Showing papers in "Research on Chemical Intermediates in 1997"

The photo-fenton oxidation : a cheap and efficient wastewater treatment method

Abstract: Advanced Oxidation Processes (AOPs) for wastewater treatment are gaining more importance since biological treatment plants are often not sufficient for highly contaminated or toxic wastewaters. In order to find out the most efficient and cheap AOP, investigations were concentrated on methods that can use sunlight. The systems TiO2/UV, Fe2+/H2O2/UV (Photo-Fenton reaction), Fe2+/O2/UV and Fe2+/O3/UV were compared. Since the Photo-Fenton system was the most effective, pilot plant experiments with industrial wastewaters and sunlight experiments were carried out. Finally a rough cost estimate shows that Photo-Fenton treatment with sunlight is far cheaper than other available AOPs, namely ozonization.

Photocatalytic degradation of naphthalene and anthracene: GC-MS analysis of the degradation pathway

Abstract: The mechanism of the photocatalytic transformation of naphthalene and anthracene has been studied qualitatively in aqueous suspensions of titanium dioxide under UV-irradiation. The degradation products were identified by GC-MS technique. 15 different intermediates have been identified during the photocatalytic degradation of naphthalene. A detailed reaction mechanism is proposed to explain their formation. For the photocatalytic degradation of anthracene phthalic acid and 9, 10-anthraquinone have been found as relatively stable intermediates. Their photocatalytic degradation has been followed in separate experiments to achieve further clarification of the reaction pathway.

Photocatalytic degradation of waste water pollutants. Titanium dioxidemediated oxidation of a textile dye, Acid Blue 40

Abstract: The photocatalyzed degradation of Acid Blue 40, a textile dye, in aqueous suspension of TiO2 has been studied by monitoring the change in dye concentration and formation of carbon dioxide as a function of irradiation time. Mechanistic studies suggest that in addition to the reaction of the hydroxyl and superoxide radicals with the dye, electron transfer from the photoexcited TiO2 to the dye forms a significant pathway in the photodegradation process.

Fullerenes linked to photosynthetic pigments

Abstract: The synthesis and photochemical characterization of two porphyrin-fullerene dyads, two zinc porphyrin-fullerene dyads, and a carotenobuckminsterfullerene are reviewed. In these molecules, the fullerene first excited singlet state may be formed by direct excitation or by singlet-singlet energy transfer from the attached pigment. In polar solvents, the dominant singlet-state decay pathway is photoinduced electron transfer to yield the pigment radical cation and fullerene radical anion. This charge-separated state has a long lifetime relative to the time constant for charge separation. In toluene, in cases where photoinduced electron transfer is slow for thermodynamic reasons, the fullerene singlet state decays by intersystem crossing, and the resulting triplet energy is partitioned between the components of the dyad according to their triplet energies. The results suggest that fullerenes can be valuable components of photochemically active multicomponent molecular systems.

Tio2 photocatalytic degradation of dimethyl- and diethyl- methylphosphonate, effects of catalyst and environmental factors

Abstract: Dimethyl methylphosphonate (DMMP) and diethyl methylphosphonate (DEMP) are readily mineralized by photoexcited titanium dioxide (TiO2). Intermediate products include low molecular weight organic acids and methylphosphonic acid. Complete mineralization yields phosphate and carbon dioxide. The photoactivities of different types of TiO2 were investigated. The decomposition kinetics of DMMP and effects of DMMP and catalyst concentration, sonication, solar irradiation, oxygen concentration, temperature, and hydrogen peroxide on the rate of decomposition are reported. The degradation rates increase with simultaneous sonication, addition of hydrogen peroxide, and at higher temperatures.

Photocatalytic reduction of azo dyes Naphthol Blue Black and Disperse Blue 79

Abstract: Photocatalytic reduction of two textile azo dyes, Naphthol Blue Black (NBB) and Disperse Blue 79 (DB79) has been carried out in colloidal WO3 and TiO2 suspensions. Under bandgap excitation of the semiconductor colloids these dyes undergo irreversible reduction as they react with the trapped electrons. The quantum efficiency for the photocatalytic reduction of these dyes were 5.4% and 4.8% for NBB and DB79 respectively. The kinetics and mechanism of the interfacial charge transfer in these colloidal suspension has been elucidated with transient absorption spectroscopy. The reaction between the dye and trapped electrons is diffusion limited and occurs with rate constants of 1.1×108 M−1s−1 and 4.0×107 M−1s−1 for NBB and DB79 respectively.

