Next Article in Journal
Vanadium-Doped Bi2S3@Co1−xS Heterojunction Nanofibers as High-Capacity and Long-Cycle-Life Anodes
Previous Article in Journal
Short-Term Energy Generation Forecasts at a Wind Farm—A Multi-Variant Comparison of the Effectiveness and Performance of Various Gradient-Boosted Decision Tree Models
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Energies
Volume 17
Issue 23
10.3390/en17236195
energies-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Highly Efficient Process for Producing a Jet-A1 Biofuel Component Through Hydroprocessing Soybean Oil over Ni and Pt Catalysts

by
Marek Główka
1,2,*,
Jan Krzysztof Wójcik
1,
Przemysław Boberski
1,
Piotr Józef Woszczyński
3 and
Ewa Sabura
3
1
High Pressure Processes Research Group, Lukasiewicz Research Network—Institute of Heavy Organic Synthesis “Blachownia”, Energetykow 9, 47-225 Kedzierzyn-Kozle, Poland
2
Faculty of Chemistry, PhD School, Silesian University of Technology, Akademicka 2a, 44-100 Gliwice, Poland
3
Analytics Research Group, Lukasiewicz Research Network—Institute of Heavy Organic Synthesis “Blachownia”, Energetykow 9, 47-225 Kedzierzyn-Kozle, Poland
*
Author to whom correspondence should be addressed.
Energies 2024, 17(23), 6195; https://doi.org/10.3390/en17236195
Submission received: 3 October 2024 / Revised: 21 October 2024 / Accepted: 29 November 2024 / Published: 9 December 2024
(This article belongs to the Section I1: Fuel)
Browse Figures
Versions Notes

Abstract

This study presents an efficient process for producing sustainable aviation fuel (SAF) from soybean oil through hydrodeoxygenation (HDO) and hydroisomerization (HI). The research utilized a commercial nickel catalyst for the HDO step, and a newly developed platinum catalyst supported on SAPO-11 zeolite for the hydroisomerization (HI) stage. The process parameters, including temperature and pressure, were optimized to maximize conversion efficiency and meet ASTM D7566 standards. The results indicate that the HDO process using the nickel catalyst achieved a high yield of n-alkanes (97.8% ± 0.4%) with complete conversion of triglycerides. In the subsequent hydroisomerization step, the platinum catalyst demonstrated excellent selectivity for Jet-A1 fuel, yielding a bio-jet fraction of 87.5% ± 1.6% in a 200 h continuous test. This study also highlights the minimal coking phenomena and high catalyst stability throughout the process. This work suggests that soybean oil, as a readily available feedstock, could significantly contribute to the production of SAF and reduce greenhouse gas emissions in the aviation sector. Additionally, the optimization of temperature and pressure conditions is crucial for enhancing the yield and quality of the final bio-jet product.

1. Introduction

In 2021, the aviation sector was responsible for the generation of 900 million metric tons of CO2, representing approximately 2.5% of the global total of CO2 emissions. Projections suggest that, with the growing demand for air transport, CO2 emissions could increase to 5% by 2050 [1]. Moreover, the utilization of conventional jet fuel has an adverse impact on the environment through the emission of nitrogen oxides (NOx), sulfur compounds, and carbon monoxide (CO), which contribute to climate change and ozone layer depletion. Consequently, Regulation 2023/2405 of the European Parliament (ReFuelEU Aviation) has mandated that aviation fuel producers incorporate sustainable aviation fuel (SAF) into their products, with a minimum of 2% SAF content by 2025, increasing to 70% by 2050 [2]. Fuel costs, accounting for 28% of airline expenses, are driving the industry to find strategies to reduce environmental impacts and lower fuel costs [3]. The most promising solution to the challenges associated with fossil fuels is the production of aviation fuel derived from biomass, commonly referred to as bio-jet fuel. The primary pathways for the production of bio-components for aviation fuels include the hydroconversion of vegetable oils (the hydrodeoxygenation of triglycerides followed by hydroisomerization) [4], the ATJ process (alcohol-to-jet, involving alcohol dehydration followed by oligomerization) [5], biomass conversion through gasification and Fischer–Tropsch synthesis, followed by hydrocracking [6], and the STJ process (sugar-to-jet, involving multiple catalytic conversions of sugars) [7]. Figure 1 illustrates the commercialized synthesis pathways for sustainable aviation fuel (SAF).
In the context of aviation fuels, the technology for the hydroconversion of vegetable oils to jet fuels (Annex II and VII) represents the most promising direction due to the availability of raw materials and an almost zero-waste production method. This two-step process involves the hydrodeoxygenation of vegetable oils (HDO) to n-alkanes, followed by the hydroisomerization of n-alkanes (HI) into branched hydrocarbons, the presence of which allows for the requirements of freezing point. In the hydrodeoxygenation process, n-alkanes, primarily in the C15–C18 range, water, and optionally carbon dioxide and carbon monoxide are produced [15], depending on the reaction pathway via hydrodeoxygenation, hydrodecarboxylation, or hydrodecarbonylation [12]. In addition to the main reaction, there are also side reactions where methane, ethane, and propane are formed [16]. Ni-Mo [17] or Ni-Co [18] catalysts supported on alumina or silica are used. These catalysts are particularly effective when utilizing feedstocks with elevated sulfur content. In the case of vegetable oils, the levels of sulfur and nitrogen impurities are low, allowing for the use of more cost-effective nickel-based catalysts. They are used due to the high active metal density, which allows the HDO process to be carried out at lower temperatures and pressures. Nickel’s broad d-band and the high density of energy levels near the crystal lattice promote the efficient adsorption and activation of H2 molecules and oxygen-containing functional groups. Nonetheless, the characteristics of the feedstock—such as purity, composition, and molecular weight distribution—play a crucial role in process optimization. To achieve a balance between high yield and product quality, it is essential to fine-tune operational parameters, not only to avoid localized overheating or “hot spots” but also to prevent excessive cracking of the hydrocarbon chains, which can lower the overall efficiency and lead to undesirable by-products.
In the hydroisomerization reaction, bifunctional catalysts are employed, operating through a mechanism in which alkylcarbenium ions are intermediate products (Figure 2). These alkylcarbenium ions are formed via the dehydrogenation of the alkane on a noble metal, followed by the protonation of the alkene on a Brønsted acid site. In this process, noble metal catalysts such as Pt [19] or Pd [20], supported on synthetic zeolites like ZSM-5, SAPO-11, or MCM-41, are utilized. A typical schematic of the two-step technology for producing aviation bio-additives is presented in Figure 2.
Currently, three primary technologies for the processing of vegetable oils into biofuel components, developed by UOP, Neste Oil, and Axens, are available commercially [4]. These technologies are in most cases a combination of biodiesel production with a slight percentage of bio-jet, largely due to the difficulties associated with obtaining aviation fuel components that meet the stringent requirements, particularly the low freezing point necessary for jet fuel. In response to these challenges, ongoing research is increasingly directed toward the development of innovative technologies that offer enhanced catalytic properties, improved efficiency, and optimized operational costs. Hengsawad et al. [21] achieved a yield of 33% for sustainable aviation fuel (SAF) using hydrogenated Jatropha oil with a Pt/H-Y zeolite catalyst under the conditions of T = 310 °C, pH2 = 3.1 MPa, and Liquid Hourly Space Velocity (LHSV) = 1.0 h−1 Hengsawad. In contrast, Brandao et al. [22] reported a significantly higher SAF yield of 83.4% using coconut oil with a Pt/SAPO-11 hydroisomerization catalyst under the conditions of T = 350 °C, pH2 = 3 MPa, and LSHV = 2 h−1. Based on the scientific literature, it can be concluded that there is a need to develop a catalyst for the hydroisomerization process that will enhance the efficiency of producing sustainable aviation fuel, especially under lower process conditions. This improvement would enable a reduction in both process costs and the negative environmental impact.
The objective of this study was to improve the efficiency of the HEFA process for soybean oil by optimizing the process parameters of a Trickle-Bed Reactor (TBR), such as temperature and pressure, in the hydrodeoxygenation and hydroisomerization stages. A commercial nickel catalyst was used for the HDO process, along with a newly developed hydroisomerization catalyst composed of 0.5% Pt, Al2O3, and SAPO-11, with the addition of 3% PEG-4 as a pore modifier. The catalyst was characterized by N2 sorption, and thermogravimetry before and after the test. Based on the conducted experiments, the stability of both stationary catalysts was assessed, along with their impact on the efficiency of producing sustainable aviation fuels that comply with the key parameters outlined in the ASTM D7566 standard [23]. Reaction products were characterized using Gas Chromatography–Mass Spectrometry (GC, GC/MS) methods.

