Separation and characterization of products from thermal cracking of individual and mixed polyalkenes

Low-density polyethylene (LDPE), polypropylene (PP), and their mixture in the mass ratio of 1: 1 (LDPE/PP) were thermally decomposed in a batch reactor at 450°C. The formed gaseous and oil/wax products were separated and analyzed by gas chromatography. The oils/waxes underwent both atmospheric and vacuum distillation. Densities, molar masses and bromine numbers of liquid distillates and distillation residues were determined. The first distillate fraction from the thermally decomposed LDPE contained mostly linear alkanes and alk-1-enes ranging from C₆ to C₁₃ (boiling point up to 180°C). The second distillate fraction was composed mostly of hydrocarbons C₁₁ to C₂₂ (boiling point up to 330°C). 2,4-Dimethylhept-1-ene was the major component of the first distillate fraction obtained from the product of PP decomposition, while in the 2nd distillate fraction it was 2,4,6,8-tetramethylundec-1-ene. The yields of some gaseous or liquid hydrocarbons obtained by distillation from thermally degraded LDPE/PP differed from the values corresponding to the decomposition of individual plastics due to the mutual influence of polyalkenes during their thermal cracking. Similarly, the yields of propene and methylpropene in the gaseous phase were higher in the case of mixture. Whereas the content of C₉ to C₁₇ alkanes and alkenes in the distillates separated from the liquid mixture obtained by the decomposition of LDPE/PP decreased, the formation of 2,4,6,8,10,12-hexamethylpentadec-1-ene remained unchanged. The corresponding mechanisms of thermal cracking were discussed.     

Production and characterization of the biofuels obtained by thermal cracking and thermal catalytic cracking of vegetable oils

The thermal cracking and the thermal catalytic cracking of soybean oil were evaluated for the production of biofuels as an alternative to fossil fuels. The catalyst proposed for the cracking reaction was bauxite, a high-acidity and low-cost catalyst. The chromatographic profile of the biofuels obtained by cracking showed hydrocarbon compounds such as alkanes, alkenes and aromatics, as well as some oxygenated compounds such as carboxylic acids, ketones and alcohols. The products generated by the thermal catalytic cracking process showed better results than the thermal cracking products because of the low quantity of acids present. The catalyst used was thus shown to act in the secondary cracking process, in which the fatty acids decompose and generate hydrocarbons.     

Determination of sulphur in liquids obtained by thermal cracking of waste polymers and commercial fuels with different analytical methods

Low sulphur concentration in hydrocarbon products as fuels or lubricants is an important requirement for the high quality standards of refineries. A non-polarised energy dispersive X-ray fluorescence spectroscopy (EDXRFS) and sample combustion technique (ASTM D6428-99) was compared. A new application of energy dispersive X-ray spectrometry as analytical method for the determination of sulphur in fuels and fuel-like fractions was investigated. Low sulphur containing fuels and hydrocarbon mixtures obtained by thermal cracking of waste polymers were measured and the influence of C/H ratio on accuracy was studied. The concentration of sulphur in samples was measured with calibration graphs of different hydrocarbon matrices (commercial gasoline, diesel oil and white oil were used). Good correlation was observed between the different methods, but the correlation was depending on the characteristics of the matrices. Detection limits of 1.0 ppm, 1.1 ppm and 0.9 ppm were obtained for S in gasoline, diesel oil and white oil, respectively.     

Photoresponsive inorganic polymers obtained by metal alkoxides

The polymerization of metal alkoxides was carried out in organic solvents and light responsive polymers were obtained. As starting materials for polymerization, Ti(OBu)₄, Zr(OBu)₄, Nb(OEt)₅, and Ta(OEt)₅ were used. The polymerization yield roughly corresponds to the formation of TiO₂, ZrO₂, NbO₂(OEt), and TaO₂(OEt), respectively. The polymers obtained are paramagnetic and all give similar (dark) ESR spectra. When illuminated by visible light, a new ESR absorption is detected in the vicinity of g = 2.00, or 330–340 mT (for 9.450 GHz) region. The formation and decay rates of this ESR absorption was measured. The decay rate constants obtained from the formation curves were larger than those obtained from the decay curves, indicating relatively short lived species are formed during light illumination. The polymers thus prepared have photocatalytic activity and can photolyze 1 : 1 methanol/water system with visible light. Other possible uses of these polymers as paramagnetic or photochromic materials are discussed.     

