Decarboxylation Of Fatty Acids Research Articles

In situ thermal-assisted photocatalytic decarboxylation of high-concentration biomass-derived fatty acids to alkanes

Heating is a straightforward method to increase reaction rates to meet industrial production, yet photocatalysis seldom incorporates it because their intrinsic driving force depends on the separation of photogenerated carriers, which is rarely affected by temperature. Here, we report a temperature-dependent photocatalytic decarboxylation strategy for producing long-chain n-alkanes from biomass-derived fatty acids using only the photothermal effect of the SnS catalyst. Under concentrated light irradiation without any external heating, and by employing high boiling-point solvents to reach optimal reaction temperatures (∼254 °C), Cn-1 n-alkane allows a very high concentration output (∼0.5 M for stearic acid to n-heptadecane) in a single operation, which is far beyond the capacity limit of conventional photocatalysis, typically no more than the mM levels. Mechanistic studies suggest that the in-situ heat brings the standing C-chain at low temperature down onto the SnS surface, increasing strain on the C-COO- bonds and facilitating reaction with photo-induced hole-electron pairs. We demonstrate that the majority of the incident light energy, when converted to heat, accelerates the photocatalytic decarboxylation.

Enhanced photocatalytic alkane production from fatty acid decarboxylation over sulfide-modified TiO2 under mild conditions

Photocatalytic decarboxylation of fatty acids derived from biomass is considered a sustainable approach for alkane production. In this study, a series of NiS2 co-catalyst-modified TiO2 (NiS2/TiO2) composites were successfully synthesized and employed for the photocatalytic decarboxylation of fatty acids. Under mild conditions, the optimized NiS2/TiO2 composite exhibited conversion of 60.2% and selectivity of 72.6% for converting chondritic acid to pentadecane, which was 6.56 times to single TiO2. The incorporation of the co-catalyst led to red shift of the absorption edge, and decrease in photoluminescence (PL) intensity, indicating enhanced light absorption and efficient separation of photogenerated charge in NiS2/TiO2. The lower work function of NiS2 compared with TiO2 and the differential charge density indicated that electrons tended to migrate from the S-atom to the O-atom, thus creating a built-in electric field that accelerated the reaction. The study on biofuel synthesized from biomass offered insights that can help mitigate future energy crises.

In Situ Formation of the Ag/V2O5 Catalyst for High-Flux Production of Alkane by Self-Heating Photocatalytic Fatty Acid Decarboxylation

In Situ Formation of the Ag/V₂O₅ Catalyst for High-Flux Production of Alkane by Self-Heating Photocatalytic Fatty Acid Decarboxylation

Visible light-driven self-heating photocatalytic decarboxylation of fatty acid over α-Fe2O3

Here we report a temperature-dependent strategy that achieves high-efficiency photocatalytic decarboxylation of long-chain fatty acids to Cn-1 n-alkanes, e.g., producing ∼0.5 M of n-heptadecane from stearic acid in a single operation with ∼91% selectivity, far beyond no more than mM limit capacities of conventional photocatalysis. Through the use of high boiling-point n-alkane solvents for getting the best self-heating based on the photothermal conversion effect of α-Fe2O3, i.e., high temperatures, which force the standing C-chain at low temperatures down onto the α-Fe2O3 surface for energy-storing, allowing photo-induced hole-electron pairs to readily approach and react with the more strained C-COO- bonds. And the consumption of photogenerated electrons shifts from the conventional PCET of the photo-Koble reaction into a step-wise pathway to form more favorable carbanion intermediate that reacting with H+ into RH is accelerated with lifting temperature. Our work offers a practical approach to upgrade photocatalytic decarboxylation by a convenient photo-to-heat route.

