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Carbon nanotube (CNT)-supported Ni-modified MoS2 catalysts with ultra-high loading were synthesized with the assistance of citric acid. The morphology of the nanoflake arrays could be controlled to give abundant stepped sites, which favored the hydrogenation desulfurization pathway of dibenzothiophene. The catalyst exhibited excellent performance and stability for hydrodesulfurization of model oil and coal-to-liquid fuel. [ABSTRACT FROM AUTHOR]

We report carbon can be activated as metal-like hydrogenation catalyst for the selective hydrogenation of nitroarenes. Using DFT calculations we demonstrated the combination of P dopant and lattice defect in carbon can cause significant electron delocalization and change the band structure to a metal-like one, and thus both H2 and the nitro group are easily activated for selective hydrogenation. Then we fabricated this carbon catalyst with tunable concentration of P dopant and lattice defects by polymerization and carbonization of phytic acid, and found the concentration of lattice defect is closely related to that of P-dopants. The synthesized catalyst exhibits superior catalytic activity, perfect selectivity, and stability in the hydrogenation of nitroarenes, outperforming the reported metal-free, metal-oxide, and nickel catalysts. Importantly, the hydrogenation activity is linearly dependent on the P-doping and/or defect concentration, perfectly agreeing with the DFT calculation. This work is expected to provide a cheap way for large-scale production of anilines using metal-like carbon catalyst. [ABSTRACT FROM AUTHOR]

Abstract: Hydrogenation of dicyclopentadiene (DCPD) to tetrahydrodicyclopentadiene (THDCPD) over nickel alloy catalyst SRNA-4 has been studied. GC–MS analysis showed that the reaction is a consecutive process with two hydrogenated intermediates. DFT simulation confirmed the double bond in norbornene ring is easier to saturate than that in cyclopentene ring, so the major intermediate is 8,9-dihydrodicyclopentadiene (8,9-DHDCPD). In comparison with Raney Ni, SRNA-4 shows a significantly higher activity and makes the reaction proceed at lower temperature. The reaction conditions including temperature and hydrogen pressure were optimized. The optimal hydrogen pressure is 1.5MPa. To avoid the decomposition of DCPD, a two-stage operation was designed: 373K for 1h and then 403K for another 4h. Under these conditions, the yield of THDCPD reaches 98.5%. The apparent kinetics was also calculated using the concentration–time data obtained in the experiments. The activation energy for DCPD to 8,9-DHDCPD and 8,9-DHDCPD to THDCPD reaction is 22.8kJ/mol and 40.9kJ/mol, respectively. [Copyright &y& Elsevier]

Abstract: Pd-B/γ-Al2O3 amorphous catalysts were prepared through impregnation and KBH4 reduction for the hydrogenation of tricyclopentadiene. The effects of reduction conditions, pre-calcination and thermal annealing on the hydrogenation activity were studied. It is found that the reduction should be conducted in ice water batch with KBH4 solution added by dropping to avoid the crystallization of amorphous metals. Pre-calcination of the catalyst before reduction can increase the amount of Pd on the prepared catalyst. With pre-calcination at 200°C, the highest hydrogenation turnover frequency is obtained. The amorphous catalyst is thermally stable at temperature below 150°C. When annealed at higher temperature, the amorphous metals are gradually crystallized and the particle size is increased. After annealing at 600°C, the catalyst is uniformly crystallized. It is noticed that the size of amorphous Pd calculated from H2-adsorption is much smaller than the actual size observed by transmission electron microscope (TEM). This indicates that amorphous metal has stronger H2-adsorption ability than crystal metals with comparative particle sizes. The hydrogenation activity decreases with the increase of annealing temperature. Moreover, the hydrogenation activity is solely dependent on the amount of H2-adsorption, suggesting that the excellent performance of amorphous catalyst should be attributed to their better H2-adsorption ability. [Copyright &y& Elsevier]

