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Fluidized-bed reactors crack mixed wastes into valuable raw materials Thermal cracking of mixed-plastics wastes with a fluidized-bed reactor can be a viable and cost-effective means to meet mandatory recycling laws. [...]

Après un aperçu relatif à des essais faits en laboratoire en couches tourbillonnaires de sable, on examine des essais techniques de pyrolyse de matières plastiques.

The pyrolysis of plastic waste, scrap tires and other polymeric materials in a fluidized bed has been carried out based on a scale up program (laboratory plants 70 g/h, 500 g/h, 3000 g/h, and pilot plant 20-50 kg/h). The fluidized bed shows short residence times and high heat and mass transfers, and is heated indirectly up to 600 - 800°C. In the case of poly(methylmethacrylate) (PMMA) or polystyrene as feedstock up to 97 wt.% of the monomer can be recovered. Other polymers give a more unspecific product spectrum. Depending on the process parameters between 30 and 60 % of the polymeric material could be recovered as oil which is comparable to that of a mixture of light benzene and bitumious coal tar if the pyrolysis gas is used as fluidizing gas. The other fractions are gas and a residue containing fillers and impurities (heavy metals). The gas fraction contains mainly methane, ethane, ethene, and propene, the oil fraction benzene, toluene, xylene, and naphthalene.

The synthesis, photophysics, cyclic voltammetry, and highly efficient blue electroluminescence of a series of four new n‐type conjugated oligomers, 6,6′‐bis(2,4‐diphenylquinoline) (B1PPQ), 6,6′‐bis(2‐(4‐tert‐butylphenyl)‐4‐phenylquinoline) (BtBPQ), 6,6′‐bis(2‐p‐biphenyl)‐4‐phenylquinoline) (B2PPQ), and 6,6′‐bis((3,5‐diphenylbenzene)‐4‐phenylquinoline) (BDBPQ) is reported. The oligoquinolines have high glass‐transition temperatures (Tg≥ 133 °C), reversible electrochemical reduction, and high electron affinities (2.68–2.81 eV). They emit blue photoluminescence with 0.73–0.94 quantum yields and 1.06–1.42 ns lifetimes in chloroform solutions. High‐performance organic light‐emitting diodes (OLEDs) with excellent blue chromaticity coordinates are achieved from all the oligoquinolines. OLEDs based on B2PPQ as the blue emitter give the best performance with a high brightness (19 740 cd m–2at 8.0 V), high efficiency (7.12 cd A–1and 6.56 % external quantum efficiency at 1175 cd m–2), and excellent blue color purity as judged by the Commission Internationale de L'Eclairage (CIE) coordinates (x= 0.15,y= 0.16). These results represent the best efficiency of blue OLEDs from neat fluorescent organic emitters reported to date. These results demonstrate the potential of oligoquinolines as emitters and electron‐transport materials for developing high‐performance blue OLEDs.

Nanoparticles such as silica balls (monopheres), calcium carbonate, carbon nanotubes (CNT) or fibers (CF) are uniformly coated with a film of polyolefins of variable thickness using metallocene/methyl‐aluminoxane (MAO) catalysts. The catalyst is adsorbed on the filler surface, leading to a polymer growth directly on its surface. Highly filled and stiff nano composites, basing on polyethene (PE) and syndiotactic or isotactic polypropene (sPP/iPP) with a content up to 85 wt% of silica or 7 wt% of multi‐walled carbon nanotubes (MWCNT) are obtained. MWCNT treated with MAO in the same way form a heterogenous cocatalyst for the preparation of iso‐ and syndiotactic PP/MWCNT composites, too. The uniformity of the dispersion depends primarily on the pretreatment of the filler.

Copolymers of propene and ethene‐based macromers have been prepared in a direct copolymerization. First macromers in a range of 3000–11600 g/mol were synthesized by varying the polymerization temperature and ethene concentration with the metallocene catalyst [(CH3)2CCp2]ZrCl2/MAO. These vinyl terminated ethene oligomers were copolymerized with propene by Cssymmetric catalyst [Ph2C(Cp)(Flu)]ZrCl2to a long‐chain branched syndiotactic polypropylene. The LCB‐sPP was separated from the bimodal product by a fractional crystallization with p‐xylene and 2 ‐ ethoxy ethanol at 130 °C. A detailed analysis of the purified copolymer was given by GPC, DSC and 13C NMR spectroscopy.