Photoinduced electron transfer of fullerenes (C60 and C70) studied by transient absorption measurements in near-IR region

Abstract: Efficiencies and rates of electron transfer from various electron donors to excited fullerenes (C60 and C70) have been determined by observing the transient absorption bands in the near-IR region, where the anion radicals of fullerenes appear. From the rise of the absorption bands of C60 −+ and C70 −+ in the near-IR region, electron transfer takes place via the triplet states (TC60 * and TC70 *) under appropriately low concentrations of electron donors. By analysis of the rise curves C60 −+ and C70 −+, contribution of the excited singlet states (SC60 * and SC70 *) in addition to the route of the triplet states (TC60 * and TC70 *) is confirmed. The quantum yield for electron transfer via the triplet states Φct T was evaluated by the ratio of [C60 −+]/[TC60 *] (or [C70 −+/[TC70 *]). The Φct T depends upon the donor-ability, donor concentration, and solvent polarity. The back electron-transfer process, which was evaluated by observing C60 −+, also depends upon the solvent polarity.

Heterogeneous photocatalytic transformations of s-triazine derivatives

Abstract: Photocatalytic processes arising from irradiated semiconductor oxide suspensions containing 1,3,5-triazine (s-triazine) derivatives are described. Whereas unsubstituted 1,3,5-triazine undergoes hydrolysis, irrespective of the presence of the photocatalyst, other chloro-, amino-, mercapto-, allyloxo-, carboxy- derivatives give rise, in the presence of band-gap excited semiconductor oxide, to nearly stoichiometric formation of 2,4,6-trihydroxy-1,3,5-triazine (cyanuric acid). This last compound is stable toward photocatalytic conditions as well as to ·OH chemically generated in homogeneous solution (H2O2/UV or Fenton's reagent). Only partial conversion in cyanuric acid is observed for 2,4,6-tris(2-pyridyl)-1,3,5-triazine and possible explanation is given. The formation of inorganic species (nitrate, chloride, sulfate and ammonium ions) is reported and the mechanism of their evolution presented.

Sonolytic enhancement of the bactericidal activity of irradiated titanium dioxide suspensions in water

Abstract: Irradiated TiO2 suspensions in water were used to inactivate Escherichia coli and Hansenula polymorpha. Two types of batch reactors employing static and recirculating solutions were used in this study. Sonolysis using a 20 kHz ultrasonic unit was found to enhance the microorganism inactivation in all instances, although the enhancement was more modest for the batch recirculation reactor. These data are interpreted within the framework of four possible mechanisms. The mechanism based on sonolytic creation of ·OH appears to provide the most satisfactory explanation of the data trends. The present data also implicate ·OH as the dominant bactericidal agent in irradiated TiO2 suspensions.

The design of photocatalysts for the removal of NOx at normal temperatures—Copper (I) and silver (I) ion catalysts anchored within zeolite cavities

Abstract: The Cu+/ZSM-5 and Ag+/ZSM-5 catalysts were prepared by a combination of ion-exchange and thermovacuum treatments. In situ photoluminescence, ESR, XAFS, UV-VIS and FT-IR measurements of the catalysts revealed that within the cavity of the ZSM-5 zeolite, the Cu+ ion or Ag+ ion exists in an isolated state. UV irradiation of the catalysts in the presence of NO at normal temperature led to the formation of N2 and O2 for Cu+/ZSM-5 and N2, N2O and NO2 for Ag+/ZSM-5, indicating that the isolated Cu+ ion or Ag+ ion acts as a photocatalyst for the direct decomposition of NO. However, the Cu+/ZSM-5 catalyst loses its photocatalytic reactivity under the coexistence of O2, while the Ag+/ZSM-5 catalyst maintains its reactivity under the coexistence of O2 and H2O.

Photocatalytic degradation of 4-chlorophenol : a mechanistically-based model

Abstract: The photocatalytic degradation of 4-CP was mathematically modelled using the mechanistic insights and data presented in an earlier study [1]. The solution and surface concentrations of reacting species were calculated by solving a system of differential equations that account for oxidation reactions of dissolved and adsorbed species, adsorption and desorption, reduction of oxygen, and hole-electron recombination. The differential equations were integrated over discrete time-periods and annular regions of the photoreactor. The resulting model predicts the trends observed in studies in other laboratories using different experimental apparati. Using the model it is possible to predict effects of reactor geometry, TiO2 loading, light intensity, and mixing on the course of TiO2 photocatalytic oxidation. The model verifies the importance of surface reactions, and reveals the need to better understand the fate and role of oxygen in TiO2 photocatalytic systems.

