Efficient deoxygenation of waste cooking oil over Co3O4–La2O3-doped activated carbon for the production of diesel-like fuel

Untreated waste cooking oil (WCO) with significant levels of water and fatty acids (FFAs) was deoxygenated over Co₃O₄–La₂O₃/AC_nano catalysts under an inert flow of N₂ in a micro-batch closed system for the production of green diesel. The primary reaction mechanism was found to be the decarbonylation/decarboxylation (deCOx) pathway in the Co₃O₄–La₂O₃/AC_nano-catalyzed reaction. The effect of cobalt doping, catalyst loading, different deoxygenation (DO) systems, temperature and time were investigated. The results indicated that among the various cobalt doping levels (between 5 and 25 wt%), the maximum catalytic activity was exhibited with the Co : La ratio of 20 : 20 wt/wt% DO under N₂ flow, which yielded 58% hydrocarbons with majority diesel-range (n-(C₁₅ + C₁₇)) selectivity (∼63%), using 3 wt% catalyst loading at a temperature of 350 °C within 180 min. Interestingly, 1 wt% of catalyst in the micro-batch closed system yielded 96% hydrocarbons with 93% n-(C₁₅ + C₁₇) selectivity within 60 min at 330 °C, 38.4 wt% FFA and 5% water content. An examination of the WCO under a series of FFA (0–20%) and water contents (0.5–20 wt%) indicated an enhanced yield of green diesel, and increased involvement of the deCOx mechanism. A high water content was found to increase the decomposition of triglycerides into FFAs and promote the DO reaction. The present work demonstrates that WCO with significant levels of water and FFAs generated by the food industry can provide an economical and naturally replenished raw material for the production of diesel.

Untreated waste cooking oil (WCO) with significant levels of water and fatty acids (FFAs) was deoxygenated over Co₃O₄–La₂O₃/AC_nano catalysts under an inert flow of N₂ in a micro-batch closed system for the production of green diesel.     

Chemoselective decarboxylation of ceiba oil to diesel-range alkanes over a red mud based catalyst under H2-free conditions

Concerns over global greenhouse gas emissions such as CO_x and NO_x as well as the depletion of petroleum fossil resources have motivated humankind to seek an alternative energy source known as green diesel. In this study, green diesel was produced via a deoxygenation (DO) reaction of ceiba oil under a H₂-free atmosphere over Ni modified red mud-based catalysts, which have been synthesized via a precipitation – deep-deposition assisted autoclave method. The obtained catalyst was further characterized by XRF, XRD, BET, FTIR, TPD-NH₃, FESEM, and TGA. Based on the catalytic activity test, all Ni/RMO_x catalysts facilitated greater DO activity by yielding 83–86% hydrocarbon yield and 70–85% saturated diesel n-(C₁₅ + C₁₇) selectivity. Ni/RMO₃ was the best catalyst for deoxygenizing the ceiba oil owing to the existence of a high acidic strength (12717.3 μmol g⁻¹) and synergistic interaction between Fe–O and Ni–O species, thereby producing the highest hydrocarbon yield (86%) and n-(C₁₅ + C₁₇) selectivity (85%). According to the reusability study, the Ni/RMO₃ could be reused for up to six consecutive runs with hydrocarbon yields ranging from 53% to 83% and n-(C₁₅ + C₁₇) selectivity ranging from 62% to 83%.

Concerns over global greenhouse gas emissions such as CO_x and NO_x as well as the depletion of petroleum fossil resources have motivated humankind to seek an alternative energy source known as green diesel.     

Production of green diesel from catalytic deoxygenation of chicken fat oil over a series binary metal oxide-supported MWCNTs

Deoxygenation processes that exploit milder reaction conditions under H₂-free atmospheres appear environmentally and economically effective for the production of green diesel. Herein, green diesel was produced by catalytic deoxygenation of chicken fat oil (CFO) over oxides of binary metal pairs (Ni–Mg, Ni–Mn, Ni–Cu, Ni–Ce) supported on multi-walled carbon nanotubes (MWCNTs). The presence of Mg and Mn with Ni afforded greater deoxygenation activity, with hydrocarbon yields of >75% and n-(C₁₅ + C₁₇) selectivity of >81%, indicating that decarboxylation/decarbonylation (deCOx) of CFO is favoured by the existence of high amount of lower strength strong acidic sites along with noticeable strongly basic sites. Based on a series of studies of different Mg and Mn dosages (5–20 wt%), the oxygen free-rich diesel-range hydrocarbons produced efficiently by Ni₁₀–Mg₁₅/MWCNT and Ni₁₀–Mn₅/MWCNT catalysts yielded >84% of hydrocarbons, with n-(C₁₅ + C₁₇) selectivity of >85%. The heating value of the green diesel obtained complied with the ultra-low sulphur diesel standard.

Deoxygenation processes that exploit milder reaction conditions under H₂-free atmospheres appear environmentally and economically effective for the production of green diesel.     

