A monolithic complexed catalyst composed of a piece of Co foam decorated with Ru nanosheets has been fabricated. This catalyst has demonstrated excellent performance in catalyzing NaBH4 hydrolysis under alkaline conditions. Most importantly, the bulky size of the developed catalyst provides convenience to control the start and stop of hydrogen production by manipulating the attachment and detachment between the catalyst and NaBH4 solution. These features endow this catalyst with great potential for on-site hydrogen supply.
Graphic AbstractThe magic number clusters Au102(p-MBA)44 and Au144(p-MBA)60 were synthesized and tested for their ability to catalyze the reduction of 4-nitrophenol. Kinetic and thermodynamic analyses demonstrate that both clusters are effective catalysts with activation energies less than 10 kJ/mol and turnover frequencies approaching 103 h–1 per surface gold atom.
Graphic AbstractIn this study, we describe the synthetic of uranyl nitrate ion functionalized MOFs linked by carboxyl, which displays block shape crystals structure. The as-prepared uranyl-MOF has been efficiently utilized as heterogeneous catalyst for selective aerobic oxidation of sulfides under visible-light irradiation. Photochemistry of extended MOFs including uranyl nitrate ion has been examined. The sulfoxidation reaction proceeds with good yields for a large variety of different sulfides. This process is carried out under visible light conditions, methanol as single solvent, and the uranyl-MOF material can be recycled up to five times. Sulfoxidation reaction mainly proceeds through an electron and energy transfer mechanism of oxygen in uranyl nitrate ion.
Graphic AbstractIn this study, we describe the synthetic of uranyl nitrate ion functionalized MOFs. The as-prepared uranyl-MOF was efficiently utilized as heterogeneous catalyst for selective aerobic oxidation of sulfides under visible-light irradiation. Photochemistry of extended MOFs including uranyl nitrate ion has been examined.
In this paper, we have produced carboxylic acids by the oxidation of various alcohols in the presence of CO2 using SBA-15/IL supported Cu(II) (SBA-15/IL/Cu(II)) as nanocatalyst. The obtained products showed to have excellent yields by taking into account of SBA-15/IL/Cu(II) nanocatalyst. In addition, the analysis of EDX, SEM, TGA, TEM, XPS, and FT-IR showed the heterogeneous structure of SBA-15/IL/Cu (II) catalyst. It is determined that, after using SBA-15 excess, the catalytic stability of the system was enhanced. Moreover, hot filtration provided a full vision in the heterogeneous catalyst nature. The recycling as well as reuse of the catalyst were studied in cases of coupling reactions many times. Moreover, we have studied the mechanism of the coupling reactions.
Graphic AbstractAPO-11 aluminophosphate molecular sieve was prepared by hydrothermal method of aluminum hydroxide with diisopropylamine. Ni–P/APO-11 amorphous alloy catalysts were prepared by chemical reduction method and used for the hydrogenation of α-pinene reaction. The catalysts were characterized by X-Ray photoelectron spectroscopy (XPS), Nitrogen adsorption–desorption isotherms (BET), scanning electron microscope (SEM), transmission electron microscope (TEM) and fourier transform infrared spectrometer (FT-IR).The prepared conditions of the Ni–P/APO-11 catalysts played important roles on the hydrogenation of α-pinene reaction. It was found that the preparation temperature, P/Ni molar ratio and pH value had great influence on the reduction dosage, dispersion and particle sizes of the catalysts, thus affecting the reactivity of the catalysts. The appropriate reaction conditions explored were at 30 °C, n(P/Ni)?=?5 and pH?=?8, obtaining a 90.65% conversion of α-pinene and 97.87% selectivity to cis-pinane. Under these conditions, the catalysts exhibited better repeatability and stability.
Graphic AbstractIn this study, the porous ultrathin graphitic carbon nitride (CN) nanosheets with rich C and nitrogen defects were prepared by one-step calcining the mixture of melamine and glucose (Glu) in air atmosphere (Glu-CN). Introducing simultaneously rich C atoms and nitrogen defects into CN structures continuously modulates the bandgaps from 2.67 to 1.81 eV of CN photocatalysts. Due to large surface area, more active sites, remarkably longer lifetime of charge carriers and adjustable band gap structure, the prepared ultrathin porous CN nanosheets show the enhanced photocatalytic performance for the degradation of methyl orange (MO) under visible light. The degradation efficiency of optimal CN nanosheet photocatalyst for MO is 5.75 times that of bulk CN. This work provides a facile and universal relevance approach to engineer the band structures of CN by introduction of rich C and porous morphology for high-performance photocatalytic, which can provide informative principles for the design of efficient photocatalysis systems for solar energy conversion.
