Search

Graphical abstract Highlights • Ga geometrically and electronically modify Ni in Ni-Ga alloy and IMC. • Direct deoxygenation (DDO) was more preferential on Ni-Ga alloy and IMC than Ni. • Benzene hydrogenation, C C cleavage and methanation was suppressed on alloy and IMC. • H 2 was generated from anisole via methanol decomposition on Ni-Ga alloy and IMC. • There was a synergetic effect between Ni and Ga on alloy and IMC for HDO. Abstract Herein, Ni/SiO 2 and bimetallic Ni x Ga/SiO 2 (Ni/Ga atomic ratio x = 6 and 3) catalysts were prepared by the impregnation method followed by reduction at 550 °C and tested in the vapor hydrodeoxygenation of anisole at 0.1 MPa and 300 °C. Ni-Ga alloy and Ni 3 Ga intermetallic compound (IMC) formed in Ni 6 Ga/SiO 2 and Ni 3 Ga/SiO 2 , respectively, where the Ga atoms break contiguous Ni ones reducing the ensembles of Ni atoms and the H 2 uptakes. Also, a charge transfer from Ga to Ni increased the electron density of Ni, and hydrogen spill-over occurred on Ni x Ga/SiO 2. In contrast to Ni/SiO 2 , Ni x Ga/SiO 2 improved not only the hydrodeoxygenation activity but also the selectivity to benzene. At the similar anisole conversion (˜31%), the selectivity to benzene was 75.2%, 83.0% and 92.6% on Ni/SiO 2 , Ni 6 Ga/SiO 2 and Ni 3 Ga/SiO 2 , respectively. Reactivity evaluation, anisole-TPD and TPSR results show that the direct C Ar OCH 3 bond cleavage (C Ar represents the carbon in benzene ring) to benzene was more preferential on Ni x Ga/SiO 2 than on Ni/SiO 2. Isotope tracing experiment indicates that the spilt-over hydrogen at the interface between the Ni 3 Ga particles and support participated in the reaction. We suggest that the synergetic effect between Ni and Ga facilitated the direct C Ar O bond cleavage. Moreover, Ni x Ga/SiO 2 were less active for benzene hydrogenation and C C bond hydrogenolysis than Ni/SiO 2 , contributing to higher selectivity to benzene. Significantly, methanol, derived from the direct the C Ar OCH 3 bond cleavage, dominatingly decomposed to CO and H 2 and methanation scarcely occurred on Ni x Ga/SiO 2 , however, it was mainly converted to methane on Ni/SiO 2. Low activities for benzene hydrogenation, C C bond hydrogenolysis and methanation on Ni x Ga/SiO 2 (especially Ni 3 Ga/SiO 2) are attributed to the geometric and electronic effects of Ga in alloy and IMC. The finding is significant in rationally designing the catalyst with high benzene yield and low H 2 consumption. [ABSTRACT FROM AUTHOR]

Abstract: Hydrotreating catalyst NiMo/Al2O3 was modified by adding nano-sized zeolite beta and by hydrothermal treatments. The catalysts were characterized by BET, XRD, Pyridine-IR, 29Si NMR, 27Al NMR and TEM. The results showed that the addition of nanobeta could significantly enhance the hydrodesulfurization (HDS), hydrogenation, and hydrocracking abilities of the NiMo catalysts. The catalytic performance decreased in the order NiMo(C)>NiMo(15)>NiMo(D)>NiMo(7.5)≫NiMo/Al2O3. The presence of nanobeta could strengthen acid sites which facilitated the abilities of hydrocracking and removal of sulfur-containing compounds, especially those of refractory nature. Introduction of nanobeta could also induce the synergetic effect between NiMoS and the support material with thicker NiMoS slabs. This morphology change might be responsible for the improvement in hydrogenation. It was observed that hydrothermal treatment conditions could affect the acidity and the NiMoS morphology of the catalysts, which in turn alter the catalyst hydrogenation ability. [Copyright &y& Elsevier]

Abstract: The hydrogenation and hydrocracking performances of a series of MoNi/Al2O3 catalysts were evaluated with 4,6-dimethyl dibenzothiophene (4,6-DMDBT), 1-methylnaphthalene, pyridine, and hexadecane as model compounds. Different materials which involved amorphous silica–alumina, and hydrothermally treated zeolite beta and zeolite Y were introduced as part of the catalyst supports. The catalysts were characterized by BET, NH3 temperature programmed desorption (NH3-TPD), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). The addition of zeolites in the catalysts could greatly improve the hydrodesulfurization and hydrodenitrogenation activities, but it had have little enhancement in the hydroconversion of 1-methylnaphalene. The comparison among zeolite beta containing catalysts with various zeolite content (5–20wt%) indicated that the optimum hydrogenation activity was achieved by the catalyst containing 10wt% zeolite beta. A considerable amount of hexadecane was hydrocracked on zeolite containing catalysts. The hydrocracking of hexadecane proportionally increased with the zeolite content. Zeolite Y appeared to be more effective in enhancing the hydrotreating activity than zeolite beta. The high hydrogen pressure not only considerably increased hydrodearomatization activity, but also greatly suppressed the cracking of hexadecane in the feed. [Copyright &y& Elsevier]

