Thermo-catalytic pyrolysis of polystyrene in batch and semi-batch reactors: A comparative study

Thermo-catalytic pyrolysis is considered as a promising process for the chemical recycling of waste polymeric materials aiming at converting them into their original monomers or other valuable chemicals. In this regard, process parameters and reactor type can play important roles for an enhanced recovery of the desired products. Polystyrene (PS) wastes are excellent feedstocks for the chemical recycling owing to the capability of PS to be fully recycled. In this respect, the present work deals with the thermo-catalytic pyrolysis of PS in batch and semi-batch reactor setups. The main goal was to perform a comprehensive study on the depolymerisation of PS, thereby investigating the effect of reactor type, catalyst arrangement, feed to catalyst ratio and residence time on the yields of oil and styrene monomer (SM). A further goal was to identify the optimum operating conditions as well as reactor type for an enhanced recovery of oil and SM. It was demonstrated that the semi-batch reactor outperformed the batch reactor in terms of oil and SM yields in both thermal (non-catalytic) and catalytic tests performed at 400 degrees C. Furthermore, it was shown that the layered arrangement of catalyst (catalyst separated from PS) produced a higher amount of oil with higher selectivity for SM as compared to the mixed arrangement (catalyst mixed with PS). Moreover, the effect of carrier gas flowrate on the product distribution was presented.Web of Scienceart. no. 0734242x2093674

Influence of Miscanthus rhizome pyrolysis operating conditions on products properties

Waste from the Miscanthus production cycle may be a promising source of material for the pyrolysis and biochar production. The biochar can be used to enrich the soil on which the crop grows, thus increasing productivity. A sample of Miscanthus rhizomes was used as a raw material in a series of experiments in order to find the most suitable conditions for the preparation of biochar. Miscanthus biochar was prepared in a laboratory unit using four different temperatures (i.e., 400, 500, 600 and 700 degrees C). All pyrolysis products were subsequently evaluated in terms of their quality and product yields were determined. For a temperature of 600 degrees C and a residence time of 2 h, the appropriate properties of biochar were achieved and the process was still economical. The biochar contained a minimal number of polycyclic aromatic hydrocarbons and a high percentage of carbon. Surface area was measured to be 217 m(2)/g. The aqueous extract of biochar was alkaline.Web of Science1410art. no. 619

α-Fe2O3 nanoparticles/iron-containing vermiculite composites: Structural, textural, optical and photocatalytic properties

Vermiculite two-dimensional mixed-layer interstratified structures are a very attractive material for catalysis and photocatalysis. The iron-containing vermiculite from the Palabora region (South Africa) and its samples, which calcined at 500 and 700 degrees C, were studied in comparison with the alpha-Fe2O3 nanoparticles/vermiculite composites for the first time as photocatalysts of methanol decomposition, which is an organic pollutant and an efficient source for hydrogen production. The aim of the work was to characterize their structural properties using X-ray fluorescence, X-ray diffraction, infrared spectroscopy, nitrogen physisorption, diffuse reflectance UV-Vis spectroscopy and photoluminescence spectroscopy to explain the photocatalytic effects. The photocatalytic test of the samples was performed in a batch photoreactor under UV radiation of an 8W Hg lamp. The photocatalytic activity of vermiculite-hydrobiotite-mica-like layers at different water hydration states in the interstratified structure and the substitution ratio of Fe(III)/Al in tetrahedra can initiate electrons and h holes on the surface that attack the methanol in redox processes. The activity of alpha-Fe2O3 nanoparticle photocatalysts stems from a larger crystallite size and surface area. The hydrogen production from the methanol-water mixture in the presence of vermiculites and alpha-Fe2O3 nanoparticles/vermiculite composites was very similar and higher than the yield produced by the commercial TiO2 photocatalyst Evonik P25 (H-2 = 1052 mu mol/g(cat.)). The highest yield of hydrogen was obtained in the presence of the Fe/V-700 composite (1303 mu mol/g(cat) after 4 h of irradiation).Web of Science125art. no. 60

Hematites precipitated in alkaline precursors: Comparison of structural and textural properties for methane oxidation

