Deoxygenation of Palmitic and Lauric Acids over Pt/ZIF-67 Membrane/Zeolite 5A Bead Catalysts

Metal-Acid Bifunctional Catalysts toward Tandem Reaction: One-Step Hydroalkylation of Benzene to Cyclohexylbenzene

The one-step hydroalkylation of benzene to cyclohexylbenzene (CHB) is a technically challenging and economically interesting reaction with great industrial importance, where bifunctional catalysts play a crucial role in such a tandem reaction. In this work, we report H₃PW₁₂O₄₀ (HPW) modified Ni nanoparticles (NPs) supported on mixed metal oxides (Ni/MMOs), which are featured by HPW species localized on the surface of Ni NPs (denoted as HPW-Ni/MMOs). The optimal catalyst (0.3HPW-Ni/MMOs) exhibits a satisfactory catalytic performance toward benzene hydroalkylation to CHB with a CHB yield of up to 41.2%, which is the highest standard among previously reported catalysts to date. A combination investigation based on HR-TEM, XPS, XANES, and in situ FT-IR verified the electron transfer from the W atom to the adjacent Ni atom, which facilitated the formation and desorption of cyclohexene (CHE) from Ni followed by the alkylation reaction of benzene and CHE at the interfacial Brønsted (B) acid sites of HPW, accounting for the significantly enhanced catalytic behavior. It is proposed that the HPW-Ni interface structure in xHPW-Ni/MMOs samples provides unique adsorption sites for benzene and CHE with a moderate adsorption strength, which serve as the intrinsic active center for this reaction: the Ni site promotes the hydrogenation of benzene to CHE, while the B acid site in HPW facilitates the alkylation of CHE and benzene to produce CHB. This work provides a fundamental understanding of the metal-acid synergistic catalysis toward the hydroalkylation reaction, which can be extended to the design and preparation of high-performance catalysts used in tandem reactions.

Mineral Montmorillonite Valorization by Developing Ni and Mo-Ni Catalysts for Third-Generation Green Diesel Production

Four Ni catalysts and one Mo–Ni catalyst supported on montmorillonite were synthesized, characterized by various techniques and evaluated, under solvent-free conditions, for the production of green diesel from waste cooking oil. The optimum Ni content was found to be 20 wt.%. The addition of 2 wt.% Mo to the catalyst resulted in a considerable increase in the amount of green diesel hydrocarbons. The Mo species, moreover, led to a decrease in the (C15 + C17)/(C16 + C18) ratio, which is beneficial from the viewpoint of carbon atom economy. The promoting action of Mo was mainly attributed to the synergy between the oxygen vacancies on the surface of the well-dispersed Mo(V) and Mo(VI) oxides and the neighboring Ni⁰ sites. The optimum reaction conditions, for achieving a proportion of liquid product in the green diesel hydrocarbons (C15–18) equal to 96 wt.%, were found to be 350 °C, 3 g of catalyst per 100 mL of waste cooking oil and 13 h reaction time. These conditions correspond to an LHSV of 2.5 h⁻¹, a value that is considered quite reliable from the viewpoint of industrial applications. Thus, the cheap and abundant mineral montmorillonite is proved a promising support for developing efficient Ni–Mo catalysts for green diesel production.

Recent Advances in Catalysis Based on Transition Metals Supported on Zeolites

This article reviews the current state and development of thermal catalytic processes using transition metals (TM) supported on zeolites (TM/Z), as well as the contribution of theoretical studies to understand the details of the catalytic processes. Structural features inherent to zeolites, and their corresponding properties such as ion exchange capacity, stable and very regular microporosity, the ability to create additional mesoporosity, as well as the potential chemical modification of their properties by isomorphic substitution of tetrahedral atoms in the crystal framework, make them unique catalyst carriers. New methods that modify zeolites, including sequential ion exchange, multiple isomorphic substitution, and the creation of hierarchically porous structures both during synthesis and in subsequent stages of post-synthetic processing, continue to be discovered. TM/Z catalysts can be applied to new processes such as CO₂ capture/conversion, methane activation/conversion, selective catalytic NO_x reduction (SCR-deNO_x), catalytic depolymerization, biomass conversion and H₂ production/storage.

