineering and Biotechnological Engineering, Université de Sherbrooke, 2500,

Boulevard de l’Université, Sherbrooke, QC J1K 2R1, Canada; Amine.Bali@usherbrooke.ca (A.B.);
Jasmin.Blanchard@usherbrooke.ca (J.B.); Mostafa.Chamoumi@usherbrooke.ca (M.C.)
* Corresponding author: Nicolas.Abatzoglou@usherbrooke.ca; Tel.: +1-819-821-7904

Received: 17 November 2017; Accepted: 15 December 2017; Published: 22 December 2017

Abstract: Bio-oil reforming is considered for syngas or H2 production. In this work, we studied the
steam reforming (SR) of two raw bio-oils without adding external steam, using a recently-developed
catalyst, Ni-UGSO. Experiments were performed at temperature (T) = 750–850 ◦ C and weight hourly
space velocity (WHSV) = 1.7–7.1 g/gcat /h to assess C conversion (XC ) and product yields. The results
show that, in all conditions and with both bio-oils tested, the catalyst is stable for the entire duration
of the tests (~500 min) even when some C deposition occurred and that only at the highest WHSV
tested there is a slight deactivation. In all tests, catalytic activity remained constant after a first,
short, transient state, which corresponded to catalyst activation. The highest yields and conversions,
with YH2 , YCO and XC of 94%, 84% and 100%, respectively, were observed at temperatures above
800 ◦ C and WHSV = 1.7 g/gcat /h. The amount of H2 O in the bio-oils had a non-negligible effect on
catalyst activity, impacting YH2 , YCO and XC values. It was observed that, above a critical amount
of H2 O, the catalyst was not fully activated. However, higher H2 O content led to the reduction of
C deposits as well as lower YH2 and YCO and, through the water-gas-shift reaction, to higher YCO2
(CO2 selectivity). Fresh and spent catalysts were analyzed by physisorption (BET), X-ray diffraction,
scanning electron microscopy and thermogravimetric analysis: the results reveal that, during the
oils’ SR reaction, the initial spinel (Ni-Fe-Mg-Al) structures decreased over time-on-stream (TOS),
while metallic Ni, Fe and their alloy phases appeared. Although significant sintering was observed
in used catalysts, especially at high H2 O/C ratio, the catalyst’s specific surface generally increased;
the latter was attributed to the presence of nanometric metallic Ni and Ni-Fe alloy particles formed
by reduction reactions. A small amount of C (4%) was formed at low H2 O/C.

Keywords: bio-oil; catalysis; steam reforming; mining residue; nickel catalyst; spinel; hydrogen; syngas

1. Introduction
Biomass is a renewable energy resource. It can be combusted to provide heat, gasified to produce
syngas, torrefied to yield biochar or undergo pyrolysis to generate bio-oils (or pyrolysis oils) [1].
Bio-oils are complex mixtures of various hydrocarbons and oxygenated compounds: H2 O, ketones,
aldehydes, acids and sugars [2]. They may have many applications as: fuel for burners [3] or engines [4],
transportation fuels after upgrading [5] or feedstock for producing chemicals and syngas [6]. In the
latter two cases, such applications are difficult to implement due to the unfavorable physico-chemical
properties of bio-oils. Indeed, they are viscous; have high O and H2 O content; have low heating
value (<20 MJ/kg); and have high acidity. They are unstable so they age relatively rapidly and
phase-separate upon storage [7]. However, this latter issue can be prevented by including additives
such as methanol [7,8]. Because of mixture complexity, it is technically difficult and expensive to isolate
chemicals with available separation processes.

Catalysts 2018, 8, 1; doi:10.3390/catal8010001 www.mdpi.com/journal/catalysts

Catalysts 2018, 8, 1 2 of 24

The main advantage of bio-oils is that they are liquid [9], and easy to store and transport.
These attributes have led the National Renewable Energy Laboratory (NREL) in the USA to work on the
concept of distributed H2 production by bio-oil catalytic reforming [9–12], which is currently a promising
options for bio-oil use. Other work has been done in collaboration with the NREL—transportation
fuel production from bio-oils via bio-oil hydroprocessing—where the H2 needed is produced by the
catalytic reforming of 38 wt % of feedstock [13].
The targeted reaction is Equation (1):
 y
Cx Hy Oz + ( x − z)H2 O ↔ xCO + x − z + H2 (1)
2
Side reactions also take place in the reactor: water-gas-shift (WGS) (Equation (2)), Boudouard
equilibrium (Equation (3)) and thermal cracking (Equation (4)):

CO + H2 O ↔ CO2 + H2 (2)

C + CO2 ↔ 2CO (3)

C x Hy Oz → C + C a Hb + Ce H f O g (4)

where Ca Hb designates light hydrocarbons, such as: CH4 , C2 H6 and C2 H4 , while Ce H f Og represents
light oxygenated compounds, such as acetone, ethanol, and methanol.
To increase H2 yield, a WGS reactor is commonly added next to the reforming unit [9], and H2 is
purified through a pressure swing adsorption (PSA) unit.
Bio-oil steam reforming (SR) was studied in the 1990s at the NREL: Wang et al. [10,14] investigated
H2 production from bio-oils, using commercial Ni-based catalysts. The same group studied catalytic
reforming of bio-oil aqueous fractions over a variety of commercial and research-based Ni catalysts [15].
The commercial catalysts performed better while La2 O3 and MgO addition to classical Ni/Al2 O3
enhanced steam adsorption and facilitated C gasification. Moreover, they showed that addition
through impregnation of metallic Cr and Co reduced Ni crystallite size, which proved beneficial in
terms of catalytic efficiency and resistance to coke deposition. Later on, NREL researchers studied
different routes of H2 production from bio-oils: (a) catalytic SR [11], partial oxidation (POX) [16],
and autothermal reforming (ATR) [9]; and (b) non-catalytic POX [17]. Different reactor configurations
(fixed bed, fluidized bed, and staged reactor) as well as different catalysts were tested. POX and ATR
have the advantage of being much less energy-intensive and, consequently, more economical processes,
but their H2 yields are generally lower.
Other groups also worked on bio-oil reforming. Hu and Lu [18] developed an original “Y”
reactor for mixed SR and dry reforming of bio-oils over two catalyst beds aimed at increasing
CO2 conversion or CO2 selectivity (expressed in an equivalent way). The catalysts used we
Ni/Al2 O3 and Ni/La2 O3 . Xie et al. [19] studied bio-oil SR enhanced by CO2 sorption with CaO
over Ni-Ce/Co-Al2 O3 catalyst: they compared three precursors of the sorbent CaO and confirmed
that at least partial removal of CO2 improved H2 yield because the WGS reaction was, thus, favored.
Seyedeyn-Azad et al. [20] worked on SR of the aqueous fraction of bio-oil over Ni-MgO/Al2 O3 catalyst;
they assessed the effect of bio-oil/H2 O ratio, Ni loading and catalyst preparation conditions on H2
yield; the maximum H2 yield obtained was 61%. Gao et al. [21] have studied the SR of raw bio-oil
over the nano-Ni/ceramic foam catalyst; they assessed the effect of: reaction temperature (TR ), WHSV
and catalyst calcination temperature (Tcal ) on products composition and yield; the highest H2 yield
was obtained at Tcal = 400 ◦ C, TR = 700 ◦ C and WHSV = 1.4 h−1 . Similar work was conducted by
Quan et al. [22] on the SR of coconut shell bio-oil over Fe/olivine catalyst; the latter was suitable for the
conversion of most of the phenolic compounds. The authors also show that a Tcal > 900 ◦ C could lead
to catalyst deactivation and Fe sintering. Remón et al. [23] studied the SR of various bio-oils aqueous
fraction over Ni-Co/Al-Mg catalyst; they evaluated the effect of the liquids compositions on products
yield and found that acetic acid and furfural content had the greatest impact on reforming results.
Catalysts 2018, 8, 1 3 of 24

Many works on SR of bio-oil model compounds have been published. Vagia and Lemonidou [24,25]
performed thermodynamic analysis of SR and autothermal SR of simulated bio-oils with oxygenated
compounds (acetic acid, ethylene glycol and acetone) where the effects of temperature, H2 O/C ratio
and pressure on product composition and yield were evaluated. González-Gil et al. [26] studied
the catalytic SR of representative molecules (acetone and ethanol) of bio-oil aqueous fractions: they
demonstrated that the addition of Rh on Ni/Al2 O3 improved H2 selectivity. Trane-Restrup and
Jensen [27] investigated SR and the oxidative SR (OSR) of three cyclic model compounds, guaïacol,
furfural and 2-methylfuran, at various temperatures over Ni/CeO2 -K/MgAl2 O4 . The catalyst was
active during 4 h but significant C deposition was observed, mostly in the case of guaïacol SR. OSR led
to less C deposition but at the expense of H2 yield.
Generally, catalysts used in SR are Ni-based because of their high activity and low cost. However,
they deactivate relatively quickly owing to C deposition and sintering. Noble metals, such as Rh, Ru,
Pt and Pd, are also employed and display better resistance to deactivation for comparable activity
with Ni but they are much more expensive [28]. To improve the resilience of Ni catalysts to C deposits,
promotors like alkali metals are used as they enhance steam adsorption [29]. S passivation, or the
addition of a noble metal, such as Au, reduces the rate of C deposits considerably by blocking the
step sites [30]. Navarro et al. [31] reported that the addition of Pt enhances acetone gasification by
increasing the reducibility and surface exposure of metallic Ni. Catalyst supports, such as hydrotalcite,
favor the presence of small Ni particles compared to NiO/α-Al2 O3 and NiO/CaO-Al2 O3 catalysts [32]:
the smaller the particles, the lower the C deposits. Spinel type catalysts such as NiAl2 O4 /Al2 O3 -YSZ
have been reported to be effective for liquid hydrocarbon SR with high resistance to C deposits [33–35].
In this study, we assessed the SR of two different raw bio-oils (named MemU and WU) without
adding external steam over a new patent-pending Ni-based spinel catalyst made from the mining
residue UGSO [36]. The catalyst, named Ni-UGSO, has already demonstrated high activity and
resilience in methane SR and dry reforming [37,38].