The d-band center position of the metal catalyst is one of the most important factors for catalytic selective hydrogenation, e.g., the conversion of nitrostyrene to aminostyrene. In this work, we modulate the d-band center position of the Pt surface via H coverage manipulation in order to assess the highly efficient selective hydrogenation catalyst using density functional theory (DFT) calculation, which is validated experimentally. The optimal transition metal catalysts are first screened by comparing the adsorption energy values of two ideal models, nitrobenzene and styrene, and by correlating the adsorption energy with the d-band center positions. Among the ten transition metals, Pt nanoparticles have a good balance between selectivity and the conversion rate. Then, the surface hydrogen covering strategy is applied to modulate the d-band center position on the Pt (111) surface, with the increase of H coverage leading to a decline of the d-band center position, which can selectively enhance the adsorption of nitro groups. However, excessively high H coverage (e.g., 75% or 100%) with an insufficiently low d-band center position can switch the chemisorption of nitro groups to physisorption, significantly reducing the catalytic activity. Therefore, a moderate d-band center shift (ca. −2.14 eV) resulted in both high selectivity and catalytic conversion. In addition, the PtSn experimental results met the theoretical expectations. This work provides a new strategy for the design of highly efficient metal catalysts for selective hydrogenation via the modulation of the d-band center position. [ABSTRACT FROM AUTHOR]

For selective hydrogenation of chemicals the high selectivity is always at the expense of activity and improving both selectivity and activity is challenging. Here, by chelating with p‐fluorothiophenol (SPhF)‐arrays, both steric and electronic effects are created to boost the performance of cheap nickel‐based catalysts. Compared with dinickel phosphide, the SPhF‐chelated one exhibits nearly 12 times higher activity and especially its selectivity is increased from 38.1% and 21.3% to nearly 100% in hydrogenations of 3‐nitrostyrene and cinnamaldehyde. Commercial catalysts like Raney Ni chelating with SPhF‐array also exhibits an enhanced selectivity from 20.5% and 23.4% to ≈100% along with doubled activity. Both experimental and density functional theory (DFT) calculation prove that the superior performance is attributed to the confined flat adsorption by ordered SPhF‐arrays and downshifted d‐band center of catalysts, leading to prohibited hydrogenation of the vinyl group and accelerative H2 activation. Such a surface modification can provide an easily‐realized and low‐cost way to design catalysts for the selective hydrogenation. [ABSTRACT FROM AUTHOR]

Liquid organic hydrogen carrier technology is a promising alternative for hydrogen storage and transportation. Benzyltoluene (BT) is a high-performance hydrogen storage carrier, but the hydrogenation kinetic parameters that are important to guide reactor and catalyst design are not clear. Here, we systematically investigated the kinetics of BT hydrogenation over a supported Ni catalyst for its potential application in hydrogen storage. Our results suggest that BT hydrogenation reaction follows a two-step series reaction from BT to 12H-BT with 6H-BT as the intermediate. The reaction order is 0 and 1 with respect to BT and 6H-BT concentration, respectively, whereas that with respect to H 2 pressure is approximately equal (1.0 and 1.1 for BT and 6H-BT hydrogenation, respectively). Calculated activation energy suggests that 6H-BT hydrogenation is the rate-determining step in the whole process. Moreover, both kinetic and DFT results indicate that the presence of BT would inhibit the further 6H-BT hydrogenation to 12H-BT. This study is expected to provide a new understanding of BT hydrogenation reactions and a useful guideline for reactor and catalyst design. • This work investigated BT hydrogenation kinetics over Ni catalysts for its application in hydrogen storage. • BT hydrogenation follows a two-step reaction via 6H-BT intermediates, and 6H-BT hydrogenation is the rate-limiting step. • Experimental and theoretical results indicate BT has an inhibitory effect on the 6H-BT hydrogenation. [ABSTRACT FROM AUTHOR]