Copolymers of ethene and 1‐octene, 1‐dodecene, 1‐octadecene, and 1‐hexacosene were carried out with [Ph2C(2,7‐di‐tertBuFlu)(Cp)]ZrCl2/methylalumoxane as a catalyst to obtain short‐chain branched polyethylenes with branch lengths of 6–26 carbon atoms. This catalyst provided high activity and a very good comonomer and hydrogen response. In this study, the influence of the length and number of the side chains on the mechanical properties of the materials was investigated. The crystalline methylene sequence lengths of the copolymers and lamellar thicknesses were calculated after the application of a differential scanning calorimetry/successive self‐annealing separation technique. By dynamic mechanical analysis, the storage modulus as an indicator of the stiffness and the loss modulus as a measure of the effect of branching on the α and β relaxations were studied. The results were related to the measurements of the polymer density and tensile strength to determine the effect of longer side chains on the material properties. The hexacosene copolymers had side chains of 24 carbons and remarkable material properties very different from those of conventional linear low‐density polyethylenes. The side chains of these copolymers crystallized with one another and not only parallel to the backbone lamellar layer, depending on the hexacosene concentration in the copolymer. The side chains crystallized even at low hexacosene concentrations in the copolymer. A transfer of these results to 16 carbons side chains in ethene–octadecene copolymers was also possible. © 2006 The Authors. Journal of Polymer Science Part A: Polymer Chemistry Published by Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1600–1612, 2006 Copolymers of ethene and α‐olefins with branch lengths of 6–26 carbon atoms were synthesized, and the influence of the length and number of the side chains on the mechanical properties of the materials was investigated. Thermal fractionation of the polymers was performed with a differential scanning calorimetry/successive self‐nucleation and annealing technique; by dynamic mechanical analysis, the mechanical behavior of the materials was studied, and the results were related to the measurements of the density and tensile strength. The 24‐carbon‐long side chains of the ethene–hexacosene copolymers crystallized separately, depending on the comonomer concentration. This led to new copolymers with remarkable material properties.

All relevant 13C NMR signals of two series of seven homogeneous ethylene–propylene copolymers were used to fit the second‐order Markov reactivity ratios of the catalysts and the theoretical feeds. The copolymers cover a very broad range of comonomer incorporations, from about 10 to 93%, and show only primary (1,2) insertions. For both series, solutions are found with reliabilities >>99.5%. The reactivity ratios, r112 = 2.54, r121 = 0.12, r212 = 2.05, and r221 = 0.29 for the used Zirconocone and r112 = 1.69, r121 = 0.32, r212 = 1.56, and r221 = 0.51 for the hafnocene, provide direct information about the metallocenes, the kinetics, and the chain microstructure. With these results, the direct peak method demonstrates that the use of all relevant 13C NMR peaks enables accurate second‐order Markov modeling, revealing subtle differences between copolymers. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 747–755, 2006

Three series of ethylene−propylene copolymers are made using the catalysts (1) rac-[Me2Si(2-Me-4-(1-Naph)Ind)2]ZrCl2/MAO, (2) [Me2Si(Ind)(Flu)]ZrCl2/MAO, and (3) a 1:5 mixture of 1 and 2, all with a broad range of (co)monomer mole fractions in the reactor and copolymers. All three series are analyzed by ¹³C NMR, DSC, and SEC. The ¹³C NMR spectra of the single-site series are the input of the direct peak method to determine the second-order Markov reactivity ratios of the catalysts used. The activities and reactivity ratios of the catalysts in the single-site experiments are used to model the dual-site series based on ¹³C NMR data. The results of this modeling are used to interpretate the DSC and SEC data of the dual-site series:  most of the melting peak temperatures and molar masses of the dual- site can be attributed to one of the two catalysts.

A number of novel C1-symmetric metallocenes based on substituted fluorenyl and indenyl ligands, [dimethylsilyl(2,7-di-tert-butyl-9-η⁵-fluorenyl)(1-η⁵-indenyl)]zirconium dichloride (3), [dimethylsilyl(1,1,4,4,7,7,10,10-octamethyl-1,2,3,4,7,8,9,10-octahydrodibenzo[b,h]-9-η⁵-fluorenyl)(1-η⁵-indenyl)]zirconium dichloride (5), and [dimethylsilyl(1,1,4,4,7,7,10,10-octamethyl-1,2,3,4,7,8,9,10-octahydrodibenzo[b,h]-9-η⁵-fluorenyl)(2-methyl-1- η⁵-indenyl)]zirconium dichloride, and the analogue complexes with a Ph2Si bridge (4, 6, and 8) have been synthesized and used for alternating ethene/propene copolymerizations and compared to the unsubstituted complexes 1 and 2. With growing sterical demand of the substituents, the activities of the catalysts at moderate temperatures decrease strongly, but a very high-temperature stability is achieved. Usage of catalyst species with a Ph2Si instead of a Me2Si bridge leads to higher activities and molar masses. The percentages of alternating triads are high for all catalysts and are decreasing with growing polymerization temperature. Surprisingly, the catalysts with the bulky substitution at the fluorene ring (5−8) yield at 15 and 0 °C copolymers with a lower alternating part than at 30 °C.