2. Results and Discussion

2.1. Bio-Oil Properties

Table 1 reports measured properties of the two bio-oils. These two oils behaved differently;
the difference was attributed mainly to H2 O content. Indeed, H2 O content has a significant impact on
SR and on catalyst morphology. In this study, molar H2 O/C ratio was low (0.6 for MemU and 1.85 for
WU) compared to other studies (2 < H2 O/C < 10) where external steam was added [17,19,39] or the
bio-oil aqueous fraction was used [16,24]. Nevertheless, our results were comparable or even better in
terms of yields, selectivity and catalyst resistance to coke deposition. These points are detailed below.

Table 1. Bio-oil properties.

Properties Bio-Oil MemU Bio-Oil WU

Density 1.187 1.087
%C* 39.4 18.8
%H* 7.0 7.9
%O* 53.6 73.3
% H2 O * 34.3 52.3
pH 2.4 2.9
H2 O/C ** 0.60 1.85
O/C ** 1.02 2.92
* Weight percentages; ** Molar ratios.

2.2. Steam Reforming Results

The SR results of the two bio-oils appear in Figures 1 and 2. They showed that:
Catalysts 2018, 8, 1 4 of 25

Catalysts
2.2. Steam2018, 8, 1
Reforming Results 4 of 24

The SR results of the two bio-oils appear in Figures 1 and 2. They showed that:
• Increased temperature evoked higher C conversion (XC ), CO and H2 yields (YCO , YH2 ) for both
 Increased temperature evoked higher C conversion (XC), CO and H2 yields ( , ) for both
bio-oils. This was in agreement with the thermodynamic analysis of bio-oil model compounds
bio-oils. This was in agreement with the thermodynamic analysis of bio-oil model compounds
studied by many authors [20,23,40] where it is found that the reaction is endothermic. The decrease
studied by many authors [20,23,40] where it is found that the reaction is endothermic. The
in XC , YCO and YH2 at 850 ◦ C in Figure 1B is an outlier; we attribute that to experimental errors,
decrease in XC, and at 850 °C in Figure 1B is an outlier; we attribute that to experimental
which led to higher error in the mass balance than the average.
errors, which led to higher error in the mass balance than the average.
• CO and H2 were favored at low WHSV because of increased residence time over the catalyst
 CO and H2 were favored at low WHSV because of increased residence time over the catalyst
bed. In the MemU bio-oil (Figure 3), we observe a decrease of CO2 . A higher CO, H2 production
bed. In the MemU bio-oil (Figure 3), we observe a decrease of CO2. A higher CO, H2 production
through reforming means that there is a higher H2 O consumption. If the increase of CO and H2
through reforming means that there is a higher H2O consumption. If the increase of CO and H2
is equal, the WGS reaction (CO + H2 O = CO2 + H2 ) will shift in such a way to compensate the
is equal, the WGS reaction (CO + H2O = CO2 + H2) will shift in such a way to compensate the H2O
H2 O decrease; this means that the CO2 will decrease. This is the case for the MemU oil whose
decrease; this means that the CO2 will decrease. This is the case for the MemU oil whose H2O/C
H2 O/C is low; thus, the consumption of H2 O by the reforming reaction has a higher impact on
is low; thus, the consumption of H2O by the reforming reaction has a higher impact on WGS. In
WGS. In the case of WU, we do not observe this behavior because the H2 O/C is much higher.
the case of WU, we do not observe this behavior because the H2O/C is much higher.
• The amount of H2 O and O in the two bio-oils had a significant impact on SR performance.
 The amount of H2O and O in the two bio-oils had a significant impact on SR performance.
Comparison of bio-oil MemU (Figure 1) and bio-oil WU (Figure 2) showed that the former gave
Comparison of bio-oil MemU (Figure 1) and bio-oil WU (Figure 2) showed that the former gave
better results in terms of H2 selectivity (up to 94%) and CO selectivity (up to 84%), while selectivity
better results in terms of H2 selectivity (up to 94%) and CO selectivity (up to 84%), while
was maximum 43% and 36%, respectively, for bio-oil WU SR. It appeared that a ratio of O/C ≈ 1
selectivity was maximum 43% and 36%, respectively, for bio-oil WU SR. It appeared that a ratio
(bio-oil MemU) was good enough for SR with Ni-UGSO compared to O/C ≈ 3 (bio-oil WU),
of O/C ≈ 1 (bio-oil MemU) was good enough for SR with Ni-UGSO compared to O/C ≈ 3 (bio-oil
which suggested that the catalyst was more active at low H2 O or O content.
WU), which suggested that the catalyst was more active at low H2O or O content.

Figure
Figure 1. 1. Results
Results of of bio-oil
bio-oil MemU
MemU SR:SR:
(A)(A) WHSV
WHSV = 6.6
= 6.6 g/g
g/g /h; and (B) WHSV =
catcat/h; = 1.7 g/g
g/gcat/h.
cat /h.
Catalysts 2018, 8, 1 5 of 24
Catalysts 2018, 8, 1 5 of 25

Figure Bio-oil
2. 2.
Figure WU
Bio-oil results:
WU (A)(A)
results: WHSV = 7.1
WHSV g/g
= 7.1 g/g cat/h;
cat /h; and (B) WHSV = 1.8 g/g
g/gcatcat
/h./h.

The low
The low selectivity
selectivityof ofCOCOand andHH 2 after bio-oil WU SR were due to high O and H2O content (%O
2 after bio-oil WU SR were due to high O and H2 O content
= 73%, %H O = 52.3%, O/C ≈ 3). CO
(%O = 73%, %H2 O = 52.3%, O/C ≈ 3). CO was converted
2 was converted to to
COCO 2 through WGS (Equation (2)), and the
2 through WGS (Equation (2)), and the
presence of
presence of FeFe inin the
the catalyst
catalyst isis known
known to to catalyze
catalyze the the reaction.
reaction. Non-converted
Non-converted H H remained
remained as as H O
H22O
or was transformed to CH 4 via cracking (Equation (4)). Moreover, the
or was transformed to CH4 via cracking (Equation (4)). Moreover, the high oxygen and H2 O content high oxygen and H 2 O content
rather limited
rather limited Ni Ni reduction
reduction and and activation
activation because
because of of the
the oxidative
oxidative atmosphere, which also
atmosphere, which also explained
explained
the high CH 4 selectivity.
the high CH4 selectivity.
Figures 33 and
Figures and44show showthe theevolution
evolutionofofconcentration
concentration andand selectivity
selectivity over
over time-on-stream
time-on-stream (TOS)
(TOS) for
for SR
the theofSRboth
of both bio-oils
bio-oils at 800at◦ C800and°Catand
two at two different
different WHSV. WHSV. WithWU
With bio-oil bio-oil WU3),(Figure
(Figure 3), we
we observed
observed
that CO and thatHCO and H2 concentrations rapidly reached maximum, then decreased slightly to
2 concentrations rapidly reached maximum, then decreased slightly to stabilize at
stabilize at a quasi-steady-state.
a quasi-steady-state. At high WHSV, Atsteady
high WHSV,
state wassteady
reached state
morewas reached
quickly whilemore quickly while
concentration and
concentration and selectivity of CO and H were lower; this was corroborated
selectivity of CO and H2 were lower; this was corroborated by higher CO2 and CH4 concentration4
2 by higher CO 2 and CH
concentration
and selectivity.and selectivity.
Similar profilesSimilar profiles for
were observed wereall observed
temperatures for all temperatures
at high at highAand
and low WHSV. low
state of
WHSV. A state
equilibrium betweenof equilibrium
active-phasebetween
NiO andactive-phase
oxidized Ni NiO 2+ may and oxidized
explain theseNi
2+ may Indeed,
profiles. explain in these
the
profiles.
first stepsIndeed, in the first
of the reaction, theresteps
was of the reaction,
a transient state there
duringwas a transient
which state during
Ni2+ involved which was
in the spinels Ni2+
involvedpartially
reduced in the spinels
to Ni0 wasby thereduced
bio-oilpartially
and syngas to Ni 0 by the bio-oil and syngas produced. Then, as the
produced. Then, as the reaction continued over time,
reaction
the amount continued
of H2 O over time,inside
increased the amount of H2which
the reactor O increased inside the areactor
first re-oxidized part ofwhich
Ni0 intofirst
Nire-oxidized
2+ [41] and
a part of Ni 0 into Ni2+ [41] and favored sintering of Ni particles [42]. We consider that this mechanism,
favored sintering of Ni particles [42]. We consider that this mechanism, which was explained in detail
which
by wasetexplained
Braidy al. [43] forinmethane
detail bySR Braidy et al. [43]
over Ni/Al for methane SR over Ni/Al2O3-YSZ spinel catalyst,
2 O3 -YSZ spinel catalyst, also prevails in the case of the
also prevails
Ni-UGSO in the case of the Ni-UGSO catalyst.
catalyst.
Catalysts 2018, 8, 1 6 of 24
Catalysts 2018, 8, 1 6 of 25