2. Materials and Methods

2.1. Materials

Aluminum hydroxide—Pural SB was purchased from Sasol, Hamburg, Germany; SAPO-11 zeolite was purchased from Tianjin Hutong Global Trade, Tianjin, China; nitric acid (V) (65%) p.a. was purchased from Chempur, Karlsruhe, Germany; dihydrogen hexachloroplatinate (IV) hexahydrate 99.95% was purchased from ThermoFischer GmbH, Warszawa, Poland; additionally, Polikol 200 (PEG-4) was supplied by PCC Rokita, Brzeg Dolny, Poland; a commercial nickel catalyst was purchased from Clariant, Munich, Germany; commercial degummed soybean oil was used.

2.2. Hydrodeoxygenation Process

The hydrodeoxygenation process for crude soybean oil was conducted in a high-pressure flow reactor system with a stationary bed of 200 cm3 catalyst. The system setup is illustrated in Figure 3. It also includes a raw material tank, a high-pressure pump (Leva, Warszawa, Poland), a hydrogen mass flow regulator (Bronkhorst, AK Ruurlo, The Netherlands), and a pressure regulator (Swagelok, Wrocław, Poland). The hydrodeoxygenation reactions were carried out in temperatures ranging from 220 to 340 °C, pressure from 2 to 10 MPa, and LHSV (0.25 to 1) at a GHSV of 600. A commercially available nickel catalyst on silica-alumina support was used. The catalyst is dedicated to sulfur-free conditions and was supplied in the form of extrudates with a diameter of ~2 mm. The obtained n-alkanes were evaluated via GC method, using a PerkinElmer Clarus 500 instrument (Shelton, CT, USA) equipped with a flame ionization detector and a nonpolar capillary column DB-1 (60 m × 0.32 mm × 0.5 µm), and GC/MS method using the Gas Chromatograph 7890A GC System by Agilent Technologies (Santa Clara, CA, USA) equipped with the MSD type 5977B mass detector and a computer station with Mass Hunter software version 10.1.49.0.

2.3. Synthesis of Hydroisomerization Catalyst

Pural SB was mixed in wt. ratio 1:1 with zeolite (SAPO-11) to obtain the carrier for the hydroisomerization process, ensuring uniform distribution (of active phase. Subsequently, solid substrates were mixed with 5% of Polyglycol 200 (PCC Rokita, Brzeg Dolny, Poland). Additionally, 40 g of 3% nitric acid was introduced per 100 g of the Pural/zeolite to initiate gelling and achieve a homogeneous paste, according to the procedure provided by the Pural SB supplier (Sasol, Hamburg, Germany). The thoroughly blended mixture resulted in increased viscosity and was then pressed into extrudates with a diameter of approximately 1.6 mm. The obtained carrier was dried for 24 h at room temperature, then for 24 h at 130 °C, and finally calcinated for 10 h at 450 °C with a temperature rise of 2 °C/min.
The active phase was loaded using the incipient wetness method. Before the impregnation, the adsorptive capacity of the carrier was evaluated to determine the amount of water required for the impregnation process. The catalyst was impregnated with hexachloroplatinic acid (IV) solution to obtain a 0.5 % wt. Pt loading. The catalyst was dried for 24 h at 130 °C, and subsequently calcined for 10 h at 500 °C with a temperature rise of 2 °C/min. The Pt content in the catalyst was confirmed using the ICP-OES method.

2.4. Hydroisomerization Process

The hydroisomerization process for the crude soybean oil was conducted in a high-pressure flow reactor system with a stationary bed of 50 cm3. The system setup is illustrated in Figure 3. It also includes a raw material tank, a high-pressure pump (Knauer Azura, Berlin, Germany), a hydrogen mass flow regulator (Bronkhorst), and a pressure regulator (Swagelok). Hydroisomerization studies investigated the influence of temperature ranging from 260 to 340 °C, pressure from 2 to 5 MPa, and LHSV (0.25 to 1) at a GHSV of 100. Following the process, the catalyst was dried in the presence of hydrogen to remove any residual reactants. The obtained biocomponent was evaluated via GC method using a Gas Chromatograph 6890N GC System by Agilent Technologies equipped with a flame ionization detector and nonpolar capillary column ZB-5HT Inferno (15 m × 0.25 mm × 0.1 µm). The GC/MS method was carried out using the Gas Chromatograph 7890A GC System by Agilent Technologies equipped with the MSD type 5977B mass detector and a computer station with Mass Hunter software.

2.5. Catalyst Characterization

2.5.1. Low-Temperature Nitrogen Adsorption Method

The specific surface area and porosity of the catalyst samples were determined via nitrogen adsorption at −196.15 °C using a Micromeritics ASAP 2060 Surface Area and Porosity Analyzer (Norcross, GA, USA) according to the BET method, with at least five data points with relative pressures ranging from 0.05 to 0.30 p/p0. The total pore volume was determined at p/p0 = 0.7. Prior to measurements, the samples (100 mg) were degassed through heating in a nitrogen atmosphere at 250 °C for 24 h.

2.5.2. Inductively Coupled Plasma–Optical Emission Spectroscopy (ICP-OES)

Catalyst samples (200 mg) were homogenized and then subjected to mineralization in a PerkinElmer Titan MPS pressure digester (Shelton, CT, USA) using aqua regia solution in triplicate. The prepared samples were subsequently analyzed for Pt content using a PerkinElmer Avio 200 instrument at a wavelength of 265.945 nm.

2.5.3. Thermogravimetry

Thermogravimetric analysis of catalysts (TG) was conducted using a Mettler Toledo TGA 2 System (Warszawa, Poland). Measurements were performed on analytical samples weighing 20–30 mg, placed in an open platinum crucible (Pt70 μL, without lid). The analysis was carried out in the temperature range from 30 °C to 1100 °C, with the heating rate of 10 °C·min−1, under a nitrogen or air atmosphere with a flow rate of 100 mL/min. The thermograms were analyzed with the use of the STARe Thermal Analysis Software (version 15.00).

