Hydrotreating of Jatropha-derived Bio-oil over Mesoporous Sulfide Catalysts to Produce Drop-in Transportation Fuels

The bio-oil was largely produced by thermal pyrolysis of Jatropha-derived biomass wastes (denoted as Jatropha bio-oil) using a pilot plant with a capacity of 20 kg h-1 at Thailand Institute of Scientific and Technological Research (TISTR), Thailand. Jatropha bio-oil is an unconventional type of bio-oil, which is mostly composed of fatty acids, fatty acid methyl esters, fatty acid amides, and derivatives, and consequently, it contains large amounts of heteroatoms (oxygen ~20 wt.%, nitrogen ~ 5 wt.%, sulfur ~ 1000 ppm.). The heteroatoms, especially nitrogen, are highly poisonous to the metal or sulfide catalysts for upgrading of Jatropha bio-oil. To overcome this technical problem, we reported a stepwise strategy for hydrotreating of 100 wt.% Jatropha bio-oil over mesoporous sulfide catalysts (CoMo/γ-Al2O3 and NiMo/γ-Al2O3) to produce drop-in transport fuels, such as gasoline- and diesel-like fuels. This study is very different from our recent work on co-processing of Jatropha bio-oil (ca. 10 wt.%) with petroleum distillates to produce a hydrotreated oil as a diesel-like fuel. Jatropha bio-oil was pre-treated through a slurry-type high-pressure reactor under severe conditions, resulting in a pre-treated Jatropha bio-oil with relatively low amounts of heteroatoms (oxygen < 20 wt.%, nitrogen < 2 wt.%, sulfur < 500 ppm.). The light and middle distillates of pre-hydrotreated Jatropha bio-oil were then separated by distillation at a temperature below 240 °C, and a temperature of 240–360 °C. Deep hydrotreating of light distillates over sulfide CoMo/γ-Al2O3 catalyst was performed on a batch-type high-pressure reactor at 350 °C and 7 MPa of H2 gas for 5 h. The hydrotreated oil was a gasoline-like fuel, which contained 29.5 vol.% of n-paraffins, 14.4 vol.% of iso-paraffins, 4.5 vol.% of olefins, 21.4 vol.% of naphthene compounds and 29.6 wt.% of aromatic compounds, and little amounts of heteroatoms (nearly no oxygen and sulfur, and less than 50 ppm of nitrogen), corresponding to an octane number of 44, and it would be suitable for blending with petro-gasoline. The hydrotreating of middle distillates over sulfide NiMo/γ-Al2O3 catalyst using the same reaction condition produced a hydrotreating oil with diesel-like composition, low amounts of heteroatoms (no oxygen and less than 50 ppm of sulfur and nitrogen), and a cetane number of 60, which would be suitable for use in drop-in diesel fuel.


