Selective Deoxygenation Research Articles

Selective direct deoxygenation of m-cresol on Heusler alloy catalysts via precise control of electronic structure: An integrated density function theory and microkinetic modeling study

Directional designing a catalyst with high direct deoxygenation selectivity of Phenols during hydrodeoxygenation (HDO), remains a formidable challenge in cost-effectively converting biomass to bio-fuel and chemicals. Herein, we evaluated for the first time the catalytic performance of Heusler alloy surfaces for HDO process of m-cresol at the atomic scale. The direct deoxygenation (DDO) route of m-cresol on the Co2FeGa (110) surface at 573.15 K exhibited relatively low kinetic (1.20 eV) and thermodynamic (−0.04 eV) barriers, leading to high selectivity (near 100 %) for toluene production. The degree of rate control (DRC) analysis revealed that direct dehydroxylation constituted the rate-limiting elementary reaction. Additionally, by tailoring the Ga and Ge ratio on the Co2FeGa1-xGex (110) surface, an almost linear relationship (R2 = 0.95) was discovered between activation energy of C-OH and the d-band center energy of the Fe element in the unit cell. Both the activation energy of C-OH and d-band center energy of the Fe decreased with increasing Ge/Ga substitution ratio. This research unveils for the first time the catalytic performance of Heusler alloy for the selective direct deoxygenation of m-cresol, but also suggest the possibility tuning d-band center of Heusler alloys to precisely tailor the selectivity of DDO during HDO process.

Sustainable ammonia and amines from chitin

Efforts are underway to explore alternative methods to the Haber-Bosch process for sustainable ammonia production, while the potential for ammonia extraction from natural nitrogenous biomass is under-exploited. Here, a synergistic catalytic strategy involving acid and modified Ru-based catalysts is communicated for the direct production of amines and ammonia from chitin. Phosphoric acid promotes the cleavage of ether bonds in biomass polymers and also serves to protect amino groups from being removed. Selective hydrogenation, deoxygenation, and amination can be achieved by controllably adjusting the ratio of Ru0/Run+. The utilization of nitrogen atoms in chitin can reach up to 95 % (21 % amines, 74 % ammonium), and the catalytic process is applicable to waste shrimp shells. This study demonstrates the possibility of efficient production of nitrogen-containing compounds from abundant biopolymers.

Renewable Diesel Production over Mo-Ni Catalysts Supported on Silica

Nickel catalysts promoted with Mo and supported on silica were studied for renewable diesel production from triglyceride biomass, through the selective deoxygenation process. The catalysts were prepared by wet co-impregnation of the SiO2 with different Ni/(Ni + Mo) atomic ratios (0/0.84/0.91/0.95/0.98/1) and a total metal content equal to 50%. They were characterized by XRD, XPS, N2 physisorption, H2-TPR, and NH3-TPD. Evaluation of the catalysts for the transformation of sunflower oil to renewable (green) diesel took place in a high-pressure semi-batch reactor, under solvent-free conditions. A very small addition of Mo, namely the synergistic Ni/(Ni + Mo) atomic ratio equal to 0.95, proved to be the optimum one for a significant enhancement of the catalytic performance of the metallic Ni/SiO2 catalyst, achieving 98 wt.% renewable diesel production. This promoting action of Mo has been attributed to the significant increase of the metallic Ni active phase surface area, the suitable regulation of surface acidity, the acceleration of the hydro-deoxygenation pathway (HDO), the creation of surface oxygen vacancies, and the diminution of coke formation provoked by Mo addition.

Production of Sustainable Liquid Fuels

As the world aims to address the UN Sustainable Development Goals (SDGs), it is becoming more urgent for heavy transportation sectors, such as shipping and aviation, to decarbonise in an economically feasible way. This review paper investigates the potential fuels of the future and their capability to mitigate the carbon footprint when other technologies fail to do so. This review looks at the technologies available today, including, primarily, transesterification, hydrocracking, and selective deoxygenation. It also investigates the potential of fish waste from the salmon industry as a fuel blend stock. From this, various kinetic models are investigated to find a suitable base for simulating the production and economics of biodiesel (i.e., fatty acid alkyl esters) and renewable diesel production from fish waste. Whilst most waste-oil-derived biofuels are traditionally produced using transesterification, hydrotreating looks to be a promising method to produce drop-in biofuels, which can be blended with conventional petroleum fuels without any volume percentage limitation. Using hydrotreatment, it is possible to produce renewable diesel in a few steps, and the final liquid product mixture includes paraffins, i.e., linear, branched, and cyclo-alkanes, with fuel properties in compliance with international fuel standards. There is a wide range of theoretical models based on the hydrodeoxygenation of fatty acids as well as a clear economic analysis that a model could be based on.