3. Results

3.1. Hydrodeoxygenation of Degummed Soybean Oil

Most soybean oils used in biofuel production undergo a degumming process aimed at removing phosphorus-containing compounds, such as phosphatides or phospholipids. These phospholipids can exist in two forms: hydratable, which can be removed with water, and non-hydratable, which require the use of mineral acids or enzymes, among other methods [24]. In the first stage of refining, both types of phospholipids are removed, which is crucial for ensuring the oil’s quality for further applications.
Degummed soybean oil is widely used in the food industry. Additionally, it serves as a renewable raw material in the production of plasticizers, soy candles, paints, and crayons. Due to its low acid value, soybean oil also plays a significant role as a raw material in biodiesel production, making it a competitive resource in the biofuel industry [25]. Table 1 presents the fatty acid profiles of soybean oil, where polyunsaturated fatty acids dominate, with a predominance of C18 fatty acids.
Degummed soybean oil was also characterized in terms of its physicochemical properties. The results are presented in Table 2.
Based on the results, it can be concluded that the soybean oil used contains a low amount of free fatty acids, as confirmed by the low acidic number of 0.78 mgKOH/g. This value is typical for oils intended for biodiesel production, indicating good oil stability during storage and processing. The iodine number indicates a high level of unsaturated bonds in the soybean oil. This suggests that, compared to other vegetable oils such as rapeseed or palm oil, a greater usage of hydrogen is required to hydrogenate the double bonds to n-paraffins.
The specific gravity and viscosity of the oil, 0.919 g/cm3 and 32.18 mm2/s, respectively, do not allow the use of a high-pressure HPLC pump without the necessity of heating the dosing line.
The HDO reaction of an oil is an highly exothermic process, where the high iodine number of the feedstock may result in overheating of the catalyst and so-called hot-spots. This is a challenging technological issue [27]. Such local overheating may lead to coking and carbon deposition on the catalyst surface, negatively impacting its catalytic activity. One way to prevent such a problem is to circulate the product in order to dilute the volumetric heat, or to use catalysts that are more resistant to coking.
The aim of this study is to provide data on how these process conditions, which are critical for optimizing the HDO process and improving product quality, influence both the catalytic performance and product distribution [28].
Figure 4 and Figure 5 show the effects of temperature (220–340 °C) and hydrogen pressure (2–10 MPa) on the n-alkane yield and the activity of the hydrodeoxygenation (HDO) process for degummed soybean oil using a nickel catalyst.
The above results indicate that higher temperatures significantly increase both the conversion of soybean oil and the yield of n-alkanes and intermediate fatty acids. The increase in temperature leads to a reduction in the amount of tri-, di- and monoglycerides, which is consistent with observations from the literature [29,30]. Higher temperature enhances the kinetic energy of triglyceride molecules, required to overcome the energy barrier in the HDO process.
At a reaction temperature of 340 °C, the yield of n-alkanes (Σn-C14–C18) reached a maximum value of 82.4%. Higher temperatures also led to an increase in iso-alkane content due to the intensification of cracking reactions due to the skeletal rearrangement of hydrocarbons into lighter fractions. Similar findings were reported by Verma et al. [31], who found that increasing the temperature (375–450 °C) promoted the cracking of hydrocarbons within the naphtha range (425 °C), confirming an enhancement in cracking reactions and increased selectivity for isomerization.
The high content of C17 proves that DCO and DCO2 are more favored as a result of the common mechanism of triglyceride decomposition, the β-elimination reaction, in which a triglyceride is converted into a free fatty acid and an unsaturated diglyceride. The diglyceride must then undergo hydrogenation before further β-elimination occurs, releasing another molecule of fatty acid. The final stage of hydrogenation and β-elimination results in the release of the third fatty acid molecule along with propane. This mechanism is crucial for understanding triglyceride conversion processes, as β-elimination influences the selectivity of the final products [32].
Hydrogen pressure also plays an important role in the deoxygenation process. As the pressure increases, both the conversion and the number of n-alkanes and iso-alkanes increases. Sotelo-Boyas et al. observed a gradual increase in selectivity toward HDO as the pressure was raised from 5 to 11 MPa. Their studies also noted a decrease in the proportion of heavy fractions in favor of lighter C5–C12 fractions, suggesting that higher pressures promote a greater degree of cracking.
This study has shown the great importance of hydrogen pressure on the process yield. The increase of hydrogen pressure from 2 MPa to 10 MPa allowed an increase in the hydrocarbon content from 22.3 to 93.4. At a hydrogen pressure of 2 MPa, the highest number of triglycerides (25.0%) was observed, compared to 6.7% at 5 MPa and 1.3% at 10 MPa. It was also observed that, as pressure increases, the C16/C15 ratio remains constant at 0.58, indicating that the rates of DCO and DCO2 reactions are not directly dependent on hydrogen pressure. Similar conclusions were drawn by Kubicka et al. [33], who investigated the deoxygenation of rapeseed oil using CoMo catalysts supported on OMA (organized mesoporous alumina), MCM-41, and alumina. They found that both the conversion and the reaction pathway were significantly dependent on the H2 pressure.
In the context of SAF production, the availability of suitable feedstock for the hydroisomerization process represents a significant advantage. Therefore, the conditions of 340 °C and 10 MPa are the most favorable for obtaining a bio-jet fuel without additional recycling or multiplication of HDO reactors. However, it should be noted that the Ni catalyst promotes the DCO pathway, with less favorable atom economy. To ensure that the resulting SAF meets ASTM 7566 standards, the amounts of high-boiling triglycerides, fatty acids, and other by-products from the process must be minimized prior to the hydroisomerization step.
Under the most favorable process conditions of 340 °C and 10 MPa, catalyst stability tests were conducted to assess whether the loss of activity due to catalyst coking occurs over time, and the impact on the composition of the product obtained from the hydrodeoxygenation of degummed soybean oil.
The catalyst stability tests (Figure 6) did not reveal a significant loss of activity in time during continuous operation over 150 h. The organic fraction during the test contained a stable amount of 97.8 ± 0.4% wt. of hydrocarbons, and the overall triglyceride conversion was ~100%. The HDO fraction does not contain any multiple bonds, as the iodine value has changed from 127.40 to 0.78. Based on the GC-MS analysis (Figure 7) of the produced feedstock, it can be concluded that 2% of free fatty acids and mono- and diglycerides are present, while the majority of the composition consists of saturated hydrocarbons. The presence of trace amounts of oxygenated compounds does not interfere with the hydroisomerization process, as the 0.5% Pt/Al2O3 + SAPO-11 + 3% PEG-4 catalyst is also capable of deoxygenating the n-alkane fraction without directly affecting the product, since the resulting water is removed in the light fraction distillation process.
After the catalyst stability test, surface studies were conducted to evaluate changes in pore structure and specific surface area by comparing the results with the fresh catalyst. The results of the nitrogen sorption analysis at −196.15 °C, including BET surface area, pore volume, and pore size distribution, are presented in Figure 8 and Table 3.
Based on Figure 8, the nickel catalyst can be classified as a material with type III adsorption isotherm and H3 hysteresis, suggesting a micro–mesoporous structure. Hysteresis H3 indicates the presence of plate-like or irregular pores, which may affect the adsorption characteristics [34]. Thermogravimetric analysis confirmed the presence of coke, but its quantitative determination is challenging due to overlapping oxidation peaks of nickel present in the catalyst in a partially reduced form. Figure 9 shows the TG and DTG curves for fresh and used nickel catalyst samples in a nitrogen atmosphere. Nevertheless, physicochemical studies indicate that coke formation is likely not permanently detrimental to the catalyst, as the decrease in surface area and pore volume after testing (as shown by SBET and VT values) does not correspond to a significant loss of catalytic activity. This suggests that the coke may be forming in non-critical regions or in the larger pores, leaving the active sites largely unaffected. Additionally, the unchanged average (La) and median (Lm) pore lengths further support the hypothesis that the structural integrity of the catalyst is maintained, and any deposited coke is either weakly bound or easily removed under reaction conditions, preventing significant deactivation.
In summary, n-alkane fractions were produced from degummed soybean oil with high efficiency. This product represents an excellent material for the production of bio-component fractions for aviation fuels. However, its physicochemical properties, such as the freezing point temperature (17.5 °C), indicate that a crucial step of the entire technology is the hydroisomerization process.

