Addition Of Alkali Metals Research Articles

Effect of Alkali and Alkaline Earth Metallic Species on Gas Evolution and Energy Efficiency Evolution in Pyrolysis and CO2-Assisted Gasification

Abstract In this study, the same moles of alkali and alkaline earth metallic species were introduced into pine wood to investigate their effects on biomass pyrolysis and carbon dioxide-assisted gasification. First, thermogravimetric analysis was conducted to examine the pyrolytic behavior of pine wood loaded with alkali and alkaline earth metallic species. A semi-batch fixed bed platform was used to quantify gaseous product parameters, including gas mass flowrate, gas yield, recovered energy, energy efficiency, and net carbon dioxide consumption. Thermogravimetric results indicated that the loading of alkali and alkaline earth metallic species promoted the thermal decomposition of pine wood at low temperatures, but an inhibitory effect was observed at high temperatures. In terms of pyrolysis, adding alkaline earth metals increased syngas yields, and recovered energy, as well as energy efficiency, whereas alkali metals had the opposite effect. For the gasification, the loading of alkali metals showed a stronger catalytic than the pine wood loaded with alkaline earth metals. Based on the evolution of carbon monoxide, the effects of alkali and alkaline earth metallic species on enhancing the biochar's gasification reactivity were in the sequence of sodium > potassium > calcium > magnesium. In addition, the addition of alkali metals exhibited a stronger capacity for carbon dioxide consumption, which contributed to the management of the greenhouse gas. Considering only energy efficiency, adding alkaline earth metals in biomass pyrolysis is an optimal choice due to the higher overall energy efficiency obtained in less time.

Production of highly reactive cokes by adding alkali metals and alkaline earth metals and their effect mechanism

The influence of alkali metals and alkaline earth metals on coke reactivity and coke microstructure was studied by the mechanical mixing method to produce metallurgical cokes with high reactivity. The Gasification kinetics of coke samples was further studied to clarify the catalytic mechanism of alkali metals and alkaline earth metals on cokes, which provided a basis and guidance for the production of hydrogen-rich blast furnace charge. The chemical reactivity index of cokes increased significantly after adding alkali metals or alkaline earth metals. Meanwhile, CaO had little effect on the structural strength of cokes, while the structural strength of cokes added with K2CO3 and Na2CO3 decreased. The microstructure analysis of different coke samples showed that cokes produced new pores after adding alkali metals or alkaline earth metals, with increased contact area and decreased disorder of cokes. These were the main reasons for the increased reactivity index of cokes. The addition of alkali metals or alkaline earth metals increased the positive reaction rate constant and the effective diffusion coefficient inside cokes by analyzing the kinetic behavior of cokes after adding alkali metals or alkaline earth metals. Furthermore, it reduced gasification reaction resistance and internal-diffusion mass transfer resistance.

Theoretical insight into the promotion effect of potassium additive on the water-gas shift reaction over low-coordinated Au catalysts.

