Single Alkali Research Articles

Experimental Studies on Utilization of Prunus armeniaca L. (Wild Apricot) Biodiesel as an Alternative Fuel for CI Engine

In present research work, Prunus armeniaca L. (Wild Apricot) Seed oil has been investigated to produce biodiesel. The free fatty acid (FFA) content of the Prunus armeniaca oil (PAO) was <2%, so a single stage alkali catalyzed transesterification process was used to produce Prunus armeniaca methyl ester (PAME). The transesterification was conducted using optimum condition of 1% (w/w) potassium hydroxide as catalyst, 55 °C reaction temperature and 60 min reaction time with constant stirring at 400 rpm. Transesterification process gave a maximum yield of 96.5% by weight of Prunus armeniaca biodiesel. Fuel properties determined in the study conform to standards set for the ASTM D6751 and EN 14214. PAME exhibited a satisfying oxidative stability of 6.3 h and high cetane number (58.7) compared to petrodiesel (49.7). The experiments were conducted using various blends (B5, B10, B20 and B30) of the methyl ester of PAO with diesel in a single cylinder, four strokes, and direct injection diesel engine. The test results show that the brake thermal efficiency (BTE), in general, was found to be decreased and brake specific fuel consumption (BSFC) increased with increased volume fraction of P. armeniaca biodiesel (PAME) in the blends. A marginally higher BTE and lower BSFC noticed for B5 blend than diesel. At higher load conditions, CO, UHC and smoke opacity were found lower for all PAME blends in comparison to neat diesel. The NOx emissions were found to be increased for PAME based fuel in comparison to neat diesel. It may be concluded from the experimental investigations that PAME, can be an alternative for petrodiesel that can be used in a diesel engine without any major modification in the engine.

(Invited) Synthesis, Kinetics, Characterization and Application of Sodium and Potassium (poly)Selenides for Chalcogenide Semiconductor Doping

Alkali elements are essential for batteries and solar cells. In batteries, alkali ions are typically intercalated in layered 2D structures, such as transition metal sulfides and selenides, in a reversible fashion 1–4. In solar cells based on Cu(In,Ga)Se2 and Cu2ZnSn(S,Se)4 semiconductors, Na2Sex and K2Sex compounds are sources of extrinsic doping and act as surfactants during or after the growth, ending up as segregations at the grain boundaries, where they are also thought to passivate electronic defects 5–10. Alkali (poly)chalcogenide solutions are also traditionally employed for photoelectrochemical characterization of semiconductors because they offer a wide range of redox states 11,12 and stabilize against photoanodic dissolution 13,14. More recently, they have also been adopted as electrolytes in quantum dot sensitized solar cells 15–17. However, despite their technological relevance, little is known about the single alkali selenide compounds beyond the pioneering works of Zintl and Klemm 18,19 and subsequent structural characterizations 20–24. In this presentation, our recent work on (i) synthesis, (ii) characterization (iii) reactivity to oxygen and (iv) utilization of alkali (poly)selenides is reviewed. The synthesis is performed in liquid ammonia at atmospheric pressure and -55 °C. The progress of the reaction is monitored electrochemically, in order to unveil the kinetics. The decrease of solvated electrons concentration after selenium addition is measured directly by means of cyclic voltammetry at the surface of a Pt microelectrode. The compounds are characterised by X-ray photoelectron, Raman and electronic spectroscopies. Broadening of the Se 3d XPS peaks with the increase of the number of Se atoms in the chain suggests a limited extent of negative charge delocalization among the Se atoms in the solid (poly)selenides. A direct band-gap of 1.83 eV and pseudo-direct band-gap of 2.05 eV are identified for Na2Se and K2Se, respectively. The full width at half maximum of the fluorescence emissions is on the order of 300 meV, and the emission peaks occur at more than 0.5 eV below the respected bandgaps, revealing a pronounced defect-assisted radiative recombination. The extreme sensitivity of the compounds to oxidation is studied and discussed with respect to chalcogenide grain boundary passivation. Additionally, extrinsic doping of epitaxial and polycrystalline CuInSe2 films is investigated by means of a novel gas-phase route 25 that utilizes the synthesised compounds. The resulting films are characterised by photoluminescence spectroscopy, revealing the emergence of a distinct peak at ca. 100 meV higher energy than typical 1 eV peak of Cu-poor CuInSe2, irrespective of the alkali source. Lastly, some of the species likely involved in the alkali gas-phase transport and incorporation in CuInSe2are identified for the first time by Knudsen effusion mass spectrometry.

