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Recent work has demonstrated that, for bimetallic Au–Pd systems, the rate of catalytic alcohol and formyl dehydrogenation (DH) is intrinsically linked to the rate of oxygen reduction (ORR) within the same system.

Processes for the isomerization of light alkanes have been commercialized, however, the isomerization of paraffins (CnH2n+2, n ≥ 7) remains a challenge. On mesoporous WZrOx supported Pt catalysts (...

In oxidation reactions catalysed by supported metal nanoparticles with oxygen as the terminal oxidant, the rate of the oxygen reduction can be a limiting factor. This is exemplified by the oxidative dehydrogenation of alcohols, an important class of reactions with modern commercial applications1–3. Supported gold nanoparticles are highly active for the dehydrogenation of the alcohol to an aldehyde4 but are less effective for oxygen reduction5,6. In contrast, supported palladium nanoparticles are less active than gold for dehydrogenation but offer high efficacy for oxygen reduction5,6. This imbalance can be overcome by alloying gold with palladium which gives enhanced activity to both reactions7,8; however, the electrochemical potential of the alloy is a compromise between that of the two metals meaning that although the oxygen reduction is improved in the alloy, the dehydrogenation activity is poorer. Here we show that by separating the gold and palladium components in bimetallic carbon-supported catalysts we can almost double the reaction rate beyond that achieved with a corresponding alloy catalyst. We demonstrate this using physical mixtures of carbon-supported monometallic gold and palladium and a bimetallic catalyst comprising separated gold and palladium regions. Furthermore, we demonstrate electrochemically that this enhancement is attributable to the coupling of separate redox processes occurring at isolated gold and palladium sites. The discovery of this novel catalytic effect, a cooperative redox enhancement (CORE), offers a new approach to the design of multi-component heterogeneous catalysts.

Selective partial oxidation of methane to valuable oxygenated products remains a great challenge, as typically over oxidation of oxygenated products to COx is observed. Weak oxidative species on the catalyst surface have a great potential to overcome this limitation. However, weak oxidative species usually have low concentrations and are easily decomposed. Here we report a Pd/MoO3 photocatalyst which can realize excellent methane oxidation to methanol and methyl hydroperoxide in pure water, under simulated solar light by in situ generated H2O2 at room temperature and pressure. The combined selectivity for methanol and methyl hydroperoxide is up to 98.6%, representing a productivity rate of 42.5 μmol gcat−1 h−1. Further studies on the reaction mechanism indicate that PdO species on the Pd loaded MoO3 catalyst play an essential role in the suppression of over oxidation. In this case PdO traps the photo-generated electrons, leaving photo-generated holes for decomposition of H2O2 into weak oxidative hydroperoxyl radicals which are not involved in the formation of over oxidation products.

The use of heterogeneous catalysts to convert glycerol into lactic acid has been extensively investigated in recent years. Several different strategies have been employed, but importantly, the highest production rates of lactic acid are achieved through aerobic oxidation under alkaline conditions. Despite the progress made in this area, insight into how the catalytic properties influence the selectivity of the competing pathways, oxidative dehydrogenation and dehydration, remains limited. Developing a deeper understanding is therefore critical, if process commercialization is to be realized. Using a model Pt/TiO2 catalyst, we set out to investigate how the supported metal particle size and support phase influenced the selectivity of these two pathways. Both these parameters have a profound effect on the reaction selectivity. Using a range of characterization techniques and through adopting a systematic approach to experimental design, important observations were made. Both pathways are first instigated through the oxidative dehydrogenation of glycerol, leading to the formation of glyceraldehyde or dihydroxyacetone. If these intermediates desorb, they rapidly undergo dehydration through a reaction with the homogeneous base in solution. Based on the experimental evidence we therefore propose that selectivity to lactic acid is influenced by surface residence time.