Figure 3. Cont.
Catalysts 2018, 8, 1 7 of 24
Catalysts
Catalysts2018,
2018,8,8,11 77of
of25
25

Concentration ◦
Figure
Figure3.
Figure Concentrationand
3.3.Concentration andselectivity
and selectivityprofiles
selectivity profilesofof
profiles ofbio-oil
bio-oilWU
bio-oil WUSR
WU SRatat
SR at800
800 C:
800 °C:(A,B)
°C: (A,B)WHSV
(A,B) WHSV===1.8
WHSV 1.8g/g
1.8 g/g /h;
cat/h;
g/gcat
cat /h;
and (C,D)
and(C,D)
and WHSV
(C,D)WHSV = 7.1
WHSV==7.1 g/g
7.1g/g cat /h.
/h.
g/gcatcat/h.

InInthe
thecase
caseofofbio-oil
bio-oilMemU
bio-oil MemUSR
MemU SR(Figure
SR 4), the
(Figure 4), the catalyst
catalyst demonstrated
demonstratedhigh
catalystdemonstrated highstability
high stabilityat
stability atlow
at lowWHSV.
low WHSV.
WHSV.
Concentration and
Concentration and selectivity
selectivity (to
selectivity (to aa lesser
(to lesser extent)
lesser remained
extent) remained constant
constant for
remained constant for the
the entire
entire test
test duration.
duration.
for the entire test duration.
However,at
However, athigh
at highWHSV,
high WHSV,
WHSV,we we observed
observedaa gradual
weobserved agradual
gradual loss of activity
loss
loss of activity after
of activity aa first
afterafter a period
first first
period of
of stability.
period This
of stability.
stability. This
deactivation
This was
deactivation attributed
was to
attributed filamentous
to C
filamentous formed
C over
formed the
over catalyst,
the as
catalyst,it
deactivation was attributed to filamentous C formed over the catalyst, as it is shown in the next is
asshown
it is in
shown the next
in the
section
section of
next section catalyst characterization.
of catalyst
of catalyst characterization.
characterization.

Figure 4. Cont.
Catalysts 2018, 8, 1 8 of 24
Catalysts 2018, 8, 1 8 of 25

◦ (A,B) WHSV = 1.7 g/g /h;

Figure4.4.Concentration
Figure and
Concentration andselectivity profiles
selectivity of bio-oil
profiles MemU
of bio-oil SR at 800
MemU SR atC:800 °C: (A,B) WHSV =cat1.7
and (C,D)
g/gcat WHSV
/h; and (C,D)=WHSV
6.6 g/g=cat6.6
/h.g/gcat/h.

Table22displays
Table displayssome
some results
results obtained
obtained byby research
research groups
groups ononbio-oils
bio-oilscatalytic
catalyticsteam
steamreforming.
reforming.
The conditions vary which makes the comparison rather difficult. Although,
The conditions vary which makes the comparison rather difficult. Although, in all cases in all cases found in thein
found
literature,
the the the
literature, tests conditions
tests are are
conditions more favourable
more thanthan
favourable thosethose
in our
in experiments
our experiments(see Table 2), the
(see Table 2),
catalyst tested and reported here is at least equally efficient.
the catalyst tested and reported here is at least equally efficient.

Table2.2.Comparison
Comparisonof
ofYYH2 results obtained from different works on bio-oils SR.
Table H2 results obtained from different works on bio-oils SR.
Temper
Temperature
H2O/C
H2 O/C
Space
Space Velocity
TOS
TOS
YH2
Catalyst
Catalyst Feedstock
Feedstock ature Reactor
Reactor Y H2 (%)
Reference
Reference
(◦ C) (mol/mol)
(mol/mol) (h−1 ) (h−1)
Velocity (h)
(h) (%)
(°C)
RBO MemU
RBO MemU 0.6
0.6 1.7–6.6
1.7–6.6(W)
(W) 78–95
78–95
Ni-UGSO
Ni-UGSO 750–850
750–850 Fixed
Fixedbed
bed 8.3
8.3 Thiswork
This work
RBO WU 1.9 1.8–7.1 (W) 16–43
RBO WU 1.9 1.8–7.1 (W) 16–43
C11-NK BOAq 800–850 7–9 0.96–2.7 (W) Fluidized bed
Fluidized 4–90 77–89 [12]
C11-NK
Ni-MgO/Al2 O3
BOAq
BOAq
800–850
850
7–9
3.2–4.2
0.96–2.7
30 (W)
(W) Fixed bed
4–90
1
77–89
12–61
[12]
[20]
bed
Ni-MgO/Al 2O3
Ni/ceramic foam BOAq
RBO 850
500–800 3.2–4.2
2.6 30(W)
1.5–4 (W) Fixedbed
Fixed bed 1
0.5–2 12–61
54.5–93.5 [20]
[21]
Ni/ceramic
ICI 46-1/4 0.5– 54.5–
RBO
BOAq 500–800
700–75 2.6
5–35 1.5–4 (W)
760–1130 (G) Fixedbed
Fixed bed 1–6 76–100 [21]
[10]
UCI
foamG-91 2 93.5
ICI 46-1/42 O3
Ce-Ni/Co/Al
RBO
BOAq 650–850
700–75 9–15
5–35 0.08–0.23
760–1130 (L)(G) Fixed
Fixedbed
bed 0.5
1–6 65–85
76–100 [19]
[10]
+ UCI
CO2 sorbent
G-91
Ce-
Ni/Al2 O3 BOAq 600 0.5–3.5 1.5–3.8 (W)
Fixed bed
0.6–1.7 59–83 [44]
Ni/Co/Al2O3 + RBO 650–850 9–15 0.08–0.23 (L) (CLR)bed
Fixed 0.5 65–85 [19]
COG90LDP
2 sorbent RBO 550–700 3.9–9.7 2–24 (W) ** Fluidized bed - 20–95 [39]
Fixed
RBO: Raw Bio-Oil; BOAq: Bio-Oil Aqueous fraction; W: WHSV; L: LHSV; G: bed 0.6–
GC1 HSV; ** gvolatiles /gcat /h.
Ni/Al2O3 BOAq 600 0.5–3.5 1.5–3.8 (W) 59–83 [44]
(CLR) 1.7
2–24 Fluidized
G90LDP RBO 550–700 3.9–9.7 - 20–95 [39]
(W) ** bed
Catalysts 2018, 8, 1 9 of 25

RBO:
Catalysts Raw
2018, 8, 1Bio-Oil; BOAq: Bio-Oil Aqueous fraction; W: WHSV; L: LHSV; G: GC1HSV; ** gvolatiles/gcat/h.9 of 24

Figure 5 and Table 3 display the results of long-term testing (105 h) of bio-oil MemU SR at 800
°C and WHSV
Figure = 2.0
5 and g/gcat
Table 3 /h. The catalyst
display exhibited
the results the highest
of long-term testingactivity
(105 h)in
ofthe firstMemU
bio-oil 12 h, during which
SR at 800 ◦C
period CO and H 2 concentrations and selectivity were maximum. During the period between 12 and
and WHSV = 2.0 g/gcat /h. The catalyst exhibited the highest activity in the first 12 h, during which
30 h, the
period COcatalyst
and H underwent a sudden
concentrations loss of activity.
and selectivity Therefore, During
were maximum. CO andthe H2 period
concentration
betweenand12
2
selectivity
and 30 h, the had decreased
catalyst underwent of CO2 and
in favora sudden loss of 4. This was
CHactivity. attributed
Therefore, to CHformation.
CO and Catalytic
2 concentration and
activity
selectivityremained constant
had decreased in from
favor 30 to 2105
of CO andh.CHThe4 . result
This was
was atypical,
attributed tobecause,
C usually,
formation. when
Catalytic
deactivation
activity remainedstarts,constant
it generally
fromprogresses
30 to 105more
h. Therapidly over
result wasTOS. In ourbecause,
atypical, case, it seems that
usually, whenthe
catalyst was starts,
deactivation in a state of equilibrium
it generally which
progresses morewas a function
rapidly of operating
over TOS. conditions.
In our case, it seems This wascatalyst
that the a very
important
was result
in a state and showedwhich
of equilibrium that the
wasreaction mechanism
a function was similar
of operating to the
conditions. onewas
This explained by Braidy
a very important
et al. and
result [43].showed
Nevertheless, further mechanism
that the reaction investigations are needed
was similar to the to
oneconfirm
explained our highly-plausible
by Braidy et al. [43].
speculation.
Nevertheless, further investigations are needed to confirm our highly-plausible speculation.

