Function Of Pyrolysis Temperature Research Articles

Development of long-range conductivity mechanisms in glass-like carbon

The conductivity mechanisms in glass-like carbon synthesised from SU-8 3005 photoresist are explored as a function of pyrolysis temperature (between 700–750 °C) utilising microwave dielectric spectroscopy techniques. Broadband measurements using an open-ended coaxial probe (BCP) are used to investigate the complex permittivity and conductivity as a function of frequency and show the development of long range conduction and sp2 carbon chain formation. Fixed frequency resonance measurements using microwave cavity perturbation (MCP) methods are shown as a way of measuring this transition and change in Q-factor without requiring contacts and therefore acting as a effective method for non-destructive and non-invasive measurements. Using these methods we show a clear change in the AC conductivity of glass-like carbon at a pyrolysis temperature of ∼730 °C and demonstrate how microwave cavity perturbation (MCP) can be used as a non-contact method of dielectric spectroscopy for determining the transition of conductivity mechanisms in glass-like carbon from short to long range and therefore as a method for non-destructive material quality control. We demonstrate that both BCP and MCP dielectric spectroscopy methods are effective at clearly detecting changes in the structure and conductivity mechanisms of glass-like carbon over a small pyrolysis temperature range.

Evolution and prediction model of environmentally-persistent free radicals in biomass three-component pyrolytic carbon with pyrolysis temperature

To clarify the evolution mechanism of environmentally-persistent free radicals (EPFRs) in biochar as a function of pyrolysis temperature, three-component pyrolytic carbon was characterized by electron paramagnetic resonance (EPR) spectroscopy. Four types of EPFRs were distinguished by using the peak splitting method. The EPFRs in three-component pyrolytic carbon obtained at a pyrolysis temperature of 300 °C were mainly oxygen-containing free radicals (57.31–83.63 %). Upon increasing the pyrolysis temperature, simple aromatic ring radicals were formed by the dehydrogenation of biomass, and then the polymeric aromatic radicals formed, accompanied by π-electron delocalization to form phenyl-π radicals. Biomass pyrolysis was simulated by mechanically mixing the three components in different proportions. A comparison of the experimental and theoretical values indicated that interactions between the three components did not obviously affect the EPFR concentration in the range of 450–550 °C, with a maximum relative error of 12.78 %. A prediction model for the EPFRs concentration in multi-component pyrolytic carbon was proposed. This study also clarified the generation and transformation mechanisms of EPFRs in three-component pyrolytic carbon, thus providing guidance for generating and regulating biochar EPFRs.

Sustainable and efficient removal of cationic, anionic and neutral dyes from water by pre-deposited vinasse biochar membrane

This study demonstrated a simple and sustainable approach for removing dyes from water through a new pre-deposited vinasse biochar (PDVB) membrane, which was developed by single-step deposition of vinasse biochar powder on a filter paper support via vacuum pumping. The PDVB membrane combined advantages of adsorption and membrane filtration processes in one-stage. Performance of the PDVB membranes with water-wettable surface was examined on methylene blue (as a model dye) solution as functions of pyrolysis temperature, amount of biochar on the membrane unit area, solution pH, initial concentration and temperature of dye solution in a dead-end filtration mode. The best performance (removal efficiency >99%, flux: 8017 L/(m2.h)) was obtained at a wide pH range (2−11) by using membrane (7.95 mg biochar/cm2, derived from pyrolysis of vinasse at 900 °C). Moreover, initial dye concentration and solution temperature had no considerable effect on membrane performance, which was stable even after ten cycles of filtration-regeneration by ethanol-washing. At pH 2, the membrane was also quite good at removing Congo red (anionic dye) with efficiency of 98%, which decreased when increasing pH from 2 to 11. Behavior of membrane towards dyes with different characteristics was explained by considering high surface area (756 m2/g) of the biochar and phenomenon, including aromatic stacking and electrostatic-attraction between dye molecule and biochar surface. All findings and application to a real textile industry effluent demonstrated that developed membrane was easy-to-use and sustainable material for effective treatment of water and wastewater containing dyes with different molecular weights and ionic characteristics.