The development of highly active single-atom catalysts (SACs) and identifying their intrinsic active sites in oxidizing industrial hazardous hydrocarbons are challenging prospects. Tuning the electronic metal-support interactions (EMSIs) is valid for modulating the catalytic performance of SACs. We propose that the modulation of the EMSIs in a Pt1−CuO SAC significantly promotes the activity of the catalyst in acetone oxidation. The EMSIs promote charge redistribution through the unified Pt−O−Cu moieties, which modulates the d-band structure of atomic Pt sites, and strengthens the adsorption and activation of reactants. The positively charged Pt atoms are superior for activating acetone at low temperatures, and the stretched Cu−O bonds facilitate the activation of lattice oxygen atoms to participate in subsequent oxidation. We believe that this work will guide researchers to engineer efficient SACs for application in hydrocarbon oxidation reactions.\ud \ud Open Research

A series of TiO2 anatase materials were synthesized with varying proportions of exposed (101) and (001) facets. Pt was subsequently impregnated onto these materials, which were then exposed to either an aerobic or reductive thermal treatment. The final catalysts were assessed for their performance in the aerobic, solvent free oxidation of octanol. Many kinds of characterization methods were employed to gain insight on how the exposed support facets influenced the catalysis. Thermal reduction of the catalysts led to a loss in the support surface structure, but in the contrary, after calcination, the defined facets remained, which was revealed by Raman and XRD. We further provide evidence that the coordinately unsaturated O2c–Ti5c–O2c sites present in the support promoted the dispersion of Pt after calcination in Air, leading to the formation of low-coordinated and electron-deficient Pt clusters, based on high resolution- and spherical- aberration corrected transmission electron microscopy and X-ray absorption fine structure analysis. The calcined catalysts were far more active for both the oxidation of octanol and intermediate octanal, thus resulting in a higher selectivity of octanoic acid. Catalyst performance closely correlated with the proportion of low-coordinated Pt species and the specific surface coordination structure of the support in the catalyst. Subsequent in-situ Fourier transfer infrared experiments, conducted using alcohol and aldehydic probe molecules, confirmed that substrate adsorption was strongly influenced by the low-coordinated sites of both the Pt cluster and the exposed surface facets on the support.

Low temperature oxidation of alcohols over heterogeneous catalysts is exceptionally challenging, particularly under neutral conditions. Herein, we report on an efficient, base-free method to oxidise glycerol over a 0.5%Pd-0.5%Fe/SiO2 catalyst at ambient temperature in the presence of gaseous H2 and O2. The exceptional catalytic performance was attributed to the in situ formation of highly reactive surface-bound oxygenated species, which promote the dehydrogenation on the alcohol. The PdFe bimetallic catalyst was determined to be significantly more active than corresponding monometallic analogues, highlighting the important role both metals have in this oxidative transformation. Fe leaching was confirmed to occur over the course of the reaction but sequestering experiments, involving the addition of bare carbon to the reactions, confirmed that the reaction was predominantly heterogeneous in nature. Investigations with electron paramagnetic resonance spectroscopy suggested that the reactivity in the early stages was mediated by surface-bound reactive oxygen species; no homogeneous radical species were observed in solution. This theory was further evidenced by a direct H2O2 synthesis study, which confirmed that the presence of Fe in the bimetallic catalyst neither improved the synthesis of H2O2 nor promoted its decomposition over the PdFe/SiO2 catalyst.

The development of highly active single-atom catalysts (SACs) and identifying their intrinsic active sites in oxidizing industrial hazardous hydrocarbons are challenging prospects. Tuning the electronic metal-support interactions (EMSIs) is valid for modulating the catalytic performance of SACs. We propose that the modulation of the EMSIs in a Pt

Stabilizers are commonly employed to synthesize nanocrystals with well-defined morphologies and size distributions, making them ideal tools to study structure–activity relationships in heterogeneous catalysts. While it is well documented that stabilizers can influence both the structure and size of the nanocrystals, little emphasis has been placed on how the properties of these species influence catalytic performance. Herein, different polymers (poly-sodium acrylate (PNaA), poly(vinyl alcohol) (PVA), and poly(vinyl pyrrolidone) (PVP)) and the monomer sodium acrylate (NaA) were used as stabilizers for the synthesis of Au nanoparticles supported on TiO2. The mean Au particle size in all of the catalysts was comparable regardless of the stabilizer used; however, the activity of these catalysts toward CO oxidation differed markedly. The activity decreased in the sequence Au/TiO2 (NaA) > Au/TiO2 (PNaA) > Au/TiO2 (none) > Au/TiO2 (PVA) > Au/TiO2 (PVP), despite the Au/TiO2 (none) catalyst possessing a larger Au mean particle size, suggesting active site blocking due to the steric nature of the polymer species. According to UV–vis, X-ray photoelectron spectroscopy (XPS), in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), high-resolution transmission electron microscopy (HRTEM), X-ray absorption spectroscopy (XAS), and composition analysis experiments, it was concluded that the enhanced activity of Au/TiO2 (NaA) and Au/TiO2 (PNaA) catalysts were attributed to the large proportions of low coordinate step/kink Au sites. It is to be noted that the electronic interactions between NaA and HAuCl4 facilitated the production of active Au nanoparticles. Our findings highlight that the physicochemical properties of the stabilizer can profoundly influence the reactivity of supported metal catalysts prepared by sol-immobilization. These observations highlight the influence that various stabilizers have on the morphology of supported metal nanoparticles and provides an explanation for the low activity of catalysts prepared using common forms such as PVA and PVP.