Catalytic deoxygenation of palm oil over metal phosphides supported on palm fiber waste derived activated biochar for producing green diesel fuel

Palm oil conversion into green diesel by catalytic deoxygenation (DO) is one of the distinctive research topics in biorefinery towards a bio-circular-green economic model to reduce the greenhouse gas emissions. In this study, palm fiber waste was explored as an alternative precursor for the preparation of activated biochar as a support material. A new series of nickel phosphide (Ni–P) and iron phosphide (Fe–P) catalysts supported on palm fiber activated biochar (PFAC) was synthesized by wetness impregnation, and extensive characterization was performed by several techniques to understand the characteristics of the supported metal phosphide catalysts prior to palm oil deoxygenation for producing of green diesel (C₁₅–C₁₈ hydrocarbons). The PFAC support exhibited suitable physicochemical properties for catalyst preparation, such as high carbon content, and high porosity (S_BET of 1039.64 m² g⁻¹ with V_T of 0.572 cm³ g⁻¹). The high porosity of the catalyst support (PFAC) significantly promotes the metal phosphide nanoparticle dispersion. The DO of palm oil was tested in a trickle bed down flow reactor under hydrogen atmosphere. The outstanding catalytic performance of supported Ni–P and Fe–P catalysts provided an impressive liquid hydrocarbon yield between 63.37 and 79.65% with the highest green diesel selectivity of 62.64%. Decarbonylation (DCO) and decarboxylation (DCO₂) are the main pathways for the relative phosphide catalysts as presented by the high number of C_n−1 atoms (C₁₅ and C₁₇ hydrocarbons). In addition, metal phosphide/PFAC catalysts could achieve great potential application as a promising alternative catalyst for biofuel production via deoxygenation for large-scale operation owing to their excellent catalytic activity, simple preparation, and utilization of sustainable resources.

Palm oil deoxygenation over palm fiber activated biochar supported metal phosphide catalysts.     

Efficiency of liquid tin(ii) n-alkoxide initiators in the ring-opening polymerization of l-lactide: kinetic studies by non-isothermal differential scanning calorimetry

Novel soluble liquid tin(ii) n-butoxide (Sn(OnC₄H₉)₂), tin(ii) n-hexoxide (Sn(OnC₆H₁₃)₂), and tin(ii) n-octoxide (Sn(OnC₈H₁₇)₂) initiators were synthesized for use as coordination–insertion initiators in the bulk ring-opening polymerization (ROP) of l-lactide (LLA). In order to compare their efficiencies with the more commonly used tin(ii) 2-ethylhexanoate (stannous octoate, Sn(Oct)₂) and conventional tin(ii) octoate/n-alcohol (SnOct₂/nROH) initiating systems, kinetic parameters derived from monomer conversion data were obtained from non-isothermal differential scanning calorimetry (DSC). In this work, the three non-isothermal DSC kinetic approaches including dynamic (Kissinger, Flynn–Wall, and Ozawa); isoconversional (Friedman, Kissinger–Akahira–Sunose (KAS) and Ozawa–Flynn–Wall (OFW)); and Borchardt and Daniels (B/D) methods of data analysis were compared. The kinetic results showed that, under the same conditions, the rate of polymerization for the 7 initiators/initiating systems was in the order of liquid Sn(OnC₄H₉)₂ > Sn(Oct)₂/nC₄H₉OH > Sn(Oct)₂ ≅ liquid Sn(OnC₆H₁₃)₂ > Sn(Oct)₂/nC₆H₁₃OH ≅ liquid Sn(OnC₈H₁₇)₂ > Sn(Oct)₂/nC₈H₁₇OH. The lowest activation energies (E_a = 52, 59, and 56 kJ mol⁻¹ for the Kissinger, Flynn–Wall, and Ozawa dynamic methods; E_a = 53–60, 55–58, and 60–62 kJ mol⁻¹ for the Friedman, KAS, and OFW isoconversional methods; and E_a = 76–84 kJ mol⁻¹ for the B/D) were found in the polymerizations using the novel liquid Sn(OnC₄H₉)₂ as the initiator, thereby showing it to be the most efficient initiator in the ROP of l-lactide.

The efficiency of homogeneous liquid tin(ii) n-alkoxide initiators in the ROP of l-lactide was reported in this work by non-isothermal DSC kinetic approaches.     

Production of green biofuel by using a goat manure supported Ni–Al hydrotalcite catalysed deoxygenation process

