Search Results (25)

Black liquor, the side stream from Kraft pulping, is a promising feedstock for the production of renewable fuels via hydrothermal liquefaction (HTL). However, further upgrading of the black liquor HTL oil is required to reduce the oxygen content for fuel use. In this work, the hydrodeoxygenation (HDO) of black liquor HTL oil model compounds was investigated to enhance the understanding of catalyst activity and selectivity under hydrothermal conditions. The study focused on isoeugenol and 4-methylcatechol as model compounds, representing different functionalities in black liquor-derived HTL-oil. Sulfided NiMo catalysts supported on titania, zirconia, activated carbon, and α-alumina were evaluated in batch mode at subcritical and supercritical upgrading using hydrogen gas. The results show that isoeugenol was fully converted in all experiments, while 4-methylcatechol conversion varied depending on the catalyst and reaction conditions. Phenols were obtained as the main products and the maximum degree of deoxygenation achieved was around 40%. This research provides insights into the potential of hydrothermal HDO for upgrading BL-derived biocrudes, emphasising the importance of catalyst selection and reaction conditions in hydrothermal conditions. Full article

Bio-oil is a potential source for the production of alternative fuels and chemicals. In this work, Ni-V bimetallic zeolite catalysts were synthesized and evaluated in in situ catalytic hydrodeoxygenation (HDO) of pyrolysis volatiles of pine nut shell for upgraded bio-oil products. The pH and lower heating value (LHV) of the upgraded bio-oil products were improved by in situ catalytic HDO, while the moisture content and density of the oil decreased. The O/C ratio of the upgraded bio-oil products decreased significantly, and the oxygenated compounds in the pyrolysis volatiles were converted efficiently via deoxygenation over Ni-V zeolite catalysts. The highest HDO activity was obtained with NiV/MesoY, where the obtained bio-oil had the lowest O/C atomic ratio (0.27), a higher LHV (27.03 MJ/kg) and the highest selectivity (19.6%) towards target arenes. Owing to the more appropriate pore size distribution and better dispersion of metal active sites, NiV/MesoY enhanced the transformation of reacting intermediates, obtaining the dominant products of phenols and arenes. A higher HDO temperature improved the catalytic activity of pyrolysis volatiles to form more deoxygenated arenes. Higher Ni loading could generate more metal active sites, thus promoting the catalyst’s HDO activity for pyrolysis volatiles. This study contributes to the development of cost-efficient and eco-friendly HDO catalysts, which are required for producing high-quality biofuel products. Full article

Single-ring aromatic compounds including BTX (benzene, toluene, xylene) serve as essential building blocks for high-performance fuels and specialty chemicals, with extensive applications spanning polymer synthesis, pharmaceutical manufacturing, and aviation fuel formulation. Current industrial production predominantly relies on non-renewable petrochemical feedstocks, posing the dual challenges of resource depletion and environmental sustainability. The catalytic hydrodeoxygenation (HDO) of lignin-derived phenolic substrates emerges as a technologically viable pathway for sustainable aromatic hydrocarbon synthesis, offering critical opportunities for lignin valorization and biorefinery advancement. This article reviews the relevant research on the conversion of lignin-derived phenolic compounds’ HDO to benzene and aromatic hydrocarbons, systematically categorizing and summarizing the different types of catalysts and their reaction mechanisms. Furthermore, we propose a strategic framework addressing current technical bottlenecks, highlighting the necessity for the synergistic development of robust heterogeneous catalysts with tailored active sites and energy-efficient process engineering to achieve scalable biomass conversion systems. Full article

The supported Ni-P catalysts (marked as s-Ni-P/Hβ(3) and s-Ni-P/Ce-β(3)) were prepared by an incipient wetness step-impregnation method, and characterized by XRD, N₂ physisorption, TEM, XPS, and NH₃-TPD. The catalytic hydrodeoxygenation (HDO) performance was assessed using phenol in water (5.0 wt%) or in decalin (1.0 wt%) as the feed. After the introduction of Ce, the conversion of phenol increased due to the high dispersity of the active site. However, compared to s-Ni-P/Hβ(3), the amount of total and strong acid sites of s-Ni-P/Ce-β(3) decreased, restraining the cycloisomerization of cyclohexane to form methyl-cyclopentane. Moreover, the kinetics of the APHDO and OPHDO of phenol catalyzed by s-Ni-P/Hβ(3) and s-Ni-P/Ce-β(3) were investigated. Full article

