Hydrodeoxygenation Reaction Research Articles

Competitive Hydrodeoxygenation and Hydrodenitrogenation Reactions in the Hydrotreatment of Fatty Acid and Amine Mixtures

Understanding how hydrotreating oxygen-containing compounds together with nitrogen-containing compounds affects the reactivity and selectivity is relevant for processing renewable feedstocks. In this work, competitive hydrodeoxygenation (HDO) and hydrodenitrogenation (HDN) reactions were studied by co-hydrotreating palmitic acid (C16 acid) and tetradecylamine (C14 amine) over a Pt/ZrO2 catalyst in a batch reactor. HDO proceeded faster than HDN in the studied system, and the deoxygenation reactions were found to have an inhibitory effect on HDN. Co-hydrotreating the C16 acid and the C14 amine expanded the reaction network from the individual HDO and HDN networks and changed the prevailing reaction pathways, initially in favor of oxygen removal. The formation of heavy secondary amides and amines through condensation reactions became increasingly favored as the share of C16 acid in the feed increased. For a given conversion level, the condensation product selectivity was observed to increase as the reaction temperature was decreased, whereas increasing the reaction temperature promoted the formation of the desired paraffins. This work described the ease of HDO compared to HDN, the role of condensation reactions in the co-hydrotreating reaction network, and the inhibitory effect on HDN thereof.

GuaiacolHDOon La‐modified Pt/Al2O3: Influence of rare‐earth loading

AbstractThe stability of the catalyst used in hydrodeoxygenation (HDO) of biomass‐derived oils needs improvement. La has been applied in delaying Al2O3phase‐change under reaction conditions. Lanthanum (0.5–8 wt.%)‐γ‐alumina was studied as Pt (1 wt.%) carrier aimed at guaiacol (GUA) HDO. Materials characterization included N2physisorption, X‐ray diffraction (XRD), thermal analysis, FTIR, UV–vis, and TPR. Solids pore size (~8–10 nm) was suitable for GUA (kinetic diameter~0.668 nm) hydrotreating. Mixed carriers were amorphous (XRD), suggesting well‐dispersed La domains; meanwhile, carbonates/bicarbonates were formed (from CO2) due to the basic surface properties of modified supports (FTIR). That could impart catalyst stability by inhibiting coking through the passivation of Lewis acidity on Al2O3. Pt reducibility increased with La loading in various formulations. However, that was not reflected in enhanced GUA HDO (T = 488 K and P = 3.2 MPa, batch reactor), presumably due to the strong metal–support interaction (SMSI), where LaOxcovered the metallic Pt particle surface. GUA HDO on various catalysts was approximated by pseudo‐first‐order kinetics (integral regime,k), where deviations were observed as La loading increased, presumably by an SMSI state that could affect the rate‐determining step of the reaction mechanism. Basic sites provided by rare‐earth could contribute to altering HDO reaction pathways as well. At 1 wt.% rare‐earth, GUA HDO was maximized (k~25% higher than that on Pt/Al2O3), with that material also exhibiting similar deoxygenation (85%–90% at total GUA conversion) to the latter Pt over pristine alumina. Conversely, both parameters significantly diminished over the catalyst of the highest La content. Materials at low rare‐earth concentrations deserve further studies focused on catalyst stability under HDO conditions.

Origin of strong metal-support interactions between Pt and anatase TiO2 facets for hydrodeoxygenation of m-cresol on Pt/TiO2 catalysts

Metal/reducible metal oxide catalysts are widely used in hydrodeoxygenation (HDO) reactions for upgrading bio-oil to produce chemicals and fuel components. Under such strong reducing condition, the strong metal-support interaction (SMSI) should take place, however, few work has been devoted to understand the effect of facet of metal oxide on the SMSI and its consequence on HDO performance. Herein, Pt supported on anatase TiO2 with varying dominative exposed facets of (101), (100) and (001) were prepared and tested in HDO of m-cresol at 350 °C and atmosphere H2 pressure. The degree of SMSI of Pt/TiO2 is strongly dependent on the facet of TiO2 when reduced at 350 °C, and the degree of encapsulation decreases following the order of Pt/TiO2-100 > Pt/TiO2-001 > Pt/TiO2-101. The encapsulation correlates well with the reduction degree of TiO2 and the location of oxygen vacancy, which are resulted from varied oxygen vacancy formation and anisotropic diffusion rates in different facets. The intermediate SMSI is achieved on TiO2-001, which creates the maximal density of Pt-Ov-Ti3+ sites at the interfacial perimeter of TiOx/Pt for deoxygenation of m-cresol, resulting in the highest reaction rate and turnover frequency (TOF) while the lowest activation energy (Ea). In contrast, the maximum SMSI on TiO2-100 leads to the lowest deoxygenation rate while the highest Ea. This work provides insight into facet dependent SMSI of Pt/TiO2 and indicates the HDO activity can be finely tailored by tuning the facet of TiO2.