Theoretical insight into the deoxygenation molecular mechanism of butyric acid catalyzed by a Ni12P6 cluster

For the deoxygenation of butyric acid catalyzed by Ni12P6 cluster, decreasing temperature is beneficial to butyraldehyde, n-butyl alcohol, and n-butane formation, and increasing temperature is preferable to propylene, propane, and butylene formation.

Deposition of NiO Nanoparticles on Nanosized Zeolite NaY for Production of Biofuel via Hydrogen-Free Deoxygenation

Nickel-based catalysts play an important role in the hydrogen-free deoxygenation for the production of biofuel. The yield and quality of the biofuel are critically affected by the physicochemical properties of NiO supported on nanosized zeolite Y (Y65, crystal size of 65 nm). Therefore, 10 wt% NiO supported on Y65 synthesized by using impregnation (IM) and deposition–precipitation (DP) methods were investigated. It was found that preparation methods have a significant effect on the deoxygenation of triolein. The initial rate of the DP method (14.8 g_oil·h⁻¹) was 1.5 times higher than that of the IM method (9.6 g_oil·h⁻¹). The DP-Y65 showed the best deoxygenation performance with a 80.0% conversion and a diesel selectivity of 93.7% at 380 °C within 1 h. The outstanding performance from the DP method was due to the smaller NiO particle size (3.57 ± 0.40 nm), high accessibility (H.F value of 0.084), and a higher Brönsted to Lewis acidity (B/L) ratio (0.29), which has improved the accessibility and deoxygenation ability of the catalyst. The NH₄⁺ released from the decomposition of the urea during the DP process increased the B/L ratio of zeolite NaY. As a result, the pretreatment to convert Na-zeolite to H-zeolite in a conventional zeolite synthesis can be avoided. In this regard, the DP method offers a one-pot synthesis to produce smaller NiO-supported nanosized zeolite NaY with a high B/L ratio, and it managed to produce a higher yield with selectivity towards green diesel via deoxygenation under a hydrogen-free condition.

Hydrodecarboxylation of fatty acids into liquid hydrocarbons over a commercial Ru/C catalyst under mild conditions

100% stearic acid conversion can be achieved at even 160 °C alongside a 90.1% yield of heptadecane.

Catalytic Conversion of Palm Oil to Bio-Hydrogenated Diesel over Novel N-Doped Activated Carbon Supported Pt Nanoparticles

Bio-hydrogenated diesel (BHD), derived from vegetable oil via hydrotreating technology, is a promising alternative transportation fuel to replace nonsustainable petroleum diesel. In this work, a novel Pt-based catalyst supported on N-doped activated carbon prepared from polypyrrole as the nitrogen source (Pt/N-AC) was developed and applied in the palm oil deoxygenation process to produce BHD in a fixed bed reactor system. High conversion rates of triglycerides (conversion of TG > 90%) and high deoxygenation percentage (DeCOx% = 76% and HDO% = 7%) were obtained for the palm oil deoxygenation over Pt/N-AC catalyst at optimised reaction conditions: T = 300 °C, 30 bar of H2, and LHSV = 1.5 h−1. In addition to the excellent performance, the Pt/N-AC catalyst is highly stable in the deoxygenation reaction, as confirmed by the XRD and TEM analyses of the spent sample. The incorporation of N atoms in the carbon structure alters the electronic density of the catalyst, favouring the interaction with electrophilic groups such as carbonyls, and thus boosting the DeCOx route over the HDO pathway. Overall, this work showcases a promising route to produce added value bio-fuels from bio-compounds using advanced N-doped catalysts.

