SEARCH · PubMed Health

Results for “Pyrolysis”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 379 records · Page 21Linked to original sources

PubMed2006

Separation of phenols and furfural by pervaporation and reverse osmosis membranes from biomass--superheated steam pyrolysis-derived aqueous solution.

The separation of valuable chemicals from raw products, where a great number of chemicals coexist, is the key technology in biomass refinery. In this study, the applicability of membrane separation of valuable chemicals from our currently developed portable superheated steam (SHS) biomass pyrolysis process was demonstrated. Phenols (phenol, p-cresol, guaiacol, methyl guaiacol, and ethyl guaiacol), furfural, and acetone were successfully separated by pervaporation using the silicone rubber membrane from model solutions and an actual SHS derived aqueous solution. The solution was also concentrated effectively by reverse osmosis separation using a polyamide membrane. When a high concentration of SHS solution was fed to the pervaporation process, a phase-separated permeate was obtained, which indicated that the reverse osmosis concentration combined with pervaporation separation is useful for the superheated steam process.

Acetone↗

PubMed2006

Pyrolysis of triglyceride materials for the production of renewable fuels and chemicals.

Conversion of vegetable oils and animal fats composed predominantly of triglycerides using pyrolysis type reactions represents a promising option for the production of renewable fuels and chemicals. The purpose of this article was to collect and review literature on the thermo-chemical conversion of triglyceride based materials. The literature was divided and discussed as (1) direct thermal cracking and (2) combination of thermal and catalytic cracking. Typically, four main catalyst types are used including transition metal catalysts, molecular sieve type catalysts, activated alumina, and sodium carbonate. Reaction products are heavily dependant on the catalyst type and reaction conditions and can range from diesel like fractions to gasoline like fractions. Research in this area is not as advanced as bio-oil and bio-diesel research and there is opportunity for further study in the areas of reaction optimization, detailed characterization of products and properties, and scale-up.

Bioelectric Energy Sources↗

PubMed2004

Characterisation of beeswax in works of art by gas chromatography-mass spectrometry and pyrolysis-gas chromatography-mass spectrometry procedures.

Pyrolysis (Py) with in situ derivatisation with hexamethyldisilazane-gas chroma-break tography-mass spectrometry (GC-MS) and a gas chromatography-mass spectrometry procedure based on microwave-assisted saponification were used to identify the organic components in small sized beeswax samples. With the latter procedure quantitative recoveries can be made and hydrocarbons, alcohols and omega-1-diols in the neutral fraction, and fatty acids and omega-1-hydroxy acids in the acidic fraction can be efficiently separated and detected. Both procedures were used to characterise a wax anatomic sculpture "The Plague" (1691-1694) by Gaetano Zumbo, resulting in the identification of beeswax and a Pinaceae resin. The GC-MS analysis brought to light some essential differences in beeswax composition between the raw material and the old modelled wax thus giving some clear indications about the recipe used by the sculptor.

Alcohols↗

PubMed2004

Gel permeation chromatography followed by pyrolysis-gas chromatography-mass spectrometry via a solvent-evaporative interface.

The measurement of chemical composition as a function of molecular weight has always been a challenge for analytical chemists. In this paper, we present a unique way to combine gel permeation chromatography (GPC) with pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS) for this purpose. A commercially available solvent-evaporative interface, originally designed for GPC-IR measurements, was used to deposit the eluent of GPC onto aluminum foil. Small strips of aluminum foil were cut and subjected to Py-GC-MS analysis. Compared with the GPC-IR measurements, the proposed technique offers the advantage of being able to distinguish between structurally similar monomers in a complex copolymer. As an example, a copolymer composed of four monomers was analyzed. The results clearly demonstrate that this technique can be applied to complex polymeric systems to yield information regarding chemical heterogeneity versus molecular weight.

Chromatography, Gel↗

PubMed2005

Determination of optimum conditions for the analysis of volatile components in pine needles by double-shot pyrolysis-gas chromatography-mass spectrometry.