Study on thermal degradation of poly (1,4 phenylene terephthalamide) and its volatile products by unadorned setup of Pyrolysis and subsequent UV–VIS spectroscopy

Pyrolysis involves the elimination of moisture and volatile components from fibrous materials by cleavage of molecular bonds to finally obtain carbon-rich residues. Over the years, there have been numerous studies on the pyrolysis of poly (1,4 phenylene terephthalamide) (Kevlar) and characterization of volatile products by using various analytical techniques. The main objectives of this work were to exhibit a simple and straightforward pyrolysis method using a smelting furnace, concurrently condensing the volatile products on a cold surface, followed by acquiring information on progressive changes in concentrations of decomposition products and their difference in volatility using UV-Vis spectroscopy, and to subsequently demonstrate an interesting algorithm for separation of mixture spectra. Variations in concentration of major elements (C, N, S, and O) were also monitored as a function of pyrolysis temperature. An increase in the concentration of volatile products was observed above 500 °C, reaching maximum at 700 °C and then progressively decreases towards the final temperature of 1100 °C. Separation of mixture spectra was attempted using the concept of spectral matrix decomposition to decompose measured spectra into possible spectra of individual components with the objective of proposing a fast and inexpensive method coupled with computational aid that contributes to kinetic studies of pyrolytic processes.

Biochar application strategies for polycyclic aromatic hydrocarbons removal from soils

Polycyclic aromatic hydrocarbons (PAHs) are known as a hazardous group of pollutants in the soil which causes many challenges to the environment. In this study, the potential of biochar (BC), as a carbonaceous material, is evaluated for the immobilization of PAHs in soils. For this purpose, various bonding mechanisms of BC and PAHs, and the strength of bonds are firstly described. Also, the effect of impressive criteria including BC physicochemical properties (such as surface area, porosity, particle size, polarity, aromaticity, functional group, etc., which are mostly the function of pyrolysis temperature), number of rings in PAHs, incubation time, and soil properties, on the extent and rate of PAHs immobilization by BC are explained. Then, the utilization of BC in collaboration with biological tools which simplifies further dissipation of PAHs in the soil is described considering detailed interactions among BC, microbes, and plants in the soil matrix. The co-effect of BC and biological remediation has been authenticated by previous studies. Moreover, recent technologies and challenges related to the application of BC in soil remediation are explained. The implementation of a combined BC-biological remediation method would provide excellent prospects for PAHs-contaminated soils.

Effect of HF and NaOH etching on the composition and structure of SiOC ceramics

Porous SiOC ceramics were prepared with tetraethoxysilane (TEOS) and vinyltriethoxysilane (VTES) as sol−gel precursors, and followed by etching with HF and NaOH solution. The microstructure evolution and chemical etching as a function of pyrolysis temperature were investigated. The amorphous carbon increases as rising the temperature from 800 o C to 1200 o C, and the graphitic carbon increases with further etching by HF and NaOH. However, the effect of pyrolysis temperature on the structure of C is more significant. The hydroxylation reaction and phase separation of SiOC ceramics results in the increase of SiO 4 unit, which reacts with HF and NaOH to form micro- and mesopores. The existence of mesopore after HF etching provides more specific surface area and pore volume. However, NaOH etching produces more micropores, and the contribution of micropores to specific surface area and pore volume is higher than that of mesopores. Although HF and NaOH etching increase the specific surface area of SiOC ceramics, the etching effect of NaOH is superior to that of HF etching, and the carbon-enriched SiOC ceramics are obtained after NaOH etching.

Synthesis of Nanocrystalline TiO<sub>2</sub> by the Extraction-Pyrolytic Method and its Phase Transformation in the Presence of Gadolinium

Due to its to its optical, thermal, photocatalytic and electrophysical properties, nanocrystalline titanium oxide (TiO2) is widely used in various fields. In the present work, a series of pure and Gd-modified (0.5, 5, 50 mol%) TiO2 nanocrystalline powders were prepared by a novel synthesis approach – extraction-pyrolytic method (EPM). Metal containing extracts on the basis of valeric acid were used as precursors. Thermal behavior of produced individual and mixed precursors were investigated by thermogravimetric analysis (TGA) and high temperature differential scanning colometry (HDSC). Phase composition of pure and Gd-modified TiO2 powders were studied as a function of pyrolysis temperature (450o -850°C ) and gadolinium content by X-ray diffraction (XRD) method. Photocatalytic activity of produced powders was studied by photocatalytic degradation of methylene blue (MB) under UV/VIS light irradiation.