Petrochemical feedstock by thermal cracking of plastic waste

The thermal cracking is one of the possible ways to obtain petrochemical feedstock from polymer wastes. The properties of the cracking products depend mainly on the type of the raw material. In this study the degradation of different mixtures of polymer wastes (polypropylene and polystyrene) were investigated in a horizontal tube reactor. Temperature of 510–520 °C and residence time of 15–30 min were used. The effects of the concentration of polystyrene on the yields and structure of products were also studied. Moreover, the interaction between the polymers during the pyrolysis was investigated. The products of the thermal cracking were analyzed by gas-chromatography, infrared spectroscopy and different standardized and non-standardized methods.It was found, that the concentration of polystyrene significantly affected both the quantity and quality of degradation products. It was also observed that the presence of the polystyrene in the raw material increased the reaction rate coefficient, and enhanced the degradation rate of polypropylene. By higher concentration of polystyrene in raw materials, the yield of light products considerably increased, furthermore, in the naphtha-like fraction the concentration of aromatics also increased. The characteristics of the products were changed with the polystyrene content in the raw materials. The liquid products had advantageous properties for further utilization as fuel like or petrochemical feedstock applications.     

Structural and thermal investigation of gadolinium gallium mixed oxides obtained by coprecipitation: Observation of a new metastable phase

Polycrystalline gadolinium gallium mixed oxides were prepared by coprecipitation and annealing at various temperatures below 1000 °C. The oxide materials appear to be X-ray amorphous after a heat treatment at 500 °C for 30 h, but after 30 h at 800 and 900 °C a major, unreported, hexagonal phase, isostructural with TAlO₃ compounds (where T=Y, Eu, Gd, Tb, Dy, Ho, Er) appears to crystallize. On the other hand, a highly energetic mechanical treatment of the amorphous powder previously annealed at 500 °C changes considerably the shape and position of exothermal events occurring in the range from 700 up to 900 °C. Subsequent annealing at 900 °C of the mechanically treated powder gives rise to the complete formation of the Gd₃Ga₅O₁₂ garnet structure at the expense of the hexagonal phase and of the minor Gd₄Ga₂O₉ oxide phase. However, a 7.0 wt% contamination is found to be due to tetragonal zirconia coming from vials and balls colliding media. The garnet phase may have strong deviations from the nominal stoichiometry of the garnet, as suggested by the refined lattice parameter obtained from the powder diffraction patterns and by the remarkable absence of intensity relative to the (220) Bragg peak position.     

Microstructure of polymers obtained by cationic polymerization of endo-dicyclopentadiene

endo-Dicyclopentadiene (DCPD) was polymerized by various cationic initiating systems in different solvents. IR and ¹H NMR results show that four types of structural units are formed due to the corresponding addition modes: the addition on the norbornenic (NB) double bond generates unit I and rearranged unit II, while the addition on the cyclopentenic (CP) double bond produces unit III and rearranged unit IV. The reaction medium has a stronger effect on the microstructure of the polymer (PDCPD) than initiating systems. The polymers prepared in toluene and n-hexane contain all four structural units, while the polymer produced in methylene chloride is composed of structural units II and IV. © 1996 John Wiley & Sons, Inc.     

