Hydrodeoxygenation Activity Research Articles

Liquid Phase Conversion of Phenols into Aromatics over Magnetic Pt/NiO–Al2O3@Fe3O4 Catalysts via a Coupling Process of Hydrodeoxygenation and Dehydrogenation

Magnetic colloidal sol was first prepared and added in the mixed solution of Ni(NO3)2 and Al(NO3)3. After the constant-pH coprecipitation and calcination, magnetic NiO–Al2O3@Fe3O4 mixed oxides were formed and used as supports for Pt-based catalysts. The activities of these magnetic Pt/NiO–Al2O3@Fe3O4 catalysts were tested in the hydrodeoxygenation (HDO) of phenols such as 4-ethylphenol, 4-methylphenol, and guaiacol. These exhibited high HDO activity, and aromatic hydrocarbons were produced through a coupling process of hydrodeoxygenation and dehydrogenation. The addition of Fe enhanced both the conversion and aromatic hydrocarbons selectivity, which was attributed to the electron transfer between metallic Pt and Fe. For example, after the liquid phase HDO of 4-ethylphenol at 300 °C and 2.0 MPa for 1.5 h, 97.9% conversion and 18.3% toluene selectivity were obtained. When the reaction time was prolonged to 8 h, ethylbenzene selectivity increased to 88.0%. Moreover, these Pt/NiO–Al2O3@Fe3O4 catalysts were easily recycled from the liquid reaction mixture by employing an external magnet, but the dehydrogenation stability needs to be further improved.

Phosphonic acid promotion of supported Pd catalysts for low temperature vanillin hydrodeoxygenation in ethanol

Bifunctional catalysts with activity for both hydrogenation and dehydration have been frequently investigated for hydrodeoxygenation (HDO). Here, we report the application of organophosphonic acids (PAs) to Pd/Al2O3 catalysts for low-temperature vanillin HDO. Reaction studies indicated that PA-modification significantly improved the liquid-phase HDO activity; the yield to the desirable product, p-creosol (CR), increased from 2.5% to 87% at 50 °C. This improvement was attributed to the creation of metal/acid bifunctional sites upon PA modification. In addition, HDO activity positively correlated with the Brønsted acidity of the PA modifier, which could be tuned by adjusting the PA tail functionality.

Pd Nanoparticles Supported on Cellulose as a Catalyst for Vanillin Conversion in Aqueous Media

Palladium nanoparticles were first anchored on modified biopolymer as an efficient catalyst for a biofuel upgrade. Fluorinated compounds was grafted onto cellulose to obtain amphiphilic supports for on water reactions. Pd catalyst was prepared by straightforward deposition of metal nanoparticles on modified cellulose. The catalyst exhibited excellent catalytic activity and selectivity in hydrodeoxygenation of vanillin (a typical model compound of lignin) to 2-methoxy-4-methylphenol under atmospheric hydrogen pressure in neat water without any other additives under mild conditions.

Hydrodeoxygenation of phenolic compounds to cycloalkanes over supported nickel phosphides

SiO2, HZSM-5 and Al2O3 were used to support nickel phosphides to prepare hydrodeoxygenation (HDO) catalysts. The nickel loading was kept at 20 wt% while the Ni/P molar ratio was varied among 3, 2, and 1 in the preparation by incipient wetness impregnation. XRD characterization revealed that Ni3P, Ni12P5, and Ni2P as the major crystal phases were obtained at Ni/P ratio of 3, 2, and 1, respectively, on SiO2 and HZSM-5. When Al2O3 was used as the support, nickel metal rather than nickel phosphides was generated. Among SiO2-supported nickel phosphides, Ni3P exhibited highest hydrogenation activity and catalytic performance in phenol HDO. Ni3P/HZSM-5 showed the high catalytic performance in HDO of phenol as well as catechol and o-cresol, with Ni3P as the hydrogenation site and the acid sites in HZSM-5 zeolite as the dehydration site. The strong acidity in HZSM-5 also facilitated the isomerization of cycloalkanes at elevated temperatures.