Transition metal-containing MgFe ex-LDH mixed oxides, effective catalysts in the hydrodeoxygenation of benzyl alcohol

Several M-MgFe-LDH precursors were prepared via co-precipitation and then calcined at 500 °C to yield the corresponding M-MgFeO mixed oxide catalysts, which were tested in the hydrodeoxygenation (HDO) of benzyl alcohol. The prepared LDH contained Mg and Fe in a mol ratio of 3:1 and 10 at% M with respect to cations, where M = Ni, Co, Ag and Cu. The Cu-MgFeO mixed oxide gave the best results, therefore we proceeded with the preparation of a Cu(x)-MgFeO series, where x = 2.5–20 at% Cu. The prepared solids were characterized by powder X-ray diffraction, nitrogen adsorption-desorption, temperature-programmed reduction with H2, temperature-programmed desorption of CO2 and energy dispersive X-ray spectroscopy. We studied the influence of the nature of the transition metal M on the activity and selectivity of the catalysts and, for the Cu-containing samples, the influence of Cu loading, reaction time and reaction temperature on their performance in the HDO reaction of benzyl alcohol. With 93.8% conversion and 93.8% selectivity towards toluene at 230 °C, 3 h reaction time and under a hydrogen pressure of 5 atm, the Cu(10)-MgFeO catalyst proved to have the best performance in the studied reaction. Therefore, its stability and reusability were checked. We also proposed a sequence of reactions for the entire HDO process, based on a reverse Mars-van Krevelen mechanism driven by oxygen vacancies formed on the catalyst surface.

Selective hydrodeoxygenation of guaiacol to cyclohexanol over NixCoyAlz catalysts under mild conditions

Hydrodeoxygenation is one of the key steps to upgrade of biomass derived bio-oil into valuable biofuels and chemicals. Developing of highly reactive and cost-effective catalysts for bio-oil hydrodeoxygenation is highly desired. Layered NixCoyAlz catalyst was prepared using layered double hydroxide (LDH) as the precursors. The optimized Ni1Co3Al2-600 catalyst exhibits excellent catalytic performance for guaiacol hydrodeoxygenation. Guaiacol could completely converted with 90.0% of cyclohexanol selectivity under relatively mild reaction conditions. The XRD and HRTEM characterizations of the as prepared catalysts confirmed the formation of Ni-Co alloy and the XPS analysis revealed the strong interaction between Al species with both Ni and Co in catalyst Ni1Co3Al2-600, which should contribute to its high catalytic activity for guaiacol hydrodeoxygenation. Catalyst Ni1Co3Al2-600 also demonstrated excellent versatility for the hydrodeoxygenation reactions of guaiacyl and syringyl compounds as well as high stability. The results from this work could provide a new approach for the constructing of effective catalysts from non-noble metal LDHs.

Direct deoxygenation reaction of oxygenated model compounds by biomass pyrolysis on the Ni5P4(001) surface: a computational study

The activity of nickel phosphides in hydrodeoxygenation reactions along with the preservation of the products aromaticity indicate that these catalysts possess exceptional surface affinity for the functional groups of the probe molecules of interest.

On the reduction of CO2 footprint via selective hydrodeoxygenation by ZnO–Ti3C2Tx catalyst under solvent-free conditions

A series of ZnO–Ti3C2Tx catalysts was studied first time for the catalytic hydrodeoxygenation (HDO) reaction. The catalyst exhibited complete conversion and >90% selectivity for octadecane (C-18) with 5-cycle recyclability.

Formic acid-promoted hydrodeoxygenation reactions over carbon encapsulated Co nanoparticles

It is challenging to use formic acid as a hydrogen donor for reduction reactions over heterogeneous non-noble metal catalysts.

An alternative reaction pathway triggered by oxygen vacancies for boosting selective hydrodeoxygenation reactions

The Co/CoOx catalyst with rich oxygen vacancies was found to be robust for mild and selective hydrodeoxygenation reactions. The oxygen vacancies promote the activation of substrates, and enable the reactions in direct hydrogenolysis pathway.

Compositional dependence of hydrodeoxygenation pathway selectivity for Ni2−xRhxP nanoparticle catalysts

Controlled synthesis of Ni2−xRhxP nanoparticle catalysts enables an understanding of composition-dependent selectivity for the hydrodeoxygenation reaction of phenolic molecules.