Shape effects of nanocrystal catalysts in different reactions have attracted remarkable attention. In the present work, three types of α-Fe2O3 oxides with different micromorphologies were rationally synthesized via a facile solvothermal method and adopted in deep oxidation of ethane. The physicochemical properties of prepared materials were characterized by XRD, N2 sorption, FE-SEM, HR-TEM, FTIR, in situ DRIFTS, XPS, Mössbauer spectroscopy, in situ Raman, electron energy loss spectroscopy, and H2-TPR. Moreover, the formation energy of oxygen vacancy and surface electronic structure on various crystal faces of α-Fe2O3 were explored by DFT calculations. It is shown that nanosphere-like α-Fe2O3 exhibits much higher ethane destruction activity and reaction stability than nanocube-like α-Fe2O3 and nanorod-like α-Fe2O3 due to larger amounts of oxygen vacancies and lattice defects, which greatly enhance the concentration of reactive oxygen species, oxygen transfer speed, and material redox property. In addition to this, DFT results reveal that nanosphere-like α-Fe2O3 has the lowest formation energy of oxygen vacancy on the (110) facet (Evo (110) = 1.97 eV) and the strongest adsorption energy for ethane (−0.26 eV) and O2 (−1.58 eV), which can accelerate the ethane oxidation process. This study has deepened the understanding of the face-dependent activities of α-Fe2O3 in alkane destruction.

The production of methanol from glycerol over a basic oxide, such as MgO, using high reaction temperatures (320 °C) is a promising new approach to improving atom efficiency in the production of biofuels. The mechanism of this reaction involves the homolytic cleavage of the C3 feedstock, or its dehydration product hydroxyacetone, to produce a hydroxymethyl radical species which can then abstract an H atom from other species. Obtaining a detailed reaction mechanism for this type of chemistry is difficult due to the large number of products present when the system is operated at high conversions. In this contribution we show how DFT based modelling studies can provide new insights into likely reaction pathways, in particular the source of H atoms for the final step of converting hydroxymethyl radicals to methanol. We show that water is unlikely to be important in this stage of the process, C-H bonds of C2 and C3 species can give an energetically favourable pathway and that the disproportionation of hydroxymethyl radicals to methanol and formaldehyde produces a very favourable route. Experimental analysis of reaction products confirms the presence of formaldehyde. The calculations presented in this work also provides new insight into the role of the catalyst surface in the reaction showing that the base sites of the MgO(100) are able to deprotonate hydroxymethyl radicals but not methanol itself. In carrying out the calculations we also show how periodic DFT and QM/MM approaches can be used together to obtain a rounded picture of molecular adsorption to surfaces and homolytic bond cleavage which are both central to the reactions studied.

Accurately identifying different representations of the same real–world entity is an integral part of data cleaning and many methods have been proposed to accomplish it. The challenges of this entity resolution task that demand so much research attention are often rooted in the task–specificity and user–dependence of the process. Adopting deep learning techniques has the potential to lessen these challenges. In this paper, we set out to devise an entity resolution method that builds on the robustness conferred by deep autoencoders to reduce human–involvement costs. Specifically, we reduce the cost of training deep entity resolution models by performing unsupervised representation learning. This unveils a transferability property of the resulting model that can further reduce the cost of applying the approach to new datasets by means of transfer learning. Finally, we reduce the cost of labeling training data through an active learning approach that builds on the properties conferred by the use of deep autoencoders. Empirical evaluation confirms the accomplishment of our cost–reduction desideratum, while achieving comparable effectiveness with state–of–the–art alternatives.