Kinetics of fullerene triplet states

Abstract: Studies are described whose goal is a quantitative kinetic description of fullerene triplet relaxation The room-temperature intrinsic lifetimes of solution phase T1 C60 and C70 differ substantially, with values in toluene of 143 μs and 12 ms, respectively These decay rates exhibit only weak temperature dependence near room temperature The intrinsic lifetime of T1 C60 has a simple dependence on vibrational energy content up to 1000 K Efficient triplet-triplet annihilation occurs in C60 and C70 solutions at ca 50% of the diffusion-limited rate In mixed solutions, rapid reversible triplet energy exchange was observed between C60 and C70, and between C60 and (CH3)2 C60 A new method for measuring relative triplet enthalpies and entropies in such mixtures has also been applied Complex kinetics has been uncovered in C70 solutions and modeled by reversible formation of shortlived triplet excimers, accounting for the efficient self-quenching C60 self-quenching has been found to be highly temperature dependent, but the mechanism remains unresolved

Femtosecond To Nanosecond Dynamics in Fullerenes: Implications for Excited-State Optical Nonlinearities

Abstract: We compared detailed dynamics of the excited-state absorption for C60 in solution, thin films, and entrapped in an inorganic sol-gel glass matrix. Our results demonstrate that the microscopic morphology of the C60 molecules plays a crucial role in determining the relaxation dynamics. This is a key factor for applications in optical limiting for nanosecond pulses using reverse saturable absorption. We find that the dynamics of our C60-glass composites occur on long (ns) timescales, comparable to those in solution; thin film samples, by contrast, show rapid decay (<20 picoseconds). These results demonstrate that C60-sol-gel glass composites contain C60 in a molecular dispersion, and are suitable candidates for solid-state optical limiting. Multispectral analysis of the decay dynamics in solution allows accurate determination of both the intersystem crossing time (600±100ps) and the relative strengths of the singlet and triplet excited-state cross sections as a function of wavelength from 450–950 nm. The triplet excited-state cross section is greater than that for the singlet excited-state over the range from 620–810 nm.

Intermediate products and reductive reaction pathways in the TiO2 photocatalytic degradation of 1,1,1-trichloroethane in water

Abstract: 1,1,1-Trichloroethane (TCA) has been chosen for the study of the reducing versus oxidizing steps of carbon, involved in the degradation, in UV-irradiated TiO2 aqueous suspensions, of chlorinated alkanes containing two C atoms. At wavelengths > 290 nm, TCA disappearance rate was largely increased in the presence of TiO2. The corresponding apparent first-order rate constant was lower by a factor of only ca. 1.2 than that of nitrobenzene under the same conditions. Within experimental accuracy, the rate of release of Cl ions was equivalent to the TCA disappearance rate, which illustrated the dechlorination efficiency of TiO2, photocatalysis. Indeed, monochloroacetic acid and, at very low concentrations, monochloroacetaldehyde were the only chlorinated intermediate products detected. Analyses by HPLC of aldehydes (2,4-DNPH derivatization) and carboxylic acids allowed the quantification of ten intermediate products containing these functionalities. Glycolic acid (HO−CH2−COOH) was the product that reached the highest concentration. From the practical viewpoint, it is important to emphasize that all the organic intermediate products were progressively oxidized. From the fundamental viewpoint, a discussion on the nature and formation pathways of the intermediate products brings evidence of the coexistence of reduction and oxidation steps involving the organic material; detection of cis-butenedioic acid, however at very low concentrations, indicated the existence of coupling radical reactions.

Vapour phase synthesis of isobutyraldehyde from methanol and ethanol over mixed oxide supported vanadium oxide catalysts

Abstract: The vapour phase synthesis of isobutyraldehyde from methanol and ethanol in one step was investigated over titania-silica, titania-alumina, titania-zirconia, titania-silica-zirconia, and magnesia supported vanadium oxide catalysts at 623 K and under normal atmospheric pressure. Among various catalysts the titania-silica binary oxide supported vanadia provided higher yields than the other single or mixed oxide supported catalysts. The high conversion and product selectivity of V2O5/TiO2-SiO2 catalyst (20 wt% V2O5) was related to the better dispersion of vanadium oxide over titania-silica mixed oxide support in addition to other acid-base and redox characteristics. A reaction path for the formation of isobutyraldehyde from methanol and ethanol mixtures over these catalysts was described.