Introduction
Biomass is one of the most abundant natural resource, which has supplied around 10% of annual primary energy consumption corresponding to a capacity of 50 EJ/yr globally in 2006-2007 [1][2][3].It is generally agreed that the chemicals and fuel with low carbon footprint can be synthesized by conversion of biomass using various catalytic strategies, which contribute to the reduction of CO2 emission and consequent avert global warming [4][5][6][7][8][9][10].For example, the biodiesel fuel (BDF), which is so-called the firstgeneration biofuel, can be synthesized by base-catalyzed transesterification of refined vegetable oils with methanol, and it has been extensively used in the transport sector, particularly in America, European Union and ASEAN counties [6,[11][12][13][14][15][16].However, it has caused a new environmental problem in waste biomass treatment, such as discarded kernel shells and husks, which are massively produced as byproducts in the BDF industry.
Recent studies have focused on post-treatment and utilization of those biomass wastes into valuable products, such as gasification to produce syngas, liquification to produce chemicals and fuels, and chip production for thermal power generation [7,17].Similar to biomass gasification and liquification, bio-oil can be synthesized by thermal conversion of biomass, the wastes especially, through the catalytic pyrolysis or non-catalytic pyrolysis technology, and therefore it contains large amounts of heteroatom-containing 5 hydrocarbons, oxygen and sulfur especially, water and unwanted impurities which were highly associated with the feedstocks and the processing parameters used in the pyrolysis and condensation steps [18][19][20][21].The subsequent upgrading of bio-oil through hydrotreating technology using metal catalysts, such as Pd/C, or sulfide catalysts, such as Co-or Ni-promoted MoS2/γ-Al2O3, is required to remove the heteroatoms, resulting in clean and drop-in biofuel with composition and fuel property closed to petro-fuels [22].
Unfortunately, the heteroatoms, water and unwanted impurities, which are originally presented in the bio-oil, poison the active sites of metal and sulfide catalysts, causing serious catalyst deactivation and consequently reducing the quality of hydrotreated biooil [23][24][25][26][27][28][29][30].Yoshimura et al. reported that the sulfide NiMo catalysts were deactivated by the oxygen-containing compounds due to the oxidation of active sites [23].Laurent and Delmon showed that the deoxygenation of model compounds of bio-oils over CoMo and NiMo catalysts was strongly inhibited in the presence of water and ammonia [24].There is still room for development of innovative catalytic process using advanced catalysts with high resistance to heteroatoms, which can produce clean and drop-in fuel for directly formulating with petro-fuels.
Our recent study demonstrated that Jatropha bio-oil could be synthesized by thermal pyrolysis of waste Jatropha biomass (a mixture of kernel shell and husk) using a Pilot Plant with a capacity of ca.20 kg/h at TISTR, Thailand [19].The Jatropha bio-oil is an unconventional bio-oil with a high concentration of nitrogen (ca. 5 wt%) and relatively low concentrations of oxygen (ca.20 wt%) and sulfur (<1000 ppm), which is mostly consisted of fatty acids, fatty acid methyl esters, fatty acid amides and their derivatives (> 50 wt%) in addition to other light organic compounds incorporated with heteroatoms.
It is different from conventional bio-oils with high oxygen content (ca.20-40 wt%) and low sulfur and nitrogen contents (<1 wt%), which were derived from cedar or pine biomass waste, and mostly consisted of carbohydrates and phenolic compounds.In the upgrading process, the upgraded catalysts as aforementioned were immediately deactivated by high concentration of nitrogen-containing compounds when Jatropha biooil was directly used as a feedstock (Scheme 1(a)).To prevent catalyst deactivation, our previous study demonstrated a co-processing method for upgrading of Jatropha bio-oil co-fed with petroleum distillates over sulfide CoMo and NiMo catalysts under severe conditions (330-350 o C and 5-7 MPa of H2) [31].The diesel-like fuel with nearly no heteroatoms (sulfur, oxygen and nitrogen < 10 ppm) could be obtained by hydrotreating of oil feedstock containing ca. 10 wt% of Jatropha bio-oil and ca.90 wt% of light gas oil.
In this study, a stepwise strategy was reported for hydrotreating of 100 wt% Jatropha biooil over sulfide catalysts to produce drop-in transport fuels including gasoline-and diesel-7 like fuels (Scheme 1(b)).The Jatropha bio-oil was pre-treated by a slurry bed reactor at 400 o C and 7 MPa of H2 using waste NiMo/γ-Al2O3 catalyst, followed by distillation.The clean and drop-in transport fuels were then obtained by hydrotreating of pre-treated distillates over fresh CoMo/γ-Al2O3 or NiMo/γ-Al2O3 catalysts using a high-pressure stainless-steel batch-type reactor under severe conditions.Influence of catalysts and processing parameters on the composition and fuel property of upgraded Jatropha biooils was reported.