In oxidation reactions catalysed by supported metal nanoparticles with oxygen as the terminal oxidant, the rate of the oxygen reduction can be a limiting factor. This is exemplified by the oxidative dehydrogenation of alcohols, an important class of reactions with modern commercial applications

Exploring thermally robust single atom catalysts (SACs) is of great significance. Here, we develop a universal strategy for stabilizing Pt atoms on the mono-oxygen vacancies of CeO2 with diverse exposed facets. The stabilization mechanism was proposed that the formed Pt-O-Ce interface will be taken into distortion spontaneously to keep thermodynamics stable through strong metal-support interactions. The highest degree of Pt-O-Ce distortion is achieved over Pt1-CeO2{100} material, which exhibits exceptional efficiency and thermal stability for oxygenated hydrocarbon removal. The enhanced adsorption capacity of O2 and methanol confirmed in the distortion interface is seen as another crucial reason for improving the stability of SACs. Methanol oxidation on Pt1-CeO2{100} obeys the L-H mechanism under relatively low temperature and then goes through to the MVK mechanism with temperature increasing. We believe that these results would bring new opportunities in the fabrication of SACs and applications of them in thermal reactions.

2 Schemes, 3 Tables, 5 Figures., A high surface area mesoporous TiO2 material (110 m2/g) was synthesised using a nanocasting methodology, utilizing SBA‐15 as a hard template. This material was subsequently used as a support to prepare a series of 1 wt.% AuPt/TiO2 catalysts, synthesised by conventional impregnation and sol‐immobilisation. Catalysts were tested for the oxidation of glycerol to lactic acid and their performance was compared with corresponding catalysts supported on TiO2−P25, TiO2‐anatase and TiO2‐rutile. Higher rates of reaction and higher selectivity to lactic acid were observed over nanocast TiO2 supported catalysts. The increased performance of these catalysts was attributed to the presence of Si on the surface of the support, which likely arose from inefficient etching of the SBA‐15 template. The presence of Si in these catalysts was confirmed by X‐ray photoelectron spectroscopy and electron energy loss spectroscopy. It was proposed that the residual Si present increases the Brønsted acidity of the TiO2 support, which can lead to the formation of Lewis acid sites under reaction conditions; both sites are known to catalyse the dehydration of a primary alcohol in glycerol. Typically, under alkaline conditions, lactic acid is formed by the nucleophilic abstraction of a hydrogen. Thus, we propose that the improved selectivity to lactic acid over the nanocast TiO2 supported catalyst is attributed to the co‐operation of heterogeneous and homogeneous dehydration reactions, as both compete directly with a direct oxidation pathway, which leads to the formation of oxidation products such as glyceric and tartronic acid., T. García would like to acknowledge the Spanish MICINN through its Mobility program for stays of senior researchers and professors in foreign countries (grant number PRX18/00474) for funding. O.S.P acknowledges the FPI fellowship (BES-2016-077750) funded by Spanish MINECO. B.S. also thank MINECO (MAT2017-84118-C2-1-R project) for funding. We would also like to thank the Cardiff University TEM facility for the TEM and FEG-SEM electron microscopy data acquired and Diamond Light Source for access and support in use of the electron Physical Science Imaging Centre (Instrument E01 and proposal number MG21641 and MG22766) which contributed to the results presented here.

The oxidation of glycerol under alkaline conditions in the presence of a heterogeneous catalyst can be tailored to the formation of lactic acid, an important commodity chemical. Despite recent advances in this area, the mechanism for its formation is still a subject of contention. In this study, we use a model 1 wt. % AuPt/TiO

A novel method for the synthesis of MFI zeolites has been developed, which does not require any crystal seeds or solvent. The adaptability of this method was also evidenced; a series of ZSM-5 zeolites with differing Si/Al ratios (18∼∞) were synthesized, which to date, has been a challenge in the field of solvent-free synthesis. The materials were probed by in situ DRIFTS and 2D 27Al–19F HETCOR NMR spectroscopy, the results from which indicated that fluorine-containing species play a crucial role in the crystallization of ZSM-5. During the crystallization process F− anions coordinate with Al3+ cations, resulting in the formation of 6-coordinated “F–Al–O–Si” species. It is these intermediate species which drive the formation of tetrahedral [AlO4]− units in the zeolitic framework. The effectiveness of these materials as catalyst supports was subsequently assessed in the hydrogenation of levulinic acid and glucose, which exhibited a comparable performance to commercial ZSM-5. The simple, efficient and low-cost method presented herein provides an alternative approach for the green scaled-up synthesis of zeolites.