Radiation Chemical Investigations On Aqueous Solutions of C60(Oh)18

Abstract: The ultraviolet-visible absorption spectrum of C60(OH)18 in water showed an absorption band with λmax = 215 nm and other characteristic absorption bands of C60 are not observed. The singlet-singlet and triplet-triplet absorption bands are not observed in the 400–900 nm region. It has low reactivity with e aq − and formed an absorption band with λmax = 580 nm. The hydroxyl radicals react with a bimolecular rate constant of 2.4×109 dm3 mol−1 s−1 and showed an absorption band at 540 nm.

Electron transfer to buckminster-fullerenes and functionalized fullerene derivatives in aqueous and protic media, as studied by radiolytic techniques

Abstract: The primary radical products, namely C60 *− and C70 *− which were formed by reactions with either the solvated electrons or (CH3)2 *C(OH) radicals exhibit distinct absorption bands in the near-IR. Reaction of a water-soluble C60/γ-cyclodextrin complex with α-hydroxyalkyl radicals and hydrated electrons also involves electron transfer, as indicated by the dependence of the rate constants on the redox potential of the reducing species. Pulse radiolysis of micellar C60 solutions in BRIJ 35 and Triton X-100, on the other, exhibited electron transfer from various reducing radicals to the fullerence core. Water soluble fullerence mono-derivatives, e.g. C60[C(COO− 2]2 (1) and C60(C9H11O2)(COO−) (2) did not show any noticeable reactivity towards strongly reducing species which can be ascribed to the formation of clusters in which the hydrophobic fullerence core is shielded by a surrounding layer of negatively charged carboxylate functions. Upon incorporation into γ-cyclodextrin the reduction of 1 and 2 occurs rapidly as indicated by both an accelerated decay of the hydrated electron absorption and the formation of the characteristic near-IR absorption due to (C60 *−[C(COO−)/γ-CD and (C60 *−) (C9H11O2)(COO−)/γ-CD at 1030 nm. The all-equatorial bis- and tris-adducts, e.g. equatorial-C60[C(COO−)2]2 and equatorial-C60[C(COO−)2]3, did not show any evidence with respect to the occurrence of aggregation phenomena and yielded the respective radical anions equatorial-(C60 *−) [C(COO−)2]n in high yields.

Translational diffusion of intermediate species in solutions

Abstract: In this article, applications of the TG method to measurements of the translational diffusion of photochemically created intermediate species are reviewed. The intermediate species include unstable isomers, photochromic charged molecules, transient radicals created by photochemical reactions, and the electronically photoexcited species. Diffusional behaviors of these intermediates are different from those of stable molecules, which have been investigated extensively so far. The investigations of the diffusion of these species will provide opportunity to reveal the unique intermolecular interaction between the intermediates and matrix. Furthermore, by using products of photochemical reactions as probe molecules, the molecular dynamics of the system can be studied. This information will be valuable for understanding photochemistry in solution.

The thermal decomposition of hydrocarbons. Part 2. Alkylaromatic hydrocarbons: Alkylbenzenes

Abstract: The pyrolysis of the n-alkylbenzenes is reviewed with emphasis on the radical chain mechanism and on the reactions of the intermediate radicals. The effects of the experimental conditions and conversion on the types and distribution of the final products are also evaluated. The Arrhenius rate parameters are summarized for both the elementary steps and the overall decomposition reactions.

Surface species in the direct amination of methanol over Bronsted acidic mordenite catalysts

Abstract: Quantitative in situ infrared spectroscopy in combination with kinetic analysis is utilized to derive mechanistic aspects for the reaction of methanol with ammonia on Bronsted acidic mordenite. Under non-reactive conditions, a coadsorption complex between methanol and ammonia is found, in which only ammonia is in direct interaction with the Bronsted acid sites of the zeolite. This complex is proposed to be the precursor for the formation of protonated methylamines in the zeolite pores which are formed in sequential order up to tetramethylammonium ions. These methylamines are unable to desorb under reaction conditions in the absence of ammonia. They leave the surface either by ammonia adsorption assisted desorption or by scavenging of methyl groups from protonated methylamines by ammonia. Both steps are concluded to be potentially rate determining.