◦ WHSV = 2.0 g/g /h

Figure 5.
Figure 5. Concentration
Concentration(A); and
(A); selectivity
and (B) profiles
selectivity of bio-oil
(B) profiles MemUMemU
of bio-oil SR at 800
SR C,
at 800 °C, WHSV cat= 2.0
and TOS = 105 h. Note: Peaks and outlier values that appear in the graph
g/gcat/h and TOS = 105 h. Note: Peaks and outlier values that appear in the graph were due to burette
were due torefilling
burette
with bio-oil.
refilling with bio-oil.

Table 3. Long TOS test results of bio-oil MemU SR.

T = 800 ◦ C
WHSV = 2.0 g/gcat /h Bio-Oil MemU
∆t = 105 h
Period (h) XC (%) YH2 (%) YCO (%) YCO2 (%) YCH4 (%) yH2 (%) yCO (%) yCO2 (%) yCH4 (%)
0–12 96.2 100 81.6 14.1 0.87 52.6 39.7 6.8 0.9
30–105 96.7 66.8 52.7 25.0 6.9 43.1 32.2 14.8 9.4
 2.0 g/g
WHSV = 2.0 g/gcat /h
cat/h Bio-OilMemU
Bio-Oil MemU
Δt = 105
105 hh

Period (h)
Period (h)
(%)
(%) (%)
(%) (%)
(%) (%)
(%) (%)
(%) (%)
(%) (%) (%)
(%) (%) (%) (%)
0–12
0–12
Catalysts 2018, 8, 1 96.2
96.2 100
100 81.6
81.6 14.1
14.1 0.87
0.87 52.6
52.6 39.7 6.8
39.7 6.8 0.90.910 of 24
30–105
30–105 96.7
96.7 66.8
66.8 52.7
52.7 25.0
25.0 6.9
6.9 43.1
43.1 32.2 14.8
32.2 14.8 9.49.4

2.3. Catalyst
2.3. CatalystCharacterization
Characterization
Characterization

2.3.1. Scanning
2.3.1. ScanningElectron
ElectronMicroscopy
Electron Microscopy
Microscopy
Figure 66 presents
Figure presents SEM
presents SEM results
SEM results of
offresh
resultsof freshcatalyst
fresh catalystNi-UGSO,
catalyst Ni-UGSO,which
Ni-UGSO, whichconsisted
which consistedof
consisted an
ofof agglomeration
ananagglomeration of
agglomeration
non-porous particles
of non-porous particles with an
particles with
with anamorphous
anamorphous shape
amorphousshape and
shapeand grain
andgrainsize
grainsizeof D = 168
sizeofofDD= =168± 59 nm
168± ±5959nm [37].
nm[37].
[37].

Figure 6. SEM of fresh Ni-UGSO.

Figure 6.
Figure SEMof
6. SEM offresh
fresh Ni-UGSO.
Ni-UGSO.

Catalyst morphology seemed slightly different after reaction, and depended on the oil type
Catalyst
Catalyst morphology seemed slightly different after reaction, and
and depended
depended on on the
the oil
oil type
injected. After morphology
bio-oil MemUseemedSR at 800 slightly
°C anddifferent
WHSV =after reaction,
1.7 g/g cat/h, we observe an eruption of small
type
injected.
injected. After
After bio-oil
bio-oil MemU
MemU SR
SR at
at 800
800 ◦°C
C and
and WHSV
WHSV == 1.7
1.7 g/g
g/g cat/h, we observe an eruption of small
cat /h, we observe an eruption of small
crystals in the shape of nanosphere over the original platelets (Figure 7A). EDX mapping (Figure 8)
crystals
crystals in
in the
the shape
shape of
of nanosphere
nanosphere over thethe original platelets (Figure 7A). EDX mapping (Figure 8)
showed that these small crystals wereoveractually original
metallic platelets
Ni particles(Figure 7A).alloy
or Ni-Fe EDXparticles,
mappingand (Figure
their 8)
showed that
showed size these
thatwasthese small
small crystals were actually metallic Ni particles or Ni-Fe alloy particles, and their
average 15.5 nm,crystals were actually
as determined by the metallic Ni particles
Sherrer equation or Ni-Fe
applied alloy
to XRD particles,
analyses. and their
A similar
average size was 15.5 nm, as determined by the Sherrer equation applied to XRD analyses. A similar
observation was made on the catalyst after bio-oil MemU SR at high WHSV (Figure 7B); in this similar
average size was 15.5 nm, as determined by the Sherrer equation applied to XRD analyses. A case,
observation
observation was made on the catalyst after bio-oil MemU SR at high WHSV (Figure 7B); in this case,
however, wewas alsomade on the
observed C catalyst
filamentafter bio-oilover
formation MemU theSR at highwhich
catalyst, WHSV (Figure
was 7B); in
probably thethis case,
main
however,
however, we
we also
also observed
observed CC filament
filament formation
formation over
over the the catalyst,
catalyst, whichwhich
was was probably
probably the the
main main
cause
cause of activity loss.
cause of activity
of activity loss. loss.

Figure 7. Micrographs of Ni-UGSO after bio-oil MemU SR at 800 ◦ C: (A) WHSV = 1.7 g/gcat /h;
and (B) WHSV = 6.6 g/gcat /h.

Micrographs of the catalyst used on bio-oil WU SR show two different morphologies at low WHSV
(Figure 9A,B). Figure 9A is a micrograph of a zone where metallic Ni particles were formed, but they
were not as numerous as in Figure 7 and were larger in size, 40.6 nm (with XRD and the Sherrer
equation). A zone of sintering can be distinguished qualitatively in Figure 9B. The two morphologies
 Catalysts 2018, 8, 1 11 of 24

can2018,
Catalysts explain
8, 1 the low catalyst activity in comparison to the one used for bio-oil MemU SR. At high
11 of WHSV
25
(Figure 9C,D), the catalyst clearly showed signs of sintering, with some of the particles coalesced or
agglomerated. In bothofcases,
Figure 7. Micrographs no Cafter
Ni-UGSO deposits
bio-oilwere
MemUfound
SR atwith high
800 °C: (A)and low =WHSV,
WHSV as/h;the
1.7 g/gcat andwater
(B) gasified
WHSV
it = 6.6and
into CO g/gcat
CO/h.2 . In general, similar observations were made with the catalyst in the various tests.

Catalysts 2018, 8, 1 8. EDX mapping 12 of 25

Figure
Figure 8. EDX mapping of Niof Ni particles
particles after after bio-oil
bio-oil MemU MemU
SR (ESR (E kV).
= 20 = 20 kV).

Micrographs of the catalyst used on bio-oil WU SR show two different morphologies at low
WHSV (Figure 9A,B). Figure 9A is a micrograph of a zone where metallic Ni particles were formed,
but they were not as numerous as in Figure 7 and were larger in size, 40.6 nm (with XRD and the
Sherrer equation). A zone of sintering can be distinguished qualitatively in Figure 9B. The two
morphologies can explain the low catalyst activity in comparison to the one used for bio-oil MemU
SR. At high WHSV (Figure 9C,D), the catalyst clearly showed signs of sintering, with some of the
particles coalesced or agglomerated. In both cases, no C deposits were found with high and low
WHSV, as the water gasified it into CO and CO2. In general, similar observations were made with the
catalyst in the various tests.

Figure 9. Micrographs of Ni-UGSO after bio-oil MemU SR at 800 ◦ C: (A,B) WHSV = 1.7 g/gcat /h;
Figure
and 9. Micrographs
(C,D) WHSV = 6.6 of
g/gNi-UGSO
cat /h.
after bio-oil MemU SR at 800 °C: (A,B) WHSV = 1.7 g/gcat/h; and
(C,D) WHSV = 6.6 g/gcat/h.

Figure 10 represents micrographs of the catalyst after the 105-h test. The morphology was the
same as in Figure 7. However, it seems that there was more C deposited at the catalyst’s surface
(Figure 10B) without significantly affecting catalytic activity.
 Figure 9. Micrographs of Ni-UGSO after bio-oil MemU SR at 800 °C: (A,B) WHSV = 1.7 g/gcat/h; and
Catalysts 2018, 8, 1 12 of 24
(C,D) WHSV = 6.6 g/gcat/h.

Figure 10 represents
Figure micrographs
10 represents micrographsof theofcatalyst after after
the catalyst the 105-h test. test.
the 105-h The morphology
The morphologywas the
was the
samesame
as inas
Figure 7. However, it seems that there was more C deposited at the catalyst’s
in Figure 7. However, it seems that there was more C deposited at the catalyst’s surface
surface
(Figure 10B) without significantly affecting catalytic activity.
(Figure 10B) without significantly affecting catalytic activity.