Abstract: Four W–Ni catalysts, containing Al2O3, chemically treated zeolite Y, hydrothermally treated zeolite beta, and the combination of the above zeolite Y and beta, were prepared. The catalysts were characterized by BET, NH3-TPD, XRD, TEM, pyridine-IR, and XPS. The reaction performance in hydrodesulfurization (HDS), hydrodenitrogenation (HDN), and hydrodearomatation (HDA) was evaluated with light cycle oil (LCO). The zeolite-containing catalysts exhibited much higher HDN, HDS, and HDA activities than the WNi/Al2O3. The three zeolite-containing catalysts had similar HDN activity. The WNi/Beta+Y and WNi/Beta catalysts had higher HDS activity than the WNi/Y catalyst. The higher HDN, HDS, and HDA activities of the three zeolite-containing catalysts are associated primarily with enhanced hydrogenation activity and increased acidity. [Copyright &y& Elsevier]

CH3OH is an energy carrier that can be generated from renewable resources and be used as a fuel in fuel cells and internal combustion engines and a platform chemical for the synthesis of value‐added chemicals or gasoline. Carbon dioxide (CO2) hydrogenation is one of the widely researched methods to generate methanol. The traditional CO2 hydrogenation reaction method (requires high H2 pressure and temperatures) has attracted considerable attention. However, the new emerging field of catalysis referred to as nonthermal plasma (NTP) catalysis has also been developed extensively for methane reforming and CO2 hydrogenation to methane and CO. The plasma‐assisted approach not only presents remarkable advantages, such as room temperature and atmospheric H2 pressure but also has great potential to be powered by renewable electricity in a flexible way since it can be easily switched on/off. In this account, we review the recent articles published on methanol synthesis from CO2 and H2 using NTP. We reviewed and discussed the mechanism of this reaction under NTP, the modification of the reactor configurations, and the rationale behind the catalyst design. In the end, we discussed the advantages and disadvantages of each of these works and the future perspectives of this interesting privileged reaction. We believe this review is of interest to researchers active in sustainable heterogeneous catalysis. [ABSTRACT FROM AUTHOR]

The design and synthesis of highly dispersible and accessible Cu(I)-containing catalysts as efficient catalysts for the hydrogenation of CO 2 to alcohols has attracted considerable interest. Copper-based metal-organic framework (Cu-MOF) is considered one appropriate ideal precursor to prepare a porous Cu(I)-containing catalyst owing to their unique coordination assembly that can significantly prevent the aggregation of copper species during reduction. However, the thermal sensitivity of Cu-MOF makes it challenging to develop an efficient reduction strategy. Herein, we report a novel plasma reducing treatment (PRT) method that can reduce HKUST-1 in a DBD reactor at atmospheric pressure and near room temperatures (40°C). In addition, the PRT method requests short reduction time without the need for post-treatment. In this work, various reducing agents, including hydrogen gas, carbon monoxide, and methanol, have been investigated to manipulate the copper valence. The highly reactive reducing agents that are excited by the DBD plasma discharge at nearly ambient conditions, penetrate into the inner porous structure of Cu-MOFs to achieve efficient conversion of Cu(II) sites to Cu(I) without affecting the overall crystallinity. CO demonstrates the best reduction result. 79.9% Cu(II) was converted to Cu(I) within only 3 h, and the MOF crystal structure is well preserved. The obtained Cu(I)-HKUST catalyst exhibited good selectivity of alcohols in the plasma-assisted CO 2 hydrogenation. The work confirms that the PRT method is a superior approach for reducing thermal-sensitive catalysts. [Display omitted] • A novel plasma reducing treatment (PRT) for valence modulation of Cu-MOF under mild conditions (40°C) was developed. • The proposed PRT strategy is a controllable and environmentally friendly procedure without any solvent or post-treatment. • The CO-PRT method efficiently reduced 78% of Cu(II) to Cu(I) species in only 3 h based on HKUST-1 as a template. • The influencing factors of reduction efficiency among different reducing plasmas were investigated. • The CO 2 hydrogenation reaction was in situ performed over the reduced catalyst exhibiting good alcohol product selectivity. [ABSTRACT FROM AUTHOR]

