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Two different routes of synthesis were followed in order to compare the surface properties of two Cu-SAPO-34 catalysts. The direct copper incorporation during the hydrothermal synthesis, compared to the conventional impregnation method, allowed us to study the impact of active centers location on the catalytic activity during both the selective catalytic reduction of NOx by NH3 and the NH3 oxidation. X-ray diffraction, ex-situ diffuse reflectance infrared spectroscopy and X-ray photoelectron spectroscopy analysis were performed to know the copper location and its state for each catalysts. A unique location of the copper oxide at the surface of the synthesized catalyst was observed when the hydrothermal process was used. For similar Cu contents in the catalysts, different catalytic behaviors during the selective catalytic reduction of NOx by NH3 and during the NH3 oxidation were observed as a consequence of the specific activity of the copper clusters. Indeed, some cations in exchanged position were detected when the impregnation method was used, allowing high SCR performance at low temperature. On the other hand, the small copper clusters at the surface and the exchanged cations exhibited a certain NH3 oxidation at low temperature, hindering DeNOx activity. Catalyst with mainly large copper clusters and no appreciable occurrence of exchanged Cu2+ present in a range of temperatures, limited NH3 oxidation and high SCR performance.

In Earth’s atmosphere, the surface tension of sub-micron aerosol particles is suspected to affect their efficiency in becoming cloud droplets. But this quantity cannot be measured directly and is inferred from the chemical compounds present in aerosols. Amphiphilic surfactants have been evidenced in aerosols but experimental information on the surface properties of their mixtures with other aerosol components is lacking. This work explores experimentally the surface properties of aqueous mixtures of amphiphilic surfactants (SDS, Brij35, TritonX100, TritonX114, and CTAC) with inorganic salts (NaCl, (NH 4 ) 2 SO 4 ) and soluble organic acids (oxalic and glutaric acid) using pendant droplet tensiometry. Contrary to what could be expected, inorganic salts and organic acids systematically enhanced the efficiency of the surfactants rather than reduced it, by further lowering the surface tension and, in some cases, the CMC. Furthermore, all the mixtures studied were strongly non-ideal, some even displaying some synergism, thus demonstrating that the common assumption of ideality for aerosol mixtures is not valid. The molecular interactions between the mixture components were either in the bulk (salting out), in the mixed surface monolayer (synergy on the surface tension) or in the micelles (synergy on the CMC) and need to be included when describing such aerosol mixtures.

Soot particles produced by incomplete combustion processes are one of the major components of urban air pollution. Chemistry at their surfaces lead to the heterogeneous conversion of several key trace gases; for example NO₂ interacts with soot and is converted into HONO, which rapidly photodissociates to form OH in the troposphere. In the dark, soot surfaces are rapidly deactivated under atmospheric conditions, leading to the current understanding that soot chemistry affects tropospheric chemical composition only in a minor way. We demonstrate here that the conversion of NO₂ to HONO on soot particles is drastically enhanced in the presence of artificial solar radiation, and leads to persistent reactivity over long periods. Soot photochemistry may therefore be a key player in urban air pollution.

Copper and iron species were co-deposited onto a hydroxyapatite surface to produce bimetallic catalysts. Characterization techniques (XRD, XPS, DR-UV spectroscopy and TEM-EDX) helped in unveiling the speciation, nuclearity, and electronic properties of copper and iron in samples with variable total metal loading (1–10 wt.%) and relative Cu-to-Fe ratios. The speciation of Cu was revealed to be not affected by Fe and vice versa. Conversely, the metal loading turned out to be a key factor ruling the aggregation state of Cu and Fe species. The samples were tested as catalysts in the Selective Catalytic Reduction of NO by NH3 (NH3-SCR) in dry and wet environments under quasi-real conditions (50,000 ppm O2; 50,000 ppm H2O, if present; 120,000 h−1 GHSV) in the 200−500 °C interval. Although the combination of Cu and Fe affords a modest improvement in water resistance compared to their monometallic counterparts, no substantial enhancement in activity was observed for the bimetallic hydroxyapatite-based SCR catalysts.

This work uses machine learning (ML) procedures to investigate the effect of the properties of different cobalt-based catalysts on the oxidation of toluene and propane. The hydrocarbon conversion was modeled using 600 ANNs and 8 supervised regression algorithms. An optimization framework for the input variables was subsequently developed, using the best neural networks to minimize both the catalyst costs and the energy consumption for reaching 97.5% conversion. This optimization analysis showed that for toluene and propane oxidation, the best result was coincidental with that reported elsewhere and with the commercial catalyst, respectively. As expected, the optimization analysis selected the cheapest catalyst (practically negligible influence of the energy cost). The optimization analysis in terms of physical properties of the catalyst showed that the best results obtained with the toluene oxidation would approximately correspond to catalyst Co-C2O4 while those obtained with the propane oxidation did not result to be conclusive.