How to elucidate the effect of alkali metal promoters on gold-catalyzed water-gas shift reaction intrinsically remains a challenging, because that the complex synergy effects such as strong metal-support interactions, interfacial effects, and charge transfer of supported metal catalysts makes people difficulty in the understanding the alkali promotion phenomenon in nature. Herein, we report a systematically study of whole water-gas shift reaction mechanism on pure and the K-modified defected-Au(211) (i.e., by removing one surface Au atom from perfect Au(211) and make one model with the Au-Au coordination number is six) by using the microkinetic modeling based on first principles. Our results indicate that the presence of K can increase the adsorption ability of oxygen-containing species via the attractive coulomb interaction, has no significant effect on the adsorption of H species, but inhibits the adsorption of CO due to the steric effect. K promoter stabilizes the water adsorption by ~0.3 eV, which results in one order increasing of whole reaction rate. Interestingly, the strong promotion effect of the K can be assigned to the significant direct space interaction between K and the adsorbate H2O* through the inducted electric field, which can be further confirmed by the posed negative electric field on the unpromoted D-Au(211). Microkinetic modeling results revealed that the carboxyl mechanism is the most likely to occur, redox mechanism is the next one, and the formate mechanism is the least likely to occur. For different kinds of alkali metal additives, the adsorption strength of water molecules gradually weakens from Li to Cs, but Na shows the best promoter behavior at the low temperature. By considering the effect of K contents on the reactivity of water-gas shift reaction, we found that the K with the medium coverage (~0.2~0.3 ML) has the strongest promoting effect. It is expected that the conclusion of this work can be extended to other WGSR catalytic systems like Cu(or Pt). All calculations were performed by using the plane-wave based periodic method implemented in Vienna ab initio simulation package (VASP, version 5.4.4), where the ionic cores are described by the projector augmented wave (PAW) method. The exchange and correlation energies were computed using the Perdew, Burke and Ernzerhof functional with the vdw correction (PBE-D3). The transition states (TSs) were searched using the climbing image nudged elastic band (CI-NEB) method. Some electronic structure properties like work function was predicated by the DS-PAW software. Microkinetic simulation was carried out using MKMCXX software.

A first-principal study of pure and encapsulation boron nitride cluster with alkaline metals as the metformin drug carrier

Finding new drug-delivery materials has attracted considerable interest from many researchers in recent years. Herein, systematic investigation of the metformin interaction with the surface of pristine B12N12 and group I metals (Li, Na, and K) encapsulation nanoclusters was carried out at B3LYP/631++ (d, p) level of theory based on the DFT calculations. MF molecule has two nucleophilic sites, NH and NH2 groups. The trapping of Li, Na, and K atoms affected the HOMO–LUMO gaps of the considered configurations and the electronic properties of considered complexes. Besides, it is noticed that presence of alkali metals remarkably increased the absorption energies of MF-B12N12 to −2.14, −2.24, −2.30, and −2.38 for B12N12, Li@B12N12, Na@B12N12, and K@B12N12 respectively. In addition, DOS plots show a decrease in Egap by the addition of alkali metals and therefore an increase in reactivity of the considered configurations, which is confirmed by the decrease in total hardness.

On the Origin of Tail States and Open Circuit Voltage Losses in Cu(In,Ga)Se2

The detrimental effect of tail states on the radiative and non‐radiative voltage loss has been demonstrated to be a limiting factor for the open circuit voltage (VOC) in Cu(In,Ga)Se2 solar cells. A strategy that has proven effective in reducing tail states is the addition of alkali metals, the effect of which has been associated with the passivation of charged defects at grain boundaries. Herein, tail states in Cu(In,Ga)Se2 are revisited by studying the effect of compositional variations and alkali incorporation into single‐crystal films. The results demonstrate that sodium and potassium decrease the density of tail states despite the absence of grain boundaries, suggesting that there is more to alkalis than just grain boundary effects. Moreover, an increase in doping as a result of sodium or potassium incorporation is shown to contribute to the reduced tail states, which are demonstrated to arise largely from electrostatic potential fluctuations and to be determined by grain interior properties. By analyzing the voltage loss in high‐efficiency polycrystalline and single crystalline devices, this work presents a model that explains the entirety of the voltage loss in Cu(In,Ga)Se2 based on the combined effect of doping on tail states and VOC.

The Promotional Effect of Na on Ru for pH-Universal Hydrogen Evolution Reactions

Alkali metals, as ideal electron donors, can effectively regulate the valence state distribution of the host metals. Nevertheless, no studies have reported the application of alkali metal promoters in the hydrogen evolution reaction (HER). Here, we designed an efficient and wide pH-universal hydrogen evolution catalyst that utilizes alkali metal to control the valence, size, and dispersion of Ru NPs. The experimental results reveal that the alkali metal additives contribute to the dispersion and stabilization of metallic Ru. More importantly, the interaction between Na and Ru regulates the distribution of Ru valence states and helps to form more active components of Ru0. Additionally, NaCl functioned as an in situ template to assist the construction of a porous carbon skeleton promotes mass transfer and exposes more active sites, further promoting the synergistic effect of Ru and Na. As a result, the optimal Ru0.3/C−800 delivers high efficiency for HER with an overpotential as low as 29 mV in 1.0 M KOH and 83 mV in 0.5 M H2SO4 under 10 mA cm−2. Particularly, the catalytic performance of Ru0.3/C−800 even outbalanced that of commercial Pt/C in an alkaline medium. This rational construction strategy opens up new avenues for obtaining superior pH-universal electrocatalysts.