Anion radicals of [60]fullerenes. An EPR study

Abstract: Photochemically induced electron transfer in homogeneous systems (using triethylamine donor) and heterogeneous systems (using photoexcited TiO2 suspension) was applied in in situ reduction of [60]fullerene. The anion radicals generated were characterized by means of EPR and VIS/near-IR spectroscopy. Narrow EPR lines were found. Radical A with gA=2.0000 and peak-to-peak width, ppA=0.09mT was observed as the primary product; followed by its consecutive product B with gB=2.0006, ppB=0.04mT, and in some cases product C with gC=2.0009 and ppc<0.1 mT. Radical A was assigned to [60]fullerene mono-anion, also characterized by a near-IR band at 1077 nm. B is presumably di-anion or a dimeric form of mono-anion. Identical results were also obtained using cathodic in situ reduction. Applying these generation techniques to [60]fullerene derivatives produced narrow EPR lines analogous to those described for pristine [60]fullerene. This was the case not only in organic solvents, but also in aqueous solutions. The results obtained present a contrast with the original ex situ EPR investigations describing [60]fullerene mono-anion with wide lines. According to the results presented here, the narrow and wide EPR lines do not represent contradictory phenomena, but are an integral part of the relatively complicated manifestations of various fullerene states and both will have to be seriously considered in the future.

Radical reactions of C84

Abstract: Pulse radiolysis and steady-state radiolysis experiments describing the radical and electron transfer reactions of C84 are reported here for the first time. C84 reacts readily with radiolytically generated chloromethyl (•CCl3) and trichloromethylperoxyl (CCl3OO•) radicals in CCl4. The formation of the radical adduct has been confirmed from its characteristic absorption in the UV (320 nm) and visible (480 nm). Radical-induced oxidation in 1,2-dichloroethane (1,2-DCE) resulted in a short lived transient absorbing at 920 nm. Reduction of C84 in toluene/2-propanol/acetone could be conveniently followed by formation of an absorption band with an absorption maximum at 960 nm.

Laser flash photolysis studies on radical formation by H-atom abstraction of triplet vitamin K3 and by H-atom transfer via the triplet exciplex between triplet methyldihydroxynaphthalene and benzophenone

Abstract: Nanosecond laser photolysis techniques were incorporated to obtain (1) the absorption spectra and coefficients of triplet vitamin K3 (2-methyl-1,4-naphthoquinone, MNQ) and its ketyl radical (2-methylnaphthosemiquinone, 2MNQH*) in acetonitrile (ACN) as well as to reveal (2) the mechanisms for hydrogen atom abstraction of triplet MNQ (3MNQ*) from phenol which proceeded in a diffusion process with an efficiency of unity On the other hand, the hydroxymethylnaphthoxy radical was produced with the benzophenone ketyl radical (BPK) by the hydrogen atom transfer from triplet 2-methyl-1,4-dihydroxynaphthalene (MDHNp) sensitized by triplet benzophenone to benzophenone (BP) via the triplet exciplex The question to be addressed was, which was produced in the MDHNp-BP system, the 2-methyl or 3-methylnaphthosemiquinone radical? Comparing the absorption spectrum and coefficient of the radical produced via the triplet exciplex with those of the 2MNQH* obtained by H-atom abstraction of 3MNQ*, the radical formed with BPK was revealed to be 2MNQH* The reasons for the preferable formation of 2MNQH* are discussed for H-atom abstraction as well as the transfer reactions

Absorption and Fluorescence Spectra of 9-Anthrol and Its Chemical Species in Solution

Abstract: The absorption, fluorescence, and fluorescence-excitation spectra of 9-anthrol (and/or anthrone) have been observed in various solvents, one of which includes a silicon-aluminium ester (diisobutoxyaluminium triethyl silane[(OBu)2−Al−O−Si−(OEt)3 SAE]). The fluorescence spectra of 9-anthrol shows peak wavelengths at 442 nm in benzene, 454 nm in methanol, 539 nm in triethylamine, and 550 nm in basic solution, which can be assigned to a neutral, a hydrogen-bonded neutral, an ion pair, and an anionic species of 9-anthrol, respectively. In ethanol solution including SAE, on the other hand, a new fluorescence peak appears at 473 nm. This new band originates from a complex formed between 9-anthrol and SAE. The excited-state ion pair is formed through the hydrogen-bonded form in water and the complex form in triethylamine. CNDO/S calculations support the experimental results.

