Szerves aeroszol képződése felhőfolyamokban = Formation of organic aerosol in cloud processes

Kutatásaink során bizonyítottuk, hogy a felhővízben a biomassza égetés során kibocsátott vegyületekből polimerizációval fényt elnyelő humuszszerű anyag keletkezik. Vizsgáltuk ennek a folyamatnak a mechanizmusát, időállandóját és a keletkezett anyag kémiai tulajdonságait is. Ezzel párhuzamosan a biomassza égetésből származó aeroszolban megfigyelt, gömb alakú szerves részecskék keletkezési mechanizmusát is valószínűsítettük, amit összefüggésbe hoztunk a fenti kémiai reakcióval. E részecskék abszorpciós tulajdonságait kísérletileg is vizsgáltuk, és megállapítottuk, hogy a biomassza égetésből származó aeroszolban a sugárzáselnyelés számottevő hányadáért felelős lehet. Kutatásaink során részben nemzetközi együttműködésben bizonyítottuk, hogy a természetben a legnagyobb mennyiségben kibocsátott illékony szerves vegyületből, az izoprénből közvetve lehetséges felhőfolyamatokban aeroszol képződés. A folyamat légköri jelentőségét egy egyszerűsített légköri modell segítségével vizsgáltuk, és megállapítottuk, hogy globális léptékben jelentős. A beszámolási időszakban a pályázat témáját is érintő monográfiát írtam Carbonaceous Aerosol címmel, ami 2004-ben a Springer kiadónál jelent meg. A könyv külön alfejezetet szentel a felhőfolyamatok lehetséges szerepének a másodlagos szerves aeroszol képződésében, ami a tudományterület legújabb eredményeit, nem kis részben saját eredményeinket foglalja össze. | In our study it has been proved that volatile compounds released by biomass burning can polymerize into humic-like substances (HULIS) in cloud water. The mechanism and kinetics of these reactions, as well as the properties of the products have also been studied. It has been hypothesized that tar ball particles observed in biomass smoke may also be produced in such reactions. It has been found that these particles account for a significant fraction of absorption of shortwave radiation in biomass smoke. In another study, isoprene has been established as a possible precursor of secondary aerosol formation in cloud processes, and a model study has revealed that it is globally significant. My monograph titled Carbonaceous Aerosol was published in 2004 by Springer. In this book a separate sub-chapter is devoted to the role of cloud processes in secondary organic aerosol formation, partly based on the results of our recent studies in this field

Pyrolysis of wood – PVC mixtures. Formation of chloromethane from lignocellulosic materials in the presence of PVC

Thermal decomposition of polyvinylchloride (PVC) – wood and wood component mixtures were examined under slow and fast heating by pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) and thermogravimetry/mass spectrometry(TG/MS) techniques in order to clarify the chemical interaction of biomass materials and PVC during thermal decomposition. A hardwood and a softwood (beech and pine), their lignin and two types of cellulose (Avicel and Whatman) were chosen as natural polymer components. Comparing the gaseous and liquid pyrolysis products of pure samples to those of mixtures it was found that considerably lower amount of several reactive compounds have been produced when the biomass sample was mixed with PVC. On the other hand significant amount of chloromethane appeared in the pyrolysate of wood and lignin samples mixed with PVC under fast and slow pyrolysis conditions as well, but only in traces of chlorinated organic compounds were detected from cellulose mixtures. It was concluded that the methoxy groups at phenolic rings in lignin are the methyl source of chloromethane formation, and this reaction consumed most of the HCl evolved from PVC

Thermogravimetric analysis of tobacco combustion assuming DAEM devolatilization and empirical char-burnoff kinetics

Two blends of tobacco (Virginia and Burley) were studied by thermogravimetry at linear and nonlinear heating programs in gas flows containing 2, 4 and 9% oxygen. A kinetic scheme of successive devolatilization and char burn-off reactions was assumed. A distributed activation energy model was assumed for the devolatilization with a Gaussian distribution and a constant pre-exponential factor. The evaluations were also carried out using non-constant pre-exponential factors that depended on the activation energy. The char burn-off was described by first order kinetics and by an empirical model that took into account the change of the reactivity with the conversion of the sample. The dependence of the rate of combustion on the oxygen concentration was approximated by a power function. Series of 15 and 30 experiments were used for the determination of the model parameters by simultaneous least squares evaluation of the experiments. The considerations, methods and results can also be used in the field of biomass gasification and combustion

Környezetszennyező komponensek eltávolítása műanyaghulladékok pirolízistermékéből = Elimination of polluting components from pyrolysis oils of plastics wastes

