Characterization of naphtha and carbon black obtained by vacuum pyrolysis of polyisoprene rubber

Pure polyisoprene and a commercial rubber sample containing 52% polyisoprene and 31% carbon black were pyrolysed at 500°C and at a total pressure varying between 0.8 and 28.0 kPa. The yields of gas, oil and pyrolytic carbon black (CB_P) changed little with the pyrolysis pressure. However, the oil composition and the CB_P characteristics depended considerably on the pyrolysis pressure. For example, the amount of dl-limonene, a valuable compound in the naphtha fraction, decreased with increasing pyrolysis pressure. The CB_P and the commercial carbon black initially present in the rubber sample were analysed by ESCA, SIMS and SEM. With decreasing pyrolysis pressure the surface chemistry of the CB_P became similar to that of the commercial carbon black initially present in the rubber. Therefore, rubber pyrolysis should be performed at low pressures in order to obtain products with a higher commercial value.     

Mineral matter effects on the rapid pyrolysis and hydropyrolysis of a bituminous coal. 1. Effects on yields of char,tar and light gaseous volatiles

The effects of minerals on product compositions from rapid pyrolysis of a Pittsburgh Seam bituminous coal were investigated. Whole, demineralized, and mineral treated samples of pulverized coal were heated in 100 KPa helium or 6.9 MPa hydrogen at 1000 K s^?1 to temperatures of up to 1300 K. Yields of char, tar and individual gaseous products were determined as a function of time-temperature conditions. Clays, iron-sulphur minerals, and quartz had few effects on pyrolysis in helium. Calcium minerals decreased yields of hydrocarbon products and increased yields of CO in helium pyrolysis. Calcite and clays decreased yields of CH₄ from hydropyrolysis, whereas iron-sulphur minerals had little effect on pyrolysis at 6.9 MPa H₂. Whole coal results were similar to demineralized coal results under all conditions.     

Pyrolysis of polyolefin elastomers

Commercial samples of two ethylene—propylene terpolymers (EPDM), two isobutene— isoprene copolymers (IIR), one polyisobutene (PIB) and one chlorosulphonated polyethylene (CSPE) were pyrolysed at temperatures between 770 and 1370 K in a quartz micro-furnace. Volatile products were analysed by gas chromatography using wide-boiling-range and high-boiling-point columns with flame ionisation detectors and/or online quadrupole mass spectrometry using helium as carrier. Low molecular weight gases were separated on a crosslinked polystyrene bead column and detected with a katharo-meter using argon as carrier. Mechanisms are put forward to account for the temperature-dependence of pyrolysis-product yields as follows. In the primary pyrolysis (ca 770–870 K) EPDM products arise principally from 1 : 5 : 9(: 13 : 17) intramolecular hydrogen transfer accompanied by some unzipping. There is also evidence for a small amount of transfer to the third carbon atom and of some β-scission. IIR and PIB yielded isobutene presumably by stepwise cyclic unimolecular elimination. However, a number of other products including telomers, methane, iso-butane and neopentane are explained by telomerisation of isobutene and intramolecular transfer reactions following random scission; at 870 K, there is already evidence for some aromatisation. CSPE pyrolysis is complicated by preliminary loss of SO₂Cl groups and dehydrochlorination to form a polyene. Concomitant crosslinking may involve inter-molecular elimination of HCl and/or a Diels-Alder type reaction between two polymer molecules which have already undergone dehydrochlorination. Subsequent thermal degradation of the main chain proceeds principally by 1 : 5 hydrogen transfer. At intermediate temperatures (above 900 K) secondary pyrolysis occurs in which higher alk-l-enes formed by primary pyrolysis break down to lower molecular weight products probably by a modified Rice mechanism and associated intramolecular cyclic dissociation. Similar mechanisms are proposed to explain the secondary products from IIR and CSPE. At higher temperatures (above 1000 K) further fragmentation, cyclisation and aromatisation. occur. For all the polymers, hydrogen yields increase sharply and yields of C₃/C₄ products diminish; C₂ yields show maxima at temperatures about 1100 K. Below 1200 K, benzene is formed in largest yield. Toluene yields fall at temperatures above 1100 K, but naphthalene is formed in increasing yields up to a maximum at about 1220 K. At these higher temperatures, the product spectrum is simplified by the disappearance of molecules of intermediate size leaving only small fragmentation products and rather large polynuclear aromatics (anthracene, etc.). Two main routes are suggested for the formation of cyclic products from EPDM and IIR-

