Low Pyrolysis Research Articles

Development of biochar from crofton weed & relationship between biochar properties and its applicability as a heavy metal removal activity

Biochar is a pyrogenic black carbon produced from thermal degradation of carbon-rich biomass (<700°C) in an oxygen-limited environment, and usually has a porous structure, a surface rich in oxygenated functional groups, strong adsorption capacity, and a certain degree of surface area and stability. Biochar has multiple uses, including agricultural applications for soil remediation and pollution control in water and soil. Biochar has several significant socioeconomic and environmental benefits such as carbon sequestration, pollutant removal, and soil improvement. Pyrolysis temperature affects biochar properties, which in turn determines its application potential. The collected Crofton weed (except for the roots) was washed, air-dried at room temperature, and crushed for passage through a 10-mesh sieve. Here, we examined the properties of Crofton weed biochar (C-BC) produced at different pyrolysis temperatures of 300°C, 400°C, 500°C, and 600°C. We measured the yield, ash content, pH, iodine sorption value (ISV), and elemental composition of C-BC. We also characterized C-BC using scanning electron microscopy (SEM), as well as its ability to remove Pb2+and Cd2+contaminantsfrom an aqueous solution. C- BC yield decreased with increasing pyrolysis temperature, whereas ash content and pH increased. ISV first increased at 300–400°C and decreased at 500–600°C. For C-BC produced at pyrolysis temperatures 300–600°C (C-BC300 to C-BC600, respectively), H, N, and O content decreased, but C, Ca, Mg, P, and K content in- creased with increasing temperature. All C-BCs had a certain number of pore structures. Increasing pyrolysis temperatures decreased the amount of -OH, -COOH, aliphatic C-H, and polar C-O on the C-BC surface. The percentage of Pb2+and Cd2+removed increased with increasing pyrolysis temperatures. Overall, for C-BC, a low pyrolysis temperature was beneficial for producing a more porous biochar and increased content of water-soluble calcium, magnesium, nitrogen, and phosphorus, whereas high pyrolysis temperatures yield biochar that had high alkalinity, aromaticity, and stability, as well as heavy metal removal activity

Graphene as a promising additive to hierarchically porous carbon monoliths for enhanced H2 and CO2 sorption

This study aimed to examine a synthesis of hierarchically porous carbon monoliths (HPCM) doped with graphene oxide (GO) for H2 and CO2 sorption applications. The synthesis procedure combining the sol-gel process with soft-templating was tuned by adding different quantities of GO (0.5; 2 and 10 wt% of the total amount of polycondensation mixture), as well as different carbonization temperatures (500 °C, 900 °C) of the composite materials during which the reduction of GO to graphene occurs. The degree of GO reduction to graphene and its incorporation into the HPCM matrix of prepared materials were characterized by Raman, FTIR, SEM, TEM, and elemental analysis. Although incorporation was successful, the higher pyrolysis temperature of 900 °C promotes the reduction of GO to graphene, which enhances the (ultra)microporosity (proven by gas physisorption experiments) of the samples, especially of the one with 10% GO addition. The effectivity of materials towards H2 and CO2 sorption was examined by sorption of H2 (77 K, up 1 bar) and CO2 (273 K, up 1 bar), respectively. Addition of any amount of GO together with the used lower pyrolysis temperature of 500 °C reduced the adsorption capacity of the samples for CO2 (from 2.4 to 1.8 mmol g−1) and H2 (from 5.8 to 3.6 mmol g−1) compared to the original HPCM. On the bright side, a 10% addition of GO in combination with a pyrolysis temperature of 900 °C results in industrially perspective material with an H2 and CO2 adsorption capacity of 9.6 mmol g−1 and 4.6 mmol g−1, respectively.