A pályázat céljának megfelelően műanyaghulladékokból nyert pirolízisolajokat módosítottunk szilárd fázisú katalizátorok segítségével a nitrogén- és a halogéntartalom csökkentése érdekében. Megállapítottuk, hogy az Y és ß zeolitok többnyire megváltoztatják a polimerek hőbomlástermék vegyületeit, magát a hőbomlás reakcióját azonban kevéssé befolyásolják. Gyengén savas zeolit katalizátorágyon a pirolízistermék molekulák heteroatomot (nitrogént és oxigént) tartalmazó csoportjai leszakadnak, így a pirolizátum nitrogéntartalma a gázfázisba kerül, míg a szénhidrogén szegmensek egy- és kétgyűrűs aromás szénhidrogén vegyületekké alakulnak. A nátrium-zeolit kisebb molekulákra tördeli, és gyűrűbe zárja a hőbomlás termékeit, de nem bontja a szén-nitrogén kötéseket; így ez a katalizátor alig csökkenti a pirolízisolaj nitrogéntartalmát. A foszfortartalmú gyengén savas szervetlen égésgátlók jelentős hatással vannak a polimerek hőbomlási folyamataira és azok termékeire, azonban a pirolízisolaj nitrogéntartalmát nem befolyásolják. A nátriumionos Y és ß zeolitok általában alkalmasak a klór- és brómtartalmú pirolízisolajok halogéntartalmának mérséklésére, de halogénmentesítő aktivitásuk jelentősen eltérő a különböző típusú szerves klór- és brómvegyületek esetében. Tanulmányoztuk a deaktiválódott zeolitok regenerálhatóságát is. A katalitikus aktivitás elvesztését okozó szenes lerakódás minősége eltérőnek bizonyult a protonos és a nátriumion tartalmú zeolitoknál. | In accordance with the goals of the project pyrolysis oils of plastics waste have been converted over solid catalysts in order to decrease their nitrogen and halogen content. Our observations showed that the thermal decomposition reactions of polymers are hardly altered, but their products are mostly modified by Y and ß zeolite. The heteroatom (N and O) containing groups of the pyrolysis product molecules are cleaved over zeolites of weak acidity, thus the nitrogen content of the pyrolysate is moved to the gas phase, while the hydrocarbon parts are converted to aromatic hydrocarbons of one and two rings. Over sodium-zeolites the pyrolysis product molecules are either split at C-C bonds or cyclised. But the C-N bonds are not cleaved, so the nitrogen content of the pyrolysis oil has hardly decreased over these zeolites. The inorganic phosphor containing flame retardants of weak acidity proved to influence the thermal decomposition process of the polymers, however, the nitrogen content of the pyrolysis oil has not been changed by them. Our experiments revealed that Na-Y and Na-ß zeolite can be applied for dehalogenating pyrolysis oils of chlorine and bromine containing polymers, nevertheless their catalytic activity considerably differ for various types of organic chloro-and bromo-compounds. The regeneration of the deactivated zeolites has been also studied. The quality of the deposited coke proved to be different on the surface of protonated and sodium forms of zeolite

Tobacco pyrolysis. Kinetic evaluation of thermogravimetric – mass spectrometric experiments.

The thermal decomposition of two tobacco blends was studied by thermogravimetry - mass spectrometry (TGA-MS) at slow heating programs under well defined conditions. The kinetic evaluation was based on a distributed activation energy model (DAEM) which is a suitable tool for complex materials of plant origin. Linear and non-linear (stepwise) heating programs were employed to obtain information for reliable kinetic modeling. Series of experiments were evaluated simultaneously by the method of least squares. Efforts were made to identify and describe kinetically the similarities between two, highly different tobacco samples as well as between the various mass spectrometric intensity curves. This was achieved by evaluating large series of experimental results and assuming several kinetic parameters to be common for both samples and/or a group of mass spectrometric intensities. The methods and considerations outlined in the paper may be helpful in the studies of biomass and other organic samples by a wider variety of experimental techniques including TGA-FTIR and time resolved pyrolysis

Combustion Kinetics of Biomass Materials in the Kinetic Regime

Wheat straw, willow from an energy plantation, and municipal sewage sludge were studied by thermogravimetry at linear and nonlinear heating programs in gas flows containing 4 and 20% oxygen. A kinetic scheme of successive devolatilization and char burnoff reactions was assumed. A distributed activation energy model (DAEM) was assumed for the devolatilization with a Gaussian distribution and a constant pre-exponential factor. The burnoff of the forming char was approximated by first-order kinetics with respect to the amount of char. The dependence of the reactions upon the oxygen concentration was described by power functions. This model gave a suitable description for the wheat straw and sewage sludge. An additional partial reaction with accelerating kinetics was needed for describing the oxidative cellulose pyrolysis in the willow sample. The evaluations were carried out by the method of least squares. 9-17 model parameters were determined from ten experiments for each sample. Good fit quality and reasonable kinetic parameters were obtained. Test evaluations revealed that the first-order kinetics, with respect to the amount of char is an adequate model; the assumptions of more complex char burnoff submodels did not led to notable improvements. The replacement of the DAEM devolatilization by simpler n-order kinetics gave inadequate performance. Earlier works with simpler models and linear temperature programs showed that the successive mechanism can be well-approximated by parallel reactions. Such approximations proved to be viable in the present case, too

Study on the leaching of phthalates from polyethylene terephthalate bottles into mineral water