• a cyclisation of (particularly) methyl-substituted n-alkenes/alkanes of sufficiently high carbon number; and
• b the reaction of intermediate molecules such as olefin + diene by a Diels-Alder reaction.

At the highest temperatures investigated, high hydrogen yields are accompanied by a substantial drop in total yield of volatilisable products and this is attributed to further condensation of aromatics in coking reactions.     

New method for evaluation of kinetic parameters and mechanism of degradation from pyrolysis–GC studies: Thermal degradation of polydimethylsiloxanes

Thermal degradation of polydimethylsiloxane (PDMS) polymers having hydroxyl (PS) and vinyl (PS‐V) terminals was studied by pyrolysis‐gas chromatography (PGC) in the temperature range from 550 to 950°C. The degradation products were primarily cyclic oligomers ranging from trimer (D₃) to cyclomer D₁₁ and minor amounts of linear products and methane. The product composition varied significantly with pyrolysis temperature and extent of degradation. A new method was developed to derive a mass loss‐temperature curve (pyrothermogram, PTG) and to determine the kinetic parameters of decomposition (k, n, and E_a) from sequential pyrolysis studies. It was shown that isothermal rate constants can be derived from repeated pyrolysis data. Good agreement between the rate constants derived from the two methods validates the methodology adopted. This was further confirmed from thermogravimetric studies. The E_a values for the decomposition of PS and PS‐V derived from sequential pyrolysis were 40 ± 2 and 46 ± 2 kcal mol⁻¹, respectively. Various mechanisms for the degradation of PDMS were reviewed and discussed in relation to the PGC results. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 441–450, 1999     

Grafting of methyl methacrylate on EPR and EPDR: Impact properties of polyvinyl chloride grafted polymer blends

EPDM rubber can be brought into water suspension after swelling in n-heptane containing proper emulsifiers and in shear stress; particles reach dimensions as low as 150 Å. Methyl methacrylate in emulsion can be grafted easily with Bz₂O₂ on the rubber. Grafting yields depend particularly on the monomer/rubber ratio. The grafted polymer can be recovered by precipitating the emulsion with acetone, which eliminates the homopolymer. The grafting mechanism is discussed in terms of different initiators (AIBN and Bz₂O₂) and unsaturated (EPDM) and saturated rubber (EPR); AIBN and PMMA radicals were inactive in abstracting hydrogen atoms from rubber chains. Mechanical properties of the blends with PVC of the raw graft product are discussed on the basis of the grafted polymer composition and synthesis conditions. Very high impact strength can be reached at 15% rubber content in the blend for a grafted polymer obtained from a monomer/rubber ratio equal to 0.75.     

Thermal and scanning electron microscopy/energy‐dispersive spectroscopy analysis of styrene–butadiene rubber–butadiene rubber/silicon dioxide and styrene–butadiene rubber–butadiene rubber/carbon black–silicon dioxide composites

Silica as a reinforcement filler for automotive tires is used to reduce the friction between precured treads and roads. This results in lower fuel consumption and reduced emissions of pollutant gases. In this work, the existing physical interactions between the filler and elastomer were analyzed through the extraction of the sol phase of styrene–butadiene rubber (SBR)–butadiene rubber (BR)/SiO₂ composites. The extraction of the sol phase from samples filled with carbon black was also studied. The activation energy (E_a) was calculated from differential thermogravimetry curves obtained during pyrolysis analysis. For the SBR–BR blend, E_a was 315 kJ/mol. The values obtained for the composites containing 20 and 30 parts of silica per hundred parts of rubber were 231 and 197 kJ/mol, respectively. These results indicated an increasing filler–filler interaction, instead of filler–polymer interactions, with respect to the more charged composite. A microscopic analysis with energy‐dispersive spectroscopy showed silica agglomerates and matched the decreasing E_a values for the SBR–BR/30SiO₂ composite well. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 2273–2279, 2005     

