Deoxygenation Of Triglycerides Research Articles

The impact of operating conditions on H2-free catalytic deoxygenation of triglycerides for bio-jet fuel synthesis: A step towards sustainable aviation

The impact of operating conditions on H2-free catalytic deoxygenation of triglycerides for bio-jet fuel synthesis: A step towards sustainable aviation

Analysis of palm oil hydrodeoxygenation pathway selectivity based on oxygen quantification

Hydrogenation of palm oil over commercial NiMo/γ-Al2O3 catalysts and the effect of operating conditions were investigated in an autoclave with a continuous H2 flow mode. Methanation as the side reactions were taken into account in the reaction path selectivity for the first time. Three competing reaction pathways of hydrodecarboxylation, hydrocarbonation, and direct hydrodeoxygenation were clearly distinguished by quantifying the oxygen in the aqueous, organic, and gas phases. The results corroborated that the temperature and hydrogen supply were crucial to oxygen removal and the selectivity of the HDO pathways. Methane is the predominant gas product rather than propane during triglyceride deoxygenation, in which 87–100% of the methane production comes from the glycerol skeleton of the triglyceride and the rest comes from the CO methanation. Lower temperature favored the direct HDO route, while the selectivity of the HDCO and HDCO2 reactions preferred a higher temperature. HDO dominated the hydrodeoxygenation process under all H2 supply conditions, followed by the HDCO2 pathway and the HDCO reaction. This study brings the understanding of the vegetable oil triglyceride hydrodeoxygenation process to the molecular level and can potentially guide the optimization of process conditions.

Liquefaction, cracking and hydrogenation of microalgae biomass resources to CO2 negative advanced biofuels: Mechanisms, reaction microkinetics and modelling

Deoxygenation of triglycerides is one of the crucial pathways for the production of oxygen-free hydrocarbons and biofuels that are fully compatible with conventional internal combustion engines. The one-step liquefaction and hydrotreatment of Chlorella sorokiniana microalgae was investigated in a three-phase slurry reactor. The production of diesel-like hydrocarbons was successfully accomplished over sulfide form of NiMo/Al2O3 catalyst under hydrogen atmosphere. The present work contains a comprehensive investigation of the temperature and hydrogen pressure influence on the final product composition. The highest yield of C18 and C16 (26.1% and 10.7%, respectively) was reached by increasing the reaction temperature to 350 °C and hydrogen pressure to 50 bar, while at milder conditions (200 °C and 20 bar) the products appeared only in trace concentrations. In order to obtain an accurate kinetic model, reaction mechanism was first needed to be determined based on experimentally obtained products and intermediates. A simplified reaction pathway contains liquefaction, hydrogenolysis, hydrodeoxygenation, decarboxylation and decarbonylation. The model comprises mass transfer phenomena involved in the liquefaction process, the mass transfer of hydrogen from gas to liquid phase, adsorption, desorption and surface reaction kinetics. The lowest rate constant was calculated for the microalgae conversion to triglycerides (k0 = 1.93 × 10−6 min−1), indicating slow liquefaction.

Effect of heating rate on oil yield and composition in co-pyrolysis of polypropylene and triglycerides from refined palm oil using ZrO2.Al2O3.TiO2 catalyst

Polypropylene is major contributor to waste plastics, but its pyrolysis produces hydrogen radicals beneficial for deoxygenation of carboxylic acids. Fatty acids can be obtained by pyrolysis of triglycerides from refined palm oil. To investigate the possibility of the use of polypropylene as hydrogen donor and as part of hydrocarbons for producing hydrocarbons by deoxygenation of triglycerides, the present research works on catalytic co-pyrolysis of refined palm oil and polypropylene in a semibatch reactor. Two heating rates, i.e. 10℃/min and 6℃/min, were chosen to investigate their effect on liquid yield and remaining oxygen content. The C abundance in liquid product are analysed by C-NMR. The present catalyst of ZrO2.γAl2O3.TiO2 has succeeded in suppressing content of oxygen atoms in liquid product with carbon abundance associated with oxygen not more than 2%. The catalyst contains high basicity which hinders high contribution of polypropylene to the co-pyrolysis by leaving high yields of wax and non-condensable gas. By comparison of primary and secondary alkyl contents in liquid phase, catalytic pyrolysis of refined palm oil produces liquid phase with higher proportion of secondary alkyl while that of polypropylene produces liquid fraction with higher proportion of primary alkyl.

