The dissolution of cellulose in anhydrous chloral/aprotic solvents

Two new approaches toward the chemical modification and rapid dissolution of cellulose pulp in aprotic solvents containing chloral are presented. In the first method, cellulose pulp is water activated and then solvent exchanged prior to the addition of chloral. In the second method, cellulose pulp is heated in refluxing solvent and then cooled to ambient temperature before the addition of chloral. The methods do not entail the use of catalysts but require the preactivation of the pulp prior to treatment with chloral. Clear solutions obtained by the water activation–solvent exchange method were cast into films, and after washing with water the product was soluble in a variety of organic solvents including acetone. IR and NMR (¹H and ¹³C) analyses as well as chemical analyses led to the conclusion that a cellulose chloral hemiacetal with a DS of 2.2 is initially formed which then slowly decomposes upon standing at 23°C to a relatively stable hemiacetal of DS 0.4. Complete regeneration to cellulose results upon standing for an extended period or treatment with 1 N acetic acid at 80°C, 1 N HCl at 50°C, 0.5% NH₄OH or 0.1 N NaOH at 23°C. When solutions, obtained by the hot solvent activation method, were coagulated in water at ambient temperature, regenerated cellulose was obtained. In both methods, little or no degradation of the regenerated cellulose resulted.     

Tetralin pyrolysis under H2 pressure,between 350 and 510°C

The chemistry and kinetics of tetralin thermolysis were experimentally specified under a hydrogen pressure of 8 MPa within a wide temperature range of 350–510°C. The main products are 1-methylindane and n-butylbenzene; out of a total of 16 hydrocarbons identified in the thermolysis products, only benzene, toluene, o-xylene and naphthalene are final. The general order of tetralin thermolysis is 2. The individual orders of isomerization and hydrogenolysis are 0 and 1, respectively. A simplified kinetic model of tetralin thermolysis at the initial stage agrees well with experimental data. The tetralin thermolysis was assumed to begin with a bimolecular transformation into tetralyl and cyclohexadienyl radicals. This is consistent with the facts that the main intermediate products formed from these radicals are 1-methylindane and n-butylbenzene and that the experimentally established activation energy of the total process (59.1 kcal/mol) is close to the thermodynamically evaluated enthalpy of the proposed disproportionation.     

Identification of volatile compounds resulting from the thermal oxidation of polyethylene

The migration of compounds from polymer-based packaging may impart undesirable odors to foods. We, therefore, undertook a study of the volatile compounds produced during the heating of polyethylene (PE) in the presence of excess O₂ at temperatures of 150–350°C and for heating times of 5–15 min. Eightyfour volatile compounds in the range of C₅—C₂₃ were identified by gas chromatography mass spectrometry. The major products were aliphatic hydrocarbons, aldehydes, ketones, and olefins. Changes in temperature and heating times affected the amount and type of compounds produced, with hexanal being found in the largest amount and 300°C resulting in the greatest quantity of volatile compounds. At 350°C, greater amounts and numbers of low-boiling and fewer high-boiling compounds were formed. Only small amounts of volatiles were produced at 150°C. Many of the compounds identified have been reported to have odor and/or toxicological significance. © 1993 John Wiley & Sons, Inc.     

The isothermal degradation of wood

The results of a study of spruce (whitewood) and its organic components (cellulose, hemicellulose, and lignin) by isothermal thermogravimetric analysis in air and inert atmospheres are presented. Data on the thermal decomposition of fuel wood in a temperature range from 200 to 450°C were acquired. The porous structure of biocoal and the process of its evolution were examined by scanning electron microscopy. The porous structure of the whitewood thermally treated at 200 and 300°C had pore sizes from 4 to 15 μm. The stratification of tracheids occurred in the above temperature range. At higher temperatures of 350°C or above, thermal pores with sizes of about 100 nm appeared. As the temperature was increased to 400°C, the pore size increased to 200–300 nm.     