The application of thermal processes to valorise waste tyre

Scrap tyres are a growing environmental problem because they are not biodegradable and their components cannot readily be recovered. In this investigation, the thermochemical recycling of rubber from old tyres by pyrolysis and the value of the products obtained have been studied. First, thermobalance experiments were carried out, studying the influence of the following variables: heating rate, flow rate, particle size and temperature. These thermobalance results were extended by performing experiments in a fixed bed reactor, studying the effect of the main process variables on yields of derived products: oils, gases and solid residue. The oils have been characterized using a combination of analytical techniques (TLC–FID, GC–MS and simulated distillation). No relationship between functional group composition of the oils determined by TLC–FID and process variables was found. The carbonaceous material obtained was characterized by N₂ and CO₂ adsorption. The possible uses of this char have been analyzed taking into account and calculating the emissions that would be produced if the char were burnt.     

CW CO2-Laser SF6-Photosensitized Pyrolysis of Tetralin

CW CO₂ laser photosensitized (SF₆) pyrolysis of tetralin proceeds mainly via dehydrogenation channel affording 1,2-dihydronaphthalene and naphthalene. Less important ring cleavage products are indene, styrene, ethylbenzene, toluene, and benzene, together with ethylene and methane. No occurrence of polyaromatics and high yields of ethylene compared to methane are the features differing this process from high temperature conventional pyrolysis.     

Pyrolysis products of uncoated printing and writing paper of MSW

Uncoated printing and writing paper, one of the principal waste papers in Taiwan, was pyrolyzed with a thermogravimetric analysis (TGA) reaction system. The pyrolysis experiments were carried out in nitrogen environment at a constant heating rate of 5 K min⁻¹. The gaseous products and the residues were collected at room temperature (300 K) and analyzed by gas chromatography (GC) and elemental analyzer, respectively. The major gaseous products investigated included non-hydrocarbons (H₂, CO, CO₂, and H₂O) and hydrocarbons (C_1-3, C₄, C₅, C₆, 1-ring, C_10-12, levoglucosan, C_13-15, and C_16-18). The cumulated masses and the instantaneous concentrations of gaseous products were obtained under the experimental conditions. The yields of non-hydrocarbon gases and of hydrocarbon gases were about 10.46 and 0.49% at 623 K, 33.68 and 0.89% at 700 K, 64.52 and 1.05% at 788 K, and 79.10 and 1.63% at 938 K, respectively. The estimation of the mass of tar, yielded at various pyrolysis temperatures was also made. The results of this study might be useful for the design of pyrolysis process as well as for determining the pyrolysis mechanisms of the uncoated printing and writing paper.     

Chlorination of low-molecular-weight Euphorbia lactiflua natural rubber

The chlorination of low-molecular-weight natural rubber isolated from Euphorbia lactiflua latex (LMWER) was accomplished. The reaction was performed by using Cl_2(g), and CH₂Cl₂ or CCl₄ solvents. Different temperatures, reaction times and Cl₂ to isoprene ratio were used. The products were characterized by elementary analysis, infrared spectroscopy (FT-IR), ¹H nuclear magnetic resonance (NMR), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The maximum chlorination reached was 59.9%. The properties were found to be comparable with chlorinated rubber obtained from liquid natural rubber (LNR). Received: 13 June 1997/Revised: 15 September 1997/Accepted: 23 September 1997     

Pyrolysis of benzenethiol

Flow pyrolysis of benzenethiol at 700 °C or vacuum pyrolysis of benzenethiol at 800 °C yields benzene, diphenyl sulphide and diphenyl disulphide as the major products. Dibenzothiophene, biphenyl, thianthrene and diphenyl trisulphide are minor products. Co-pyrolysis of benzene-d₆ and natural isotopic abundance benzenethiol yields deuterated and non-deuterated products, indicating that the product-forming sequence is initiated by phenyl radical formation. The phenyl radicals abstract hydrogen atoms from benzenethiol to yield benzene and phenylthio radicals. Coupling of phenylthio radicals yields diphenyl disulphide. Diphenyl sulphide and the minor products are diphenyl disulphide pyrolysis products.     