Catalysts 2018, 8, 1 13 of 25

2.3.2. X-ray Diffraction

Figure 11 depicts the XRD pattern of the fresh catalyst. We can distinguish two groups of phases
(Table 4): (a) one group that englobed the spinels NiFeAlO4, NiFe2O4, MgFeAlO4, AlFe2O4, Fe3O4 (2θ
= 19°, 31°, 36°, 43°, 54°, 58° and 63°); and (b) another group that englobed oxides NiO, MgO and their
Figure 10. Micrographs of Ni-UGSO after bio-oil MemU SR at 800 ◦ C, WHSV = 2.0 g/gcat /h and
Figure 10. Micrographs
solid solutions NiO-MgOof Ni-UGSO
(2θ = after bio-oil
37°, 43°, MemU
63°, 74° SR
andat 79°).
800 °C, WHSV
Such grouping cat/h
= 2.0 g/gis and TOS =because of
proposed
TOS = 105 h. (A) Zone without C deposits; (B) Zone with C deposits.
105 h. (A) Zone without C deposits; (B) Zone with C deposits.
serious peak overlapping for most of the same type phases.
2.3.2. X-ray Diffraction
Table 4. XRD phase legend.
Figure 11 depicts the XRD pattern of the fresh catalyst. We can distinguish two groups of phases
NiFeAlO4, MgAl2O4, FeAl2O4 SiO2 (from quartz wool)
(Table 4): (a) one group that englobed the spinels NiFeAlO4 , NiFe2 O4 , MgFeAlO4 , AlFe2 O4 , Fe3 O4
(2θ = 19◦ , 31◦ , 36◦ , 43◦ ,MgO,
54◦ , 58NiO,
◦ andNiO-MgO Fe3C that englobed oxides NiO, MgO and
63◦ ); and (b) another group
their solid solutions NiO-MgO (2θ = 37 , 43◦ , 63◦ , 74◦ and 79Fe
Ni, FeNi, Fe 0.5Ni◦0.5, FeNi 3 ◦ ).2O3
Such grouping is proposed because of
Carbone
serious peak overlapping for most of the same type phases.

Catalysts 2018,
Catalysts 8,
8, 11 8,
2018, 8, 13
13 of 25
Catalysts
Catalysts 2018,2018,
Catalysts 2018, 8, 11
1 13
of13 of
25of
13 25
of 25
25

2.3.2.
2.3.2. X-ray
2.3.2. Diffraction
X-ray
X-ray Diffraction
Diffraction
Figure
Figure 11
11 depicts
Figure depicts the
the XRD
11 depicts the XRD
XRD pattern of
of the
pattern
pattern of fresh
the catalyst.
the fresh
fresh We
catalyst.
catalyst. We Wecan distinguish
can can two
distinguish
distinguish twotwogroups
groups groups of
of phases
of phases
phases
(Table
(Table 4):
(Table (a)
4):
4): (a)
(Table one
(a)
4):one group
one
group
(a) one that
group englobed
that
thatthat
group englobed the
englobed spinels
the
the spinels
englobed NiFeAlO
spinels NiFeAlO
NiFeAlO
the spinels NiFeAlO4, NiFe
4, NiFe
4, 2 O
NiFe
44, NiFe4 , MgFeAlO
O
2O4, 22MgFeAlO
2 4 , MgFeAlO
4 , AlFe
4, AlFe
O44, MgFeAlO 4 , 2 O
AlFe4 , Fe
2O4, 22Fe
44, AlFe 2 O O 4 (2θ
O443,OFe
43, 333O
4 (2θ
Fe O444 (2θ
(2θ
== 19°,
19°, 31°,
= 19°, 36°,
31°,31°, 43°,
36°,36°, 54°,
43°,43°, 58°
54°,54°, and 63°);
58° and
58° and and
63°);63°); (b)
andand another group
(b) another
(b) another that
group
group englobed
thatthat englobed
englobed oxides NiO,
oxides
oxides NiO,NiO, MgO
MgO MgO and
andand their
theirtheir
solid solutions
solidsolid
solutions NiO-MgO
solutions NiO-MgO
NiO-MgO (2θ == 37°,
(2θ (2θ 43°,
= 37°,
37°, 63°,
43°,43°, 74°
63°,63°, and
74° 74°
andand79°). Such
79°).79°).
SuchSuchgrouping
grouping
grouping is
is proposed
is proposed
proposed because
because because of
of of
serious
serious peak
serious
peakpeak
serious overlapping
peak
overlapping for
overlapping most
for
for most
overlapping of the
Figure
most of
of the
Figure
for most same
11.
theXRD
same
of11. type
same
theXRD type
same phases.
spectra
type
spectra
type of fresh
phases.
phases.
of catalyst.
fresh catalyst.
phases.

In Figures 12 and 13, it can be Table Table

seen
Table Table
Table4. XRD
4. 4.
that,
XRD XRD
4. XRD
XRDphase
phase
4.generally,
phase legend.
legend.
phase the
legend.
phase intensities of spinel peaks decreased in
legend.
legend.
favor of metallic Ni or Ni-Fe alloy
NiFeAlO 4, MgAl
(2θ2O=444°,, FeAl 51°, 76°)-attributed
2O4 22O44 SiO (from peaks. Figure
quartz 13 shows peaks which
wool)
NiFeAlO
NiFeAlO 444, MgAl
4, MgAl 2O O444, FeAl
4, 22FeAl 2O SiO22SiO
O44 2 crystallite (from 222 (from quartz
quartz wool)wool)
are broader than thoseNiFeAlO
in Figure4 , MgAl
12, 2 O4 ,2 FeAl
implying 2that 4 SiO
size 2 (from
was quartz
smaller wool)
in Ni-UGSO after bio-
MgO,
MgO,MgO,
MgO, NiO,
NiO,
NiO, NiO-MgO
NiO, NiO-MgO
NiO-MgO
NiO-MgO Fe
Fe 3
3C
CFeFe333C3 C
oil MemU SR, which is in agreement with the micrographs in Figures 7 and 9. It also confirmed that
Ni,
Ni,FeNi,
Ni, Ni,
FeNi,
FeNi, Fe
FeNi,
Fe0.5 Ni
FeNi ,, FeNi
0.5Ni 0.5, FeNi
, 0.5
FeNi 3 Fe22OOFe
3 222O
3 Fe
23O
after Fe Ni FeNi at 2θ =Fe32°,
0.5 0.5
0.5
0.5 333 3 3
there was more sintering 0.5
bio-oil 0.5
0.5
WU SR.33Peaks
0.5
40°, 3
and 52° in Figure 12 are attributed
Carbone
Carbone
Carbone
Carbone
Carbone
to hematite (Fe2O3) formed probably after the oxidation of magnetite (Fe3O4) or Fe involved in spinel
phases because of the high amount of O in bio-oil WU SR. In Figure 13A, the small peaks that appear
between 38° and 49° are characteristic of cementite (Fe3C); its presence shows chemical interaction
between reduced Fe and deposited C. Nevertheless, cementite was observed only in this test.
Catalysts 2018, 8, 1 13 of 24

In Figures 12 and 13, it can be seen that, generally, the intensities of spinel peaks decreased in
favor of metallic Ni or Ni-Fe alloy (2θ = 44◦ , 51◦ , 76◦ )-attributed peaks. Figure 13 shows peaks which
are broader than those in Figure 12, implying that crystallite size was smaller in Ni-UGSO after bio-oil
MemU SR, which is in agreement with the micrographs in Figures 7 and 9. It also confirmed that there
was more sintering after bio-oil WU SR. Peaks at 2θ = 32◦ , 40◦ , and 52◦ in Figure 12 are attributed to
hematite (Fe2 O3 ) formed probably after the oxidation of magnetite (Fe3 O4 ) or Fe involved in spinel
phases because of the high amount of O in bio-oil WU SR. In Figure 13A, the small peaks that appear
between 38◦ and 49◦ are characteristic of cementite (Fe3 C); its presence shows chemical interaction
between reduced
Catalysts 2018, 8,Fe
1 and deposited C. Nevertheless, cementite was observed only in this test.
14 of 25
Catalysts 2018, 8, 1 14 of 25

12. XRD spectra ◦ C: (A) WHSV = 1.8 g/g /h;

FigureFigure
Figure 12.
12. XRD
XRD spectraofof
spectra ofNi-UGSO
Ni-UGSO after
Ni-UGSO after
after bio-oil
bio-oil
bio-oil WUWU
WU SR atSR
SR at 800at
800 °C:800
°C: (A)
(A) WHSV
WHSV == 1.8
1.8 g/g /h; and (B);
cat/h; and (B); cat
g/gcat
WHSV
and (B) WHSV = 7.1
= g/g
7.1 /h.
g/g
cat
WHSV = 7.1 g/gcat/h. cat /h.

Figure 13. Cont.