The localized plasmon resonance (LSPR) is recognized as an effective way to convert incident light energy and significantly boost the catalytic reaction. However, a comprehensive understanding of the plasmon-thermo coupling mechanism is still lacking. To address this knowledge gap, we investigate reaction pathway and plasmonic enhancement mechanism of the photo-thermo coupled catalytic reverse water gas shift (RWGS) reactions over Au/γ-Al 2 O 3. The results indicate that both formate and carboxyl pathways contribute to the overall reaction. The m-formate pathway is suggested as the main reaction mechanism at low reaction temperature over small Au NPs. Spectro-kinetics and theoretical calculation analyses indicate that the plasmonic energy preferentially transfers to HCOO* via a combination of hot electron and resonance energy transfer mechanisms. The plasmonic energy facilitates the dehydration of HCOO* to CO, which is the rate-determining step (RDS) of the overall RWGS reaction. [Display omitted] • Plasmon enhances the CO 2 hydrogenation rate by ∼211.8 % over Au/Al 2 O 3. • m-HCOO* is demonstrated as the main reaction intermediate over small-size Au/Al 2 O 3. • br-HCOO* is proven as a reaction intermediate contributing to CO production. • Plasmon preferentially enhances the br-HCOO* pathway via promoting its dehydration. • Both "hot" electrons and resonance energy transfer are the promoting mechanisms. [ABSTRACT FROM AUTHOR]

SYNOPSIS: Coupling photo- and thermo- catalytic CO 2 hydrogenation is a promising way to convert CO 2 with higher sustainability. Herein, the redox pathway is demonstrated as the main reaction pathway for CO 2 hydrogenation at 200 °C over Au/TiO 2. The plasmonic enhancement mechanism is proven to be the facilitated oxygen vacancy generation. [Display omitted] • Plasmon enhances the CO production rate by ∼ 318 % at 200 °C over Au/TiO 2. • Redox mechanism is proven as the main pathway for CO 2 hydrogenation to CO. • DRIFTS analyses prove the spontaneous dissociation of CO 2 at V O site of Au/TiO 2. • Inverse H/D kinetic isotope effects suggest the V O creation is the RDS. • Plasmon-thermo coupling mechanism is the hot-electrons enhanced V O creation. Using solar energy to promote the thermocatalytic CO 2 conversion is a promising way to reduce the energy consumption and increase the sustainability. Au/TiO 2 is known for its good catalytic activity in both thermo- and photo- catalytic CO 2 conversion, however both the reaction mechanisms in dark and in photo-thermo coupled reaction condition remain unclear. In this work, the operando isotope-labelled spectroscopic and computational analyses are combined to clarify these mechanisms. The redox mechanism that CO 2 direct dissociation at the oxygen vacancy (V O) is found as the main reaction pathway of CO 2 hydrogenation over Au/TiO 2. The plasmonic enhancement mechanism is proven to be the hot electrons facilitated V O generation at interface. The clear understandings of reaction pathway and plasmonic enhancement mechanism are helpful for the future design of photo-thermal CO 2 conversion catalysts. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents the contribution of hydrogen spillover to the hydrogenation of naphthalene over Pt/RHO catalysts. Platinum supported on RHO zeolite was prepared by adding a Pt precursor to the synthesis gel of RHO zeolite. Pt/RHO catalysts were characterized by XRD, TEM, TPR and XPS. The hydrogenation activity was tested using 1-hexene, 1-cyclohexene and naphthalene as model compounds. XRD and TEM results indicated that incorporating Pt precursors into the synthesis gel did not affect the crystal structure and the morphology of the RHO zeolite. TPR, XPS and hydrogenation tests revealed that Pt particles were located in both RHO cages and intrazeolite spaces. In Pt/RHO containing lower levels of cesium, a small amount of Pt was also located on the external surface of the zeolite. The contribution of hydrogen spillover over hybrid Pt/RHO_H-Y zeolite catalysts was examined in naphthalene hydrogenation. Naphthalene conversion increased from 21% over a Pt/RHO catalyst to 91% over Pt/RHO diluted with H-Y zeolite, clearly demonstrating the positive effect of hydrogen spillover on the hydrogenation reaction. [Copyright &y& Elsevier]

Abstract: Pt supported on a carbon molecular sieve (Pt/CMS) was prepared by pyrolysis of polyfurfuryl alcohol containing pre-reduced Pt particles. The catalysts were characterized by hydrogen chemisorption, XRD, N2 adsorption/desorption and TEM. Hydrogen chemisorption showed that not all the Pt particles were exposed to H2 molecules. Oxidation treatment made Pt particles more accessible to H2. Catalyst activity was evaluated by hydrogenation of 1-hexene. Hydrogen spillover was demonstrated by diluting Pt/CMS with activated carbon or hydrogen type zeolite Y. The initial conversion of 1-hexene was increased from 86.5% to 98.5% and to 100% when Pt/CMS was diluted with activated carbon and hydrogen type zeolite, respectively. The high initial conversion was sustained for 6h in the presence of diluents while the conversion decreased quickly for Pt/CMS alone. [Copyright &y& Elsevier]