Branch contents in sparsely short-chain branched polyethylenes (<C28) and end-group concentrations in linear polyethylenes were investigated by solid- and melt-state ¹³C NMR using model copolymers of 1-octene, 1-octadecene, 1-hexacosene, and linear PE standards. Benchmark measurements were established for single-pulse acquisition under MAS on these melts at 423 K, using 7 mm ceramic rotors and commercially available solid-state probes at 300 and 500 MHz ¹H Larmor frequency. Signal improvement by a factor of 3−4 was observed, corresponding to a factor 10 reduction in measurement time, when compared to a reference solution-state (400 MHz ¹H) measurement. Transient NOE effects due to proton decoupling during FID acquisition were found to affect significantly the accuracy of branch content determination and end-group analysis in the melt spectra, even at moderate pulse repetition rates. ¹³C T1 and NOE buildup rates and intensity variations were established at 423 K and correlated to the local packing of the branched chain architecture. CP/MAS spectra at and below room temperature on the solid-state polyethylenes showed good agreement with reference spectra, providing an alternative method for sensitivity improvement, with about a factor of 10 saving in measurement time as compared to the melt measurements. Using an optimized parameter set, molecular weight determination of a linear polyethylene standard with Mn>100 000 g/mol was shown to be feasible in both solid-state and melt measurements in less than a one-day measurement, obtained on a 500 MHz spectrometer and 4 mm rotor. Using this enhanced signal intensity, NMR relaxation times were investigated in the melt with respect to their inherent sensitivity to the branching architecture. These measurements included T1ρ, T1, and T1^NOE. It was found that T1^NOE seems to have the best sensitivity to determine the approximate length of the side chain branches for n > 6.

The synthesis of long-chain branched polyethylene by copolymerization of ethylene with higher α-olefins has its limitations due to commercial availabilities of pure α-olefins above carbon lengths of C30. Soga¹ and Bazan² have shown the possibility of inserting side chains up to a length of 60 carbons into a growing polyethylene backbone. The details of combining [Me2C(Cp)2]ZrCl2 (1) and [Me2Si(N^tBu)(Me4Cp)]TiCl2 (2) to obtain long-chain branched polyethylene with branch lengths up to 350 carbons as well as the copolymerization profile and purification of the product throughout the Kumagawa extraction are discussed here. Compound 1 was used in a first oligomerization step to yield a macro-comonomer. Three different methods involving conventional copolymerization, tandem polymerization, and simultaneous entry of the catalysts were examined using 2 and MAO as cocatalyst to copolymerize different macro-comonomers with ethylene.

The hydroalumination of the allyl ethers CH2&dbd;CHCH2OR with ⁱBu2AlH yields the (3-alkoxypropyl)diisobutylaluminum complexes ⁱBu2Al(CH2)3OR (R = Me (1), Et (2), Bu (3)). Et2AlCl and ⁱBu2AlCl react with (2-(methoxymethyl)phenyl)lithium and (2-methoxybenzyl)magnesium chloride, yielding (2-(methoxymethyl)phenyl)diethylaluminum (4), (2-(methoxymethyl)phenyl)diisobutylaluminum (5), and (2-methoxybenzyl)diisobutylaluminum (7), respectively. The reaction of ⁱBu2AlCl with (2-methoxyphenyl)lithium affords the dimeric bis((2-methoxyphenyl)diisobutylaluminum) (6). Et2AlCl and (8-ethoxynaphthyl)lithium form (8-ethoxynaphthyl)diethylaluminum (10) along with a few crystals of bis(8-ethoxynaphthyl)aluminum chloride (13). AlCl3 reacts with 2 equiv of (2-methoxybenzyl)magnesium chloride, yielding bis(2-methoxybenzyl)aluminum chloride (9). Ligand redistribution followed by metathesis was observed for the reactions of Me2AlCl and Et2AlCl with (2-methoxybenzyl)magnesium and (8-methoxynaphthyl)lithium, yielding bis(2-methoxybenzyl)methylaluminum (8), bis(8-methoxynaphthyl)methylaluminum (11), and bis(8-methoxynaphthyl)ethylaluminum (12), respectively. The new compounds have been characterized by elemental analysis, NMR spectroscopy, and mass spectrometry. The solid-state structures of 6, 8, 9, and 11−13 were determined by single-crystal X-ray diffraction. The new aluminum alkyls are very active cocatalysts in the TiCl4-catalyzed ethylene polymerization. 7 and 10 cause a higher productivity compared to the common cocatalyst Al2Et6. The activity depends strongly on the structure of the oxygen-stabilized aluminum alkyls and is also influenced by the Al/Ti ratio.