[Display omitted] • A highly selective hydrodeoxygenation of 5-hydroxymethylfurfural was conducted by intelligent regulation and usage of Ni/MCM-41 and Pt-WO X /t-ZrO 2. • 1-hexanol in 76 % yield is firstly synthesized using 5-hydroxymethylfurfural. • The mechanism of synthesis of 1-hexanol using 5-hydroxymethylfurfural is explored. • 5-hydroxymethylfurfural is a biomass. Metal-metal oxide catalysts are robust in selective hydrodeoxygenation of biomass derives. Herein, 1-hexanol in total yield about 76 % is firstly achieved by high selective hydrodeoxygenation of 5-hydroxymethylfurfural over Ni/MCM-41 and Pt-WO X /t-ZrO 2. By controlling the amount ratio of Ni/Ni2+ to 0.46, a 99.9 % yield of 2,5-tetrahydrofurandimethanol was achieved from 5-hydroxymethylfurfural by Ni/MCM-41. Subsequently high yield of 76 % of 1-hexanol was obtained by competing pathways of tandem reactions beginning at SN2 reaction at the epoxy atom of 2,5-tetrahydrofurandimethanol to enol/tautomer intermediates and ending with controllable selective hydrogenation. The reaction mechanism is explored and the reaction-oriented regulation is realized by the additional strong BrÖnsted acid sites generated by electron transfer from W to Pt and the appropriate amount of Pt0 sites of Pt-WO X /t-ZrO 2 , where the ratios of W5+/W6+ and Pt0/Pt2+ are 0.31 and 4.58 respectively. This work provides a new and green method for the synthesis of 1-hexanol and expands the utilization of metal–metal oxide in making value-added products using sustainable feedstocks. [ABSTRACT FROM AUTHOR]

[Display omitted] • NiM-2 is prepared as the non-precious metal catalyst for olefins and aromatics hydrogenation. • NiM-2 have more active sites due to high dispersion and easier oxidized Ni species reduction. • The connection between d-band center and di-σ adsorption is firstly confirmed. • Higher d-band center of NiM-2 boost adsorption and activation of C = C bonds. • NiM-2 shows excellent activity compared with commercial and reported Ni-based catalyst. Hydrogenation of olefins and aromatics is of significance for fuel processing and hydrogen storage, and developing nickel (Ni) catalyst highly active at low reaction temperature is the key to low the process cost. Herein we developed an ammonium citrate assisted impregnation method to fabricate loaded Ni catalyst (NiM-2) for hydrogenation. The Ni2+ species are anchored on the support MCM-41 strongly and evenly in form of Ni-citrate complex via the H-bonding between Si-OH group of MCM-41 and –COO- of citrate. During reduction, the carbon layers temporarily formed by carbonization of citrate species inhibit the transfer and sintering of Ni species, and finally induces ultra-small metallic Ni nanoparticles after carbon layers slow decomposition by Ni species. Low coordination numbers and strong electron interaction between small metallic Ni nanoparticles and MCM-41 support upshift the d-band center of metallic Ni atoms. In hydrogenation, the small particle size and easier reduction for oxidized Ni species provide abundant active sites for reaction, and the upshifted d-band center induces strongly adsorption and activation of C = C bonds, which is confirmed for the first time in our work. As a result, the catalyst exhibits superior activity compared with reported and commercial Ni-based catalysts for hydrogenation of olefins and aromatics. Specifically, the catalyst with higher Ni loading (18%) exhibits good activity under room temperature and 0.1 MPa for hydrogenation of dicyclopentadiene and are comparable to Pd catalysts, making it as one of the best non-precious metal catalysts for hydrogenation reaction. And also, NiM-2 shows extremely high stability. [ABSTRACT FROM AUTHOR]