Carbonated and non-carbonated mineral water samples bottled in 0.5-L, 1.5-L and 2.0-L polyethylene terephthalate (PET) containers belonging to three different water brands commercialized in Hungary were studied in order to determine their phthalate content by gas chromatography - mass spectrometry. Among the six investigated phthalates, diisobutyl phthalate, di-n-butyl-phthalate, benzyl-butyl phthalate and di(2-ethyl-hexyl) phthalate (DEHP) were determined in non-carbonated samples as follows: <3.0 ng L-1 - 0.2 μg L-1, <6.6 ng L-1 - 0.8 μg L-1, <6.0 ng L-1 - 0.1 μg L-1 and <16.0 ng L-1 - 1.7 μg L-1, respectively. Any of the above-mentioned phthalate esters could not be detected in carbonated mineral water samples. DEHP was the most abundant phthalate in the investigated samples. It could be detected after 44 days of storage at 22 ºC and its leaching was the most pronounced when samples were stored over 1200 days. Mineral water in PET bottles of 0.5 L had the highest phthalate concentrations compared to those obtained for waters of the identical brand bottled in 1.5-L or 2.0-L PET containers due to the higher surface/volume ratio. No clear trend could be established for phthalate leaching when water samples were kept at higher temperatures (max. 60 ºC) showing improper storage conditions. Phthalate determination by pyrolysis - gas chromatography/ mass spectroctrometric measurements in the plastic material as well as in the aqueous phase proved the importance of the quality of PET raw material used for the production of the pre-form (virgin vs. polymer containing recycled PET)

Égésgátló szereket tartalmazó műanyagok hőbomlása = Thermal decomposition of fire retardant containing plastics

Műanyag hulladékok közvetlen elégetésekor vagy pirolízis útján való hasznosításakor környezetre ártalmas vegyületek képződhetnek, amelyek fő forrása a polimerekhez gyakran jelentős arányban adagolt égésgátló. Pályázati kutatásunk eredményeképp megállapítottuk, hogy a bróm- vagy foszfortartalmú aromás szerves vegyület alkotta égésgátlókból származó brómatom és aromás gyökök elősegítik az ugyancsak gyökösen bomló polimer elszenesedését az égés hőmérsékletén, kisebb hőmérsékleten viszont az égésgátlók bomlástermékei jelentősen szennyezik a polimer pirolízisolaját. Az ammónium-polifoszfátból (APP) hő hatására felszabaduló ammónia elősegíti a polikarbonát és az azt felépítő biszfenol fenolokra bomlását. Az égésgátló szerekből származó brómtartalmú vegyületek kémiai eltávolítása ammónia atmoszférában végzett pirolízissel sikeresnek bizonyult: a pirolízisgáz brómmentes lett, a pirolízisolaj brómtartalma pedig egytizedére volt csökkenthető. A pirolízisolajak halogéntartalmának kiszűrésére a nátriumtartalmú, nagypórusú zeolitokat (NaY és 10X) találtuk alkalmasnak. Pirolízis-GC/MS analízisen alapuló gyors és megbízható módszert vezettünk be a katalizátorok halogén-mentesítő aktivitásának, majd a pirolízisolaj tisztítása során elszennyeződött katalizátor regenerálásának hatásosság tesztelésére. | Incineration or pyrolytic recycling of waste plastics may lead to the formation of polluting compounds, the main sources of which is the flame retardant added to the polymer often in considerable ratio. The research in this project lead to the conclusion that bromine atom and other radicals formed at the temperature of burning from bromine- or phosphor-containing aromatic organic compounds promote char formation in polymers decomposing also by radical reactions, while at lower temperature the thermal decomposition products of flame retardants contaminate considerably the pyrolysis oil of the polymer. Ammonia evolved from ammonium polyphosphate (APP) by heating promotes the thermal decomposition of polycarbonate and the cleavage of its bisphenol building unit to phenols. Chemical elimination of brominated compounds from the pyrolysate proved to be successful carrying out pyrolysis in ammonia atmosphere: bromine free pyrolysis gas and pyrolysis oil of considerably reduced bromine content was obtained. Sodium zeolites of large pores (NaY and 13X) were successfully applied for the elimination of bromine-containing aromatic compounds from pyrolysis oils. The dehalogenation activity of the various catalysts, moreover the effectiveness of regeneration of the contaminated used catalysts have been tested applying a novel, fast and reliable method based on pyrolysis-GC/MS analysis

Thermal decomposition of black locust and wheat straw under torrefaction

In this work the torrefaction of two typical Hungarian biomass materials, wheat straw and black locust wood was studied. Three different torrefaction temperatures were applied: 225, 250 and 300°C with one hour isothermal period. The untreated and torrefied biomass materials were characterized by thermogravimetric analysis (TGA) and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) techniques. The alkali ion contents of the samples were determined by ICP-OES technique. It was found that the thermal treatment at 225°C for 1 hour modifies the thermal decomposition mechanism of the cellulose content of the sample, indicating chemical changes in the cellulose structure. At 250°C the hemicellulose content of the analyzed biomass materials partially decomposes. Furthermore, the most labile lignin groups (terminal CH2OH) also start to decompose. At 300°C torrefaction temperature the major part of hemicellulose and cellulose decomposes. The degree of the cellulose decomposition highly correlates with the alkali ion content of the samples