Bifunctional CaCO3/HY Catalyst in the Simultaneous Cracking-Deoxygenation of Palm Oil to Diesel-Range Hydrocarbons

Palm oil is a promising raw material for biofuel production using the simultaneous catalytic mechanism of the bifunctional cracking-deoxygenation reactions. Through the cracking-deoxygenation process, the chains of palmitic acid and oleic acid in the palm oil were converted to diesel-range hydrocarbons. The combination effects of CaCO3 and HY zeolite enhanced the bifunctional catalytic cracking-deoxygenation of palm oil into biofuel, because of the increasing acid and basic sites in the catalysts due to the synergistic roles of CaCO3 and HY. The introduction of CaCO3 on HY zeolite generated both a strong acid and strong basic sites simultaneously on the designed catalyst, which supports the bifunctional mechanisms of hybrid cracking-deoxygenation, respectively. The CaCO3 impregnated on the HY catalyst has a synergistic and bifunctional effect on the catalyst supporting cracking-deoxygenation reaction mechanisms as mentioned previously. The deoxygenation reaction required the bifunctional strong acid and strong basic sites on the CaCO3/HY catalyst through decarboxylation, decarbonylation, and hydrodeoxygenation reaction mechanisms. Meanwhile, the cracking reaction pathway was supported by the strong acid sites generated on the CaCO3/HY catalyst. In other words, the high acidity strength promotes diesel selectivity, whereas the high strength of basicity leads to the deoxygenation reaction.

Stabilizing the interfacial Cu0-Cu+ dual sites toward furfural hydrodeoxygenation to 2-methylfuran via fabricating nest-like copper phyllosilicate precursor

Furfural hydrodeoxygenation (HDO) to 2-methylfuran (2-MF) is one of the most momentous routes in upgrading of biomass platform molecules, where the most universally employed active metal—Cu often suffers from thermal sintering and poor stability in spite of its brilliant effect on the activation of carbonyl. In this study, we designed a highly active and stable Cu/SiO2 nanocatalyst by fabricating nest-like nanotubes (CuSi-N) through a two-step method: preparation of amorphous copper phyllosilicate through ammonia evaporation, followed by a further hydrothermal crystallization with the assistance of P123. Notably, the CuSi-N catalyst gives a 2-MF space–time yield of 46.6 mmol·gcat−1·h−1, which is much larger than CuSi-A prepared by the conventional ammonia-evaporation method. A combination study (Raman spectra, TEM, H2-TPR, XPS, CO-DRIFTS and NH3-TPD) verifies that the nest-like precursor enhances the CuOx-SiO2 interaction, which results in a promoted Cu+ abundance as well as thermal stability of the active sites. In situ FTIR spectra of adsorbed molecules, coupled with density functional theory calculations, prove that Cu+ sites are responsible for the adsorption and activation of both furfural (FAL) and intermediate furfuryl alcohol (FOL) while Cu0 sites account for H2 dissociation. This work discloses the significance of the synergy effect of Cu0-Cu+ dual sites of Cu/SiO2 catalysts which could be employed for the other HDO reactions in the upgrading process of biomass.

Quantitative synergy between metal and acid centers over the Ni/Beta bifunctional catalyst for methyl laurate hydrodeoxygenation to bio-jet fuel

The synergistic effect of metal and acid centers influences performance of bifunctional hydrodeoxygenation (HDO) catalyst significantly. However, seldom work concerning this point has been performed quantitatively. Herein, the Ni/Beta catalysts were prepared for HDO of methyl laurate to bio-jet fuels. The ratios of metal to acid centers (nNi/nA) were used to quantitatively express the synergistic effect and correlated to the HDO performance. The transformation of methyl laurate mainly stagnates at fatty acid over the mono-functional catalyst (nNi/nA = 0), while the acid centers are indispensable for the efficient transformation of methyl laurate at relatively mild reaction conditions. The TOF and selectivity to C11 and C12 alkanes increase and then keep constant with the increasing nNi/nA. The turning point at the nNi/nA of 0.67 implies that one nickel center over the Ni/Beta catalyst can balance ca. 1.5 acid centers in the HDO of methyl laurate. Besides, the higher nNi/nA favors the HDO reaction pathway compared with the decarbonylation or decarboxylation ones. It increases the selectivity to C12 alkanes and improves efficiency of atomic utilization during the hydrodeoxygenation of methyl laurate. This work provides a deeper insight into the quantitative synergy of active sites over the bifunctional HDO catalyst for production of bio-fuels.