Three olefin polymerization catalysts are supported onto a flat silica wafer employing spin-coating impregnation. These model catalysts feature a defined surface direction of the silica support and thus facilitate the direct correlation between catalyst dispersion and morphology of the polymer product. Depending on the interaction of the catalysts with the silica surface, the catalysts disperse in very different fashions, which induces different constraints on the polymer growth upon gas-phase polymerization. Chemical anchoring of the active species as in the CrOx/SiO2 (Phillips) system results in homogeneous polymer film of up to several 10 μm . In contrast the physisorbed Cp[1,3-(2,6-Me2C6H3)2C2H4N2C&dbd;N]TiBz2B(C6F5)3 forms clusters on the flat silica that evolve into highly porous, ball-shaped polymer beads. rac-[Me2Si(2-Me-4-(1-Naph)Ind)2]ZrCl2(CH3AlO)x forms a film of metallocene catalyst dispersed inside the cocatalyst matrix. Homogeneous regions of this film give rather homogeneous polymer films while local concentrations of active species (hotspots) form crater- and ball-shaped structures.

A continuous fluidized‐bed plant (PDU‐scale) for fast pyrolysis of lingnocellulosic biomass gives rise to bio‐oil yields of 65 wt.‐%. The average reactor gas residence time was 1.2 s only. The gas and charcoal yields were 15–20 wt.‐%, respectively. The bio oils were chemically characterized. The main monomeric products of the thermal degradation of carbohydrates are acetic acid, hydroxyacetaldehyde, hydroxypropanone, and levoglucosan. The process described in this paper can also be used for disposal of inorganic‐, metal‐organic‐, and chlorine‐organic contaminated waste‐wood. Inorganic compounds of wood preservatives are concentrated in the charcoal fraction and can be separated easily. Chlorine‐organic wood preservatives are mostly degraded. The process has been positively tested as a technique for disposal, recycling, and exploitation of industrial biomass waste (wood waste, grinding grit, fibre sludge, cocoa shell and modern composites like HPL). Bio oil from fast pyrolysis can be used for the production of energy and chemical feedstock. Research for these purposes is ongoing.

Measurement of optical rotation in RbTiOAsO4(RTA) with the tilter method resulted in an optical rotation of ρ12= +17(3)o/mm at a wavelength of 670nm, when a (100) sample was tilted about [001]. A tilt about [010] showed no rotation, as expected from the directional dependence of optical rotation calculated from the tensor in point group mm2. The absolute Miller-indices of the sam-les were found using X-ray anomalous scattering. The calculations with a dipole-dipole model show that the As5+-ions in RTA correlate with the main structural contribution of the optical rotation. However, there seems to be an even larger intrinsic contribution due to the Ti4+– ions as a result of the distorted octahedral co-ordination with oxygen.

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AbstractThe ferroelectric/ferroelastic phase transition of K2ZnCl4at 145 K has been investigated employing the tilter method (Kaminsky and Glazer (1996) Ferroelectrics183, 133) which was adapted to low-temperature experiments. We were able to observe the anisotropy of optical rotation in K2ZnCl4which shows a distinct discontinuity at the transition temperature. A precursor-optical rotation in the ferroelectric phase is discussed in connection with a cluster ordering scheme suggested in an earlier X-ray study. The rotation of the optical indicatrix which accompanies the transition from the orthorhombic to the monoclinic system shows a Landau-type temperature dependence. Model calculations based on the dipole-dipole interaction between the atoms of the structures at different temperatures are in qualitative agreement with the experimental results.

1-Butene and 1-pentene were polymerized with three different metallocenes:  dimethylsilylbis(2-methyl-4,5-benzoindenyl)zirconium dichloride [Me2Si(2-Me-4,5-BzoInd)2ZrCl2] (1), dimethylsilylbis(2-methyl-4-phenylindenyl)zirconium dichloride [Me2Si(2-Me-4-PhInd)2ZrCl2] (2), and dimethylsilylbis(indenyl)zirconium dichloride [Me2Si(Ind)2ZrCl2] (3). The polymerizations were conducted with the rac-isomers of the metallocenes and mixtures of the rac- and meso-systems for 1 and 2 and with the meso-form of catalyst 3 combined with MAO. It was shown that the activities in the polymerization of the α-olefins of the meso-isomers of 1 and 2 were much higher than those of the rac-metallocenes, while a vice versa behavior is observed for catalyst 3. Additionally, reaction profiles of 1 and 2 were recorded which underline that the stability of their meso-compounds is much higher than that of the rac-systems for the polymerization of the investigated monomers.

