Hydrotalcite-Based Bimetallic PdNi Catalysts with High Sulfur Tolerance for the Hydrogenation of Dicyclopentadiene Resin

The catalytic hydrogenation of unsaturated bonds in petroleum resin is a promising way to enhance the properties of petroleum resin in terms of weather resistance, stability, and compatibility. However, the presence of sulfur compounds in petroleum resin poses a high challenge to hydrogenation catalysts. Herein, based on the cation-tunability of hydrotalcite-like compounds, a series of PdNi bimetallic catalysts are prepared by calcination–reduction of their hydrotalcite-like precursors and applied in the hydrogenation of dicyclopentadiene (DCPD) petroleum resin. By tuning the molar ratios of Pd/Ni and optimizing the reaction conditions, the optimal Pd1Ni1–MgAlO–HT catalyst can obtain the hydrogenated DCPD petroleum resin with saturation up to 91.5% at 255 °C, 10 MPa H2 pressure, and 3 h reaction time with the presence of 50 ppm sulfur compound. As compared with the monometallic catalyst, the PdNi bimetallic catalyst presents higher sulfur tolerance in the hydrogenation of DCPD petroleum resin. Combined with the analysis results of XRD, XPS, TEM, and H2-TPR, the enhanced catalytic performance of the Pd1Ni1–MgAlO–HT catalyst can be attributed to the small particle size, high dispersion of metal particles, and the synergy effect between Pd and Ni species. This work will guide to design a highly efficient sulfur tolerance catalyst derived from the hydrotalcite-like precursor for the hydrogenation of polymers

Steerable Engineering of Nickel Molybdenum Carbonitride Nanostructures for Catalytic Regioselectivity Cleavage of C–O and C–C Bonds in Deoxygenation of Methyl Palmitate

The rational exploit of fatty esters to obtain clean fuels can effectively solve the problems of energy depletion and carbon emission. The challenges are the optimal catalytic process and the development of highly efficient catalysts for the removal of oxygen from fatty esters in bioenergy. Herein, nickel molybdenum carbonitride (NixMoCN) nanostructures with low cost and Pt-like properties are simply obtained from one-step pyrolysis of a self-assembly NiMo-based organic–inorganic precursor and tested in the deoxygenation of methyl palmitate. The introduced Ni plays a great role in the phase composition and catalytic properties of NixMoCN with steerable nanoheterostructures. Regioselectivity cleavage of C–O and C–C bonds exists over NixMoCN nanocatalysts. The optimal Ni0.30MoCN with 49% β-Mo2C and 51% Ni2Mo3N shows 98.3% conversion and 100% deoxygenation degree, which are much higher than those of MoCN with a β-Mo2C phase (only 12.4% conversion and 51% deoxygenation degree at a contact time 0.35 min under 300 °C and 0.1 MPa). The main reaction route over the MoCN nanocatalyst is hydrodeoxygenation of methyl palmitate, while the hydrodeoxygenation and decarbonylation/decarboxylation of methyl palmitate compete over the Ni0.30MoCN nanocatalyst

In Situ Fabrication of the Al₂O₃@NiMo Core–Shell Catalyst from LDH for Low-Pressure Hydrodeoxygenation of Fatty Acid Methyl Ester

The hydrothermal stability of supported metal catalysts is one of the greatest challenges in the development of biomass conversion to chemicals and fuels. Herein, a hydrotalcite-based core–shell catalyst (Al2O3@NiMo-LDO) was synthesized by urea precipitation and ion-exchange methods, which could selectively convert bio-oil model compounds to liquid alkanes with high activity and selectivity and excellent hydrothermal stability at low pressure. In the hydrogenation of methyl palmitate, the catalyst afforded 81% conversion and 99% selectivity of n-pentadecane and n-hexadecane under low pressure, with excellent hydrothermal stability. The excellent catalytic performance of Al2O3@NiMo-LDO was attributed to the strong hydrogen activation ability, improvement of the utilization of active components under low pressure, and the increase in the number of active Mo5+ species. The superior hydrothermal stability was attributed to the core–shell structure, which avoided the influence of the specific surface area of Al2O3 that is reduced by the hydration reaction between Al2O3 and H2O at high temperature

