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 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 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 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 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 AbstractLaBO3 (B?=?Fe, Mn, and FeMn) perovskite-type oxides were prepared by sol–gel method and then used as catalysts in CO hydrogenation for light olefins. The catalysts were characterized using XRD, H2-TPR, SEM, CO (CO2)-TPD, and XPS. The results showed that the lattice oxygen migration and oxygen vacancies promoted oxygen mobility by doping Mn2+ at the B site, Moreover, the presence of manganese as a promoter in the catalyst increased olefin selectivity compared with the olefin selectivity of the catalyst containing iron at the B-site and exhibited resistance to carbon deposition; while reducing the metal elements. In CO hydrogenation, potassium-promoted LaFeMnO3 catalysts afforded high catalytic activity and C2=–C4= selectivity. An O/P value of 5.0 and a C2=–C4= fraction of 54% were achieved for all hydrocarbons with low methane selectivity.
Graphic AbstractCuO–CeO2 (Cu–Ce) catalyst with a CuO/CeO2 mass ratio of 1 prepared by a sol–gel method is used in the CO catalytic oxidation reaction in the actual industrial sulfur-containing atmosphere. At a reaction temperature of 200 °C, the catalyst exhibits quite different stability under sulfur-containing and sulfur-free conditions. When 30 ppm SO2 was added to the feed gas, the Cu–Ce catalyst had an initial CO conversion rate of 100%, gradually decreasing after 26 h, and this catalyst completely deactivated at about 50 h. However, the CO conversion rate of the catalyst under sulfur-free conditions could be nearly maintained at 100% within the measured time range (60 h). The results of IR, Raman, and XPS characterizations proved that the accumulation of cerium sulfate on the Cu–Ce catalyst would cover the active sites of the catalyst, eventually leading to the complete deactivation of the catalyst, which provides favorable evidence for the actual industrial anti-sulfur application.
Graphical AbstractThe statistical selectivity models were developed for four different Fischer–Tropsch synthesis product range, including methane (CH4), light olefins (C2=C4), light paraffins (C2–C4), and long-chain hydrocarbons (C5+), based on the experimental data obtained over thirteen γ-Al2O3 supported cobalt-based catalysts with different cobalt particle and pore sizes. The input variables consist of cobalt metal particle size and catalyst pore size. The cubic and quadratic polynomial equations were fitted to the experimental data, however, the mathematical models were subjected to model reduction for the enhancement of model adequacy, which was investigated through ANOVA. The multi-objective optimization revealed that the maximum C5+?selectivity (84.150%) could be achieved at the cobalt particle size and pore sizes of 14.764 and 23.129 nm, respectively, while keeping the selectivity to other hydrocarbon products minimum.
Graphic Abstract0D/2D Pt-C3N4/CdS heterojunction photocatalyst were fabricated with CdS quantum dots interspersed on g-C3N4 nanosheets via successive ionic layer absorption process. The obtained Pt-C3N4/CdS Z-scheme heterojunction with Pt cocatalyst deposited on g-C3N4 nanosheets exhibited H2 production rate of 35.3 mmol g?1 h?1, which is 3.1 times higher than that of Pt-CdS/C3N4. The enhanced photocatalytic activity are attributed to the Z-scheme charge carrier transfer mechanism with stronger redox ability. The photocatalytic mechanism of the CdS/g-C3N4 composite is investigated and demonstrated in this work. It may provide unique insights to design 0D/2D Z-scheme heterojunction photocatalyst systems using a facile method for highly efficient H2 production.
Graphic AbstractSchematic illustration of charge transfer modulated by the metal cocatalyst selective deposition on heterojunction-type II (a) and direct Z-Scheme mechanisms (b) over the C3N4/CdS heterostructure composites under visible light irradiation.