Effect of pendant groups on the mass yield and density of polycarbosilanes during pyrolysis

AbstractAs SMP‐10 and SMP‐877 are pyrolyzed, they undergo multiple thermal decomposition reactions that result in the formation of amorphous SiC and differing degrees of excess carbon. Differences in the initial composition of the two polycarbosilanes in the form of allylic group concentration and the presence of methyl pendant groups lead to differences in thermal decomposition of the polymers. These differences then affect the evolution of density of the two polymers in a way that dramatically affects their volume yield as a function of pyrolysis temperature.

Robust intelligent topology for estimation of heat capacity of biochar pyrolysis residues

Biochar is recognized as a promising spectrum for thermal science applications considering environmental protection. In this study, different artificial intelligence (AI) techniques are employed to determine the heat capacity of biochar derived from pyrolysis of different biomass sources as a function of pyrolysis temperature, post-treatments process, and temperature. Relatively substantial experimental measurements are employed for adjusting the hyper-parameters of the considered AI methodologies. Accurate measurement using seven statistical criteria confirmed that the least-squares support vector machine (LS-SVM) with the Gaussian-type kernel is the best paradigm for the considered task. Statistical analysis shows an excellent capacity of the developed LS-SVM approach for estimation of heat capacity of biochar, i.e., mean square error (MSE) of 6.82, absolute average relative deviation (AARD) of 0.15%, and regression coefficient (R2) of one. Furthermore, the LS-SVM method accuracy is more than 700 times better than the developed empirical correlation in literature.

SiC-Coated Carbon Nanotubes with Enhanced Oxidation Resistance and Stable Dielectric Properties.

Carbon nanotubes (CNTs) coated with SiC coating was successfully prepared by pyrolysis of polycarbosilane (PCS) used as a precursor. The function of pyrolysis temperature on the oxidation resistance and the dielectric properties of CNTs/SiC were studied in X-band. The results demonstrate that the obtained dense SiC film can prevent the oxidation of CNTs when the pyrolysis temperature reaches 600 °C. Correspondingly, after heat treatment is at 400 °C for 200 h, the mass loss of P-600 is less than 1.86%, and the real and imaginary parts of the dielectric constant nearly keep constant (ε′ from 14.2 to 14, and ε″ from 5.7 to 5.5). SiC-coated CNTs have a better oxidation resistance than pristine CNTs. Therefore, this work, with a facile preparation process, enhances the oxidation resistance of CNTs at high temperature for a long time and maintains a stable dielectric property, which means CNTs/SiC composites can be good candidates for applications in the field of high-temperature absorbers.

Production of value-added aromatics from wasted COVID-19 mask via catalytic pyrolysis

In this study, wasted mask is chosen as a pyrolysis feedstock whose generation has incredibly increased these days due to COVID-19. We suggest a way to produce value-added chemicals (e.g., aromatic compounds) from the mask with high amounts through catalytic fast pyrolysis (CFP). To this end, the effects of zeolite catalyst properties on the upgradation efficiency of pyrolytic products produced from pyrolysis of wasted mask were investigated. The compositions and yields of pyrolytic gases and oils were characterized as functions of pyrolysis temperature and the type of zeolite catalyst (HBeta, HY, and HZSM-5), including the mesoporous catalyst of Al-MCM-41. The mask was pyrolyzed in a fixed bed reactor, and the pyrolysis gases evolved in the reactor was routed to a secondary reactor inside which the zeolite catalyst was loaded. It was chosen 550 °C as the CFP temperature to compare the catalyst performance for the production of benzene, toluene, ethylbenzene, and xylene (BTEX) because this temperature gave the highest oil yield (80.7 wt%) during the non-catalytic pyrolysis process. The large pore zeolite group of HBeta and HY led to 134% and 67% higher BTEX concentrations than HZSM-5, respectively, likely because they had larger pores, higher surface areas, and higher acid site density than the HZSM-5. This is the first report of the effect of zeolite characteristics on BTEX production via CFP.