Crystal facet engineering and defect engineering are both critical strategies to improve the catalytic hydrogenation performance of catalyst. Herein, ethylene hydrogenation on the perfect and oxygen defective Co 3 O 4 (110) surfaces has been studied by using periodic density functional theory calculations. The results are compared with that on Co 3 O 4 (111) surface to clarify the problem of which facet for Co 3 O 4 is more reactive, and to illuminate the role of oxygen vacancy. The low oxygen vacancy formation energy suggests that Co 3 O 4 (110) surface with defective site is easily formed. The whole mechanism of H 2 dissociation and stepwise hydrogenation of ethylene to ethane is examined, and the most favorable pathway is heterolytic dissociation of H 2 follows two stepwise hydrogenation of ethylene process. The results show that ethyl hydrogenation to ethane on perfect Co 3 O 4 (110) surface is the rate limiting step with an activation energy of 1.19 eV, and the presence of oxygen vacancy strongly reduces the activation energies of main elementary steps, and the activation energy of rate limiting step is only 0.47 eV. Compared with that on Co 3 O 4 (111), ethylene hydrogenation is preferred on Co 3 O 4 (110) surface. Therefore, Co 3 O 4 with exposed (110) facet is predicted as an excellent catalyst for ethylene hydrogenation. [ABSTRACT FROM AUTHOR]

Biofuels are important alternative for fossil-based fuel but they have either relatively low density or high freezing point and viscosity. Here we reported a simple and efficient route to synthesis biofuel with density comparable to widely used JP-10 fuel as well as good low-temperature properties. Substituted diphenyl methane was synthesized by acid catalytic alkylation of lignin-derived phenols (phenol, anisole, guaiacol) with benzyl ether or benzyl alcohols, and MMT-K10 exhibits better activity than HPW, Amberlyst-15, and Al-MCM-41, due to the modest acid strength and open lamellar structure. High selectivity along with good-to-excellent conversion was obtained under optimized conditions regardless of different reactant used. Then the alkylated product was subjected to hydrogenation with the presence of Pd/C and HZSM-5, and interestingly, intramolecular cyclization reaction occurred to produce a large amount of perhydrofluorene as well as dicyclohexylmethane. Subsequently, biofuel with density as high as 0.93 g/mL and freezing point as low as −40.0 °C was obtained, which surpasses the state-of-art of biofuel reported. [ABSTRACT FROM AUTHOR]

Herein, an efficient domino synthesis for N-aryl pyrroles and tetrahydropyrroles from biomass-derived furan alcohols (i.e., 5-methyl furfuryl alcohol, and 2,5-bis(hydroxymethyl)furan) and nitrobenzenes was reported for the first time over metal phosphides. Dual active sites, including metal sites for nitro hydrogenation, acid sites for furan alcohol ring-opening determine the catalytic performance. Different from traditional tandem catalysts of Pd/C and HZSM-5 or Amberlyst-15 that suffer from binary competitive adsorption of furan and nitro groups on metal sites, as well as hydroxyl and hydrogenated amino groups on the acidic sites, metal phosphides show unexpected cooperative catalytic properties with the oriented synthesis of pyrroles over NiCoP and tetrahydropyrroles over Ni 2 P. Furthermore, the catalyst displays outstanding stability and recycling performance after 4 runs. This work demonstrates an effective strategy for governing reaction routes by selective activation and shows the powerful synergistic effect of hydrogenation and acid catalysis. [Display omitted] • A series of metal phosphides (NiCoP, Ni 2 P, Co 2 P) were prepared. • N-aryl pyrroles were obtained from furan alcohols and nitrobenzenes over NiCoP. • N-aryl tetrahydropyrroles were obtained over Ni 2 P. • Selective hydrogenation and acid activation ensure the synergistic catalysis. • The catalysts show excellent recycling stability. [ABSTRACT FROM AUTHOR]