Lanthanum (La) integration (at various nominal contents) in SBA-15 prepared under acidic medium was intended from corresponding direct nitrate addition during mesoporous silica formation. Materials were impregnated with Pt (1.5 wt%) and studied through several textural (N₂ physisorption), structural (XRD, TG-DTG), and surface (FTIR, STEM-HAADF, SEM-EDS, NH₃, and CO₂ TPD) instrumental techniques. Pt-impregnated solids were tested in phenol hydrodeoxygenation (HDO, T = 250 °C, 3.2 MPa, batch reactor, n-decane as solvent). Catalytic activity (in pseudo-first-order kinetic constant, k_HDO basis) was not directly related to Pt dispersion, which was not determined by nominal rare earth content. Determining the actual composition of modified SBA-15 materials is crucial in reaching sound conclusions regarding their physicochemical properties, especially when La modifier is directly added during mesoporous matrix formation, where efficient interaction among constituents could be difficult to get. Otherwise, results from some characterization techniques (N₂ physisorption and FTIR, for instance) could be misleading and even contradictory. Indeed, extant modifier precursors, when under SBA-15 synthesis conditions, could affect the properties of prepared materials even though they were absent in obtained formulations. Performing simple compositional analysis could eliminate uncertainties regarding the role of various modifiers on characteristics of final catalysts. However, several groups have failed in doing so. Full article

Currently, many research projects are focused on the conversion of renewable raw materials into chemicals and fuels. Lignocellulosic biomass is a raw material used for the production of bio-oils and black liquors. These biomass-derived fractions offer promising paths for the production of valuable chemical products. Various catalytic methods have been investigated for upgrading the biomass-derived fractions. Researchers are interested in the hydrodeoxygenation process (HDO); in this process, the oxygen groups are eliminated by breaking the C-O bonds and water as a product. Incorporating heterogeneous catalysts (i.e., noble metals, transition metals, and metal sulfides) improves this process. Most HDO review articles describe catalytic results for model phenolic compounds. However, there is also a need to investigate the catalytic activity of real biomass-derived fractions. This paper explains research results regarding the upgrading of lignin-derived fractions (i.e., black liquors) by HDO. The paper has been organized according to the type of heterogeneous catalyst and shows compelling results based on different experimental conditions. The final sections present an analysis of the documented results and outline perspectives about integrating lignin into the biorefinery framework. Full article

Bio-oil upgrading to produce biofuels and chemicals has become an attractive topic over the past decade. However, the design of cost- and performance-effective catalysts for commercial-scale production remains a challenge. Herein, commercial titania (TiO₂) was used as the support of cobalt (Co)-based catalysts (Co/TiO₂) due to its low cost, high availability, and practicability for commercialization in the future. The Co/TiO₂ catalysts were made with two different forms of TiO₂ (anatase [TiO₂–A] and rutile [TiO₂–R]) and comparatively evaluated in the hydrodeoxygenation (HDO) of 4-propylguaicol (4PG), a lignin-derived model compound. Both Co/TiO₂ catalysts promoted the HDO of 4PG following a similar pathway, but the Co/TiO₂–R catalyst exhibited a higher activity in the early stages of the reaction due to the formation of abundant Ti³⁺ species, as detected by X-ray photoelectron spectroscopy (XPS) and hydrogen–temperature programed reduction (H₂–TPR) analyses. On the other hand, the Co/TiO₂–A catalyst possessed a higher acidity that enhanced propylcyclohexane production at prolonged reaction times. In terms of reusability, the Co/TiO₂–A catalyst showed a higher stability (less Co leaching) and reusability compared to Co/TiO₂–R, as confirmed by transmission electron microscopy (TEM) and inductively coupled plasma optical emission spectroscopy (ICP-OES) analyses. The HDO of the real bio-oil derived from pyrolysis of Leucaena leucocephala revealed that the Co/TiO₂–A catalyst could convert high oxygenated aromatics (methoxyphenols, dimethoxyphenols, and benzenediols) to phenols and enhanced the phenols content, hinting at its potential to produce green chemicals from bio-feedstock. Full article

This comprehensive review explores recent catalyst advancements for the hydrodeoxygenation (HDO) of aromatic oxygenates derived from lignin, with a specific focus on the selective production of valuable aromatics under moderate reaction conditions. It addresses critical challenges in bio-crude oil upgrading, encompassing issues related to catalyst deactivation from coking, methods to mitigate deactivation, and techniques for catalyst regeneration. The study investigates various oxygenates found in bio-crude oil, such as phenol, guaiacol, anisole, and catechol, elucidating their conversion pathways during HDO. The review emphasizes the paramount importance of selectively generating arenes by directly cleaving C–O bonds while avoiding unwanted ring hydrogenation pathways. A comparative analysis of different bio-crude oil upgrading processes underscores the need to enhance biofuel quality for practical applications. Additionally, the review focuses on catalyst design for HDO. It compares six major catalyst categories, including metal sulfides, transition metals, metal phosphides, nitrides, carbides, and oxides, to provide insights for efficient bio-crude oil upgrading toward sustainable and eco-friendly energy alternatives. Full article