A comparison of MoS2 catalysts hydrothermally synthesized from different sulfur precursors in their morphology and hydrodeoxygenation activity

Three MoS2 catalysts were synthesized by a hydrothermal method using different sulfur precursors such as thiourea, L-cystine and sulfur powder; their differences in the structure, morphology, and catalytic activity in the hydrodeoxygenation (HDO) of p-cresol were comparatively investigated. The results illustrated that the sulfur source has a significant influence on the morphology and surface area of the as-synthesized MoS2 catalysts. All the hydrothermally synthesized MoS2 catalysts show much higher activity in HDO than the commercial MoS2 sample. Among three MoS2 catalysts, the one prepared from thiourea, with a high surface area and flower-like morphology, exhibits the highest activity in HDO; over it, a deoxygenation degree of 99.3% is achieved at 300°C.

Controlling the growth of activated carbon supported nickel phosphide catalysts via adjustment of surface group distribution for hydrodeoxygenation of palmitic acid

Nickel phosphides were known to be promising substitute for noble metal used in various catalysts. The traditional method of controlling the growth of nickel phosphide species, including Ni2P, Ni3P, and Ni12P5, was either modulating Ni/P molar ratio or changing support. Here, we report a new method to control the growth of nickel phosphide species by tuning the types of surface oxygenated group types on activated carbon. The pretreatment of activated carbon with HNO3 remarkably increased the content of OCO groups. In the preparation process of activated carbon supported nickel phosphide catalyst, the OCO groups might interact with P to form POCO groups. The formed POCO inhibited the reduction of P species at low temperature, and thus inhibited the formation of the nickel phosphides; whereas at 873 K reduction, the formation of pure Ni2P on activated carbon was enhanced. However, the content of -OH groups content increased on activated carbon treated by NH3∙H2O, which might be favorable for the simultaneous formation of Ni2P and Ni12P5 with 1/1 ratio, and the thus formed catalyst displayed excellent catalytic hydrodeoxygenation activity for palmitic acid. Our results demonstrated how simple base and acid pretreatment could be used to tune the interfacial group distribution, hereby providing a strategy to rationally design transition metal phosphide supported catalysts.

Acidity, oxophilicity and hydrogen sticking probability of supported metal catalysts for hydrodeoxygenation process

Hydrodeoxygenation is an oxygen removal process that occurs in the presence of hydrogen and catalysts. This study has shown the importance of acidity, oxophilicity and hydrogen sticking probability of supported metal catalysts in having high hydrodeoxygenation activity and selectivity. These properties are required to ensure the catalyst has high affinity for C-O or C=O bonds and the capability for the adsorption and activation of H2 and O-containing compounds. A theoretical framework of temperature programmed desorption technique was also discussed for the quantitative understanding of these properties. By using NH3-TPD, the nature and abundance of acid sites of catalyst can be determined. By using H2-TPD, the nature and abundance of metallic sites can also be determined. The desorption activation energy could also be determined based on the Redhead analysis of TPD spectra with different heating rates.

Catalytic synthesis of renewable hydrocarbons via hydrodeoxygenation of angelica lactone di/trimers

Angelica lactone and its di/trimers is becoming an important renewable platform molecule but the development of simple hydrodeoxygenation (HDO) catalysts will play a major role in its utilization as feedstock for fuel production. In this study, Ni supported on ZSM-5 having Si/Al ratio of 40 and 300 or Ni supported on heteropoly acid/activated carbon (Ni/Ac-HPA) were synthesized and their HDO activities on angelica lactone di/trimers resulted in the production of gasoline ranged (C6–C15) hydrocarbon fuels. The HDO activities of the catalysts were dependent on the successful incorporation of Ni metals into the pores of the supports and the Ni metals were highly dispersed with average particle sizes of 20 nm. Considering recent advances in catalytic conversion of biomass to liquid fuels, the method provided in this study is simple and could be replicated in an industrial scale.