Highly efficient photocatalytic decarboxylation of fatty acids to alkanes enabled by photothermal conversion effect

Heating is the most straightforward means to achieve rapid, high-flux production of thermal catalytic reactions, but photocatalysis rarely uses it mainly because their intrinsic driving force depends on the photogenerated carriers separation , which has always been treated as little dependent of temperature and sometimes even with negative dependence. Here we report a temperature-dependent strategy of in-situ thermal-assisted photocatalytic decarboxylation of bioderived long-chain fatty acids into Cn–1n-alkanes over Sb2S3 photocatalyst. Under concentrated simulated sunlight illumination without external heating, this reaction system is readily self-heated to boiling (254 °C) of n-tetradecane solvent only by the photothermal conversion effect of Sb2S3. The heat from the incident light enables the standing C-chain at low temperature down onto the surface of Sb2S3 resulted in the CCOO− bonds with more strain, which makes it easier for light-induced hvb+/ecb− to approach and react with the energy-storing CCOO− bonds, thereby resulting in an increase in n-alkane single output concentrations exceeding five orders of magnitude. Our study demonstrated the vast majority of incident light energy could be harnessed in a heat form to enhance the efficiency of photocatalytic decarboxylation.

Decarboxylation of fatty acids by ternary zinc cationic complexes studied by mass spectrometry and theoretical calculations

We have shown that fatty acids can be decarboxylated in the gas phase via collision-induced dissociation (CID) of ternary zinc complexes of the general formula [(L)Zn(OOCR)]+, where RC3H7, C6H13, C7H15, C17H35, C17H33, C17H31 and L = 1,10-phenanthroline or 2,2′:6′,2″-terpyridine. These complexes were formed by electrospray ionization of a solution mixture of zinc(II) salt, fatty acid, and the ligand. Two pathways were mapped for the resulting [(L)ZnR]+ organozinc ion: i) a gas-phase ion-molecule reaction with a neutral carboxylic acid R’COOH in the linear quadrupole ion trap resulted in the production of the alkane RH and formation of [(L)Zn(OOCR’)]+; ii) a second CID stage produced an alkene and the ion [(L)ZnH]+ which underwent a subsequent ion-molecule reaction with R’COOH to form [(L)Zn(OOCR’)]+ ion accompanied by the loss of H2. In the case of RR’ = C3H7 (butyric acid), both processes presented formal catalytic cycles with the overall equations C3H7COOHC3H8+ CO2 or C3H7COOHC3H6 + H2+ CO2. Theoretical DFT calculations provided the energetics of reactants/products as well as transition state energies and were in agreement with the experimental data. The work identifies Zn as a potential catalyst for deoxygenation of fatty acid with no fragmentation of the alkyl chain.

High-Concentration Alkane Output via In Situ Thermal-Assisted Photocatalytic Decarboxylation of Biomass-Derived Fatty Acid

High-Concentration Alkane Output via In Situ Thermal-Assisted Photocatalytic Decarboxylation of Biomass-Derived Fatty Acid

Orthovanadate intercalated CuFe-LDO catalyzed hydrothermal liquefaction of microalgae for low nitrogen bio-oil production

Hydrothermal liquefaction (HTL) of microalgae for bio-oil production is a promising strategy to avoid extensive fossil fuel utilization, while tandem amidation and Maillard reactions during hydrolysis of cellular compounds unavoidably result in formation of nitrogen containing (N-containing) compounds, reducing quality of bio-oil. Accordingly, VO43− intercalated Cu–Fe layered double oxides named as Cu2Fe-VO4-LDO is firstly synthesized to both catalyze hydrolysis of cellular compounds and block N-containing compounds formation. The results indicate Cu2Fe-VO4-LDO can improve bio-oil yield from 19.32 to 20.32 wt%, with decrease of N/C ratio from 0.70 of control to 0.67 of experimental group, and increase of H/C ratio from 0.129 to 0.132. The insert of VO43− provides more strong-acid sites, which are beneficial to hydrolysis of cellular compounds. Meanwhile, more strong-base sites of Cu2Fe-VO4-LDO promote decarboxylation of fatty acids and removing amino-group of amino acids, subsequently improve production of alkanes. Furthermore, the reversible oxidation of VO43− promotes oxidation of reducing sugars, blocking tandem amidation and Maillard reaction between intermedia of hydrolyzed lipids, carbohydrates, and proteins. This work reports a methodology for synthesis of Cu2Fe-VO4-LDO with strong acid-base sites and reversible oxidize interlayer sites, providing a strategy to simultaneously improve bio-oil yield and reduce its N/C ratio.