Surface Charge Effects on Adsorption of Solutes by Poplar and Elm Biochars

Elm and poplar are two tree species that can provide a large amount of low-value feedstock for biochar production due to their rapid growth rate (poplar), and susceptibility to disease and/or infestation (both elm and poplar). Biochar has been studied recently as filtration medium for water purification, as it provides a renewable alternative to activated carbon. In this work, the adsorption efficiency of biochars made from elm and poplar as a function of pyrolysis temperature were studied by ultraviolet (UV) adsorption of dyes with positive, neutral, and negative charges to determine what factors had the greatest effect on adsorption of these dyes. It was found that conductivity of the biochars increased with pyrolysis temperature, and that this factor was more important than surface area in terms of adsorbing charged dyes. Both elm and poplar biochars were not effective in adsorbing neutral dyes. This research demonstrates that elm and poplar biochars adsorb charged (either positively or negatively) solutes more efficiently than uncharged ones because they carry both charges themselves. Therefore, these biochars would make excellent candidates as renewable filtration media for charged contaminants.

Effect of calcium dispersion and graphitization during high-temperature pyrolysis of beech wood char on the gasification rate with CO2

This paper presents thermal deactivation of beech wood chars during secondary pyrolysis in a drop-tube reactor. Pyrolysis temperature was varied between 1000 °C and 1600 °C at a constant residence time of 200 ms. The effect of pyrolysis conditions on initial conversion rate R0 during gasification, graphitization of the carbon matrix and ash morphology was investigated. Gasification experiments for the determination of R0 were conducted in a thermogravimetric analyzer using pure CO2 at 750 °C and isothermal conditions. A linear decrease in initial conversion rate R0 was observed between 1000 °C and 1400 °C. However, a strong increase of R0 at 1600 °C was encountered. Micropore surface area of the secondary chars showed no correlation with the initial conversion rate R0 during gasification with CO2. Graphitization of the carbon matrix was determined using X-ray diffraction and Raman spectroscopy suggesting the growth of aromatic clusters and graphite-like structures for increasing pyrolysis temperatures up to 1600 °C. Furthermore, CaO dispersion was analyzed quantitatively and qualitatively using temperature-programmed reaction at 300 °C as well as SEM/TEM. CaO dispersion DCaO decreases steadily between 1000 °C and 1400 °C whereas a strong increase can be observed at 1600 °C, which is in good accordance with the development of the initial conversion rate R0 as a function of pyrolysis temperature. SEM/TEM images indicate the formation of a thin CaO layer at 1600 °C that is presumably responsible for the strong increase in initial conversion rate R0 at this temperature. When excluding the catalytic activity of CaO via formation of the ratio R0DCaO−1, increasing graphitization degree has a linear negative influence on char reactivity at pyrolysis temperatures between 1000 °C and 1400 °C.

Chemical-physical analysis and exfoliation of biochar-carbon matter: from agriculture soil improver to starting material for advanced nanotechnologies

Biochar (BC) is a carbonaceous product obtained by pyrolysis, using lignocellulosic biomass. Feedstock and pyrolysis temperature affects the physical-chemical characteristics of the BC, and therefore its use and purpose. The main application of biochar is in the agricultural domain, however, it is considered as an effective strategy for the climate change mitigation, caused by the fact that carbon is not easily returned to the atmosphere during BC lifetime. Due to the presence of several carbon molecules, arranged from the thermochemical process of pyrolysis, biochar is a heterogeneous compound. Previous studies revealed a wide presence of interesting carbon molecules, therefore the biochar can be proposed as a useful material tank containing carbon structures used for different aims. Our study was focused on physical and chemical characterization of carbonaceous structures of a kind of biochar as a function of pyrolysis temperature. Biochar samples were produced by muffle furnace with the temperature range of 300 °C ÷650 °C. X-ray Diffraction (XRD) spectra were collected to determine crystal structures present in BC. Two broad peaks (002) and (100) were found corresponding to the turbostratic carbon crystallites. Raman Spectroscopy measurements were performed to examine different carbon-based molecules in the turbostratic-carbon phase of BC. Raman spectra showed an overlap between two peaks, corresponding to G band associated with graphite, and D band, displaying the aromatic rings arranged on layers, similar to graphene sheets. To separate and exfoliate carbonaceous structures, BC samples were exposed to ultrasonic bath. Atomic Force Microscopy (AFM) was used to characterize the nanostructures extracted. The presence of about 1 nm topographic height islands on mica substrate was found, consistent with a typical height of Few Layer Graphene (FLG) reported in the literature. From these results obtained, Biochar could be considered as a reservoir of materials for nanotechnology, such as graphene sheets.