Efficient and stable Ni-supported novel porous Ca-Mg-Al complex oxide catalyst for catalytic pyrolysis of oleic acid into gasoline-kerosene rich production using methanol as a hydrogen donor: Synthesis methods and process optimization

In this study, a series of cost-effective and eco-friendly Ca-Mg-Al and Ni-modified Ca-Mg-Al catalysts were successfully synthesized with different methods (coprecipitation, impregnation and mechanical mixing method) and applied to catalytic pyrolysis vapor upgrading of oleic acid (OA) to produce gasoline-kerosene rich production using methanol as a hydrogen donor. In addition, the effects of the process parameters (catalyst type, OA to methanol ratio, pyrolysis/catalytic temperature, catalyst loading, feedstock injection volume) on the product yield and selectivity were explored, and the reuse properties and deactivation mechanism were also evaluated. Active Ni species coupled with methanol were more conducive to enhancing the catalyst activity and OA conversion and obviously increased the selectivity toward the gasoline-kerosene product. The impregnation method was favorable for the formation of NiAl2O4 species, and coprecipitation method suppressed the formation of NiAl2O4 species. The enhanced activity and deoxygenation selectivity of the coprecipitation method (NiCaMgAl) at lower pyrolysis temperatures was attributed to the abundant higher specific surface area and pore size, higher active metal oxide (Ni2+) and well-active Ni dispersion with a smaller particle size, as well as the lower acidity and partially oxidized Ni, which suppressed the NiAl2O4 spinel phase formation compared with the Ni/Ca-Mg/Al (impregnation) and Ca-Mg-Al (mixing) catalysts, which was beneficial to the decarbonylation/ decarboxylation reaction and inhibited the hydrocracking reaction of CC. Therefore, 100% conversion, 97.12% hydrocarbon yield, 54.53% gasoline and 58.80% kerosene content over NiCaMgAl catalyst were obtained under optimal conditions (pyrolysis/catalytic temperature = 450/500°C, catalyst loading = 1.5 g, feedstock injection volume = 0.1 ml/min and OA to methanol ratio = 3:1). Moreover, NiCaMgAl catalyst also demonstrated good reusability and hydrothermal stability performance due to the lower amount of coke deposition with a lower graphitized structure, which suppressed sintering.

Petrographical and geochemical investigation on maturation and primary migration in intact source rock micro-plugs: Insight from hydrous pyrolysis on Woodford Shale

This study proposes a new approach to investigate primary migration in petroleum source rocks under laboratory conditions. It was conducted on organic carbon-rich, type II kerogen-bearing Upper Devonian-Lower Mississippian Woodford Shale. Hydrous pyrolysis was performed on polished source rock micro-plugs at different temperatures. Maceral characteristics are observed before and after the different pyrolysis experiments. Applying this new approach, in situ maceral changes at different maturities are directly visualized at the exact same place after artificial maturation at 300 °C, 320 °C, 330 °C, and 340 °C for 24 h. After each heating step, the surface was cleaned with dichloromethane. The bitumen adsorbed to some of the Tasmanites surfaces leads to the brighter fluorescence color after chemical extraction. Leiosphaeridia alginites are less stable than Tasmanites; they first expand and then shrink during thermal evolution partly leaving empty holes in the matrix. Tasmanites keep a strong yellow fluorescence and start to bituminize at the edge of the particles. Liptodetrinite shows significantly decreasing fluorescence intensities already at low pyrolysis temperature (320 °C) and disappears to a great extent at 330 and 340 °C.

Reaction characteristics of maximizing light olefins and decreasing methane in C5 hydrocarbons catalytic pyrolysis