Dy3+ ions doped single and mixed alkali fluoro tungsten tellurite glasses for LASER and white LED applications

A new-fangled series of Dy3+ ions doped Single and Mixed Alkali Fluoro Tungsten Tellurite Glasses have been prepared by using melt quenching technique and their spectroscopic behaviour was investigated by using XRD, optical absorption, photoluminescence and lifetime measurements. The bonding parameter studies reveal the ionic nature of the DyO bond in the present glasses. From the absorption spectra, the Judd-Ofelt (J-O) intensity parameters have been determined and in turn used to determine various radiative properties for the different emission transitions from the 4F9/2 fluorescent level. The photoluminescence spectra of all the glasses exhibit two intensified peaks in blue and yellow regions corresponding to the transitions 4F9/2 → 6H15/2 (483 nm) and 4F9/2 → 6H13/2 (575 nm) respectively. From the photoluminescence spectra, it is observed that the luminescence intensity is maximum for Dy3+ ion doped potassium combination of tungsten tellurite glass (TeWK:1Dy). The highest emission cross-section and branching ratio values observed for the 4F9/2 → 6H15/2 and 4F9/2 → 6H13/2 transitions suggest the possible laser action in the visible region from these glasses. By correlating the experimental lifetimes (τexp) measured from the decay spectral features with radiative lifetimes (τR), the quantum efficiencies (η) for all the glasses have been evaluated and found to be maximum for potassium combination tungsten tellurite (TeWK:1Dy) glass. The CIE colour chromaticity coordinates (x, y), (u, v), colour correlated temperature (CCT) and Y/B ratio were also estimated from the photoluminescence spectra for different compositions of glasses. The chromaticity colour coordinates evaluated for all the glasses fall within the white light region and white light emission can be tuned by varying the composition of the glass. From all these studies, it was concluded that 1 mol% of Dy3+ ions doped TeWK glass is more suitable for lasing and white-LED applications.

Adsorption of alkali and alkaline earth metal atoms and dimers on monolayer germanium carbide

First-principles plane wave calculations have been performed to study the adsorption of alkali and alkaline earth metals on monolayer germanium carbide (GeC). We found that the favourable adsorption sites on GeC sheet for single alkali and alkaline earth adatoms are generally different from graphene or germanene. Among them, Mg, Na and their dimers have weakly bounded to GeC due to their closed valence electron shells, so they may have high mobility on GeC. Two different levels of adatom coverage ( and ) have been investigated and we concluded that different electronic structures and magnetic moments for both coverages owing to alkali and alkaline earth atoms have long range electrostatic interactions. Lithium atom prefers to adsorbed on hollow site similar to other group-IV monolayers and the adsorption results in metallisation of GeC instead of semiconducting behaviour. Na and K adsorption can induce 1 total magnetic moment on GeC structures and they have shown semiconductor property which may have potential use in spintronic devices. We also showed that alkali or alkaline earth metal atoms can form dimer on GeC sheet. Calculated adsorption energies suggest that clustering of alkali and alkaline earth atoms is energetically favourable. All dimer adsorbed GeC systems have nonmagnetic semiconductor property with varying band gaps from 0.391 to 1.311 eV which are very suitable values for various device applications.

Influence of Waste Cooking Oil Methyl Ester Biodiesel Blends on the Performance and Emissions of a Diesel Engine