Mechanism of initial activation of carbon–oxygen bonds for deoxidation of acetic acid

Producing valuable fuel-ranged hydrocarbons from cellulosic biomass is an effective approach to addressing potential energy issues. However, the cellulose-derived bio-oil may contain carboxylic acid components that contribute to the unfavorable acidic and corrosive nature, which necessitates upgrading through the hydrodeoxygenation (HDO) treatment using heterogeneous catalysis. Here, we performed reactive force-field molecular dynamics (ReaxFF-MD) to study the hydrogenolysis, dehydrogenation and decarboxylation mechanisms of the acetic acid model compound on the Ni-based catalyst. Comparative analysis of the activation of C–O and C=O bonds was presented, followed by an examination of the associative desorption of H2 and the dynamic evolution of main intermediates. Furthermore, the conversion pathways of key intermediates were determined and four main pathways for ethanol generation and the temperature-response mechanism for coking formation were proposed. This mechanism diagram explains the strong effects of a hydrogen environment in biomass-related reactions, highlighting the dynamic mechanism of selective hydrogenation and deoxygenation of carbon–oxygen bonds.

Selective deoxygenation of biomass-derived carbonyl compounds on Zn via electrochemical Clemmensen reduction

Selective deoxygenation of biomass-derived carbonyl compounds on Zn via electrochemical Clemmensen reduction

Development of supported intermetallic compounds: advancing the Frontiers of heterogeneous catalysis.

Intermetallic compound (IMC) catalysts have garnered significant attention due to their unique surface and electronic properties, which can lead to enhanced catalytic performance compared to traditional monometallic catalysts. However, developing IMC materials as high-performance catalysts has been hindered by the inherent complexity of synthesizing nanoparticles with well-defined bulk and surface compositions. Achieving precise control over the composition of supported bimetallic IMC catalysts, especially those with high surface area and stability, has proven challenging. This review provides a comprehensive overview of the recent progress in developing supported IMC catalysts. We first examine the various synthetic approaches that have been explored to prepare supported IMC nanoparticles with phase-pure bulk structures and tailored surface compositions. Key factors influencing the formation kinetics and compositional control of these materials are discussed in detail. Then the strategies for manipulating the surface composition of supported IMCs are delved into. Applications of high-performance supported IMCs in important reactions such as selective hydrogenation, reforming, dehydrogenation, and deoxygenation are comprehensively reviewed, showcasing the unique advantages offered by these materials. Finally, the prevailing research challenges associated with supported IMCs are identified, including the need for a better understanding of the composition-property relationships and the development of scalable synthesis methods. The prospects for the practical implementation of these versatile catalysts in industrial processes are also highlighted, underscoring the importance of continued research in this field.

Heterogeneous La and CeOx co-promoted SAPO-11 catalyst for catalytic upgrading of cellulose-derived volatile and methanol into hydrocarbon-rich fuels

In this paper, a series of La–Ce co-doped SAPO-11 catalysts with various La to Ce ratio were developed via wet impregnation method then employed in catalytic cellulose and methanol co-pyrolysis to produce hydrocarbon-rich biofuels. Comprehensive characterization technologies including X-ray diffraction, X-ray photoelectron spectroscopy, N2 physisorption, scanning electron microscope, transmission electron microscope, ammonia temperature-programmed desorption, Pyridine-infrared, and thermal gravimetric analyzer, were conducted to unveil the physicochemical properties, structure properties and acidity of as-prepared catalysts. Additionally the product content; aromatic selectivity and synergetic effect were also investigated. Additionally possible conversion pathway, deactivation mechanism and reusability were also deduced. La and Ce showed a certain synergetic effect and exhibited superior catalytic deoxygenation activity due to La–O and Ce-Ox species, suitable Brønsted acidity, abundant oxygen vacancies and enhanced mesopores structure, which was facilitated to promote the selectivity of hydrocarbon. Higher La content was fascinated to generate furans and ketones compounds, due to lower Brønsted acid site and smaller specific surface area. In contrast, higher CeOx content was beneficial to hydrocarbon formation via Diels-Alder reaction and dehydro-aromatization due to higher Brønsted acid site, total acidity, higher specific surface area, mesoporous pore volume as well as strong oxygen affinity of CeOx. The maximum proportion hydrocarbon, aromatics and minimum contents coke was obtained over 1La–1Ce/SAPO-11 were 77.96 %, 55.82 % and 9.81 %, respectively. Additionally, 1La–1Ce/SAPO-11 catalyst exhibited outstanding reusability and stability after four cycles; nearly ∼96 % relative content of hydrocarbon was maintained after regeneration test. Hence, the insight into the synergetic catalysis between La and CeOx species could provide a new potential possible pathway for design and synthesized efficient and eco-friendly bimetallic catalyst for selective catalytic deoxygenation organic solid waste biomass for valuable chemicals.