When converting C5 hydrocarbons to light olefins by catalytic pyrolysis, the generation of low value-added methane will affect the atomic utilization efficiency of C5 hydrocarbons. To improve the atomic utilization efficiency, different generation pathways of light olefins and methane in the catalytic pyrolysis of C5 hydrocarbons were analyzed, and the effects of reaction conditions and zeolite types were investigated. Results showed that light olefins were mainly formed by breaking the C2–C3 bond in the middle position, while methane was formed by breaking the C1–C2 bond at the end. Meanwhile, it was discovered that the hydrogen transfer reaction could be reduced by about 90% by selecting MTT zeolite with 1D topology and FER zeolite with 2D topology under high weight hourly space velocity (WHSV) and high temperature operations, thus leading to the improvement of the light olefins selectivity for the catalytic pyrolysis of n-pentane and 1-pentene to 55.12% and 74.60%, respectively. Moreover, the fraction ratio of terminal C1–C2 bond cleavage was reduced, which would reduce the selectivity of methane to 6.63% and 1.83%. Therefore, zeolite with low hydrogen transfer activity and catalytic pyrolysis process with high WHSV will be conducive to maximize light olefins and to decrease methane.

Experimental and kinetics study of NO heterogeneous reduction on semi-coke and its chars: Effects of high-temperature rapid pyrolysis and atmosphere

The high-temperature rapid pyrolysis has an evident impact on NO heterogeneous reduction over semi-coke char, which is rarely reported before. This study systematically evaluated the reactivity and kinetics of NO reduction over semi-coke and its rapid pyrolysis chars with the presence of O2 and CO using a fixed-bed reactor. The experimental results showed that the rapid pyrolysis at a desirable temperature of roughly 1100 °C can promote NO reduction over semi-coke, but excessively high and low pyrolysis temperatures were unfavorable for char-NO reaction. Partially explaining the situation was the trend of a rise before fall in specific surface area and C–O bond content of char with the rising pyrolysis temperature. The rapid pyrolysis char formed above 1100 °C showed lower activation energy than the fixed-bed pyrolysis char by 24.10%, but the higher one by 12.55% at 900 °C. The presence of CO noticeably promoted the NO reduction and reduced the activation energy by up to 41.73% at 0.75% CO, while the addition of oxygen inhibited NO reduction over semi-coke char. The suitable pyrolysis temperature with the presence of CO favored NO reduction over rapid pyrolysis char, which guided semi-coke utilization as a fuel or reducing agent.

Binding characteristics of Pb and Zn to low-temperature feces-based biochar-derived DOM revealed by EEM-PARAFAC combined with general and moving-window two-dimensional correlation analyses.

Pyrolysis carbonization of human feces has shown potential for converting feces biomass into a soil amendment. However, little is known about the interactions of DOM derived from feces-based biochar produced at low-temperature with heavy metals (HMs). In this study, the binding properties of Pb(II) and Zn(II) with DOM derived from feces-based biochar produced at low pyrolysis temperatures were investigated using EEM-PARAFAC combined with general, and moving-window two-dimensional correlation analyses (2D-COS). The results revealed that DOM from biochar produced at 280°C exhibited a higher Pb(II) and Zn(II) affinity and more binding sites than DOM produced at 380°C. The fulvic-like and humic-like components exhibited obvious fluorescence quenching after the heavy metal addition, and the complexes formed with Pb(II) and Zn(II) were more stable. C-H groups exhibited the fastest response to Pb(II) and Zn(II) binding in the FB280 DOM, while the COO- groups of carboxylic acids in the FB380 DOM exhibited the fastest response to Pb(II) and Zn(II). Moreover, the mutation concentration range of components and functional groups in DOM, as analyzed by MW2D-COS, was greater for Zn(II) than for Pb(II). These results provide a more detailed molecular-level understanding of the interaction mechanisms between heavy metals and feces-based biochar-derived DOM and the effect of HM concentration on DOM binding. Further, these results will help to provide a reasonable reference for feces management and feces-based biochar in controlling soil HMs.