The present study deals with the performance and emissions of conventional diesel fuel and biodiesel produced from waste cooking oil and their blends (B10, B15). The waste cooking oil methyl esters synthesis has been (WCOME) carried out by a single step alkali catalysed transesterification reaction. Significant physico-chemical properties have been measured and compared against the ASTM D6751 standards. The tests have been performed on a single cylinder, direct injection diesel engine at a constant speed 1500 ± 50 rpm. During the tests, brake thermal efficiency, specific fuel consumption, exhaust gas temperature, exhaust emissions are measured. The experimental results revealed that, relative to diesel, WCOME fuel blends show 1.7–4.14 % decrease in the brake thermal efficiency and 2.18–5.57 % increase in the brake specific fuel consumption due to higher density and kinematic viscosity of WCOME, which reduces the fuel atomization rate. Moreover, most of the constituents of exhaust gas such as CO (13.67–16.89 %) and HC (4.35–11.84 %) along with greenhouse gas such as CO2 (8.34–17.39 %) are reduced in case of all the blends. However, an increase in the NOx emissions (0.3–4.2 %) is mainly due to the higher cetane number of fuel blends, which decreases the ignition delay. The results of this study revealed that WCOME blends show fewer exhaust emissions with a little compromise in the performance of the engine.

Enrichment of Black Ripe Olives in Bioactive Compounds Using a Single Alkali Treatment.

The aim of this work was to develop a method for processing ripe olives with a single NaOH treatment (lye) instead of the well-known 3 lye treatments. Olives of the Hojiblanca variety were processed according to the 2 processes and the color, firmness, flavor, and content in phenolic compounds of the final product were similar in both cases but concentration in triterpenic acids was highest in the olives from the single lye treatment. In this process the concentration of NaOH must range between 20 and 35 g/L, especially to obtain good texture when working at 20 °C. If temperature during the oxidation up to 27 °C the firmness of olives was significantly decreased. The concentration of the NaOH did not exert a high effect on the color of the final product, although firmness decreased as the strength of the lye increased. Higher contents in phenolic compounds and triterpenic acids were also found in the olives processed with the lowest NaOH concentration tested (20 g/L). This new process reduces the volume of wastewaters and energy consumption, and gives rise to a product which is richer in bioactive substances than the traditionally processed one.

Discovery of a Red-Emitting Li3RbGe8O18:Mn4+ Phosphor in the Alkali-Germanate System: Structural Determination and Electronic Calculations.

A solid-state combinatorial chemistry approach, which used the A-Ge-O (A = Li, K, Rb) system doped with a small amount of Mn4+ as an activator, was adopted in a search for novel red-emitting phosphors. The A site may have been composed of either a single alkali metal ion or of a combination of them. This approach led to the discovery of a novel phosphor in the above system with the chemical formula Li3RbGe8O18:Mn4+. The crystal structure of this novel phosphor was solved via direct methods, and subsequent Rietveld refinement revealed a trigonal structure in the P3̅1m space group. The discovered phosphor is believed to be novel in the sense that neither the crystal structure nor the chemical formula matches any of the prototype structures available in the crystallographic information database (ICDD or ICSD). The measured photoluminescence intensity that peaked at a wavelength of 667 nm was found to be much higher than the best intensity obtained among all the existing A2Ge4O9 (A = Li, K, Rb) compounds in the alkali-germanate system. An ab initio calculation based on density function theory (DFT) was conducted to verify the crystal structure model and compare the calculated value of the optical band gap with the experimental results. The optical band gap obtained from diffuse reflectance measurement (5.26 eV) and DFT calculation (4.64 eV) results were in very good agreement. The emission wavelength of this phosphor that exists in the deep red region of the electromagnetic spectrum may be very useful for increasing the color gamut of LED-based display devices such as ultrahigh-definition television (UHDTV) as per the ITU-R BT.2020-2 recommendations and also for down-converter phosphors that are used in solar-cell applications.

Characterization and Bone Differentiation of Nanoporous Structure Fabricated on Ti6Al4V Alloy

The optimal temperature for the alkaline treatment and subsequent heat treatment is determined to optimize the nanoporous structures formed on Ti6Al4V titanium alloy plates. Surface characterization of the alkali‐heat treated samples was performed by scanning electron microscopy, atomic force microscopy, X‐ray photoelectron spectroscopy, and X‐ray diffraction. The effects of heating temperatures on albumin adhesion, rat bone marrow mesenchymal stem cells (BMMSCs) adhesion, alkaline phosphatase activity, osteocalcin production, calcium deposition, and Runx2 mRNA expression were evaluated. The nanotopography, surface chemistry, and surface roughness were unchanged even after heat treatments at 200, 400, and 600°C. Only the amorphous sodium titanate phase changed, increasing with the temperature of the heat treatments, which played a crucial role in promoting superior cell adhesion on the nanoporous surface compared with the sodium hydrogen titanate obtained by a single alkali treatment. The heat treatment at 800°C did not enhance cell attachment on the surface because the nanostructure was dramatically destroyed with the reappearance of Al and V. This study reveals that nanoporous structures with amorphous sodium titanate were fabricated on Ti6Al4V surface through an amended alkali‐heat treatment process to improve BMMSCs adhesion.