The optimum conditions for the analysis of the volatile organic components of pine needles from Pinus densiflora using double-shot pyrolysis-gas chromatography-mass spectrometry (DSP-GC-MS) were investigated with respect to thermal desorption temperature and duration of heating. A total of 41 compounds were identified using thermal desorption temperatures of 150 degrees C, 200 degrees C, 250 degrees C and 300 degrees C. Thermal decomposition products, which include acetol, acetic acid, furfurals and phenols, were observed only at thermal desorption temperatures exceeding 250 degrees C: they were not observed in the extract from a simultaneous distillation extraction (SDE) method. Heating times of 1 s, 6 s, 30 s, 150 s and 300 s were investigated at the thermal desorption temperature of 200 degrees C, whence it was found that thermal decomposition products were produced only at heating times over 30 s. The optimum pyrolyzer conditions for the analysis of pine needles using DSP-GC-MS is 200 degrees C for 6 s. Under these conditions, this method gives comparable results to the SDE method.

Gas Chromatography-Mass Spectrometry↗

PubMed2005

Study of Burseraceae resins used in binding media and varnishes from artworks by gas chromatography-mass spectrometry and pyrolysis-gas chromatography-mass spectrometry.

In the present work, a study attempting to characterize the Manila elemi and Mexican copal resins from the Burseraceae family, which are used as components of varnishes and binding media of artworks, has been carried out. A new GC-MS method involving the use of methyl chloroformate as derivatisation reagent has been proposed. A second method which uses pyrolysis-GC-MS and hexamethyldisilazane as derivatization reagent has also been applied. Characterization of the main components of the mono-, sesqui- and triterpenoid fractions occurring in the raw materials has been achieved. Both alpha- and beta-amyrin have been established as the major triterpenoid compounds occurring in these resins together with hop-22(29)-en-3beta-ol, found only in the Mexican copal. Artificially aged samples of Manila elemi and Mexican copal have also been analysed in order to study the stability of the triterpenoid components of the resins and their possible use as marker molecules. The results obtained indicate that these molecules, in particular, alpha- and beta-amyrin undergo oxidation processes during both artificial and natural ageing. Nevertheless, hop-22(29)-en-3beta-ol could be selected as marker compound for Mexican copal. The proposed methods of analysis have been applied to real paint samples extracted from paintings in which Mexican copal was present as the main component of an "oleoresin" binding medium to assess their ability for identifying this product when used in artworks. Satisfactory identification of this resin is obtained by means of GC-MS whereas Py-GC-MS provides, in general, weaker signals for the components of the resin. Additionally, the influence of the pigments present in real samples on the resin ageing process has been considered.

Burseraceae↗

PubMed2006

Determining the composition and microstructure of ethylene-propylene copolymers by pyrolysis-gas chromatography.

The average composition and detailed microstructure of copolymers of ethylene and propylene have been studied by pyrolysis-gas chromatography (Py-GC), using a statistical modeling approach to analyze the data. The trimer distribution obtained from Py-GC is used to infer monomer arrangement information, which is quantified in terms of a number-average sequence length for each monomer. These values are used to define the microstructure and to calculate the average composition. Compared with other available techniques, Py-GC provides a simple, quick and reliable approach to study the microstructure and composition of polyolefin copolymers. Details of this Py-GC method are discussed, including an examination of its advantages and disadvantages, and a summary of the qualitative and quantitative analysis aspects of this approach is presented. The combination of a statistical modeling approach with Py-GC to study copolymer composition and microstructure allows one to investigate the complex problem of monomer arrangement in copolymers using a widely available analytical technique. We expect that with further advances in separation technology, especially two-dimensional gas chromatography (GC x GC), research of this type will be become increasingly accurate and reproducible in the near future.

Alkenes↗

PubMed2005

Records of atmospheric delivery of pyrolysis-derived pollutants in recent mountain lake sediments of the Julian Alps (NW Slovenia).

The historical record of the input of pyrolysis-derived pollutants via the atmosphere, i.e. black carbon (BC), polycyclic aromatic hydrocarbons (PAH) and spheroidal carbonaceous particles (SCP) was measured in the sediments of three remote alpine lakes situated in the Julian Alps, northwest Slovenia. Parallel sedimentary trends for BC, PAH and SCP were observed across the Julian Alps and relationships among these contaminants are discussed. Inputs of these pyrolytic-contaminants to sediments of remote lakes started to rise at the end of the 19th century, while their peak inputs were observed in the mid-20th century, amounting up to 6.0 gm(-2) yr(-1) for BC, 5200 x 10(4) m(-2) yr(-1) for SCP and 2900 microg m(-2) yr(-1) for PAH. In the last two to three decades, inputs decreased substantially, by a factor of up to 3 for BC, 7 for SCP and at least 3 for PAH.