The effect of rosin acid on hydrodeoxygenation of fatty acid

In this study, inhibition of tall oil fatty acid hydrodeoxygenation (HDO) activity due to addition of rosin acid over sulfided NiMo/Al2O3 was investigated. Oleic acid and abietic acid were used as model compounds for fatty acid and rosin acid respectively in tall oil. After completion of each HDO experiment, the NiMo catalysts were recovered and used again under the same conditions. The results showed that the oleic acid HDO activity of sulfided catalysts was inhibited by addition of abietic acid due to competitive adsorption and increased coke deposition. The rate of carbon deposition on the catalysts increased when abietic acid was added to oleic acid feed. Moreover, the coke was in a more advanced form with higher stability for the catalysts exposed to both oleic acid and abietic acid. Furthermore, a clear correlation between the rate of coke formation and concentration of abietic acid was observed.

A Comparative Study of Hydrodeoxygenation of Furfural Over Fe/Pt(111) and Fe/Mo2C Surfaces

It is desirable to convert biomass-derived furfural to 2-methylfuran through the hydrodeoxygenation (HDO) reaction using an inexpensive catalyst with high stability. In this work, Mo2C was used as an alternative substrate to replace precious Pt to support monolayer Fe for the HDO reaction of furfural. The HDO activity and stability of Fe/Pt(111) and Fe/Mo2C/Mo(110) surfaces were compared. Density functional theory calculations and vibrational spectroscopy results indicated that both surfaces bonded to furfural with similar adsorption geometries and should be active toward the furfural HDO reaction. Temperature programmed desorption experiments confirmed a similar HDO activity between the two surfaces, with Fe/Mo2C/Mo(110) being more thermally stable than Fe/Pt(111). The combined theoretical and experimental results demonstrated that Fe/Mo2C should be a promising non-precious metal catalyst for the HDO reaction of furfural to produce 2-methylfuran.

Eco-friendly controllable synthesis of highly dispersed ZIF-8 embedded in porous Al2O3 and its hydrogenation properties after encapsulating Pt nanoparticles

In this paper, a new strategy was proposed to synthesize a novel composite of highly dispersed ZIF-8 embedded in porous Al2O3 by a solvent-free method. This is a very simple, efficient, and eco-friendly method, in which ZnO/Al2O3 was used as a precursor, and dimethyl imidazole was used as an organic ligand. Meso- and microporous composite of ZIF-8@Al2O3 was synthesized arising from the crystal growth of ZIF-8 derived from ZnO nanoparticles. Characterization results reveal that the distribution of micropores and mesopores can be controlled by simply adjusting the amount of zinc salt supported on Al2O3. The value of this composite is that it can simultaneously exert the advantages of ZIF-8 and Al2O3 support, which can significantly decrease the particle size of ZIF-8 and improve its utilization efficiency. The micropores of ZIF-8 can increase the dispersion of Pt nanoparticles, at the same time, the functional groups on the surface of Al2O3 can improve the selectivity of the product. Furthermore, this kind of composite material can be extended by replacing the support. Finally, the results of the activity tests showed that the obtained Pt/ZIF-8@Al2O3 catalyst exhibits high activity and selectivity in hydrodearomatization (HDA) and hydrodeoxygenation (HDO) reactions.

Facile synthesis of Mo/Al2O3–TiO2 catalysts using spray pyrolysis and their catalytic activity for hydrodeoxygenation

In this study, spherical mixed oxides of Al2O3 and TiO2 supported molybdenum (Mo) catalysts, Mo/Al2O3−TiO2, were successfully prepared using a novel approach combining sol-gel and spray pyrolysis (SP) methods. First, both boehmite sol and titania sol were prepared by a sol-gel process, and then molybdate salt was dispersed in the sol mixture with the assistance of citric acid, followed by spray pyrolysis of the mixed precursor solution. Structural analyses of prepared catalysts showed that the dispersion of active sites was affected by the TiO2 concentration in the Al2O3−TiO2 mixed oxide support. The catalytic activities of reduced catalysts were investigated for hydrodeoxygenation (HDO) of palmitic acid, which is the main component of microalgae–derived biocrude. The results show that the Mo/Al2O3–TiO2 catalysts exhibited excellent catalytic performance for the HDO of palmitic acid.

Ni3P as a high-performance catalytic phase for the hydrodeoxygenation of phenolic compounds

Ni3P shows extremely high activity and stability in phenol hydrodeoxygenation both in the aqueous phase and in the organic phase.