Electrochemical Deposition of Alkali Metal in Low-Melting Alkali Metal Perfluorosulfonylamides

Low-melting alkali metal salts have possibility to be molten salt electrolytes for various applications. Depositions of alkali metal in the single molten salts, which correspond to their cathode limits, were investigated by cyclic voltammetry. For example, the single lithium (fluorosulfonyl)(trifluoromethylsulfonyl)amide molten salt showed a pair of reduction and oxidation currents on the nickel electrode at −0.02 V vs. Li+/Li. The order of deposition potential is Na > Li > K > Rb > Cs. This study is the first time for discussion about deposition in the single alkali metal perfluorosulfonylamides.

Aluminum Anodization in the Low-Melting LiAlBr4-NaAlCl4-KAlCl4 Molten Salt

Inorganic chloroaluminate molten salts are of interest as electrolytes for the high-rate plating of aluminum because of their high conductivity and low cost. Unfortunately, low-melting Lewis acidic inorganic chloroaluminate molten salts such as AlCl3-rich AlCl3-NaCl are problematic because of the loss of volatile AlCl3, which restricts their use to sealed systems. Most common Lewis neutral chloroaluminate salts that are based on a single alkali chloride salt, e.g., equimolar AlCl3-NaCl or NaAlCl4, are problematic as well because of their high melting points. However, Hjuler et al.1 described a complex mixture of inorganic haloaluminate salts, LiAlCl4-NaAlCl4-NaAlBr4-KAlCl4 (3:2:3:2) [or LiAlBr4-NaAlCl4-KAlCl4 (3:5:2)] with a melting point of only 86 oC. This Lewis neutral salt was originally formulated for use as an electrolyte for rechargeable Al/molten salt/Ni3S2batteries. The facile electrodeposition of aluminum from this salt was also demonstrated. Any electrolyte solution that is used for the continuous electrodeposition or plating of aluminum normally requires an aluminum anode to resupply the aluminum species that is reduced at the cathode and lost from the solution during the plating process. Much research has been directed at the mechanism of the plating reaction at the cathode in haloaluminate melts, but little attention has been directed to the reactions taking place at the anode. As described in a now classical paper by Holleck and Giner,2passivation phenomena at the aluminum anode may ultimately limit the rate of the plating process in these molten salts as well as their use as battery electrolytes. In this presentation, we describe the behavior of the aluminum anode in the LiAlCl4-NaAlCl4-NaAlBr4-KAlCl4 molten salt at 130 oC. The anodization of Al in this melt is a complex process. Figure 1 shows current - time plots recorded at an Al rotating disk electrode at different applied potentials, E app, versus the equilibrium potential, E eq. (0 V versus Al). As shown in the Levich plots in Fig. 2, for E appup to 0.60 V, the anodization of Al is a mass transport-limited process according to the well-known reversible reaction:Al + 7AlX4 - ↔ 4Al2X7 - + 3e- (1)where X = Cl + Br. However, as E app is increased above this value, the current decreases significantly over a short time period, indicating that the amount of AlX4 - supplied by mass transport is not sufficient to support the reaction in Eq. 1. This results in passivation of the Al anode with AlX3(s) according to the reaction Al + 3AlX4 - ↔ 4AlX3(s) + 3e- (2) Once the Al electrode develops a passive layer, the current reaches a steady-state value determined by the rate of AlX3(s) formation (Eq. 2) and dissolution according to the reaction AlX3(s) + AlX4 - ↔ Al2X7 - (3)The Levich plot in Figure 2 suggests that this dissolution process is also mass transport limited. References 1H. A. Hjuler, S. von Winbush, R. W. Berg, and N. J. Bjerrum, J. Electrochem. Soc., 136, 901-906 (1989). 2G. L. Holleck and J. Giner, J. Electrochem. Soc., 119, 1161-1166 (1972). Acknowledgement This work was funded by the Strategic Environmental Research and Development Program (SERDP) through contract DE-AC05-00OR22725 to Oak Ridge National Laboratory with subcontract to the University of Mississippi.