3.2. Hydroisomerization of Hydrocarbons Fraction

The formation of SAPO-11 zeolite into a stationary catalyst represents a significant technological challenge, crucial for the development of a selective catalyst for isomerization processes. Due to its unique pore structure and high selectivity, SAPO-11 has proven it usability in the skeletal rearrangement of saturated hydrocarbons [35]. However, for effective industrial application, it must be provided as a stationary catalyst while maintaining its catalytic and mechanical properties. A key issue is to ensure high catalyst selectivity throughout the formation process, as the extrusion or shaping of SAPO-11 can damage its crystalline structure, leading to reduced catalytic activity. In this study, pseudoboehmite was used as a binder, directly mixed with SAPO-11. Under low pH conditions, pseudoboehmite forms a gel, which was extruded using a piston extruder. The calcined support was subsequently impregnated with 0.5% wt. Pt using the incipient wetness impregnation method, which was confirmed via ICP analysis.
The developed catalyst, 0.5% Pt/Al2O3 + SAPO-11 + 3% PEG-4, was utilized to optimize the process parameters for the hydroisomerization of n-alkanes derived from degummed soybean oil, with the objective of maximizing the yield of Jet-A1 fractions in compliance with ASTM 7566 standards. The results obtained from the lab-scale flow reactor are presented in Figure 10.
Figure 10a illustrates the impact of temperature (300–350 °C) on a range of parameters. The conversion of n-C17 (n-heptadecane) is observed to increase significantly with temperature, from approximately 80% at 300 °C to around 95% at 320 °C, and subsequently reaching ~100% at 350 °C. This proves that the activation energy for the endothermic reactions of hydroisomerization and hydrocracking has an important role, becoming more active as the temperature rises [36]. The results show that the yield of bio-jet declines with temperature increase, with the highest yield observed at 300 °C and the lowest at 350 °C, as a consequence of the higher activity of acidic centres responsible for the skeletal rearrangement and thermal cracking of alkanes over hydroisomerization. In the results for the non-selective cracking of n-C17, the hydroisomerization product contains more light hydrocarbons, which are not in the boiling range of the bio-jet fraction. The yield of light fractions <C9 increases with temperature, particularly noted between 320 °C and 350 °C, from approximately 10% to over 40%. The observed increase in <C9 fraction with rising temperature suggests that the process is dominated by excessive cracking rather than selective isomerization. At higher temperatures, the acidic function of bifunctional catalysts becomes more active, driving the production of low molecular weight hydrocarbons. As temperature increases, n-alkanes are more susceptible to cracking, which results in a reduction in their content and the production of lighter hydrocarbons (Figure 11a). The results of this study indicate that the optimal temperature for the hydroisomerization process using the synthesized Pt/SAPO-11 catalyst is approximately 320 °C. At this temperature, the maximum yield of the bio-jet fuel fraction was determined to be 87% by weight, confirming its suitability for sustainable aviation fuel production. Operating at this optimal temperature enhances the yield and process efficiency by minimizing cracking and promoting greater product selectivity. Further optimization, particularly in dedicated pilot units, will allow for the precise determination of hydrogen pressure and temperature, ensuring even higher yields and long-term catalyst stability.
Figure 11b illustrates the effect of pressure (1–5 MPa) on product yield during the hydroisomerization process. As pressure increases, the conversion of n-C17 decreases significantly, dropping from approximately 95% at 1 MPa to around 65% at 5 MPa. This reduction is attributed to enhanced hydrogenation activity at the metal sites of the catalyst under higher pressures, which stabilizes n-alkanes and suppresses cracking. The isomerization process is favored at elevated pressures, resulting in the production of heavier hydrocarbons rather than lighter fractions.
Interestingly, the yield of bio-jet fuel increases with pressure, peaking at approximately 85% at 5 MPa. Higher pressures promote the formation of higher molecular weight hydrocarbons by shifting the reaction equilibrium towards more stable n-alkanes. This behavior is beneficial for bio-jet production, as the process favors heavier fractions over lighter gasoline-type hydrocarbons at elevated pressures. Figure 11b shows a slight decrease in the yield of light fractions as pressure rises, further confirming that high-pressure conditions promote the stability and formation of heavier hydrocarbons. The increased n-alkane content, reaching its maximum at 5 MPa, underscores the pressure’s role in enhancing hydrogenation over cracking.
In conclusion, higher pressure improves the bio-jet yield, although it reduces the conversion of n-C17, demonstrating the trade-off between conversion efficiency and product selectivity under varying pressure conditions.
To determine the optimal process parameters, the effects of temperature and pressure on the formation of n-alkanes, mono-branched alkanes, and multi-branched alkanes were analyzed. These components play a critical role in influencing key properties of Jet-A1 biofuel, particularly the freezing point, which is essential for aviation performance.
Based on Figure 11a, it can be observed that, as temperature increases, the concentration of n-C15 to n-C18 hydrocarbons in the product decreases, while the concentration of C9 to C14 hydrocarbons increases, due to cracking reactions. The cracking process predominantly occurs at the middle of long hydrocarbon chains, resulting in higher concentrations of C9 and C10 in the cracked products, a finding consistent with the results reported by Lin et al. [37]. According to the data shown in Figure 12a, both mono-branched and poly-branched hydrocarbons increase with temperature. At 350 °C, the highest concentrations of both mono- and multi-branched hydrocarbons are observed, corresponding with the lowest content of n-alkanes.
In Figure 11b, it is evident that, as pressure increases, the concentration of n-C15 to n-C18 hydrocarbons rises, while the concentration of C9 to C14 hydrocarbons declines, indicating that higher pressure reduces cracking. Elevated pressures increase the tendency for hydrogen to bond with hydrocarbon radicals, which suppresses the formation of branched isomers. The higher hydrogen concentration at elevated pressures enhances hydrogenation at the metallic sites of the catalyst, stabilizing n-alkanes and reducing their susceptibility to further breakdown into smaller molecules.
To achieve the highest possible content of iso-alkanes, especially multi-branched ones, to meet the desired freezing point requirements, the optimal operating conditions for the 0.5% Pt/Al2O3 + SAPO-11 + 3% PEG-4 catalyst were determined to be 320 °C and 1 MPa. Stability tests were then conducted over a 200 h period, as shown in Figure 13.
The stability tests of the 0.5% Pt/Al2O3 + SAPO-11 + 3% PEG-4 catalyst did not reveal significant changes in its performance, both in terms of process parameters and product composition, during continuous operation over 200 h. A bio-jet fraction yield of 87.5 ± 1.6% was achieved, while the yield of the light fraction was 12.5 ± 0.5%. These results indicate no signs of increased cracking, which could have been attributed to the leaching of the metallic phase of the catalyst, a fact that was further confirmed via ICP-OES analysis.
After the catalyst stability test for the hydroisomerization process, surface studies were conducted to evaluate changes in pore structure and specific surface area by comparing the results with the catalyst before use. The results of nitrogen sorption analysis at −196.15 °C, including BET surface area, pore volume, and pore size distribution, are presented in Figure 14 and Table 4.
Based on Figure 15, the 0.5% Pt/Al2O3 + SAPO-11 + 3% PEG-4 catalyst can be classified as a material with a type III adsorption isotherm and H3 hysteresis, suggesting a micro–mesoporous structure. The H3 hysteresis indicates the presence of plate-like or irregular pores, which may influence adsorption characteristics [25]. Post-process analyses revealed a reduction in micropore content and pore volume, likely due to blockage by product residues and coke, as preliminarily confirmed by changes in pore volume and a decrease in specific surface area.
To confirm the presence of coke, thermogravimetric analysis (TGA) was conducted for both fresh and used 0.5% Pt/Al2O3 + SAPO-11 + 3% PEG-4 catalysts (Figure 15). During the heating of the fresh catalyst, a significant one-step mass loss was observed, primarily related to the release of volatile components, including water evaporation. In contrast, for the used catalyst sample, within the temperature range from 30 °C to approximately 380 °C, three overlapping weight loss stages were observed, corresponding to the evaporation/boiling of volatile components and the thermo-oxidative decomposition of organic compounds from the synthesis process. Above 400 °C, a significant weight loss occurred due to the thermo-oxidative decomposition of the “coked” post-reaction residue.
Based on complementary thermogravimetric (TG) measurements for both fresh and used catalysts, accounting for weight loss in the range of ~380 °C–1100 °C, the amount of coked residue in the catalyst sample after the process was calculated to be 6.0%. Despite the accumulation of coke, the catalyst did not exhibit a significant loss in activity during testing. Remarkably, after subjecting the used catalyst to a regeneration process through calcination, the BET surface area returned almost to its original state, indicating that the catalyst can retain its efficiency and be reused effectively after regeneration.
To obtain the final bio-component for Jet-A1 aviation fuel, the distillation process has to be carried out. The hydroisomerization product, after a 200 h stability test, was subjected to fractional distillation to remove light n-alkanes and iso-alkanes. These compounds negatively impact the fuel properties by lowering the autoignition temperature, which has significant safety implications for aviation fuel use. Additionally, their presence affects other physicochemical parameters, such as viscosity and fuel density. The distillation was conducted within a temperature range of [30–180 °C], and the composition of the obtained distillate was evaluated using Gas Chromatography–Mass Spectrometry (Figure 16).
Based on Figure 16, it can be concluded that there is a lack of a light gasoline fraction (hydrocarbons up to C11), the presence of which in the bio-component could lead to non-compliance with the minimum self-ignition temperature requirement of 38 °C, specified in ASTM 7566. The analysis indicates that the sample has been distilled almost to the C12 hydrocarbon fraction, which likely has a positive effect on the self-ignition temperature. However, this may negatively impact the freezing point temperature. Furthermore, small amounts of C17-C18 hydrocarbons were detected in the bio-component, which may negatively affect the crystallization temperature. Table 5 confirms the compliance with the self-ignition temperature and crystallization temperature, which results from the high degree of isomerization.