 Catalysts 2018, 8, 1 15 of 25
Catalysts 2018, 8, 1 14 of 24
Catalysts 2018, 8, 1 15 of 25

13. XRD
FigureFigure spectra of Ni-UGSO after bio-oil MemU SR at 800 ◦WHSV
C: (A)= WHSV = 1.7 g/g /h;
cat/h; and (B) cat
Figure 13. 13.
XRD XRD spectra
spectra ofof Ni-UGSOafter
Ni-UGSO after bio-oil
bio-oil MemU
MemU SR
SRatat800
800°C:
°C:(A)
(A) WHSV 1.7 g/gg/g
= 1.7 cat/h; and (B)
and (B) WHSV
WHSV = 6.6=g/g
6.6catg/g
/h. cat /h.
WHSV = 6.6 g/gcat/h.

XRD spectra of the catalyst after the 105-h long test (Figure 14) was similar to those obtained
XRDXRDspectra of of
spectra thethe
catalyst after
catalyst thethe
after 105-h long
105-h longtesttest
(Figure 14)14)
(Figure was similar
was to to
similar those obtained
those with
obtained
with the catalyst after the 500-min test. Principal peaks of spinel and metallic phases were present.
thewith the catalyst
catalyst after theafter the 500-min
500-min test. test. Principal
Principal peaks peaks
of spinel of and
spinel and metallic
metallic phases phases
The high peak at 22° was attributed to non-efficiently removed quartz wool from the catalyst. high
were were present.
present. The
The
peak at 22◦ was
high
Hematitepeak at were
22° was
attributed
peaks attributed to long
to non-efficiently
probably due to the non-efficiently
removed
exposure removed
quartz
time. quartz
wool from thewool fromHematite
catalyst. the catalyst.
peaks
Hematite
were peaks
probably duewere probably
to the due to the
long exposure long exposure time.
time.

Figure 14. XRD spectra of Ni-UGSO after bio-oil MemU SR at 800 °C, WHSV = 2.0 g/gcat/h and TOS =
105 h.
Figure
Figure 14.14.XRD
XRDspectra of Ni-UGSO
spectra of Ni-UGSOafter
afterbio-oil
bio-oil MemU
MemU SR SR at 800
at 800 ◦ C, WHSV
°C, WHSV = 2.0
= 2.0 g/gcat/hg/g /h and
andcatTOS =
2.3.3.
105=h.
TOS TGA
105 h. Analysis
Figure 15 displays TGA results for Ni-UGSO samples taken after bio-oil WU SR (Figure 15A)
2.3.3.
2.3.3. and
TGATGA Analysis
bio-oil MemU SR (Figure 15B) at 775 °C and low WHSV.
Analysis
Figure
Figure 1515 displays
displays TGA
TGA results
results forfor Ni-UGSO
Ni-UGSO samples
samples taken
taken after
after bio-oilWU
bio-oil WUSRSR (Figure
(Figure 15A)and
15A)
and bio-oil MemU SR (Figure 15B) at◦ 775 °C and low WHSV.
bio-oil MemU SR (Figure 15B) at 775 C and low WHSV.
In Figure 15A,B, we observe a weight loss of 0.2% starting around 90 ◦ C. This is attributed to
water evaporation and desorption of other species like CO2 . Then, weight gain is observed starting at
~250 ◦ C for the sample from bio-oil MemU SR and at ~350 ◦ C for the sample from bio-oil WU SR. It is
attributed to Ni0 nanoparticles oxidation, as demonstrated by Song et al. [45]; the authors also affirm
that Ni0 nanoparticles are oxidized at lower temperature than bulk Ni materials which start oxidizing
at about 600 ◦ C. Thus, the difference in Ni particle size determined from XRD by Sherrer equation may
explain the difference in oxidation temperature. Moreover, the weight gain in Figure 15B was 8.4%
and 5.5% in Figure 15A, which implies that there were less Ni0 after bio-oil WU SR because of high
water/oxygen content. In Figure 15B, the weight loss of 3.9% at ~600 ◦ C was attributed to C deposited
over the catalyst, this amount is low considering the ratio O/C ≈ 1 (and H2 O/C = 0.6) and TOS of
500 min. No C was detected by TGA in Figure 15A.
Catalysts 2018, 8, 1 15 of 24
Catalysts 2018, 8, 1 16 of 25

106 0.3
A
TG-Blanc (%) dTG (%/min)

0.25
105
0.2
104
TG-Blanc (%)

dTG (%/min)
0.15
103
0.1
102
0.05

101
0

100 -0.05

99 -0.1
0 100 200 300 400 500 600 700 800 900

Temperature (°C)

109 TG-Blanc (%) dTG (%/min)

0.6
108
B 0.4
107
106 0.2
TG-Blanc (%)

dTG (%/min)
105
0
104
-0.2
103
102 -0.4
101
-0.6
100
99 -0.8
0 100 200 300 400 500 600 700 800 900
Temperature (°C)

Figure 15. TGA results of Ni-UGSO after SR at T = 775 °C and low WHSV: (A) bio-oil WU; and (B)
Figure 15. TGA results of Ni-UGSO after SR at T = 775 ◦ C and low WHSV: (A) bio-oil WU;
bio-oil MemU.
and (B) bio-oil MemU.
Catalysts 2018, 8, 1 16 of 24

2.3.4. BET Measurement

Table 5 displays the results of BET measurement of fresh and used catalyst after bio-oil SR at
825 ◦ C and WHSV ~1.8 g/gcat /h. Fresh Ni-UGSO had a specific area of 6.70 m2 /g. After the reaction,
the surface increased due to reduction and eruption of Ni particles (see Figure 7) to reach 10.49 m2 /g
in the case of MemU SR and 8.98 m2 /g in WU SR. The difference was attributed to the difference in
particle size between the two samples because of different reduction (or oxidation) conditions. Indeed,
more H2 O was present in bio-oil WU, which favors sintering and, consequently, a loss of specific area.
However, the amount of C deposited on the used catalyst after MemU SR (TGA in Figure 15B) may
also contribute to the increase of the specific area.

Table 5. BET results.

Sample S (m2 /g) Pore Volume (cm3 /g)

Fresh catalyst 6.70 0.0202
Used catalyst (MemU) 10.49 0.0241
Used catalyst (WU) 8.98 0.0144

3. Materials and Methods

3.1. Bio-Oils
Two different bio-oils were subjected to SR testing. They were produced and provided by
Memorial University (St. John’s, NL, Canada) and Western Ontario University (London, ON, Canada),
designated hereafter as MemU and WU, respectively. A description of the experimental set-up for
bio-oil production can be found in [46] (for MemU) and in [47] (for WU). Before testing, the bio-oils
were centrifuged in the J-20XP Avanti centrifuge (Beckman Coulter, Indianapolis, IN, USA) and
filtered to remove solids. The physico-chemical properties of the resulting bio-oils were then analyzed.
H2 O was measured by the Karl-Fischer method, using a TOLEDO V20 KF titrator (Mettler-Toledo,
Mississauga, ON, Canada), solvent HYDRANAL medium K (Honeywell Fluka, Morris Plains, NJ,
USA) and the reagent HYDRANAL composite 5K (Honeywell Fluka, Morris Plains, NJ, USA) [48].
pH was measured with an OAKTON pH700 (OAKTON Instruments, Vernon Hills, IL, USA) pH-meter.
Elements (C, H and O) were analyzed with a TrueSpec Micro (LECO, St. Joseph, MI, USA) apparatus.
Liquid densities were quantified with a DMA 3000 density-meter (Anton Paar, Montréal, QC, Canada).

3.2. Catalyst Preparation and Characterization

3.2.1. UGSO
UGSO is a mining residue derived from the process of upgrading titanium slag (UGS) of the
company Rio Tinto Iron and Titanium (RTIT) (Sorel-Tracy, QC, Canada). It is constituted of a mixture
of metal oxides, mainly Fe, Mg, Al and, to a lesser extent, Cr, V, Ti, Si, Na, Mn, Ca, K, P, Zr and
Zn [34,39]. The main crystalline phases present in this residue are: MgFe2 O4 , FeAl2 O4 , and a solid
solution of both Mg(Fe,Al)2 O4 and MgO [49]. The mining residue was support for the Ni-UGSO
catalyst. More information on it can be found in [37].

3.2.2. Ni-UGSO
The catalyst was prepared via improved solid-state reaction [50]. UGSO (RTIT) was first ground
in a mortar and sieved at 53 µm, then wetted and mixed with Ni(NO3 )2 ·6H2 O (Sigma-Aldrich,
Darmstadt, Germany) at a proportion such that the final dry formulation contained 13 wt % Ni loading.
The mixture was then dried at 105 ◦ C for 4 h and, finally, the catalyst was calcined at 900 ◦ C during 12 h
to decompose the nitrates and convert all Ni content into spinel phases (Figure 16). Fresh and spent
catalysts (Ni-UGSO) were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM),
 The catalyst was prepared via improved solid-state reaction [50]. UGSO (RTIT) was first ground in
a mortar and sieved at 53 μm, then wetted and mixed with Ni(NO3)2·6H2O (Sigma-Aldrich,
Darmstadt, Germany) at a proportion such that the final dry formulation contained 13 wt % Ni
loading. The mixture was then dried at 105 °C for 4 h and, finally, the catalyst was calcined at 900 °C
Catalysts 2018, 8, 1 17 of 24
during 12 h to decompose the nitrates and convert all Ni content into spinel phases (Figure 16). Fresh
and spent catalysts (Ni-UGSO) were analyzed by X-ray diffraction (XRD), scanning electron
microscopy (SEM), Brunauer–Emmett–Teller
Brunauer–Emmett–Teller physisorption (BET),physisorption
energy dispersive(BET), energy
X-ray dispersive
mapping (EDXX-ray mapping
mapping) and
(EDX mapping) andanalysis
thermogravimetric thermogravimetric
(TGA). analysis (TGA).