(Invited) Revisiting the Nature of Active Sites in Pyrolyzed Fe-N-C Electrocatalysts: In Situ Monitoring the Structure Evolution of Active Sites in Fe-N-C Catalysts during Pyrolysis

Since it was found in 1980s that pyrolysis of the mixture of Fe, N, and C precursors leads to decent electrocatalysts for the oxygen reduction reaction (ORR), the nature of active sites high inherent ORR activity formed upon the heat treatment remains elusive. This mystery hasn’t been unraveled by recent applications of advanced spectroscopy and microscopy techniques.1-4 Herein, we conducted in situ x-ray absorption spectroscopy on carbon supported iron(II) phthalocyanine (FePc), as well as the mixture of ZIF-8, phenanthroline, Fe(II) acetate (namely MOF-derived catalyst) in a sealed inert gas environment as a function of pyrolysis temperature, in attempt to directly monitor the formation of new active sites. The FePc represents the Fe precursors with preexisting Fe-N4 moieties, and the Fe(II) acetate represents the precursors without. We observed the destruction of the in-plane Fe-N4 sites in FePc as a result of demetalization starting at a low temperature of ~300 ℃. However, we did not see the formation of new Fe-Nx active sites but metallic Fe clusters at elevated temperatures. The maximum of the ORR activity of the FePC/C pyrolyzed at 600 ℃ was attributed to the counterbalance between the loss of Fe-N4 sites and the increase of the carbon porosity caused by the demetalization, plus strengthening of the interactions between the FePc and carbon substrate, rather than creation of new active sites. On the other hand, during the pyrolysis of the MOF-derived catalyst, the XAS reveals the evolution from the Fe-O6 moiety to the Fe-N4 moiety with the local geometry resembling that of FePc but with longer Fe-N bond distance. The formation of metallic Fe clusters was not observed even at a high temperature of 1000 ℃. These results together suggest that the new active sites are likely formed upon the incorporation of Fe atoms into the N-doped carbon matrix during the pyrolysis. Compared to FePc/C, the carbon matrix in the MOF-derived catalyst appears to capture Fe atoms more efficiently forming Fe-N4 sites, owing probably to more abundant C-N cavities. Acknowledgement This work was supported by the US Department of Energy under award number DE-EE0008416. The authors declare no competing financial interests. MRCAT operations are supported by the Department of Energy and the MRCAT member institution. This research used resources of the Advanced Photon Source, a DOE Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357. References (1) Li, J.; Alsudairi, A.; Ma, Z.-F.; Mukerjee, S.; Jia, Q. Asymmetric Volcano Trend in Oxygen Reduction Activity of Pt and Non-Pt Catalysts: In Situ Identification of the Site-Blocking Effect. J. Am. Chem. Soc. 2017, 139, 1384-1387. (2) Li, J.; Ghoshal, S.; Liang, W.; Sougrati, M.-T.; Jaouen, F.; Halevi, B.; McKinney, S.; McCool, G.; Ma, C.; Yuan, X.; Ma, Z.-F.; Mukerjee, S.; Jia, Q. Structural and mechanistic basis for the high activity of Fe-N-C catalysts toward oxygen reduction. Energ Environ Sci 2016, 9, 2418-2432. (3) Jia, Q.; Ramaswamy, N.; Tylus, U.; Strickland, K.; Li, J.; Serov, A.; Artyushkova, K.; Atanassov, P.; Anibal, J.; Gumeci, C.; Barton, S. C.; Sougrati, M.-T.; Jaouen, F.; Halevi, B.; Mukerjee, S. Spectroscopic insights into the nature of active sites in iron–nitrogen–carbon electrocatalysts for oxygen reduction in acid. Nano Energy 2016, 29, 65-82. (4) Jia, Q.; Ramaswamy, N.; Hafiz, H.; Tylus, U.; Strickland, K.; Wu, G.; Barbiellini, B.; Bansil, A.; Holby, E. F.; Zelenay, P.; Mukerjee, S. Experimental Observation of Redox-Induced Fe–N Switching Behavior as a Determinant Role for Oxygen Reduction Activity. ACS Nano 2015, 9, 12496-12505. Figure 1