Effects of graphitization of carbon nanospheres on hydrodeoxygenation activity of molybdenum carbide

The hydrodeoxygenation catalytic activity and stability of carbon supported molybdenum carbide catalysts could be improved by graphitizing their carbon supports.

Hydrodeoxygenation of p-cresol as a model compound for bio-oil on MoS2: Effects of water and benzothiophene on the activity and structure of catalyst

MoS2 was prepared by a hydrothermal method and then applied into the hydrodeoxygenation (HDO) of p-cresol as a model compound for bio-oil to study the effects of water and benzothiophene on the conversion, product distribution and stability in detail. The presence of water enhanced the HDO activity and decreased the hydrogen consumption: the deoxygenation degree and toluene selectivity reached to 97.0% and 88.0%, respectively. When water was replaced by benzothiophene, p-cresol conversion increased to 92.3% with toluene selectivity of 72.4%. With water and benzothiophene simultaneously introduced, at 275 °C and 4.0 MPa, the conversion and toluene selectivity were 86.0% and 79.1%, respectively. The reaction temperature and hydrogen pressure were also significant factors. The conversion was raised to 97.4% with toluene selectivity of 80.1% when the reaction temperature increased to 300 °C, but decreased to 71.7% with toluene selectivity of 77.2% when hydrogen pressure increased to 5.0 MPa. The characterization results of the spent catalysts indicated that some defects in the (0 0 2) plane of MoS2 caused by the loss of sulfur were observed after the HDO reaction, which resulted in its deactivation. This deactivation was accelerated by adding water but inhibited by adding benzothiophene.

Study of catalytic hydrodeoxygenation performance for the Ni/KIT-6 catalysts

Ni/KIT-6 catalysts loaded with different amounts of metallic Ni were prepared by impregnation method. The prepared catalysts and their precursors were investigated through wide- and low-angle XRD, TEM, BET, H2-TPR, and H2-TPD analyzes. The catalytic hydrodeoxygenation performance of the catalysts was evaluated using ethyl acetate as a model bio oil compound. Results indicate that the catalytic hydrodeoxygenation performance of the prepared catalysts was directly related to hydrogen storage properties, hydrogen desorption properties, dispersion of the active component Ni, and so on. The ethyl acetate conversion and ethane selectivity of 25 wt% Ni/KIT-6 catalyst were 100 and 96.8%, respectively, at 300 °C, which shows the best performance. The hydrodeoxygenation activity of ethyl acetate was higher than that of methyl acetate and isopropyl acetate because of the effect of molecular polarity and size. And, this reaction is a structure sensitive reaction.

Hydrodeoxygenation activity of W modified Ni/H-ZSM-5 catalyst for single step conversion of levulinic acid to pentanoic acid: An insight on the reaction mechanism and structure activity relationship

Direct conversion of levulinic acid (LA) to pentanoic acid (PA) was achieved over the W modified Ni supported on SiO2, Al2O3 and H-ZSM-5 catalysts at 270°C and ambient H2 pressure in a continuous flow fixed-bed reactor. The interaction between Ni and W was the key which is rationalized by XRD, XPS, TGA-TPD of NH3, DRIFTS, TEM, CO-pulse chemisorption and H2-TPR analyses. PA rate of ∼1.24μmols−1gcat−1 (with highest LA conversion ∼40% and selectivity ∼65% after 6h of continuous operation) achieved over W modified Ni/H-ZSM-5 catalyst compared to others. The better PA rate on Ni-W/H-ZSM-5 catalyst was manifested by the presence of not only strong acid sites and also due to a higher number surface ionic Ni species which were responsible for the ring opening of γ-valerolactone (GVL) and the β-proton abstraction that occurred on basic sites. On the contrary, Ni-W/SiO2, Ni-W/Al2O3 and Ni/H-ZSM-5 were found to be less selective towards PA and more selective towards GVL, exemplifying the role of support and W for the PA selectivity. The surface active sites for the PA formation are illustrated by using probes such as pyridine (strong base) and/or acetone (mild base) and formic acid adsorbed DRIFT spectroscopy. Based on the product distribution, a plausible surface mechanism was also elucidated and discussed.

