The Kinetics of Lignin Reactions During Oxygen Bleaching. IV. The Reactivities of Different Lignin Model Compounds and the Influence of Metal Ions on the Rate of Degradation

The reactivities of different lignin model compounds with oxygen in alkaline media have been compared. Generally, phenolic structures with a conjugated side chain like stilbene and enol ethers react very rapidly during oxygen bleaching, whereas structures like propylguaiacol and β-aryl ethers are more resistent. Some of the reaction mechanisms involved are probably of a radical type because new crosslinked structures can be formed with even lower reactivity.

The influence of metal ions on the reactivity has also been studied. We have found that Mg²⁺ and transition metal ions like Mn²⁺, Cu²⁺ and Fe²⁺ influence the rate of degradation as well as the rate of dimerization. Most of the metal ions gave a lower rate of degradation as measured at pH 11. The addition of a small amount of hydrogen peroxide to the oxygen alkali system increases the rate of degradation.     

Polarography of some anions in presence of aqueous organic solvent mixtures: Reduction of IO−3 ions in presence of various base electrolytes

The present studies treat with the reduction of IO^?₃ ions different types of base electrolytes at the dropping mercury electrode. All the measurements were done in 0.1 M base electrolytes at 30°C. The effect of various sodium and potassium halides, different cations (alkali and alkaline earth metal chloride), various alkali metal nitrates and some ammonium salts, on the polarographic characteristics of iodate ions, have been studied in details, iR measurements have also been carried out in presence of various oxy-anions and sodium salts of organic acids. In all cases the reduction was found to be diffusion controlled but irreversible. The kinetic parameters have been evaluated by Koutecky's method.     

Effect of ultraviolet irradiation on the selective transport of alkali metal ions through 2,3-epithiopropyl methacrylate–methacrylic acid copolymer membrane

Cationic exchange membranes were prepared with 2,3-epithiopropyl methacrylate (ETMA)–methacrylic acid (MAc) copolymer. Transport of alkali metal ions against their concentration gradient through the membranes was investigated by using the system which contains HCl (left side) and alkali metal solution including two kinds of alkali hydroxides (right side). The effect of ultraviolet (UV) irradiation on the selective transport of alkali metal ions through the ETMA–MAc copolymer membranes was investigated. The membranes were irradiated with a 6-W low pressure mercury lamp at a distance of 10 cm at room temperature in air. The transport selectivity could be increased by using UV-irradiated membranes and the selectivity increased with increasing irradiation time up to 2–3 h, although the transport rate of alkali metal ions decreased with increasing time of UV irradiation. The maximum selectivity of K⁺/Na⁺, Na⁺/Li⁺, and K⁺/Li⁺ were 1.7, 2.0, and 4.2, respectively. In order to explain this phenomena, the effect of UV irradiation on the properties of the membranes was studied. It was concluded that the increase of the selectivity is attributed to the formation of the dense membrane by photocrosslinking of the membrane by UV irradiation.     

The effect of various alkali metal fluoride solutions on the brushite—fluoroapatite transformation

The brushite—fluoroapatite transformation reaction has been examined in 10^?1 M solutions of NaF, KF, RbF, CsF and NH₄F at room temperature. The nature of the alkali metal ion has no effect on the fluoride-diffusion-controlled reaction, although the incorporation of the cation into the apatite structure is dependent the nature of the alkali metal cation.     

Electrochemical properties of modified copper-thallium hexacyanoferrate electrode in the presence of different univalent cations

The preparation of copper(II) hexacyanoferrate (CuHCF) films on the surface of gold electrodes as well as their characterization in solutions of various alkali metal and NH₄⁺ cations and in the presence of thallium(I) are described. The electrochemical quartz crystal microbalance and cyclic voltammetric techniques were used. In 0.50 M lithium nitrate, even at submillimolar concentration of Tl(I), the formal potential of CuHCF was shifted to more positive values. At higher Tl(I) concentrations, the formal potential of the CuHCF redox reaction changed linearly with the logarithm of Tl(I) concentration (in the 0.50 M solution of lithium or another alkali metal nitrate). From such dependencies, selectivity coefficients K_Tl/M were calculated, and they show that the CuHCF film on the gold electrode interacts preferentially with Tl(I). High affinity of Tl(I) to copper hexacyanoferrate, that was observed in the presence of alkali metal cations, was explained by relatively strong donor-acceptor interactions of Tl(I) ions with nitrogen in CN groups of the CuHCF film.It was also shown for simple M₄[Fe(CN)₆] metal ferrocyanate salts (where M = Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺ and Tl⁺) that there is a preferential interaction of Tl⁺ with CN group consistent with formation of a Tl-NC-Fe bridge.     