Figure 16. Ni-UGSO synthesis by the improved solid-state reaction.

Figure 16. Ni-UGSO synthesis by the improved solid-state reaction.

XRD
XRD analysis
analysis was
was performed
performed with with aa Philips X’pert PRO
Philips X’pert PRO diffractometer
diffractometer (PANalytical,
(PANalytical, Almelo,
Almelo,
The Netherlands) which was operated with data collector analysis
The Netherlands) which was operated with data collector analysis software (PANalytical). The software (PANalytical).
The radiation
radiation sourcesource
was was Kα
Kα of Cuof(15,418
Cu (15,418 Å) produced
Å) produced at 40atkV
40and
kV 50andmA.
50 mA. The anti-dispersion
The anti-dispersion slit
slit was
was ◦ ◦ ◦
fixedfixed
at ½°at and
1/2 and divergent
divergent slit slit at /Analysis
at ¼°. 1 4 . Analysiswaswas conducted
conducted onon a 2θrange
a 2θ rangeofof15–80°,
15–80 , and
and overall
overall
analysis time was 47 min. XRD was undertaken with built-in software, and
analysis time was 47 min. XRD was undertaken with built-in software, and database research carrieddatabase research carried
out
out with
with MDI
MDI JADE
JADE 2010
2010 (Materials
(Materials Data,Data, Livermore,
Livermore, CA, CA, USA,
USA, 2017).
2017).
Micrographs were taken on SEM with a field emission
Micrographs were taken on SEM with a field emission gun Hitachi S-4700 gun Hitachi S-4700 (Hitachi,
(Hitachi, Chiyoda-ku,
Chiyoda-ku,
Tokyo,
Tokyo, Japan). EDX analysis was performed on the same apparatus, which also involved aa X-MAX
Japan). EDX analysis was performed on the same apparatus, which also involved X-MAX
X-ray
X-ray detector
detector(Oxford
(OxfordInstruments,
Instruments, Abingdon,
Abingdon,UK). UK).
The catalyst samplessamples
The catalyst were prepared
were by dispersion
prepared by
in ethanol, followed by ultrasonic treatment; they were then deposited on silicon
dispersion in ethanol, followed by ultrasonic treatment; they were then deposited on silicon wafer. wafer. After a few
minutes
After a fewof drying
minutes atof
room temperature,
drying the samplesthe
at room temperature, were metallized
samples wereby sputter coating
metallized of acoating
by sputter Pd-Au
cathode,
of a Pd-Au using Ar plasma
cathode, usingin
Ara plasma
Hummer in VI device (Anatech
a Hummer VI device Ltd., Battle Creek,
(Anatech MI, USA).
Ltd., Battle Creek, MI, USA).
TGA
TGA analysis was conducted on catalyst samples after reaction using the SETSYS
analysis was conducted on catalyst samples after reaction using the SETSYS 2424 apparatus
apparatus
(Setaram,
(Setaram, Caluire,
Caluire, France)
France) to
to assess
assess thethe amount
amount of of deposited
deposited C. C.
Surface
Surface area
area analysis
analysis (BET
(BET physisorption)
physisorption) was was undertaken
undertaken withwith aa Micromeritics
Micromeritics ASAP
ASAP 20202020
apparatus (Micrometrics, Norcross, GA, USA), employing N at − 196 ◦ C.
apparatus (Micrometrics, Norcross, GA, USA), employing N22 at −196 °C.

3.3. Experiments and Calculations

3.3.1. Experimental Set-Up

The layout of the experimental set-up is shown in Figure 17. It comprised a Quartz tube reactor
(Technical Glass products, Painesville, OH, USA) (d = 40 mm) placed inside a furnace. The catalyst was
positioned in the middle, over a quartz disc, and dispersed in quartz wool. Initially, the bio-oil was in
a burette; it was then injected at the top of the reactor by peristaltic pump. Drops fell on the catalyst,
and the gas formed after conversion left the reactor and was cooled through an ice bath to condense
H2 O off the gaseous products. The so-dried gas then passed through a molecular sieve and charcoal
columns to remove residual H2 O and other impurities, and the last filter removed entrained solids.
The gas was then sampled and analyzed in a Varian CP-3800 gas chromatograph (GC). Flowrate was
measured by a Delta II mass flow meter (Brooks Instruments, Hatfield, PA, USA).
was in a burette; it was then injected at the top of the reactor by peristaltic pump. Drops fell on the
catalyst, and the gas formed after conversion left the reactor and was cooled through an ice bath to
condense H2O off the gaseous products. The so-dried gas then passed through a molecular sieve and
charcoal columns to remove residual H2O and other impurities, and the last filter removed entrained
solids. The 2018,
Catalysts gas 8,was
1 then sampled and analyzed in a Varian CP-3800 gas chromatograph (GC). 18 of 24
Flowrate was measured by a Delta II mass flow meter (Brooks Instruments, Hatfield, PA, USA).

Figure 17. Experimental

Figure set-up.
17. Experimental set-up.

3.3.2. TestTest
3.3.2. Conditions
Conditions
Nineteen runsruns
Nineteen werewere
undertaken in thisin
undertaken study.
this Five temperatures
study. (750, 775, (750,
Five temperatures 800, 825 and
775, 850825
800, °C),and
two850 ◦ C), loads
catalyst (1 and 4loads
two catalyst g) and(1 two
and bio-oils
4 g) and(MemU and WU)
two bio-oils (MemUwereand
tested:
WU) a long-term testa(105
were tested: h)
long-term
wastest
also(105
carried
h) was also carried out with bio-oil MemU and 4 g of Ni-UGSO. All experimentsatwere
out with bio-oil MemU and 4 g of Ni-UGSO. All experiments were performed
atmospheric
performed pressure and without
at atmospheric a catalyst
pressure and activation
without astep. Indeed,
catalyst as detailed
activation step.byIndeed,
Lea-Langton et
as detailed
al. [44], bio-oils actedet
by Lea-Langton directly as bio-oils
al. [44], Ni-reducing
actedagents. The
directly astest conditionsagents.
Ni-reducing are summarized in Table 6. are
The test conditions
summarized in Table 6.
Table 6. Experimental conditions.
Table 6. Experimental conditions.
Reactant Catalyst Weight Temperature (°C) Injection Flowrate TOS
Bio-oil WU
Reactant Catalyst Weight ◦
Temperature ( C) Injection Flowrate TOS
1 g and 4 g 750, 775, 800, 825, 850 ~0.1 mL/min ~500 min
Bio-oil MemU
Bio-oil WU
1 g and 4 g 750, 775, 800, 825, 850 ~0.1 mL/min ~500 min
Bio-oil Bio-oil
MemUMemU 4g 800 ~0.1 mL/min 105 h
Bio-oil MemU 4g 800 ~0.1 mL/min 105 h

3.3.3. Calculations
This section details the main calculation and formulae used to make the elemental mass balance.
XC was the conversion of C to gaseous products: CO, CO2 , CH4 , C2 H4 , C2 H6

mol of gaseous C
XC = × 100 (5)
mol of C in biooil
Yi was selectivity toward the product i H2 , CO, CO2 , CH4

2 × mol of H2
YH2 = × 100 (6)
mol of H in biooil
mol of CO
YCO = × 100 (7)
mol of C in biooil
Catalysts 2018, 8, 1 19 of 24

mol of CO2
YCO2 = × 100 (8)
mol of C in biooil
4 × mol of CH4
YCH 4 = × 100 (9)
mol of H in biooil
YH2 O was H2 O yield
mass of H2 O formed
YH2 O = × 100 (10)
mass of biooil
Moles of C, H and O in bio-oils were calculated, knowing the amount injected and the elemental
analysis results, which are given in wt % and easily converted to mol %. Mole rates of the gases were
calculated with ideal gas Equation (11).
. .
Pv = nRT (11)

Combination of the GC results with total flowrate measurement allowed mass balance calculations.
An example of the methodology and calculation of elemental mass balance for the testing of
bio-oil MemU SR at 800 ◦ C and WHSV = 1.7 g/gcat /h is presented below:

1. The injection flowrate of the bio-oil was adjusted to ~0.1 mL/min; the amounts of C, H and O
injected were calculated by multiplying mass flowrate, and the mass fraction of each element
was determined by elemental analysis.
2. Concentration measurements of gases by GC are reported in Table 7: the interval between each
measurement was 30 min.
3. The flowrate of the produced gas was measured by massflow meter and recorded.
4. Using the ideal gas equation, we calculated the molar flow of each gas at 1 atm and 20 ◦ C,
and, by multiplying the stoichiometric number, we got the amount of each element at each time t,
and we then summed it to obtain the total (Table 8).
5. We weighed solid C deposited on the reactor wall and the liquid produced in the condenser,
considering that it was composed 100% of H2 O. In this example, mC = 1.63 g (0.135 mol) and
mH2 O = 3.43 g (nH = 0.38 mol, nO = 0.19 mol).
6. We calculated the yield at each time t and for each product with Equations (6)–(9) (Table 9).
7. Then, we calculated relative error between input and output and we got (Table 10).