Bonding in Group 1 Citrate Salts

Computational studies of &gt; 15 new crystal structures and the 10 previously-reported structures of alkali metal citrates provide insight into why the atoms are where they are. The metal-citrate bonding is predominantly ionic, with very little covalent character, which decreases as the cation size increases. Bond valence calculations indicate that most cations are crowded, and that the crowding decreases as the cation size increases. Although most oxygen atoms coordinate to the metals, a few do not, and they tend to be the least-negative oxygens. Both the citrate hydroxyl groups and water molecules tend to bridge two cations, and the carboxylate coordination is more varied. The solid state energy differences are dominated by differences in van der Waals and electrostatic energy contributions. In the Li and Na salts, the citrate anion occurs predominantly in a higher-energy "kinked" conformation, rather than the extended lowest-energy conformation observed in salts of the larger cations. Detailed conformational analysis of the citrate anions enables quantification of the conformational energy costs in these solids. Hydrogen bonding is important to the stability of these salts. The Mulliken overlap population in the hydrogen bonds provides a quantitative measure of their strength, and permits identification of long (weak) interactions which are significant in some of these compounds. Patterns in both the local environments of the hydrogen bonds and the more-extended features (graph sets) are noted. Polymorphs and sets of isostructural compounds permit more-detailed analysis of the structures and energetics in these compounds. The order of ionization of the three carboxylic acid groups is in general central/terminal/terminal, but there are two exceptions. While we have concentrated on salts containing a single alkali metal cation (and hydrogen), the structures of NaK2C6H5O7 and NaKHC6H5O7 provide an exciting window on a larger universe of mixed salts.

Molecular photons interfaced with alkali atoms.

Future quantum communication will rely on the integration of single-photon sources, quantum memories and systems with strong single-photon nonlinearities. Two key parameters are crucial for the single-photon source: a high photon flux with a very small bandwidth, and a spectral match to other components of the system. Atoms or ions may act as single-photon sources--owing to their narrowband emission and their intrinsic spectral match to other atomic systems--and can serve as quantum nonlinear elements. Unfortunately, their emission rates are still limited, even for highly efficient cavity designs. Single solid-state emitters such as single organic dye molecules are significantly brighter and allow for narrowband photons; they have shown potential in a variety of quantum optical experiments but have yet to be interfaced with other components such as stationary memory qubits. Here we describe the optical interaction between Fourier-limited photons from a single organic molecule and atomic alkali vapours, which can constitute an efficient quantum memory. Single-photon emission rates reach up to several hundred thousand counts per second and show a high spectral brightness of 30,000 detectable photons per second per megahertz of bandwidth. The molecular emission is robust and we demonstrate perfect tuning to the spectral transitions of the sodium D line and efficient filtering, even for emitters at ambient conditions. In addition, we achieve storage of molecular photons originating from a single dibenzanthanthrene molecule in atomic sodium vapour. Given the large set of molecular emission lines matching to atomic transitions, our results enable the combination of almost ideal single-photon sources with various atomic vapours, such that experiments with giant single-photon nonlinearities, mediated, for example, by Rydberg atoms, become feasible.

Detection of Yersinia enterocolitica in diarrhoiec stools and environmental samples

Aim: To detect distribution of Yersinia enterocolitica in gastroenteritis cases, in environmental samples and food samples consumed by humans. Materials and Methods: Stool samples, environmental samples comprising water from water pools on the bank of river 'Kabini,' fruit juices from commercial fresh juice centers, pork intestinal contents, drinking water from public eateries, ('paani puri' outlets), public tap water samples and commercial prepacked juices. All samples were cultured by four different methods; direct plating on MacConkey agar, plating following cold enrichment, single alkali and double alkali treatment with KOH & PBS. Results: A total of 181 stool samples and 15 food and environmental samples were processed. Y. enterocolitica was isolated from one stool sample (0.55%) by cold enrichment method and from one water sample collected from river bank (6.6%). Conclusion: Y. enterocolitica is found in humans and in the environment in this region. Adopting a rapid isolation method may infuse interest among clinical microbiologists to undertake an epidemiological study on Y. enterocolitica and Yersiniosis. Unhygienic defaecation habits of the people and movement of swine herds along the river bank may be the source for river water contamination.