This study aims to examine the hydrodeoxygenation (HDO) of vanillin, an oxygenated phenolic compound present in bio-oil, into creosol. Biochar residue generated when wood is slowly pyrolyzed is utilized as a catalyst support. To improve biochar’s physicochemical properties, H₂SO₄ (sulfuric acid) and KOH (potassium hydroxide) are used as chemical activators. By means of a wet impregnation method with nickel salt, an Ni/biochar catalyst was prepared and utilized in the HDO of vanillin using a 100 mL Parr reactor, catalyst loading 0.4–0.8 g, temperature 100 °C to 150 °C, hydrogen (H₂) pressures of 30 to 50 bar, and a stirring rate of 1000 rpm. The prepared catalysts were characterized with the nitrogen-sorption isotherm technique, carbon dioxide temperature-programmed desorption (CO₂-TPD), scanning electron microscopy (SEM) coupled with energy dispersed X-ray analysis (EDX), X-ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FTIR). Based on chemical treatment, Ni/biochar (KOH) pore sizes were found to be dominated by mesopores, with a surface area increase of 64.7% and a volume increase of 65.3%, while Ni/biochar (H₂SO₄) was mostly microporous and mesoporous, with an area increase of 372.3% and a volume increase of 256.8% in comparison to Ni/biochar (74.84 m²g⁻¹ and 0.095 cm³g⁻¹). Vanillin conversion of up to 97% with 91.17% selectivity to p-creosol was obtained over Ni/biochar catalyst; in addition to being highly selective and active for p-creosol, a plausible fuel, the catalyst was stable after four cycles. Chemical treatments of the biochar support resulted in improved physicochemical properties, leading to improved catalytic performance in terms of vanillin conversion and p-creosol yield in the order Ni/biochar (H₂SO₄) > Ni/biochar (KOH) > Ni/biochar. Full article

Binary Ni–Cu heterogeneous catalysts are known to demonstrate excellent activity in conventional hydrogenation of phenolic compounds, and Cu addition facilitates hydrodeoxygenation (HDO). In this study, we aimed to show the effect of Cu on the specific catalytic activity and selectivity of Ni–Cu catalysts in transfer hydrogenation, in which 2-PrOH was used as a solvent and an H donor. Catalytic transformations of anisole were studied in sub- and supercritical alcohol at 150 and 250 °C. The catalysts were prepared using an environmentally friendly supercritical antisolvent coprecipitation method, which makes it possible to obtain well-dispersed particles (less than 7 nm) at high metal loading (up to 50 wt.%). When copper is added, deactivation of the catalyst in transformations of anisole, including HDO, is observed. The experimental data and the appropriate kinetic analysis demonstrate that there is a decrease in the rate of anisole conversion accompanied by an increase in the concentration of acetone formed during the dehydrogenation of 2-PrOH. Full article

This work aims at assessing the hydrodeoxygenation (HDO) of phenol over a promising catalytic material: a CoMoS-based active phase with a Co/(Co + Mo) = 0.2, supported on a promising mixed oxide, Al₂O₃-TiO₂ (Al/Ti = 2). Particularly, to optimize the catalytic and kinetic performance of CoMoS/Al₂O₃-TiO₂, a response surface methodology (RSM) is carried out by following a Box–Behnken experimental design. The response variables are the initial reaction rate and the reaction selectivity, determined via a proper contribution analysis (𝜑) of both the direct hydrodeoxygenation (DDO) and the hydrogenation (HYD). At the same time, the operating conditions used as factors are the reaction temperature (280–360 °C), the total pressure (3–5.5 MPa), and the Mo loading (10–15 wt.%). The activity and selectivity are correlated to the catalysts’ physicochemical properties determined by XRD, UV-Vis DRS, TPR, and Raman Spectroscopy. Regarding the CoMo-based active phase, a Mo loading of 12.5 wt.% leads to the optimal reaction performance, which is associated with the lowest (Co + Mo)^oh/(Co + Mo)^th ratio. Concerning the operating conditions, a temperature of 360 °C and a total pressure of 5.5 MPa give rise to the optimal initial reaction rates, in which the DDO (𝜑 = 65%) is selectively favored over HYD (𝜑 = 35%). Full article