Air Pollutants↗

PubMed2004

Temperature-programmed pyrolysis hyphenated with metastable atom bombardment ionization mass spectrometry (TPPy/MAB-MS) for the identification of additives in polymers.

Thermoanalytical techniques are currently used for the analysis of additives contained in polymers that cannot be easily dissolved, extracted, or hydrolyzed. With these techniques, the polymers are heated to liberate the additives trapped in the polymer matrix. If the polymer is heated slowly, up to its thermal degradation, the technique is called temperature-programmed pyrolysis (TPPy). For TPPy experiments, mass spectrometry is generally used as the detection method. The ionization sources commonly used in mass spectrometry, such as CI and EI, can cause fragmentation during the ionization process. Fragmentation decreases the sensitivity of the molecular ions and increases the risks of interferences with the compounds coming from the matrix. An energy-tunable ionization technique, called metastable atom bombardment (MAB), is proposed for TPPy/MS experiments. With this ionization source, the energy of ionization depends on the metastable gas used. With low-energy metastable gases such as Xe or N(2), fragmentation is reduced compared to CI, whereas with medium-energy metastable gases such as Ar or Kr, the fragmentation is similar to that observed with CI. TPPy/MAB-MS was performed on an unknown polyurethane-based car paint. The detection of molecular ions and characteristic fragments with MAB(N(2)) led to the identification of two light stabilizers: Bis(1,2,2,6,6-pentamethyl-4-piperidinyl)sebacate (BPPS) and 2-(2H-benzotriazol-2-yl)-4,6- di-tert-pentylphenol (PTPP). Using MAB(Ar) to simulate CI, the molecular ion and one of the two characteristic fragments of BPPS were not detected, thus confirming the advantage of using MAB(N(2)) ionization for TPPy/MS experiments.

Journal Article↗

PubMed2004

Designing of nanostructured hollow TiO2 spheres obtained by ultrasonic spray pyrolysis.

Theoretical model describing the mechanism of droplet formation and structure of hollow TiO2 spheres prepared by the process of ultrasonic spray pyrolysis, using colloidal solution consisting of the 2.5-nm TiO2 nanoparticles as a precursor, is developed. The proposed model quantitatively defines each line in the size distribution spectrum. The mechanism of droplet formation and/or particle genesis is fully determined by harmonization between the physical fields inherent to the system as the consequence of its physical characteristics: external, e.g., ultrasound, and internal. Agreement between theoretically obtained basic structural parameters (size distribution and geometry) and experimentally determined values was found.

Journal Article↗

PubMed2005

Carbon-mineral adsorbents prepared by pyrolysis of waste materials in the presence of tetrachloromethane.

Natural bentonite spent in the process of plant oil bleaching was used as an initial material for preparation of carbon-mineral adsorbents. The spent bleaching earth was treated using four procedures: T (thermal treatment); H (hydrothermal treatment); C (thermal treatment with addition of CCl4 vapor); M (modification of porous structure). Raw bentonite, RB (raw bleaching earth), and carbon materials prepared using plant oil were compared. The physicochemical characteristics of the adsorbents were determined using different methods: nitrogen adsorption/desorption, XRD, TEM, and MS-TPD. Carbon-mineral adsorbents contain from 5.23 to 19.92% C (w/w) and carbon adsorbents include from 84.2 to 91.18% C (w/w). Parallel processes of organic substance carbonization, porous structure modification, sublimation or evaporation of metal chlorides, and removal of hydrogen chloride take place during pyrolysis of waste mineral materials in the CCl4 atmosphere.

Journal Article↗

PubMed2005

Effects of temperature and soil components on emissions from pyrolysis of pyrene-contaminated soil.