Selective Deoxygenation of Waste Cooking Oil to Diesel-Like Hydrocarbons Using Supported and Unsupported NiMoS2 Catalysts

Selective Deoxygenation of Waste Cooking Oil to Diesel-Like Hydrocarbons Using Supported and Unsupported NiMoS₂ Catalysts

Methane-assisted selective bio-oil deoxygenation for high-quality renewable fuel production: A rational catalyst design and mechanistic study

Methane is the main component of naturally abundant natural gas resources and is under-utilized. Bio-oil is a promising energy source with lower economic and environmental costs compared to fossil fuels. However, pyrolysis-derived bio-oil obtained from lipid sources is hindered by high oxygen content and unsaturated species. In this work, an Ir-Ga-Ce/TiO2-A catalyst is theorized and subsequently tailored to optimize deoxygenation product oil quality. After synthesis, 2-hexyl-1-decanol is employed as a model compound to understand the mechanism of deoxygenation under different atmospheres and rationalize the assistance of methane compared to inerts. It is found that methane significantly facilitates the deoxygenation and chain growth reactions by direct incorporation into the paraffinic and naphthenic liquid-phase products. In the gas-phase products, isotopic labeling studies reveal that methane is directly involved with deoxygenation as a major contributor to CO2, and potentially CO. The role of each catalyst component (Ir, Ga, Ce, and TiO2-A) is elucidated, resulting in a sophisticated network tailored for deoxygenation of alcohols with the assistance of methane. The Ir-Ga-Ce/TiO2-A catalyst is then subject to testing on a real pyrolysis-derived bio-oil and shows 84.7% deoxygenation, 0.07% water content by weight, 0.2 (mg KOH g−1) TAN and greater than 1.5% methane conversion, while maintaining the product oil’s structural integrity as a renewable fuel. This work illustrates the potential of a methane-assisted deoxygenation process and explains multiple roles methane can play in achieving better reaction performance and product quality. The effective utilization of methane for bio-oil deoxygenation demonstrates unique benefits for the natural gas and fatty waste industries.

Catalyst- and Stoichiometry-Dependent Deoxygenative Reduction of Esters to Ethers or Alcohols with Borane-Ammonia.

A facile and selective room temperature deoxygenation of both aromatic and aliphatic carboxylic esters to ethers has been achieved by regulating the stoichiometry of the reductant, BH3-NH3, and the catalyst, TiCl4. This first, practical borane-mediated process is compatible with various potentially sensitive functional groups and is applicable to the deoxygenative ether formation from typically challenging aromatic acid esters. Substituting BF3-Et2O as the catalyst alters the reaction pathway, reducing the esters to alcohols. Mechanistic insights are provided by NMR spectroscopy, deuterium labeling, and kinetic isotope studies.

Al-Doped Core-Shell-Structured Ni@Mesoporous Silica for Highly Selective Hydrodeoxygenation of Lignin-Derived Aldehydes.

Selective deoxygenation of chemicals using non-noble metal-based catalysts poses a significant challenge toward upgrading biomass-derived oxygenates into advanced fuels and fine chemicals. Herein, we report a bifunctional core-shell catalyst (Ni@Al3-mSiO2) consisting of Ni nanoparticles closely encapsulated by the Al-doped mesoporous silica shell that achieves 100% vanillin conversion and >99% yield of 2-methoxy-4-methylphenol under 1 MPa H2 at 130 °C in water. Due to the unique mesoporous core-shell structure, no significant decrease in catalytic activity was observed after 10 recycles. Furthermore, incorporating Al atoms into the silica shell significantly increased the number of acidic sites. Density functional theory calculations reveal the reaction pathway of the vanillin hydrodeoxygenation process and uncover the intrinsic influence of the Al sites. This work not only provides an efficient and cost-effective bifunctional hydrodeoxygenation catalyst but also offers a new synthetic protocol to rationally design promising non-noble metal catalysts for biomass valorization or other widespread applications.