Sorption of phenols by single and mixed cyclodextrin polymers

Cyclodextrin (CD) hydrogels were synthesized by a crosslinking reaction with the same cyclodextrin/epichlorohydrin mole ratio (1/11) using αCD, βCD, γCD, and 50:50 mixtures of α/βCD and β/γCD. In order to investigate the sorption capacity of these hydrogels to different solutes, five model molecules have been selected: phenol, 3-nitrophenol, 4-nitrophenol, 1-naphthol, and the antiinflamatory drug diflunisal. The amounts sorbed have been related to the different affinities of the solutes. 1-naphthol shows the highest affinity for these polymers, especially in the case of sorbents containing βCD. The sorption is considerably poorer for phenol than for its nitro derivatives. The two structural isomers 3- and 4-nitrophenol show significant differences in their affinities towards αCD, βCD and α/βCD. Finally, in the case of diflunisal, a bulkier model molecule, remarkable differences were found on the sorption behaviour by polymers whose cyclodextrins have a similar affinity for this solute (βCD, γCD, and β/γCD).     

A FTIR spectroscopic study of surface acidity and basicity of mixed Mg,Al-oxides obtained by thermal decomposition of hydrotalcite

A hydrotalcite with a Mg:Al ratio of 2.5:1 has been synthesized and characterized. The solids obtained upon calcination of this material at 770 and 1023 K have been also characterized, and have been found to be a mixture of MgAl₂O₄ and MgO. Surface acidity and basicity of the solid calcined at 1023 K have been assessed by FTIR monitoring of pyridine and formic acid adsorption. It has been found that the surface is not acid, although a residual acidity, larger than that in pure MgO, exists. Adsorption of formic acid takes place dissociatively on surface, isolated hydroxyl groups, contrary to previous results with MgO, where dissociative adsorption took place through interaction with exposed oxide ions.     

Adsorption properties of phenolic resin-based mesoporous carbons obtained by using mixed templates of Pluronic F127 and Brij 58 or Brij 78 polymers

Phenolic resin-based mesoporous carbons were synthesized by using mixed templates of Pluronic F127 and Brij 58 or Brij 78. For the purpose of comparison three samples of nanoporous carbons were prepared by using single templates of Pluronic F127, Brij 58 and Brij 78 polymers, respectively. Adsorption properties of the aforementioned carbons were studied by nitrogen adsorption at ?196?°C. The resulting carbons featured high specific surface areas ranging from 641 m²/g for the sample obtained in the presence of Brij 58 polymer to 825 m²/g for the carbon prepared by using a mixed template containing 23% of Pluronic F127 and 77% of Brij 58 and from 588 m²/g for the sample obtained in the presence of Brij 78 polymer to 813 m²/g for the carbon prepared by using Pluronic F127 only. It was shown that the width of mesopores increases with increasing amount of Brij 58 or Brij 78 in the mixture of one of these polymers with Pluronic F127, suggesting that Brij polymers act also as micelle expanders.     

Investigations of thermal elimination reactions of polymers by thermal volatilization analysis and ultraviolet spectroscopy

Using thermal volatilization analysis with differential condensation of volatile products, with film samples on flat-bottomed silica glass reaction tubes to permit measurements of UV spectra of partly degraded polymer, the thermal stability, the types of volatile products and the development of conjugation in the involatile residue have been compared for poly(vinyl chloride), polychloroprene, poly(vinyl acetate) and vinyl acetate/ethylene copolymers, poly(vinyl formate) and poly(vinyl alcohol). All undergo a side-group elimination reaction at lower temperatures, and polyene breakdown occurs in all the samples between 400 and 500°. The longest polyene sequences are formed by PVC. All the polymers except PVC show some complexity of products in the elimination reaction.