Lignocellulosic 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 Abstractg-C3N4 has received much attention due to its role in photocatalytic hydrogen evolution and contaminants degradation. Nevertheless, the photocatalytic property of bulk g-C3N4 (BCN) is seriously restricted owing to its short photo-generated carrier lifetime, small specific surface area and low visible light utilization rate, etc. In this study, nanosheet constructing and heteroatom phosphorus (P) doping, as two important strategies, are synergistically adopted to co-enhance its activity. The controllable P atoms were successfully doped into the framework of g-C3N4 nanosheet (NCN-P) through forming P-N bond. The optimized NCN-P sample displays an excellent H2 production rate (3263.99 µmol·g?1·h?1) under white LED light irradiation, which is more than 11.6 times that of the BCN. Moreover, it also exhibits excellent photocatalytic degradation ratio of tetracycline reached 80% in 1 h. Furthermore, the optimized NCN-P sample still maintains robust photocatalytic performance after recycling tests, making it as a bright prospect photocatalyst for solar energy utilization and contaminants removal.
Graphic AbstractAchieving the removal of the toxic nitric oxide (NO) gas efficiently and cheaply has always been a challenge. Herein, we systematically investigate the reduction mechanisms of NO on the surface of the Fe–PCs (PCs?=?phthalocyanines) using density functional theory calculations. The isolated iron atom not only plays the role of an adsorption and activation site for the NO molecule but also works as an electron transfer medium in the whole reaction process. The results indicate that the catalytic reduction of NO to N2 takes place through a continuous two-step pathway. The first step involves the reduction of NO to N2O through a competitive Langmuir–Hinshelwood and Eley–Rideal mechanisms with the energy barrier of 1.19 eV and 0.60 eV, respectively. The second step involves the reduction of N2O to N2 with an energy barrier of 0.91 eV. These reaction pathways are favorable thermodynamically, thus the Fe–PCs catalyst is a promising candidate for the abatement of NO gases.
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 AbstractIn 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 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 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 AbstractZSM-48 and ZSM-22 zeolites with similar Si/Al ratio were synthesized and modified by alkali treatment. Moreover, n-dodecane hydroisomerization performance of Pt supported ZSM-22 and ZSM-48 were investigated. The catalytic results showed that the activity and the isomers selectivity of n-dodecane hydroisomerization could be improved by alkali treatment. The isomers distributions were distinct for Pt/ZSM-48 and Pt/ZSM-22. Mono-branched isomers near the end of the chains were more prone to be generated on Pt/ZSM-22 catalyst, which suggested “pore-mouth” catalysis model dominating the hydroisomerization catalysis. However, di-branched isomers and mono-branched isomers with methyl near the middle of the carbon chains were favorable to be formed over Pt/ZSM-48 catalyst according to the “key-lock” catalysis model. Moreover, more central-branched isomers were formed at high reaction temperature (>?320 °C) especially for Pt/ HZSM-22.
Graphic AbstractIn the development of photocatalytic processes towards waste water treatment, we have been long faced three foremost obstacles, including catalyst mass production, photon-energy cost and finally catalyst separation process after the treatment. In this study, such problems were addressed through the development of samarium and cerium-doped BiFeO3 (BFO) nanoparticles (NPs) (BixRExFeO3; RE?=?Sm, Ce, x?=?0.00, 0.01, 0.03, 0.05;) employing a rapid solution combustion synthesis (SCS). This technique is greatly capable of large scale nanopowder production at low temperature. In the SCS procedure, different amount of oxidant-to-fuel (glycine-to-nitrate ion, Gly/NO3?) were investigated (Gly/NO3??=?0.2, 0.3, 0.37, 0.56, and 0.8). Moreover, a catalytic sunlight irradiation was employed to study the effect of Sm and Ce dopant contents on the photodegradation of benzene and methyl orange (MO) in the aqueous solution. The as-synthesized catalysts were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), UV–Visible diffuse reflectance spectroscopy (UV–Vis DRS) and Brunauer–Emmett–Teller (BET)/Barrett-Joyner Halenda (BJH) techniques. The band gap energy of BFO decreaed from 2.14 to 2.06 eV with the increase of Sm3+ contents while it increased up to 2.22 eV in the case of Ce-doped BFO. The solar decomposition of the organic pollutants demonstrated the superior performance of Bi1-xSmxFeO3 photocatalyst rather than using cerium in the BFO crystalline structure which is attributed to the increased surface area and visible light harvesting.
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 Abstract