On the origin of frequency dispersion at the interface between mercury electrode and aqueous solutions of alkali halides

The origin of frequency dispersion of electrochemical impedance is investigated at the interface of mercury and aqueous solutions of single alkali halides. It is found that in the presence of each one of KI, CsI, CsF and CsBr salts, the interface presents certain potential regions where frequency dispersion effects are detected and others where the ideal capacitor behavior is closely approximated. Frequency dispersion effects are contributed by interfacial processes such as anion and cation adsorption, mercury halide film formation and dissolution and charge transfer reactions. The discrimination between frequency dispersion due to charge transfer processes occurring at the Hg/solution interface and that due to reactant adsorption itself is generally difficult and depends on the reaction mechanism, provided that a discrete adsorption step is anticipated.

Ionic transport in mixed-alkali glasses: hop through the distinctly different conduction pathways of low dimensionality

A feature common to various solids, including single-alkali (SA) and mixed-alkali (MA) glasses, is a frequency-dependent ionic conductivity that shows the power law and the linear behavior with frequency. In spite of the advances made, the origin of this behavior continues to be controversial. We report our measurements of the conductivity of a series of MA borate glasses (Li1−xAx)2B4O7 (A = Na, K, Rb, Cs; 0 ⩽ x ⩽ 1.0) in the frequency range of 100 Hz–15 MHz and in the temperature range from 300 K to less than the glass transition temperature Tg . Using a self-similar spatial structure model, we show that the real process of ionic transport in the SA and the MA glass systems can be described by the fractional kinetic equations containing non-integer integration/differentiation operators. In the procedure of a systematic deduction of the ionic transport in glass systems, we obtained two important insights. Firstly, the time-dependent conductivity σ(t) ∼ exp (t/τc)α reproduces the empirical expression of mean square displacement of the mobile ions 〈r2 (t)〉 ∼tα as a first approximation of ions moving through the fractal pathway and leads to the universal power-law behavior at frequency scales. Secondly, the modified fractional Rayleigh equation with a repulsive interaction provides a quantitative explanation for experimental findings on the SA and the MA glasses. Investigations on the power-law exponent β in the SA and the MA borate glasses indicate that the ions move through the different branches of the fractal structured conduction pathways due to the structural character, associated with a site mismatch effect, and Coulomb blockade by the randomly distributed ions.

Environment-Congenial Biodiesel Production from Non-Edible Neem Oil

In developing countries like India, where edible oils are in short supply, the contribution of non-edible oils like neem as a source for biodiesel production will be of great importance in the coming days. Biodiesel was produced from non-edible neem oil having a free fatty acid content of 19% in a two-step process, as free fatty acid of more than 1% in the feedstock adversely affects the single step alkali catalyzed transesterification process by soap formation. The first step of acid catalysed esterification reduced the free fatty acid content of neem oil to below 1%. The optimum combinations of parameters for pretreatment were found to be 0.60 volume by volume (v/v) methanol-to-oil ratio, 1% v/v H2SO4 acid catalyst and 1 hr reaction time. The next base catalysed transesterification process converted the pretreated oil to neem biodiesel. The optimum combination of parameters for transesterification was found to be 0.24 v/v methanolto-oil ratio, 1.08% weight by volume (w/v) catalyst concentration and 34 min reaction time. This two-step process gave an average yield of 90%. The fuel properties of neem biodiesel were found to be comparable to those of diesel, and conform to the latest American Standards for Testing of Materials Standards.

