Mechanism of Hydrodenitrogenation on Phosphides and Sulfides

Reactivity of Sulfur and Nitrogen Compounds of FCC Light Cycle Oil in Hydrotreating over CoMoS and NiMoS Catalysts

NiMoS and CoMoS catalysts were synthesized and applied to hydrotreating (HDT) of FCC light cycle oils (FCC-LCO) in an autoclave batch reactor at 613 K and 8.6 MPa H2. The S and N compounds in LCO were classified into four and three groups, respectively, in terms of the HDT reactivity. The individual and the competitive reactivities of the S and N compounds in the HDS and the HDN were investigated over the conventional CoMoS and NiMoS catalysts using S and N model compounds (dibenzothiophene, DBT, and carbazole, CBZ). In the HDS of DBT, both the direct desulfurization (DDS) and pre-hydrogenation pathway (HYD) were found to proceed, whereas the HYD pathway was favored for the HDN of CBZ. As a result, the NiMoS catalyst that facilitates the HYD pathway showed better activity in the HDN of LCO than the CoMoS (k = 10.20 × 10−2 vs. 1.80 × 10−2 h−1). Indeed, the HDS of LCO over the NiMoS was more favorable than that over the CoMoS catalyst (k = 4.3 × 10−1 vs. 3.6 × 10−1 h−1).

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.

Progress in thermochemical conversion of duckweed and upgrading of the bio-oil: A critical review

The processing of duckweed has been included in the list of promising pathways for biofuels production. This property is attributed to its simple manual harvesting method and its ability for high protein or starch content, depending on its species and growing environment. The biofuels production from duckweed, is not only a solution to energy and environmental problems, but also a reliable way to realize the utilization of duckweed. This critical review focuses on the bio-oil production from duckweed via pyrolysis and hydrothermal liquefaction processes. First, characteristics and eco-environmental benefits of duckweed are reviewed. Next, the impacts of different parameters on the properties and distribution of bio-oil from pyrolysis and hydrothermal liquefaction are discussed in detail. Subsequently, the effect of hydrogen donor solvents (as reaction media for upgrading) and catalysts on the upgrading of duckweed bio-oil are extensively discussed. This paper ends with the prospects for further development in thermochemical valorization of duckweed.

Structure and Activity of Ni2P/Desilicated Zeolite β Catalysts for Hydrocracking of Pyrolysis Fuel Oil into Benzene, Toluene, and Xylene

The effects of desilication (DS) of the zeolite β on the hydrocracking of polycyclic aromatics were investigated using the Ni2P/β catalysts. The Ni2P/β catalysts were obtained by the temperature-programmed reduction (TPR) method, and the physical and chemical properties were examined by N2 physisorption, X-ray diffraction (XRD), 27Al magic angle spinning–nuclear magnetic resonance (27Al MAS NMR), extended X-ray absorption fine structure (EXAFS), isopropyl amine (IPA) and NH3 temperature-programmed desorption (TPD), CO uptake, and thermogravimetric analysis (TGA). The catalytic activity was examined at 653 K and 6.0 MPa in a continuous fixed bed reactor for the hydrocracking (HCK) of model compounds of 1-methylnaphthalene (1-MN) and phenanthrene or a real feedstock of pyrolysis fuel oil (PFO). Overall, the Ni2P/DS-β was observed as more active and stable in the hydrocracking of polycyclic aromatics than the Ni2P/β catalyst. In addition, the Ni2P/β suffered from the coke formation, while the Ni2P/DS-β maintained the catalytic stability, particularly in the presence of large polycyclic hydrocarbons in the feed.

Effects of calcination and reduction temperature on the properties of Ni-P/SiO2 and Ni-P/Al2O3 and their hydrodenitrogenation performance

A series of SiO₂-supported and γ-Al₂O₃-supported nickel phosphides were prepared by temperature-programmed reduction (TPR) with different calcination and reduction temperatures. The prepared catalysts were characterized by XRD, BET, H₂-TPR, CO titration and HRTEM. The crystal phase and CO uptake content were influenced by calcination and reduction temperature. The catalytic performance of various catalysts was tested in quinoline hydrodenitrogenation and exhibited considerable differences. The quinoline HDN activity of SiO₂-supported nickel phosphides decreases with increase of calcination and reduction temperature. In contrast to SiO₂-supported samples, the ability to remove nitrogen of γ-Al₂O₃-supported samples increases with reduction temperature.

XRD patterns of different SiO₂-supported nickel phosphides reduced at (a) 560 °C, (b) 650 °C, (c) 750 °C and different γ-Al₂O₃-supported nickel phosphides reduced at (d) 560 °C, (e) 650 °C, (f) 750 °C.

Preparation and characterization of NiW supported on Al-modified MCM-48 catalyst and its high hydrodenitrogenation activity and stability

Al-containing MCM-48 with different Si/Al ratios and aluminum free MCM-48 materials were successfully prepared with CTAB and P123 as a co-template.

Initial hydrogenations of pyridine on MoP(001): a density functional study

The initial hydrogenations of pyridine on MoP(001) with various hydrogen species are studied using self-consistent periodic density functional theory (DFT). The possible surface hydrogen species are examined by studying interaction of H(2) and H(2)S with the surface, and the results suggest that the rational hydrogen source for pyridine hydrogenations should be surface hydrogen atoms, followed by adsorbed H(2)S and SH. On MoP(001), pyridine has two types of adsorption modes, i.e., side-on and end-on; and the most stable η(5)(N,C(α),C(β),C(β),C(α)) configuration of the side-on mode facilitates the hydrogenation of pyridine. The optimal hydrogenation path of pyridine with surface hydrogen atoms in the Langmuir-Hinshelwood mechanism is the formation of 3-monohydropyridine, followed by producing 3,5-dihydropyridine, in which the two-step hydrogenations take place on the C(β) atoms. When adsorbed H(2)S is considered as the source of hydrogen, slightly higher hydrogenation barriers are always involved, while the energy barriers for hydrogenations involving adsorbed SH are much lower. However, the hydrogenation of pyridine should be suppressed by the adsorption of H(2)S, and the promotion effect of adsorbed SH is limited.

Design of a high-temperature and high-pressure liquid flow cell for x-ray absorption fine structure measurements under catalytic reaction conditions

The design and performance of a new high-pressure and high-temperature cell for measurement of x-ray absorption fine structure (XAFS) spectra of solid catalysts working in a flowing liquid are presented. The cell has flat, high-purity sintered cubic boron nitride (c-BN) windows which can tolerate high temperature (900 K) and high pressure (10 MPa). The c-BN is a new material which has the highest tensile strength, second only to diamond, and is also chemically and thermally stable. The use of the cell is demonstrated for measurements of PtPdAl(2)O(3) and Ni(2)PSiO(2) hydrodesulfurization catalysts at reaction conditions. A technique called delta chi (Deltachi), involving determining the difference between XAFS spectra of the sample at reaction conditions and the bare sample, is introduced.