Catalytic hydrogenation of levulinic acid to form γ-valerolactone was studied over Cu–ZrO2 catalysts doped with metal oxides from the first-row transition metals. The Cu–ZrO2 material was prepared by oxalate gel coprecipitation, and dopants were added by an incipient wetness approach. The addition of 1% Mn into Cu–ZrO2 significantly increases the yield of γ-valerolactone, and the catalytic activity of Mn/Cu–ZrO2 was found to be 1.6 times higher than that of the undoped Cu–ZrO2 catalyst. Catalyst characterization suggests that the Mn dopant improves the dispersion of Cu on the surface of ZrO2. Kinetic studies show that the reaction order with respect to the substrate concentration is approximately zero. However, the order of reaction with respect to the partial pressure of H2 is different for the Mn/Cu–ZrO2 and Cu–ZrO2 catalysts. Comparison of reaction products from reactions carried out in H2O and D2O solvents using 1H NMR and 13C NMR show that there is a pre-equilibrium keto–enol isomerization step under our reaction conditions. DFT calculations show that the enol isomers have a higher affinity for the Cu surface, which may improve the availability of the substrate in the hydrogenation step of the reaction.

A novel reactor that combines a catalyst slurry flowing inside a loop configuration, incorporating a tubular membrane (Teflon AF-2400) for controlled oxygen delivery was designed and employed for the aerobic oxidation of benzyl alcohol using a 1 wt% Au-Pd/TiO2 powdered catalyst. This reactor keeps the liquid phase saturated with oxygen, while avoiding the creation of bubbles in it, thus enhancing operation safety. Experimental results in batch mode compared with those of a conventional autoclave demonstrated that the slurry loop membrane reactor reached a similar oxidation turnover frequency (20,000–25,000 h−1) with comparable values of benzaldehyde selectivity (∼70%). Continuous operation was achieved by using a crossflow filter connected to the loop to keep the catalyst from exiting the reactor. Using a 60 cm long tubular membrane, with the slurry flow circulating at 10 mL/min, continuous reaction was performed at 100–120 °C, 0–5 bar oxygen pressure and 1.2–5.0 g/L catalyst loading. Selectivity to benzaldehyde increased by either decreasing the reaction temperature or increasing the external oxygen pressure. The oxygen consumption rate decreased linearly with the catalyst loading, suggesting negligible gas-liquid mass transfer resistance. This was further evidenced by doubling the length of the tubular membrane, which had no effect on the oxidation turnover frequency. The slurry loop membrane reactor showed significantly better performance than packed-bed membrane microchannel reactors, and similar performance as that of a trickle-bed capillary reactor. This reactor can be implemented for a wide range of applications, which rely on the use of powder catalyst, are limited by gaseous reactant availability and require safe operation.

Pt0.3Mnx/SiO2 nanocubic (nc) micro-/mesoporous composite catalysts with varied Mn contents were synthesized and tested for the oxidation of methyl ethyl ketone (MEK). Results show that MEK can be efficiently decomposed over synthesized Pt0.3Mnx/SiO2-nc materials with a reaction rate and turnover frequency respectively higher than 12.7 mmol gPt–1 s–1 and 4.7 s–1 at 100 °C. Among these materials, the Pt0.3Mn5/SiO2-nc catalyst can completely oxidize MEK at just 163 °C under a high space velocity of 42600 mL g–1 h–1. The remarkable performance of these catalysts is attributed to a synergistic effect between the Pt nanoparticles and Mn2O3. NH3-TPD and NH3-FT-IR experiments revealed that exposed Mn2O3 (222) facets enhance the quantity of Brønsted acid sites in the catalyst, which are considered to be responsible for promoting the desorption of surface-adsorbed O2 and CO2. It is suggested that the desorption of these species liberates active sites for MEK molecules to adsorb and react. 18O2 isotopic labeling experiments revealed that the presence of a Pt–O–Mn moiety weakens the Mn–O bonding interactions, which ultimately promotes the mobility of lattice oxygen in the Mn2O3 system. It was determined that the Mn4+/Mn3+ redox cycle in Mn2O3 allows for the donation of electrons to the Pt nanoparticles, enhancing the proportion of Pt0/Pt2+ and in turn increasing the activity and stability of catalyst. In situ DRIFTS, online FT-IR, and DFT studies revealed that acetone and acetaldehyde are the main intermediate species formed during the activation of MEK over the Pt0.3Mn5/SiO2-nc catalyst. Both intermediates were found to partake in sequential reactions resulting in the formation of H2O and CO2 via formaldehyde.