The high oxygen content in natural biomass resources, such as vegetable oil or biomass-pyrolysed bio oil, is the main constraint in their implementation as a full-scale biofuel for the automotive industry. In the present study, renewable fuel with petrodiesel-like properties was produced via catalytic deoxygenation of oleic acid in the absence of hydrogen (H₂). The deoxygenation pathway of oleic acid to bio-hydrocarbon involves decarboxylation/decarbonylation of the oxygen content from the fatty acid structure in the form of carbon dioxide (CO₂)/carbon monoxide (CO), with the presence of a goat manure supported Ni–Al hydrotalcite (Gm/Ni–Al) catalyst. Goat manure is an abundant bio-waste, containing a high mineral content, urea as well as cellulosic fiber of plants, which is potentially converted into activated carbon. Synthesis of Gm/Ni–Al was carried out by incorporation of pre-activated goat manure (GmA) during co-precipitation of Ni–Al catalyst with 1 : 3, 1 : 1 and 3 : 1 ratios. The physico-chemical properties of the catalysts were characterized by X-ray diffractometry (XRD), Brunauer–Emmet–Teller (BET) surface area, field emission surface electron microscopy (FESEM) and temperature program desorption ammonia (TPD-NH₃) analysers. The catalytic deoxygenation reaction was performed in a batch reactor and the product obtained was characterized by using gas chromatography-mass spectroscopy (GCMS) for compound composition identification as well as gas chromatography-flame ionisation detector (GC-FID) for yield and selectivity determination. The optimization and evaluation were executed using response surface methodology (RSM) in conjunction with central composite design (CCD) with 5-level-3-factors. From the RSM reaction model, it was found that the Gm/Ni–Al 1 : 1 catalysed deoxygenation reaction gives the optimum product yield of 97.9% of hydrocarbon in the range of C₈–C₂₀, with diesel selectivity (C₁₇: heptadecane and heptadecene compounds) of 63.7% at the optimal reaction conditions of: (1) reaction temperature: 327.14 °C, (2) reaction time: 1 h, and (3) catalyst amount: 5 wt%.

Deoxygenation pathway of oleic acid to bio-hydrocarbon involves decarboxylation/decarbonylation of oxygen content from fatty acid structure in the form of carbon dioxide (CO₂)/carbon monoxide (CO), respectively, with the presence of goat manure supported Ni–Al hydrotalcite (Gm/Ni–Al) catalyst.     

Impacts of octanol and decanol addition on the solubility of methanol/hydrous methanol/diesel/biodiesel/Jet A-1 fuel ternary mixtures

This study attempts to enhance the mixture instability of methanol/hydrous methanol mixed with diesel fuel, waste cooking oil (WCO) biodiesel, and Jet A-1 fuel using n-octanol and n-decanol as cosolvent at numerous temperatures of 10 °C, 20 °C, and 30 °C. The experiment is divided into two stages: first, blending pure methanol with diesel oil, Jet A-1, and WCO biodiesel individually utilizing n-octanol and n-decanol as cosolvent at various temperatures. Second, combining hydrous methanol (90% methanol + 10 wt% water) with diesel oil, Jet A-1, and WCO biodiesel independently and applying n-octanol and n-decanol as cosolvent at different temperatures. Pure methanol or hydrous methanol is mixed with the base fuels at different mixing proportions varying from 0 to 100 vol% with 10 vol% increments. The co-solvent, mainly n-octanol and n-decanol (titrant), is progressively and separately inserted into the tube with continuous shaking by utilizing a high-precision pipette until the ternary mixtures'' phase borders seem. The findings demonstrate phase separation in pure methanol–diesel and pure methanol–Jet A-1 combinations even when the blend temperature increased to 60 °C. The pure methanol/biodiesel combination proves complete solubility without adding an external agent. The results also illustrate that the ambient temperature considerably affects the stability of mixture and amount of cosolvent in the blend. n-Octanol and n-decanol showed promising performance in enhancing the phase stability issue of methanol and hydrous methanol with the base fuels. It can be deduced that the minimum amount of cosolvent is recorded for biodiesel–hydrous methanol, Jet A-1–hydrous methanol, and diesel–hydrous methanol, respectively.

This study attempts to enhance the mixture instability of methanol/hydrous methanol mixed with diesel fuel, waste cooking oil biodiesel, and Jet A-1 fuel using n-octanol and n-decanol as cosolvent at numerous temperatures of 10 °C, 20 °C, and 30 °C.     

Acid–base sites synergistic catalysis over Mg–Zr–Al mixed metal oxide toward synthesis of diethyl carbonate

In heterogeneous catalysis processes, development of high-performance acid–base sites synergistic catalysis has drawn increasing attention. In this work, we prepared Mg/Zr/Al mixed metal oxides (denoted as Mg₂Zr_xAl_1−x–MMO) derived from Mg–Zr–Al layered double hydroxides (LDHs) precursors. Their catalytic performance toward the synthesis of diethyl carbonate (DEC) from urea and ethanol was studied in detail, and the highest catalytic activity was obtained over the Mg₂Zr_0.53Al_0.47MMO catalyst (DEC yield: 37.6%). By establishing correlation between the catalytic performance and Lewis acid–base sites measured by NH₃-TPD and CO₂-TPD, it is found that both weak acid site and medium strength base site contribute to the overall yield of DEC, which demonstrates an acid–base synergistic catalysis in this reaction. In addition, in situ Fourier transform infrared spectroscopy (in situ FTIR) measurements reveal that the Lewis base site activates ethanol to give ethoxide species; while Lewis acid site facilitates the activated adsorption of urea and the intermediate ethyl carbamate (EC). Therefore, this work provides an effective method for the preparation of tunable acid–base catalysts based on LDHs precursor approach, which can be potentially used in cooperative acid–base catalysis reaction.

Mg/Zr/Al mixed metal oxides were prepared via a facile phase transformation process of hydrotalcite precursors, which showed acid–base sites synergistic catalytic performance toward the synthesis of diethyl carbonate from ethanol and urea.     