Determining organo-chemical composition of sugarcane bagasse-derived biochar as a function of pyrolysis temperature using proximate and Fourier transform infrared analyses

New research findings on biochar applications attracted considerable international attention as it offers environmentally sustainable solutions. This paper has focused on identifying the most important organo-chemical characteristics of slow pyrolysis bagasse-derived biochar as a function of pyrolysis temperature using proximate and Fourier transform infrared analysis. Therefore, a biochar thermosequence was produced by the pyrolysis of biomasses at 300, 400, 500, and 600 °C in a carbonization furnace. Organo-chemical transformations of biomasses during heating were followed by using chemical, proximate, and Fourier transform infrared (FTIR) analysis. The results can be summarized as follows. (1) Mass loss on ignition and oxidizable organic carbon content, respectively, decreased from 81.13 to 56.22% and 33.31 to 17.05% with increasing pyrolysis temperature from 300 to 600 °C. (2) The molar ratios of O/C, N/C, and H/C tended to decrease with increasing pyrolysis temperature. (3) Aromaticity equivalent (Xc) increased from 2.44 to 2.59 with increasing pyrolysis temperature from 300 to 600 °C. (4) The results of FTIR spectroscopy introduced the 1800–1100 cm−1 zone, related to oxygenated functional groups (OFGs), as region with most marked differences. (5) Results revealed an increase in the point of zero charge (pHpzc) with increasing pyrolysis temperature, indicating a decrease in the acidic OFGs and increase in the basic functionality. (6) Total acid functional groups concentration decreased from 9 to 5.8 mmol g−1 (based on Boehm titration) as the pyrolysis temperature decreased from 600 to 300 °C, while total basic functional groups concentration increased from 0.8 to 4.1 mmol g−1. (7) The cation exchange capacity, determined using NH4+ exchange, increased from nearly 18 to 105 cmolc kg−1 biochar as the pyrolysis temperature increased from 300 to 600 °C. In general, biochar produced at low temperature (< 500 °C) may improve nutrient availability and crop productivity in acidic and alkaline soils and also be suitable for removal of inorganic pollutants, whereas high-temperature biochar (≥ 500 °C) may enhance long-term soil carbon sequestration and also be suitable for removal of organic pollutants.

Characterization of Jordanian oil shale and variation in oil properties with pyrolysis temperature

Marine oil shale from the Sultani mine was characterized (ultimate and proximate analysis, 13C NMR, differential thermogravimetry (DTG)). The 13C NMR indicated that the shale is highly aliphatic, and the concentration of carbonyl carbon is small. DTG indicated a total weight loss of 21 wt% to 550 °C. The shale was pyrolysed to different final temperatures in the range 360–540 °C under N2 and the shale oils produced characterized by utilization parameters (API, heating value, boiling point distribution) and by chemical properties (1H-NMR and gas chromatography-mass spectrometry GC–MS) as a function of final pyrolysis temperature. Previous studies have only investigated the utilization properties of marine-shale oil at one temperature. The average oil yield increased with pyrolysis temperature to a maximum at 520 °C, and then fell. The oil density was higher at 440–520 °C than at 360–400 °C (0.99–1.00, 0.96−0.97 g/cm3 respectively). Unexpectedly, oil heating value (39.7–40.0 MJ/kg in 360–540 °C) and sulfur content (11.25 wt% in 360–520 °C) were independent of pyrolysis temperature. Oil distillation indicated that up to 90 vol% was in the diesel fraction.1H-NMR implied that the oil produced at all temperatures was highly aliphatic. GC/MS for the oil indicated the presence of long chain hydrocarbons (C11-C32), both normal and branched, some substituted benzenes, and high concentrations of sulfur compounds, mainly substituted thiophenes with same benzothiophenes. The average molecular weight of the sulfur compounds and proportion of heavier oil were higher at 520 °C than at 460 °C, so that the increased yield of oil at higher temperatures would have to be balanced against the lower quality of the crude shale oil produced. The results emphasized the importance of studying oil properties as a function of pyrolysis temperature, as differences which could be important in practice were noted.