Functional production and biochemical investigation of an integral membrane enzyme for olefin biosynthesis.

Integral membrane enzymes play essential roles in a plethora of biochemical processes. The fatty acid desaturases (FADS)-like superfamily is an important group of integral membrane enzymes that catalyze a wide array of reactions, including hydroxylation, desaturation, and cyclization; however, due to the membrane-bound nature, the majority of these enzymes have remained poorly understood. UndB is a member of the FADS-like superfamily, which catalyzes fatty acid decarboxylation, a chemically challenging reaction at the membrane interface. UndB reaction produces terminal olefins that are prominent biofuel candidates and building blocks of polymers with widespread industrial applications. Despite the great importance of UndB for several biotechnological applications, the enzyme has eluded comprehensive investigation. Here, we report details of the expression, solubilization, and purification of several constructs of UndB to achieve the optimally functional enzyme. We gained important insights into the biochemical, biophysical, and catalytic properties of UndB, including the thermal stability and factors influencing the enzyme activity. Additionally, we established the ability and kinetics of UndB to produce dienes by performing di-decarboxylation of diacids. We found that the reaction proceeds by forming a mono-carboxylic acid intermediate. Our findings shed light on the unexplored biochemical properties of the UndB and extend opportunities for its rigorous mechanistic and structural characterization.

Exploring Strategic Approaches for CvFAP Photodecarboxylation through Violet Light Irradiation

In this study, we describe a light-driven photocatalytic decarboxylation of palmitic acid and related fatty acids using Chlorella variabilis fatty acid photodecarboxylase (CvFAP). By utilizing violet light emitting diode (LED) light (50 W; 397 nm), we achieved a remarkable conversion efficiency of 99% within just 4 min, surpassing the previous 79% conversion achieved in 60 min using blue LED light (300 W; 439 nm). Importantly, the use of 50 W violet LED light also resulted in a lower enzyme photoinactivation rate when compared to 300 W blue LED. Comparing the whole-cell biocatalyst with the enzymatic extract, we found that the former demonstrated superior catalytic performance and reduced susceptibility to photoinactivation. Furthermore, whole-cell biocatalyst reuse was demonstrated after five sequential batches. Employing this approach, we successfully synthesized 26 mmol L-1 h-1 of pentadecane, showcasing a promising strategy to improve productivity. These findings represent a significant advancement in CvFAP photodecarboxylation processes compared to the literature, utilizing an alternative light source, with potential implications to the biofuel sector

Exponentially enhanced photocatalytic alkane production from biomass-derived fatty acid decarboxylation via self-heating induced conformational inversion

Heating is the most convenient means to enable unfavorable chemical reactions to scale application, but photocatalysis rarely uses it because its driving force has always been identified as the intensity...

Electrolyte dependence for the electrochemical decarboxylation of medium-chain fatty acids (n-octanoic acid) into fuel on Pt electrode