Results and discussion
The sulfide CoMo/γ-Al2O3 or NiMo/γ-Al2O3 catalysts were prepared by the same procedures as reported in our previous study [30], and their structural properties were and nitrogen (ca.0.1 wt%) [19,20].However, Jatropha bio-oil is mostly composed of fatty acids, fatty acid methyl esters, fatty acid amides and derivatives, presumably due to that Jatropha oil is partly remained in the waste Jatropha biomass after the oil extraction.As a result, Jatropha bio-oil contains high concentration of nitrogen (ca. 5 wt%), relatively high concentration of sulfur (ca.1000 ppm) and relatively low concentration of oxygen (ca.20 wt%).The heteroatoms, nitrogen especially, are extremely poisonous to metal and sulfide catalysts used in the upgrading process [].In scheme 1(a), the preliminary studies showed that direct hydrotreating of Jatropha bio-oil over sulfide and metal catalysts produced low-quality hydrotreated bio-oils with high heteroatoms, which was inapplicable for use in fuel oil blending, even if the severe conditions were used [unpublished results].In other worlds, the sulfide and metal catalysts were immediately deactivated by strong adsorption of heteroatoms on the catalytically active sites, nitrogen especially, in the upgrading process.To solve this technical problem, we proposed a stepwise strategy for upgrading of Jatropha bio-oil over sulfide catalysts to produce dropin biofuels (see Scheme 1(B) and Fig. 3).Jatropha bio-oil was pre-treated through a slurry-type high pressure reactor at 400 o C and 7 MPa of H2 for 2 h using 1 wt% of waste NiMo catalyst, resulting in a pre-treated Jatropha bio-oil with relatively low concentrations of heteroatoms (oxygen < 20 wt.%, nitrogen < 2 wt.%, sulfur < 500 ppm.).
The yield of pre-treated Jatropha bio-oil was around 65%.The pre-treated bio-oil was Deep hydrotreating of light distillates over the sulfide CoMo/γ-Al2O3 catalyst was performed on a stainless-steel batch-type reactor at 350 o C and 7 MPa of H2 for 5 h (Figure 3(a)).The hydrotreating oil was characterized by GC-FID instrument and elemental analysis.Figure 4 shows that the hydrotreating oil is a gasoline-like fuel, except a small portion of paraffins with carbon number higher than 10.Table 1 shows that the hydrotreated oil contains 29.5 vol.% of n-paraffins, 14.4 vol.% of iso-paraffins, 4.5 vol.% of olefins, 21.4 vol.% of naphthene compounds, 29.6 wt.% of aromatic compounds and little amounts of heteroatoms (nearly no oxygen and sulfur, and ca.50 ppm of nitrogen), corresponding to an octane number of 44.This result suggests that the hydrotreating oil would be suitable for blending with petro-gasoline.On the other hand, the paraffins with carbon number higher than 10 can be separated from the hydrotreating oil by further distillation, and it would be suitable for use in kerosene [34].
Deep hydrotreating of middle distillates over sulfide NiMo/γ-Al2O3 catalyst was performed by a large-scale batch-type high pressure reactor under the same reaction condition.(Figure 3(b)).In a typical synthesis, a 100 g of middle distillates was mixed with 40 g of sulfide NiMo/γ-Al2O3 catalyst under an atmosphere of H2, followed by heating to 350 o C in 1 hr under pressured atmosphere of H2 (7 MPa) and vigorously stirring.After 350 o C for 5 h, the hydrotreating oil was cooled to ambient condition and corrected by filtration.The yield of hydrotreating oil was 55.2%.The sulfur and nitrogen concentrations of hydrotreating oil were smaller than 10 and 50 ppm, respectively.In catalyst is a clean and drop-in diesel-like biofuel, which can be applicable for use in high blends.