4. Discussion

The presented results demonstrate that the synthesized hydroisomerization catalyst is highly effective in producing HEFA additives, fully compliant with Annex II of ASTM D7566.
Theoretically, the HDO process results in the formation of hydrocarbons with the same carbon number as primary fatty acid, but the decarboxylation and decarbonylation result in the removal of one carbon through the formation of carbon monoxide or carbon dioxide. Nonetheless, the formation of CO or CO2 may be advantageous, as it improves the hydrogen usage (instead of the formation of H2O). Furthermore, n-C18 has a boiling value above the required range (~312 °C, in contrast to the final boiling point of 300 °C according to ASTM D7566).
When evaluating catalyst performance in the context of bio-jet production, significant variations in yield have been observed across different studies. In comparison to the current study, the research by Hengsawad et al. [21] and Brandao et al. [22] demonstrated significantly divergent yields of 33% and 83.4%, respectively, utilizing Pt-based catalysts under varying process conditions. However, our synthesized catalyst achieved a bio-jet fraction yield of 87.5 ± 1.6%, demonstrating superior selectivity for hydrocarbons in the Jet-A1 range. These results align with the findings of Verma et al. [31] underscoring the importance of optimizing process parameters—particularly temperature and pressure—in maximizing yield and minimizing unwanted by-products. Furthermore, our catalyst not only meets ASTM D7566 standards but also shows improved stability and reduced coking, making it an excellent candidate for future commercial-scale SAF production.
The hydroisomerization catalyst exhibited excellent activity and maintained stability over a 200 h continuous testing period, highlighting its potential for industrial-scale applications. Notably, the yield of branched alkanes within the optimal boiling range for aviation kerosene (bio-jet) was significant, surpassing the typical outputs where bio-jet is often a minor product. This catalyst opens the door for developing a process where bio-jet fuel becomes the primary output, unlike many existing processes focused on other fractions.
Given the stringent ReFuelEU Aviation regulations, which mandate the inclusion of sustainable components in jet fuels, this approach is not only timely but also crucial for meeting current and future market demands. The technology developed here is poised to address the increasing need for sustainable aviation fuels (SAFs), particularly as industry targets aim for as much as 70% sustainable components by 2050. This work lays the groundwork for addressing the challenges posed by these ambitious goals, particularly in terms of balancing high fuel yields with the necessary cold flow properties required for jet fuels. The catalyst’s robustness, coupled with the ability to tailor the isomerization conditions, offers a flexible solution adaptable to various renewable feedstocks. Further optimization of process parameters, such as hydrogen pressure and temperature, will likely enhance yields and catalyst longevity, ensuring this technology remains competitive in future SAF production landscapes.

5. Conclusions

The article presents research on the production of sustainable aviation fuel from soybean oil using a hydrocatalytic process that includes hydrodeoxygenation (HDO) and hydroisomerization (HI). The study focuses on the utilization of newly developed catalysts, including a commercial nickel catalyst and an innovative platinum catalyst supported on SAPO-11 zeolite. Optimization of catalysts and process conditions, such as temperature, pressure, and flow rate, has led to high conversion efficiency and product quality in compliance with ASTM D7566 standards. In summary, the conducted research provides data for the development of the hydrocatalytic process for the conversion of soybean oil into sustainable aviation fuel with high yield, which can significantly contribute to the reduction of greenhouse gas emissions in the aviation sector.
The experimental results show that the HDO process for soybean oil using the nickel catalyst achieved a yield of n-alkanes at 97.8 ± 0.4% with complete triglyceride conversion. Optimal conditions for the hydroisomerization process using the platinum catalyst allowed for increased selectivity toward the Jet-A1 fraction, which is crucial for aviation applications. The analyses also indicate that the stability of the catalysts was high, resulting in minimal coking phenomena and improved process efficiency. A bio-jet fraction yield of 87.5 ± 1.6% was achieved, while the yield of the light fraction was 12.5 ± 0.5% in a 200 h test.
The availability of soybean oil suggests that such a HEFA additive meeting ASTM D7566 requirements may be a valuable solution for providing sustainable aviation fuels suitable for commercial application. Optimization of process conditions, such as temperature and pressure, significantly affects conversion efficiency and the quality of the final products. It was found that higher temperatures lead to better triglyceride conversion and increased yields of n-alkanes.

Author Contributions

Conceptualization, M.G. and J.K.W.; methodology, M.G.; validation, P.B. and M.G.; data curation, M.G., E.S. and P.J.W.; writing—original draft preparation, M.G.; writing—review and editing, J.K.W.; visualization, M.G. and J.K.W.; funding acquisition, M.G. All authors have read and agreed to the published version of the manuscript.

Funding

This research received a National Centre for Research and Development grant, number LIDER/33/0171/L-12/20/NCBR/2021. This work is supported by the “Implementation doctorate” program financed by the Polish Ministry of Education and Science, edition 5, grant no. DWD/5/0287/2021.

Data Availability Statement

The original contributions presented in the study are included in the article, further inquiries can be directed to the corresponding author.

Conflicts of Interest

The authors declare no conflict of interest.