Importance of pore size and Lewis acidity of Pt/Al2O3 for mitigating mass transfer limitation and catalyst fouling in triglyceride deoxygenation

The deoxygenation of triglycerides via hydrotreating is a promising route for producing hydrocarbon fuels from renewable biomass. Because triglycerides are bulky esters possessing multiple C=C bonds, mass transfer limitation and coke deposition within the pore space of catalysts are significant problems. In this study, the catalytic effects of porous structure and surface acidity of Pt/Al2O3 were rigorously investigated in triglyceride deoxygenation. Pt was supported on a series of Al2O3 materials with various crystal structures (γ, θ, and α), pore sizes (3.3–28.6 nm), and Lewis acid amounts (0–337 µmol g−1), which were prepared by sol–gel synthesis. The γ- and θ-Al2O3 phases containing appreciable pentacoordinated Al sites effectively stabilized highly dispersed Pt particles (1.3–1.5 nm) via strong metal-support interactions and exhibited high catalytic activities. Conversely, Pt on α-Al2O3 without pentacoordinated Al sites exhibited very poor dispersion (> 12.6 nm), resulting in low catalytic activity. The results also showed that large mesopores (pore diameter > ∼12 nm) were essential to obtain maximum catalytic activity without mass transfer limitation and to suppress catalyst deactivation by fouling. When comparing the γ- and θ-Al2O3 phases, the latter generally showed inhibited formation of heavy products and coke owing to its larger pore size and smaller amount of Lewis acid sites that can catalyze undesirable oligomerization of unsaturated fatty acids. Consequently, Pt on θ-Al2O3 with extra-large mesopores (pore diameter: 28.6 nm) simultaneously exhibited the highest deoxygenation activity, selectivity toward diesel-range paraffins, and long-term stability.

Phonolite Material as Catalyst Support for the Hydrotreatment of Gas Oil and Vegetable Oil Type Feedstocks.

Phonolite material has shown to be promising catalyst support for the deoxygenation of triglycerides. In this work, we continue with our previous research by synthesising and testing three acid-treated phonolite-supported Co-Mo, Ni-Mo and Ni-W catalysts for the hydrotreating of atmospheric gas oil and co-processing with rapeseed oil at industrial operating conditions (350–370 °C, WHSV 1–2 h−1, 5.5 MPa) in the continuous regime for more than 270 h. The phonolite-supported catalysts showed hydrotreating activity comparable with commercial catalysts, together with a complete conversion of triglycerides into n-alkanes. During co-processing, the Ni-promoted catalyst showed strong stability, with similar activity previous to the rapeseed oil addition. Our results enable us to evaluate the suitability of phonolite as catalyst support for the development of plausible alternatives to conventional hydrotreating catalysts for the co-processing of middle distillates with vegetable oils.

Highly active iron-promoted hexagonal mesoporous silica (HMS) for deoxygenation of triglycerides to green hydrocarbon-like biofuel

The interest in the production of sustainable hydrocarbon-like biofuel is increasing due to the environmental issues such as global warming and uncertainty of crude oil prices. A series of Fe catalysts (5, 10, 40, and 100 wt% Fe) supported on the hexagonal mesoporous silica (HMS) were successfully prepared for the production of biofuel via deoxygenation (DO) reaction. In the DO reaction, the diesel range biofuel is produced in the absence of H2 and solvents. Interestingly, the 40 wt.%Fe/HMS catalyst exhibited the highest conversion and selectivity of 81.4 and 84.8%, respectively toward C8-C20 hydrocarbons-like biofuel at 380 °C for 2 h. This performance is closely related to the well-dispersed Fe in the hematite phase, along with the interaction between Si-OH and Fe-O bonds. The acidity, surface area, and pore size of Fe/HMS have improved the catalytic activity. This result demonstrates that the Fe/HMS catalyst is a potential DO catalyst for the production of renewable hydrocarbon-like biofuel.