Manufacturing an asphalt-rubber binder for asphalt concrete road pavement via joint thermolysis of crumb rubber with heavy petroleum residues

Thermolysis of heavy petroleum residues (atmospheric and vacuum residua) mixed with crumb rubber obtained via shredding of spent automobile tires was studied, and it was shown that a high-quality asphalt-rubber binder for asphalt concrete road paving can be prepared with the use of this process. Under optimal conditions (temperature 350–415 °C, isothermal holding time 10–20 min, amount of the activator oil shale 2–3 wt %), a 58–60% yield of the asphalt-rubber binder fraction on the basis of the feed mass can be obtained via the thermolysis of heavy petroleum residues in a mixture with 25–40% crumb rubber. The quality of the obtained binder meets the GOST (STate Standard) 9128-97 specifications for road pavements in Russian roadway climatic zone I–II.     

Structure and formation of cellulosic chars

The formation and structure of chars produced on heating of cellulose, lignin, and wood have been investigated by FTIR and CP/MAS ¹³C-NMR, and the results have been discussed in conjunction with parallel permanganate oxidation studies reported before. These data show that when cellulose is heated for 5 min within the temperature range of 325–350°C, the IR bands associated with hydroxyl and glycosidic groups in cellulose disappear, and new bands signal the formation of unsaturation and carbonyl groups by dehydration and rearrangement. The NMR data also show the disappearance of the glycosyl carbons at 60–110 ppm and the appearance of methyl and other paraffinic carbons at 0–60 ppm, aromatic carbons at 110–170 ppm, carboxyl carbons at 170–190 ppm, and carbonyl carbons at 190–220 ppm. On heating at 400°C the IR and NMR signals for the glycosyl groups completely disappear, the signals for carbonyl and carboxyl groups diminish, and those for the aromatic and paraffinic groups expand. At this stage the char contains about 69% aromatic and 27% paraffinic carbons. At the temperature range of 400–500°C the paraffinic carbon content is reduced to 12%, and a highly aromatic (88%) char is produced. This is consistent with the permanganate oxidation studies which show the production of polycyclic aromatic structures resulting from extensive condensation and crosslinking at these temperatures. The chars produced from wood and lignin at 400°C had about the same aromatic carbon content as the corresponding cellulose char; however, the char yields were higher due to the presence of the methoxy phenyl groups that survive the heating process, as indicated by strong NMR signals at 55 and 148 ppm.     

Compositional and structural variations of bitumen and its interactions with mineral matters during Huadian oil shale pyrolysis

Thermal bitumen is an important intermediate derived from kerogen decomposition during oil shale pyrolysis. In this study, free bitumen (FB) and bound bitumen (BB) were obtained by extracting oil shale chars (300–550 °C) before and after demineralization, and then analyzed by liquid chromatography fractionation, Fourier transform infrared spectroscopy, and gas chromatography/mass spectrometry. The FB yield first increased and then decreased with increasing temperature, and the maximum value was 2.10% at 400 °C. The decarboxylation of acids and decomposition of esters at 350–450 °C decreased the content of these compounds. Meanwhile, the intense cracking reactions of aliphatic compounds and alkyl chains at 400–450 °C decreased the carbon chain lengths and molecular weights of these compounds. From the analytical results obtained for the BB fractions, we suggest that some carboxylic acids or carboxyl group-containing compounds may be trapped on carbonate particles by the formation of Ca₂₊COO_? bonds, whereas other oxygenated compounds (e.g., esters and phenols) can be adsorbed preferentially by clay minerals through Lewis acid-base interactions.     

Thermolysis and hydrogenolysis of polyethylene under steam pressure

Thermolysis and hydrogenolysis of polyethylene under steam pressure were carried out by batchwise autoclave in the recovery of liquid petrochemical resources from waste polymers. Thermolysis of polyethylene under steam pressure occurred in the temperature range 400–475°C and reaction pressures up to 213 bar. The presence of steam is advantageous for an increase in liquid products and 450°C is an appropriate temperature for the formation of low molecular aromatic compounds. Hydrogenolysis of polyethylene was studied at 450°C and initial hydrogen pressure range of 10–100 bar under steam pressure. Over 80 wt % of the low-boiling product was converted to saturated hydrocarbons at 40 bar hydrogen pressure, which corresponds to 1 mole hydrogen to 1 mole monomeric unit of polyethylene. The schemes for the thermolysis and the hydrogenolysis, especially the aromatization, are discussed.     