Hematite (alpha-Fe2O3) catalysts prepared using the precipitation methods was found to be highly effective, and therefore, it was studied with methane (CH4), showing an excellent stable performance below 500 degrees C. This study investigates hematite nanoparticles (NPs) obtained by precipitation in water from the precursor of ferric chloride hexahydrate using precipitating agents NaOH or NH4OH at maintained pH 11 and calcined up to 500 degrees C for the catalytic oxidation of low concentrations of CH4 (5% by volume in air) at 500 degrees C to compare their structural state in a CH4 reducing environment. The conversion (%) of CH4 values decreasing with time was discussed according to the course of different transformation of goethite and hydrohematites NPs precursors to magnetite and the structural state of the calcined hydrohematites. The phase composition, the size and morphology of nanocrystallites, thermal transformation of precipitates and the specific surface area of the NPs were characterized in detail by X-ray powder diffraction, transmission electron microscopy, infrared spectroscopy, thermal TG/DTA analysis and nitrogen physisorption measurements. The results support the finding that after goethite dehydration, transformation to hydrohematite due to structurally incorporated water and vacancies is different from hydrohematite alpha-Fe2O3. The surface area SBET of Fe2O3_NH-70 precipitate composed of protohematite was larger by about 53 m(2)/g in comparison with Fe2O3_Na-70 precipitate composed of goethite. The oxidation of methane was positively influenced by the hydrohematites of the smaller particle size and the largest lattice volume containing structurally incorporated water and vacancies.Web of Science2315art. no. 816

Effect of torrefaction on pellet quality parameters

Torrefied biomass is characterized as a high-quality renewable energy commodity that can substitute fossil fuels. Combined torrefaction and pelletization are used to increase the value of biomass by improving its handling and fuel properties. The aim of this study is to present the influence of pelletization process on torrefaction in a pilot-scale unit. Above that, two process modes were assessed, and the properties of the torrefied and pelletized biomass and vice versa were studied. Mode I involved torrefaction prior pelletization. In mode II, on the contrary, the waste biomass was first pelletized and then torrefied. Analysis of mechanical parameters and chemical composition was therefore used to determine which of the modes was more advantageous. The results showed that within both modes it is evident that a higher torrefaction temperature caused wettability index decrease with a simultaneous higher heating value increase. Pellets produced in mode I showed better calorific values, however worse mechanical properties particularly durability.Web of Scienc

Chemical recycling of waste polypropylene via thermocatalytic pyrolysis over HZSM-5 catalysts

The present work deals with the chemical recycling of waste polypropylene viathermocatalytic pyrolysis over HZSM-5 zeolite catalysts. The main aim was tosystematically investigate the influence of reactor configuration, zeolite acidity,polypropylene wastes, obtained from different sources, as well as catalyst regener-ation on the product distribution. It was demonstrated that the reactor configura-tion and the acid site density of HZSM-5 catalysts strongly influence the productyields and distributions. The different types of polypropylene waste, on the otherhand, showed a comparatively small yet noticeable effect on the product distribu-tion. Moreover, it was demonstrated that the HZSM-5 catalysts exhibit goodregeneration capacity during regeneration-reaction cycles.Web of Science4661297128

Conductivity of carbonized and activated leather waste

The conductivity of chromium-tanned pigskin leather waste carbonized in various manner to nitrogen-containing carbons is reported. Four protocols have been tested: (1) The simple carbonization at 800 °C in inert atmosphere, (2) the carbonization at 500 °C followed by the activation with potassium hydroxide at 800 °C, (3) direct activation with the alkali at 800 °C and (4) the similar activation with potassium hydroxide excess. The fibrous collagen morphology was preserved after the carbonization except for some shrinkage. The yield in the simple carbonization, 26.9 wt%, was reduced to 23.9 wt% for the activated products. Elemental analysis indicated reduced content of organic elements after carbonization, and X-ray fluorescence the composition of growing inorganic part. The chromium content in biochar was close to 12 wt% and the X-ray diffraction revealed also the presence of metallic chromium in addition to expected chromium(III) oxide and sulfide. FTIR and Raman spectroscopies demonstrated the typical pattern of carbonized materials. The specific surface area and pore volume increased after the activation. The resistivity of the powdered carbonized leather was determined in four-point van der Pauw setup. It decreased by more than one order of magnitude as applied pressure increased from 0.1 to 10 MPa. The sample conductivity depended only a little on the way of carbonization and was of the order of tenths to units S cm−1 at 10 MPa. The precarbonization followed by the activation provided the best result with respect to the yield, nitrogen-content, specific surface area and conductivity of the carbonized material. © 2023 Elsevier B.V.Ministerstvo Školství, Mládeže a Tělovýchovy, MŠMT, (FRC/RO 70200003025/2102, LM2023056