Crystal Phase Sensitivity of 5-Hydroxymethylfurfural Hydrodeoxygenation over a Pt1Co Single-Atom Alloy Catalyst

In reactions of hydrodeoxygenation (HDO) of biomass-derived chemicals, one promising method for improving the yield of desirable products is to control the crystal phase of the catalyst and thus the adsorption configuration of intermediates. In this work, we have investigated the catalytic activity and selectivity of Pt1Co single-atom alloy (SAA) catalysts with fcc (face-centered cubic) and hcp (hexagonal close-packed) cobalt crystal phases toward 5-hydroxymethylfurfural (5-HMF) HDO reaction by density functional theory (DFT) calculation. Potential energy profiles of 5-HMF HDO reactions on the Pt1Co-fcc and Pt1Co-hcp surfaces show that the Pt1Co-hcp surface has a lower hydrogenation energy barrier (0.96 and 0.83 eV) and C–O bond cleavage energy barrier (0.58 and 0.44 eV) than the Pt1Co-fcc surface, indicating the Pt1Co-hcp surface exhibits higher catalytic activity. Ring-opening energy and ring hydrogenation calculations distinguish product selectivity: the optimal product on the Pt1Co-hcp surface is 2,5-dimethyltetrahydrofuran (DHMF), but 2-hexanol on the Pt1Co-fcc surface, which is caused by atomic density difference from the crystalline phase. This work provides a new theoretical support to improve reaction activity and product selectivity by controlling the crystal phase of biomass HDO catalysts.

Hierarchical ZSM-5 supported Ni catalysts for hydrodeoxygenation of phenolics: Effect of reactant volumes and substituents

Hydrodeoxygenation (HDO) is considered as one of the most efficient technologies for phenolics upgrading. To explore the effect of volumes and substituents on the phenolics, hierarchical nanosponge ZSM-5 supporting Ni catalyst (Ni/NPZ) is prepared and used in HDO reactions. The Ni/NPZ catalyst with hierarchical pores and highly dispersed metal species, shows enhanced adsorption of phenolics and adsorption/transfer of hydrogen, thus giving significantly higher catalytic activity than the reference micropores catalyst (Ni/CZ). Moreover, phenolics with large volumes such as 4-propylphenol give decreased conversion rates than phenol and anisole, through sequenced hydrogenation and deoxygenation procedures. Owing to the steric resistance, the deoxygenation occurs firstly on guaiacol and 2,6-dimethoxyphenol, following by hydrogenation of aromatic rings. Interestingly, the scission of C-C bonds occurs at 2,6-ditertbutylphenol by electron transfer between tertbutyl and aromatic ring, which improves their initial conversion.

Comparison of Co-Mo-S and remote control model for designing efficient Co-doped MoS2 hydrodeoxygenation catalysts

Co-promoted MoS2 catalysts as good candidates can effectively remove the oxygen in bio-oil through the hydrodeoxygenation (HDO) of phenolics. However, it is of great importance to maximize the synergistic effect between Co and MoS2 which is conductive to the design of highly efficient Co-doped MoS2 HDO catalysts. Herein, two model catalysts with Co-Mo-S and CoS2/MoS2 (remote control model) as the active phases were successfully constructed and evaluated in the HDO of p-cresol. It was found that Co-Mo-S catalyst showed a significantly higher intrinsic HDO activity than CoS2/MoS2 catalyst, and the synergy factor between Co dopant and MoS2 of Co-Mo-S was 3.1 times that of CoS2/MoS2. The greatly enhanced HDO performance of Co-Mo-S catalyst is attributed to remarkably weakened strength of MoS bond, which can facilitate the sulfur vacancies (Vs) formation on the sulfur edges and promote the reaction rate of direct deoxygenation (DDO) pathway. This work revealed that Co-Mo-S model could better promote the CoMo synergy than the remote control model so as to design more efficient MoS2-based catalysts for HDO reactions.

Catalytic production of long-chain hydrocarbons suitable for aviation turbine fuel from biomass-derived levulinic acid and furfural

Catalytic conversion of biomass to liquid fuel is one of critical part to ease dependence on fossil fuel. Herein, a route of transformation of biomass-derived furfural and levulinic acid into long-chain hydrocarbon fuels was developed. A C20 oxygenate with 95 % mol yield was firstly synthesized through condensation-polymerization reactions catalyzed by NaOH. Various techniques were employed to verify the chemical structure of the C20 oxygenate. The condensation mixture was then directly subjected to hydrodeoxygenation reaction to prepare long-chain hydrocarbons with a catalytic system of Pd/C and H3PO4 in aqueous phase. A 57.1 % weight yield of liquid fuel was obtained with main products of C12, C14, and C18 hydrocarbons. The mass percent of carbon and hydrogen in fuel was significant improved to 95.91 %, as well as the high heat value was increased to 47.04 MJ/kg.