Thermofraktographie – eine neue mikroanalytische Schnellmethode zur Untersuchung von Lipidgemischen

Thermofractography – A Novel Microanalytical Method for the Rapid Analysis of Lipid Mixtures New possibilities now exist for the rapid analysis of lipid mixtures in micro-scale through fractionated carrier gas distillation in direct coupling with the thin-layer chromatography (= Thermofractography). To begin with, the behaviour of pure substances in the temperature gradient 50°–450°C was investigated. It was observed that numerous compounds, which are otherwise separable only via vacuum distillation, pass over with the carrier gas at normal pressure. In this connection, the thermolysis of such compounds was also investigated. Practical cases of application, e. g. fats and oils, mayonnaise, dairy products, chocolate base are given and other possibilities are discussed.     

Hafnium Triflate as an Efficient Catalyst for Direct Friedel–Crafts Reactions of Chromene Hemiacetals

The direct Friedel–Crafts reaction of chromene hemiacetals with indoles, furans and sterically hindered anilines has been accomplished with high selectivity and excellent yields in the presence of a catalytic amount of hafnium triflate [Hf(OTf)₄, 0.1 mol%, 0–40 °C]. The mild conditions tolerate various sensitive functional and protecting groups, and the products were confirmed unambiguously from their spectra and by single‐crystal X‐ray analysis. This direct Friedel–Crafts reaction of chromene hemiacetals should inspire and encourage the consideration of hafnium triflate in the development of mild reaction conditions for the efficient derivatization of hemiacetal‐containing compounds.     

Researches on improving the quality and quantity of the feed for catalytic cracking

Studies have been carried out on the influence of cumene hydroxperoxide at high temperatures on the properties of the atmospheric residue of crude oil and on the composition and quantity of the fraction obtained at 350–490 °C during its vacuum distillation. This treatment results in an increase in the yield of the fraction boiling at 350–490 °C and a decrease in coke and heavy metals contents.     

Study of the thermal-oxidative stability of polybenzoheterocyclic binder

The results of investigating highly thermostable polymer matrices with softening temperatures of 400–450°C are reported. Binders based on a tetranitrile of an aromatic tetracarboxylic acid and bis(o-cyanoamine) are used as polymer matrices. Traditional antioxidants, such as aromatic amines, phenols, and alkyl aryl phosphites, cannot be applied as thermostabilizers. Detailed tests of an efficient stabilizer carborane-containing dinitrile were also unsuccessful because the initial period of retardation in the thermal-oxidative degradation is followed by irreversible changes in the polymer at 350–400°C. Only a new thermostabilizing system based on carborane-containing aromatic compounds with a set of conjugated bonds demonstrates a positive effect. It is established that the developed thermostabilizing system retards the thermal-oxidative degradation and makes it possible to obtain the polymer matrix with a thermal stability of 350–400°C.     

Temperature dependence of indentation size effect,dislocation pile‐ups,and lattice friction in (001) strontium titanate

Nanoindentations with a Berkovich type indenter were performed on (001) strontium titanate (STO) single crystal at 25°C and 350°C, analyzing the influence of temperature on the indentation size effect (ISE) and dislocation structure around the residual impression. It is found that the STO exhibits an ISE, which is strongly reduced at 350°C compared to 25°C. The dislocation structure around the residual impression has been resolved using an etch‐pit technique. At 25°C, the extension of the dislocation pile‐ups were found to be shorter as compared to 350°C. This also correlates with the smaller size effects at 350°C. Peach‐Koehler forces and the elastic‐plastic indentation stress field were used to model the influence of the lattice frictional stress on the dislocation pile‐ups. Based on an equilibrium position of the outermost dislocations, the average lattice frictional stresses were calculated to be 89 MPa and 46 MPa at 25°C and 350°C, respectively.     

