Characterization and catalytic properties of Ni–Mo–B amorphous catalysts for phenol hydrodeoxygenation

Transition Metal Phosphides (TMP) as a Versatile Class of Catalysts for the Hydrodeoxygenation Reaction (HDO) of Oil-Derived Compounds

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.

Improved Brønsted to Lewis (B/L) Ratio of Co- and Mo-Impregnated ZSM-5 Catalysts for Palm Oil Conversion to Hydrocarbon-Rich Biofuels

The purposes of this study are to investigate the effect of metal (Co and Mo) impregnation to ZSM-5 catalysts on the Brønsted to Lewis (B/L) ratio as the active sites of cracking reaction, and the catalysts’ performance testing for palm oil cracking to produce hydrocarbon-rich biofuels. Both metals were impregnated on the ZSM-5 catalyst using a wet-impregnation method. The catalysts were characterized using X-ray diffraction (XRD), X-ray Fluorescence (XRF), Scanning Electron Microscopy (SEM), Brunauer–Emmett–Teller (BET), and Pyridine-probed Fourier-Transform Infrared (Py-FTIR) spectroscopy methods. The catalysts were tested on the cracking process of palm oil to biofuels in a continuous fixed-bed catalytic reactor. In order to determine the composition of the organic liquid product (OLP, biofuels), the product was analyzed using a gas chromatography-mass spectrometry (GC-MS) method. The results showed that the co-impregnation of Co and Mo to ZSM-5 highly increased the Brønsted to Lewis acid site (B/L) ratio, although the total number of acid sites decreased. However, the impregnation of Co and Mo on the ZSM-5 decreased the surface area of catalysts due to pore blocking by metals, while the B/L ratio of the catalysts increased. It was obtained that by utilizing Co- and Mo-impregnated ZSM-5 catalysts, the hydrocarbons product selectivity increased from 84.32% to 95.26%; however, the yield of biofuels decreased from 67.57% to 41.35%. The increase in hydrocarbons product selectivity was caused by the improvement of the Brønsted to Lewis (B/L) acid sites ratio.

In situ hydrodeoxygenation of vanillin over Ni-Co-P/HAP with formic acid as a hydrogen source

A new noble metal-free Ni-Co-P/HAP (hydroxyapatite) amorphous alloy catalyst was synthesized by an impregnation-chemical reduction method; the structure and properties of the catalysts were characterized by XRD, SEM, BET, XPS and DSC. Based on the model of the hydrodeoxygenation (HDO) of vanillin to 2-methoxy-4-methylphenol (MMP) with formic acid as a hydrogen source, the catalytic performance of the catalyst was studied. The results found that the Ni-Co-P/HAP catalyst exhibited excellent catalytic activity for the in situ HDO reaction of vanillin compared with Ni-P and Ni-Co-P. The conversion of vanillin could be high to 97.86% with MMP selectivity of 93.97% under optimized reaction conditions. In addition, mechanism studies have shown that the side reaction of carbocation and vanillyl alcohol (HMP) condensation can be effectively reduced with increasing the hydrogenation rate, thereby the selectivity of MMP was effectively increased.

Catalytic hydrodeoxygenation of rubber seed oil over sonochemically synthesized Ni-Mo/γ-Al2O3 catalyst for green diesel production

Hydrodeoxygenation is one of the promising technologies for the transformation of triglycerides into long-chain hydrocarbon fuel commonly known as green diesel. The hydrodeoxygenation (HDO) of rubber seed oil into diesel range (C₁₅-C₁₈) hydrocarbon over non-sulphided bimetallic (Ni-Mo/γ-Al₂O₃ solid catalysts were studied. The catalysts were synthesized via wet impregnation method as well as sonochemical method. The synthesized catalysts were subjected to characterization methods including FESEM coupled with EDX, XRD, BET, TEM, XPS, NH₃-TPD, CO-chemisorption and H₂-TPR in order to investigate the effects of ultrasound irradiations on physicochemical properties of the catalyst. All the catalysts were tested for HDO reaction at 350 °C, 35 bar, H₂/oil 1000 N (cm³/cm³) and WHSV = 1 h^-1 in fixed bed tubular reactor. The catalyst prepared via sonochemical method showed comparatively higher specific surface area, particles in nano-size and uniform distribution of particle on the external surface of the support, higher crystallinity and lower reduction temperature as well as higher concentration of Mo⁴⁺ deoxygenating metal species. These physicochemical properties improved the catalytic activity compared to conventionally synthesized catalyst for HDO of rubber seed oil. The catalytic performance of sonochemically synthesized Ni-Mo/γ-Al₂O₃ catalyst (80.87%) was higher than the catalyst prepared via wet impregnation method (63.3%). The sonochemically synthesized Ni-Mo/γ-Al₂O₃ catalyst is found to be active, produces 80.87 wt% of diesel range hydrocarbons, and it gives high selectivity for Pentadecane (18.7 wt%), Hexadecane (16.65 wt%), Heptadecane (24.45 wt%) and Octadecane (21.0 wt%). The product distribution revealed that the deoxygenation reaction pathway was preferred. Higher conversion and higher HDO yield in this study are associated mainly with the change in concentration ratio between oxidation states of molybdenum (Mo⁴⁺, Mo⁵⁺, and Mo⁶⁺) on the external surface of the catalyst due to ultrasound irradiation during the synthesis process. Consequently, the application of sonochemically synthesized non-sulphided catalysts favored mainly hydrodeoxygenation of diesel range hydrocarbon.

Mechanistic insights into hydrodeoxygenation of phenol on bimetallic phosphide catalysts

Different binding modes of the reactant on different catalysts determine the hydrodeoxygenation selectivity.

Effective parameters on selective catalytic hydrodeoxygenation of phenolic compounds of pyrolysis bio-oil to high-value hydrocarbons

Selective hydrodeoxygenation of phenolic compounds present in pyrolysis bio-oil (phenol, cresol, guaiacol and anisole) to high-value hydrocarbons is a great function of catalyst properties and operating conditions.

Highly selective catalytic hydrodeoxygenation of Caromatic–OH in bio-oil to cycloalkanes on a Ce–Ni–W–B amorphous catalyst

Ce–Ni–W–B amorphous catalysts exhibited high activity in the hydrodeoxygenation (HDO) of C_aromatic–OH. The deoxygenation degree was up to 98.1% with low aromatics selectivity at 498 K. Both the aromatics content and reaction temperature were decreased, which realized the energy saving and consumption reduction in the HDO process.

Synthetic Fabrication of Nanoscale MoS2-Based Transition Metal Sulfides

Transition metal sulfides are scientifically and technologically important materials. This review summarizes recent progress on the synthetic fabrication of transition metal sulfides nanocrystals with controlled shape, size, and surface functionality. Special attention is paid to the case of MoS₂ nanoparticles, where organic (surfactant, polymer), inorganic (support, promoter, doping) compounds and intercalation chemistry are applied.