Selective Hydrogenation of Anthracene to Symmetrical Octahydroanthracene over Al₂O₃‑Supported Pt and Rh Catalysts Prepared by Strong Electrostatic Adsorption

The hydrogenation of polycyclic aromatic hydrocarbons (PAHs) over highly efficient and stable catalysts to fine chemicals and intermediates for producing chemical materials is an effective approach to realize the high value-added utilization of coal tar and slurry oil. Herein, two kinds of Al2O3-supported Pt and Rh catalysts are synthesized by strong electrostatic adsorption (SEA) and used to catalyze the hydrogenation of anthracene. Compared with the traditional catalysts synthesized by wet impregnation, the Pt/Al2O3‑SEA and Rh/Al2O3‑SEA catalysts have smaller active metal particle sizes and higher dispersion, which can expose more active centers, showing higher catalytic activity. Interestingly, anthracene may be preferentially adsorbed on the surface of the Pt/Al2O3 catalyst in a parallel manner but on the surface of the Rh/Al2O3 catalyst in a lateral manner, which leads to the different hydrogenation routes. 9,10-Dihydroanthracene is an initial product for the hydrogenation of anthracene, which is rearranged into tetrahydroanthracene and subsequently hydrogenated to symmetrical octahydroanthracene (sym-OHA) over the Pt/Al2O3 catalyst. The high selectivity to sym-OHA (93%) with the conversion of anthracene near 100% can be achieved in the hydrogenation of anthracene at 240 °C and 7 MPa for 10 h. Additionally, due to the strong anchoring effect, the Pt/Al2O3‑SEA catalyst shows high stability for six cycles. This work supplies a new tactic to develop high-performance catalysts for selective hydrogenation of PAHs to important monomers for synthesizing chemical materials

Synthesis and Characterization of Ferromagnetic Nickel–Cobalt Silicide Catalysts with Good Sulfur Tolerance in Hydrodesulfurization of Dibenzothiophene

Preparation of highly active and excellent sulfur tolerant hydrodesulfurization (HDS) catalysts is very important for the removal the sulfur from the sulfur containing compounds in petroleum. Herein we report on the synthesis and characterization of ferromagnetic nickel–cobalt silicide (Ni1–xCoxSi2) solid solution catalysts having large surface area by the reaction of nickel cobalt oxide solid solutions with SiH4. The catalytic properties of Ni1–xCoxSi2 were investigated for HDS of dibenzothiophene (DBT). The results showed that the saturation magnetization of the Ni1–xCoxSi2 solid solutions with fluorite structure can be controlled by changing the molar ratio of Ni to Co. The nickel-rich Ni0.75Co0.25Si2 catalyst is much more active than that of monometallic silicide (NiSi2 and CoSi2) and significantly improves the hydrogenation property (31.5% HYD selectivity), proving the synergistic effect between the components. X-ray photoelectron spectroscopy (XPS) provided further evidence that the valence electron concentration of the Ni increased with increasing the Co substitution, enhancing the metal–silicon and metal–metal interactions. In addition, the Si sites in the silicides alter the metal coordination, leading to a strong modification of the electronic structure around the Fermi level of the metals. This engenders a high activity for the HDS of DBT and weakens the metal–sulfur bonds, improving the sulfur tolerance

Selective Ring-Shift Isomerization in Hydroconversion of Fluorene over Supported Platinum Catalysts

Hydroconversion of fluorene has been conducted over the zeolites and silica–alumina-supported platinum catalysts. The hydrogenation of aromatic rings, the hydroisomerization of the cycloalkanes, and the cracking reaction over the Pt/Y zeolite catalysts are studied to give a detailed hydroconversion reaction network of fluorene through conversion of the synthesized intermediates. Compared to the β-zeolites and silica–alumina supports used, the dispersed platinum catalysts on the Y-zeolites with unique cage structure and acidic properties selectively catalyze the ring-shift isomerization of perhydrofluorene with high yields of the dodecahydrocyclopenta­[a]­naphthalene and dodecahydrophenalene. Such hydroisomerization reaction is enhanced above 250 °C, while more cleavage of carbon–carbon bond occurs at higher temperatures (280–290 °C) which lead to the great production of single-ring cycloalkanes and more loss in carbons. In the comparative study of the support effect, an examination of the product yields indicates that mild acidity and unique zeolitic structure of Y-zeolites show a major contribution to the selective ring-shift isomerization of saturated aromatic rings. In addition, the generation of mesopores in the Y-zeolite crystals by postsynthesis alkaline treatment facilitates the mass transfer of compounds and provides an improved yield of isomers