Recent trends for clean fuel production by deoxygenation of pure palmitic acid using Ni/C catalyst.

Deoxygenation of triglycerides is one of key processes making possible a convenient production of high quality automotive fuels components (sulfur-, oxygen- and aromatics-free). This reaction was studied over non noble metal catalysts 20wt%Ni/C and performed in batch reactor system (autoclave) by using pure palmitic acid, n-hexane as a solvent and 200 psi pressure. The effect of different atmospheres (pure hydrogen, pure nitrogen, and mixture of 50 psiH2/150psiN2) and different temperature range (300 oC-350 oC) under a mixed atmosphere (50 psiH2/150psiN2) were studied in this paper. The main product was n-pentadecane (C15) which the catalyst Ni/C has lower cracking selectivity to light hydrocarbons. The total conversion of carboxylic groups of palmitic acid and the selectivity to C15 in case of pure nitrogen are (22.29% and 12.38%) respectively and in case of hydrogen they are (75.16% and 80.07%) respectively. In case of using H2/N2 as a mixture the total conversion and the selectivity are (81.18% and 75.32%) respectively for Ni/C catalyst. The total conversion increases from 81.18% to 99.99% by increase the temperature from 300 oC to 350 oC. The deoxygenation of palmitic acid over 20wt%Ni/C catalyst indicated that the high selectivity for n-alkane (C15) (75.32%) at 300 oC and reach maximum value (98.11%) at 350oC. Analysis of liquid products by gas chromatography (GC) was used to determine n-alkane (C15) yield and other products (isomeres, olefins and dimers). Insights pertaining to the reaction scheme and an assessment of the reaction products as liquid transportation fuels are also provided in this contribution.

Generating Organic Liquid Products from Catalytic Cracking of Used Cooking Oil over Mechanically Mixed Catalysts

Used cooking oil is unsuitable to use again in the food process, but it may be harnessed as raw material in biofuel production. In this work, used palm oil was reactedvia cracking over mechanically mixed catalystsbetween ZSM-5 and Y-Re-16to generate organic liquid products (OLP). The catalysts used were known for highacidity and lowcost for decomposition, degradation,and deoxygenation of triglycerides. The cracking experiments were conducted in a flow reactor. The experimental variables included reaction temperature between 300-500°C, catalyst loading between 5-20 % w/w, and ratio of mixed catalyst between ZSM-5 and Y-Re-16 from 0-100 % w/w. They were setvia response surface methodology and central composite design of experiments. Both catalysts showed good cracking reaction. The optimum condition for generating the OLP of about 85 % w/w was found at 300°C, 5 % catalyst loading, 97 % ratio of mixed catalyst. The OLPs with different short-chain hydrocarbons between C7-C21 were identified. The main components were 71.43% of diesel, 12.11% of gasoline, and 8.95% of kerosene-like components.

Single-step hydroconversion of triglycerides into biojet fuel using CO-tolerant PtRe catalyst supported on USY

The direct hydroconversion of triglycerides into biojet fuel (i.e., cascade reactions including hydrogenation, deoxygenation, and hydrocracking) is challenging, even though it is beneficial in terms of process intensification. This is because the minute amount of CO produced during deoxygenation can poison the metal component of various metal–acid bifunctional catalysts, causing undesired overcracking and rapid catalyst deactivation through coke formation. To overcome this problem, we synthesized a CO-tolerant catalyst by supporting bimetallic PtRe on ultra-stable Y (USY) zeolite as acidic support. Compared to conventional catalyst (e.g., Pt/USY), PtRe/USY showed markedly enhanced tolerance to CO because it had weakened interaction with CO and also could rapidly convert the chemisorbed CO into less harmful methane and H2O through methanation. Consequently, overcracking and catalyst deactivation were greatly suppressed during the direct triglyceride hydroconversion. It is remarkable that PtRe/USY is intrinsically a much poorer hydrocracking catalyst than Pt/USY under pure H2 atmosphere because of its high hydrogenolysis activity. However, H2O and CO produced in situ during the deoxygenation of triglycerides selectively poisoned the active sites for undesired hydrogenolysis, thereby making PtRe/USY a highly stable and selective catalyst for producing biojet fuel. Under the optimum condition, 41 wt% of biojet fuel with respect to palm oil could be produced through direct hydroconversion, which satisfied all the required fuel specifications.