Revealing the Mechanistic Details for the Selective Deoxygenation of Carboxylic Acids over Dynamic MoO3 Catalysts

Revealing the Mechanistic Details for the Selective Deoxygenation of Carboxylic Acids over Dynamic MoO₃ Catalysts

Selective catalytic deoxygenation of palm oil to produce green diesel over Ni catalysts supported on ZrO2 and CeO2–ZrO2: Experimental and process simulation modelling studies

The selective deoxygenation of palm oil to produce green diesel has been investigated over Ni catalysts supported on ZrO2 (Ni/Zr) and CeO2–ZrO2 (Ni/CeZr) supports. The modification of the support with CeO2 acted to improve the Ni dispersion and oxygen lability of the catalyst, while reducing the overall surface acidity. The Ni/CeZr catalyst exhibited higher triglyceride (TG) conversion and yield for the desirable C15–C18 hydrocarbons, as well as improved stability compared to the unmodified Ni/Zr catalyst, with TG conversion and C15–C18 yield remaining above 85% and 80% respectively during 20 h of continuous operation at 300 oC. The high C17 yields also revealed the dominance of the deCOx (decarbonylation/decarboxylation) pathway. A fully comprehensive process simulation model has been developed to validate the experimental findings in this study, and a very good validation with the experimental data has been demonstrated. The model was then further utilised to investigate the effects of temperature, H2 partial pressure, H2/oil feed ratio and LHSV. The model predicted that maximum triglyceride conversion was attainable at reaction conditions of 300 °C temperature, 30 bar H2 partial pressure, H2/oil of 1000 cm3/cm3 feed ratio and 1.2 h−1 LHSV.

Synthesis and catalytic performance of nickel phosphinite pincer complexes in deoxygenative hydroboration of amides.

A series of imino-POCNR, amino-POCNR2, and bis(phosphinite) POCOP pincer complexes of Ni(II) were prepared and tested in catalytic deoxygenative hydroboration of amides with HBPin to the corresponding amines. In contrast to the deoxygenative hydrosilylation approach, primarily developed for tertiary amides, superior reactivity in Ni-catalyzed deoxygenative hydroboration was demonstrated for secondary carboxamides. The bis(phosphinite) hydride complex (POCOP)NiH proved the most active in these reactions, tolerating potentially reducible functionalities such as internal alkenes, esters, nitriles, heteroaromatic compounds, and tertiary amides. Preferable hydroboration of secondary amides was also demonstrated in the presence of primary amide functionalities. The reactions were conducted at 60-80 °C, representing a rare example of a base-metal catalytic system for selective deoxygenation of secondary amides to the corresponding amines under mild conditions. In contrast to secondary amides, deoxygenative hydroboration of primary amides was demonstrated using an iminophosphinite pre-catalyst (POCNDmp)Ni(CH2TMS) (Dmp = 2,6-Me2C6H3). Deoxygenation reactions were suggested to proceed via a direct C-O bond cleavage mechanism, which is triggered by dehydrogenative N-borylation to access more electrophilic N-borylamides amenable to the addition of HBPin to the carbonyl group.

Highly stable Mo-based bimetallic catalysts for selective deoxygenation of oleic acid to fuel-like hydrocarbons

To develop efficient, economical and environmentally friendly Mo-based bimetallic Al/MCM-41 catalysts for catalytic oleic acid pyrolysis into hydrocarbon-like upgrading biofuel, a series of metal-modified Mo-based catalysts was successfully synthesized. The effects of different metal oxide types (Zr, Zn, Pt, Cu, Co, Ce, Ni) and Ce to Mo mixed ratios were compared and characterized by XRD, BET, NH3-TPD, XPS, SEM and TEM technologies. Simultaneously, the deoxygenation effect and reusability properties were also evaluated by Py-GC/MS and TGA. The results showed that the molybdenum-based bimetallic catalyst exhibited superior deoxygenation activity (Ce>Cu>Zn>Ni>Zr∼Pt>Co) in the decarbonylation and decarboxylation pathways. Higher deoxygenation activity was related to rich surface Ce-□-Mo synergistic oxygen vacancies, suitable metal-Lewis and Brønsted acidity and excellent textural properties. A higher Ce content was beneficial to HC and aromatic formation due to a higher specific surface area and mesoporous volume, and a higher Mo content facilitated olefin and alkane conversion due to a higher Brønsted acid intensity and smaller pore size. The 3Ce-1Mo/Al-MCM-41 exhibited excellent catalytic activity and promising reusability by yielding 97.72% hydrocarbons, 75.33% aromatic content and 57.92% MAHs due to the synergistic effect between Ce and MoOx, rich surface Ce-□-Mo synergistic oxygen vacancies and suitable metal-Lewis and Brønsted acid intensities that contributed to better reaction activity and coke resistance and activated the CO of oleic acid. The slight reduction in HCs was mainly due to the loss of active metal sites and coke deposition. Furthermore, the synergistic effect of Ce and MoOx species obviously advanced the reaction activity and coke resistance.