The effects of fluid catalytic cracking (FCC) catalysts as fluidized bed material on the pyrolysis of polystyrene and polyethylene were investigated at temperatures between 370 and 515°C in a scale of ∼1 kgh−1. The results were compared qualitatively with pyrolysis-GC-MS-experiments (200 μg). The catalytic influence on the product distribution is easily seen by the comparison to non-catalytic experiments with simple quartz sand. In the catalytic polystyrene pyrolysis, the product distribution is changed from the usual main product styrene (61 wt.%) to basic chemicals (18–26 wt.% ethylbenzene, 9–22 wt.% benzene, 1–7 wt.% styrene, 3–5 % toluene) and soot (15–23 wt.%). Surprisingly, it was shown that in the catalytic pyrolysis of polyethylene even at low temperatures (450–515°C) gases (48–52 wt.%) and low boiling aliphatic oils (38–39 wt.%) were received instead of waxes (∼90 wt.%) in non-catalytic experiments. A further success of the catalytic pyrolysis is a dramatic reduction of the process temperature. Pyrolysis-GC-MS-experiments confirmed these results qualitatively.

Metallocene catalysts in dissolved form are in most cases unsuitable for the production of polyethylene or polypropylene on an industrial scale. In order to use them in existing technical processes, metallocenes have to be supported. Cs-symmetric zirconocenes show a high activity and no leaching additional triisobutyl aluminum is used as scavenger and MAO-covered silica for heterogenization. The aluminum : zirconium ratio can be reduced to values of 500:1 to get optimal activities. The syndiotacticity of the obtained polypropylene is lower compared with polymers of the homogeneous catalyst and decreases strongly with a thinner propene concentration.

Polymerizations of styrene were carried out with half-sandwich complexes supported on silica, CpTiX3/MAO/SiO2 (X = Cl, F). The optimum values for the polymerization time, the amount of cocatalyst and the Alsupport/Ti ratio were found for the trichlorinated system. The highest activity obtained was 3,100 g sPS/(mol Ti × h × mol/L styrene). The trihalogenated complexes were compared to one another with respect to their polymerization rate. CpTiCl3/MAO/SiO2 and CpTiF3/MAO/SiO2 behave in a similar manner, suggesting that the active species of both half-sandwich complexes on the support are the same. Furthermore, aging experiments were carried out with CpTiCl3/MAO/SiO2 and, surprisingly, deactivation was observed, as opposed to supported zirconocenes which gain stability against deactivation reactions when anchored to a carrier. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2959–2968, 1999

New functional copolymers consisting of ethene and 4-vinylcyclohexene (4-VCH) were synthesized by a stereorigid metallocene/methylalumoxane catalyst. The content of 4-VCH depends on the polymerization temperature, thus influencing the polymeric properties. Investigations of the microstructure were made using 13C NMR spectroscopy, thus revealing that 4-VCH is inserted regioselectively into the growing polymer chain. Hydroboration of selected copolymers followed by an oxidative workup yielded polyacohols which display different polymeric properties than the precursor

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AbstractIn the last few years, new techniques have been devised to measure optical rotation in cases where the linear birefringence dominates and this has opened up new fields of research into the phenomenon of optical rotation. In this paper, the phenomenon of optical rotation will be discussed with respect to our knowledge of crystal structure and a new measurement technique based on tilting of the crystal will be described.

Fluorinated half-sandwich complexes of titanium, such as CpTiF3, show an increase in activity of up to a factor of 50 compared to chlorinated compounds. In a temperature range of 10−70 °C the excess of methylaluminoxane (MAO) can be reduced to an Al:Ti ratio of 300. The highest melting point of 277 °C can be obtained using pentamethylcyclopentadienyltitanium trifluoride Cp*TiF3. This fluorinated complex affords polymers with a significantly higher molecular weight than with the chlorinated compound. Alkyl substitution of the cyclopentadienyl ligand can increase the activity.

The tensor of the Faraday effect and its temperature derivatives were determined from the temperature dependence of Faraday rotation and indices of refraction of orthorhombic Li2Ge7O15 between 120K and 340K, wave length 633nm. A strong anomaly of the Verdet constant V33 and of the index n3 was observed passing through the transition at 284K. The ratio of the slopes of the Verdet constant V33 above and below the transition is about -2. This value corresponds to a second-order ferroelectric phase transition.