People spend approximately 80% of their time indoor, making the understanding of the indoor chemistry an important task for safety. The high surface‐area‐to‐volume ratio characteristic of indoor ...environments leads the semi‐volatile organic compounds (sVOCs) to deposit on the surfaces. Using a long path absorption photometer (LOPAP), this work investigates the formation of nitrous acid (HONO) through the photochemistry of adsorbed nitrate anions and its enhancement by the presence of furfural. Using a high‐resolution proton‐transfer‐reaction time‐of‐flight mass spectrometer (PTR‐TOF‐MS), this work also investigates the surface emissions of VOCs from irradiated films of furfural and a mix of furfural and nitrate anions. Among the emitted VOCs, 2(5H)‐furanone/2‐Butenedial was observed at high concentrations, leading to maleic anhydride formation after UV irradiation. Moreover, the addition of potassium nitrate to the film formed NOx and HONO concentrations up to 10 ppb, which scales to ca. 4 ppb for realistic indoor conditions. This work helps to understand the high levels of HONO and NOx measured indoors.
Hydrothermal liquefaction (HTL) is a promising process for the energetic valorization of low-value feedstocks. However, HTL crude oils are incompatible with the existing fuel standards, making their ...upgrade imperative. Nonetheless, the hydrotreatment (HDT) of HTL crude oils is still a challenge due to the complex nature of the feedstock. Therefore, this work explores the relationship between the HTL crude oil origin and the HDT conversion. Five HTL crude oils from different feedstocks, namely, oak sawdust, Brewer’s Spent Grain (spent grain), sewage sludge from two origins, and lignite, and their detailed characterization by elemental analysis, 13C and 31P NMR, molecular weight distribution, comprehensive 2D gas chromatography, and SimDis were compared to those of the HDT liquid product. Lignite displayed the highest potential for producing hydrocarbons, particularly monoaromatics and naphthenes, among the feedstocks tested. The capacity of lignite HTL crude oil to be transformed into hydrocarbons was associated with the absence of compounds resistant to HDT in this feedstock. Similarly, oak sawdust also displayed higher selectivity toward aromatic and naphthene hydrocarbons due to the significant concentration of aromatic compounds in the crude oil. In opposition, the sewage sludge and spent-grain crude oils were particularly selective toward aliphatic hydrocarbons, particularly paraffins, produced from aliphatic components, such as amides, in the crude oil. However, these feedstocks were rich in nitrogenated aromatics, for example, carbazole, which are recalcitrant to hydrotreatment and were not fully converted during the reaction. The differences observed in the HDT liquid composition show that the HTL crude oil composition dictates the potential for producing hydrocarbon fuels. Indeed, HTL crude oils rich in aromatic compounds will yield preferentially naphthenes and aromatic hydrocarbons. In opposition, crude oils richer in aliphatic carbon will be more selective toward paraffins. The nature and concentration of heteroatom components must also be considered since these must be imperatively eliminated.
Lignite from Belchatów in Poland was converted to hydrocarbon fuels, particularly in the kerosene and diesel ranges, through sequential hydrothermal liquefaction (HTL) and hydrotreatment (HDT) of ...the obtained crude oil. Different HDT temperatures were investigated (from 350 °C up to 390 °C). Despite the highly aromatic nature and high heteroatom content, the HTL lignite crude oil could undergo deep hydrodesulfurization (HDS = 99%) and hydrodeoxygenation (HDO = 98%) in a single HDT treatment stage, yielding a liquid product rich in aliphatic and aromatic, particularly monoaromatic, hydrocarbons. The hydrotreatment and hydrogenating capacity of the lignite crude oil was linked to the low concentration of compounds resistant to hydrotreatment in lignite and, consequently, lignite’s crude oil, permitting the easy transformation of the crude oil into hydrocarbon fuel. Still, the significant concentration of aromatic compounds, particularly monoaromatic and diaromatic, in the liquid product (≈45% of fuel range products) suggests that further upgrading, blending, or harsher HDT conditions might be necessary to improve the fuel quality. In addition to the crude oil, the HTL of lignite yielded a stream of char, which displayed a higher calorific value and lower heteroatom content than the original lignite feedstock, thus having a high potential for electricity production, which is the common use of lignite. Thus, introducing an HTL stage to extract crude oil before lignite use in electricity production could provide an alternative fuel source used as a strategy to increase multiple countries’ energetic independence.