ESR studies of free radicals in photo-initiated graft polymerization reactions with cotton cellulose

Electron spin resonance (ESR) spectra of free-radical intermediates formed during photo-initiated graft polymerization reactions of acrylamide, methacrylamide, and diacetone acrylamide onto purified cotton cellulose were recorded. Purified cellulose was saturated with aqueous solutions of the vinyl monomers (0.5M) and then photolyzed under nitrogen by near-ultraviolet light (3100–4100 Å, peak near 3500 Å) at ?196° and 40°C. Other samples of cellulose were saturated with aqueous solutions of the monomers, dried, and then photolyzed at 40°C. In the absence of cellulose, either poorly resolved or no free-radical spectra were generated on photolysis of the monomers. Photolysis of dried cellulose at 40°C and wet cellulose at ?196°C initiated formation of a cellulosic radical that generated a singlet spectrum. Photolysis of wet cellulose at 40°C generated no ESR detectable radical; however, photolysis of wet cellulose that contained monomer at 40°C generated poorly resolved spectra. The ESR spectra of the propagating copolymer radicals recorded were poly(acrylamide), three lines; poly(methacrylamide), five lines; and poly(diacetone acrylamide), two lines (doublet).     

Thermal decomposition of energetic materials. 55. Metal Complexes of Diamioglyoxime as Potential Burn Rate Modifiers in composite propellants

Metal complexes having the potential to modify the burn rate of rocket propellants are described. These are the diaminoglyoxime (DAG) complexes: Co(DAG–H)₂·DAG, Cu(DAG–H)₂·DAG, Ni(DAG–H)₂ and Pd(DAG–H)₂. The thermal decomposition was characterized by DSC, TGA and IR spectroscopy at a heating rate of 5°C/min, and by fast thermolysis/FTIR spectroscopy at 100–250°C/s. The M(DAG–H)₂ complexes are more thermally stable than M(DAG–H)₂·DAG. However, all of the compounds produce highly thermally stable residues which would be expected to retard the heat and mass transfer at a burning surface. The residues most closely resemble coordination complexes of the metal and polymeric cyclic azine compounds. The crystal and molecular structure of the previously unreported complex Ni(DAG–H)₂·HCL is described.     

Thermolysis of brown coal in the presence of alkali metal hydroxides

The thermolysis (≤500°C) of brown coal impregnated with alkali metal hydroxides MOH was studied. Alkalis cause the cleavage of a three-dimensional coal framework into fragments similar to humic acids. The initial rate of the process increases with the diameter of a cation. For the brown coal–KOH compound, an increase in the temperature from 110 to 400°C increased the rate of fragmentation by a factor of ~200 to cause the almost complete (≥90 wt %) decomposition of coal. The promotion of condensational reactions that cause a decrease in the yield of low-molecular-weight volatile organic products is a competing process. In the presence of MOH, the buildup of radicals is changed: a local maximum (at 200–250°C) is formed in the temperature dependence of the concentration of unpaired electrons; the temperature of this maximum and the values of [e ^–] depend on the nature of MOH. In the series of alkalis from LiOH to CsOH, the EPR signal broadened from 0.63 to 0.84 mT due to the formation of semiquinone radical anions and the interaction of an unpaired electron with a cation. A reaction scheme was proposed for the processes of the thermolysis (to 400°C) of brown coal with MOH; it includes the cleavage of a coal framework by the simultaneous heterolysis and homolysis of C–O and C–C bonds with the subsequent formation of a secondary lattice due to polycondensation and radical polymerization.     