The deoxygenation of organic acids, important biomass feedstocks and derivatives, to synthesize hydrocarbon products under mild electrochemical conditions, holds significant importance for the production of carbon-neutral biofuels. There is still limited research on the influential factors of the electrochemical decarboxylation reaction of medium-chain fatty acids. In this study, n-octanoic acid (OA) was chosen as the research subject to investigate the electrochemical decarboxylation behavior of OA on a platinum electrode, focusing on the influence of different alkali metal cations (Li+, Na+, K+), common anions (SO42−, Cl−), and electrolyte pH. It was found that KOH as an electrolyte exhibited the best performance for OA. Possibly, the larger size of K+ increased the alkalinity of the electrode surface, facilitating OA deprotonation. LiOH electrolyte reduced the solubility of OA, thereby inhibiting the decarboxylation reaction. SO42− exhibited a weak promoting effect on the decarboxylation reaction of OA, while Cl− showed no adverse effect although Cl− may adsorb on the electrode surface. Furthermore, unlike short-chain fatty acids, medium-chain OA can only achieve efficient decarboxylation under alkaline conditions due to its solubility properties. This study provides references and foundations for future efforts to enhance the efficiency of electrochemical decarboxylation synthesis of hydrocarbon biofuels from medium-chain fatty acids.

Continuous Fatty Acid Decarboxylation using an Immobilized Photodecarboxylase in a Membrane Reactor.

The realm of photobiocatalytic alkane biofuel synthesis has burgeoned recently; however, the current dearth of well-established and scalable production methodologies in this domain remains conspicuous. In this investigation, we engineered a modified form of membrane-associated fatty acid photodecarboxylase sourced from Micractinium conductrix (McFAP). This endeavour resulted in creating an innovative assembled photoenzyme-membrane (protein load 5 mg cm-2 ), subsequently integrated into an illuminated flow apparatus to achieve uninterrupted generation of alkane biofuels. Through batch experiments, the photoenzyme-membrane exhibited its prowess in converting fatty acids spanning varying chain lengths (C6-C18). Following this, the membrane-flow mesoscale reactor attained a maximum space-time yield of 1.2 mmol L-1 h-1 (C8) and demonstrated commendable catalytic proficiency across eight consecutive cycles, culminating in a cumulative runtime of eight hours. These findings collectively underscored the photoenzyme-membrane's capability to facilitate the biotransformation of diverse fatty acids, furnishing valuable benchmarks for the conversion of biomass via photobiocatalysis.

Hierarchical porous honeycomb NiCo/C catalyst for decarboxylation of fatty acids and upgrading of sludge bio-crude

Honeycomb NiCo/C-Na catalyst featured with a micro-meso-macroporous structure is fabricated and shows a significantly higher catalytic activity for decarboxylation of fatty acid compared to a series of other carbon-based catalysts. A 100 % conversion of stearic acid and a C15-18 alkane total yield of 70 % is achieved at 280 °C for 3 h under 1 MPa H2 with heptadecane as the main product. NiCo/C-Na also achieves a complete conversion of monoglyceride into heptadecane when using edible oil as reactant. The catalyst is further evaluated for upgrading of sludge HTL bio-crude and proves to be highly efficient. The obtained upgraded biofuel exhibits a decreased viscosity and an increased density. Specifically, the higher heating value (HHV) increases to 47.32 MJ/kg. This result is attributed to the easier desorption of CO2, better H2 activation capacity and the unique hierarchical pore structure of the catalyst, which allows faster mass transfer and reaction rate.

Caution! Contents were hot: Novel biomarkers to detect the heating of fatty acids in residues from pottery use

Understanding exposure of pottery vessels to fire is an important question in the agenda of researchers studying how prehistoric pottery was used to prepare food and the reasons leading to its widespread adoption across the world. In the case lipid residues from cooking, making sense of the range of biochemical compounds synthesised by the application of significant amounts of heat (i.e > 100 °C) to lipid residues can reveal different use patterns in the repertoires of the earliest pottery productions. While knowledge about the thermal degradation of fats in archaeological pottery has been available since the mid-nineties, this paper presents and describes two previously unreported biomarkers detected during ongoing research on the earliest Mediterranean farming societies: the ketonic decarboxylation of saturated fatty acids and dicarboxylic acids resulting in very long chain oxo fatty acids, and, the cyclisation of monounsaturated fatty acids yielding ω-(2-alkylcyclopentyl)alkanoic acids. Therefore, combining experimentation with the analysis of several sets of Neolithic pottery, this paper aims at updating the available data on the range of known biomarkers for lipid thermal alteration by characterising said unreported compounds and facilitating their detection in further studies.