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Zusammenfassung Die Anwendung der thermischen Verdampfungsanalyse durch Differentialkondensation der flüchtigen Produkte an Filmproben in flachen Quarzglasreaktionsrohren gestattet die Ermittlung der UV-Spektren von teilweise degradierten Polymeren sowie Aussagen über die thermische Stabilität und Types des flüchtigen Produktes. Die Bindungen in dem nichtflüchtigen Rest wurden untersucht und im Falle der Copolymere Poly(vinylchlorid), Polychloropren, Poly(vinylacetat) und Vinylacetat/Äthylen, weiterhin Poly/vinylformat und Poly/vinylalkohol verglichen. Alle erleiden eine Eliminierungsreaktion an der Seitengruppe bei niedrigeren Temperaturen und Polyenabspaltung zwischen 400 und 500°. Die längsten Polyensequenzen werden durch PVC gebildet. Abgesehen vom PVC zeigten alle übrigen Polymere eine gewisse Komplexität in der Eliminierungsreaktion.

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Résumé L'emploi de la méthode d'analyse par volatilisation thermique avec condensation différentielle des produits volatils, sur des échantillons en film sur tubes de réaction en verresilice à fond plat permet l'examen des spectres ultraviolets des polymères partiellement dégradés et l'étude de la stabilité thermique, outre l'identification des constituants volatils. On a comparé le développement de la conjugaison dans le résidu non-volatil pour les polychlorure de vinyle, polychloroprène, polyacétate de vinyle et les copolymères acétate de vinyle/éthylène, polyformiate de vinyle et polyalcool vinylique. Dans chaque cas, on a observé une réaction d'élimination du groupe latéral à basse température et rupture du polyène entre 400 et 500°. Les plus longues séquences ont été formées dans le cas du PCV. Tous les polymères, excepté le PCV, montrent une certaine complexité de produits dans la réaction d'élimination.

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. (), , , , . , , — - , — . ; 400–500°. . , , .

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Some parts presented at the International Symposium on Macromolecular Chemistry, Budapest, 1969.

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One of the authors (D.L.G.) thanks the Science Research Council for the award of a studentship. Some of the experiments with PVF were carried out by Mr. A. Jamieson. Differential condensation TVA curves were obtained by Mr. R. G. Perrett.     

Physicomechanical properties of grafted polymers obtained by radiation-induced polymerization by radical and ionic mechanisms

The radiation-induced grafting of acrylonitrile, 4-vinylpyridine, and styrene was carried out by both radical and ionic mechanisms. Grafted polymers with equal percentages of graft were obtained by the radical and ionic propagation of the grafted chains. The molecular weight of homopolymers has been determined. The thermomechanical properties of the graft polymers were investigated. The yield temperatures for the graft polymers obtained by ionic propagation of the grafted chains is higher than that of graft polymers obtained by a radical mechanism. This is attributed to the higher molecular weight of the grafted chains obtained by the radiation-induced grafting by the ionic mechanism. The radiation-induced grafting of polyacrylonitrile increases significantly the thermal stability of polyethylene. The differential thermal analysis shows no marked differences in properties of the polymers.     

Kinetics of thermal cracking of light hydrocarbon mixture by pulsed microreactor

The kinetics of thermal cracking of a mixture of hydrocarbons (ethane, propane, isobutane and n-butane) was investigated in a packed-bed pulsed microreactor in the temperature range 600 – 725 °C. The reactor was made up of stainless steel (304) packed with quartz, and nitrogen was used as diluent. From experimental data it was found that all the saturated hydrocarbon, taken together as reactant in terms of total carbon, yielded first-order rates of disappearance to give products which were mainly methane, ethylene and propylene. The values of the Arrhenius factor and activation energy were found to be 4.779 × 10¹¹ s⁻¹ and 214.24 kJ/g mol, respectively. The kinetics of disappearance of individual hydrocarbons and formation of individual products were also investigated. Optimum temperature and residence time conditions for the formation of ethylene and propylene are reported. Surface effects of the packing were not detected when different sizes of packing were used.     