Two-Step Conversion of Biomass-Derived Glucose with High Concentration over Cu–Cr Catalysts

The conversion of highly concentrated glucose was conducted over a Cu–Cr catalyst with a base in two steps for the first time. Reaction parameters such as reaction time, temperature, and H₂ pressure were optimized in each step. On the basis of these results, the corresponding reaction route was proposed. At the low-temperature step, and without a base, glucose was hydrogenated into sorbitol or isomerized and hydrogenated into mannitol. While in the presence of a base, the direct decomposition of glucose was observed because of base-catalyzed retro-aldol condensation. At the high-temperature step, it was found that the addition of a base greatly restrained the formation of oligosaccharides. Compared with CaCO₃, Ba­(OH)₂, KOH, and NaOH, Ca­(OH)₂ exhibited the best promotion, indicating that the conversion of glucose was relative to not only the concentration of OH^– but also the metal ionic radius and electric charge. The addition of a base had no obvious effect on the stability of Cu–Cr catalyst. In the recycling, the catalyst exhibited reasonable recyclability because of the partial deactivation originating from the migration of Cr onto Cu sites and the coverage of carbon species, as shown by X-ray photoelectron spectroscopy measurements

DataSheet1_Promotion of Au nanoparticles on carbon frameworks for alkali-free aerobic oxidation of benzyl alcohol.docx

We synthesized a series of modified Co-ZIF-67 materials with tunable morphology to support fine Au nanoparticles for the alkali-free aerobic oxidation of benzyl alcohol. Structure promotion was performed using Stöber silica as a hard template, which was subsequently removed by NaOH etching before gold immobilization. The texture structure of Au/(Si)C was greatly improved with increasing surface area and volume. CoOx was simultaneously introduced into the carbon shell from the Co-ZIF-67 precursor, which consequently facilitated the specific Au-support interaction via bimetallic synergy. XRD, XPS, and TEM images demonstrated the redispersion of both Au and CoOx as well as the electronic delivery between metals. Analysis of the chemical and surface composition suggested a surface rich in Auδ+ with abundant lattice oxygen contributed by CoOx in the final Au/(Si)C, which improved the transformation rate of benzyl alcohol even in an alkali-free condition. Au/(Si)C with finely dispersed Au particles showed excellent catalytic performance in the alkali-free environment, with 89.3% benzyl conversion and 74.5% benzaldehyde yield under very mild conditions.</p

In Situ FT-IR Spectroscopic Studies of CO Adsorption on Fresh Mo₂C/Al₂O₃ Catalyst

The surface sites of supported molybdenum carbide catalyst derived from different synthesis stages have been studied by in situ FT-IR spectroscopy using CO as the probe molecule. Adsorbed CO on the reduced passivated Mo2C/Al2O3 catalyst gives a main band at 2180 cm-1, which can be assigned to linearly adsorbed CO on Mo4+ sites. The IR results show that the surface of reduced passivated sample is dominated by molybdenum oxycarbide. However, a characteristic IR band at 2054 cm-1 was observed for the adsorbed CO on MoO3/Al2O3 carburized with CH4/H2 mixture at 1033 K (fresh Mo2C/Al2O3), which can be assigned to linearly adsorbed CO on Moδ+ (0 2C/Al2O3. Unlike adsorbed CO on reduced passivated Mo2C/Al2O3 catalyst, the IR spectra of adsorbed CO on fresh Mo2C/Al2O3 shows similarity to that on some of the group VIII metals (such as Pt and Pd), suggesting that fresh carbide resembles noble metals. To study the stability of Mo2C catalyst during H2 treatment and find proper conditions to remove the deposited carbon species, H2 treatment of fresh Mo2C/Al2O3 catalyst at different temperatures was conducted. Partial amounts of carbon atoms in Mo2C along with some surface-deposited carbon species can be removed by the H2 treatment even at 450 K. Both the surface-deposited carbon species and carbon atoms in carbide can be extensively removed at temperatures above 873 K