Extraction of Alkali Metal Cations by Lipophilic Dibenzo-14-crown-4-carboxylic Acids

Abstract

The extraction of alkali metal cations by the lipophilic crown ether, bis-t-octylbenzo-14-crown-4 (BOB14C4), three derivatives of BOB14C4 having pendant carboxylic acid sidearms, and a lipophilic carboxylic acid, 2-methyl-2-heptylnonanoic acid (HMHN) was studied by two-phase potentiometric titration and ion-chromatography. The lipophilic, ionizable crown ethers, BOB14C4-acetic acid (BOB14C4AA), BOB14C4-propanoic acid (BOB14C4PA), and BOB14C4-oxyacetic acid (BOB14C4OAA) extract cations efficiently from aqueous mixed alkali metal chloride solutions into 1-octanol by an ion-exchange mechanism in the range p[H] > 7, as does HMHN. The mode of attachment of the ionizable sidearm, via an ether linkage (BOB14C4OAA) versus a carbon linkage (BOB14C4AA and BOB14C4PA), has a significant effect on the cation selectivity and extraction efficiency of these extractants. BOB14C4 exhibits no p[H] dependent extraction behavior and has no significant effect on the extraction of alkali metal cations by HMHN in a mixture of these two compounds. Although BOB14C4AA and BOB14C4PA extract cations at lower p[H] than HMHN, all three compounds exhibit similar selectivity for Li⁺ over Na⁺, K⁺, Rb⁺ and Cs⁺. A significant reversal in selectivity is observed with BOB14C4OAA, which extracts Na⁺ and K⁺ selectively over Li⁺, Rb⁺, and Cs⁺ and at significanty lower p[H] than BOB14C4AA, BOB14C4PA, or HMHN. The unique behavior of BOB14C4OAA may be attributed to the presence of the ether linkage between the crown ether and the pendant carboxylic acid.     

Application of modified clays in diazotization and azo coupling reactions in water

Diazotization and diazo coupling reaction of a series of aromatic amines and activated aromatic compounds over eco-friendly modified clay catalysts are described. The reaction was catalyzed by modified montmorillonite K-10 including Cu²⁺, Fe³⁺, and Zn²⁺ metal ions. The versatility of this method was checked by using various amines and phenols, which showed reasonable yields of products. These inexpensive, noncorrosive and reusable catalysts were found to exhibit bifunctional catalytic properties for diazotization and diazo coupling reactions. The catalysts could be reused several times without significant loss of their catalytic reactivity.     

Decomposition of phenols in aqueous solution by a UV/O3 process

The decomposition of several non‐biodegradable phenols by the UV/O₃ and ozonation processes was studied and compared under various solution pH values, O₃ input mass flow rates and UV intensities to investigate the removal efficiencies of reactants and organic intermediates. The decomposition rate of phenols by the UV/O₃ process was found to increase with increasing O₃ input dosage, light intensity and solution pH value. The mineralization efficiencies of phenols in aqueous solution would be above 98% under adequate reaction conditions within three hours, but would be retarded for alkaline solutions because of the dissolution of CO₂ formed by mineralization of phenols. The increment of ozone input dosage had little effect on the mineralization of organic intermediates at the latter course of the reaction. The order of the decomposition rate of the phenols used in this research was 2,4‐dichlorophenol > 2‐chlorophenol > 2‐nitrophenol for low and neutral pH solutions, whereas they were nearly alike for alkaline solutions. The two‐step consecutive kinetic model was found to fit well in modeling the behavior of species during the decomposition of phenols in aqueous solutions by the UV/O₃ process.     

Catalytic Upgrading of Phenolic Oil by Etherification with Methanol

Catalytic etherification of phenolic oil with methanol was investigated to decrease the polarity and acidity of the product oil. The catalyst KH₂PO₄/activated alumina (AA) provided the best performance due to its excellent dehydration and anti‐coking property. When catalyzed by KH₂PO₄‐AA, the content of aryl ethers increased with rising temperature during the early stage but decreased at 500 °C. Alkoxy phenols had an inhibiting effect on etherification of alkyl phenols due to adsorption competition. Aryl ethers were mostly generated from alkyl phenols, while alkoxy phenols also contributed by simultaneous conversion to dialkoxybenzenes and diphenols, with a higher selectivity to diphenols. This explained the reduced alkoxy phenols and more generated alkyl phenols and aryl ethers at 350 °C.     