References

  1. IEA. Aviation. 2022. Available online: https://www.iea.org/energy-system/transport/aviation (accessed on 1 October 2024).
  2. Scheelhaase, J.; Grimme, W.; Maertens, S. EU Trilogue Results for the Aviation Sector—Key Issues and Expected Impacts. Transp. Res. Procedia 2024, 78, 206–214. [Google Scholar] [CrossRef]
  3. Abrantes, I.; Ferreira, A.F.; Silva, A.; Costa, M. Sustainable Aviation Fuels and Imminent Technologies—CO2 Emissions Evolution towards 2050. J. Clean. Prod. 2021, 313, 127937. [Google Scholar] [CrossRef]
  4. Główka, M.; Wójcik, J.; Boberski, P.; Białecki, T.; Gawron, B.; Skolniak, M.; Suchocki, T. Sustainable Aviation Fuel—Comprehensive Study on Highly Selective Isomerization Route towards HEFA Based Bioadditives. Renew. Energy 2024, 220, 119696. [Google Scholar] [CrossRef]
  5. Richter, S.; Kukkadapu, G.; Westbrook, C.K.; Braun-Unkhoff, M.; Naumann, C.; Köhler, M.; Riedel, U. A Combined Experimental and Modeling Study of Combustion Properties of an Isoparaffinic Alcohol-to-Jet Fuel. Combust. Flame 2022, 240, 111994. [Google Scholar] [CrossRef]
  6. Goh, B.H.H.; Chong, C.T.; Ong, H.C.; Seljak, T.; Katrašnik, T.; Józsa, V.; Ng, J.-H.; Tian, B.; Karmarkar, S.; Ashokkumar, V. Recent Advancements in Catalytic Conversion Pathways for Synthetic Jet Fuel Produced from Bioresources. Energy Convers. Manag. 2022, 251, 114974. [Google Scholar] [CrossRef]
  7. Lim, J.H.K.; Gan, Y.Y.; Ong, H.C.; Lau, B.F.; Chen, W.H.; Chong, C.T.; Ling, T.C.; Klemeš, J.J. Utilization of Microalgae for Bio-Jet Fuel Production in the Aviation Sector: Challenges and Perspective. Renew. Sustain. Energy Rev. 2021, 149, 111396. [Google Scholar] [CrossRef]
  8. Chevron Renewable Energy Group. Available online: https://www.regi.com/about (accessed on 28 September 2024).
  9. Weiss, K.R. Sustainable Aviation Fuels (SAF). Available online: https://www.icao.int/Meetings/Stocktaking2020/Documents/ICAO%20Stocktaking%202020%20-%203.3.7%20-%20Kevin%20Weiss.pdf (accessed on 1 October 2024).
  10. Del Paggio, A. IH2* Technology. 2018. Available online: https://bioenergyinternational.com/wp-content/uploads/2018/09/6.Alan_Del-Paggio.pdf (accessed on 1 October 2024).
  11. Shahabuddin, M.; Alam, M.T.; Krishna, B.B.; Bhaskar, T.; Perkins, G. A Review on the Production of Renewable Aviation Fuels from the Gasification of Biomass and Residual Wastes. Bioresour. Technol. 2020, 312, 123596. [Google Scholar] [CrossRef] [PubMed]
  12. de Klerk, A.; Chauhan, G.; Halmenschlager, C.; Link, F.; Montoya Sánchez, N.; Gartley, B.; El-Sayed, H.E.M.; Sehdev, R.; Lehoux, R. Sustainable Aviation Fuel: Pathways to Fully Formulated Synthetic Jet Fuel via Fischer–Tropsch Synthesis. Energy Sci. Eng. 2024, 12, 394–409. [Google Scholar] [CrossRef]
  13. van Dyk, S.; Saddler, J. Progress in Commercialization of Biojet/Sustainable Aviation Fuels (SAF): Technologies and Policies; IEA Bioenergy: Task 39; IEA Bioenergy: Paris, France, 2024; ISBN 9791280907363. [Google Scholar]
  14. Peters, M.A.; Alves, C.T.; Onwudili, J.A. A Review of Current and Emerging Production Technologies for Biomass-Derived Sustainable Aviation Fuels. Energies 2023, 16, 6100. [Google Scholar] [CrossRef]
  15. Ameen, M.; Azizan, M.T.; Yusup, S.; Ramli, A.; Yasir, M. Catalytic Hydrodeoxygenation of Triglycerides: An Approach to Clean Diesel Fuel Production. Renew. Sustain. Energy Rev. 2017, 80, 1072–1088. [Google Scholar] [CrossRef]
  16. Nepomniashchii, A.A.; Buluchevskiy, E.A.; Yurpalov, V.L.; Drozdov, V.A.; Lavrenov, A.V. Hydrodeoxygenation of Vegetable Oil on M/WO3-Al2O3 (M = NiMo, Pt, Pd, Ni) Catalysts for Producing Biofuels. AIP Conf. Proc. 2020, 2301, 020002. [Google Scholar] [CrossRef]
  17. Yoosuk, B.; Sanggam, P.; Wiengket, S.; Prasassarakich, P. Hydrodeoxygenation of Oleic Acid and Palmitic Acid to Hydrocarbon-like Biofuel over Unsupported Ni-Mo and Co-Mo Sulfide Catalysts. Renew. Energy 2019, 139, 1391–1399. [Google Scholar] [CrossRef]
  18. Dabbawala, A.A.; Elmutasim, O.; Baker, M.A.; Siakavelas, G.; Anjum, D.H.; Charisiou, N.D.; Hinder, S.J.; Munro, C.J.; Gacesa, M.; Goula, M.A.; et al. Toward Maximizing the Selectivity of Diesel-like Hydrocarbons from Oleic Acid Hydrodeoxygenation Using Ni/Co-Al2O3 Embedded Mesoporous Silica Nanocomposite Catalysts: An Experimental and DFT Approach. Appl. Surf. Sci. 2023, 640, 158294. [Google Scholar] [CrossRef]
  19. Yang, Z.; Liu, Y.; Zhao, J.; Gou, J.; Sun, K.; Liu, C. Zinc-Modified Pt/SAPO-11 for Improving the Isomerization Selectivity to Dibranched Alkanes. Cuihua Xuebao/Chin. J. Catal. 2017, 38, 509–517. [Google Scholar] [CrossRef]
  20. Veriansyah, B.; Han, J.Y.; Kim, S.K.; Hong, S.-A.; Kim, Y.J.; Lim, J.S.; Shu, Y.-W.; Oh, S.-G.; Kim, J. Production of Renewable Diesel by Hydroprocessing of Soybean Oil: Effect of Catalysts. Fuel 2012, 94, 578–585. [Google Scholar] [CrossRef]
  21. Hengsawad, T.; Srimingkwanchai, C.; Butnark, S.; Resasco, D.E.; Jongpatiwut, S. Effect of Metal-Acid Balance on Hydroprocessed Renewable Jet Fuel Synthesis from Hydrocracking and Hydroisomerization of Biohydrogenated Diesel over Pt-Supported Catalysts. Ind. Eng. Chem. Res. 2018, 57, 1429–1440. [Google Scholar] [CrossRef]
  22. Brandão, R.D.; de Freitas Júnior, A.M.; Oliveira, S.C.; Suarez, P.A.Z.; Prauchner, M.J. The Conversion of Coconut Oil into Hydrocarbons within the Chain Length Range of Jet Fuel. Biomass Convers. Biorefin. 2021, 11, 837–847. [Google Scholar] [CrossRef]
  23. ASTM D7566-22; Standard Specification for Aviation Turbine Fuel Containing Synthesized Hydrocarbons. ASTM International: West Conshohocken, PA, USA, 2022.
  24. Fan, X.; Burton, R.; Austic, G. Conversion of Degummed Soybean Oil to Biodiesel: Optimization of Degumming Methods and Evaluation of Fuel Properties. Int. J. Green Energy 2010, 7, 593–599. [Google Scholar] [CrossRef]
  25. More, N.S.; Gogate, P.R. Intensified Degumming of Crude Soybean Oil Using Cavitational Reactors. J. Food Eng. 2018, 218, 33–43. [Google Scholar] [CrossRef]
  26. Talpur, M.Y.; Sherazi, S.T.H.; Mahesar, S.A.; Kandhro, A.A. Effects of Chicken Frying on Soybean, Sunflower and Canola Oils. Pak. J. Anal. Environ. Chem. 2009, 10, 59–66. [Google Scholar]
  27. Arun, N.; Sharma, R.V.; Dalai, A.K. Green Diesel Synthesis by Hydrodeoxygenation of Bio-Based Feedstocks: Strategies for Catalyst Design and Development. Renew. Sustain. Energy Rev. 2015, 48, 240–255. [Google Scholar] [CrossRef]
  28. Chen, S.; Zhou, G.; Miao, C. Green and Renewable Bio-Diesel Produce from Oil Hydrodeoxygenation: Strategies for Catalyst Development and Mechanism. Renew. Sustain. Energy Rev. 2019, 101, 568–589. [Google Scholar] [CrossRef]
  29. Li, T.; Cheng, J.; Huang, R.; Zhou, J.; Cen, K. Conversion of Waste Cooking Oil to Jet Biofuel with Nickel-Based Mesoporous Zeolite Y Catalyst. Bioresour. Technol. 2015, 197, 289–294. [Google Scholar] [CrossRef]
  30. Mäki-Arvela, P.; Rozmysłowicz, B.; Lestari, S.; Simakova, O.; Eränen, K.; Salmi, T.; Murzin, D.Y. Catalytic Deoxygenation of Tall Oil Fatty Acid over Palladium Supported on Mesoporous Carbon. Energy Fuels 2011, 25, 2815–2825. [Google Scholar] [CrossRef]
  31. Verma, D.; Rana, B.S.; Kumar, R.; Sibi, M.G.; Sinha, A.K. Diesel and Aviation Kerosene with Desired Aromatics from Hydroprocessing of Jatropha Oil over Hydrogenation Catalysts Supported on Hierarchical Mesoporous SAPO-11. Appl. Catal. A Gen. 2015, 490, 108–116. [Google Scholar] [CrossRef]
  32. Di Vito Nolfi, G.; Gallucci, K.; Rossi, L. Green Diesel Production by Catalytic Hydrodeoxygenation of Vegetables Oils. Int. J. Environ. Res. Public Health 2021, 18, 13041. [Google Scholar] [CrossRef] [PubMed]
  33. Šimáček, P.; Kubička, D.; Šebor, G.; Pospíšil, M. Hydroprocessed Rapeseed Oil as a Source of Hydrocarbon-Based Biodiesel. Fuel 2009, 88, 456–460. [Google Scholar] [CrossRef]
  34. Xu, L.; Zhang, J.; Ding, J.; Liu, T.; Shi, G.; Li, X.; Dang, W.; Cheng, Y.; Guo, R. Pore Structure and Fractal Characteristics of Different Shale Lithofacies in the Dalong Formation in the Western Area of the Lower Yangtze Platform. Minerals 2020, 10, 72. [Google Scholar] [CrossRef]
  35. Jaroszewska, K.; Masalska, A.; Grzechowiak, J.R. Hydroisomerization of Long-Chain Bio-Derived n-Alkanes into Monobranched High Cetane Isomers via a Dual-Component Catalyst Bed. Fuel 2020, 268, 117239. [Google Scholar] [CrossRef]