Deoxygenation of stearic acid with a novel Ni(CO)‐MoS2/Fe3S4 catalyst

AbstractMagnetically recyclable Ni(Co)‐promoted MoS2 catalysts with greigite (G) core were synthesized and their activity and selectivity in hydrodeoxygenation of stearic acid were investigated. The activity of the catalysts tested at 320 °C and H2 initial pressure of 3.5 MPa could be ranked as NiMo/G > CoMo/G > Mo/G. Two main products were detected, C18 (through HDO pathway) and C17 hydrocarbons (through DCO pathway). HDO was the dominant pathway for all of the catalysts. As for the C18/C17 ratio, the catalysts were found to be in the order: Mo/G > CoMo/G ≈ NiMo/G. The Paraffin/Olefin ratio was over 1 for all of the catalysts with NiMo/G showing the highest ratio. Stearic acid was found to have an inhibiting effect on the adsorption of intermediates over the active sites. Moreover, the concentrations of intermediates decreased at high conversions of stearic acid. The formation of the intermediate aldehyde is through C–O hydrogenolysis of the fatty acid following the protonation, dehydrogenation, and hydride addition steps. The same steps were suggested to be involved in the transformation of the aldehyde to the alcohol. Formation of Cn‐1 hydrocarbons was found to be via decarbonylation route. The enhancement of the DCO pathway over the promoted catalysts was related to the electron transfer from the promoting atom to an adjacent sulphur atom and reduction in sulphur‐metal bond strength.

High-Performance Magnetic Activated Carbon from Solid Waste from Lignin Conversion Processes. 2. Their Use as NiMo Catalyst Supports for Lignin Conversion

Lignin conversion processes produce carbon-rich residues [Oregui-Bengoechea et al. J. Anal. Appl. Pyrolysis 2015, 113, 713−722; Zakzeski et al. Chem. Rev. 2010, 110, 3552–3599] that can be converted into valuable materials such as magnetic activated carbons (MACs). Such lignin-derived MACs can be further used as functional substrates for hydrotreating NiMo catalysts. In this work, we studied the activity of different NiMo-MACs for the catalytic conversion of lignin in a formic acid/ethanol media (lignin-to-liquid, LtL, process). Two KOH-activated LtL hydrochars from eucalyptus (MACE) and Norwegian spruce (MACS) lignins were used as catalyst supports. In addition, the activity of the resulting NiMo-MACs, namely, C-MACE and C-MACS, was compared with a NiMo catalyst supported on a commercial activated carbon (AC). At reaction conditions of 340 °C and 6 h, the best result was obtained for the NiMo-MACS with a yield of 72.2 wt % of oil and 21.1 wt % of organic solids. At 300 °C and 10 h, both NiMo-MAC catalysts displayed higher hydrodeoxygenation (HDO) activities than their commercial counterpart, yielding considerably higher oil yields. The higher HDO activities are tentatively assigned to the formation of NiFe species on the catalytic surfaces of the NiMo-MAC catalysts. In addition, the magnetism exhibited by the C-MACS made it easy to recover the catalyst. However, a considerable loss of activity was observed upon recycling due to a chemical modification of the catalyst surface.

Nickel impregnated mesoporous USY zeolites for hydrodeoxygenation of anisole

Ni was impregnated on various mesoporous USY zeolites, which were characterized and tested for catalytic hydrodeoxygenation (HDO) of anisole. Parent USY zeolite was modified using the mild surfactant-assisted method, and more severe desilication and desilication with pore directed agent techniques. Ni impregnation on the zeolites with higher micropore volume produced small, easily reduced, internal Ni crystallites, whereas the larger mesopores promoted the formation of bulky external Ni particles. Catalysts with larger external Ni particles were more effective for HDO of anisole. HDO with the optimal mesoporous USY supported catalyst proceeded at more than double the reaction rate, with greater yield to fully deoxygenated products, compared to HDO using Ni supported on the parent USY. Kinetic modeling using a simple lumped mechanism demonstrated that this improvement was a result of greater rates of initial Ni-catalyzed hydrogenation reactions, most likely due to greater access to the Ni surface. The most successful technique was further modified to produce a final mesoporous USY supported Ni zeolite with superior catalytic activity for anisole HDO.