Role of NiMo Alloy and Ni Species in the Performance of NiMo/Alumina Catalysts for Hydrodeoxygenation of Stearic Acid: A Kinetic Study

The hydrodeoxygenation (HDO) of vegetable oil and fatty acid is extremely important for the sustainable production of diesel-range hydrocarbons. The present work depicts the role of Ni/Mo (mole) in the performance of alumina-supported NiMo catalysts for the HDO of stearic acid. Both Ni and NiMo alloy coexist in the NiMo catalysts depending on the Ni and Mo content. With increasing Ni/Mo (mole), the NiMo alloy content in the catalyst increases with the simultaneous decrease in the Ni content. The activity of NiMo catalysts thus enhances with increasing Ni/Mo (mole). The reaction follows a decarbonylation route over Ni sites and a HDO route over NiMo alloy species. C₁₇ and C₁₈ alkanes are thus observed as the dominating hydrocarbon product over Ni and NiMo alloy-rich catalysts, respectively. The activity of the NiMo catalyst further enhances with increasing reaction temperature and metal (Ni + Mo) loading. The selectivity to alkanes was, however, not affected by metal loading. A suitable kinetic model was further established based on the reaction mechanism to relate the kinetic data.

Effect of Pt Promotion on the Ni-Catalyzed Deoxygenation of Tristearin to Fuel-Like Hydrocarbons

Pt represents an effective promoter of supported Ni catalysts in the transformation of tristearin to green diesel via decarbonylation/decarboxylation (deCOx), conversion increasing from 2% over 20% Ni/Al2O3 to 100% over 20% Ni-0.5% Pt/Al2O3 at 260 °C. Catalyst characterization reveals that the superior activity of Ni-Pt relative to Ni-only catalysts is not a result of Ni particle size effects or surface area differences, but rather stems from several other phenomena, including the improved reducibility of NiO when Pt is present. Indeed, the addition of a small amount of Pt to the supported Ni catalyst dramatically increases the amount of reduced surface metal sites, which are believed to be the active sites for deCOx reactions. Further, Pt addition curbs the adsorption of CO on the catalyst surface, which decreases catalyst poisoning by any CO evolved via decarbonylation, making additional active sites available for deoxygenation reactions and/or preventing catalyst coking. Specifically, Pt addition weakens the Ni-CO bond, lowering the binding strength of CO on surface Ni sites. Finally, analysis of the spent catalysts recovered from deCOx experiments confirms that the beneficial effect of Pt on catalyst performance can be partially explained by decreased coking and fouling.

Role of Sn promoter in Ni/Al2O3 catalyst for the deoxygenation of stearic acid and coke formation: experimental and theoretical studies

The effect of Sn promoter on a Ni/γ-Al₂O₃ catalyst towards the deoxygenation of stearic acid has been investigated.

Continuous Hydrothermal Decarboxylation of Fatty Acids and Their Derivatives into Liquid Hydrocarbons Using Mo/Al2O3 Catalyst

In this study, we report a single-step continuous production of straight-chain liquid hydrocarbons from oleic acid and other fatty acid derivatives of interest including castor oil, frying oil, and palm oil using Mo, MgO, and Ni on Al₂O₃ as catalysts in subcritical water. Straight-chain hydrocarbons were obtained via decarboxylation and hydrogenation reactions with no added hydrogen. Mo/Al₂O₃ catalyst was found to exhibit a higher degree of decarboxylation (92%) and liquid yield (71%) compared to the other two examined catalysts (MgO/Al₂O₃, Ni/Al₂O₃) at the maximized conditions of 375 °C, 4 h of space time, and a volume ratio of 5:1 of water to oleic acid. The obtained liquid product has a similar density (0.85 kg/m³ at 15.6 °C) and high heating value (44.7 MJ/kg) as commercial fuels including kerosene (0.78-0.82 kg/m³ and 46.2 MJ/kg), jet fuel (0.78-0.84 kg/m³ and 43.5 MJ/kg), and diesel fuel (0.80-0.96 kg/m³ and 44.8 MJ/kg). The reaction conditions including temperature, volume ratio of water-to-feed, and space time were maximized for the Mo/Al₂O₃ catalyst. Characterization of the spent catalysts showed that a significant amount of amorphous carbon deposited on the catalyst could be removed by simple carbon burning in air with the catalyst recycled and reused.