Evolution of dielectric properties of thermally reduced graphene oxide as a function of pyrolisis temperature

Reduced grapheneoxide (rGO) is a derivative of graphene and its properties allow several applications, such as supercapacitors, sensors, filters, among others. The rGO was obtained at 400 °C and 1000 °C. These materials were analysed using Scanning Electron Microscopy, Transmission Electron Microscopy, Thermogravimetric Analysis, Differential Exploratory Calorimetry, X-Ray Diffraction, Raman Scattering Spectroscopy, Fourier Transform Infrared Spectroscopy and Vector Network Analyzer. The sample treated at 400 °C resulted in a more exfoliated material, presenting six sheets in the interlayer, with well-distributed aromatic symmetry and more electroactive groups. Thus, it showed higher electric permittivity in agreement with Raman G symmetry results, implying an increase of CC aromatic ring quantities, enabling this material to be used in electronic devices and nanocomposites with electromagnetic properties. This article aims to study the influence of structural and consequent changes in the dielectric properties of rGO samples as a function of pyrolysis temperature.

Effect of inherent minerals on sewage sludge pyrolysis: Product characteristics, kinetics and thermodynamics

Inherent minerals in sludge influence sludge pyrolysis behaviors and the final products. In this study, the effects of inherent minerals on sewage sludge pyrolysis were systematically investigated by studying the pyrolysis behaviors of raw sewage sludge (RS) and HCl-washed sludge (WS), and in combination with thermodynamic equilibrium simulations for the hypothetical mineral-free sludge (AS) assumed. The pyrolysis of RS and WS was performed with a novel online thermogravimetric analyzer equipped with an infrared spectrometer and a gas chromatograph coupled with a mass spectrometer (TG-IR-GC/MS). It was found that inherent minerals influenced both the release of volatile products as a function of pyrolysis temperature, and the development of the physicochemical properties of the derived char. In the temperature range of 300–500 °C, hydrocarbons with more than 4 carbon atoms as well as aromatic compounds showed an increased release during WS pyrolysis, with respect to RS, while hydrocarbons with less than 3 carbon atoms such as CH4 and C3H6 exhibited a decreased release. In addition, the inherent minerals enhanced the release of HCN and NH3, both leading to increased NO2 release, and the release of H2S and COS was also promoted while the release of CH3SH, SO2 and CS2 was mitigated. Kinetic analysis confirmed that a catalytic effect induced by the inherent minerals decreased the activation energy at 300–500 °C. Thermodynamic simulations suggested that inherent minerals influenced sludge pyrolysis and the derived products formation by increasing the total Gibbs energy of the sludge pyrolysis system. Therefore, considerations of sludge inherent minerals should be taken into account during pyrolysis for the purpose of value-added commodity production and pollutant mitigation.

Preparation of upgraded bio‐oil using two‐step catalytic pyrolysis of fresh, putrefied, and microbe‐treated biomass

In this study, water hyacinth was converted into highly flammable bio‐oil via two‐step catalytic pyrolysis. The upgradation of bio‐oil was based on the pretreatment of biomass, second‐step pyrolysis and use of clinkered material as a catalyst. This three‐prong approach was found effective for improving the nature and yield of the oil by lowering the water and oxygen content in the product. The yield of oil was investigated as a function of pyrolysis temperature and weight of the catalyst in addition to pretreatment of biomass. Optimum time for the reaction was also investigated for all three types of biomass. In the preliminary pyrolysis, each of the sample was pyrolyzed into an aqueous liquid, gas, and solid residue fractions. The liquid fraction of each of the sample was separated into combustible and non‐combustible liquids in addition to residue using fractional distillation. The residue of the fractional distillation for each of the fresh, putrefied, and microbe‐treated biomass was re‐pyrolyzed and the gas produced during 1st and 2nd steps of the pyrolysis was analyzed using chemical analysis. The upgraded oils were analyzed for their composition with GC‐MS technique. The oil products of the tested samples were significantly differing from each other in terms of nature and number of the compounds. © 2017 American Institute of Chemical Engineers Environ Prog, 37: 1836–1844, 2018