苯甲酸催化加氢合成环己基甲酸的研究

采用绿色合成法,在水相条件下,在Pd/C催化剂的作用下用苯甲酸催化氢化合成环己基甲酸。通过一系列的实验,得到了较好的合成环己基甲酸的工艺条件,在该条件下,能够得到比较纯的产物和较好的产物收率。

Self-assembled S-scheme In_(2.77)S_(4)/K^(+)-doped g-C_(3)N_(4)photocatalyst with selective O_(2) reduction pathway for efficient H_(2)O_(2) production using water and air

The development of an efficient artificial H_(2)O_(2) photosynthesis system is a challenging work using H_(2)O and O_(2) as starting materials.Herein,3D In_(2.77)S_(4) nanoflower precursor was in-situ deposited on K^(+)-doped g-C_(3)N_(4)(KCN)nanosheets using a solvothermal method,then In_(2.77)S_(4)/KCN(IS/KCN)het-erojunction with an intimate interface was obtained after a calcination process.The investigation shows that the photocatalytic H_(2)O_(2) production rate of 50IS/KCN can reach up to 1.36 mmol g^(-1)h^(-1)without any sacrificial reagents under visible light irradiation,which is 9.2 times and 4.1 times higher than that of KCN and In_(2.77)S_(4)/respectively.The enhanced activity of the above composite can be mainly attributed to the S-scheme charge transfer route between KCN and In_(2.77)S_(4) according to density functional theory calculations,electron paramagnetic resonance and free radical capture tests,leading to an expanded light response range and rapid charge separation at their interface,as well as preserving the active electrons and holes for H_(2)O_(2) production.Besides,the unique 3D nanostructure and surface hydrophobicity of IS/KCN facilitate the diffusion and transportation of O_(2) around the active centers,the energy barriers of O_(2) protonation and H_(2)O_(2) desorption steps are ef-fectively reduced over the composite.In addition,this system also exhibits excellent light harvesting ability and stability.This work provides a potential strategy to explore a sustainable H_(2)O_(2) photo-synthesis pathway through the design of heterojunctions with intimate interfaces and desired reac-tion thermodynamics and kinetics.

Preparation of Fe-Mn/K/Al2O3 Fischer-Tropsch Catalyst and Its Catalytic Kinetics for the Hydrogenation of Carbon Monoxide

A K promoted iron-manganese catalyst was prepared by sol-gel method,and subsequently was tested for hydrogenation of carbon monoxide to light olefins.The kinetic experiments on a well-characterized Fe-Mn/K/Al2O3 catalyst were performed in a fixed-bed micro-reactor in a temperature range of 280-380 ℃,pressure range of 0.1-1.2 MPa,H2/CO feed molar ratio range of 1-2.1 and a space velocity range of 2000-7200 h-1.Considering the mechanism of the process and Langmuir-Hinshelwood-Hogan-Watson（LHHW） approach,unassisted CO dissociation and H-assisted CO dissociation mechanisms were defined.The best models were obtained using non-linear regression analysis and Levenberg-Marquardt algorithm.Consequently,4 models were considered as the preferred models based on the carbide mechanism.Finally,a model was proposed as a best model that assumed the following kinetically relevant steps in the iron-Fischer-Tropsch（FT） synthesis：（1） CO dissociation occurred without hydrogen interaction and was not a rate-limiting step;（2） the first hydrogen addition to surface carbon was the rate-determining steps.The activation energy and adsorption enthalpy were calculated 40.0 and -30.2 kJ.mol-1,respectively.

Promotional effects of Sb on Pd-based catalysts for the direct synthesis of hydrogen peroxide at ambient pressure

TiO2‐supported Pd‐Sb bimetallic catalysts were prepared and evaluated for the direct synthesis of H2O2 at ambient pressure.The addition of Sb to Pd significantly enhanced catalytic performance,and a Pd50Sb catalyst showed the greatest selectivity of up to 73%.Sb promoted the dispersion of Pd on TiO2,as evidenced by transmission electron microscopy and X‐ray diffraction.X‐ray photoelectron spectroscopy indicated that the oxidation of Pd was suppressed by Sb.In addition,Sb2O3 layers were formed and partially wrapped the surfaces of Pd catalysts,thus suppressing the activation of H2 and subsequent hydrogenation of H2O2.In situ diffuse reflection infrared Fourier transform spectroscopy for CO adsorption suggested that Sb homogenously located on the surface of Pd‐Sb catalysts and isolated contiguous Pd sites,resulting in the rise of the ratio of Pd monomer sites that are favorable for H2O2 formation.As a result,the Sb modified Pd surfaces significantly enhanced the non‐dissociative activation of O2 and H2O2 selectivity.