Bifunctional Pt/Hβ catalyzed alkylation and hydrodeoxygenation of phenol and cyclohexanol in one-pot to synthesize high-density fuels

Synthesis of fuels from lignin bio-oil feedstock significantly alleviates energy crises and environmental pollution. Phenol is the simplest model compound for lignin bio-oil feedstocks, and the synthesis of fuel precursors from phenol through alkylation has received increasing attention. Here we report a one-pot strategy for preparing polycyclic alkane high-density fuels from phenol and cyclohexanol over bifunctional Pt/Hβ catalyst by combining alkylation with following hydrodeoxygenation (HDO). The activity of different zeolites for catalyzing the alkylation of phenol and cyclohexanol was explored. It was found that the larger pore size of alkali treated Hβ would not limit the production of polycyclic compounds, and good acid content in a particular mesoporous specific surface area can speed up the reaction rate. The one-pot reaction conditions were then optimized. When the alkali treatment concentration is 0.2 mol/L, the metal loading is 0.2 wt%, and the molar ratio of phenol and cyclohexanol is 1:1, the highest conversion of phenol can reach more than 83 %. The selectivity of alkylphenol can reach more than 97 %, and the yield of bicyclic and tricyclic rings in the final product after HDO can reach 83.42 %. The bifunctional catalyst can also realize the coupling of other acid-catalyzed carbon growth reactions and metal-catalyzed HDO reactions, which allows the direct synthesis of fuel from lignin oil or other biomass compounds.

PH-Induced selective electrocatalytic hydrogenation of furfural on Cu electrodes

AbstractThe efficient and selective electrocatalytic hydrogenation (ECH) of furfural is considered a green strategy for achieving biomass-derived high-value chemicals. Regulating an aqueous electrolytic environment, a green hydrogen energy source of water, is significant for improving the selectivity of products and reducing energy consumption. In this study, we systematically investigated the mechanism of pH dependence of product selectivity in the ECH of furfural on Cu electrodes. Under acidic conditions, the oxygen atom dissociated directly from hydrogenated furfural-derived alkoxyl intermediates, followed by stepwise hydrogenation until H2O formation via a thermodynamically favorable proton-coupled electron transfer process, thereby inducing a high proportion of the hydrogenolysis product (2-methylfuran). However, under partial alkaline conditions, furfural could be directly hydrogenated to furfuryl alcohol (selectivity ~98%) due to the high-energy barrier of the deoxidation process via a surface hydride (Had) transfer. Our results highlight the vital role of the electrolytic environment in furfural selective conversion and broaden our fundamental understanding of hydrodeoxygenation reactions in ECH.

The formation and transformation of hexadecanal influence on reaction pathway and activity in the palmitic acid hydrodeoxygenation over mesoporous ETS-10 supported Ni catalyst

Mesoporous ETS-10 zeolites supported Ni catalysts (Ni@NaMETS-10 and Ni@HMETS-10) were applied in the hydrodeoxygenation (HDO) of palmitic acid to investigate the formation and transformation pathways of hexadecanal (HAL) and reaction activity. Experiment results verified that HAL was an initial product in the HDO reaction under 0.1 MPa H2 pressure, and Ni@HMETS-10 exhibits higher activities (robs,1=2.55×10−4 mol kg−1 s−1, robs,2= 6.85×10−3 mol kg−1 s−1) than Ni@NaMETS-10 (robs,1=1.59×10−4 mol kg−1 s−1, robs,2=5.74×10−3 mol kg−1 s−1) due to the presence of Brönsted acid sites and highly dispersed Ni particles. At high H2 pressure (4.0 MPa), the acid-base properties of the support affected the transformation of HAL and the reaction pathways. The abundant Lewis basic sites on Ni@NaMETS-10 can promote the decarbonylation of the HAL and the HDCO route are dominate. Brönsted acid and Ni sites on Ni@HMETS-10 synergistically catalyzed the deoxygenation of palmitic acid via two parallel HDH2O and HDCO routes with a higher reaction rate (1.42×10−3 mol kg−1 s−1) than Ni@NaMETS-10 (1.31×10−3 mol kg−1 s−1). The reaction rate constants of each step in reaction routes on both catalysts were supplemented.