Prediction of gaseous products from biomass pyrolysis through combined kinetic and thermodynamic simulations

Due to the nonhomogeneous characteristics of biomass constituent, it has been known to be difficult to apply directly any simulation work to the pyrolysis of biomass for a precise prediction of gaseous products. In this study, two computation codes (HSC Chemistry for thermodynamic and Sandia PSR for kinetic simulations) were employed, to consider the integrated effects of thermodynamic and kinetic phenomena occurring in biomass pyrolysis on the distribution of gaseous products. The principle of simulation applied in this study was to extract substitutable gas phase compositions from HSC calculations, which were predicted thermodynamically. Then, the gas phase compositions were inputted into the Sandia PSR code to consider the potential constrains of kinetics involving in the pyrolysis and finally to get the distributions of gas products which should be closer to the realistic situation. Palm oil wastes, a local representative biomass, were studied as sample biomass. The gaseous products obtained from HSC calculations were mainly H₂, CO₂, CO, CH₄ and negligible C₂₊ hydrocarbons. After applying these products into PSR program, the final products developed into H₂, CO₂, CO, CH₄, C₂H₂, C₂H₄, C₂H₆ and C₃H₈ which are more realistic products in the modern fast pyrolysis.     

Effects of Atmospheric Composition on the Molecular Structure of Synthesized Silicon Oxycarbides

The dependence of silicon oxycarbides' chemical composition and molecular structure on their reaction conditions was tested by varying the atmosphere under which pyrolysis was performed. To obtain the silicon oxycarbides, densely cross‐linked silicone resin particles with an averaged diameter of 2 μm were pyrolyzed in various atmospheres of H₂, Ar, and CO₂, in the temperature range 700°C–1100°C. The residual mass of resin after pyrolysis was almost constant at 700°C, although their apparent colors varied distinctly. The sample obtained from the H₂ atmosphere was white, whereas that obtained from the CO₂ atmosphere was dark brown. Fourier‐transform infrared (FT‐IR) spectra of the residues suggested that the Si–O–Si network evolution was accelerated in the CO₂ atmosphere. Beyond 800°C, the chemical compositions of the compounds obtained from a H₂ atmosphere increasingly approached near‐stoichiometric SiO₂–xSiC composition with increasing the pyrolysis temperature. Compounds from a CO₂ atmosphere approached a composition of SiO₂–xC with no free SiC as the pyrolysis temperature increased. In the products from an Ar atmosphere, SiO₂–xSiC–yC compositions were typically obtained. The observed effects of the pyrolysis atmosphere on the resulting chemical compositions were analyzed in terms of thermodynamic calculations. Electron spin resonance (ESR) spectra revealed broad and intense signals from products obtained from either Ar or CO₂. Estimating from the signal intensity, the residual spin concentrations were in the range 10¹⁸–10¹⁹ g^?1. Meanwhile, the spectra from the samples obtained in H₂ showed weak and sharp signals with estimated spin concentrations ranging from 10¹⁶–10¹⁷ g^?1. This signal attenuation may have been due to the hydrogen capping of dangling bond formed during pyrolysis.     