Graphic AbstractAlthough numerous efforts have been made in direct syngas conversion to higher alcohols via Fischer–Tropsch synthesis, the higher alcohols distribution remains a challenge. Here, we introduce alkaline earth metal oxide as promoter into activated carbon supported cobalt catalyst to tune distribution of higher alcohols. With the addition of Mg, the distribution of C2-5 alcohols increase from 41.2 to 75.8% accompanying with distribution of C6-18 alcohols decrease from 52.8 to 14.0%. Ba-promoted Co based catalyst (CoBa/AC) presents similar alcohols distribution to un-promoted catalyst, while the alcohol selectivity over CoBa/AC is higher than Co/AC. For promoted catalysts, the distribution of C6-18 alcohols increased in the order of Mg?<?Ca?<?Sr?<?Ba. The characterization results exhibit that the promoter addition facilitates the cobalt carbide formation, which leads to enhancement of selectivity to higher alcohols. The available active cobalt sites of promoted Co based catalysts increase in the same above order of Mg?<?Ca?<?Sr?<?Ba.
Graphic AbstractSolid base metal oxide catalysts such as MgO offer utility in a wide variety of syntheses from pharmaceuticals to fuels. The (111) facet of MgO shows enhanced, unique properties relative to the other facets. Carbon coatings have emerged as a promising modification to impart metal oxide catalyst stability. Here, we report the synthesis, characterization, and catalytic properties of commercial MgO, MgO(111), and carbon coated derivatives thereof for 2-pentanone condensation. The dimer and trimer products of this reaction can be used as precursors for biofuels upon oxygen removal and thus have relevance in environmental sustainability. MgO(111) maintained impressive selectivity towards the dimer product after carbon coating, whereas the other catalysts experienced a decrease in conversion and selectivity as a consequence of the carbon coating. Our findings highlight the catalytic efficacy of MgO(111), provide insight into carbon coating for catalyst stability, and pave the way for continued mechanistic investigations.
Graphical AbstractAn efficient solvent-free catalyst system for hydrosilylation of aldehydes and ketones was developed based on iron pre-catalyst Fe2(CO)9/C6H4-o-(NCH2PPh2)2BH. The reactions were tolerant of many functional groups and the corresponding alcohols were isolated in good to excellent yields following basic hydrolysis of the reaction products. The reaction is likely catalyzed by an in situ generated pincer ligated iron hydride complex.
Graphic AbstractIn order to further improve the catalytic activity and stability of heterogeneous acid catalysts, a polystyrene microspheres modified sulfonic acid-based catalyst (PS-SO3H) was prepared. PS-SO3H was characterized by Fourier transform infrared spectroscopy, powder X-ray diffraction, scanning electron microscope, transmission electron microscope, N2 adsorption–desorption, and X-ray photoelectron spectroscopy. Catalytic efficiency was determined using the reaction of furfuryl alcoholysis to ethyl levulinate (EL). The obtained results showed that PS-SO3H had excellent catalytic performance, with EL yield of 94.7%. In addition, PS-SO3H was easily separated from the reaction system and recycled multiple times without significant reduction in activity. High catalytic activity stemmed from the effect of Brønsted acid sites and appropriate structural properties.
Graphical AbstractIn this work, density functional theory is used to study the mechanism of propane dehydrogenation over non-metallic C3N catalyst. The structure, electrostatic potential and density of state of C3N are introduced, as well as the adsorption of reactants on catalyst is studied. The propane dehydrogenation reaction is divided into the first dehydrogenation and the second dehydrogenation (deep dehydrogenation). We explore the possible dehydrogenation pathways in two-step dehydrogenation. The rate control step of the first dehydrogenation is the removal of methylene hydrogen atom from propane, and its energy barrier is 47.79 kcal/mol, which reflected the catalytic activity of the catalyst. The rate control step of deep dehydrogenation is the process of removing the first hydrogen atom of the product propylene to produce the by-product. The energy barrier is 72.80 kcal/mol, which is much larger than that of the first step of dehydrogenation, reflecting the excellent selectivity of the catalyst.