Currently, Pb poisoning of heterogeneous catalysts is considered to be a key area of interest in research involved with industrial NOx reduction. As such, a series of Pb-poisoned V2O5-WO3/TiO2 catalysts were prepared by a wet impregnation method and the influence of SO2 on the performance of these poisoned catalysts for NOx reduction was assessed both experimentally and using theoretical calculations. As expected, the incorporation of Pb in these materials resulted in a significant reduction in their catalytic performance. The conversion of NOx over the Pb-V2O5-WO3/TiO2 catalyst increased from approximately 50% to 90% in presence of SO2 (2000 ppm) at 350 °C. It was postulated that in the absence of SO2, Pb reacts with surface V-OH species, which ultimately results in the destruction of Brønsted acid sites; considered to be crucial for the catalytic conversion of NOx. In the presence of SO2 however, enhanced catalytic activity was observed which was suggested to be a result of the formation of additional Brønsted sites (S-OH) via a surface bidentate sulfate intermediate species. The formation of these species was attributed to the interaction of Pb with SO2 and O2 on the surface of the catalyst. Density functional theory (DFT) calculations based on a monolayer V model on TiO2 (0 0 1) showed that SO2 absorbed selectively onto Pb sites rather than V or Ti oxides. It was subsequently determined that NH3 absorption proceeds through the formation of Pb-N species with Pb atom and H-O with SO2. We believe that the present work provides new insights into the design and application of SCR catalysts with specific relevance for application in flue gas streams which contain high quantities of Pb content.

Carbon-based materials are some of the most commonly studied catalysts for the conversion of cellulose to polyols. The catalytic performance of these materials, however, is typically limited by the access of the substrate to the active sites, which is governed by the poor solubility of cellulose in aqueous solutions. In an attempt to resolve this, we presented a novel hierarchical carbon material which was prepared by a dual-templating method. Transmission electron microscopy and porosity measurements confirmed that the resultant materials consisted of both spherical macropores and well-defined mesoporous channels. Additional characterisation of this material revealed that it has an exceptionally high surface area (>1110 m2 / g) and a high concentration of acidic sites, which are considered to be crucial for the hydrolysis of cellulose. Ni nanoparticles were subsequently immobilised onto this material and some additional carbon supports. It was determined that the high surface area and porosity of the synthesised carbon material assisted with the dispersion of the Ni nanoparticles. This Ni catalyst was found to be highly efficient for the one-pot conversion of cellulose to polyols, which is proposed to be a consequence of both the high number of acid sites and excellent Ni dispersion. This approach to catalyst design, offers a novel method for the valorisation of cellulose.

A novel pH gradient methodology was used to synthesise a series of Cu–ZrO2 catalysts containing different quantities of Cu and Zr. All of the catalysts were highly selective to the desired product, γ-valerolactone, and are considerably more stable than Cu–ZrO2 catalysts prepared by other co-precipitation methods for this reaction. Characterisation and further investigation of these catalysts by XRD, BET, SEM and XPS provided insight into the nature of the catalytic active site and the physicochemical properties that lead to catalyst stability. We consider the active site to be the interface between Cu/CuOx and ZrOx and that lattice Cu species assist with the dispersion of surface Cu through the promotion of a strong metal support interaction. This enhanced understanding of the active site and roles of lattice and surface Cu will assist with future catalyst design. As such, we conclude that the activity of Cu–ZrO2 catalysts in this reaction is dictated by the quantity of Cu–Zr interface sites.

Heterogeneous catalysts with single‐atom active sites offer a means of expanding the industrial application of noble metal catalysts. Herein, an atomically dispersed Pt1‐Co3O4 catalyst is presented, which exhibits an exceptionally high efficiency for the total oxidation of methanol. Experimental and theoretical investigations indicate that this catalyst consists of Pt sites with a large proportion of occupied high electronic states. These sites possess a strong affinity for inactive Co2+ sites and anchor over the surface of (111) crystal plane, which increases the metal–support interaction of the Pt1‐Co3O4 material and accelerates the rate of oxygen vacancies regeneration. In turn, this is determined to promote the coadsorption of the probe methanol molecule and O2. Density functional theory calculations confirm that the electron transfer over the oxygen vacancies reduces both the methanol adsorption energy and activation barriers for methanol oxidation, which is proposed to significantly enhance the dissociation of the CH bond in the methanol decomposition reaction. This investigation serves as a solid foundation for characterizing and understanding single‐atom catalysts for heterogeneous oxidation reactions.