In situ synthesis of highly dispersed Fe/C catalysts with pomelo peel as carbon source in CO2 hydrogenation to light olefins

Although considerable progress has been made in the hydrogenation of CO2 to light olefins through the modified Fischer-Tropsch synthesis route (CO2-FTS), the design of catalysts with high selectivity and stability is still a challenge. Herein, a simple, highly dispersed and scalable Fe/C-400 catalyst was prepared by in-situ pyrolysis using pomelo peel (PP) as carbon source, and was first used in CO2 hydrogenation to light olefins. This catalyst exhibited a high space time yield of light olefins (48.3 μmolCO2·gFe−1·s−1), and the light olefins selectivity and O/P were 63.0% and 9.0, respectively. More surprisingly, no obvious deactivation was observed within 200 h. A series of characterization techniques such as TEM, TG-MS, FTIR, XPS, H2-TPR and 57Fe Mössbauer spectrum showed that the naturally abundant oxygen-containing functional groups in PP support could impart metal-support interactions that enhance the dispersion of iron species. The modulation of the catalyst phase composition was achieved by simply varying the residual amount of oxygen-containing functional groups to impart different metal-support interactions. The catalysts prepared at lower pyrolysis temperatures retained more oxygen-containing functional groups and therefore had stronger metal-support interactions, which facilitated the formation of more active phases. Overall, this newly developed catalyst realized the high activity and high stability production of CO2 hydrogenation to light olefins, providing a cost-effective and sustainable way for its industrial application.

Effects of pyrolysis temperature and feedstock type on biochar characteristics pertinent to soil carbon and soil health: A meta‐analysis

AbstractBiochar amendment to soil is utilized globally as an approach to enhance carbon storage and to improve soil functioning. However, biochar characteristics and related improvements of soil functioning depend on biochar production conditions. Systematic evaluation of corresponding biochar characteristics is needed for more targeted and efficient biochar application strategies. Herein, we systematically review the effects of biochar pyrolysis temperature (175–950°C) and feedstock (corn stover, switchgrass and wood) on selected biochar characteristics (carbon content, H/C ratio, nitrogen content, pH, specific surface area, ash content and pore volume). These specific characteristics were selected as being pertinent to soil organic carbon sequestration and soil health improvement. Despite numerous studies on these topics, few have numerically quantified the effects of pyrolysis temperature. Our results show that high pyrolysis temperature (>500°C) increased carbon content and pore volume for wood biochar compared with low pyrolysis temperature (≤500°C). The high pyrolysis temperature decreased the H/C ratio and nitrogen content but increased pH, specific surface area and ash content regardless of feedstock. Compared with corn stover biochar and switchgrass biochar, wood biochar had higher carbon content and larger specific surface area but lower nitrogen and ash contents regardless of pyrolysis temperature. The higher biochar carbon content might be derived from higher lignin and cellulose contents of wood feedstock. Wood feedstock had 76%–109% more lignin and 27%–47% more cellulose than corn stover and switchgrass. Corn stover biochar had higher pH, and switchgrass biochar had larger pore volume than wood biochar. Our study indicates that the targeted production of biochar with specific characteristics can be facilitated by the selection of pyrolysis temperature and feedstock type. For amending soil with biochar, more operationally defined biochar production conditions and feedstock selection might be a way forward to wider acceptance and better predictability of biochar performance under field conditions.

The preferential preservation of both different minerals and polyethylene microplastics on aromatic or aliphatic carbon fractions within low or high pyrolysis temperature biochar under mineralization

The effects of soil minerals and microplastics on the stability of biochar (BC) have not been clearly clarified. Here, the mineralization of BC produced at low and high temperatures (L-BC and H-BC) and their artificial soils made of quartz, smectite and kaolinite, respectively, was investigated. BC and BC artificial soils were incubated with or without polyethylene (PE) over 180 d, and the CO2 emission, molecular composition and microbial community structure were assessed. Minerals, especially quartz, had relatively more protection to H-BC than to L-BC. Moreover, smectite preserved aliphatic C of L-BC, and kaolinite protected its aromatic C and aliphatic C. Smectite and kaolinite likely had comparable ability to protect BCs. Quartz protected the aromatic C of H–BCs by adsorbing the hydrophobic aromatic C. Minerals also led to the shift of the dominant bacteria from r-strategists to K-strategists, which alleviated degradation of labile carbon and reduced the CO2 emissions. PE decreased the CO2 emissions of L-BC as well as its artificial soils and the opposite effect was observed for H-BC. PE enhanced the aromatic C associated with minerals within H-BC artificial soils, and inhibited the mineralization of H-BC. PE degradation by fungi (Aspergillus) could be largely responsible for the rise in CO2 emissions of H-BC artificial soils. This study addressed the different effect of minerals and PE in the process of BC mineralization and provided the basis for elucidating the stability mechanism of BC in soil, which would be helpful for establishment of BC carbon sequestration policy.