Alkali pre-treatment of Sorghum Moench for biogas production

AbstractThis work studies the influence of the alkali pre-treatment of Sorghum Moench — a representative of energy crops used in biogas production. Solutions containing various concentrations of sodium hydroxide were used to achieve the highest degradation of lignocellulosic structures. The results obtained after chemical pre-treatment indicate that the use of NaOH leads to the removal of almost all lignin (over 99 % in the case of 5 mass % NaOH) from the biomass, which is a prerequisite for efficient anaerobic digestion. Several parameters, such as chemical oxygen demand, total organic carbon, total phenolic content, volatile fatty acids, and general nitrogen were determined in the hydrolysates thus obtained in order to define the most favourable conditions. The best results were obtained for the Sorghum treated with 5 mass % NaOH at 121°C for 30 min The hydrolysate thus achieved consisted of high total phenolic compounds concentration (ca. 4.7 g L−1) and chemical oxygen demand value (ca. 45 g L−1). Although single alkali hydrolysis causes total degradation of glucose, a combined chemical and enzymatic pre-treatment of Sorghum leads to the release of large amounts of this monosaccharide into the supernatant. This indicates that alkali pre-treatment does not lead to complete cellulose destruction. The high degradation of lignin structure in the first step of the pre-treatment rendered the remainder of the biomass available for enzymatic action. A comparison of the efficiency of biogas production from untreated Sorghum and Sorghum treated with the use of NaOH and enzymes shows that chemical hydrolysis improves the anaerobic digestion effectiveness and the combined pre-treatment could have great potential for methane generation.

On the Phenomenon of Vapor-Phase Combustion of Alkali Metals

Spectra of a burning spray of alkali metals have been analyzed. The Stark effect splitting of the hyperfine components of the sodium diffuse series lines without any applied external electric field is likely to have been obtained. On this basis, a semi-theoretical electrodynamic model of the vapor-phase combustion of single alkali metal particles (droplets) is presented. Such an electrodynamic combustion mechanism is characterized through great increase of both the flame stand-off distance and the lifetime of the burning alkali metal droplets. The total magnitude of the flame stand-off distance by the burning metal droplets is supposed to be composed of more than two-thirds action of the electrodynamic mechanism and smaller than one-third effect of the “ordinary” heat and mass transfer (the Spalding's combustion model). References to analogous spectral and electrical phenomena in papers on vapor-phase metal combustion of different authors are cited. In case of verification of the electrodynamic metal combustion mechanism in some control experiments, it could be purposely applied both in science and engineering.

Catalytic performance of X molecular sieve modified by alkali metal ions for the side-chain alkylation of toluene with methanol

The X molecular sieve catalysts modified by several alkali metal ions for the side-chain alkylation of toluene with methanol were prepared by an ion exchange method, and characterized by low temperature N2 adsorption, DTA, XRD, SEM, FT-IR and 27Al solid NMR. The effects of the reaction conditions (the reaction temperature, space velocity and reactant composition) on the side-chain alkylation of toluene with methanol and the effects of different ions and ratio of SiO2/Al2O3 on the catalytic performance of the KCsX catalyst were investigated. The results show that the X molecular sieve catalyst modified by several alkali metal ions exhibits much higher catalytic performance than the one modified by single alkali metal ions and the catalyst with lower ratio of SiO2/Al2O3 has higher activity for the side-chain alkylation of toluene with methanol. And the acid–base property of the catalyst affects obviously the methanol utilization efficiency and selectivity to product. A low temperature is in favor of increasing the selectivity to styrene, and high space velocity helps to increase the methanol utilization efficiency. With an increase in the reaction temperature, this catalyst would be deactivated due to the coke deposition on the catalyst and the slight structure damage, which results from small part of framework Al has transformed to extra-framework Al.

Nonlinear impedance in oxide glasses containing single and mixed alkali ions

The aim of the present study was to find more clues on the nonlinearities in impedance of oxide glasses. The measurements were conducted in three families of glasses in the frequency range of 1mHz to 10MHz and the temperature range of −120°C to 150°C.The first family of glasses has a composition of FeO–P2O5–Na2O. Oxide glasses containing iron and alkali are well known for a very low alkali ion mobility and may be considered purely polaron conducting. These glasses show no detectable nonlinearities in the impedance spectra. The second was a family of ionic conducting SiO2–Na2O–Al2O3 glasses. The contents of the third harmonics at certain cases reach high values of about 10% at higher temperatures and extremely low frequency region. This may be caused by blocking properties of electrodes. It has been pointed out that such a nonlinearity may imply errors in interpretation of conventional linear impedance measurements. The third family of glasses contained mixed alkali, no detectable nonlinearities in the impedance spectra was found.