The reaction of aqueous glycerol over a series of ceria catalysts is investigated, to produce bio-renewable methanol. Product distributions were greatly influenced by the reaction temperature and catalyst contact time. Glycerol conversion of 21% was achieved for a 50 wt.% glycerol solution, over CeO2 (8 m2 g−1) at 320 °C. The carbon mass balance was >99 % and the main product was hydroxyacetone. In contrast, at 440 °C the conversion and carbon mass balance were >99.9 % and 76 % respectively. Acetaldehyde and methanol were the major products at this higher temperature, as both can be formed from hydroxyacetone. The space-time yield (STY) of methanol at 320 °C and 440 °C was 15.2 and 145 gMeOH kgcat−1 h−1 respectively. Fresh CeO2 was prepared and calcined at different temperatures, the textural properties were determined and their influence on the product distribution at iso-conversion and constant bed surface area was investigated. No obvious differences to the glycerol conversion or product selectivity were noted. Hence, we conclude that the surface area of the CeO2 does not appear to influence the reaction selectivity to methanol and other products formed from the conversion of glycerol.

Due to high catalytic activity and excellent resistance to SO2 and H2O, sulfate materials are considered to be promising vanadium-free catalysts for selective catalytic reduction of NOx with NH3 (NH3-SCR). Despite this, investigations about thermal stability of sulfate SCR catalysts are limited, which is surprising given that sulfates are typically susceptible to thermal decomposition. In this work, the thermal stability of Fe2(SO4)3/TiO2 catalysts was investigated. It was determined that the thermal decomposition of Fe2(SO4)3 resulted in NOx conversion decreased from 90% to 60% at 350 °C. Interestingly however, the introduction of SO2 into the gas stream was found to reverse the effects of the thermal deactivation and the NOx conversion of 90% (350 °C) was once again observed. Extensive characterization of each catalyst sample and density functional theory (DFT) calculations were subsequently conducted. The reduction in catalytic activity after the thermal treatment was attributed to the transformation of Fe2(SO4)3 to α-Fe2O3, which reduced the quantity of Bronsted acid sites on the catalyst. The presence of SO2 in the gas stream was found to reverse this phase transformation which ultimately led to the recovery of Bronsted acid sites. DFT calculations indicated that SO2 adsorbed selectively on Fe atoms of the thermal deactivated catalysts and S-Fe bond should mainly be formed by electrons from p orbitals of S and Fe atoms. Then NH3 could be adsorbed on the surface by N-S bond with SO2. The recoverable property of this catalyst provides a promising outlook for the commercial application, especially given that industrial flue gas streams regularly contain SO2.

Shape effects of nanocrystal catalysts in different reactions have attracted remarkable attention. In the present work, three types of α-Fe

It is well known that urbanization and industrialization have resulted in the rapidly increasing emissions of volatile organic compounds (VOCs), which are a major contributor to the formation of secondary pollutants (e.g., tropospheric ozone, PAN (peroxyacetyl nitrate), and secondary organic aerosols) and photochemical smog. The emission of these pollutants has led to a large decline in air quality in numerous regions around the world, which has ultimately led to concerns regarding their impact on human health and general well-being. Catalytic oxidation is regarded as one of the most promising strategies for VOC removal from industrial waste streams. This Review systematically documents the progresses and developments made in the understanding and design of heterogeneous catalysts for VOC oxidation over the past two decades. It addresses in detail how catalytic performance is often drastically affected by the pollutant sources and reaction conditions. It also highlights the primary routes for catalyst deactivation and discusses protocols for their subsequent reactivation. Kinetic models and proposed oxidation mechanisms for representative VOCs are also provided. Typical catalytic reactors and oxidizers for industrial VOC destruction are further discussed. We believe that this Review will provide a great foundation and reference point for future design and development in this field.