Recently, metal oxides are attracting increasing interests as hydrogenation catalyst. Herein we studied the hydrogenation of ethylene on perfect and oxygen defective Co 3 O 4 (1 1 1) using periodic density functional theory. The energetics and pathways of ethylene hydrogenation to ethane were determined. We have demonstrated that (i) H 2 dissociation on Co 3 O 4 is a complicated two-step process through a heterolytic cleavage, followed by the migration of H atom and finally yields the homolytic product on both perfect and oxygen defective Co 3 O 4 (1 1 1) surfaces easily. (ii) After introducing the surface oxygen vacancy, the stepwise hydrogenation of ethylene by atomic hydrogen is much easier than that on perfect surface due to the weaker bond strength of OH group. The strength of O H bond is a crucial factor for the hydrogenation reaction which involves the breakage of O H bond. The formation of oxygen vacancy increases the electronic charges at the adjacent surface O, which reduces its capability of further gaining electrons from adsorbed atomic hydrogen and then weakens the strength of O H bond. These results emphasize the importance of the oxygen vacancies for hydrogenation on metal oxides. [ABSTRACT FROM AUTHOR]

• Acetylene hydrogenation over Fe x O y clusters are theoretically investigated. • Acetylene hydrogenation over 5FeO cluster is impossible for the high energy barrier. • Acetylene hydrogenation to ethane over Fe 2 O 3 cluster is kinetically most favorable. The acetylene hydrogenation reaction over FeO, Fe 2 O 3 and Fe 3 O 4 clusters are theoretically investigated, via C 2 H 2 adsorption, approach of molecular H 2 to cluster, H 2 dissociation on Fe O bond, and the sequential addition reaction of H atom. Over FeO cluster, the extremely high barrier for the addition reaction of H atom adsorbed on O atom (of cluster) predicts the impossible acetylene hydrogenation. Over Fe 2 O 3 cluster, the overall barriers for H 2 dissociation, addition reaction of two hydrogen atom are respectively 26.6, 32 and 31.8 kcal·mol−1 during the acetylene hydrogenation to form ethylene and 26.5, 35.5 and 9.1 kcal·mol−1 for its further hydrogenation to produce ethane. During the further hydrogenation pathway, the migration of semi-hydrogenated product C 2 H 3 requires extra energy of 30.7 kcal mol−1. These barriers are lower than those of the pathways over Fe 3 O 4 cluster. Hence, among three Fe x O y clusters, hydrogenation of acetylene to produce ethane on Fe 2 O 3 cluster is kinetically most favorable. [ABSTRACT FROM AUTHOR]

• The impacts of hydrogenation degree on jet fuel oxidation were investigated. • The impacts of hydrogenation degree on jet fuel deposition were investigated. • The oxidation products of jet fuels were analyzed by GC × GC–MS. • The roles of heteroatomic species and aromatics in thermal oxidative stability were analyzed. Thermal oxidative stability is a key issue for jet fuel serving as a coolant of high-performance aircraft. This study investigated the effects of the hydrogenation degree on the oxidation and deposition of jet fuel (RP-3). Fuels with different hydrogenation degrees were achieved by a commercial catalyst, with the aromatic content reduced from 12.6 wt% to 0.4 wt%, resulting in a slight density decrease and a slight increase of the net heating value. Meanwhile, the total sulfur content of hydrogenated fuel was lowered to below 1 ppm, and the naturally occurring phenols were completely removed. The initial oxidation reactivity and deposition tendency of hydrogenated fuels were investigated by pressure differential scanning calorimetry and jet fuel thermal oxidation tester, respectively. For the initial oxidation, both the oxidation OT (onset temperature) and IP (induction period) of jet fuel decrease with increasing hydrogenation degree and show good linear correlations with the aromatic content. For thermal deposition, pristine RP-3 cannot pass the JFTOT test (355 °C for 5 h), while all hydrogenated RP-3- t can pass 355 °C JFTOT test, owing to the almost total removal of inherent heteroatomic species (sulfurs and phenols) by hydrogenation. This work confirms that deep hydrogenation is a promising approach to improve the thermal oxidative stability of jet fuel (fewer deposits) for the practical applications. [ABSTRACT FROM AUTHOR]