The effects of oxygen on the yields of the thermal decomposition products of catechol under pyrolysis and fuel-rich oxidation conditions

In order to investigate the effects of oxygen on the distribution of thermal decomposition products from complex solid fuels, pyrolysis and fuel-rich oxidation experiments have been performed in an isothermal laminar-flow reactor, using the model fuel catechol (ortho-dihydroxybenzene), a phenol-type compound representative of structural entities in coal, wood, and biomass. The gas-phase catechol pyrolysis experiments are conducted at a residence time of 0.3 s, over a temperature range of 500-1000 °C, and at oxygen ratios ranging from 0 (pure pyrolysis) to 0.92 (near stoichiometric oxidation). The pyrolysis products are analyzed by nondispersive infrared analysis and by gas chromatography with flame-ionization and mass spectrometric detection. In addition to an abundance of polycyclic aromatic hydrocarbons, catechol pyrolysis and fuel-rich oxidation produce a range of C₁-C₅ light hydrocarbons as well as single-ring aromatics. Quantification of the products reveals that the major products are CO, acetylene, 1,3-butadiene, phenol, benzene, vinylacetylene, ethylene, methane, cyclopentadiene, styrene, and phenylacetylene; minor products are ethane, propyne, propadiene, propylene and toluene. Under oxidative conditions, CO₂ is also produced. At temperatures <850 °C, increases in oxygen concentration bring about increases in catechol conversion and yields of C₁-C₅ and single-ring aromatic products—in accordance with increased rates of pyrolytic reactions, due to the enhanced free-radical pool. At temperatures >850 °C, catechol conversion is complete, and increases in oxygen bring about drastic decreases in the yields of virtually all hydrocarbon products, as oxidative destruction reactions dominate. Reactions responsible for the formation of the C₁-C₅ and single-ring aromatic products from catechol, under pyrolytic and oxidative conditions, are discussed.     

Secondary coking and cracking of shale oil vapours from pyrolysis or hydropyrolysis of a Kentucky Cleveland oil shale in a two-stage reactor

It is widely recognized that secondary reactions which are mainly associated with minerals during oil shale retorting have a marked influence on the product yields and compositions. To understand these phenomena more clearly, the secondary reactions of shale oil vapours from the pyrolysis (or hydropyrolysis) of Kentucky Cleveland oil shale were examined in a two-stage, fixed-bed reactor in flowing nitrogen or hydrogen at pressures of 0.1–15 MPa. The vapours from pyrolysis (first stage) were passed through a second stage containing combusted shale, upgrading catalyst or neither. Carbon conversion to volatile products in the first stage increased from 49% during thermal pyrolysis to 81% at 15 MPa H₂ partial pressure. During thermal pyrolysis, total pressure had only a slight effect on carbon removal from the raw shale and subsequent deposition on to the porous solids in the second stage. Carbon deposition on to the combusted shale in the second stage was reduced to zero at 15 MPa H₂ partial pressure. The n-alkane distributions of the oils as determined by gas chromatography clearly demonstrated that higher hydrogen pressure, contact with combusted shale, or both contributed to lower-molecular-weight products.     

Value-added products from waste: Slow pyrolysis of used polyethylene-lined paper coffee cup waste

The objectives of this study were to examine how to recycle cup waste efficiently and effectively and to determine if cup waste can be converted into liquid, solid, and gas value-added products by slow pyrolysis. The characteristics and potential utilizations of the pyrolysis products were investigated. The study included the effects of temperature, heating rate, and different feedstocks. The yield of pyrolysis oil derived from cup waste increased from 42% at 400°C to 47% at 600°C, while the yield of char decreased from 26% at 400°C to approximately 20% at 600°C. Acetic acid and levoglucosan were identified as the main components of the pyrolysis oil. The char obtained at 500°C was physically activated at 900°C for 3 h with CO₂. The adsorption capacity of the activated char was investigated with model compounds, such as methyl orange, methylene blue, ibuprofen, and acetaminophen. The results showed that the adsorption capacity of the activated char was similar to that of commercial activated carbon produced from peat. The higher heating value of the produced gas stream calculated at 400°C was 19.59 MJ/Nm³. Also, conventional slow pyrolysis (CSP) and microwave-assisted pyrolysis (MAP) technologies were compared to determine the differences in terms of products yields, composition and characteristics of the pyrolysis oil, and their potential applications. The CSP yields higher liquid products than MAP. Also, the pyrolysis oil obtained from the CSP had significantly more levoglucosan and acetic acid compared to that of the MAP.     