A series of ceria-based solid solution metal oxides were prepared by co-precipitation and evaluated as catalysts for glycerol cleavage, principally to methanol. The catalyst activity and selectivity to methanol were investigated with respect to the reducibility of the catalysts. Oxides comprising Ce-Pr and Ce-Zr were prepared, calcined and compared to CeO 2 , Pr 6 O 11 and ZrO 2 . The oxygen storage capacity of the catalysts was examined with analysis of Raman spectroscopic measurements and a temperature programmed reduction, oxidation and reduction cycle. The incorporation of Pr resulted in significant defects, as evidenced by Raman spectroscopy. The materials were evaluated as catalysts for the glycerol to methanol reaction, and it was found that an increased defect density or reducibility was beneficial. The space–time yield of methanol normalized to surface area over CeO 2 was found to be 0.052 mmol MeOH m −2 h −1 , and over CeZrO 2 and CePrO 2 , this was to 0.029 and 0.076 mmol MeOH m −2 h −1 , respectively. The inclusion of Pr reduced the surface area; however, the carbon mole selectivity to methanol and ethylene glycol remained relatively high, suggesting a shift in the reaction pathway compared to that over ceria. This article is part of a discussion meeting issue ‘Science to enable the circular economy'.

Heterogeneous catalysts with single-atom active sites offer a means of expanding the industrial application of noble metal catalysts. Herein, we present an atomically dispersed Pt1-Co3O4 catalyst, which exhibits an exceptionally high catalytic activity for the total oxidation of various representative volatile organic compounds. Experimental and theoretical investigations indicated that this catalyst consisted of Pt sites with a large proportion of occupied high electronic states. These sites exhibited a strong affinity for the 3d orbital of Co, which increased electron transfer from Pt to Co3O4 and ultimately, accelerated the rate of oxygen vacancy regeneration. In turn, this was determined to promote the co-adsorption of probe VOC and O2. With methanol, DFT calculations confirmed that the electron transfer over the oxygen vacancy reduces both the methanol adsorption energy and activation barriers for methanol oxidation, which was proposed to significantly enhance the dissociation of the C-H bond in the methanol decomposition reaction. This investigation serves as a solid foundation for characterizing and understanding single-atom catalysts for heterogeneous oxidation reactions.

The base-free selective catalytic oxidation of n-butanol by O2 in an aqueous phase has been studied using Au-Pd bimetallic nanoparticles supported on titania. Au-Pd/TiO2 catalysts were prepared by different methods: wet impregnation, physical mixing, deposition-precipitation and sol immobilisation. The sol immobilisation technique, which used polyvinyl alcohol (PVA) as the stabilizing agent, gave the catalyst with the smallest average particle size and the highest stable activity and selectivity towards butyric acid. Increasing the amount of PVA resulted in a decrease in the size of the nanoparticles. However, it also reduced activity by limiting the accessibility of reactants to the active sites. Heating the catalyst to reflux with water at 90 °C for 1 h was the best method to enhance the surface exposure of the nanoparticles without affecting their size, as determined by TEM, X-ray photoelectron spectroscopy and CO chemisorption analysis. This catalyst was not only active and selective towards butyric acid but was also stable under the operating conditions.

Mg(OH)2‐ and Mg(OH)2‐containing materials can provide excellent performance as supports for AuPd nanoparticles for the oxidation of glycerol in the absence of base, which is considered to be a result of additional basic sites on the surface of the support. However, its influence on the reaction solution is not generally discussed. In this paper, we examine the relationship between the basic Mg(OH)2 support and AuPd nanoparticles in detail using four types of catalyst. For these reactions, the physical interaction between Mg(OH)2 and AuPd was adjusted. It was found that the activity of the AuPd nanoparticles increased with the amount of Mg(OH)2 added under base‐free conditions, regardless of its interaction with the noble metals. In order to investigate how Mg(OH)2 affected the glycerol oxidation, detailed information about the performance of AuPd/Mg(OH)2, physically mixed (AuPd/C+Mg(OH)2) and (AuPd/C+NaHCO3) was obtained and compared. Furthermore, NaOH and Mg(OH)2 were added during the reaction using AuPd/C. All these results indicate that the distinctive and outstanding performance of Mg(OH)2 supported catalysts in base‐free condition is in fact directly related to its ability to affect the pH during the reaction and as such, assists with the initial activation of the primary alcohol, which is considered to be the rate determining step in the reaction.

We have investigated the optimisation of the catalytic parameters for the preparation of catalysts by the simple mixing and thermal treatment of a support and metal acetate precursors. We have studied the effect of metal ratio and metal loading to produce a catalyst which has the optimum activity for a variety of reactions including benzyl alcohol oxidation, glycerol oxidation and the direct synthesis of hydrogen peroxide. We have demonstrated the high activity of these catalyst's for a variety of substrates and performed XPS and XRD studies on the catalysts to help elucidate the origin of the catalysts improved activity.