Hydrodeoxygenation (HDO) reaction is a route with much to offer in the conversion and upgrading of bio-oils into fuels; the latter can potentially replace fossil fuels. The catalyst’s design and the feedstock play a critical role in the process metrics (activity, selectivity). Among the different classes of catalysts for the HDO reaction, the transition metal phosphides (TMP), e.g., binary (Ni2P, CoP, WP, MoP) and ternary Fe-Co-P, Fe-Ru-P, are chosen to be discussed in the present review article due to their chameleon type of structural and electronic features giving them superiority compared to the pure metals, apart from their cost advantage. Their active catalytic sites for the HDO reaction are discussed, while particular aspects of their structural, morphological, electronic, and bonding features are presented along with the corresponding characterization technique/tool. The HDO reaction is critically discussed for representative compounds on the TMP surfaces; model compounds from the lignin-derivatives, cellulose derivatives, and fatty acids, such as phenols and furans, are presented, and their reaction mechanisms are explained in terms of TMPs structure, stoichiometry, and reaction conditions. The deactivation of the TMP’s catalysts under HDO conditions is discussed. Insights of the HDO reaction from computational aspects over the TMPs are also presented. Future challenges and directions are proposed to understand the TMP-probe molecule interaction under HDO process conditions and advance the process to a mature level. Full article

Biochar (BCR) was obtained from the pyrolysis of a palm-oil-empty fruit bunch at 773 K for 2 h and used as a catalyst for the hydrodeoxygenation (HDO) of guaiacol (GUA) as a bio-oil model compound. Brunauer–Emmet–Teller surface area analysis, NH₃ and CO₂-temperature-programmed desorption, scanning electron microscope–dispersive X-ray spectroscopy, CHN analysis and X-ray fluorescence spectroscopy suggested that macroporous and mesoporous structures were formed in BCR with a co-presence of hydrophilic and hydrophobic sites and acid–base behavior. A combination of infrared, Raman and inelastic neutron scattering (INS) was carried out to achieve a complete vibrational assignment of BCR. The CH–OH ratio in BCR is ~5, showing that the hydroxyl functional groups are a minority species. There was no evidence for any aromatic C–H stretch modes in the infrared, but they are clearly seen in the INS and are the majority species, with a ratio of sp³–CH:sp²–CH of 1:1.3. The hydrogen bound to sp²–C is largely present as isolated C–H bonds, rather than adjacent C–H bonds. The Raman spectrum shows the characteristic G band (ideal graphitic lattice) and three D bands (disordered graphitic lattice, amorphous carbon, and defective graphitic lattice) of sp² carbons. Adsorbed water in BCR is present as disordered layers on the surface rather than trapped in voids in the material and could be removed easily by drying prior to catalysis. Catalytic testing demonstrated that BCR was able to catalyze the HDO of GUA, yielding phenol and cresols as the major products. Phenol was produced both from the direct demethoxylation of GUA, as well as through the demethylation pathway via the formation of catechol as the intermediate followed by deoxygenation. Full article

Nickel-cobalt bimetallic catalysts supported on high surface area graphite with different Ni:Co ratios (3:1, 2:1 and 1:1) and the monometallic Ni and Co were prepared by wetness impregnation method. The catalysts were tested in hydrodeoxygenation (HDO) of guaiacol in the liquid phase at 50 bar of H₂ and 300 °C. The materials were characterized by N₂ adsorption–desorption, XRD, TEM/STEM, H₂-TPR, and CO-chemisorption to assess their properties and correlate them with the catalytic results. The activity was higher on the bimetallic catalysts and followed the trend NiCo_2:1/G ∼ NiCo_3:1/G > NiCo_1:1/G > Co/G > Ni/G. Also, selectivity results showed that Ni was more active in the hydrogenation favoring cyclohexanol production from phenol, while this was inhibited on the Co-containing catalysts. Hence, the results showed that synergy was created between Ni and Co and that their interaction, properties, and catalytic performance depend on the metals’ ratio. Full article

Constituents of liquid smoke possess a huge potential to be converted as value-added chemicals, such as flavoring, antiseptics, antioxidants, or even fossil oil substitutes. However, liquid smoke instability, led by the presence of oxygenate compounds, is an obstacle for further utilization and processing. On the other hand, catalyst efficiency in hydrodeoxygenation (HDO) remains challenging. Sarulla natural zeolite (Z), with abundant availability, has not been comprehensively investigated in the catalytic performance of HDO. In this study, Sarulla natural zeolite with different Si/Al ratios, which are activated by several concentrations of hydrochloric acid and nickel supported by Z (Ni-Z) synthesized by wet impregnation, were evaluated for HDO of liquid smoke, particularly in reducing oxygenate compounds. Catalyst morphology, surface area, pores, and crystallinity are investigated. Catalytic performances were evaluated, particularly on reducing oxygenate compounds and the shifting of phenol and its derivatives. Furthermore, the liquid smoke product of HDO was analyzed by gas chromatography-mass spectrometry (GC-MS). The data obtained reveal that the HDO process of liquid smoke with the Z3 catalyst shows the best activity compared to Z5 and Z7, with phenol conversion of 62.39% and 11.93% of alkoxy reduction. Meanwhile, the best Ni metal catalyst system activity was given by the Ni-Z5 catalyst compared to Ni-Z3 and Ni-Z7, where phenol conversion and alkoxy reduction were at 60.06% and 11.49%, respectively. Full article