Preparation and characterization of sulfide catalysts
The sulfide catalysts were prepared by incipient impregnation method.The cobaltand nickel-promoted molybdenum aqueous solutions (denoted at CoMo(cit) and NiMo(cit), respectively) were freshly prepared by the procedures as described in our previous study [30].For the preparation of freshly prepared CoMo(cit) and NiMo(cit) aqueous solution, the molybdenum oxide (Wako) was dispersed in hot deionized water

Conclusions
Jatropha bio-oil was mostly composed of fatty acids, fatty acid methyl esters, fatty acid amides and derivatives, corresponding to high concentrations of heteroatoms, nitrogen especially.To overcome the catalyst deactivation by those heteroatoms, we had developed a stepwise strategy for hydrotreating of 100 wt% Jatropha bio-oil over sulfide

Figure 5 ,
Figure 5, the GC analysis equipped with FID and mass detectors indicates that the

(C and 7
ca. 90 o C) for 12 h under stirring.To this solution, the cobalt nitrate (or nickel nitrate) and citric acid were slowly added under heating and stirring conditions, resulting in freshly prepared CoMo(cit) or NiMo(cit) aqueous solution with molar composition of 1 MoO3: 0.5 CoO (or NiO): 0.58 C6H8O7: 1.67 H2O.The extruded γ-Al2O3 particle as the supporting materials were dried at 120 o C for 6 h prior to the impregnation.For the preparation of sulfide catalysts, the CoMo(cit) and NiMo(cit) aqueous solutions were Preprints (www.preprints.org)| NOT PEER-REVIEWED | Posted: 1 April 2019 doi:10.20944/preprints201904.0020.v1Peer-reviewed version available at Catalysts 2019, 9, 392; doi:10.3390/catal9050392treatment of Jatropha bio-oil was performed in a slurry bed reactor using waste sulfide NiMo/γ-Al2O3 catalyst (1 wt%) at 400 o C and 7 MPa of H2 for 2 h.The pre-treated Jatropha bio-oil was distilled and separated into three fractions: (i) light distillates (< 240 o C), (ii) middle distillates (240-360 o C) and (iii) heavy distillates (> 360 o C).The yield of light distillates which composition was closed to gasoline was 21 wt% and that of middle distillates which composition was closed to diesel was around 59 wt%., In this study, we focused on the deep hydrotreating of light and middle distillates over sulfide CoMo/γ-Al2O3 or NiMo/γ-Al2O3 catalysts into clean and drop-in biofuels (Figure 3).The deep hydrotreating was performed on a high-pressure stainless-steel batch-type reactor at 350 o MPa of H2 for 5 h using a catalyst/oil weight ratio of 0.4.The hydrotreated oils were analysed by Agilent 6890 GC-FID instrument equipped with mass detector, elemental analysis of carbon, nitrogen, hydrogen, sulfur, and the fuel property.

PreprintsC, 7
(www.preprints.org)| NOT PEER-REVIEWED | Posted: 1 April 2019 doi:10.20944/preprints201904.0020.v1Peer-reviewed version available at Catalysts 2019, 9, 392; doi:10.3390/catal9050392catalysts to produce clean and drop-in transport biofuels, such as gasoline-and diesel-like biofuels.This stepwise strategy included (i) pre-treatment of Jatropha bio-oil over waste NiMo/γ-Al2O3 catalyst (1 wt%) using a slurry-type reactor under severe condition (400 o MPa of H2, 2 h), (ii) distillation of pre-treated Jatropha bio-oil into light distillates (Td < 240 o C) and middle distillates (Td = 240-360 o C), (iii) deep hydrotreating of light and middle distillates over sulfide CoMo/γ-Al2O3 and NiMo/γ-Al2O3 catalysts (40 wt%) using a batch-type reactor under severe condition (350 o C, 7 MPa of H2, 5 h) to produceclean and drop-in biofuels.Among the step (iii), we found that the hydrotreating oil with gasoline-like composition and an octane number of 44 could be synthesized by deep hydrotreating of light distillates over sulfide CoMo/γ-Al2O3 catalyst, and it would be suitable for partly blending with petro-gasoline.On the other hand, the hydrotreating oil with diesel-like composition and a cetane number of 60.8 could be produced by deep hydrotreating of middle distillates over sulfide NiMo/γ-Al2O3 catalyst, and it would be suitable for use in diesel engine directly.Moreover, the waste NiMo/γ-Al2O3 catalyst could be recycled and used again in the step (i), which reduced the environmental pollution and production cost.