Strategies on improving the electrocatalytic hydrogen evolution performances of metal phosphides

Among the sustainable energy sources,hydrogen is the one most promising for alleviating the pollution issues related to the usage of conventional fuels,as it can be produced in an efficient and eco-friendly way via electrocatalytic water splitting.The hydrogen evolution reaction(HER,a half-reaction of water splitting)plays a pivotal role in decreasing the price and increasing the catalytic efficiency of hydrogen production and is efficiently promoted by metal phosphides in different electrolytes.Herein,we summarize the recent advances in the development of metal phosphides as HER electrocatalysts,focus on their synthesis(post-treatment,in situ generation,and electrodeposition methods)and the enhancement of their electrocatalytic activity(via elemental doping,interface and vacancy engineering,construction of specific supports and nanostructures,and the design of bior polymetallic phosphides),and highlight the crucial issues and challenges of future development.

Prospect of vapor phase catalytic H2O2 production by oxidation of water

Vapor phase catalytic hydrogen peroxide production by oxidation of water is possible by coupling the reaction with oxidation of an organic sacrificial reductant. It is potentially a safer process than direct synthesis from H2 and O2. Based on mechanistic information available mostly for liquid phase catalytic processes, feasible reaction mechanisms for such coupled reactions are proposed based on which desirable catalyst properties are identified. It is found that the surface-adsorbed oxygen bond is an important parameter for identifying desirable catalysts. Thermodynamics can be used to identify the types of organic oxidation reactions that can couple with water oxidation such that H2O2 formation becomes thermodynamically favorable. Reactions such as epoxidation of alkenes and selective oxidation of alkanes to alcohols cannot provide sufficient thermodynamic driving force, whereas oxidation of alcohols to aldehydes and to acids can. Finally, further research is suggested to identify catalytic properties important for H2O2 decomposition and for coupling selective oxidation of organic compounds to oxidation of H2O in order to facilitate development of H2O2 production coupled with selective organic oxidation.

Reverse Microemulsion Synthesis and Characterization of Pd-Ag Bimetallic Alloy Catalysts Supported on Al_2O_3 for Acetylene Hydrogenation

Pd-Ag bimetallic alloy nanoparticles were synthesized by the reverse microemulsion method, and then deposited on A1203 to form the supported catalyst. The nanoparticles of Pd-Ag and Pd-Ag/AI203 samples were characterized by UV/ Vis, HRTEM, EDX, XRD, and XPS. The test results indicated that Pd-Ag bimetallic alloy nanoparticles with a size of about 2 nm and a face-centered cubic （fcc） structure were formed in the measured area of microemulsion. The growth of nanopar- ticles was effectively limited within the droplet of micoremulsion. TEM image exhibited that the Pd-Ag alloy nanoparticles were well-dispersed on the A1203 support. The catalytic performance of various catalysts for selective hydrogenation of acetylene showed that a higher acetylene conversion and selectivity to ethylene upon acetylene hydrogenation was achieved on a nano-sized Pd-Ag bimetallic catalyst with a Pd/Ag alloy supported molar ratio of 1：1.5.

Preparation of N‐vacancy‐doped g‐C_3N_4 with outstanding photocatalytic H_2O_2 production ability by dielectric barrier discharge plasma treatment

Dielectric barrier discharge（DBD） plasma is considered to be a promising method to synthesize solid catalysts. In this work, DBD plasma was used to synthesize a nitrogen‐vacancy‐doped g‐C3N4 catalyst in situ for the first time. X‐ray diffraction, N2 adsorption, ultraviolet–visible spectroscopy, scanning electron microscopy, transmission electron microscopy, X‐ray photoelectron spectrosco‐py, electrochemical impedance spectroscopy, electron paramagnetic resonance, O2 tempera‐ture‐programmed desorption, and photoluminescence were used to characterize the obtained cat‐alysts. The photocatalytic H2O2 production ability of the as‐prepared catalyst was investigated. The results show that plasma treatment influences the morphology, structure, and optical properties of the as‐prepared catalyst. Nitrogen vacancies are active centers, which can adsorb reactant oxygen molecules, trap photoelectrons, and promote the transfer of photoelectrons from the catalyst to the adsorbed oxygen molecules for the subsequent reduction reaction. This work provides a new strat‐egy for synthesizing g‐C3N4‐based catalysts.

Sustainable synthesis of supported metal nanocatalysts for electrochemical hydrogen evolution

Among the various types of heterogeneous catalysts,supported metal nanocatalysts(SMNCs)have attracted widespread interest in chemistry and materials science,due to their advantageous features,such as high efficiency,stability,and reusability for catalytic reactions.However,to obtain well-defined SMNCs and inhibit nanoparticle aggregation,traditional approaches generally involve numerous organic reagents,complex steps,and specialized equipment,thus hindering the practical and large-scale synthesis of SMNCs.In this review,we summarize green and sustainable synthetic methodologies for the assembly of SMNCs,including low temperature pyrolysis and solid-state,surfactant-and reductant-free,and ionic liquid assisted syntheses.The conventional application of SMNCs for electrochemical hydrogen evolution and the corresponding achievements are subsequently discussed.Finally,future perspectives toward the sustainable production of SMNCs are presented.