An integrated process of oxidative coupling of methane and pyrolysis of naphtha in a scaled‐up unit

A heat‐effective ‘integrated’ process of C₂H₄ production, incorporating exothermic oxidative coupling of methane (OCM) carried out in the catalytic section of a flow tubular reactor, and endothermic pyrolysis of naphtha carried out in the postcatalytic section of the same reactor, studied earlier in a small silica reactor, was examined now in a scaled‐up unit with a stainless‐steel (1H18N9T) reactor (volume 400 cm³, Li/MgO catalyst bed 165 cm³). It was demonstrated that depending on the operating conditions, such an integrated process could be realized over a wide range of the relative contribution of the two component processes, leading always to an increase in the C₂H₄ yield, as compared with OCM or pyrolysis alone. A high degree of additivity of the yields of all products was observed in all cases, independently of the relative contribution of OCM and pyrolysis. Such results indicated that in the scaled‐up unit with a stainless‐steel reactor, the interactions between the component processes and products were only negligible under experimental conditions. The overall balance of CH₄, being consumed in OCM and formed in pyrolysis, was negative, equal to zero, or positive, depending on the relative contribution of the component processes. The integrated process could be based, therefore, either on CH₄ and naphtha as raw materials or exclusively on naphtha, with the recirculation of the excess of CH₄ to the OCM section. Copyright © 2004 Society of Chemical Industry     

煤快速热解固相和气相产物生成规律

利用能有效避免二次转化反应的高频炉热解装置对3种不同变质程度的煤进行了600～1200℃条件下的快速热解,考察了在煤热解最初阶段焦产率、焦-C产率、热解气产率、热解气4种主要组分H₂、CO、CH₄和CO₂的比例以及热解气热值随煤阶和热解温度的变化规律。结果表明,焦的产率和焦-C的产率均随煤阶的升高而升高,热解气的产率随煤阶的升高而降低;热解温度的提高能显著降低煤焦和焦-C的产率并提高热解气的产率。热解气组分以H₂相似文献   

Pyrolysis of tetra pack in municipal solid waste

The pyrolysis of tetra pack in nitrogen was investigated with a thermogravimetric analysis (TGA) reaction system. The pyrolysis kinetics experiments for the tetra pack and its main components (kraft paper and low‐density poly(ethene) (LDPE)) were carried out at heating rates (β) of 5.2, 12.8, 21.8 K min^?1. The results indicated that the one‐reaction model and two‐reaction model could be used to describe the pyrolysis of LDPE and kraft paper respectively. The total reaction rate of tetra pack can be expressed by the summation of the individual class of LDPE and kraft paper by multiplying the weighting factors. The pyrolysis products experiments were carried out at a constant heating rate of 5.2 K min^?1. The gaseous products were collected at room temperature (298 K) and analyzed by gas chromatography (GC). The residues were collected at some significant pyrolysis reaction temperatures and analyzed by an elemental analyzer (EA) and X‐ray powdered diffraction (XRPD). The accumulated masses and the instantaneous concentrations of gaseous products were obtained under the experimental conditions. The major gaseous products included non‐hydrocarbons (CO₂, CO, and H₂O) and hydrocarbons (C_1–5). In the XRPD analysis, the results indicated that pure aluminum foil could be obtained from the final residues. The proposed model may be supported by the pyrolysis mechanisms with product distribution. © 2001 Society of Chemical Industry     

Influence of the conditions of coke charge pyrolysis on the yield and composition of the gases formed

As a result of comparison of the yields, compositions, and dynamics of evolution of the vapor-gas products of pyrolysis under various process conditions, a considerable effect of secondary pyrolysis on their quality was found. When suppressing the influence of the secondary reactions, the hydrocarbon content in gas increases; an increase in the degree of influence of the secondary reactions leads to increased yields of CO and H₂.