Different alkali metals promoted Cr/Al2O3 catalysts for propane dehydrogenation

Unmodified Cr/Al2O3 and Cr/Al2O3 doping with different alkali metals (Li, Na, K) were prepared by the incipient wetness impregnation method. The surface elements of all the catalysts are evenly distributed and well loaded, and the addition of alkali metals does not change the crystal structure and surface texture. Both Cr6+ and Cr3+ species exist on all catalysts, and the addition of alkali metals can increase the amount of Cr6+ species, and Cr6+ species are basically converted into active Cr3+ species in the reaction thus increasing the initial propane conversion in the reaction. The addition of alkali metals reduced the amount of total acid sites and the strong acid sites of the catalyst, thus inhibiting the occurrence of side reactions and the formation of carbon deposition, and reducing the deactivation rate of the catalyst. Cr-0.5Na/Al2O3 exhibited the best catalytic performance and the lowest carbon deposition.

Theoretical study on dry reforming of methane over a Ni(111) surface under electric fields and with alkali metal additives

The effect of alkali metals that enhance the activity and resistance to carbon deposition of Ni-based catalysts in the DRM reaction by favoring CO2 dissociation can be reproduced by the external negative electric field quantitively.

Effect of alkali metal addition on catalytic performance of Ag/ZrO2/SBA-16 catalyst for single-step conversion of ethanol to butadiene

Alkali addition to a Ag/ZrO2/SBA-16 system for ethanol to butadiene affects a beneficial decrease in Lewis acid sites, mitigating ethanol dehydration. This results in remarkable butadiene selectivity and superior productivity over the lifetime study.

The promoting effect of alkali metal and H2O on Mn-MOF derivatives for toluene oxidation: A combined experimental and theoretical investigation

In this work, different alkali metal (Na or K)-doped manganese-based metal–organic framework (Mn-MOF) derivative materials were obtained from Mn-MIL-100 through ex situ posttreatment method, and their catalytic activities were studied by toluene oxidation. A series of characterization results (N2 adsorption–desorption, X-ray absorption spectroscopy, temperature programmed O2 desorption, etc.) showed that Na-doped Mn-MOF derivatives presented larger specific surface area, lower average manganese valence, and better adsorbed oxygen mobility, which displayed higher catalytic activity. Interestingly, both the addition of alkali metal and the introduction of water in the reaction atmosphere promoted the mineralization of toluene, as demonstrated by in situ diffuse reflectance infrared Fourier transform spectroscopy and thermal desorption-gas chromatography-mass spectrometry. Density functional theory calculations further confirmed that alkali metals and H2O were conducive to the adsorption of toluene, benzyl alcohol, benzaldehyde, benzoic acid and O2. This work provides new ideas for developing high-efficiency and water-promotion Mn-based materials for VOC control.

Effects of Ammonium and Alkali Metal Additives on Anisotropic Photoconductivities and Solar Cell Efficiencies of Two-Dimensional Lead Halide Perovskites

Effects of Ammonium and Alkali Metal Additives on Anisotropic Photoconductivities and Solar Cell Efficiencies of Two-Dimensional Lead Halide Perovskites

Electric and ionic conductivity of potassium antimony tungstate with addition of alkali metals

The electrical conductivity of complex oxides K1-xNaxSbWO6 (0≤x≤0.6) and K1-xLixSbWO6 (0≤ x≤0.4), which have a pyrochlore-type structure, was studied. The temperature dependence of the ion permeability of the compounds and the value of the ion radius were determined. As the ion radius value of the alkali metal decreases, the value of the activation energy decreases, and the ion permeability increases. A model of ion transport has been proposed in these compounds. It was found that the compound containing Li0.4K0.6SbWO6 reaches the maximum values of electrical conductivity.