Structural Aspects of Materials in Optimization of Fuel Cell Electrodes.

Today's energy problems, caused by the irrational consumption of fossil fuels and, as a result, terrible environmental consequences, require the global population to quickly introduce clean energy sources. Electrochemical power sources, which include the fuel cell, provide the technological basis for electrical energy production. While proton exchange membrane fuel cells (PEMFC) rely on platinum based catalysts, obtaining stable and earth abundant catalytic materials for the oxygen reduction reaction (ORR) is an important step towards large scale integration. Our work focusses on FeNC noble-metal free catalysts in PEMFC conditions. The reaction conditions are much more complex in comparison to half cells, as transport processes and e.g. carbon oxidation affect the performance data. Thus, it turns out to be extremely difficult to determine the most important factors affecting the catalytic activity and stability of the material and to optimize the structure of the membrane-electrode assembly as several factors are overlaying each other: For example, the pyrolysis temperature affects the surface area, degree of graphitization and iron-related composition as well as extent of surface functional groups [1]. The metal loading, pyrolysis temperature and a use of possible precursor templates effects the structure, surface area as well as ORR activity and selectivity of catalysts [2], [3].In our recent work, it was shown that in contrast to the electrochemical characteristics observed in rotating disc electrode (RDE) measurements, the best performing catalyst was prepared at the highest investigated temperature for both FC activity and stability [1]. In contrast, the dwell time had only a limited impact at low pyrolysis temperature, whereas a variation from 30 min to 90 min gave significant destruction of molecular FeNx moieties for the high temperature pyrolysis. [1]To gain further insights on the effect of preparation parameters on FC performance and in specific stability, we coupled a quadrupole mas-spectrometer to the cathode exhaust to follow possible release of CO2 depending on the applied conditions. The data are interpreted together with the structural characterization of the materials. We will discuss how the dwell time and pyrolysis temperature effected on morphology changes of the catalyst and to what extent this impacts the FC activity and short-term stability.AcknowledgementsA.O. would like to thank you the TU Darmstadt for the Future talent scholarship, UIK gratefully acknowledges financial support by the BMBF young research group StRedO (03XP0092), and we thank Y. Ostroverkh, and Z. L. Müller, for the consultation and assistance with the fuel cell setup.[1] J. Scharf, M. Kübler, V. Gridin, W.D.Z. Wallace, L. Ni, S.D. Paul, U.I. Kramm, Relation between half-cell and fuel cell activity and stability of FeNC catalysts for the oxygen reduction reaction, (2022) SusMat, accepted (doi: 10.1002/sus2.84).[2] P.Theis, W.D. Z. Wallace, L. Ni, M. Kübler, A. Schlander, R. W. Stark, N. Weidler, M, Gallei, U. I. Kramm. Systematic study of precursor effects on structure and oxygen reaction activity of FeNC catalysts, (2021) Philos. Trans. Royal Soc. A PHILOS T R SOC A, (doi: 10.6084/m9.figshare.c.5506708).[3] P. Boldrin, D. Malko, A. Mehmood, U. I. Kramm, S. Wagner, S. Paul, N. Weidler, A. Kucernak. Deactivation, reactivation and super-activation of Fe-N/C oxygen reduction electrocatalysts: Gas sorption, physical and electrochemical investigation using NO and O2., (2021) Appl. Catal. B, Vol. 292, 120169, (doi: 10.1016/j.apcatb.2021.120169).