Synthesis of Silica-Dispersed NiMo Hydrodesulfurization Catalysts

Silica-dispersed NiMo hydrodesulfurization catalysts were synthesized by the deposition-precipitation method. For comparative purposes, bulk NiMo catalysts were obtained by co-precipitation. The silica-dispersed NiMo catalyst had highly active metals content. Silica was employed to disperse active metals for full utilization of active components. The BET analysis showed that the silica-dispersed NiMo catalysts had a high surface area （147.0 m2/g） and pore volume （0.27 mL/g）, whereas the bulk NiMo catalysts exhibited a very low surface area （87.5 m2/g）. Transmission electron microscopy results proved that the active components were dispersed on the SiO2 substrate. X-ray diffraction patterns of the silicadispersed NiMo catalyst and the bulk NiMo catalyst were indexed to NiMoO4. The hydrodesulfurization activity of silicadispersed NiMo catalysts was much higher than that of reference catalysts and could be up to twice greater than those of commercial NiMo alumina-supported systems per gram of catalyst. The activity testing results also demonstrated that the silica-dispersed NiMo catalyst was an effective hydrodesulflarization catalyst.

Synthesis of Pt nanocatalysts for selective hydrogenation of ortho-halogenated nitrobenzene

Monodisperse Pt nanoparticles(NPs) were prepared by reduction of platinum acetylacetonate in octadecene with the presence of Fe(CO)5. The synthesized nanocatalysts presented high activity and selectively for hydrogenation of ortho-halogenated nitrobenzene to the corresponding ortho-halogenated aniline under mild reaction conditions.

Green synthesis of NiFe LDH/Ni foam at room temperature for highly efficient electrocatalytic oxygen evolution reaction

Clean energy technologies such as water splitting and fuel cells have been intensively pursued in the last decade for their free pollution. However, there is plenty of fossil energy consumed in the preparation of the catalysts,which results in a heavy pollution. Therefore, it is much desired but challenging to fabricate high-efficiency catalysts without extra energy input. Herein, we used a facile one-pot room-temperature method to synthesize a highly efficient electrocatalyst of nickel iron layered double hydroxide grown on Ni foam(NiFe LDH/NF) for oxygen evolution reaction(OER). The formation of the NiFe LDH follows a dissolutionprecipitation process, in which the acid conditions by hydrolysis of Fe^3+ combined with NO3^- could etch the NF to form Ni^2+. Then, the obtained Ni^2+ was co-precipitated with the hydrolysed Fe^3+ to in situ generate NiFe LDH on the NF. The NiFe LDH/NF exhibits excellent OER performance with a low potential of about 1.411 V vs. reversible hydrogen electrode(RHE) at a current density of 10 m A cm^-2, a small Tafel slope of 42.3 mV dec^-1 and a significantly low potential of ~1.452 V vs. RHE at 100 mA cm^-2 in 1 mol L^-1 KOH. Moreover, the material also keeps its original morphology and structure over 20 h. This energy-efficient strategy to synthesize NiFe LDH is highly promising for widespread application in OER catalyst industry.

CsOH catalyzed aerobic oxidative synthesis of p-quinols from multi-alkyl phenols under mild conditions

p-Quinols are ubiquitous structural motifs of various natural products and pharmaceutical compounds,and versatile building blocks in synthetic chemistry.The reported methods for the synthesis of p-quinol require stoichiometric amounts of oxidants.Molecular oxygen is considered as an ideal oxidant due to its natural,inexpensive,and environmentally friendly characteristics.During the ongoing research of C–H bond hydroxylation,we found that multi-alkyl phenols could react with molecular oxygen under mild conditions.Herein,we describe an efficient oxidative de-aromatization of multi-alkyl phenols to p-quinols.1 atm of molecular oxygen was used as the oxidant.Many multi-alkyl phenols could react smoothly at room temperature.Isotopic labeling experiment was also performed,and the result proved that the oxygen atom in the produced hydroxyl group is from molecular oxygen.

Syntheses of amides via iodine-catalyzed multiple sp3 C-H bonds oxidation of methylarenes and sequential coupling with N,N-dialkylformamides

The oxidative coupling of methylarenes and N,N-dialkylformamides was developed, and the appropriate reaction conditions were established. By using I2 as the catalyst, and tert-butyl hydroperoxide(TBHP) as the oxidant, the reaction provided N,N-dialkylamides or N-alkylamides with moderate yields via multiple sp3 C-H bonds activation of methylarenes in aqueous and metal-free conditions.