Efficient deoxygenation of triglycerides to hydrocarbon-biofuel over mesoporous Al2O3-TiO2 catalyst

The renewable hydrocarbon-like biofuel from biomass is crucial to substitute fossil fuel. A series of mesoporous Al2O3-TiO2 mixed oxide catalysts with different TiO2 content (0.1Ti-0.9Al, 0.2Ti-0.8Al and 0.3Ti-0.7Al) have been synthesized. The physicochemical properties of the catalysts were characterized by XRD, FESEM-EDX, BET, FTIR, NH3-TPD, FTIR-Py, and TGA. The deoxygenation (DO) of triglyceride (i.e. triolein) was carried out in the absence of hydrogen and solvent. The mesoporous Al2O3-TiO2 catalysts showed high catalytic activity performance as compared to that of Al2O3 and TiO2. It was found that 0.2Ti-0.8Al catalyst exhibited the highest conversion (76.86%), and selectivity (27.26%) toward n-C15 + n-C17 at 380 °C after 4 h. The excellence performance of mesoporous Al2O3-TiO2 was attributed to its acidity, mesoporosity and larger surface area. The results reveal that the mesoporous Al2O3-TiO2 catalyst is a promising catalyst for the synthesis of hydrocarbon-like biofuel.

Hydrothermal deoxygenation of triglycerides over carbon-supported bimetallic PtRe catalysts without an external hydrogen source

Hydrothermal deoxygenation is a promising route for producing oxygen-free hydrocarbons from triglycerides even without an external H2 source. In this study, PtRe catalysts supported on various carbons were investigated for this reaction. The PtRe catalysts showed enhanced rates of glycerol reforming for in situ H2 production and higher deoxygenation activities, as compared to Pt catalysts. Consequently, the PtRe catalysts showed superior hydrothermal deoxygenation performances. Carbon supports with low oxygen content (e.g., CNT) were beneficial for supporting highly dispersed and well alloyed PtRe particles, which were prerequisites for high catalytic activity. Oxygen-rich carbon surfaces caused the segregation of Re, causing low catalytic activity. PtRe/CNT showed the best performance, yielding 72 wt% n-paraffin (theoretical yield: 79 wt%) from palm oil. The catalyst could be recycled for 5 times without significant loss of activity.

Catalytic deoxygenation of stearic acid and waste cooking oil over Pd/SBA-15 for obtaining hydrocarbons with potential as renewable liquid fuels

It has been found that catalytic deoxygenation of triglycerides is a viable pathway for obtaining renewable liquid fuels to contribute to meet the global energy demand. In this study, SBA-15 mesoporous silica was synthesized in a pure form and modified with mesitylene (TMB) as a swelling molecule (SBA15-TMB). Catalysts with 0.5, 1.5 and 3.0 wt% Pd were synthesized and tested by deoxygenation of stearic acid (SA), obtaining initial conversions of 68–98% that decreased to 36–73% after 6 h time-on-stream. The most abundant product was n-heptadecane, with a selectivity of ~ 90%. The most active catalyst evaluated with SA was 3.0 wt% Pd over unmodified SBA-15 (30Pd/SBA-15). Subsequently, fresh and regenerated 30Pd/SBA-15 catalysts were tested with waste cooking oil (WCO) feed, obtaining conversions of 74 and 72%, respectively, but the fresh catalyst allowed a better oxygen removal (91%. Additionally, commercial Pd(10wt %)/C catalyst was evaluated, obtaining results comparable to those for the regenerated 30Pd/SBA-15 catalyst. The main WCO reaction product for all catalysts was a diesel fraction (C12-C21), and the quality of the products was not very different, following the order: Pd(10wt %)/C > 3.0Pd/SBA-15-regenerated > 3.0Pd/SBA-15-fresh. The results obtained indicate that shynthetized catalysts of this study are promising for obtaining renewable diesel from low-cost feeds while using low hydrogen consumption.