Synthesis of high quality colloidal Cerium(III) doped yttrium aluminum garnet (Y
Al
O
:Ce
, "YAG:Ce") nanoparticles (NPs) meeting simultaneously both ultra-small size and high photoluminescence (PL) ...performance is challenging, as generally a particle size/PL trade-off has been observed for this type of nanomaterials. The glycothermal route is capable to yield ultra-fine crystalline colloidal YAG:Ce nanoparticles with a particle size as small as 10 nm but with quantum yield (QY) no more than 20%. In this paper, the first ultra-small YPO
-YAG:Ce nanocomposite phosphor particles having an exceptional QY-to-size performance with an QY up to 53% while maintaining the particle size ≈10 nm is reported. The NPs are produced via a phosphoric acid- and extra yttrium acetate-assisted glycothermal synthesis route. Localization of phosphate and extra yttrium entities with respect to cerium centers in the YAG host has been determined by fine structural analysis techniques such as X-ray diffration (XRD), solid state nuclear magnetic resonance (NMR), and high resolution scanning transmission electron microscopy (HR-STEM), and shows distinct YPO
and YAG phases. Finally, a correlation between the additive-induced physico-chemical environment change around cerium centers and the increasing PL performance has been suggested based on electron paramagnetic resonance (EPR), X-ray photoelectron spectrometry (XPS) data, and crystallographic simulation studies.
Covalent triazine frameworks (CTFs) are a class of porous organic polymers that continuously attract growing interest because of their outstanding chemical and physical properties. However, the ...control of extended porous organic framework structures at the molecular scale for a precise adjustment of their properties has hardly been achieved so far. Here, we present a series of bipyridine-based CTFs synthesized through polycondensation, in which the sequence of specific building blocks is well controlled. The reported synthetic strategy allows us to tailor the physicochemical features of the CTF materials, including the nitrogen content, the apparent specific surface area, and optoelectronic properties. Based on a comprehensive analytical investigation, we demonstrate a direct correlation of the CTF bipyridine content with the material features such as the specific surface area, band gap, charge separation, and surface wettability with water. The entirety of these parameters dictates the catalytic activity as demonstrated for the photocatalytic hydrogen evolution reaction (HER). The material with the optimal balance between optoelectronic properties and highest hydrophilicity enables HER production rates of up to 7.2 mmol/(h·g) under visible light irradiation and in the presence of a platinum cocatalyst.
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•Mechanisms of naphthene hydroconversion over a state-of-the-art Ir/NaY catalyst.•Influence of H2S in the feed: switch from ring opening to skeletal isomerization.•Three naphthenic ...compounds investigated: influence of the size and number of rings.•Advanced products analysis through two-dimensional GCxGC-MS and –FID.
Selective ring opening is an important hydrotreating process for gas oil upgrading. In this work, we have used an Ir/NaY bifunctional catalyst -highly efficient in sulfur-free conditions- as a reference system to assess the effect of H2S impurity concentration (0–1 %) on the kinetics and mechanisms of naphthene conversion under high hydrogen pressure (5 MPa). Three model naphthenic molecules (decalin, perhydroindan and butylcyclohexane) were compared to evaluate the influence of the ring size (C5 vs C6) and number (1 vs 2). The numerous reaction products were identified, quantified and classified by using two-dimensional gas chromatography (GC × GC). In the absence of sulfur, it is confirmed that C5 rings are opened faster than C6 rings, and that single-ring naphthenes are converted faster than double-ring naphthenes. The presence of H2S, even at concentrations as low as 30 ppm, drastically and irreversibly changes the dominant catalytic function (from metallic to acidic), mechanism (from dicarbene-mediated to carbocation rearrangement) and family of products (from ring-opening products to skeletal-isomerization products). Together with experiments at variable reactant conversion, these results allow us to propose mechanistic reaction schemes for the three naphthenes under similar conditions, both for sulfur-free and sulfur-rich atmospheres.