A Comparative Study of Thermal, Luminous, and Infrared Radiation Characteristics of Natural gas Flame in the Presence of Alkali, Alkali-Earth, and Transition Metallic Solution Additives

Abstract Experiments were performed to find out the effect of alkali, alkali-earth, and transition metallic additives on thermal, luminous, IR, and total radiative properties of natural gas flame. A total of 25 mL of 0.5 M alkali salts of NaNO3 and KNO3, alkali-earth salts of Ca(NO3)2, Ba(NO3)2, and Sr(NO3)2 and transition nitrate salts of Cu(NO3)2 and Mn(NO3)2 (Merck company) were prepared, and flame tests were done on each solution by using a Bunsen burner with the equivalence ratio of 1.05, which is close to the condition of stoichiometric air–fuel mixing. The optical characteristics of flame were measured in visible and infrared radiation (IR) spectrums by a TES-1332A luminance meter, BOMEM FTIR, and IR flame photography technique. Also, the total radiation was gauged by a HFP01 sensor. The results indicated that, in general, due to the increased rate of nucleation of intermediate soot particles, the flame in the presence of alkali metal additives has higher total, luminous, and IR radiation than in the presence of other metal additives. Also, the metallic additives do not significantly change the flame temperature. The results also revealed that although all metallic additives enhance the luminous radiation of flame, which is due to chemiluminescence phenomenon or atomic emission, luminous radiation of metal additives is negligible in comparison with their radiation in IR wavelengths. Furthermore, the results show that the boiling temperature of metallic salt solutions has a greater impact on flame luminosity than their ionization energy does.

Thermal Stability of Potassium-Promoted Cobalt Molybdenum Nitride Catalysts for Ammonia Synthesis

The application of cobalt molybdenum nitrides as ammonia synthesis catalysts requires further development of the optimal promoter system, which enhances not only the activity but also the stability of the catalysts. To do so, elucidating the influence of the addition of alkali metals on the structural properties of the catalysts is essential. In this study, potassium-promoted cobalt molybdenum nitrides were synthesized by impregnation of the precursor CoMoO4·3/4H2O with aqueous KNO3 solution followed by ammonolysis. The catalysts were characterized with the use of XRD and BET methods, under two conditions: as obtained and after the thermal stability test. The catalytic activity in the synthesis of ammonia was examined at 450 °C, under 10 MPa. The thermal stability test was carried out by heating at 650 °C in the same apparatus. As a result of ammonolysis, mixtures of two phases: Co3Mo3N and Co2Mo3N were obtained. The phase concentrations were affected by potassium admixture. The catalytical activity increased for the most active catalyst by approximately 50% compared to non-promoted cobalt molybdenum nitrides. The thermal stability test resulted in a loss of activity, on average, of 30%. Deactivation was caused by the collapse of the porous structure, which is attributed to the conversion of the Co2Mo3N phase to the Co3Mo3N phase.

Investigation of alkali metals addition on the catalytic activity of CuFe2O4 for soot oxidation

• The enhanced soot oxidation activity is ascribed to the formation of surface oxygen vacancies. • The low initial temperature (T ig = 308 °C) and the low temperature of maximum CO 2 emission (T max = 389 °C) were achieved. • DFT calculations were performed to correlate with the activity test results. Soot particle exhausted from diesel engines are causing severe health and environmental problems. Alkali metals (Li, Na, K, Cs) doped CuFe 2 O 4 catalysts were synthesized to eliminate soot residue. XRD, Raman, SEM, H 2 -TPR and temperature-programmed oxidation (TPO) were employed to investigate the effect of alkali metals addition on CuFe 2 O 4 . Density functional theory (DFT) calculations were used to explore the inner reaction mechanism. The results revealed that the doping of all alkali metals facilitated the formation of oxygen vacancies which are the main active sites for soot oxidation. The CuFe 2 O 4 doped by K showed smallest crystal size and the most oxygen vacancies. Therefore, Cu 0.9 K 0.1 Fe 2 O 4 catalyst performed best catalytic activity in soot oxidation with the T ig of 308 °C and T max of 389 °C.