Effects of temperature and soil on yields and identities of light gases (H2, CH4, C2H2, C2H4, C2H6, CO, and CO2) and polycyclic aromatic hydrocarbons (PAH) from thermal treatment of a pyrene-contaminated (5 wt%) soil in the absence of oxygen were determined for a U.S. EPA synthetic soil matrix prepared to proxy U.S. Superfund soils. Shallow piles (140-170 mg) of contaminated soil particles and as controls, neat (non-contaminated) soil (140-160 mg), neat pyrene (10-15 mg), neat sand (230 mg), and pyrene-contaminated sand (160 mg), were heated in a ceramic boat inside a 1.65 cm i.d. pyrex tube at temperatures from 500 to 1100 degrees C under an axial flow of helium. Volatile products spent 0.2-0.4s at temperature before cooling. Light gases, PAH and a dichloromethane extract of the residue in the ceramic boat, were analyzed by gas chromatography or high pressure liquid chromatography (HPLC). Over 99% pyrene removal was observed when heating for a few tens of seconds in all investigated cases, i.e., at 500, 650, 750, 1000, and 1100 degrees C for soil, and 750 and 1000 degrees C for sand. However, each of these experiments gave significant yields (0.2-16 wt% of the initial pyrene) of other PAH, e.g., cyclopenta[cd]pyrene (CPP), which mutates bacterial cells and human cells in vitro. Heating pyrene-polluted soil gave pyrene conversions and yields of acetylene, CPP, and other PAH exceeding those predicted from similar, but separate heating of neat soil and neat pyrene. Up to 750 degrees C, recovered pyrene, other PAH, and light gases accounted for all or most of the initial pyrene whereas at 1000 and 1100 degrees C conversion to soot was significant. A kinetic analysis disentangled effects of soil-pyrene interactions and vapor phase pyrolysis of pyrene. Increase of residence time was found to be the main reason for the enhanced conversion of pyrene in the case of the presence of a solid soil or sand matrix. Light gas species released due to the thermal treatment, such as acetylene and methane, lead the formation of other, pyrene-derived PAH, e.g., methylpyrenes, cyclopenta[cd]pyrene, and benzo[a]pyrene. Implications of these findings for the chemistry of soil thermal decontamination and for diagnosing potential defects in soil thermal cleaning, e.g., incomplete elimination of targeted pollutants and formation of adverse by-products, are discussed.

Environmental Monitoring↗

PubMed2006

Pyrolysis mechanism of carbon matrix precursor cyclohexane--the formation of condensed-ring aromatics and the growing process of molecules.

Based on the experiments, the UAM1 method was adopted to investigate benzene condensation of an important intermediate and the molecule growing mechanism during the cyclohexane pyrolysis process. The conclusions were drawn as follows: (1) from the viewpoint of thermodynamics, the condensation of benzene and C4H5* is a spontaneous reaction and the rising temperature will increase the spontaneous tendency of the reaction. (2) From the viewpoint of kinetic, the condensation of benzene and C4H5* is a two-step reaction. The rate-determining step is step 2 of hydrogen removal from intermediate C10H10 (I1) with the activation energy of 350.61 kJ/mol below 1473 K while the rate-determining step is step 1 that free radical C4H5* attacks benzene to form intermediate C10H10 (I1) with the activation energy DeltaE(0)(not equal to theta)=31.74 kJ/mol above 1473 K. (3) The space structure, electronic structure and thermodynamics parameters of molecular reaction of dense-ring aromatizing compounds can be used to replace the resonance energy and free valence to judge the activation of thermodynamic reaction of compounds. And (4) the analysis of the space structure, electronic structure and thermodynamic parameters show that the growing process of molecules with benzene used as initial reactants becomes more easier as the multi-ring aromatizing molecular system increases.

Benzene↗

PubMed2005

V79-hCYP2E1-hSULT1A1, a cell line for the sensitive detection of genotoxic effects induced by carbohydrate pyrolysis products and other food-borne chemicals.

We recently constructed a Chinese hamster V79-derived cell line that stably expresses human cytochrome P450 (CYP) 2E1 and human sulphotransferase (SULT) 1A1. These enzymes are involved in the bioactivation of numerous promutagens/procarcinogens, but are not taken into account in standard in vitro mutagenicity assays. Various carbohydrate pyrolysis products and other food contaminants that induce tumours or preneoplastic lesions in laboratory animals are inactive or only weakly active in standard in vitro genotoxicity assays. This is the case for acrylamide, furan, 5-hydroxymethylfurfural, nitrofen and N-nitrosodimethylamine. These compounds were investigated for induction of sister chromatid exchange (SCE) in V79-hCYP2E1-hSULT1A1 cells. All test compounds showed positive results over a wide concentration range, starting at 0.01 microM for N-nitrosodimethylamine, 3 microM for furan, 12.5 microM for nitrofen, 20 microM for 5-hydroxymethylfurfural, and 200 microM for acrylamide. The concentration-response curve of furan was unusual, as this compound induced a statistically significant, but rather constant and weak increase in SCE over an extremely wide concentration range (3-16,000 microM). Furan was slightly less active, whereas the remaining compounds were much less active in the parental V79 cell line than in V79-hCYP2E1-hSULT1A1 cells. Compared to many other genotoxic effects, the study of SCE only requires small numbers of cells (and incubation volumes) and usually is detected even at low concentrations of the genotoxicant. Therefore, induction of SCE in V79-hCYP2E1-hSULT1A1 cells may be useful in the genotoxicity testing of preparations of heated food and in their bioassay-directed fractionation.