NiCo/SiO2 nanospheres for efficient synergetic decarboxylation of fatty acids and upgrading of municipal sludge HTL bio-crude to biofuels

Municipal sludge (MS) and derived HTL (hydrothermal liquefaction) bio-crude contains a large quantity of organics, including fatty acids, which may be a potential resource for producing biofuels via catalytic treatment. Herein, decarboxylation of fatty acids is chosen as the model reaction to screen a series of nickel-based bimetallic catalysts supported on homemade SiO2 nanospheres to investigate the synergetic effect. NiCo/SiO2 turned out with the best performance compared to NiCu-, NiZn-, NiMo- and NiFe/SiO2. An 83% conversion of stearic acid and an 84% selectivity of heptadecane via hydrothermal decarboxylation were achieved at 280 °C under 1 MPa H2. XPS results revealed the electron transfer from Co to Ni, leading to the formation of Niδ-, which is more accessible to bond with Cδ+ in the carboxyl group of fatty acids, thus facilitating the decarboxylation reaction. Compared to commercial SiO2, our homemade SiO2 showed a stronger carbon accumulation resistance, indicating a medium specific surface area was essential. Both the synergetic effect of NiCo bimetal and the carbon accumulation resistance of homemade SiO2 nanospheres contributed to the efficient hydrothermal decarboxylation. The NiCo/SiO2 catalyst was further applied for upgrading of MS HTL bio-crude to biofuels, and the theoretical higher heating value (HHV) was significantly improved from 34.4 to 37.2 MJ/kg, suggesting the potential application of converting MS bio-crude to biofuels.

Continuous hydrocarbon fuels production by photoenzymatic decarboxylation of free fatty acids from waste oils

Fatty acid photodecarboxylase, recently found in Chlorella variabilis NC64A (CvFAP), could efficiently catalyze C16-C18 fatty acids into C1-shortened hydrocarbons under visible light. This provides an alternative approach for hydrocarbon fuels production in mild conditions compared with hydrotreating of oils. In this study, a cascade system integrating lipase hydrolysis and CvFAP decarboxylation was demonstrated for the efficient production of hydrocarbon fuels from waste oils. The continuous CvFAP-catalyzed decarboxylation characteristics and performance of free fatty acids derived from waste oil were investigated for the first time. A hydrocarbon fuel production rate of 18.4 mM/h was obtained at a residence time of 50 min. The regulation of pH value from 6.8 to 8.5 significantly improved the activity of CvFAP, thereby obtaining an optimal conversion of 61.2%. The precipitation of palmitic acid caused a low conversion (37.9%) compared with the other fatty acids, further inhibiting hydrocarbon production. In such a cascade system, various oils can be converted to hydrocarbon fuels with a concentration of 8.97–15.3 mM. A high energy production rate of 204.3 kJ/L/h was achieved, which exhibited the advancement in high-quality biofuel production.

A comprehensive analysis on the synthesis of value-added chemicals via slow pyrolysis: Valorisation of rapeseed residue, whitewood, and seaweed (Laminaria digitata)