Conductivity of carbonized and activated leather waste

The conductivity of chromium-tanned pigskin leather waste carbonized in various manner to nitrogen-containing carbons is reported. Four protocols have been tested: (1) The simple carbonization at 800 °C in inert atmosphere, (2) the carbonization at 500 °C followed by the activation with potassium hydroxide at 800 °C, (3) direct activation with the alkali at 800 °C and (4) the similar activation with potassium hydroxide excess. The fibrous collagen morphology was preserved after the carbonization except for some shrinkage. The yield in the simple carbonization, 26.9 wt%, was reduced to 23.9 wt% for the activated products. Elemental analysis indicated reduced content of organic elements after carbonization, and X-ray fluorescence the composition of growing inorganic part. The chromium content in biochar was close to 12 wt% and the X-ray diffraction revealed also the presence of metallic chromium in addition to expected chromium(III) oxide and sulfide. FTIR and Raman spectroscopies demonstrated the typical pattern of carbonized materials. The specific surface area and pore volume increased after the activation. The resistivity of the powdered carbonized leather was determined in four-point van der Pauw setup. It decreased by more than one order of magnitude as applied pressure increased from 0.1 to 10 MPa. The sample conductivity depended only a little on the way of carbonization and was of the order of tenths to units S cm−1 at 10 MPa. The precarbonization followed by the activation provided the best result with respect to the yield, nitrogen-content, specific surface area and conductivity of the carbonized material.Web of Science35art. no. 10117

Evaluation of the impact of varied biochars produced from M. × giganteus waste and application rate on the soil properties and physiological parameters of Spinacia oleracea L.

The use of M. x giganteus in phytoremediation requires treatment of the contaminated biomass, which can be done by pyrolysis to produce biochar. Due to its potentially detrimental properties, the application of biochar in soil remediation must first be evaluated on a test plant to infer how the growth process was affected by the impact on soil parameters. The main goal of the current research was to investigate the effects of waste-derived Miscanthus biochars (from contaminated rhizomes (B1) and aboveground biomass (B2)) on soil properties and evaluate the impact of biochar doses and properties on Spinacia oleracea L. growth. It was revealed that incorporation of B1 at a dose of 5% and B2 at doses of 1, 3, and 5% increased soil organic carbon, pH, K (at 3 and 5%), and P2O5 (at 5% B2). Cultivation of S. oleracea reduced organic carbon, soil pH as a function of biochar dosage, and K, P2O5, NH4, and NO3 content in all treatments tested. The highest biomass yield was recorded at 3% B2. The photosynthetic parameters indicated that the doses of 3 and 5% B2 led to dissociation of light-harvesting complexes. Increasing the biochar dose did not necessarily increase yield or improve photosynthetic parameters. S. oleracea adapted to the initial stress by incorporating biochar and managed to establish a balance between nutrients, water supply, and light. It is recommended that the effects of biochar on the development of the target crop be evaluated through preliminary trials before biochar is applied at field scale.Web of Science28art. no. 10289

The influence of diesel contaminated soil on Miscanthus x giganteus biomass thermal utilization and pyrolysis products composition

The second-generation energy crop Miscanthus x giganteus (Mxg) demonstrated ability to produce adequate biomass yield even in marginal or contaminated soils. This renewable biomass can be utilized energetically or transformed into various biobased products and thus contribute to decrease of primary resources and fossil fuel use. To evaluate potential effects on energetic biomass properties Mxg was grown in diesel contaminated soils. Traces of total petroleum hydrocarbons were found solely in the leaves, however most likely resulting from air contamination. No differences were detected in the elemental composition of the raw biomass. Biomass combustion heat value reached average of 17.23 ± 0.21 MJ kg−1; contamination-originated leaves had slightly but significantly decreased heat values (14.41 ± 1.10 MJ kg−1) while heat of other parts was comparable to control. Thermogravimetric curves, simulating thermic utilization processes, were comparable both under oxygen (combustion) and nitrogen (pyrolysis). No diesel impacts were observed on the pyrolysis products yield. Higher amounts of CH4, C2H6, C3H4, C3H6 and C3H8 were detected in the pyrolysis gas from aboveground biomass from contaminated soil. Diesel contamination decreased significantly biochar surface. Concentrations of acids and esters in biooil were increased on the expense of concentrations of furans in the case of samples from contaminated soils. No significant effect on phenols and ketones concentrations in the biooil was observed. The amount of acetic acid, as the main biooil component, increased in the above- and below-ground plant parts along with the higher diesel concentrations in soil. Despite slight changes detected, the parameters of the biomass produced in diesel-contaminated soils present no obstacle to its energetic utilization and Mxg can be recommended for productive phytomanagement of such soils.Web of Science406art. no. 13698