Animals↗

PubMed2004

Pyrolysis of virgin and waste polypropylene and its mixtures with waste polyethylene and polystyrene.

A comparison of waste and virgin polypropylene (PP) plastics under slow pyrolysis conditions is presented. Moreover, mixtures of waste PP with wastes of polyethylene (PE) and polystyrene (PS) were pyrolyzed under the same operating conditions. Not only the impact of waste on degradation products but also impacts of the variations in the mixing ratio were investigated. The thermogravimetric weight loss curves and their derivatives of virgin and waste PP showed differences due to the impurities which are dirt and food residues. The liquid yield distribution concerning the aliphatic, mono-aromatic and poly-aromatic compounds varies as the ratio of PP waste increases in the waste plastic mixtures. In addition to this, the alkene/alkane ratio of gas products shows variations depending on the mixing ratio of wastes.

Environmental Pollution↗

PubMed2006

Pyrolysis characteristics and kinetics of chicken litter.

Chicken litter generally consists of a mixture of bedding, manure, feathers and spilled food. Flock of birds litter (flock) is a litter consisting of hardwood shavings, feed, feathers and manure; and broiler litter (broiler) is a cake of chicken litter. A kinetic investigation of the pyrolysis of chicken litter (flock and broiler) was carried out using thermogravimetric analysis (TGA) at heating rates of 5 degrees C/min, 10 degrees C/min and 20 degrees C/min. Most of the materials decomposed between 270 degrees C and 590 degrees C at each heating rate. The region of decomposition of flock and broiler was slightly lower than that of the wood chips. Wood chips (bedding material) decomposed in two stages, while flock and broiler decomposed in three stages. Apparent activation energies increased from 99 to 484 kJ/mol for the three samples when the pyrolytic conversion increased from 5% to 95%.

Agriculture↗

PubMed2006

Pyrolysis of mixtures of sewage sludge and manure: a comparison of the results obtained in the laboratory (semi-pilot) and in a pilot plant.

A pilot-scale pyrolysis process was carried out for the treatment of a mixture of two types of waste, sewage sludge and cattle manure, comparing the results with others obtained under laboratory conditions (semi-pilot scale). The aim of this study was to obtain the energetic valorization of the products. Owing to the specific characteristics of the plant, two products were obtained from the process: gas and carbonized solid. As no liquid fraction was obtained, the gas fraction is a greater percentage made up of both condensable and non-condensable compounds, which were obtained separately at the laboratory scale. The pilot plant was designed so that the gases produced by thermolysis were burnt continuously in a combustion chamber, while the carbonized fraction was fed in batches for co-combustion. To determine composition and combustion ability, the gas and solid products from the pilot process were characterized by chromatographic analysis of the gaseous fraction and chemical analysis and programmed-temperature combustion of the carbonized solid. The composition of the combustion gases, rich in light hydrocarbons, and the carbon present in the carbonized fraction enable the energetic valorization of these products. The combustion gases were subjected to a cleaning process and their composition analysed twice: before and after the gas cleaning treatment. The study led to a positive assessment of the possible use of the process products as fuel, provided that the combustion gases are treated. As most of the sulphur and chlorine from the original waste are mainly concentrated in the solid fraction, the use of char as a fuel will depend on the effectiveness of clean-up techniques for combustion gases. During gas cleansing, neutralizing with sodium bicarbonate proved effective, especially for the acidic compounds HCl, HF and SO(2).

Animals↗

PubMedDate not supplied

Capillary column pyrolysis-gas chromatography of hair: a short study in personal identification.

Human head hairs from 18 individuals were analysed by capillary column pyrolysis-gas chromatography (PyGC). The pyrograms showed several components, three of which were found to differ significantly among individuals. These major components were identified as benzene, toluene and styrene by gas chromatography-mass spectrometry. As the result of capillary column PyGC of 18 amino acids, it was found that differences among the individuals were due to the different amounts of particular amino acids in the hair. The quantities of the components were, further, found not to change in 18 months.

Adolescent↗