Pyrolysis has emerged as a crucial thermochemical conversion technology in the field of biomass processing. Maximising the valorisation of biomass is an essential area of investigation, as it plays a pivotal role in understanding the economic viability and practical application of these advanced technologies. The novelty of this research is to investigate how slow pyrolysis and process interdependencies influence the synthesis of value-added products (bio-oil and biogas formation alongside biochar) from distinctly different UK-based biomass feedstocks: rapeseed residue, whitewood, and seaweed (Laminaria digitata). This research also analysed the chemical composition of these products to provide a holistic understanding of the reaction mechanisms involved in their formation. The maximum yield of bio-oil from lignocellulose-rich whitewood was due to the higher selectivity of several endothermic reactions including conversions of 5-hydroxymethylfurfural into cyclic C5-ketones and alkoxyphenols into cresols and aliphatic hydrocarbons, minimizing the biochar formation. The improvement of bio-oil yield from protein-rich seaweed and lipid-rich rapeseed residue was enabled by the formation of N-heterocyclics (e.g., via the Maillard reaction, Dieckmann cyclization, and Buchwald–Hartwig amination) and aliphatic hydrocarbons (e.g., via deamination of fatty amides and nitriles and decarboxylation of fatty acids), respectively. Meanwhile, the dealkylation and demethoxylation of alkoxyphenols and alkylphenols were responsible for the increased content of hydrocarbons in biogas. The findings provide valuable insights into the maximum valorisation of different types of UK-based biomass resources in slow pyrolysis for the production of biochars and lighter bio-oils to make pyrolysis a key process in biorefineries.

Photo-driven enzymatic decarboxylation of fatty acids for bio-aviation fuels production in a continuous microfluidic reactor

Fatty acid photodecarboxylase derived from Chlorella variabilis NC64A (CvFAP) is a novel enzyme that can convert fatty acids to corresponding C1-shortened alkanes under blue light illumination, which provides an alternative approach for the production of bio-aviation fuels under mild conditions. To date, the production of bio-aviation fuel using CvFAP is severely limited by an inefficient reactor. Microfluidic reactors have attracted significant attention owing to their high mass-transfer efficiency and low light attenuation in continuous photobiocatalysis. In this study, a microfluidic photobioreactor was proposed for the continuous photoenzymatic decarboxylation of palmitic acid for the first time. The optimal palmitic acid conversion of 96.7% was obtained at a flow rate of 10 μL/min, a blue light intensity of 200 μmol/(m2 s), a reaction temperature of 30 °C, a catalyst concentration of 2.4 mg/mL, a substrate concentration of 12 mM, and a cosolvent volume ratio of 30%. The maximum pentadecane production rate of 59.8 mM/h was achieved. The highest turnover frequency of CvFAP up to 19,186/h, as ever reported, was obtained at a flow rate of 40 μL/min. Meanwhile, the energy yield of 33.6 kJ/g and energy production rate of 533.5 kJ/L/h were achieved in continuous bio-aviation fuels production. Taken together, the continuous photoenzymatic decarboxylation of fatty acids in a microfluidic photobioreactor is a promising approach for bio-aviation fuels production.

Dimer-assisted mechanism of (un)saturated fatty acid decarboxylation for alkene production

The enzymatic decarboxylation of fatty acids (FAs) represents an advance toward the development of biological routes to produce drop-in hydrocarbons. The current mechanism for the P450-catalyzed decarboxylation has been largely established from the bacterial cytochrome P450 OleTJE. Herein, we describe OleTPRN, a poly-unsaturated alkene-producing decarboxylase that outrivals the functional properties of the model enzyme and exploits a distinct molecular mechanism for substrate binding and chemoselectivity. In addition to the high conversion rates into alkenes from a broad range of saturated FAs without dependence on high salt concentrations, OleTPRN can also efficiently produce alkenes from unsaturated (oleic and linoleic) acids, the most abundant FAs found in nature. OleTPRN performs carbon-carbon cleavage by a catalytic itinerary that involves hydrogen-atom transfer by the heme-ferryl intermediate Compound I and features a hydrophobic cradle at the distal region of the substrate-binding pocket, not found in OleTJE, which is proposed to play a role in the productive binding of long-chain FAs and favors the rapid release of products from the metabolism of short-chain FAs. Moreover, it is shown that the dimeric configuration of OleTPRN is involved in the stabilization of the A-A' helical motif, a second-coordination sphere of the substrate, which contributes to the proper accommodation of the aliphatic tail in the distal and medial active-site pocket. These findings provide an alternative molecular mechanism for alkene production by P450 peroxygenases, creating new opportunities for biological production of renewable hydrocarbons.