An 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 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 AbstractA 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 AbstractMicro-mesoporous aluminosilicates based on ZSM-5 zeolite, obtained by a dual template method, as well as in the presence of a dual-functional template (i.e. a Gemini-type surfactant), were tested in the oxidation of furfural with hydrogen peroxide. Even substantial changes in acidity and porosity of the catalysts result in minor variations of selectivity towards the desired products. Application of the synthesized zeolite-based materials in the oxidation of furfural with hydrogen peroxide leads to formation of 2(5H)-furanone (yield up to 28.5%) and succinic acid (up to 19.5%) as the main C4 reaction products. The kinetic model developed previously to treat the results for oxidation of furfural over sulfated zirconia was able to describe the data also for micro-mesoporous aluminosilicates.
Graphical AbstractRegularly dispersed Pt particles on SBA-15 supported catalysts were synthesized with a Pt loading of 5 wt% by a sol-immobilisation method, wherein various Pt particle sizes within 1–5 nm were finely controlled via the adjustment of the addition amount of polyvinyl alcohol (PVA). A high PVA/Pt ratio of the initial solution tended to generate small Pt particles on the SBA-15 support due to intense protection against Pt particle aggregation. In addition, the effect of Pt particle size on naphthalene hydrogenation was investigated in terms of catalytic performance. Compared with the performance of other catalysts with Pt particle sizes greater or less than 3.5 nm, Pt nanoparticles with sizes centered at 3.5 nm exhibited excellent catalytic performance towards decalin. This excellent catalytic performance was mainly attributed to a suitable ratio of the edge sites to flat sites on these Pt nanoparticles, benefitting the rapid adsorption of naphthalene and dissociation of hydrogen.
Graphical AbstractThe Pt/SBA-15 catalysts were prepared by sol-immobilisation method. The highest performance was attributed to the Pt-nanoparticles with suitable flat/edge sites ratio.
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 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 AbstractNi–Mo2C and Ni–WC were evaluated in dry reforming of methane employing different CH4/CO2 ratios. Ni–Mo2C remained active under an excess of CH4, but deactivation occurred under an excess of CO2. Ni–WC was resistant to excess of CO2 but showed carbon deposition under excess of CH4.
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 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 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 AbstractIn this research, four cholines supported on core–shell iron oxides, Fe2O3@MgO@Ch.OAc (choline acetate), Fe2O3@MgO@Ch.OH (choline hydroxide), Fe3O4@Ch.OAc, Fe3O4@Ch.OH, were synthesized. The synthesized catalysts were tested in 1,2,3-triazoles synthesis by the reaction of nitromethane, aldehyde, and benzyl azide in EtOH as a green solvent. Among four synthesized heterogeneous catalysts, the Fe2O3@MgO@ch.OAc showed superior catalytic activity for the reaction and afforded the desired triazoles in good isolated yields under mild reaction conditions.
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 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 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.
The 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 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 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 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 AbstractVanadium(IV) oxido complex of 1-Phenyl-1,3-butanedione [VIVO(bzac)2] (1) was prepared, characterized, and heterogenized onto APTMS modified graphene oxide, as well as imidazole modified polystyrene beads. Graphene oxide supported complex GO-APTMS-[VIVO(bzac)2] (2) and polymer anchored complex PS-im-[VIVO(bzac)2] (3) were used for the oxidative bromination of a number of small organic molecules and oxidation of a series of thioethers. Both 2 and 3 evolve as excellent heterogeneous catalysts. The nature of solid support does not impact substrate conversion (%) during the oxidative bromination of salicylaldehyde, phenol, or styrene, whereas it influences the substrate conversion (%) as well as the product selectivity (%) during the oxidation of thioethers.
Graphic Abstract