Polymer-bound crown ethers. III. effect of polymeric matrix properties on the rate of crotonization

Condensation of aromatic aldehydes with nitromethane or fluorene in the presence of polymer-bound crown ethers complexed with alkali metal or ammonium salts and hydroxides was used to study the kinetics of these catalytic reactions. The course of the reactions was found to depend on the properties of the polymeric matrix used, the rate of condensation being affected by the sorption of substrates and reaction products and by the swelling capacity of the matrix.     

The hydrogenation of toluene over nickel loaded Y zeolites

The catalytic activities of a range of hydrogen reduced nickel Y zeolites for the hydrogenation of toluene were measured and correlated with the following catalytic parameters: reaction temperature; reaction time; coke deposition. The role of the alkali metal co-cation (Li⁺, Na⁺, K⁺, Rb⁺ or Cs⁺) in influencing the overall hydrogenation activity of the supported nickel metal was probed. The effect of poisoning the surface Bronsted acidity by the adsorption of ammonia is discussed. For comparative purposes, data on the hydrogenation of benzene over the same catalysts are included.     

Studies on syntheses and permeabilities of special polymer membranes

Summary An active transport of alkali metal ion through cation exchange membranes was studied under various conditions. This active transport was facilitated by using a greater anion species on an acidic side in a diaphragm cell, in which one side of the solution was adjusted to be acidic and the other side alkaline across the membrane. An active transport fraction of alkali metal ion was in order poly(styrenesulfonate)>benzenesulfonate>Cl^– >I^–>Br^– of anion species on the acidic side. A rate, fraction and period of the active transport of metal ion were significantly influenced by an electric potential gradient in the membrane.     

Electrochemical Recovery of Lithium Ions in the Aqueous Phase

Abstract

The electrochemical insertion of lithium ions into a Pt/λ-MnO₂ electrode was investigated in various metal chloride solutions. The Li⁺ insertion occurred effectively in LiCl solutions with higher concentration than 10 mmol/dm³, but it could hardly occur in a 0.1 mmol/dm³ LiCl solution. Alkaline earth metal ions showed a stronger inhibition effect against the Li⁺ insertion into the Pt/λ-MnO₂ electrode than alkali metal ions. However, since only Li⁺ ions were taken up from a mixed solution of lithium and alkaline earth metal chlorides, a high selectivity of the electrode for lithium ions was shown.

It was possible to recover lithium ions from geothermal water by this electrochemical method using the Pt/λ-MnO₂ electrode; the lithium uptake was 11 mg/g-MnO₂.     

Ligands for selective metal ion extraction: A molecular modeling approach

We present a density functional theory (DFT) based study on interaction of alkali metal cations (Li⁺ and Na⁺) with macrocyclic crown ethers of different ring sizes. The minimum energy structures, binding energies, and binding enthalpies of crown ether–cation complexes have been determined with a correlated hybrid density functional, namely Becke’s three-parameter functional, B3LYP using a split valence basis function, 6-311++G(d, p). Geometry optimizations for all the crown ether–cation complexes were carried out with several initial guess structures based on semi-empirical PM3 optimized results. For both metal ions, the calculated values of binding energy and binding enthalpy increase with the increase in size of the crown ether ring, i.e. with the increase in the number of donor oxygen atoms in crown ether. The calculated values of gas phase binding energy for lithium ions are always higher than those for sodium ions in the case of all macrocyclic crown ethers studied at present. The calculated values of binding enthalpy are in good agreement with the reported experimental data.     

Studies of activated charcoal cloth. II. Influence of boron-containing impregnants on the rate of activation in carbon dioxide gas

The influence of aqueous solutions of boron-containing compounds as impregnants of viscose rayon cloths on the subsequent activation of the derived carbonised materials in CO₂ gas at 850°C has been studied. The presence of Na⁺ (or other alkali metal ions) is essential for the enhancement of the rate of activation above that observed for the untreated cloth or for the cloth initially impregnated with aqueous boric acid solutions. However, in terms of the activation rate generated, borax is more effective as an additive to boric acid solutions than sodium chloride.The results are interpreted in terms of the catalytic abilities of various alkali metal ions in the systems studied and the complexity of the borate species generated at different pH values in the aqueous impregnant solutions employed.     