INVESTIGATION OF STRUCTURAL AND DIELECTRICAL PROPERTIES OF SOLID POLY (VINYLIDENE DIFLUORIDE-COHEXAFLUOROPROPYLENE) POLYMER FILM FOR ELECTRO CHROMIC DEVICE APPLICATIONS

An electrolyte for electro chromic device applications was prepared by simple solution cast method. The incorporation of functionalized Alkali metal (Nacl) into poly (vinilydene fluoride-co-hexafluoropropylene): Titanium dioxide (TiO2) in the ratio of 80:5 provided an enhanced dielectrical and structural properties, The casting solution, effects of the solvent and non-solvent in addition of nano scale TiO2 particles and Alkali metal (Nacl) complexes were investigated in this study. After annealing of the PVDF-co-HFP/ TiO2 and AM samples at 1600C, the FTIR study showed many spectral changes including the spectral shift to high wavenumbers and the appearance of new peaks. These spectral changes indicate increasing of crystallinity, strong molecular bonds, and some crystal phase transitions. XRD results showed the change in the crystalline phase of PVdF–co-HFP electrolyte with the addition of surface modified TiO2 and Alkali metal (Nacl). The effect of the TiO2 nanoparticles and Alkali metal (Nacl) surface functionality on the degree of crystallinity of the polymer matrix was analyzed using TGA, scanning electron microscopy (SEM) results the surface morphology and porous nature of the fabricated membrane. The particular polymer electrolyte specimen having 15 wt% Alkali metal (Nacl) exhibited the large values of dielectric constant ' in the low frequency region may be due to an enhanced level of storage of charge carriers at the electrolyte-electrode interface thereby resulting in an increase in the equivalent capacitance. Results show that tends to confirm that the best conducting sample with 15 wt% Alkali metal (Nacl) would possess the maximum number of charge carriers among the five different compositions of NCPE system considered during the present endeavor

Oxidative Dehydrogenation of Propane over Vanadium Catalyst Supported on Alkali-Modifiedx-Al2O3

The propane oxidative dehydrogenation (ODH) reaction has been considered as an alternative method for propene production owing to its exothermic nature, which renders it environmentally friendly. The use of alkaline promoters for supported V catalysts can increase propene selectivity and partially inhibit the formation of CO and CO2. Our goal was to evaluate the promoting effect of K and Na and the support effect using gibbsite as precursor for the propane ODH reaction. Catalysts were prepared via co-impregnation of V and alkali metals on a previously prepared alumina support and were characterized using N2 adsorption-desorption, X-ray diffraction, temperature-programmed reduction, and isopropanol decomposition tests to evaluate their acid-base properties. The activity of the synthesized catalysts for the propane ODH reaction was evaluated at the O2:C3H8:He molar ratios of 5:2:4, 6:1:4, and 4:3:4. The addition of alkali metals to the V catalysts increased propane conversion and propene selectivity; moreover, both parameters increased with increasing molar fraction of O2 in the reactants. K doping increased the propene selectivity of the doped catalysts, because it inhibited a large fraction of catalytic surface acidic sites. A high molar fraction of O2 in the reactants facilitated the regeneration of the catalyst, whereas a high reoxidation rate improved catalytic activity and propene selectivity.

MoS2-Assisted LDI Mass Spectrometry for the Detection of Small Molecules and Quantitative Analysis of Sulfonamides in Serum.