A synthesis of soil organic carbon mineralization in response to biochar amendment

Biochar amendment can alter native soil organic carbon (SOC) mineralization via the priming effect (PE); however, its direction, intensity, and controls over a broad geographic scale are not clear, undermining the predictions of SOC dynamics as impacted by biochar inputs. Here, we synthesized 5,720 measurements of CO2 effluxes from 329 soil samples with and without 13C/14C labeled-biochar additions to quantify the spatial patterns and temporal dynamics of the PE and assess the underlying environmental drivers. Across all data, biochar amendment has led to a slight but significant positive PE (i.e., 56 mg C kg−1 soil), with stronger PEs in natural ecosystems than in agricultural soils. Negative PE occurred in the short term (i.e., <9 days after biochar addition) and subsequently shifted to a strong positive PE (i.e., 364–966 days) and remained in an insignificant PE thereafter (i.e., >1450 days). Notably, soils from rainfed croplands had the lowest negative PE (−28.76 mg C kg−1 soil). Grass-derived biochar produced at a low pyrolysis temperature (i.e., 300–400 °C) induced the strongest positive PE (244 mg C kg−1 soil). The results of our structural equation model indicated that biochar pyrolysis temperature and soil C:N ratio had the largest negative and direct association with biochar-induced PE, whereas incubation temperature and microbial biomass C exerted the greatest positive and direct effects on the PE. Variance partitioning analyses further revealed that both biochar and soil properties together accounted for 73% of the explained variance in biochar-induced PE. Overall, these results add to our understanding of biochar-induced SOC priming as impacted by different land-use types, soils, and biochar properties. The amendment of wood-derived biochars produced at high pyrolysis temperatures (>500 °C) to rainfed croplands could serve as a promising strategy to achieve maximum soil C sequestration.

Flashpoint and burning of thin molten plastic pool above hot boundary

The melting and dripping of burning thermoplastics can cause a new ignition and form a plastic pool fire, resulting in a significant fire risk. This work investigates the burning dynamics of polyethylene (PE) vs polypropylene (PP) pools fully melted at 380–410 °C on a hot plate with a controlled area and initial temperature. For PE, three burning patterns are observed and defined under different bottom boundary temperatures. When the boundary temperature is lower than the melting point of thermoplastic, burning Pattern I (near-limit flame) appears shortly and extinguishes quickly. Above the melting point of PE, the flame becomes stronger and can last for the longest period before quenching (Pattern II: transitional flame). PP does not have this transitional-flame stage due to a higher melting point and lower pyrolysis point. When the plastic pool temperature exceeds its flashpoint of about 300 °C (∼60 °C below its pyrolysis point), the flame becomes intense and quickly burns out the molten pool (Pattern III: intensive flame). The burning processes of molten thermoplastics show a clear difference from the burning of ethanol and paraffin wax. This study promotes the understanding of the melting and burning of plastics in real fire scenarios and helps quantify the hazards of dripping and flooring fires.

Enrofloxacin and Sulfamethoxazole Sorption on Carbonized Leonardite: Kinetics, Isotherms, Influential Effects, and Antibacterial Activity toward S. aureus ATCC 25923.