Development of nickel catalysts supported on silica for green diesel production

Two series of nickel catalysts supported on silica were prepared and evaluated for the selective deoxygenation of sunflower oil into green diesel, under conditions without solvent. The catalysts were characterized with various techniques (N2 physisorption, CO chemisorption, XRD, SEM-EDS, TEM, H2-TPR, NH3-TPD). The first series involves catalysts with Ni content ranging between 10 and 60 wt%, synthesized by successive dry impregnation. The green diesel in the liquid product seems to depend mainly on the active nickel surface and the moderate acidity, following a volcano trend which is maximized over the sample with 50 wt% Ni loading. The second series concerns catalysts with 50 wt% Ni, synthesized by the use of four different techniques: Successive Dry Impregnation (SDI), Wet Impregnation (WI), using Ni(en)3(ΝΟ3)2 (en: ethylene diamine) as the Ni precursor and Deposition – Precipitation at room temperature (DP-NH3), Deposition – Precipitation at high temperature (DP-Urea), using Ni(ΝΟ3)2 as the Ni precursor. SDI or WI results mainly to granular nickel supported nanoparticles, whereas DP-NH3 and mainly DP-Urea to the formation of filamentous structures of a nickel phyllosilicate phase. The performance of the catalysts towards the production of green diesel follows the order WI>SDI> DP-NH3 >DP-Urea. The catalyst synthesized by WI exhibits the higher active surface in combination with high population of sites of moderate acidity. The catalysts prepared by DP, although exhibiting a very high surface area and a very high nickel dispersion, did not appear more effective in the n-alkanes production, due to the formation of a very well dispersed nickel phyllosilicate phase, but not fully reducible even at very high temperatures and thus inactive in the selective deoxygenation of sunflower oil.

The Investigation of a Switchable Iridium Catalyst for the Hydrogenation of Amides: A Case Study of C–O Versus C–N Bond Scission

This Letter studies a switchable Cp*-iridium catalyst supported by a 1,10-phenanthroline-2,9-diol (Cp* = pentamethylcyclopentadienyl) for the hydrogenation of amides. Depending on the reaction conditions, a single catalyst provides access to two distinct products arising from either C–O or C–N bond scission of the amide. Under typical hydrogenation conditions (40 bar H2, 110 °C), selective deoxygenation of the amide is observed without acidic additives. Investigations were performed to determine the origin of the C–O bond-scission products. Upon the addition of base, however, a switch in the selectivity was observed providing C–N bond-cleaved products. These studies present fundamental insights for the rational design of hydrogenation catalysts.

Selective CO2 deoxygenation to CO in chemically looped reverse water–gas shift using iron-based oxygen carrier

Chemical-looped reverse water–gas shift reaction was investigated using transition metal/metal oxides as oxygen carriers. Iron is identified as the only promising oxygen carrier that shows compelling CO 2 splitting reactivity. A chemically looped reverse water–gas shift reaction was developed using an iron-based oxygen carrier. Compared with conventional catalytic conversion processes, the chemical looping method has the advantage of high selectivity and cheap materials cost due to the separation of CO2 splitting and H2 oxidation half-reactions that are enabled by earth-abundant transition metal oxygen carriers. However, for such process to be economically attractive, the operation temperature should ideally be low enough such that low-grade industrial waste heat can be utilized. In other words, the reactivity of oxygen carriers toward the aforementioned half-reactions is most critical. To address the materials challenge, four transition metal-based oxygen carriers, i.e., iron, nickel, manganese, and copper, are studied using temperature-programmed techniques under H2 and CO2. Iron is identified to be the only oxygen carrier reactive toward CO2 splitting and capable of completing the redox cycle at 450 °C with 100% reverse water–gas shift selectivity. Although the thermal stability of the iron oxygen carriers shows room for improvement, our work demonstrates the great potential of a scalable and economically viable route for CO2 conversion that is compatible with current industrial processes.Graphical abstract

Na2S-Mediated One-Pot Selective Deoxygenation of α-Hydroxyl Carbonyl Compounds including Natural Products.

A practical method for the deoxygenation of α-hydroxyl carbonyl compounds under mild reaction conditions is reported here. The use of cheap and easy-to-handle Na2S·9H2O as the reductant in the presence of PPh3 and N-chlorosuccinimide (NCS) enables the selective dehydroxylation of α-hydroxyl carbonyl compounds, including ketones, esters, amides, imides and nitrile groups. The synthetic utility is demonstrated by the late-stage deoxygenation of bioactive molecule and complex natural products.