Synthesis of high quality colloidal Cerium(III) doped yttrium aluminum garnet (Y3Al5O12:Ce3+, “YAG:Ce”) nanoparticles (NPs) meeting simultaneously both ultra‐small size and high photoluminescence ...(PL) performance is challenging, as generally a particle size/PL trade‐off has been observed for this type of nanomaterials. The glycothermal route is capable to yield ultra‐fine crystalline colloidal YAG:Ce nanoparticles with a particle size as small as 10 nm but with quantum yield (QY) no more than 20%. In this paper, the first ultra‐small YPO4‐YAG:Ce nanocomposite phosphor particles having an exceptional QY‐to‐size performance with an QY up to 53% while maintaining the particle size ≈10 nm is reported. The NPs are produced via a phosphoric acid‐ and extra yttrium acetate‐assisted glycothermal synthesis route. Localization of phosphate and extra yttrium entities with respect to cerium centers in the YAG host has been determined by fine structural analysis techniques such as X‐ray diffration (XRD), solid state nuclear magnetic resonance (NMR), and high resolution scanning transmission electron microscopy (HR‐STEM), and shows distinct YPO4 and YAG phases. Finally, a correlation between the additive‐induced physico‐chemical environment change around cerium centers and the increasing PL performance has been suggested based on electron paramagnetic resonance (EPR), X‐ray photoelectron spectrometry (XPS) data, and crystallographic simulation studies.
The ultra‐small YPO4‐YAG:Ce nanocomposite phosphor particles having an exceptional quantum yield (QY)‐to‐size performance with an QY up to 53% while maintaining the particle size ≈10 nm have been synthesized. Distribution of P/extra Y entities played un essential role on the optic property and morphology of the material.
Dinuclear transition metal complexes with direct metal-metal interactions have the potential to generate unique reactivities and properties. Using asymmetric triazine ligands HN
BuR (R = Et,
Pr,
Bu) ...featuring different alkyl substituents at 1,3-N centers, we report here the first rational synthesis of 'tetragonal lantern' type Fe(II) triazenides Fe
(N
BuR)
R = Et (1),
Pr (2),
Bu (3) having an exceptionally short Fe-Fe distance (2.167-2.174 Å). Unlike the previously reported lantern structures with related amidinate or guanidinate ligands, highly air-sensitive 1-3 show a lower spin ground state, as indicated by Mössbauer,
H NMR and DFT studies.
Global energy demand and environmental concerns about limiting CO2 emissions have been growing recently. This is why fuel production from renewable resources has become a priority. In this context, ...microalgae represent an attractive alternative carbon source. In this work, different supported catalysts, including metal phosphide, nitride, and sulfide, were tested for the hydroconversion of bio‐oil issued from the hydrothermal liquefaction of microalgae. Supported Ni phosphide catalysts promoted the decarboxylation and decarbonylation route, while NiMo nitride promoted the hydrodeoxygenation pathway. NiW sulfide catalysts were the most performant, producing a hydrotreated oil with the best higher heating value (HHV), lower aromaticity degree, and lower average molar mass. Among sulfide catalysts, NiWS/SiO2−Al2O3 was the least active, probably due to the inhibition of acid sites by the nitrogen compounds. However, NiWS/Al2O3 performed better, showing high hydrogenation performances, which contributed to the conversion of refractory compounds.
Supported metal phosphide, nitride, and sulfide catalysts were compared for the hydroconversion of algal oil. Nickel phosphide catalysts promoted the decarboxylation/decarbonylation route for the conversion of carboxylic acids, while NiMo nitride catalysts promoted the hydrodeoxygenation pathway. NiWS/Al2O3 sulfide was the best catalyst resulting in a hydrotreated oil with lower heteroatom content and average molar mass that felt primary in the diesel range.
After extraction of high-added value components of Spirulina sp., the remaining residues can be valorized by hydrothermal liquefaction to produce an oily water insoluble viscous phase (biocrude) ...which is very similar to petroleum bitumen. This hydrophobic fraction is composed of various N-,O-containing cyclic compounds, fatty acids, amides, nitriles, alkenes and alkanes. In order to optimize the rheological properties of the biocrude, we studied the addition of different catalysts with various loadings: ZrO2 or CeO2, or Ce(NO3)3.6H2O as well as the effect of residence time during HTL. The biocrude has been systematically characterized by GCxGC, GPC, elemental analyses and dynamic shear rheology and compared to a petroleum bitumen. The different catalysts tested had little influence on the composition of the HTL hydrophobic fraction in the chosen operating conditions. In contrast, increasing the reaction time (from 1 to 7 h) was found to promote condensation reactions, thereby increasing the average molecular weight of the biocrude, leading to a viscoelastic material very similar to a petroleum bitumen.
1.Valorization of microalgae residues by catalytic HTL2.Various catalytic system were compared (homogeneous and heterogeneous)3.GPC, GCxGC-MS, elemental analysis were carried out on the biocrude4.Bio-binder similar to petroleum one assessed by rheological characterization5.Bio-bitumen rheology is strongly affected by the time of HTL
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