Effects of Fatty Acid Compositions on Heavy Oligomer Formation and Catalyst Deactivation during Deoxygenation of Triglycerides

Deoxygenation of triglycerides (e.g., vegetable and microalgae oils) through hydro-upgrading is one of the most important routes to produce oxygen-free hydrocarbon fuels from biomass. Even though natural triglycerides are composed of fatty acids of different structures, their effects on catalytic selectivity and deactivation during deoxygenation have not been comprehensively investigated. In this study, we used three different reactant triglycerides including palm oil, soybean oil, and linseed oil for catalytic deoxygenation over Pt/γ-Al2O3. These oils consist of fatty acids with increasing degrees of unsaturation in the order of palm oil (number of C═C per fatty acid: 0.55) < soybean oil (1.33) < linseed oil (2.18). The catalytic results showed that the increased unsaturation of the triglycerides caused enhanced formation of heavy products by oligomerization (mostly dimers) of unsaturated fatty acid derivatives through Diels–Alder reaction and/or radical addition. These heavy products were readily transf...

Synergistic effect of oxygen vacancies and highly dispersed Pd nanoparticles over Pd-loaded TiO2 prepared by a single-step sol–gel process for deoxygenation of triglycerides

Renewable diesel has gained attention in recent years due to its superior fuel properties compared to the conventional biodiesel. The uses of Pd supported TiO2 (Pd/TiO2) and Pd supported activated carbon (Pd/C) catalysts for the deoxygenation of triglycerides to renewable diesel were investigated. Two different types of titania supports, i.e. mesoporous titania synthesized by a surfactant-assisted templating sol–gel method (SG-TiO2) and commercial P25-TiO2 (P25-TiO2), were used to investigate the effect of TiO2 crystal structure on the catalytic activity. The prepared catalysts were characterized by N2 adsorption-desorption isotherms, X-ray diffraction (XRD), H2 chemisorption, H2 temperature-programmed reduction (H2-TPR) and X-ray photoelectron spectroscopy (XPS). The liquid products obtained from the deoxygenation of triglycerides in beef fat over the prepared catalysts at 325 °C, 500 psig, and H2/triglyceride molar ratio of 30 were in the diesel fuel specification range (C15-18). The main liquid products were n-heptadecane (n-C17) and n-pentadecane (n-C15), resulting from the decarboxylation or decarbonylation pathways. It was found that the Pd/P25-TiO2 catalyst exhibited a higher catalytic performance compared to the Pd/C catalyst. The formation of defects (oxygen vacancies and Ti3+) on TiO2, Pd dispersion and inducement of SMSI effect play an important role in the catalytic activity and the diesel yield on Pd/SG-TiO2 catalysts. Furthermore, the Pd incorporation methods, i.e. incipient wetness impregnation (IWI), photochemical deposition (PCD) and single-step sol–gel (SSSG), were also investigated. The Pd/TiO2 prepared by SSSG method exhibited the highest conversion of beef fat and selectivity to the diesel fuel (C15-18) which could be due to its well-dispersed Pd nanoparticles with relatively small size, high defects on TiO2 support and strong SMSI behavior.

Deoxygenation of triglycerides by silylation under exceptionally mild conditions

Efficient deoxygenation of lipids using hydrosiloxanes leads to polyunsaturated hydrocarbons.

Promoting deoxygenation of triglycerides via Co-Ca loaded SiO2-Al2O3 catalyst

Triglycerides and fatty acid derivatives can be converted to hydrocarbon-grade green diesel that are entirely fungible to the fossil fuels. In the present study, deoxygenation (DO) process of triolein was studied by using mesoporous SiO2-Al2O3 supported Co-Ca catalyst. The presence of active metals (Co-Ca) showed high DO activity exclusively via decarboxylation/decarbonylation (deCOx) pathways with maximum hydrocarbon n-(C8-C20) yield of 73%, and high selectivity of n-C15 and n-C17 fractions. This results suggested the acid-base active sites of catalyst provide selective deCOx pathway of triglycerides structure. In additional, the presence of high surface area of Co-Ca/ SiO2-Al2O3 enhance the metal dispersion for better accessment of large molecular reactant with catalyst during DO process. An optimum Co metal content (10 wt.%) for deCOx reaction was observed, while an excess Co content is not preferable due to tendency of cracking effect. The efficiency of Co-Ca/SiO2-Al2O3 was investigated by using non-edible feedstock (e.g. Ceiba oil and Sterculia oil) along with catalyst stability study were carried out. Resulst also indicated that degradation of DO activity was due to the formation of coke.