Table 7. Gas composition from GC analysis.

Concentration (% mol)
Time (min)
CO2 CO H2 C2 H4 C2 H6 CH4
0 0.00 0.00 0.00 0.00 0.00 0.00
9 6.27 32.22 57.88 0.08 0.13 3.42
24 13.60 38.25 47.65 0.03 0.05 0.41
54 6.39 41.00 51.89 0.01 0.03 0.66
84 6.26 40.46 52.52 0.01 0.02 0.74
114 6.49 40.07 52.65 0.00 0.01 0.78
144 6.77 39.85 52.56 0.00 0.01 0.81
174 6.86 39.87 52.40 0.00 0.01 0.86
204 7.00 39.67 52.40 0.00 0.01 0.92
234 6.96 39.74 52.37 0.00 0.00 0.92
264 6.93 39.91 52.15 0.00 0.00 1.00
294 6.93 39.92 52.10 0.00 0.00 1.04
324 7.35 39.05 52.42 0.00 0.00 1.17
354 7.22 39.51 52.11 0.00 0.00 1.15
384 7.29 39.57 51.84 0.01 0.00 1.29
414 7.21 39.69 51.82 0.01 0.01 1.27
459 7.17 39.52 51.87 0.01 0.01 1.42
504 7.46 39.09 51.90 0.01 0.01 1.53
Catalysts 2018, 8, 1 20 of 24

Table 8. Moles calculated for each molecule at each time t.

Number of Moles
Time (min)
C in H in CO2 CO H2 C2 H4 C2 H6 CH4
0 0 0 0 0 0 0 0 0
9 0.0347 0.0742 0.0033 0.0169 0.0303 0.0000 0.0001 0.0018
24 0.0579 0.1237 0.0153 0.0430 0.0535 0.0000 0.0001 0.0005
54 0.1158 0.2474 0.0133 0.0852 0.1078 0.0000 0.0001 0.0014
84 0.1158 0.2474 0.0128 0.0828 0.1075 0.0000 0.0000 0.0015
114 0.1158 0.2474 0.0128 0.0790 0.1038 0.0000 0.0000 0.0015
144 0.1158 0.2474 0.0137 0.0809 0.1067 0.0000 0.0000 0.0016
174 0.1158 0.2474 0.0139 0.0810 0.1064 0.0000 0.0000 0.0017
204 0.1158 0.2474 0.0151 0.0855 0.1129 0.0000 0.0000 0.0020
234 0.1158 0.2474 0.0149 0.0852 0.1123 0.0000 0.0000 0.0020
264 0.1158 0.2474 0.0145 0.0835 0.1092 0.0000 0.0000 0.0021
294 0.1158 0.2474 0.0153 0.0884 0.1154 0.0000 0.0000 0.0023
324 0.1158 0.2474 0.0169 0.0896 0.1203 0.0000 0.0000 0.0027
354 0.1158 0.2474 0.0168 0.0917 0.1210 0.0000 0.0000 0.0027
384 0.1158 0.2474 0.0171 0.0928 0.1215 0.0000 0.0000 0.0030
414 0.1158 0.2474 0.0163 0.0897 0.1171 0.0000 0.0000 0.0029
459 0.1737 0.3711 0.0256 0.1414 0.1855 0.0000 0.0000 0.0051
504 0.1737 0.3711 0.0257 0.1346 0.1787 0.0000 0.0000 0.0053
Element Total Element Produced per Molecule Total
C 1.9456 0.2633 1.4511 0.0005 0.0008 0.0400 1.7558
H 4.1564 3.8200 0.0011 0.0025 0.1602 3.9837
O 0.5266 1.4511 1.9778

Table 9. Yield of each product.

Yield (%)
Time (min)
CO2 CO H2 C2 H4 C2 H6 CH4
0 0.0 0.0 0.0 0.2 0.5 9.7
9 9.5 48.6 8.7 0.1 0.3 1.5
24 26.4 74.2 86.5 0.0 0.2 2.2
54 11.5 73.6 87.2 0.0 0.1 2.4
84 11.1 71.5 86.9 0.0 0.1 2.5
114 11.1 68.2 83.9 0.0 0.0 2.7
144 11.9 69.8 86.2 0.0 0.0 2.8
174 12.0 69.9 86.0 0.0 0.0 3.2
204 13.0 73.8 91.3 0.0 0.0 3.2
234 12.9 73.6 90.8 0.0 0.0 3.4
264 12.5 72.1 88.2 0.0 0.0 3.7
294 13.3 76.4 93.3 0.0 0.0 4.3
324 14.6 77.4 97.3 0.0 0.0 4.3
354 14.5 79.2 97.8 0.0 0.0 4.9
384 14.8 80.1 98.2 0.0 0.0 4.6
414 14.1 77.4 94.6 0.0 0.0 5.5
459 14.8 81.4 100.0 0.0 0.0 5.7
504 14.8 77.5 96.3 0.2 0.5 9.7

Table 10. Error calculation results.

C in (mol) C out (mol) Error (%)

1.96 1.89 3.73
H in (mol) H out (mol) Error (%)
4.20 4.36 3.98
O in (mol) O out (mol) Error (%)
2.00 2.17 8.25
Bio-Oil in (g) Bio-Oil out (g) Error (%)
59.82 61.76 3.23
Catalysts 2018, 8, 1 21 of 24

4. Conclusions
Bio-oil SR is one of the promising routes for renewable H2 or biosyngas production. In this work,
we undertook SR of two bio-oils without separate steam addition and H2 O/C ratio as low as 0.6 and
1.85; we demonstrated the performance of a new spinel catalyst (Ni-UGSO) made from a mining
residue via improved solid-state reaction. The catalyst exhibited performances in terms of activity and
selectivity, which were close to thermodynamic equilibrium. More precisely:

• The catalyst was activated quickly (without a pre-reduction step).

• It was efficient at H2 O/C, being 2–5 times lower than those used in industrial H2 production.
• No severe deactivation was observed in all tests, even after C formation.

Ni-UGSO performed better at low H2 O/C ratio with high yield in biosyngas. When bio-oils
contained higher amounts of H2 O, the catalyst’s activity was lower, mainly due to a lower level of
activation through Ni reduction. Moreover, it seemed that high H2 O content also enhanced sintering
at the catalyst surface.
Longer testing (105 h TOS) demonstrated high resilience of the catalyst, which stayed active
during the entire period (105 h) with maximum activity observed in the first 12 h.
XRD spectra showed that, after testing, spinels were reduced to metallic phases of Ni and
Ni-Fe alloys.
TGA results reveal that only the catalyst used in MemU oil SR suffered C deposition; the latter
accounts for 3.9%. This is considerably lower that all other referred works, despite a lower O/C ≈ 1.
SEM micrographs revealed that, in the case of MemU SR, small Ni crystals appeared, and this
represented activated catalyst morphology. In the case of WU SR, the catalyst was not fully activated
due to large H2 O content, which also induced sintering, which was in agreement with the BET
measurements. The micrographs also show some filamentous C formed in SR at low WHSV.

Acknowledgments: This work was made possible with the collaboration of Prof. Kelly Hawboldt from Memorial
University (NL, Canada) and Prof. Cedric Briens from Western Ontario University (ON, Canada): they are
gratefully acknowledged for supplying the bio-oils. We also acknowledge the Centre de Caractérisation de Matériaux
of Université de Sherbrooke for characterization analyses and Mr. Guillaume Hudon and Mr. Yves Pépin of RioTinto
Iron and Titanium (Sorel-Tracy, Quebec, Canada) for UGSO supply. The present work was supported financially
by BioFuelNet Canada.
Author Contributions: This manuscript represents most of the work done by the first author in relation with
his Master Thesis project. Amine Bali has performed all experimental work under the scientific supervision
of Nicolas Abatzoglou. He has also produced the first draft of the manuscript. Jasmin Blanchard, second
author, has contributed technically in adopting the most appropriate experimental protocols and in the scientific
interpretation of the results. Mostafa Chamoumi, third author, co-inventor with Nicolas Abatzoglou of the
catalytic formulations tested has also contributed technically in adopting the most appropriate experimental
protocols and in the scientific interpretation of the results. Nicolas Abatzoglou, the corresponding author, is the
scientific and technical Director of the R&D program, within which this project takes place. He has contributed in
choosing the experimental protocols, the catalytic formulations and he followed weekly the work; he has also
worked with the first author in reviewing the first draft and finalizing the manuscript.
Conflicts of Interest: The authors declare no conflict of interest.

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