  36. Chen, Y.K.; Hsieh, C.H.; Wang, W.C. The Production of Renewable Aviation Fuel from Waste Cooking Oil. Part II: Catalytic Hydro-Cracking/Isomerization of Hydro-Processed Alkanes into Jet Fuel Range Products. Renew. Energy 2020, 157, 731–740. [Google Scholar] [CrossRef]
  37. Lin, C.-H.; Chen, Y.-K.; Wang, W.-C. The Production of Bio-Jet Fuel from Palm Oil Derived Alkanes. Fuel 2020, 260, 116345. [Google Scholar] [CrossRef]
  38. ASTM D1655-23; Standard Specification for Aviation Turbine Fuels. ASTM International: West Conshohocken, PA, USA, 2023.
Energies 17 06195 g001
Figure 1. SAF Production methods [8,9,10,11,12,13,14].
Figure 1. SAF Production methods [8,9,10,11,12,13,14].
Energies 17 06195 g001
Energies 17 06195 g002
Figure 2. The schematic of producing synthetic aviation fuels through the HEFA process.
Figure 2. The schematic of producing synthetic aviation fuels through the HEFA process.
Energies 17 06195 g002
Energies 17 06195 g003
Figure 3. Scheme of hydrogenation unit of HDO and HI processes.
Figure 3. Scheme of hydrogenation unit of HDO and HI processes.
Energies 17 06195 g003
Energies 17 06195 g004
Figure 4. Results of the HDO process for degummed soybean oil using a commercial nickel catalyst: (a) effect of temperature (hydrogen pressure 10 MPa, LHSV = 0.5), (b) influence of temperature on product composition and effect of reaction.
Figure 4. Results of the HDO process for degummed soybean oil using a commercial nickel catalyst: (a) effect of temperature (hydrogen pressure 10 MPa, LHSV = 0.5), (b) influence of temperature on product composition and effect of reaction.
Energies 17 06195 g004
Energies 17 06195 g005
Figure 5. Results of the HDO process for degummed soybean oil using a commercial nickel catalyst: (a) effect of pressure (temperature 340 °C, LHSV = 0.5), (b) influence of hydrogen pressure on product composition and effect of reaction.
Figure 5. Results of the HDO process for degummed soybean oil using a commercial nickel catalyst: (a) effect of pressure (temperature 340 °C, LHSV = 0.5), (b) influence of hydrogen pressure on product composition and effect of reaction.
Energies 17 06195 g005
Energies 17 06195 g006
Figure 6. Stability of the nickel catalyst in the hydrodeoxygenation process for degummed soybean oil in 340 °C, 10 MPa, and LHSV = 1.
Figure 6. Stability of the nickel catalyst in the hydrodeoxygenation process for degummed soybean oil in 340 °C, 10 MPa, and LHSV = 1.
Energies 17 06195 g006
Energies 17 06195 g007
Figure 7. GC/MS chromatogram of the product of HDO process in 340 °C, 10 MPa, and LHSV = 1.
Figure 7. GC/MS chromatogram of the product of HDO process in 340 °C, 10 MPa, and LHSV = 1.
Energies 17 06195 g007
Energies 17 06195 g008
Figure 8. (a) Pore distribution, and (b) adsorption isotherm of fresh and used nickel catalysts used in the hydrodeoxygenation process for degummed soybean oil, determined using nitrogen sorption at −196.15 °C.
Figure 8. (a) Pore distribution, and (b) adsorption isotherm of fresh and used nickel catalysts used in the hydrodeoxygenation process for degummed soybean oil, determined using nitrogen sorption at −196.15 °C.
Energies 17 06195 g008
Energies 17 06195 g009
Figure 9. TG (bold line) and DTG (thin line) curves of fresh and used nickel catalyst samples conducted in a nitrogen atmosphere.
Figure 9. TG (bold line) and DTG (thin line) curves of fresh and used nickel catalyst samples conducted in a nitrogen atmosphere.
Energies 17 06195 g009
Energies 17 06195 g010
Figure 10. Results of the HI process for n-alkanes derived from degummed soybean oil using 0.5% Pt/Al2O3 + SAPO-11 + 3% PEG-4 catalyst: (a) effect of temperature (hydrogen pressure 1 MPa, LHSV = 0.5), and (b) effect of pressure (temperature 320 °C, LHSV = 0.5).
Figure 10. Results of the HI process for n-alkanes derived from degummed soybean oil using 0.5% Pt/Al2O3 + SAPO-11 + 3% PEG-4 catalyst: (a) effect of temperature (hydrogen pressure 1 MPa, LHSV = 0.5), and (b) effect of pressure (temperature 320 °C, LHSV = 0.5).
Energies 17 06195 g010
Energies 17 06195 g011
Figure 11. Results of the HI process for n-alkanes derived from degummed soybean oil using 0.5% Pt/Al2O3 + SAPO-11 + 3% PEG-4 catalyst: (a) effect of temperature (hydrogen pressure 1 MPa, LHSV = 0.5), and (b) effect of pressure (temperature 320 °C, LHSV = 0.5).
Figure 11. Results of the HI process for n-alkanes derived from degummed soybean oil using 0.5% Pt/Al2O3 + SAPO-11 + 3% PEG-4 catalyst: (a) effect of temperature (hydrogen pressure 1 MPa, LHSV = 0.5), and (b) effect of pressure (temperature 320 °C, LHSV = 0.5).
Energies 17 06195 g011
Energies 17 06195 g012
Figure 12. Impact of (a) temperature and (b) pressure on the quantities of mono-branched and multi-branched hydrocarbons in the hydroisomerization process for n-alkanes derived from degummed soybean oil.
Figure 12. Impact of (a) temperature and (b) pressure on the quantities of mono-branched and multi-branched hydrocarbons in the hydroisomerization process for n-alkanes derived from degummed soybean oil.
Energies 17 06195 g012
Energies 17 06195 g013
Figure 13. Stability of the 0.5% Pt/Al2O3 + SAPO-11 + 3% PEG-4 catalyst during the hydroisomerization of n-alkanes derived from degummed soy oil at T = 320 °C, p = 1 MPa, and LHSV = 0.5.
Figure 13. Stability of the 0.5% Pt/Al2O3 + SAPO-11 + 3% PEG-4 catalyst during the hydroisomerization of n-alkanes derived from degummed soy oil at T = 320 °C, p = 1 MPa, and LHSV = 0.5.
Energies 17 06195 g013
Energies 17 06195 g014
Figure 14. (a) Pore distribution and (b) adsorption isotherm of fresh and used 0.5% Pt/Al2O3 + SAPO-11 + 3% PEG-4 catalysts used in the hydroisomerization process for n-alkane from degummed soybean oil, determined using nitrogen sorption at −196 °C.
Figure 14. (a) Pore distribution and (b) adsorption isotherm of fresh and used 0.5% Pt/Al2O3 + SAPO-11 + 3% PEG-4 catalysts used in the hydroisomerization process for n-alkane from degummed soybean oil, determined using nitrogen sorption at −196 °C.
Energies 17 06195 g014
Energies 17 06195 g015
Figure 15. TG (bold line) and DTG (thin line) curves of fresh and used 0.5% Pt/Al2O3 + SAPO-11 + 3% PEG-4 catalyst samples conducted in an air atmosphere.
Figure 15. TG (bold line) and DTG (thin line) curves of fresh and used 0.5% Pt/Al2O3 + SAPO-11 + 3% PEG-4 catalyst samples conducted in an air atmosphere.
Energies 17 06195 g015
Energies 17 06195 g016
Figure 16. GC/MS chromatogram of the biocomponent Jet-A1.
Figure 16. GC/MS chromatogram of the biocomponent Jet-A1.
Energies 17 06195 g016
Table 1. Fatty acid profile (%) of soybean oil [26].
Table 1. Fatty acid profile (%) of soybean oil [26].
Fatty Acid[%]
C14:00.10
C16:011.33
C18:04.55
C18:1 cis22.24
C18;1 n-9 trans1.02
C18:2 n9,n-12 cis54.67
C18:2 n9,n-12 trans0.01
C18:3 n9,n-12,n-15 cis6.07
C18:3 n9,n-12,n-15 trans0.01
Table 2. Physicochemical properties of degummed soybean oil.
Table 2. Physicochemical properties of degummed soybean oil.
PropertyUnitResults
Acid NumbermgKOH/g0.78 (±0.01)
Iodine NumbergI2/100 g127.4 (±0.4)
Density at 20 °Cg/cm30.919 (±0.001)
Average Kinematic Viscositymm2/s32.18 (±0.02)
Table 3. Surface and pore properties of HDO catalyst.
Table 3. Surface and pore properties of HDO catalyst.
CatalystSBETVTVMIKROLaLm
[m2/g][cm3/g][cm3/g][nm][nm]
Ni/γ-Al2O3 + SiO2 (fresh)1790.3160.005896.139.6
Ni/γ-Al2O3 + SiO2 (used)1130.2570.001056.139.6
SBET—specific surface area, VT—total pore volume, VMIKRO—micropore volume, La—average length, Lm—median length.
Table 4. Surface and pore properties of HI catalyst.
Table 4. Surface and pore properties of HI catalyst.
CatalystSBETVTVMikroLaLm
[m2/g][cm3/g][cm3/g][nm][nm]
0.5% Pt/Al2O3 + SAPO-11 + 3% PEG-4 (fresh)2080.3970.02458.0812.1
0.5% Pt/Al2O3 + SAPO-11 + 3% PEG-4 (after used)1420.2970.00508.2012.4
0.5% Pt/Al2O3 + SAPO-11 + 3% PEG-4 (after used calcinated)1910.3750.02138.1112.3
Table 5. Properties of distilled hydrocarbon fraction in accordance with ASTM D7566.
Table 5. Properties of distilled hydrocarbon fraction in accordance with ASTM D7566.
PropertyUnitRequirements (ASTM D1655 (1)/D7566 (2))Bio-Component Jet-A1
Flash point°Cmin 38100
Freezing point°Cmax −47−58.5
(1) American Society for Testing and Materials D1655 [38]; (2) American Society for Testing and Materials D7566 [23].
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