Graphic AbstractLignocellulosic biofuels are the most promising sustainable fuels for supplementing shrinking fossil resources. In this work, acid-modified vermiculite (AVM)-supported Pd–Ni bimetallic catalyst (Pd–Ni/AVM) was investigated for the hydrodeoxygenation of bio-oil and its model compounds to assess its reactivity. Pd–Ni/AVM was found to efficiently hydrodeoxygenate the investigated model compound (phenol). The phenol conversion reached 94% at 0.5% of Ni loading and temperatures beyond 513 K. Using these parameters, the phenolic hydroxyl group was removed, and the C?=?C bonds were saturated. This catalyst was also efficient in the hydrodeoxygenation of bio-oil. H2-TPR experiments elucidated the synergistic effects between the active component and the carrier, which were considered the main reason for the catalytic activity. Strong influences of the Ni loading and temperature on the hydrogenation of phenol were also observed when the Pd loading was fixed at 1 wt%.
Graphic AbstractThe efficient SBA-15 supported silver catalysts(Ag/SBA-15) were prepared and characterized by ICP-OES, XRD, TEM, SEM, XPS and N2 adsorption–desorption techniques. The catalysts exhibited an excellent catalytic activity for the aerobic oxidation of toluene to benzaldehyde under solvent-free conditions. Conversion of toluene and selectivity of benzaldehyde were 50% and 89% respectively over catalyst with 9.1 wt% Ag loading (10Ag/SBA-15). A wide range of substrates were tolerated under the selected reaction conditions. The kinetic study shows that the oxidation of toluene over 10Ag/SBA-15 is pseudo-first-order reaction and the activation energy Ea is 45.1 kJ/mol. A plausible mechanism involving oxygen free radicals was proposed for the aerobic oxidation reaction. Compared with the traditional method, the newly designed heterogeneous catalytic system shows better economic applicability, environmental friendliness and broader application prospects.
Graphical abstractThis work proposed a new path to synthesize Ni-phyllosilicate through the reaction of nickel hydroxide and silica sol on the surface of Ni-foam to form the monolithic Ni-phyllosilicate/Ni-foam catalyst. Ni-phyllosilicate could reprint the morphology of nickel hydroxid and firmly anchor on the framework of Ni-foam, which obtained fine Ni particles of 2.8 nm after reduction in H2 at 650 °C, resulting in high catalytic activity for CO2 methanation. In addition, the Ni-phyllosilicate/Ni-foam catalyst showed high long-term stability in a 100 h-lifetime test owing to the combined effects of surface confinement of Ni-phyllosilicate, firm anchoring between Ni-phyllosilicate and Ni-foam, as well as the high heat transfer property of Ni-foam.
Graphical AbstractFurfurylamine is an important furfural-upgrading biobased chemical for the production of pharmaceuticals, biofuels, fibers, additives, polymers, etc. In one-pot reaction system, biomass was tandemly catalyzed to furfurylamine with aluminium-based alkaline-treated graphite (Al-AG) catalyst and recombinant ω-transaminase biocatalyst. Al-AG (3.6 wt%) catalyzed corncob (75.0 g/L) to 110.0 mM furfural at 56.8% yield (based on xylan in corncob) in γ-valerolactone–water (1:4, v:v; pH 1.0) for 40 min at 180 °C. The pH-adjusted corncob-slurry (pH 7.5) containing furfural were catalyzed to furfurylamine at high yield with γ-valerolactone-tolerant Aspergillus terreus ω-transaminase biocatalyst at 35 °C using isopropylamine (3 mol isopropylamine/mol furfural) as amine donor. Such an efficient and sustainable approach for catalytic conversion of biomass to high-value-added biobased furfurylamine was successfully established in tandem reaction with Al-AG and ω-transaminase biocatalyst.
Graphic AbstractCu-SSZ-13 catalysts were synthesized with Si: Al?=?4.5 and 25, to obtain materials with isolated Cu2+ and [CuOH]1+ sites, respectively. The catalysts were tested for the selective catalytic reduction of NOx (SCR), NO oxidation and NH3 oxidation. Cu2+ sites presented the highest NO rates and lowest NH3 rates, as the temperature was increased from 300 °C to 650 °C, during SCR and NH3 oxidation, respectively. None of the Cu-SSZ-13 catalysts presented activity for NO oxidation, consistent with the absence of copper oxide clusters. In addition, catalysts composed by mechanical mixtures of Cu-SSZ-13?+?Fe-SSZ-13 with Si: Al?=?4.5 and 25 were tested for SCR, NO oxidation and NH3 oxidation, to study the effect of the presence of iron together with Cu-SSZ-13 for improving its SCR working temperature range. Higher reaction rates for NO oxidation and NH3 oxidation over Cu-SSZ-13?+?Fe-SSZ-13 showed a more relevancy of side reactions that makes a combined effect of Fe-SSZ-13 and Cu-SSZ-13 not a real improvement in high temperature SCR.