DSC and 13C-NMR studies of the imidazole-accelerated reaction between epoxides and phenols

The imidazole-accelerated reaction between epoxides and phenols has been studied through DSC and ¹³C-NMR of model compounds. The selectivity of the accelerator has been found to be strongly dependent on its concentration. If a low amount of accelerator is used, the reaction takes place almost exclusively through the addition of phenols to epoxides even if the latter are used in excess. However, a larger amount of accelerator will cause the secondary hydroxyls (produced by the main reaction) to react with the epoxides. In any case, the lower reactivity of the secondary hydroxyls prevents them from reacting to any significant extent as long as there are any phenols present. When polyfunctional resins are used, the effect of the selectivity of the reaction on the properties of the crosslinked network is very clear. If a low amount of accelerator is used (to promote only the epoxy–phenol reaction), the maximum glass transition temperature (T_g) occurs when the epoxides and phenols are stoichiometrically balanced, reaching 178°C. However, when an excess of epoxides over phenols is used, along with a larger amount of accelarator, the maximum T_g increases its value to 199°C.     

SPOTLIGHT ON MANUFACTURING TRENDS IN JAPAN

Three reactive and functional polymers were synthesized by reacting formaldehyde with the phenolic Schiff bases derived from 4,4′-diaminodiphenylsulfone and o-, m-, and p-hydroxybenzaldehydes, respectively. The metal ion uptake behavior of these resins towards Cu²⁺, Ni²⁺, Co²⁺, and UO₂ ²⁺ ions in dilute aqueous media was studied. The optimum conditions for the absorption of metal ions were determined by varying the various parameters like contact time, size of the sorbents, concentration of the metal ion solutions, and the pH of the reaction medium. Suitable conditions were ascertained for preferential adsorption of the above metal ions from the salt solutions containing other interfering ions such as Na⁺, K⁺, and Mg²⁺. Presence of these alkali and alkaline earth metal ions in the salt solutions did not affect the adsorption behavior of the resins. It was observed that the structural features of the resins have a profound effect on the uptake characteristics. The position of the OH group present in the meta position with respect to the imine nitrogen atom in the resin, demonstrated a significant influence on the extent of metal ion adsorption by the resin. Out of the three resins reported here, the resin derived from the Schiff base of m-hydroxybenzaldehyde-4,4′-diaminodiphenylsulfone showed higher efficiency in uptake of metal ions from the solutions than the corresponding resins derived from the Schiff bases of o- and p-hydroxybenzaldehyde-4,4′-diaminodiphenylsulfone.     

Reduction of vitrinites with lithium in ethylamine and the chemistry of the products

The reduction of a set of hand-picked vitrinite concentrates from various American seams with lithium in ethylamine has been studied. When the extent of reduction is plotted against carbon content and previously reported data are included, there is much scatter. Neither the use of ethylenediamine at 100 °C nor the use of extended reaction times has any consistent effect in increasing reduction. The same is true of the increase in extractability by pyridine. Carbonyl absorption in the infrared spectra of the products is thought to be due to reduction of phenols to cyclohexanones. Aliphatic C-H absorption is greatly increased, as expected. There is tendency for the hydroxyl content of higher-rank coals to increase on reduction and of lower-rank bituminous coals to decrease; this may be due to a change with rank of the relative importance of creation of new phenols by ether cleavage and destruction of phenols by reduction to cyclohexanones. Reduction is accompanied by substantial increases in extractability in chloroform (10–35%). Methyl absorption at 1375 cm^?1 in the infrared spectra of the reduced products is greater than that of the raw coal and is quite intense in chloroform-soluble reduction products, as is ¹H n.m.r. resonance in CDCl₃ solution. Evidently analogues of dibenzyl ether and diphenylethane are cleaved during reduction. N.m.r. spectra detect no aromatic-bound hydrogen in the chloroform-soluble products.     

A catalytic and characterization study of the surface acidity generated on the reduction of copper exchanged Y zeolites

Zeolite acidity, in the form of Bronsted acid sites generated on reducing a range of copper Y zeolites, was probed by infrared spectroscopy. The nature of the alkali metal co-cation (Li⁺, Na⁺, K⁺, Rb⁺ and Cs⁺) is shown to influence both the acid strength and location of the Bronsted sites. Acid strength decreases in the order CuLiY > CuNaY > CuKY > CuRbNaY > CuCsNaY. The specific effect of the alkali metal co-stations on the level of protonic activity in benzene ethylation and cumene cracking is discussed.     

Chloroform as solvent for the complex formation of alkaline salts with crown ethers and cryptands

The complex formation between different crown ethers and the cryptand (2 2 2) with the ammonium and alkali ions was studied in chloroform as solvent using calorimetric titrations. From the reaction enthalpies for the complex formation with 18-crown-6 and the cryptand (2 2 2) as well as from competitive reactions between both ligands no influence of ion pairs can be detected within the experimental error. Stability constants of the complexes formed could only be obtained in case of the complex formation of Na⁺ with benzo-18-crown-6 and of Cs⁺ with most of the ligands.