Very high thermal conductivity obtained by boron nitride-filled polybenzoxazine

A thermal conductivity of 32.5 W/mK is achieved for a boron nitride-filled polybenzoxazine at its maximum filler loading of 78.5% by volume (88% by weight). The extraordinarily high conductivity value results from outstanding properties of the polybenzoxazine matrix and the boron nitride filler. The bisphenol-A–methylamine-based polybenzoxazine possesses very low A-stage viscosity which aids in filler wetting and mixing. The filler particles with an average size of ca. 225 μm are large aggregates of boron nitride flake-like crystals. It has bimodal particle size distribution which assists in increasing the particle packing density. This filler–matrix system provides a highly thermally conductive composite due to the capability of forming conductive networks with low thermal resistance along the conductive paths. The SEM picture of the composite fracture surface reveals good interfacial adhesion between the boron nitride filler and polybenzoxazine matrix. Water absorption of the filled systems at 24 h is <0.1% and decreases with increasing filler content.     

Continuous fractionation of polymers in solution by thermal diffusion

The possibility of carrying out continuous fractionation of polymers by the thermodiffusion method was investigated. From the working space of a plate-type column, fractions of polymer were continuously withdrawn simultaneously with filling of the column with fresh solution from a storage vessel. After equilibrium had been established, the distributions of molecular weights of the fractions were determined by a modified Baker and Williams method. In the same apparatus, and at constant temperature and concentration, fractionation, which may be characterized by a limiting viscosity number, is dependent on the total rate of withdrawal and on the ratios of amounts of polymer withdrawn in various places on the column.     

Limiting temperatures of the thermal decomposition of polymers and their determination by rapid thermal analysis

Experimental and theoretical foundations are established for the limiting temperatures of thermal decomposition of thermoplastic polymers. The correlation between the limiting temperatures and the intermolecular interactions of the polymers investigated is reported.

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Zusammenfassung Experimentelle und theoretische Grundlagen der Grenztemperaturen der thermischen Zersetzung von thermoplastischen Polymeren werden behandelt. Es besteht eine Korrelation zwischen den Grenztemperaturen und den intermolekularen Wechselwirkungen der untersuchten Polymere.

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Coordination polymers. XIII. Synthesis and investigation of polymers obtained by the reaction of maleic acid with ZnO

In some cases metal dicarboxylates can be considered as polymers. Formation of crystalline or amorphous polymer depends on the type and ratio of the metal ion to the carboxylate ligand and on the preparation conditions. The “polymer salt” synthesized by the reaction of ZnO and maleic acid shows special feature due to the cis configuration of the dicarboxylic acid. The polymer prepared in a water medium has a fibrillar morphology with a helical structure which is changed by heat treatment: a molecular rearrangement takes place which leads finally to amorphous polymer. The reaction of ZnO and fumaric acid (trans configuration) results in monocrystals containing crystal water or, after heat treatment, in powderlike polymer.     

Copper-iron oxides obtained by thermal decomposition of oxalic coordination compounds

The influence of the coordination architecture (materialized by ligand binding mode and content) on the thermal behaviour of coordination compounds containing copper, iron and oxalic anion as ligand was investigated. It was established that the metal-metal connections influence stronger, comparative with ligand content, the stoichiometry of the thermal decompositions. This revised version was published online in July 2006 with corrections to the Cover Date.     

Aqueous polymerization of methyl methacrylate catalyzed by corundum and characterization of the obtained polymers

The aqueous polymerization of methyl methacrylate (MMA) was studied using sodium bi-sulfite as initiator in the absence and presence of corundum (Al₂O₃). It was found that corundum has a catalytic effect on the polymerization reaction. The polymers obtained in the presence of corundum were found to have a wider molecular weight distribution than in its absence; this was deduced by thin-layer chromatographic analysis in a binary mixture (benzene: methanol 1:1.5 by volume) at 25°C. The apparent energy of activation was calculated between 40 and 50°C, and was found to be 4.50 × 10⁴ and 1.70 × 10⁴ J/mol in the absence and presence of 0.5 g corundum (type 600 grit)/105 mL of the reaction mixture, respectively.