Ground-State Conformational Equilibrium of Previtamin d aNd Its E-Isomer: Effect On the Absorption Characteristics

Abstract: The ground-state conformational analysis of previtamin D, its E-isomer, tachysterol, their 10-desmethyl analogues and 1-methyl-1-hydroxy-previtamins have been performed by force-field calculations Differences in the absorption characteristics of these compounds are discussed in view of the chromophore geometry and abundance (%) of the calculated conformers according to a Boltzmann distribution at 298 K On the basis of present calculations, the red shift of previtamin D low-temperature UV and CD spectra determined earlier is attributed to the shift of conformational equilibrium in favour of more stable cZc geometries The effect of complex formation with simplest model cluster of silica surface ((H3SiO)3SiOH), on previtamin D and tachysterol conformational equilibria and on UV-absorbance maxima has been evaluated

Effects of Si−Al composition on the fluorescence spectra of 1-naphthol during the sol-gel-xerogel transitions

Abstract: A systematic study has been carried out on the characteristic changes in the fluorescence spectra of 1-naphthol doped in the sol-gel-xerogel transition systems comprised of tetraethyl orthosilicate and diisobutoxyaluminium triethylsilicate catalyzed by a small amount of HCl, NH4OH, as well as under uncatalyzed conditions. In the systems containing large amounts of silicon, the fluorescence of 1-naphthol shifts to the red (a predominant emission from the 1La state) during the first stage of the reaction. This red shift indicates an increase in the polarity of the matrix surrounding 1-naphthol. In the second stage of the reaction, the spectrum shifts to the blue (a predominant emission from the 1Lb state), reflecting an increase in the micro-viscosity around 1-naphthol. In the systems containing relatively large amounts of aluminum, however, the spectrum just after mixing shows a larger red shift than that originating from the 1L2 emission. This large red-shifted fluorescence reflects the formation of a complex between 1-naphthol and the −O−Al−O−Si−O-network. The spectrum then shifted to the blue. The spectral behaviours observed indicate that there is a large and dynamic molecular-level change in the physicochemical properties of the matrix surrounding the 1-naphthol molecules during the sol-gel-xerogel transitions of the systems while the gelation phenomenon reflects macroscopic inflexibility although it is completely different from the restriction of movement at the molecular level.

Through bond mechanism versus exciplex formation in the photochemistry of fullerene / ferrocene donor-bridge- acceptor dyads

Abstract: A systematic fluorescence and flash photolytic investigation of a series of covalently linked fullerene / ferrocene based donor-bridge-acceptor dyads is reported as a function of the nature of the bridge between the donor site and acceptor site. The fluorescence of the investigated dyads 2 (Φrel = 0.17 × 10−4, 3 (Φrel = 0.78 × 10−4), 4 (Φrel = 1.5 × 10−4), 5 (Φrel = 0.7 × 10−4), and 6 (Φrel = 2.9 × 10−4) were substantially quenched, relative to N-methyl fulleropyrrolidine (1) (Φrel = 6.0 × 10−4). Photolysis of N-methyl fulleropyrrolidine (1) in toluene revealed formation of the excited singlet state which was followed by a rapid intersystem crossing to the excited triplet state. On the other hand, the fate of the excited singlet state of 2, 3, 4, 5, and 6 was found to be governed by rapid intramolecular quenching, with rate constants of 28×109 s−1, 6.9×109 s−1, and 3.4×109 s−1, 14×109 s−1, 2.3×109 s−1 respectively. The electron transfer process and the charge separation were confirmed by monitoring the characteristic π-radical anion bands at λmax = 400 and 1055 nm in degassed benzonitrile with τ1/2 = 1.8 μs (3) and 2.5 μs (4).

The thermal decomposition of hydrocarbons. Part 3. Polycyclic n -alkylaromatic compounds

Abstract: The pyrolysis of the polycyclic n-alkylaromatic compounds, n-alkylpyrenes, methyl-anthracenes and n-alkylnaphthalenes is reviewed. The types and distributions of the decomposition products and also the mechanisms proposed for their formation are described. The theoretical calculations published on the feasibility of the unique elementary hydrogen transfer step, radical hydrogen transfer, are also discussed.

Catalytic alkylation of 2-naphthol with c1-c3 alcohols

Abstract: The vapour phase alkylation of 2-naphthol with C1−C3 alcohols in the presence of an iron catalyst that contains Cr-, Si- and K-oxides was investigated. 2-Naphthol was methylated in a temperature range 520–645 K giving first 1-methyl-2-naphthol and then 1,3-dimethyl-2-naphthol with total selectivity of ortho-alkylation over 98%. In the cases of ethanol and n-propanol, derivatives of 2-naphthol alkylated in the 1-position were obtained with high yield and selectivity. The reactions were carried out in a continuous process at atmospheric pressure.