Excessive antibiotic use in veterinary applications has resulted in water contamination and potentially poses a serious threat to aquatic environments and human health. The objective of the current study was to quantify carbonized leonardite (cLND) adsorption capabilities to remove sulfamethoxazole (SMX)- and enrofloxacin (ENR)-contaminated water and to determine the microbial activity of ENR residuals on cLND following adsorption. The cLND samples prepared at 450 °C and 850 °C (cLND450 and cLND550, respectively) were evaluated for structural and physical characteristics and adsorption capabilities based on adsorption kinetics and isotherm studies. The low pyrolysis temperature of cLND resulted in a heterogeneous surface that was abundant in both hydrophobic and hydrophilic functional groups. SMX and ENR adsorption were best described using a pseudo-second-order rate expression. The SMX and ENR adsorption equilibrium data on cLND450 and cLND550 revealed their better compliance with a Langmuir isotherm than with four other models based on 2.3-fold higher values of qmENR than qmSMX. Under the presence of the environmental interference, the electrostatic interaction was the main contributing factor to the adsorption capability. Microbial activity experiments based on the growth of Staphylococcus aureus ATCC 25923 revealed that cLND could successfully adsorb and subsequently retain the adsorbed antibiotic on the cLND surface. This study demonstrated the potential of cLND550 as a suitable low-cost adsorbent for the highly efficient removal of antibiotics from water.

Physicochemical properties and pyrolysis behavior of petcoke with artificial neural network modeling

Petcoke is a byproduct of heavy crude oil refining at an enormous scale, and insights into the physicochemical properties, thermal degradation behavior, decomposition kinetics, and thermodynamic analysis of petcoke pyrolysis are crucial for the efficient design of pyrolysis reactor systems. In this study, proximate and ultimate analyses were performed, and petcoke was found to have a high fuel ratio with high carbon, high sulfur, and considerably low ash content, implying that it is a less reactive fuel. Advanced analytical techniques such as SEM, BET, FTIR, and petrography indicated that petcoke has a considerably low pore volume and predominantly inorganic graphitic carbon. Furthermore, thermogravimetric analysis was examined at four different heating rates of 10, 20, 30, and 40 K/min and petcoke exhibited a low pyrolysis performance, which was confirmed by the devolatilization index and pyrolytic parameters. The activation energies and frequency factors estimated by three model-free methods (DAEM, FWO, Friedman) were in the range of 221.6–235.9 kJ/mol and 1011–1012 s−1, respectively. In addition, thermodynamic analyses were examined and the thermal degradation behavior of petcoke pyrolysis was modeled using an artificial neural network; the NN-2-12-12-2 model with Tansig-Tansig transfer functions was found to be the best fit. This study enabled the identification of the fundamental characteristics of petcoke fuel, and these results provide useful information regarding the design, utilization, optimization, and limitations of petcoke pyrolysis systems.

Mechanism research on hydrogen production from catalytic pyrolysis of waste tire rubber

Waste tires are currently disposed of through various approaches such as landfill and incineration, which not only causes environmental pollution, but also lead to the wastage of resources. As an important type of solid waste, tire rubber has a high carbon-to-hydrogen ratio, which makes it a good material for hydrogen production from pyrolysis. In this study, molecular dynamics simulations combined with experimental methods are used to explore the mechanism of hydrogen production from the catalytic pyrolysis (CP) of waste tire rubber (WTR) over Ni, ZSM-5 and Ni/ZSM-5. The simulation results show that the three catalysts potentially promote the release of hydrogen radicals from monomers and facilitate attack by H· radicals to generate hydrogen. Compared with ZSM-5 and Ni, the Ni/ZSM-5 catalyst exerts better catalytic effects, leading to higher contents of produced H2 and hydrocarbons. In the low-temperature stage, the long chain cracks into monomer compounds, which mainly include isoprene, styrene, and 1,3-butadiene. Meanwhile, in the high-temperature stage, free radicals attack monomers to generate small molecules. The main gas products from the catalytic pyrolysis of waste tire rubber are hydrogen, methane, and ethylene. The use of all three catalysts leads to a low final catalytic pyrolysis temperature, high catalytic pyrolysis rate, and excellent catalytic effect. This work aims to provide a deeper understanding of the reaction thermodynamics and kinetics for the formation mechanisms of gaseous products, primarily hydrogen.