Graphic AbstractThe reaction network of oxidative carbonylation of methanol (CH3OH) over CuY catalyst prepared by solid-state ion exchange of HY zeolite with CuCl was enriched by combination of in-situ diffuse reflectance infrared fourier transform spectroscopy and mass spectrometric. Based on the proposed mechanism of dimethyl carbonate formation on CuY in literature, this study mainly focused on the origin of the O atom in methoxyl and the reaction pathway for by-products formation. The interaction of the catalyst with different reactants and reactant mixtures (CH3OH, CH318OH, HCHO, O2, CH3OH/HCHO and CH318OH/CO/O2) was studied in detail. It was found that in the presence of CuOx or oxygen, methoxide species are generated by breaking of the O–H bond. Reaction of methoxide species with oxygen leads to the formation of formaldehyde (HCHO), followed by the generation of formate species through consecutive oxidation of HCHO.
Graphic AbstractIn this study, g-C3N4-TiO2 nanocomposite structure has been loaded with Co3O4 via electroless plating and thermal annealing to form Co3O4@g-C3N4-TiO2 catalyst material for H2 generation from NaBH4 hydrolysis. The material characterizations of the fabricated catalyst have been performed before and after exposure to an aqueous NaBH4 solution to understand the changes in catalytic performance and material properties. The Arrhenius activation energies have been determined to be 58 kJ mol?1. The hydrogen generation rates have been observed as 180 and 1200 mL min?1 gcat?1 for the catalyst hydrolysis of NaBH4 at 30 °C and 60 °C, respectively. The catalytic activity performed in NaBH4 solution exhibited good reusability.
Graphical AbstractBeta-zeolite supported ruthenium catalysts for reductive amination of 5-hydroxymethyl-2-furaldehyde (HMF) with an aqueous solution of ammonia (NH3 aq.) and molecular hydrogen (H2) are examined to synthesize the corresponding primary amine of 5-aminomethyl-2-furylmethanol (FAA). Various SiO2/Al2O3 (Si/2Al) ratios of the beta-zeolite support were used to prepare the Ru-based catalysts. It was observed that the Si/2Al ratio was contributed to the catalytic activity, and the Si/2Al?=?150 of beta-zeolite was found to be the most active for Ru catalyzed reductive amination of HMF, affording ca. 70% yield. Characterization techniques were taken to analysis the factors that influence the reactivity of catalysts, and which revealed that not only the ruthenium nanoparticle size but also the ratio of RuO2 against metallic Ru species were crucial factors for the reactivity of reductive amination of HMF to FAA.
Graphical AbstractHeterogeneous catalysts based on metallic nanoparticles are promising candidates for wastewater treatment. However, they aggregate easily as a result of their high surface energy. Polymers are very popular supporting catalyst materials because they can stabilize the metallic nanoparticles to prevent aggregation. In this study, aniline-pentamer-based electroactive polyurea (EPU) was synthesized by oxidative coupling, and Au nanoparticles were anchored to the EPU via its aniline segments. Electrochemical redox behavior of the as-synthesized EPU was monitored by electrochemical cyclic voltammetry. The Au/EPU composite was characterized by FTIR, UV–vis, TGA, SEM, TEM, XRD XPS, and ICP-OES. SEM showed that the EPU had a flower-like structure, and the Au nanoparticles were uniformly immobilized on the EPU surface. The reduction of 4-nitrophenol (4-NP) by NaBH4 was used as a model reaction to evaluate the catalytic properties of the Au/EPU composite. Moreover, the optimization of the reaction conditions for the reduction of 4-NP to 4-aminophenol (4-AP) were also studied in detail. The Au/EPU composite catalyzed the reduction of 4-NP to 4-AP within 4 min with a rate constant of 2.4?×?10–2 s?1 and an activation energy of 40.17 kJ/mol. The Au/EPU composite demonstrated high conversion (98%) after 20 successive cycles.
Graphical abstract