A two-dimensional MoS2 nanosheet was prepared by a chemical exfoliation method and served as an excellent matrix for the detection of small molecules by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). In comparison with organic matrices (CHCA, 3-AQ) and a graphene matrix, we found that a MoS2 matrix showed better performance in analysis of amino acids, peptides, fatty acids, and sulfonamides. A systematic comparison of the MoS2 matrix with both ion modes showed that mass spectra produced in negative ion mode featured a corresponding single deprotonated ion, which was rather different from the complex multiple alkali metal addition peaks present in positive ion mode. In addition, better sensitivity and reproducibility were obtained in negative ion mode. The ionization mechanism of MoS2 as a matrix in negative ion mode was further discussed. The deproton peak intensity of the analyte fatty acid decreased after the addition of the hole-scavenger KSCN, indicating that the ionization of the fatty acid was caused by the Auger complex effect of MoS2 and electron injection. Experiments have shown that the MoS2 matrix detects small molecules with good repeatability and can perform semiquantitative analysis of sulfonamides. Finally, the MoS2 matrix was employed for quantitative determination of sulfamethoxine in serum samples by an internal standard method. This MoS2-assisted laser desorption/ionization mass spectrometry (MoS2-assisted LDI MS) method provides a simple, rapid, high-throughput approach to evaluate the drug levels in the patient serum and can achieve convenient drug therapy monitoring.

Effect of 6 Wt.% Particle (B4C + SiC) Reinforcement on Mechanical Properties of AA6061 Aluminum Hybrid MMC

Aluminum based hybrid metal matrix composite with more than two particle reinforcement is very much popular for heavy duty application, and the proportion of these particle reinforcement can be controlled to achieve desired mechanical properties (strength and wear resistance). AA 6061 alloys popularly used in aircraft and automobile applications, tends to have inferior tribological property and therefore particle reinforcements are being made to strengthen the matrix. The prime objective of this investigation is to study the effect of varying wt.% of proportionate individual reinforcement (SiC and B4C) on the mechanical properties of a particular composition (6 wt.%) of AA 6061 hybrid composite. The present investigation is done to evaluate the dependance of hard particle reinforcements on the strength and elongation behaviour of hybrid composite. Hardness measurement and uniaxial loading techniques were used to characterize the mechanical properties of the as-cast hybrid composites, whereas OM, XRD and SEM analysis was done to study the distribution of reinforcement within the base (AA 6061) metal matrix phase. The improvement in mechanical properties, such as Vickers hardness, UTS, yield strength and elongation were presented and explained using various hypothesis proposed by previous studies. The role of clustering theory and effect of binary eutectic Mg2Si phase found to be key the enhanced mechanical properties of the hybrid composites. Addition of Alkaline Earth Metal (Mg) during the synthesis process have led to an increase in the elongation of hybrid composite with the increase in wt.% of reinforcement which is analogous to the effect of alkali metals (‘Na’ and ‘Li’) addition that helps in refining the Mg2Si Eutectic phase.

Regeneration of deactivated Fe2O3/Al2O3 oxygen carrier via alkali metal doping in chemical looping combustion

In order to reduce the cost of oxygen carriers, alkali metals (K, Na) are used to dope the deactivated Fe2O3/Al2O3 oxygen carrier, thus regenerating the redox activity of the deactivated oxygen carrier. In the case of adding the same molar amount, K could rapidly regenerate the redox performance of deactivated sample. After multiple cycles, the oxygen carrying capacity of deactivated sample doped by 5% K reached the highest oxygen carrying capacity of Fe2O3/Al2O3 before deactivation. The characterization results showed that the surface alkali metal diffused to the inside of the deactivated sample in the continuous cyclic reactions, thus forming a porous structure and then improving the gas-solid reactions in chemical looping combustion. XPS results indicated that the addition of alkali metal was beneficial to increase the content of surface adsorbed oxygen or oxygen vacancies of the deactivated Fe2O3/Al2O3. It strengthened the oxidation ability of the deactivated Fe2O3/Al2O3. In addition, the effect of K content on the regeneration of the deactivated Fe2O3/Al2O3 was also studied. The results showed that the optimum amount of K was 5%. Further increasing the amount of K had no significant effect on the regeneration of the deactivated Fe2O3/Al2O3.