Physical agglomeration behavior in preparation of cellulose‐N‐methyl morpholine N‐oxide hydrate solutions by simple mixing

The different melting temperatures of N‐methyl morpholine N‐oxide (NMMO) hydrates in the cellulose–NMMO hydrate solution may be explained by the rather different crystal structures of NMMO hydrates, which are determined by the amount of the hydrates. The preparative process of cellulose–NMMO hydrate solution may result in cellulose structural change from cellulose I to cellulose II, depending on the amount of the hydrate. Mixtures of cellulose and NMMO hydrate in a blender was changed from the granules to slurry with increasing mixing time at 60–70°C, which is below the melting point of the NMMO hydrate. In the case of 15 wt % cellulose–NMMO hydrate granules, which were made by mixing for 20 min, the melting points of various NMMO hydrates were obtained as 77.8°C (n = 0.83), 70.2°C (n = 0.97), and 69.7°C (n = 1.23), respectively, depending on the hydrate number. However, the melting points of cellulose–NMMO hydrate slurry and solution were shifted lower than those of cellulose granules, while the mixing time of slurry and solution are 25 and 35 min, respectively. These melting behaviors indicate instantaneous liquefaction of the NMMO hydrate and the diffusion of the NMMO hydrate into cellulose during mixing in a blender. When cellulose was completely dissolved in NMMO hydrate, the crystal structure of cellulose showed only cellulose II structure. In the cellulose–NMMO products of granules or slurry obtained by high‐speed mixing, which is a new preparation method, they still retained the original cellulose I structure. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1687–1697, 2004     

Obtaining a rubber-bitumen asphaltic concrete pavement binder by the thermocatalytic processing of petroleum residues in a mixture with rubber crumb in the presence of zeolites and organo-mineral activators

It has been ascertained that qualitative rubber-bitumen asphaltic concrete pavement binders can be obtained at one stage by the method of the catalytic thermolysis of residual oil in the mixture with rubber crumb of worn-out tires in the presence of synthetic or natural zeolites or pyroshale that adsorb coke besides catalyzing the process. The mineral part of pyroshale and zeolite powder with adsorbed coke and soot forming during the decomposition of rubber are a thin-disperse modifier of paving bitumens. The catalytic thermolysis of residual oil with adding 30–40% of rubber crumb proceeds under comparatively soft conditions (a temperature of 350–375° C, isothermal exposure with a duration of 10–30 min) in the presence of 1–3% of zeolite or pyroshale. The yield of a high-qualitative rubber-bitumen binder with the content of 18–20% of mineral and organic modifiers can reach 50–60 wt % of the used raw material. Rubber crumb is utilized completely. There are no foreign analogs of the suggested technology. An experimental-industrial installation with a capacity of 9000–10000 t of bitumen component/year was created in the city of Kudepsta in the Krasnodar Territory.     

Thermofraktographie zur Schnellanalyse von Kunststoffen. 2. Mitt. Identifizierung von Phenolharzen

Thermofractography is suitable for the rapid identification of phenolic resins. 3–4 mg of the material to be investigated are heated in the temperature gradient of 150–450°C. The thermofractogram shows the free phenols of the resin in the range of 150–250°C. The phenols developing through thermolysis from the condensation products appear, depending on the corresponding initial phenol, in the range of 300–450°C. The efficiency of the method is demonstrated on several novolaks and phenolresol.     

Fine-tuning of thermal dissociation temperature using copolymers with hemiacetal ester moieties in the side chain: effect of comonomer on dissociation temperature

Synthesis of polymers with hemiacetal ester moieties in the side chain by radical copolymerization of 1-alkoxyethyl methacrylate with various vinyl monomers and their thermal dissociation behavior are described. Radical copolymerization of 1-alkoxyethyl methacrylates with vinyl monomers was carried out in the presence of 2,2′-azoisobutyronitrile at 60°C to afford the corresponding copolymers with hemiacetal ester moieties in the side chain. The thermal dissociation behavior of the obtained copolymers was examined by means of TG–DTA measurements to observe that the dissociation temperatures of hemiacetal ester units depended on their comonomer components. The polarity of the comonomers and the ability to form hydrogen-bonding were key forces to control their thermal dissociation behavior.