Synthesis,surface activities,and aggregation behavior of phenyl-containing carboxybetaine surfactants

A series of carboxybetaine surfactants, 2-((4-(alkoxy)-3,5-dimethylbenzyl)dimethyl-ammonio)acetate (C_nOBCb, where n represents the hydrocarbon chain length of 12, 14, 16 and 18), were synthesized by an efficient and high-yield route for the first time. The surface activities and aggregation behavior of C_nOBCb in aqueous solution were investigated by equilibrium surface tension, interfacial tension, steady-state fluorescence, dynamic light scattering (DLS), cryogenic transmission electron microscopy (cryo-TEM) and negative-staining transmission electron microscopy (TEM) measurements. In comparison with conventional N-alkylbetaine surfactants (C_nCb), the C_nOBCb species, with a phenyl group introduced in the hydrophobic tail, exhibited excellent surface activities, including lower critical micelle concentration (cmc), lower surface tension and stronger adsorption tendency at an air/water interface. C_nOBCb also displayed high efficiency in reducing the toluene/water interfacial tension, with C₁₂OBCb achieving an ultralow interfacial tension (10⁻³ mN m⁻¹) at concentrations from 0.2 to 1 mmol dm⁻³. The fluorescence intensity ratio and the scattering intensity in DLS measurements changed remarkably at concentrations around the cmc. Furthermore, the C_nOBCb species spontaneously formed vesicles above the cmc in aqueous solution, and the size of the aggregates increased with increasing surfactant concentrations. Flooding experiments showed that C_nOBCb could effectively improve oil recovery by 7.85–10.55%.

A novel series of carboxybetaine surfactants were synthesized for the first time and their physicochemical properties were systematically investigated.     

Donor–acceptor duality of the transition-metal-like B2 core in core–shell-like metallo-borospherenes La3&[B2@B17]− and La3&[B2@B18]−

Transition-metal doping induces dramatic structural changes and leads to earlier planar → tubular → spherical → core–shell-like structural transitions in boron clusters. Inspired by the newly discovered spherical trihedral metallo-borospherene D_3h La₃&B₁₈⁻ (1) (Chen, et al., Nat. Commun., 2020, 11, 2766) and based on extensive first-principles theory calculations, we predict herein the first and smallest core–shell-like metallo-borospherenes C_2v La₃&[B₂@B₁₇]⁻ (2) and D_3h La₃&[B₂@B₁₈]⁻ (3) which contain a transition-metal-like B₂ core at the cage center with unique donor–acceptor duality in La₃&B_n⁻ spherical trihedral shells (n = 17, 18). Detailed energy decomposition and bonding analyses indicate that the B₂ core in these novel complexes serves as a π-donor in the equatorial direction mainly to coordinate three La atoms on the waist and a π/σ-acceptor in the axial direction mainly coordinated by two B₆ triangles on the top and bottom. These highly stable core–shell complexes appear to be spherically aromatic in nature in bonding patterns. The IR, Raman, and photoelectron spectra of 2 and 3 are computationally simulated to facilitate their spectroscopic characterizations.

The smallest core–shell-like metallo-borospherenes C_2v La3&[B₂@B₁₇]⁻ and D_3h La₃&[B₂@B₁₈]⁻ have been predicted at first-principles theory level which contain a transition-metal-like B₂ core with unique donor–acceptor duality.     

Synthesis and pH-stimuli responsive research of gemini amine-oxide surfactants containing amides

The series of gemini amine-oxide surfactants with the formula C_nH_2n+1CONH(CH₂)₂N⁺O⁻(CH₃)–(CH₂)₃–(CH₃)N⁺O⁻(CH₂)₂NHCOC_nH_2n+1 (n = 11, 13, 15, and 17) has been synthesized successfully. Their isoelectric point and acid dissociation constant were measured to determine the ionization form of the surfactant molecules in aqueous solution within different pH values. The studies showed that the length of the hydrophobic alkyl chains had a great influence on the pH-stimuli responsive behavior of these surfactants. When n ≤ 13 (n-3-n-OA), the regularity of the pH-stimuli responsive behavior of the surfactant solutions was relatively consistent, while the surfactants with longer hydrophobic alkyl chain lengths lost this regularity (n ≥ 15). In addition, vesicles were observed in most of these surfactant aqueous solutions, with the exception of 11-3-11-OA. Moreover, the obvious flocculation phenomenon was observed within the range of pH 4–5, and they flocculated rapidly when they approached their isoelectric points. This process was reversible, which brought more possibilities for their application in drug delivery and release.

The series of gemini amine-oxide surfactants with the formula C_nH_2n+1CONH(CH₂)₂N⁺O^–(CH₃)–(CH₂)₃–(CH₃)N⁺O^– (CH₂)₂NHCOC_nH_2n+1 (n = 11, 13, 15, and 17) have been synthesized, and their pH-stimuli responsive behavior in aqueous solution has been studied.     

Lewis acid Ni/Al-MCM-41 catalysts for H2-free deoxygenation of Reutealis trisperma oil to biofuels

The activity of mesoporous Al-MCM-41 for deoxygenation of Reutealis trisperma oil (RTO) was enhanced via modification with NiO nanoparticles. Deoxygenation at atmospheric pressure and under H₂ free conditions required acid catalysts to ensure the removal of the oxygenated fragments in triglycerides to form liquid hydrocarbons. NiO at different weight loadings was impregnated onto Al-MCM-41 and the changes of Lewis/Brønsted acidity and mesoporosity of the catalysts were investigated. The activity of Al-MCM-41 was enhanced when impregnated with NiO due to the increase of Lewis acidity originating from NiO nanoparticles and the mesoporosity of Al-MCM-41. Increasing the NiO loading enhanced the Lewis acidity but not Brønsted acidity, leading to a higher conversion towards liquid hydrocarbon yield. Impregnation with 10% of NiO on Al-MCM-41 increased the conversion of RTO to hydrocarbons via the deoxygenation pathway and reduced the products from cracking reaction, consequently enhancing the green diesel (C11–C18) hydrocarbon products.

The activity of mesoporous Al-MCM-41 for deoxygenation of Reutealis trisperma oil (RTO) was enhanced via modification with NiO nanoparticles.     

Influence of cerium doping on Cu–Ni/activated carbon low-temperature CO-SCR denitration catalysts

In this study, to evaluate the effects of two methods for activation of nitric acid, air thermal oxidation and Ce doping were applied to a Cu–Ni/activated carbon (AC) low-temperature CO-SCR denitration catalyst. The Cu–Ni–Ce/AC_0,1 catalyst was prepared using the ultrasonic equal volume impregnation method. The physical and chemical structures of Cu–Ni–Ce/AC_0,1 were studied using scanning electron microscopy, Brunauer–Emmett–Teller analysis, Fourier-transform infrared spectroscopy, X-ray diffractometry, X-ray photoelectron spectroscopy, CO-temperature programmed desorption (TPD) and NO-TPD characterisation techniques. It was found that the denitration efficiency of 6Cu–4Ni–5Ce/AC₁ can reach 99.8% at a denitration temperature of 150 °C, a GHSV of 30 000 h⁻¹ and 5% O₂. Although the specific surface area of the AC activated by nitric acid was slightly lower than that activated by air thermal oxidation, the pore structure of the AC activated by nitric acid was more developed, and the number of acidic oxygen-containing functional groups was significantly increased. Ce metal ions were inserted into the graphite microcrystalline structure of AC, splitting it into smaller graphene fragments, whereby the dispersibility of Cu and Ni was improved. In addition, many reaction units were formed on the catalyst surface, which could adsorb more CO and NO reaction gases. With the increase in Ce doping, the relative proportions of Cu²⁺/Cuⁿ⁺, Ni³⁺/Niⁿ⁺ and surface adsorbed oxygen (Oα) in the Cu–Ni–Ce/AC_0,1 catalyst increased. In addition, after the introduction of Ce into Cu–Ni/AC, the amount of weak and medium acids significantly increased. This may be due to the Ce species or its influence on the Cu/Ni species. Further, the active sites of the acid were more exposed. According to the results of the study, a composite metal oxide CO-SCR denitration mechanism is proposed. Through the oxidation–reduction reaction between the metals, the reaction gas of CO and NO is adsorbed and the incoming O₂ is converted into (Oα), which promotes the conversion of NO into NO₂. The CO-SCR reaction is accelerated, and the rate of low-temperature denitration was increased. Overall, the results of this study will provide theoretical support for the research and development of low-temperature denitration catalysts for sintering flue gas in iron and steel enterprises.

In the process of denitrification, the reaction between NO and CO (NO + CO → N₂ + CO₂) occurs. There will be a redox reaction between copper, nickel and cerium (Cu²⁺ + Ce³⁺ → Cu⁺ + Ce⁴⁺, Ni³⁺ + Ce³⁺ → Ni²⁺ + Ce⁴⁺).     

Interaction of oxalic acid with methylamine and its atmospheric implications

Oxalic acid, which is one of the most common dicarboxylic acids, is expected to be an important component of atmospheric aerosols. However, the contribution of oxalic acid to the generation of new particles is still poorly understood. In this study, the structural characteristics and thermodynamics of (C₂H₂O₄)(CH₃NH₂)_n (n = 1–4) were investigated at the PW91PW91/6-311++G(3df,3pd) level of theory. We found that clusters formed by oxalic acid and methylamine are relatively stable, and the more the atoms participating in the formation of a ring-like structure, the more stable is the cluster. In addition, via the analysis of atmospheric relevance, it can be revealed that clusters of (C₂H₂O₄)(CH₃NH₂)_n (n = 1–4) have a noteworthy concentration in the atmosphere, which indicates that these clusters could be participating in new particle formation. Moreover, by comparison with (H₂C₂O₄)(NH₃)_n (n = 1–6) species, it can be seen that oxalic acid is more readily bound to methylamine than to ammonia, which promotes nucleation or new particle formation. Finally, the Rayleigh scattering properties of clusters of (C₂H₂O₄)(CH₃NH₂)_n (n = 1–4) were investigated for the first time to determine their atmospheric implications.

Oxalic acid, which is one of the most common dicarboxylic acids, is expected to be an important component of atmospheric aerosols.     

Synthesis and characterization of MOFs constructed from 5-(benzimidazole-1-yl)isophthalic acid and highly selective fluorescence detection of Fe(iii) and Cr(vi) in water

In this work, four novel metal–organic frameworks [Cd(bipa)]_n (1), {[Zn₂(bipa)₂]·2C₂H₅OH}_n (2), {[Co(bipa)]·C₂H₅OH}_n (3), {[Ni(bipa)₂]·2DMA}_n (4), (H₂bipa = 5-(benzimidazole-1-yl)isophthalic acid) were successfully synthesized under solvothermal conditions. Complexes 1–4 were characterized by powder X-ray diffraction, elemental analysis, infrared spectroscopy and thermogravimetric analysis. Interestingly, the coordination patterns and 3D network structures of complexes 1–3 are very similar, while complex 4 is relatively unique. Complexes 1–2 exhibit potential fluorescent properties. Complex 1 can selectively and sensitively detect trace Fe(iii) and Cr(vi) in water by fluorescence quenching detection, and the quenching mechanism is further discussed.

In this work, four novel MOFs [Cd(bipa)]_n (1), {[Zn₂(bipa)₂]·2C₂H₅OH}_n (2), {[Co(bipa)]·C₂H₅OH}_n (3), {[Ni(bipa)₂]·2DMA}_n (4), (H₂bipa = 5-(benzimidazole-1-yl)isophthalic acid) were successfully synthesized under solvothermal conditions.     

Catalytic effect of (H2O)n (n = 1–3) on the HO2 + NH2 → NH3 + 3O2 reaction under tropospheric conditions

The effects of (H₂O)_n (n = 1–3) clusters on the HO₂ + NH₂ → NH₃ + ³O₂ reaction have been investigated by employing high-level quantum chemical calculations with M06-2X and CCSD(T) theoretical methods, and canonical variational transition (CVT) state theory with small curvature tunneling (SCT) correction. The calculated results show that two kinds of reaction, HO₂⋯(H₂O)_n (n = 1–3) + NH₂ and H₂N⋯(H₂O)_n (n = 1–3) + HO₂, are involved in the (H₂O)_n (n = 1–3) catalyzed HO₂ + NH₂ → NH₃ + ³O₂ reaction. Due to the fact that HO₂⋯(H₂O)_n (n = 1–3) complexes have much larger stabilization energies and much higher concentrations than the corresponding complexes of H₂N⋯(H₂O)_n (n = 1–3), the atmospheric relevance of the former reaction is more obvious with its effective rate constant of about 1–11 orders of magnitude faster than the corresponding latter reaction at 298 K. Meanwhile, due to the effective rate constant of the H₂O⋯HO₂ + NH₂ reaction being respectively larger by 5–6 and 6–7 orders of magnitude than the corresponding reactions of HO₂⋯(H₂O)₂ + NH₂ and HO₂⋯(H₂O)₃ + NH₂, the catalytic effect of (H₂O)_n (n = 1–3) is mainly taken from the contribution of the water monomer. In addition, the enhancement factor of the water monomer is 10.06–13.30% within the temperature range of 275–320 K, which shows that at whole calculated temperatures, a positive water effect is obvious under atmospheric conditions.

The catalytic effect of (H₂O)_n (n = 1−3) on the HO₂ + NH₂ → NH₃ + ³O₂ is mainly taken from the contribution of a single water vapor.     

Hydrophobics of CnTAB in an aqueous DMSO–BSA nanoemulsion for the monodispersion of flavonoids

Herein, philicphobic interactions between flavonoids (quercetin, apigenin, and naringenin) and bovine serum albumin (BSA) were analyzed using physicochemical properties obtained at T = 298.15, 303.15, 308.15 K and 0.1 MPa, from 0.01 to 0.10 mol kg⁻¹ of alkyl trimethyl ammonium bromide (C_nTAB : DTAB, C_n = 12; TDTAB, C_n = 14; HDTAB, C_n = 16). The flavonoids with cationic surfactants strongly interacted with BSA, as illustrated by the physicochemical parameters (PCPs), refractive index (n_D), Walden product, pH, electrostatic potential and molar conductance (Λ_m). Viscosity (η), density (ρ), η_D, sound velocity (u) and specific conductance (k) data were used to calculate the relative viscosity (η_r), viscous relaxation time (τ), Walden product, entropy (ΔS), enthalpy (ΔH), Gibbs free energy (ΔG), heat capacity (Δq) limiting dielectric constant (ε_∞), speed of light (C), acoustic impedance (Z) and molar refraction (R). These PCPs have quantitatively predicted the hydrophilic and hydrophobic (philicphobic) interactions developed are on increasing the alkyl chain (AC) of C_nTAB. These interactions assist a monodispersion of the flavonoids, and a similar mechanism could equally be applicable to monodisperse the antioxidants in the aqueous nanoemulsions. Their philicphobic stoichiometry weakened the cohesive forces (CF) when the shear stress was increased, and enhanced surface activities were achieved that facilitated the flavonoids to interact with BSA due to intermolecular forces (IMF) to develop a stable nanoemulsion; Upon increasing the C_nTAB concentrations, the n_D value increases since the polarizability increases with stronger shear stress due to van der Waal forces and electrostatic interactions to achieve better flavonoid–BSA linkages.

The wavy zone of flavonoid in aq-DMSO <10% DMSO predicts the kinetic energy and resultant molecular dynamics.     

Effect of the itinerant electron density on the magnetization and Curie temperature of Sr2FeMoO6 ceramics

The itinerant electron density (n) near the Fermi level has a close correlation with the physical properties of Sr₂FeMoO₆. Two series of single-phase Sr_(2−y)Na_yFeMoO₆ (y = 0.1, 0.2, 0.3) and Sr_(2−y)Na_yFe_(1−x)Mo_(1+x)O₆ (y = 2x; y = 0.1, 0.2, 0.3) ceramics were specially designed and the itinerant electron density (n) of them can be artificially controlled to be: n = 1 − y and n = 1 − y + 3x = 1 + 0.5y, respectively. The corresponding crystal structure, magnetization and the ferromagnetic Curie temperature (T_C) of two subjects were investigated systematically. The X-ray diffraction analysis indicates that Sr_(2−y)Na_yFeMoO₆ (y = 0.1, 0.2, 0.3) have comparable Fe/Mo anti-site defect (ASD) content in spite of decreased n. However, a drastically improved Fe/Mo ASD can be observed in Sr_(2−y)Na_yFe_(1−x)Mo_(1+x)O₆ (y = 2x; y = 0.1, 0.2, 0.3) caused by the intrinsic wrong occupation of normal Fe sites with excess Mo. Magnetization–magnetic field (M–H) behavior confirms that it is the Fe/Mo ASD not n that dominantly determines the magnetization properties. Interestingly, approximately when n ≤ 0.9, T_C of Sr_(2−y)Na_yFeMoO₆ (y = 0.1, 0.2, 0.3) exhibits an overall increase with decreasing n, which is contrary to the T_C response in electron-doped SFMO. Such abnormal T_C is supposed to relate with the ratio variation of n(Mo)/n(Fe). Moreover, when n ≥ 1, T_C of Sr_(2−y)Na_yFe_(1−x)Mo_(1+x)O₆ (y = 2x; y = 0.3) exhibits a considerable rise of about 75 K over that of Sr_(2−y)Na_yFe_(1−x)Mo_(1+x)O₆ (y = 2x; y = 0.1), resulting from improved n caused by introducing excess Mo into Sr_(2−y)Na_yFeMoO₆. Maybe, our work can provide an effective strategy to artificially control n and ferromagnetic T_C accordingly, and provoke further investigation on the FeMo-baseddouble perovskites.

T _C of C6 exhibits a significant rise of 75 K over that of C2, resulting from introducing excess Mo in Sr_(2−y)Na_yFe_(1−x)Mo_(1+x)O₆.     

Synergic effects between boron and nitrogen atoms in BN-codoped C59−nBNn fullerenes (n = 1–3) for metal-free reduction of greenhouse N2O gas

The geometries, electronic structures, and catalytic properties of BN-codoped fullerenes C_59−nBN_n (n = 1–3) are studied using first-principles computations. The results showed that BN-codoping can significantly modify the properties of C₆₀ fullerene by breaking local charge neutrality and creating active sites. The codoping of B and N enhances the formation energy of fullerenes, indicating that the synergistic effects of these atoms helps to stabilize the C_59−nBN_n structures. The stepwise addition of N atoms around the B atom improves catalytic activities of C_59−nBN_n in N₂O reduction. The reduction of N₂O over C₅₈BN and C₅₇BN₂ begins with its chemisorption on the B–C bond of the fullerene, followed by the concerted interaction of CO with N₂O and the release of N₂. The resulting OCO intermediate is subsequently transformed into a CO₂ molecule, which is weakly adsorbed on the B atom of the fullerene. On the contrary, nitrogen-rich C₅₆BN₃ fullerene is found to decompose N₂O into N₂ and O* species without the requirement for activation energy. The CO molecule then removes the O* species with a low activation barrier. The activation barrier of the N₂O reduction on C₅₆BN₃ fullerene is just 0.28 eV, which is lower than that of noble metals.

The synergic effects between B and N atoms make C₅₇BN₂ and C₅₆BN₃ highly active catalysts for reduction of greenhouse N₂O gas.     

Stabilization of beryllium-containing planar pentacoordinate carbon species through attaching hydrogen atoms

The diagonal relationship between beryllium and aluminum and the isoelectronic relationship between BeH unit and Al atom were utilized to design nine new planar and quasi-planar pentacoordinate carbon (ppC) species CAl_nBe_mH_x^q (n + m = 5, q = 0, ±1, x = q + m − 1) (1a–9a) by attaching H atoms onto the Be atoms in CAl₄Be, CAl₃Be₂⁻, CAl₂Be₃²⁻, and CAlBe₄³⁻. These ppC species are σ and π double aromatic. In comparison with their parents, these H-attached molecules are more stable electronically, as can be reflected by the more favourable alternative negative–positive–negative charge-arranging pattern and the less dispersed peripheral orbitals. Remarkably, seven of these nine molecules are global energy minima, in which four of them are kinetically stable, including CAl₃Be₂H (2a), CAl₂Be₃H⁻ (4a), CAl₂Be₃H₂ (5a), and CAlBe₄H₄⁺ (9a). They are the promising target for the experimental realization of species with a ppC.

The destabilization issues, like high charges, small HOMO–LUMO gaps, and dispersed MOs, etc. can be eliminated via attaching hydrogen atoms.

Planar hypercoordinate carbon chemistry can be dated back to 1968 when Monkhorst proposed the first planar tetracoordinate carbon (ptC) in a transition state structure.¹ In 1970, Hoffmann and co-workers sponsored the project of stabilizing the ptC in equilibrium structure.² After the proposal of first ptC energy minimum 1,1-dilithiocyclopropane (C₃H₄Li₂) by Schleyer and Pople group in 1976,³ the most significant advance has been the conceptual extension of ptC to planar pentacoordinate or hexacoordinate carbon (ppC or phC),⁴ which promoted the extension of the number of planar coordination to values as high as ten and the central planar hypercoordinate atom from carbon to other main group elements or even transition metals.⁵ Nevertheless, the ppC are the most witnessed in all these extended type of structures,⁶ possibly due to the geometrically nice fit between the peripheral ligand atoms and center carbon and the electronically easy satisfaction of the 18 electron (18e) rule.In 2001, Wang and Schleyer reported a family of ppC-containing molecules, i.e. the milestone “hyparenes”, which were designed by substituting the –(CH)_n– moieties in aromatic or even anti-aromatic hydrocarbons with ppC building blocks –C₃B₃–, –C₂B₄–, and –CB₅–.^4b Subsequently, ppC species such as CCu₅H₅,⁷ CBe₅ and CBe₅⁴⁻,⁸ wheel-like C₂B₈, C₃B₉³⁺ and C₅B₁₁^+ 9 were also proposed. However, it is still unknown to date whether these small ppC clusters are global minima on their potential energy surfaces. Hence, people cannot evaluate their experimental viability. Nonetheless, situation changed when Zeng and Schleyer group reported the first ppC global minimum D_5h CAl₅⁺ in 2008, which features not only the 18e structure, but also the σ and π double aromaticity.¹⁰ Taking CAl₅⁺ as the seed structure and considering the periodicity as well as the diagonal relationship, etc., people had designed a series isoelectronic ppC structures, including CAl_nBe_m^1−m (m = 1–3),¹¹ CAl₄E⁺ (E = Al, Ga, In, Tl),¹² CBe₅E⁻ (E = Al, Ga, In, Tl),¹³ CAl₄TmX₂ (Tm = Ti, Zr, Hf; X = F, Cl, Br, I, and cyclopentadienyl anion),¹⁴ and CGa_nBe_m^1−m (n + m = 5, m = 1–4).¹⁵During the design of these species, when each Al or its heavier congeners was replaced by a Be atom, a negative charge was added to maintain the isoelectronic relationship. However, it would be hard to experimentally realize such ppC structures due to the high molecular charges and the exposure of the electron deficient metal atoms. As a result, people had tried to stabilize the highly negatively charged ppC ions through attaching the certain number of auxiliary atoms. For example, H atoms had been attached to CAl₄⁻ and CAl₄²⁻ in a joint experimental-theoretical study, leading to the new ptC species CAl₄H and CAl₄H⁻.¹⁶ For ppC species, the most studied seed structure should be CBe₅⁴⁻,⁸ which is even not an eligible minimum.¹⁷ Nevertheless, through attaching the auxiliary atoms, like alkali metals, hydrogen, halogens, and even transition metal gold, a family of ppC species can be designed, including CBe₅Li_nⁿ⁻⁴ (n = 1–5),^17a CBe₅H_nⁿ⁻⁴ (n = 2, 3, 5),^17b CBe₅E₅⁺ (E = F, Cl, Br, Li, Na, K),¹⁸ and CBe₅Au_nⁿ⁻⁴ (n = 2–5).¹⁹ In these ppC species, the auxiliary atoms play the roles of both compensating the deficient electrons and reducing the high negatively charges. Remarkably, H atoms were also employed to stabilize the ppC-containing C–Be double chain nanoribbon, where its CBe₅H₂ ppC unit possesses the similar electronic structures to that of CAl₅⁺.²⁰Very recently, using Li atoms to balance the high negative charge of Be-doped ppC structures results in neutral or mono-anionic species [(CAl₂Be₃)Li]^− 11b and CGa_nBe_mLi_m−1 (n + m = 5, m = 1–4),¹⁵ where Li atoms generally show high affinity to Be atoms. In addition, our recent study revealed that Be and H can be bounded together through favourable covalent and ionic bonding,^5c,21 thus H should be a better choice than Li as the auxiliary atoms around CBe₅ ppC core.^17b Herein, we wonder whether H atoms can be attached onto the Be-doped ppC structures to design the new ppC molecules possessing the molecular charges with ±1|e|, which facilitates the experimental generation and accurate calculation. The answer is positive and presented in this computational study, which designed nine new ppC molecules (see Fig. 1), in which four of them are kinetically stable global minima, thereby providing promising targets for experimental realization.Open in a separate windowFig. 1Optimized structures 1a–9a at the B3LYP/aug-cc-pVTZ level. Bond distances and NBO charges are given in black and italic blue fonts, respectively.