LaMnO3 (LM) catalysts with a molar ratio of citric acid (CA) to metal (La3+ + Mn2+) nitrates ranging from 0.5 to 2 (LM0.5 to LM2) were synthesized by the citrate sol–gel method with the aim of studying the effect of the citric acid ratio on the physicochemical properties and the catalytic performance in hydrocarbon oxidation. Structural and morphological properties of these catalysts were characterized by X-ray diffraction (XRD) and specific surface area (N2 adsorption) measurements, while the chemical composition was determined by inductively coupled plasma atomic emission spectroscopy (ICP-OES). In the selected samples, additional characterizations were carried out by thermogravimetric and differential thermal analysis (TGA/DTA), Fourier Transform Infrared Spectroscopy (FT-IR), temperature-programmed reduction by hydrogen (H2-TPR), and X-ray photoelectron spectroscopy (XPS). The results showed that the amount of citric acid used significantly influenced the TGA/DTA profile of gels along with the physicochemical properties of the catalysts. The XRD patterns are consistent with the perovskite formation as the main phase. The segregation of a small amount of Mn3O4, detected for molar ratios ranging between 0.5 and 1.5, suggested the formation of a slightly nonstoichiometric LaMn1−xO3 phase with a relatively high content of Mn4+. The catalytic performance was evaluated in the total oxidation of two selected hydrocarbons, toluene and propene, which represent typical volatile organic compounds (VOCs). Typically, three consecutive catalytic cycles were performed in order to reach steady-state performance in toluene and propene oxidation. Moreover, the stability of the catalysts under reaction conditions was investigated through 24-h experiments at 17% of toluene conversion. The catalysts LM1.2, LM1.3, and LM1.5 showed the best catalytic performance in both hydrocarbon oxidations, well comparing with the Pd/Al2O3 used as a reference.

Co3O4 catalysts were prepared via carbonate precipitation and subsequent calcination under specific conditions. The different catalysts were characterized as received using several techniques and tested in the total oxidation of toluene or propane. Calcination at low temperature or under dynamic conditions resulted in Co3O4 catalysts with small crystallite sizes and large surface areas. The performances of the Co3O4 catalysts appeared to be closely related to the low-temperature reducibility. The best catalyst, Co-350D, showed a toluene oxidation rate of 44.5 nmol g−1 s−1 at 200 °C and a propane oxidation rate of 54.0 nmol g−1 s−1 at 150 °C. Meanwhile, Co-350D exhibited excellent cycling stability and decent long-term durability in both reactions.

Whey is a liquid waste issued from the transformation of milk into cheese. Whey is a major environmental problem for the dairy industry due to its high organic load, linked to its high content of lactose. It can be valorized by biological processes based on lactose fermentation into different products such as (1) lactic acid (as food additive), (2) 2,3-butanediol (as feedstock to get products such as methyl-ethyl-ketone or 2-butene for the pharmaceutical and chemical industries), (3) biogas (to obtain energy). The production of 2,3-butanediol from saccharides, such as glucose, has been actively studied over previous decades using several types of microorganisms such as Enterobacter aerogenes , Paenibacillus polymyxa , Klebsiella sp., Serratia marcescens and Escherichia coli . Some of these have even been genetically modified to improve the 2,3-butanediol production. The potential whey fermentation process into 2,3-butanediol depends on several operating conditions such as microorganisms, composition of the culture medium, temperature, pH and aeration. This review first presents a summary of the situation of milk and cheese production in Canada and around the world. It also describes the different kinds of whey and their treatment techniques. Finally, this paper describes the production of 2,3-butanediol from saccharides by various microorganisms under different operating conditions.

In the following work, the catalytic behavior of Pd catalysts prepared using different oxides as support (Al2O3, CeO2 and TiO2) in the catalytic combustion of propene, in low concentration in excess of oxygen, to mimic the conditions of catalytic decomposition of a volatile organic compound of hydrocarbon-type is reported. In addition, the influence of different promoters (Ce, Ti, Fe and Mn) when added to a Pd/Al2O3 catalyst was analyzed. Catalysts were prepared by the impregnation method and were characterized by ICP-OES, N2 adsorption, temperature-programmed reduction, temperature-programmed oxidation, X-ray diffraction, X-ray photoelectron spectroscopy and transmission electron microscopy. Catalyst prepared using CeO2 as the support was less easily reducible, due to the stabilization effect of CeO2 over the palladium oxides. Small PdO particles and, therefore, high Pd dispersion were observed for all of the catalysts, as confirmed by XRD and TEM. The addition of Ce to the Pd/Al2O3 catalysts increased the metal-support interaction and the formation of highly-dispersed Pd species. The addition of Ce and Fe improved the catalytic behavior of the Pd/Al2O3 catalyst; however, the addition of Mn and Ti decreased the catalytic activity in the propene oxidation. Pd/TiO2 showed the highest catalytic activity, probably due to the high capacity of this catalyst to reoxidize Pd into PdO, as has been found in the temperature-programmed oxidation (TPO) experiments.

Metal-doped (Mn, Cu, Ni, and Fe) cobalt oxides were prepared by a coprecipitation method and were used as catalysts for the total oxidation of toluene and propane. The metal-doped catalysts displayed the same cubic spinel Co3O4 structure as the pure cobalt oxide did; the variation of cell parameter demonstrated the incorporation of dopants into the cobalt oxide lattice. FTIR spectra revealed the segregation of manganese oxide and iron oxide. The addition of dopant greatly influenced the crystallite size, strain, specific surface area, reducibility, and subsequently the catalytic performance of cobalt oxides. The catalytic activity of new materials was closely related to the nature of the dopant and the type of hydrocarbons. The doping of Mn, Ni, and Cu favored the combustion of toluene, with the Mn-doped one being the most active (14.6 × 10−8 mol gCo−1 s−1 at 210 °C; T50 = 224 °C), while the presence of Fe in Co3O4 inhibited its toluene activity. Regarding the combustion of propane, the introduction of Cu, Ni, and Fe had a negative effect on propane oxidation, while the presence of Mn in Co3O4 maintained its propane activity (6.1 × 10−8 mol gCo−1 s−1 at 160 °C; T50 = 201 °C). The excellent performance of Mn-doped Co3O4 could be attributed to the small grain size, high degree of strain, high surface area, and strong interaction between Mn and Co. Moreover, the presence of 4.4 vol.% H2O badly suppressed the activity of metal-doped catalysts for propane oxidation, among them, Fe-doped Co3O4 showed the best durability for wet propane combustion.