Share and Cite

MDPI and ACS Style

Główka, M.; Wójcik, J.K.; Boberski, P.; Woszczyński, P.J.; Sabura, E. Highly Efficient Process for Producing a Jet-A1 Biofuel Component Through Hydroprocessing Soybean Oil over Ni and Pt Catalysts. Energies 2024, 17, 6195. https://doi.org/10.3390/en17236195

AMA Style

Główka M, Wójcik JK, Boberski P, Woszczyński PJ, Sabura E. Highly Efficient Process for Producing a Jet-A1 Biofuel Component Through Hydroprocessing Soybean Oil over Ni and Pt Catalysts. Energies. 2024; 17(23):6195. https://doi.org/10.3390/en17236195

Chicago/Turabian Style

Główka, Marek, Jan Krzysztof Wójcik, Przemysław Boberski, Piotr Józef Woszczyński, and Ewa Sabura. 2024. "Highly Efficient Process for Producing a Jet-A1 Biofuel Component Through Hydroprocessing Soybean Oil over Ni and Pt Catalysts" Energies 17, no. 23: 6195. https://doi.org/10.3390/en17236195

APA Style

Główka, M., Wójcik, J. K., Boberski, P., Woszczyński, P. J., & Sabura, E. (2024). Highly Efficient Process for Producing a Jet-A1 Biofuel Component Through Hydroprocessing Soybean Oil over Ni and Pt Catalysts. Energies, 17(23), 6195. https://doi.org/10.3390/en17236195

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop