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We report a study of solvent effects on the rate, selectivity, and mechanism of (hetero)aryl (pseudo)halide oxidative addition to Pd(PCy3)2 as an exemplar of L2Pd(0) species. First, 2‐chloro‐3‐aminopyridine is observed to undergo faster oxidative addition in toluene compared to more polar solvents, which is not consistent with the trend we observe with many other 2‐halopyridines. We attribute this to solvent basicity hydrogen bonding between solvent and substrate. Greater hydrogen bond donation from the substrate leads to a more electron‐rich aromatic system, and therefore slower oxidative addition. We demonstrate how this affects rate and site‐selectivity for hydrogen bond donating substrates. Second, electron‐deficient multihalogenated pyridines exhibit improved site‐selectivity in polar solvents, which we attribute to different C−X sites undergoing oxidative addition by two different mechanisms. The C−X site that favours the more polar nucleophilic displacement transition state is preferred over the site that favours a less‐polar 3‐centered transition state. Finally, (hetero)aryl triflates consistently undergo faster oxidative addition in more polar solvents, which we attribute to highly polar nucleophilic displacement transition states. This leads to improved site‐selectivity for C−OTf oxidative addition, even in the presence of highly reactive 2‐pyridyl halides. [ABSTRACT FROM AUTHOR]

The factor affecting the microscopic basicity of oxygen in the SiOSi bond are investigated on the basis of the O1s binding energy measured by X‐ray photoelectron spectroscopy (XPS). The samples used are SiO2, Na2OSiO2, CaOSiO2, CaOMgOSiO2, and CaOAl2O3SiO2. For analysis on clean surfaces, samples are finally prepared by fracturing in a vacuum in an XPS system. From the O1s spectra, derived are the centers of gravity of the O1s spectra and the binding energies of O1s in the SiOSi, SiOAl, AlOAl, SiONa, SiOCa, and SiOMg bonds. A good linear relationship is found between the center of gravity of the O1s spectra and the optical basicity, suggesting that the center of gravity of the O1s spectra is a reasonable basicity index of silicate glasses used in this work. It is also found that there is a linear relationship between the binding energy of O1s in the SiOSi bond and the optical basicity, irrespective of the glass systems. This indicates that the experimental microscopic basicity of oxygen in SiOSi bond is affected not only by the first neighboring ions of oxygen but also by the composition of the sample. [ABSTRACT FROM AUTHOR]

The regularities of extraction of adsorbate from spent bleaching earth (SBE) of sunflower oil by the esteraldehyde fraction (EAF) have been established. The content of the substances adsorbed by SBE was 34.1%, including 19.2% free fatty acids (FFA) and 11.1% moisture. The influence of temperature (50 and 700 C), extraction duration (60 and 120 min), and the mass ratio of EAF to SBE ((2–4):1) on the extraction parameters has been determined. It was found that increasing these process parameters enhances the extraction degree of the adsorbate and FFA from the bleaching earth, reaching 41.9% and 34.4%, respectively, at a temperature of 700 C, extraction duration of 120 min, and a mass excess of EAF to SBC at a ratio of 4:1. Optimal conditions for the removal of FFA from SBE were identified. It was established that strong acidic sites are present on the surface of the bleaching earth, with the acidity of fresh, spent, and EAF-treated bleaching earth being 0.79, 0.77, and 0.74 mmol H+ per gram, respectively. The basicity of fresh bleaching earth was 0.073 mmol OH– per gram, indicating the ability of bleaching earth to catalyze the esterification of FFA with ethanol. The suitability of the obtained extract for the production of FFA ethyl esters was demonstrated. [ABSTRACT FROM AUTHOR]

Herein we demonstrate the formation of new stimuli‐responsive aqueous biphasic systems (ABS), able to respond simultaneously to temperature and pH, or just to one stimulus, therefore allowing the design of more sustainable separation processes. This dual behavior is achieved with ABS formed by mono‐ or dicationic protic ionic liquids as phase‐forming components, being defined by the ionic liquid cation chemical structure or its basicity. While ABS comprising monocationic ionic liquids only respond to the effect of temperature, systems comprising dicationic ionic liquids are simultaneously affected by both temperature and pH variations. Dicationic ionic liquids are here identified as the key to unlock a double response to stimuli, which is due to the presence of two pKa values afforded by the cation. The reported findings contribute to increase the customizability of double stimuli‐responsive ABS based on ionic liquids, whose development was up to date limited to ionic liquids bearing pH‐responsive anions, opening the door towards the development of more sustainable separation processes. [ABSTRACT FROM AUTHOR]

Solid bases are valuable catalysts for industrial syntheses. However, controlling the basicity of these catalysts remains a challenge. Ga4B2O9, due to μ3-O within its structure, could behave as a special solid base catalyst exhibiting intrinsic Lewis basicity. In this work, a sol–gel method was proposed to obtain continuously adjustable acidity and basicity of the metal borate catalyst (AlxGa1−x)4B2O9. According to the results of NH3-TPD, CO2-TPD, and the systematic experimental design, Lewis basic sites originating from GaO5 groups in (AlxGa1−x)4B2O9 boost the Strecker reaction rather than the Lewis acid sites related to unsaturated Al. This work illustrates the possible application of bulk-type solid solutions with simultaneous Lewis acid and base sites for the first time. A reaction mechanism has also been proposed based on the catalytic reaction results. [ABSTRACT FROM AUTHOR]

Among the alkali metals, potassium is known to significantly shift selectivity toward value-added, heavier alkanes and olefins in iron-based Fischer–Tropsch synthesis catalysts. The aim of the present contribution is to shed light on the mechanism of action of alkaline promoters through a systematic study of the structure–reactivity relationships of a series of Fe oxide FTS catalysts promoted with Group I (Li, Na, K, Cs) alkali elements. Reactivity data are compared to structural data based on in situ, synchrotron-based XRD and XPS, as well as temperature-programmed studies (TPR-H2, TPC-CO, TPD-CO2, and TPD-H). It has been observed that the alkali elements induced higher carburization rates, higher basicities, and lower adsorbed hydrogen coverages. Catalyst stability followed the trend Na-Fe > unpromoted > Li-Fe > K-Fe > Cs-Fe, being consistent with the ability of the alkali (Na) to prevent active site loss by catalyst reoxidation. Potassium was the most active in promoting high α hydrocarbon formation. It is active enough to promote CO dissociative adsorption (and the formation of FeCx active phases) and decrease the surface coverage of H-adsorbed species, but it is not so active as to cause premature catalyst deactivation by the formation of a carbon layer resulting in the blocking active sites. [ABSTRACT FROM AUTHOR]

Reducing carbon dioxide emissions is one of the largest energy and environmental challenges currently faced globally. To achieve carbon neutrality, the development of new technologies and simultaneous improvement of conventional technologies are required. Catalysis, which determines the success or failure and efficiency of the process, is at the center of addressing these problems. Innovative advancements in catalysis have been accomplished through the extensive research on catalytic materials. Oxygen storage materials with oxygen storage capacity (OSC) have been widely applied in supports and active cocatalysts for energy and environmental catalytic applications. This review provides knowledge on the extended applications (reforming, water-gas shift reaction, and partial oxidation of methane (POM) for high-value-added chemicals, including hydrogen production, deoxygenation of fatty acids for second-generation biofuel production, selective catalytic reduction of NOx with NH3, hydrocarbon (HCs) oxidation for emission control, CO oxidation for vehicle exhaust control and purification of gaseous product fuel, and soot oxidation for the removal of motor-type pollutants) of these materials, which are mainly used as three-way catalysts (TWC) in automotive catalysis, to the carbon-neutral field. In particular, this study focuses on the physico-chemical properties that are closely synergistic with OSC, such as reducibility, dispersion, surface acid/base properties, and physical properties, such as surface structure or morphology. [ABSTRACT FROM AUTHOR]

Context: 1,1- and 1,2-ethenedithiol are elusive systems that could potentially exist in interstellar space, similar to analogous diols. In this paper, we investigate the structure, stability, and bonding characteristics of these compounds as well as the ions produced by protonation, deprotonation, or simple ionization processes. 1,2-ethenedithiol has two isomers, Z and E, with the most stable conformer being syn-anti for the Z isomer and anti-anti for the E isomer. However, the energy gaps between the different conformers are never larger than 6 kJ·mol−1. For 1,1-ethenedithiol, the global minimum is the syn-anti conformer. The vertical and adiabatic ionization processes as well as the intrinsic basicities and acidities of these families of compounds were analyzed and compared with those of the corresponding diols previously reported in the literature. This comparison revealed not only the numerical differences in these thermodynamic properties but also distinct trends between the two families of compounds. Methods: State-of-the-art G4 ab initio calculations were employed to calculate the structures and total energies of the systems under investigation. The QTAIM, ELF, and NBO approaches were used to analyze the electron density of all the neutral and charged systems included in our study. Van der Waals contributions, when relevant, were analyzed by locating regions of low reduced density gradient(s) using the NCIPLOT approach. [ABSTRACT FROM AUTHOR]

A sequence of MgO-ZrO2 mixed oxides with varying their ratios were synthesized by adopting co-precipitation method. These catalysts characteristics were deduced from different spectroscopic methods and used for vapor phase cross-ketonization of pivalic acid with acetic acid to produce pinacolone at atmospheric pressure. The characterization results indicated that at a high ZrO2 molar ratio, MgxZr1-xO2-x mixed oxide phase is formed, and it accounted for the presence of strong basic sites. MgO-ZrO2 mixed oxides ketonization activity is superior to individual oxides and the overall activity mainly depended on their molar ratio, calcination temperature, and presence of mixed oxide phase. The basicity of the MgO-ZrO2 mixed oxide catalyst is responsible for the high conversion of pivalic acid. The ketonization reaction is carried under different reaction parameters and optimized conditions were established. The catalysts are showed stability during the time on stream analysis. [ABSTRACT FROM AUTHOR]

Approximately 10–15% of the world's steel production is derived from small industries. While ladle furnaces contribute to maintaining a generally good quality of refined steel, new challenges arise, especially when striving for very low sulfur percentages in steel. To address this, the study explores the impact of process parameters such as aluminum, silicon, and basicity in reducing sulfur content. Three interconnected equilibrium/adiabatic stoichiometric-reactor-based approaches describe the overall ladle steel-making process. The macro-programming facility of FactSage™ software was used to determine the refining behaviors of the ladle steel-making processes. The model's predicted endpoint, manganese, sulfur, oxygen, and aluminum content, agreed with plant data. This efficient model is a valuable guiding tool for ladle steelmaking industries with a 10–15 ton capacity. [ABSTRACT FROM AUTHOR]

Glycerol transesterification with diethyl carbonate (DEC) using catalysts with different porosities as support for CaO was performed, seeking the evaluation of how textural properties influence glycerol conversion and product selectivity. A total of 20% CaO was supported on ZSM-5, K-10, MCM-41, SiO2, and γ-Al2O3. Catalysts showed a well-dispersed active phase of CaO in all the supports and no changes in the support crystalline structure were noticed. Reactions were performed in dimethyl sulfoxide (DMSO), 10 wt.% of catalyst in relation to glycerol, at 130 °C, and 1:3 glycerol/DEC molar ratio. According to our results, the higher the pore volume and pore size, the higher the glycerol conversion. On the other hand, concerning selectivity, higher glycerol carbonate selectivities were reached when strong basic sites were present. A total of 86% glycerol conversion and 91% glycerol carbonate selectivity were found using 60% CaO supported on γ-Al2O3 after 5 h of reaction. [ABSTRACT FROM AUTHOR]

Welding current is an essential parameter for submerged arc welding process. In submerged arc welding, the enormous heat generated by the current promotes the decomposition of the oxides in the flux, releasing oxygen and increasing the oxygen level in the metal, which further affects the microstructure and mechanical properties of the weld joint. Although previous studies have developed various models to evaluate oxygen content, the thermodynamic mechanism by which current influences oxygen levels in metal remains inadequately understood. This study integrates CALPHAD technology with welding thermodynamics to predict and simulate the impact of the welding current on oxygen content in metals. By combining experimental data with thermodynamic modeling, the research investigates how different current settings affect oxygen content in the metal across various welding zones, specifically when using CaO-Al2O3 fluxes with low and high basicity indices for the welding of typical carbon steel. This study selected two current values, 300 A and 600 A, for modeling analyses of the welding process, along with two typical fluxes with basicity indices of 1.6 and 0.4. The results indicate that the proposed method outperforms the BI model and can predict the metallurgical effects of current on oxygen content in the droplet and molten pool zones. The thermodynamic mechanisms that govern the metal oxygen level are also evaluated. These findings aim to enhance the understanding of the thermodynamic mechanism that governs oxygen behavior under different current conditions, thereby contributing to the optimization of submerged arc welding process. [ABSTRACT FROM AUTHOR]

In this study, we investigate the protonation effects on the structure, relative stability and basicity of complexes formed by the interaction of monomers and dimers of BeX2 and MgX2 (X = H, F) with NH3, CH2NH, HCN, and NC5H5 bases. Calculations were performed using the M06‐2X/aug‐cc‐pVTZ formalism, along with QTAIM, ELF and NCI methods for electron density analysis and MBIE and LMO‐EDA energy decomposition analyses for interaction enthalpies. The protonation of the MH2– and M2H4–Base complexes occurs at the negatively charged hydrogen atoms of the MH2 and M2H4 moieties through typical hydride abstraction reactions, while protonation at the N atom of the base is systematically less exothermic. The preference for the hydride transfer mechanism is directly associated with the significant exothermicity of H2 formation through the interaction between H− and H+, and the high hydride donor ability of these complexes. The basicity of both, MH2 and M2H4 compounds increases enormously upon association with the corresponding bases, with the increase exceeding 40 orders of magnitude in terms of ionization constants. Due to the smaller exothermicity of HF formation, the basicity of fluorides is lower than that of hydrides. In Be complexes, the protonation at the N atom of the base dominates over the fluoride abstraction mechanism. However, for the Mg complexes the fluoride abstraction mechanism is energetically the most favorable process, reflecting the greater facility of Mg complexes to lose F−. [ABSTRACT FROM AUTHOR]

Phosphanes play an important role in various applications, serving as a class of organic bases with basicities spanning more than 30 orders of magnitude. Accessing comprehensive basicity data for phosphanes has been challenging due to scattered information across multiple sources and notable gaps in the existing data. In this report, we present basicities (pKaH values) of a diverse set of phosphanes, both newly measured or calculated and collected from the literature. We demonstrate that pKaH values can serve as an alternative to Tolman electronic parameters (TEP values) in evaluating the electronic properties of phosphanes. Additionally, we suggest parameters for assessing the steric properties of phosphanes without the need for preparation or calculation of metal-ligand complexes. [ABSTRACT FROM AUTHOR]

Dry reforming of methane (DRM), the catalytic conversion of CH4 and CO2 into syngas (H2+CO), is an important process closely correlated to the environment and chemical industry. NiAl‐based catalysts have been reported to exhibit excellent activity, low cost, and environmental friendliness. At the same time, the rapid deactivation caused by carbon deposition, Ni sintering, and phase transformation exerts great challenges for its large‐scale applications. This review summarizes the recent advances in NiAl‐based catalysts for DRM, particularly focusing on the strategies to construct efficient and stable NiAl‐based catalysts. Firstly, the thermodynamics and elementary steps of DRM, including the activation of reactants and coke formation and elimination, are summarized. The roles of Al2O3 and its mixed oxides as the support, and the influences of the promoters employed in NiAl‐based catalysts over the DRM performance, are then illustrated. Finally, the design of anti‐coking and anti‐sintering NiAl‐based catalysts for DRM is suggested as feasible and promising by tailoring the structure and states of Ni and the modification of Al‐based supports including small Ni size, high Ni dispersion, proper basicity, strong metal‐support interaction (SMSI), active oxygen species as well as high phase stability. [ABSTRACT FROM AUTHOR]

The current study included the Al-Buwair drinking water station located northwest of Mosul City in Nineveh Governorate/Iraq with the aim of evaluating the station's performance efficiency compared to the Iraqi standard specifications. Samples were collected starting from October 2023 until July 2024. Some physicochemical and biological properties were measured, including acidity (pH), electrical conductivity (EC), turbidity concentration (Turb.), total hardness (T.H), total basicity (Alk), total dissolved solids (TDS), sulfate ions (SO4-2), chloride (Cl-), and nitrate (NO3) in addition to the total bacterial count (T.P.C). The results of the current study showed that all the studied properties conformed to the Iraqi standard specifications. [ABSTRACT FROM AUTHOR]

The proton affinity (PA) and gas phase basicity values of previously reported cyclic allene series are investigated using high-level quantum chemical calculations. Some of the studied structures possessed more than one protonation site. All protonation types were explored for each structure and the compounds with PA value more than ≈1030 kJ mol−1 were considered superbasic structures. Cyclic allene's basicity strength was affected by ring size, adjacent heteroatom's presence and resonance existence in protonated form. [ABSTRACT FROM AUTHOR]

In this work, the surface tension of CaF2–CaO–SiO2 melt with high CaF2 contents was measured by pulling cylinder method at 1773 K. The effects of CaF2 content, basicity, and the addition of MgO and Al2O3 on the surface tension were also investigated by considering the change in the melt structure. It was observed that as the CaF2 content increased from 30 to 80 mass%, there was no further depolymerizing effect on the silicate structure of the melt, maintaining a constant basicity of 1. However, the surface tension of the melts decreased from 397 to 325 mN/m due to the surface-active effect of CaF2. With the increase of basicity from 0.5 to 3, the surface tension of the melt initially increased from 342 mN/m to a maximum value of 390 mN/m, then decreased to 368 mN/m. The maximum value occurred at a basicity of 2. Furthermore, at constant basicity, the addition of MgO from 0 to 10 mass% led to a decrease in the surface tension of the melt decreased from 358 to 326 mN/m. Similarly, with the basicity ranging from 1 to 3, the addition of 10 mass% Al2O3 resulted in a decrease in the surface tension of the melt. [ABSTRACT FROM AUTHOR]

Theoretical design of molecular superbases has been attracting researchers for more than twenty years. General approaches were developed to make the bases potentially stronger, but less attention was paid to the stability of the predicted structures. Hence, only a small fraction of the theoretical research has led to positive experimental results. Possible stability issues of extremely strong bases are extensively studied in this work using quantum chemical calculations on a high level of theory. Several step-by-step design examples are discussed in detail, and general recommendations are given to avoid the most common stability problems. New potentially stable structures are theoretically studied to demonstrate the future prospects of molecular superbases design. [ABSTRACT FROM AUTHOR]

The effects of CaO/SiO 2 ratio (basicity) and CaCl 2 addition amount on the properties of CaO–MgO–Al 2 O 3 –SiO 2 –CaCl 2 glass-ceramics (GC) were investigated. When sintered at 825 °C, the increase in basicity from 0.35 to 0.75 reduced the porosity of GCs from 1.1 to 0.8 vol%, but the increase of CaCl 2 addition amount from 5 to 10 wt% increased the porosity from 0.8 to 7.0 vol%. The main crystalline phase of GC changed from augite (Ca(Mg 0 · 7 Al 0.3) (Si 1 · 7 Al 0.3)O 6) to Ca 10 Al 12 Cl 2 Si 5 O 37 by increasing the CaCl 2 addition amount to 7.5 wt%. The increase in CaCl 2 addition had adverse effects on the bending strength and Vickers hardness, while the rise in basicity deteriorated the bending strength but had little impact on the Vickers hardness. This study may have a guiding significance for preparing slag-based GCs and treating CaCl 2 -containing wastes. [ABSTRACT FROM AUTHOR]

The distribution of iron-bearing granular materials in the throat of a blast furnace (BF) plays a crucial role in influencing their performance at high temperatures. Therefore, it is essential to establish a quantitative relationship between the charging operation of the iron-bearing materials at ambient temperatures and their subsequent softening and melting behaviors at elevated temperatures. In this study, the discrete element method (DEM) is employed to quantify the instantaneous mass segregation of quaternary iron-bearing materials throughout the continuous charging process, starting from the feeding conveyor belt and continuing up to the throat. Subsequently, employing quaternary basicity (R4) as a pivotal bridge, softening and melting experiments (the temperature above 900 °C and in an atmosphere with a mole fraction of 30 pct CO to 70 pct N2) are conducted to assess the influence of physical segregation on chemical performances under simulated BF conditions. The results reveal that the sequence of loading quaternary iron-bearing materials onto the feeding belt causes fluctuations in R4, ranging from 1.08 to 1.75. Moreover, these fluctuations are propagated throughout the charging process, resulting in notable fluctuations in the mass fractions of iron-bearing materials and the R4 at the hopper outlet and the end of the chute. Therefore, the primary factor influencing the flowing characteristics of the granular materials is their distribution within the hopper. Then, the segregation in the throat is further characterized by the presence of two distinct R4 ranges (1.2 to 1.29, and 1.3 to 1.39) observed across a total of 48 equal-area blocks, and the significant difference between these two categories is determined by sinters. Besides, the influence of the R4 on softening and melting temperatures is quantitatively evaluated, resulting in a 'w'-shaped temperature distribution from the center to the edge of the BF. Our findings provide evidence of the inadequacy of evaluating the softening and melting behaviors of iron-bearing materials solely based on their initial proportions in the structure of iron-bearing materials. Instead, a quantitative examination of the granular segregation in the throat, arising from the BF charging operation, is deemed essential to provide substantial support for well-designed elevated-temperature experiments. This approach enables a more comprehensive understanding of the intricate journey of iron-bearing materials in the BF. [ABSTRACT FROM AUTHOR]

In this paper, we study an analogue of Tricomi problem for a parabolichyperbolic equation of the first type. To solve the problem for the heat equation, we use properties of the spectral problem with a spectral parameter in the boundary conditions. We show the basicity of the spectral problem with the spectral parameter in the boundary conditions. The conditions for the correctness of the formulated Tricomi problem are found. [ABSTRACT FROM AUTHOR]

4‐ and 5‐coordinate zinc thiolate complexes supported either by bis(carboxamide)pyridine frameworks or by substituted tris(pyrazolyl)borate ligands react with elemental sulfur (S8) following two distinct pathways. Some zinc thiolate moieties insert sulfur atoms to form zinc polysulfanide complexes, while others reduce sulfur and oxidize the thiolate. Here, we compare the effects of ligand electronics, strain, and sterics for selecting the respective reaction pathway. These results show that chelating and electron‐deficient thiolate ligands better stabilize persistent zinc‐bound polysulfanide species. [ABSTRACT FROM AUTHOR]

Profiting from the dual high basicity and nucleophilicity of organosodium complexes, here we report the stepwise lateral metalation of a wide range of alkyl arenes (MeAr), mediated by hydrocarbon‐soluble NaCH2SiMe3 ⋅ PMDETA (PMDETA=N,N,N',N",N"‐pentamethyldiethylenetriamine), followed by nucleophilic addition to diarylethenes of the newly generated NaCH2Ar ⋅ PMDETA complexes. This method grants access to a range of functionalised hydrocarbons in excellent yields and can be upgraded to catalytic regimes when using trans‐stilbene, a 10 mol% of the alkyl sodium base and toluene as a solvent. Extending this approach to aromatic ketones leads to the formation of stilbenes under mild reaction conditions, resulting from the deprotonative coupling of toluenes with ketones. Combining spectroscopic studies with the trapping and characterisation of key reaction intermediates, mechanistic insights have been gained, advancing the understanding of coordination effects in organosodium chemistry, and shedding light on their special reactivity profiles. [ABSTRACT FROM AUTHOR]

Cucurbiturils are popular macrocyclic receptors that bind complementary guest molecules with high affinity in aqueous environments. They are recognized for their ability to selectively bind positively charged guest molecules, including ionizable ammonium cations which frequently display much higher affinity than their neutral counterparts. This selectivity for the protonated species is translated into an increase in the basicity of encapsulated guests (i. e. into complexation‐induced positive pKa shifts). However, despite being very rare, negative pKa shifts can be observed for specific guests. Following a previous work from our group reporting slightly negative pKa shifts for flavylium and chalcone dyes featuring N‐diethylamino substituents (ΔpKa=− 0.2), herein we report a systematic study on the complexation of N‐dialkylaminochalcones with CB7. The results show that the pKa shifts of these host‐guest complexes can be rationally tuned by the nature of the N‐dialkylamino groups and as well by target substitutions on the skeleton of the dye, allowing the design of a CB7 1 : 1 host‐guest complex with a ΔpKa=− 0.6. [ABSTRACT FROM AUTHOR]

The influence of peripheral substitution and the nature of the macroheterocyclic heteroatoms on the basicity of hydrophilic 5,10,15,20-tetraarylporphyrins in the lowest excited singlet S1 state was studied using absorption and fluorescence spectroscopies. The basicity of the porphyrins themselves in the lowest excited singlet S1 state was found to decrease as compared to the ground S0 state. The difference in basicity constants pKa depended on the nature of electronic communication between the macrocycle and peripheral substituents. In the case of an inductive effect of the substituents, the difference in the basicity constants pKa was small, while mesomeric effects led to significant differences in the pKa values. The cooperative nature of protonation, leading to almost simultaneous addition of two protons, was shown to be preserved in both cases. Replacement of a pyrrole with a thiophene in the macroheterocycle led to a decrease in cooperativity in both the ground S0 and the lowest excited singlet S1 states. The basicity constants characterizing the addition of the second and third protons by thia-substituted porphyrin differed significantly in the S1 state (pKa2 – pKa1 = 2), while they were close in the ground state. The activation entropy change ΔΔS‡ upon protonation of the porphyrins in the lowest excited S1 state was compared to that in the ground S0 state. [ABSTRACT FROM AUTHOR]

To enhance the proportion of domestically manufactured Chinese pellets in the furnace, it is crucial to investigate the impact of calcium flux on the metallurgical characteristics of pellets and analyze the phase evolution behavior during the reduction process of medium‐silica fluxed pellets. This study examines the metallurgical properties of medium‐silica acid pellets and low‐basicity medium‐silica fluxed pellets produced in China. The results indicate that incorporating a small amount of calcium flux significantly enhances reducibility index (RI), reduces reduction swelling index, and lowers reductive degradation index (RDI+3.15 mm) for fluxed pellets. At a basicity level of 0.6, RI for medium‐silica fluxed pellets reaches 66.86%, while RDI−0.5 mm increases to 1.62% with increasing basicity levels. As pellet basicity increases, charge pressure drop (APmax) decreases, CaO content in silicate liquid phase within slag phase increases, and softening–melting zone widens, consequently leading to reduced solid‐phase particle content within pellets and increased fluidity within slag phase. [ABSTRACT FROM AUTHOR]

Numerous challenges persist in the smelting of vanadium–titanium magnetite using the blast furnace process. These challenges can be overcome by adopting the HIsmelt process, without the need for additional ore or enhanced slag operations. In this study, the effects of basicity and the MgO/Al2O3 ratio on slag viscosity and crystallization behavior are investigated through thermodynamic calculations and experiments. In the results, a decrease in slag viscosity with an increase in basicity and MgO/Al2O3 ratio is demonstrated. Notably, MgO/Al2O3 ratios have a minor impact on the viscosity and break temperature of the slag. With a TiO2 content of 40 wt% in the slag, perovskite phases are identified as the main equilibrium solid precipitates during the crystallization process under various basicity and MgO/Al2O3 ratios. As the slag temperature decreases further, the liquid phase content in the slag progressively decreases, reaching complete crystallization at 1159.0 °C. For industrial production, it is advisable to maintain the binary basicity of the slag within the range of 1.0–1.1, with the MgO/Al2O3 ratio around 0.6. Herein, the research findings contribute to a deeper understanding of the viscosity and crystallization behavior of HIsmelt titanium‐containing slag. [ABSTRACT FROM AUTHOR]

Thermodynamic calculations and thermal analysis tests were performed to investigate the thermodynamic and kinetic behaviors of the carbothermal reduction of vanadium-titanium magnetite w(C)/w(O) and basicity on the carbothermal reduction process of vanadium-titanium magnetite based on the HIsmelt process. Thermodynamic analysis showed that the addition of basicity promoted the reduction of vanadium-titanium magnetite, and the reaction onset temperature gradually increased with the decrease of the valence states of the elements V, Ti and Fe in the product. Increasing the amount of carbon assigned to the system gradually increased the mass fractions of metal Fe and Fe3C and raised the mass fractions of Ti, V and their low valence compounds at equilibrium. Increasing the basicity had less effect on the Fe, V and Ti fractions of the equilibrium system. The results of kinetic tests showed that the maximum reduction degree and maximum reaction rate of the reduction reaction by increasing w(C)/w(O) and basicity increased, the apparent activation energy and the finger front factor decreased, and the reaction mechanism function of the non-isothermal kinetic reduction process was f(α) = (3/2)(1−α)4/3[(1−α)−1/3−1] −1 belonging to the three-dimensional Z-L-T diffusion model. [ABSTRACT FROM AUTHOR]

Alkali tellurite glasses based on the compositions xLi2O-(30−x)TeO2-10As2O3-58B2O3-2V2O5 and xK2O-(30−x)TeO2-10As2O3-58B2O3-2V2O5 (where x = 5, 10, 15, 20, and 25 mol%) have been prepared using the melt quenching method, and their EPR, optical, and structural properties were investigated as a function of alkali ion concentration. The X-ray diffraction analyses showed that Li2O and K2O- doped tellurite boro-arsenate glasses had a completely amorphous structure. The electron paramagnetic resonance spectra of VO2+ ions in these glasses have been recorded in the X band (9.14 GHz) at room temperature. The spin Hamiltonian parameters, dipolar hyperfine coupling parameter, and Fermi contact interaction parameter have been calculated. It is observed that the resultant resonance spectra contain hyperfine structures (hfs) due to V4+ ions which exist as VO2+ ions, in octahedral coordination with a tetragonal compression in the present glasses. The optical absorption spectra reveal the characteristic spectrum in the visible region for the V2O5 doped prepared samples show three visible absorption peaks at ~ 462nm (2B2g → 2A1g), ~ 581 nm (2B2g → 2B1g), and ~ 798 nm (2B2g → 2Eg) in order of increasing wavelength, respectively. The optical band gap energies (Eopt) and Urbach energy (ΔE) have been determined from their ultraviolet edges. The theoretical values of optical basicity (ΛTh) of these glasses have also been evaluated. The density N (V4+ ion concentrations) for spins and paramagnetic susceptibility participating in resonance can be estimated. Structural studies were made by recording FTIR absorption spectra. [ABSTRACT FROM AUTHOR]

The high proportion of pelletizing blast furnace smelting technology is one of the important means to achieve the goal of "Double Carbon". Pellets prepared from Bayan Obo iron ore concentrate were selected as the research object. An X-ray diffractometer (XRD) and a Mössbauer spectrometer were used to analyze the influence mechanism of basicity on the reduction swelling performance of the pellets. The results showed that, when the basicity was 0.8, the reduction swelling index (RSI) of the pellets was the largest, and the lattice constant (a), grain size (Lc), average stacking layers of grain (Nave), residual stress (ε), and crystallinity of pellet reduction products reached extreme values. With the progress of the reduction reaction, ε, of the pellets gradually increased, and then decreased sharply in the third reduction stage. The crystallinity gradually decreased with the reduction reaction, indicating the amounts of K, Na, and Ca entering the iron oxide lattice. A smaller binding energy, larger space of motion, larger distortions, and residual stress are the reasons for the high RSI of the pellets. The Fe(II) of the pellets in the octahedral void was seriously absent, and the absence of Fe(II) gradually increased with the increase of basicity. Fe in pellets with a basicity of 0.8 has a lower coordination number and a smaller atomic arrangement. [ABSTRACT FROM AUTHOR]

Spinel is known to cause clogging of the submerged entry nozzle in continuous casting. The effect of basicity on the precipitation behavior of MgO·Al2O3 in Al-killed steel with w[Al] = 0.065% at 1550°C was investigated. The inclusions in steel are mainly MgO·Al2O3 spinel after slag-steel reaction, which is consistent with the thermodynamic results. The polygonal spinel transforms to nearly spherical or rod-like with the sizes smaller than 5 μm with the increase of refining-slag basicity. The number of inclusions shows little variation with basicity. In industrial production, it is often observed that spinel inclusions in molten steel are transformed into CaO-Al2O3-MgO inclusions. However, this phenomenon was not observed in this study. Two sets of experiments were conducted; therefore, the reasons behind the lack of transformation from spinel to CaO-Al2O3-MgO inclusions were elucidated. We determined that Mg in MgO·Al2O3 originated from the MgO crucible, and the [Ca] and [Mg] supplied through the steel slag reaction were insufficient to facilitate the modification of Al2O3. [ABSTRACT FROM AUTHOR]

The impact of heterogeneous catalytic systems, which are based on rare earth metals, on the properties of biodiesel produced via the transesterification process in a stationary reactor (autoclave) was thoroughly investigated. The physicochemical attributes, including the specific surface area, were analyzed employing the Brunauer–Emmett–Teller (BET) method. The basicity and acidity levels of the catalytic systems were evaluated through temperature-programmed desorption of ammonia and carbon dioxide (TPD-NH3, TPD-CO2), respectively. Furthermore, High-Performance Liquid Chromatography (HPLC) analysis facilitated the assessment of triglyceride conversion and the determination of methyl ester (FAME) selectivity within these processes. Our findings indicate that catalytic systems augmented with lanthanum showcased superior performance. A significant correlation was discerned between the conversion and selectivity to methyl esters and both the specific surface area and the acidity and basicity properties of the catalytic systems under study. These results underscore the crucial role that the physicochemical characteristics of catalytic systems play in optimizing the transesterification process, thereby enhancing the quality of the produced biodiesel. This study contributes valuable insights into the development of more efficient and effective biodiesel production methodologies, highlighting the potential of rare earth metal-based catalysts in renewable energy technologies. [ABSTRACT FROM AUTHOR]

Co3Mo3N has been reported to have activity for the synthesis of ammonia surpassing that of industrial Fe catalysts under certain conditions. However, so far the research has largely focused on unsupported Co3Mo3N. We report a comprehensive study on the catalytic activity of Co3Mo3N when supported on two distinct MgO substrates. Our findings reveal that the method of MgO preparation plays a crucial role in influencing surface basicity. Remarkably, Co3Mo3N supported on single‐crystalline MgO demonstrates significantly enhanced catalytic activity, achieving a 162.0 mmol g−1metal h−1 rate. This surpasses the performance on commercial MgO support (41.2 mmol g−1metal h−1) and unsupported Co3Mo3N (15.0 mmol g−1metal h−1). While kinetic analyses show no substantial differences between the two supported catalysts, spectroscopic studies employing CO2 and N2 temperature‐programmed desorption (TPD) reveal a richer array of basic sites and adsorption/desorption phenomena on the single‐crystalline MgO support. These catalysts exhibit exceptional stability. The drastically reduced Co/Mo loading amounts in comparison to the bulk form, make the commercialization of Co3Mo3N catalysts more practical. [ABSTRACT FROM AUTHOR]

To achieve low‐cost clean production in steelmaking plants, a low‐carbon double slag converter steelmaking process (LCDSP) with high dephosphorization efficiency, low lime consumption, and low CO2 emissions is focused on. The average lime consumption in LCDSP has decreased about 25.8%, which can reduce at least about 10.3 million m3 CO2 emissions per converter per year in the current steelmaking plant. The phosphorus enrichment properties of decarbonization slag with different basicities are comprehensively evaluated through LCDSP industrial experiments, mineralogy, and ion–molecule coexistence theory (IMCT). The increase of decarburization slag basicity (DSB) significantly improves the dephosphorization efficiency of molten steel. With increasing the DSB from 2.93 to 3.52, the typical morphology of the P‐rich phase extends from small pieces to long strips and then changes to block shapes with smooth edges. Finally, it forms a massive P‐rich phase with an area of more than 10 000 μm2 with a DSB of 3.80. The phosphorus enrichment properties of decarbonization slag with different DSBs evaluated using multiple perspectives show a consistent change trend. IMCT provides an accurate thermodynamic method for quantitatively predicting the phosphorus enrichment capacity in slag in two stages of LCDSP. [ABSTRACT FROM AUTHOR]

In order to apply and develop fluorine‐free slag in steelmaking, it is of great significance to study the effect of composition for fluorine‐free refining slag on the cleanliness of molten steel which affects its performance directly. The effect of composition of fluorine‐free refining slag with medium and high basicity on the contents of impurity elements for sulfur and oxygen, and characteristics of inclusions in SWRS82B hard wire steel, are investigated systematically. Sulfide capacity of refining slag is estimated based on the Royal Swedish Institute of Technology model. Dissolved oxygen content in molten steel equilibrated by refining slag is calculated based on Factsage software and classical thermodynamics. The calculated results are in good agreement with experimental results. The plasticity of inclusions at high temperature and low temperature is analyzed by phase diagram and Young's modulus calculation. The best cleanliness and inclusions of SWRS82B steel are obtained with slag composition of 53%CaO–19%SiO2–19%Al2O3–7%MgO, which has good melting characteristics. The impurity elements sulfur and oxygen in steel can be controlled for 26 and 19 ppm, respectively, and the average size of inclusions is 2.84 μm. [ABSTRACT FROM AUTHOR]

In this review, the principles of gas-phase proton basicity measurements and theoretical calculations are recalled as a reminder of how the basicity PA/GB scale, based on Brønsted–Lowry theory, was constructed in the gas-phase (PA—proton affinity and/or GB—gas-phase basicity in the enthalpy and Gibbs energy scale, respectively). The origins of exceptionally strong gas-phase basicity of some organic nitrogen bases containing N-sp3 (amines), N-sp2 (imines, amidines, guanidines, polyguanides, phosphazenes), and N-sp (nitriles) are rationalized. In particular, the role of push–pull nitrogen bases in the development of the gas-phase basicity in the superbasicity region is emphasized. Some reasons for the difficulties in measurements for poly-functional nitrogen bases are highlighted. Various structural phenomena being in relation with gas-phase acid–base equilibria that should be considered in quantum-chemical calculations of PA/GB parameters are discussed. The preparation methods for strong organic push–pull bases containing a N-sp2 site of protonation are briefly reviewed. Finally, recent trends in research on neutral organic superbases, leaning toward catalytic and other remarkable applications, are underlined. [ABSTRACT FROM AUTHOR]

Reduction of friction and wear by lubrication is necessary to improve the efficiency and prolong the lifespan of industrial machinery. However, several aspects regarding the lubrication effects in additive-combined oil are still unresolved. This study focuses on the effects of combining zinc dialkyldithiophosphate (ZnDTP), molybdenum dithiocarbamate (MoDTC), and Ca sulfonate on the frictional behavior of poly-α-olefin 4 (PAO4) lubricant oils. Ball-on-disk friction tests demonstrated that the exclusive addition of high-base Ca sulfonate solution reduced friction and wear of the lubricating oil. When combined with ZnDTP and MoDTC, the friction coefficients of PAO with high-base and low-base Ca sulfonate are affected by competitive reactions on the sliding surface. Quartz crystal microbalance with dissipation monitoring measurements suggests that high-base Ca sulfonate forms a stronger adsorption film than low-base Ca sulfonate. Atomic force microscope observations confirmed that the addition of low-base Ca sulfonate reduced friction and wear, whereas high-base Ca sulfonate induced competitive reactions with ZnDTP and MoDTC. This study provides valuable insights into the effects of the combination of additives on the lubricity of PAO and their impact on friction and wear characteristics, which are valuable for the design of suitable lubricants for industrial machinery. [ABSTRACT FROM AUTHOR]

Partial oxidation of methane (POM) is a promising route for hydrogen production, and achieving a high H2 yield with an H2/CO ratio >3 is highly appealing. Optimization of Ni/Co ratios over Ce-Sc-ZrO2 (CSZ) is investigated for POM reaction and characterized by X-ray diffraction, Raman spectroscopy, temperature-programmed reduction/oxidation/desorption, and transmission electron microscopy. The active site derived from the reduction of “strongly interacted NiO” is responsible for the dissociation of C–H (of CH4), resulting high activity towards POM. 5Ni/CSZ has the highest amount of such active sites and attains the highest activity. 5Co/CSZ catalyst has cobalt-based active sites, and there is an inert carbon deposit during the reaction, causing the least activity. 3.75 wt% Ni and 1.25 wt% Co combination over CSZ support surges the highest density of basicity, oxide vacancy, and adequate amount of active sites derived from “strongly interacted NiO”. The active sites with enhanced metal-support interaction are further grown under exposure to oxidizing gas (O2) and reducing gas (H2) during the POM reaction. The highest density of basicity and oxide vacancy involves more CO2 and H2O in the sequential oxidation of CH4 under indirect pathways. The exclusive involvement of indirect pathways of POM and inhibition of hydrogen consuming reaction (like reverse water gas shift reaction) over 3.75Ni1.25Co/CSZ results into 48 % H2 yield and 3.26 H2/CO ratio up to 24 h time on stream at 600 °C. The H2 yield doubles to ∼97 %, and the H2/CO ratio comes close to 2 over 3.75Ni1.25Co/CSZ catalyst at 900 °C.

The α-Asarone-loaded on NH2-MIL-125 (AS@AMIL) was demonstrated to be exceptional potential as a chemo dynamic therapeutic agent (CDT) for lung cancer cells (A549), showing superior efficiency as compared to α-Asarone as well as pristine NH2-MIL-125. The loading of α-Asarone was achieved through cation-π interactions between –NH3+ groups of NH2-MIL-125 and the aromatic ring of α-Asarone. This interaction enriches the framework of AS@AMIL with electrons enhancing the basicity of the framework (O-atoms), which substantially accelerates the decomposition of endogenous H2O2 into reactive oxygen species (ROS) to exhibit enhanced CDT activity. The AS@AMIL exhibited ∼a 1.36-fold increase in ROS production (CDT activity) compared to pristine NH2-MIL-125. The study suggests that the loading of aromatic compounds in amine-functionalized MOFs through cation-π interactions (with –NH3+ groups) can enhance the basicity of MOFs for improved chemodynamic therapeutic activity, and such materials can also be promising as catalysts and CO2 adsorbents.

Abstract The study investigates the molecular structure of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) and its derivatives in the gas phase using B3LYP and M06-2X functional methods. Intermolecular interactions are analyzed using natural bond orbital (NBO) and atoms in molecules (AIM) techniques. NO2-substituted TEMPO displays high reactivity, less stability, and softer properties. The study reveals that the stability of TEMPO derivatives is mainly influenced by LP(e) → σ ∗ electronic delocalization effects, with the highest stabilization observed on the oxygen atom of the nitroxide moiety. This work also considers electron density, atomic charges, and energetic and thermodynamic properties of the studied NO radicals, and their relative stability. The proton affinity and gas-phase basicity of the studied compounds were computed at T = 298 K for O-protonation and N-protonation, respectively. The studied DFT method calculations show that O-protonation is more stable than N-protonation, with an energy difference of 16.64–20.77 kcal/mol (22.80–25.68 kcal/mol) at the B3LYP (M06-2X) method. The AIM analysis reveals that the N–O…H interaction in H2O complexes has the most favorable hydrogen bond energy computed at bond critical points (3, − 1), and the planar configurations of TEMPO derivatives exhibit the highest EHB values. This indicates stronger hydrogen bonding interactions between the N–O group and water molecules.

Brønsted basicity is a fundamental chemical property featured by several kinds of inorganic and organic compounds. In this Review, we treat a particularly high basicity resulting from the mechanical entanglement involving two or more molecular subunits in catenanes and rotaxanes. Such entanglement allows a number of basic sites to be in close proximity with each other, highly increasing the proton affinity in comparison with the corresponding, non-entangled counterparts up to obtain superbases, properly defined as mechanically interlocked superbases. In the following pages, the development of this kind of superbases will be described with a historical perusal, starting from the initial, serendipitous findings up to the most recent reports where the strong basic property of entangled molecular units is the object of a rational design. Brønsted basicity can be greatly enhanced by the mechanical entanglement of two or more interlocked molecular subunits within catenanes and rotaxanes. Here, the authors discuss the development of such mechanically interlocked superbases, and outline challenges and opportunities for future directions of research. [ABSTRACT FROM AUTHOR]

β‐fluorocarbanions have garnered considerable attention for their dual reactivity in nucleophilic processes and β‐fluorine elimination. In this study, a thorough computational analysis was conducted to explore the reactions of α‐(trifluoromethyl)styrenes with 2‐pyridones to delineate the factors determining protonation or defluorination pathways for the in situ generated β‐fluorocarbanions under varied basic conditions. Our findings illuminate the critical role of organobase basicity in steering the direction of the competitive protonation and β‐fluorine elimination reactions. We propose the use of pKaH values of organobases as a quantitative indicator for discerning the predominant reaction pathways. This provides an efficient approach to predict and control the reaction outcome, facilitating the deliberate design of reactions to leverage the unique reactivity of β‐fluorocarbanions in the realm of fluorine chemistry. [ABSTRACT FROM AUTHOR]

Converting carbon dioxide into value-added products is one of the most important inventions to solve global warming and energy demand. Herein, we prepared a series of Zr-doped CeO2 catalyst (Ce1Zrx, x = 0.01, 0.05 and 0.2) for the catalytic production of ethylene urea (EU) from ethylenediamine (EDA) and CO2. Several characterization techniques, such as XRD, FTIR, Raman, TEM, N2 adsorption, CO2-TPD and XPS, were used to investigate the relationship between catalytic activity and structural characteristics, especially the doping form and promotion mechanism of Zr in CeO2 lattice. The results present that the Ce1Zr0.01 catalyst revealed excellent catalytic activity with 91.5% EDA conversion and 100% EU selectivity and cyclic stability in comparison with undoped CeO2. The doped Zr was beneficial to the formation of enriched defects and led to more oxygen vacancies and weak basic sites, thus enhancing CO2 adsorption and activation. This work laid a foundation for the design of highly active catalysts for the synthesis of EU from CO2 and EDA. [ABSTRACT FROM AUTHOR]

With the aim of studying the occurrence of chromium reduction during argon-oxygen refining using boron oxide as a flux, thermodynamic modelling of the equilibrium interfacial distribution of chromium between slag of the oxide system CaO–SiO2–(3–6%)B2O3–12%Cr2O3–3%Al2O3–8%MgO in the range of basicity 1.0–2.5 and metal depending on temperature, boron oxide content, and basicity is performed. Modelling results are shown as diagrams of the dependence of the equilibrium interphase distribution of chromium on slag composition at 1600 and 1700 °C. It is found that an increase in slag basicity from 1.0 to 2.5 at 1600 and 1700 °C leads in the range of boron oxide content studied to a decrease in the interfacial distribution coefficient of chromium from 60.0 · 10−3 to 1.5 · 10−3 and as a result an increase in the degree of chromium reduction from 91 to 99.5%. An increase in metal temperature and boron oxide content have little effect on chromium reduction. The influence of basicity of the slags studied on the chromium reduction process may be qualitatively explained from the perspective of phases formed within slags and thermodynamics of chromium reduction reactions with aluminum and silicon. Experimental studies confirm results of thermodynamic modeling. [ABSTRACT FROM AUTHOR]

The use of experimental parameters to quantify solvent properties, for example in linear free energy relationships, is well established and several scales of solvent acidity, basicity and polarity/polarizability have been developed. The success of this approach raises questions of which molecular properties contribute to particular solvent parameters and whether these contributions are found in all parameters representing a particular solvent property. In the present study, Catalan's hydrogen bond basicity and acidity parameters, SB and SA, and Gutmann's acceptor number, AN, a measure of a solvent's Lewis acidity, are correlated with molecular properties derived from computational chemistry. The results are compared with the results of similar correlations with Kamlet and Taft's β and α Solvent Scales, Gutmann's donor number DN) and Abraham's B and A solute scales. The results show that measures of solvent basicity, SB, β and DN all correlate strongly with the partial charge on the most negative atom in the solvent molecule and the energy of the donor orbital and, in all cases, the parameter values for hydrogen-bonded solvents are anomalous. Abraham's B, a measure of solute hydrogen basicity, depends only on the partial charge on the most negative atom and there is no anomaly in the values for solutes that, in the pure state, form hydrogen-bonded liquids. Similarly, all measures of solvent acidity, SA, α and AN, and Abraham's A, a measure of solute hydrogen bond acidity, depend on the partial charge on the most positive hydrogen on the molecule. [ABSTRACT FROM AUTHOR]

Photocatalytic reactions involving a reductive radical‐polar crossover (RRPCO) generate intermediates with carbanionic reactivity. Many of these proposed intermediates resemble highly reactive organometallic compounds. However, conditions of their formation are generally not tolerated by their isolated organometallic versions and often a different reactivity is observed. Our investigations on their nature and reactivity under commonly used photocatalytic conditions demonstrate that these intermediates are indeed best described as free, superbasic carbanions capable of deprotonating common polar solvents usually assumed to be inert such as acetonitrile, dimethylformamide, and dimethylsulfoxide. Their basicity not only towards solvents but also towards electrophiles, such as aldehydes, ketones, and esters, is comparable to the reactivity of isolated carbanions in the gas‐phase. Previously unsuccessful transformations thought to result from a lack of reactivity are explained by their high reactivity towards the solvent and weakly acidic protons of reaction partners. An intuitive explanation for the mode of action of photocatalytically generated carbanions is provided, which enables methods to verify reaction mechanisms proposed to involve an RRPCO step and to identify the reasons for the limitations of current methods. [ABSTRACT FROM AUTHOR]

The adsorption of ethanol and ammonia changes the basic properties of alumina, and new basic sites are created. Ethanol reacts with surface Al-OH groups, forming ethoxy group Al-O-C2H5. The substitution of Al-OH by Al-O-C2H5 increases the negative charge of neighbouring oxygen atoms, and they became sufficiently basic to react with adsorbed CO2 forming carbonate species CO32−. These carbonates were found to be monodentate and bidentate species. Preadsorption of ammonia also increases the basicity of alumina, but the mechanism is different than for ethanol adsorption. Adsorbed ammonia interacts with surface Lewis acid sites being three-coordinated aluminium atoms. This interaction is accompanied by an electron transfer from ammonia molecules to surface sites, and increases the basicity of the neighbouring oxygens, which can react with the absorbed CO2. The carbonate species formed are polydentate ones. [ABSTRACT FROM AUTHOR]