Catalytic Hydrotreatment of Jatropha Oil over Lanthanum Hydroxide Supported Noble Metals: Effect of Promotion with Cerium

AbstractCatalytic hydrotreatment of jatropha oil is an attractive option for the production of diesel‐range hydrocarbons. Here, we synthesized and tested the performance of two novel La(OH)3 supported Pd and Ru catalysts promoted with Ce, viz. Pd−Ce/La(OH)3 and Ru−Ce/La(OH)3 (hereafter referred to as Pd−Ce and Ru−Ce). The deoxygenation of jatropha oil was performed in a fixed‐bed reactor. The reaction conditions were varied so: temperature 603 to 663 K, weight hourly space velocity (WHSV) 1 to 4 h−1, pressure 1.5 to 3 MPa and H2/oil ratio 200 to 1000 (v/v). The performance of our lab‐made materials was encouraging. Upon optimization of the hydrotreating process, the best performance of both Pd‐Ce and Ru−Ce was achieved at T=663 K, WHSV=1 h−1, P=3 MPa and H2/oil ratio=600 v/v. Oil conversion at these reaction conditions was 97.3 and 91.8% over Pd−Ce and Ru−Ce. The respective hydrocarbon yield was 81% (for Pd−Ce) and 75.3% (for Ru−Ce). The resilience of the lab‐made catalysts was tested by time‐on‐stream study. Both catalysts were stable for 40 hours of time‐on‐stream. Finally, reaction pathway for deoxygenation of triglycerides over the investigated catalysts was proposed.

Pyrolytic-deoxygenation of triglycerides model compound and non-edible oil to hydrocarbons over SiO2-Al2O3 supported NiO-CaO catalysts

Catalytic deoxygenation (DO) of triglycerides-based feeds to diesel-like fuel was investigated over NiO-CaO/SiO2-Al2O3 and NiO/SiO2-Al2O3 catalysts using semi-batch reactor under partial vacuum and inert N2 flow. The results showed that the bi-functional catalyst exhibited the highest DO activity with product selectivity toward diesel-like fuel n-(C13–C20). The catalytic process appeared to inhibit the occurrence of side reactions via neutralization of the strong acid sites. On the other hand, DO reaction under inert N2 flow has improved the deoxygenated product, which demonstrate that N2 flow condition has effectively removed the decarboxylation/decarbonylation gasses (CO2/CO) from poisoning the catalyst active sites. The high concentration of strong basic-acid sites of the catalyst is the main reason for increased CC cleavage pathway, while milder acidic sites responsible for CO cleavage pathway. High degree of unsaturated fatty acid in the feedstock has affected adversely the DO of triglycerides by accelerating the catalyst deactivation. The N2 flow condition, degree of unsaturated fatty acid in the feedstocks, acidity and basicity of the catalysts are important factors to improve DO activity as well as product selectivity.

Hydrotreating of waste cooking oil over supported CoMoS catalyst – Catalyst deactivation mechanism study

The hydrotreating of waste cooking oil (WCO) to produce fuels not only solves waste problem but also recycles energy. CoMoS is regarded as an effective catalyst for the deoxygenation of triglyceride during the hydrotreating process; however, it is easy to deactivate. This article studied the deactivation mechanism of a supported CoMoS commercial catalyst during the hydrotreating of WCO. It was the first time to find triglyceride deoxygenation over different active sites during CoMoS catalyst deactivating process: saturated hydrocarbons were the primary products over MoS2 on the presulfided CoMoS catalyst, and unsaturated hydrocarbons were produced over MoO3 on the spent CoMoS catalyst as the transformation of the MoS2 into MoO3 occurred under high temperature operation. Three causes were observed for the deactivation of the studied catalyst: by-product water, loss of sulfur, and coke deposition. Low temperature operation at 275°C can control the deactivation of CoMoS catalyst due to coke deposition. In-situ drying and resulfiding the spent catalyst were proposed as methods to regenerate the spent catalyst.