Synthesis of sustainable chemicals from waste tea powder and Polystyrene via Microwave-Assisted in-situ catalytic Co-Pyrolysis: Analysis of pyrolysis using experimental and modeling approaches

In the current study, catalytic co-pyrolysis was performed on waste tea powder (WTP) and polystyrene (PS) wastes to convert them into value-added products using KOH catalyst. The feed mixture influenced the heating rates (17–75 °C/min) and product formation. PS promoted the formation of oil and WTP enhanced the char formation. The maximum oil yield (80 wt%) was obtained at 15 g:5 g, and the maximum char yield (44 wt%) was achieved at 5 g:25 g (PS:WTP). The pyrolysis index (PI) increased with the increase in feedstock quantity. High PI was noticed at 25 g:5 g, and low PI was at 5 g:5 g (PS:WTP). Low energy consumption and low pyrolysis time enhanced the PI value. Significant interactions were noticed during co-pyrolysis. The obtained bio-oil was analyzed using GC–MS and a plausible reaction mechanism is presented. Catalyst and co-pyrolysis synergy promoted the formation of aliphatic and aromatic hydrocarbons by reducing the oxygenated products.

Pyrolysis-gasification of biomass using nickel modified catalysts: The effect of the catalyst regeneration on the product properties

In this work, agricultural biomass waste (maize) was used as raw material in a pyrolysis-gasification process with the presence of nickel-loaded zeolites, CaO and Al2O3. Henceforward, the reusability and the deteriorating effect of the catalysts are important to be analysed, therefore the catalysts were reused for ten regeneration cycles. During the measurements, the effect of temperature, catalysts and the regeneration cycles of catalysts were also investigated, as well as the components of the gaseous product. At first, the proper temperature was determined in the 1st (200–800 °C) and the 2nd (500–700°) reactor zone, where 400 °C and 700 °C, while for the regeneration 800 °C was chosen. Throughout the regeneration cycles in case of Ni/ZSM-5 lighter hydrocarbons was increased while that of the carbon monoxide and carbon dioxide was decreased. In the presence of Ni/CaO the amount of carbon dioxide decreased until the 3rd regeneration cycle, while carbon monoxide and hydrogen was decreased till the 10th cycle. Regarding the Ni/Al2O3, the amount of CO2 and CO was significantly decreased at each cycles, while in case of Ni/Clinoptilolite reduction was observed in hydrogen and carbon dioxide, however not only the amount of carbon monoxide but the syngas yield increased remarkably. Due to the mentioned results, the Ni/Clinoptilolite has an effective syngas enhancing and carbon dioxide capturing effect, even with low pyrolysis temperature.

Biochar and bio-oil fuel properties from nickel nanoparticles assisted pyrolysis of cassava peel

Direct biomass usage as a renewable fuel source and substitute for fossil fuels is discouraging due to high moisture, low energy density and low bulk density. Herein, thermogravimetric analysis (TGA) was conducted at various heating rates to determine peak decomposition temperatures for the dried cassava peels (DCP). The influence of pyrolysis temperature (300, 400, 500 and 600 °C) and heating rates (10, 20 and 30 °C/min) on the nickel nanoparticles catalyzed decomposition of DCP to produce biochar, bio-oil and biogas was investigated and characterized. The results revealed higher biochar (CBC) yield of 68.59 wt%, 62.55 wt% and 56.92 wt% at lower pyrolysis temperature of 300 °C for the different heating rates of 10, 20 and 30 °C/min. The higher carbon content of 52.39, 53.30 and 55.44 wt% was obtained at elevated temperature of 600 °C and heating rates of 10, 20 and 30 °C/min, respectively. At the pyrolysis temperature of 600 °C and heating rates of 10, 20 and 30 °C/min, the optimum yield of bio-oil (24.35, 17.69 and 18.16 wt%) and biogas (31.35, 42.03 and 46.12 wt%) were attained. A high heating value (HHV) of 28.70 MJ/kg was obtained for the biochar at 600 °C. Through the TGA, FTIR and HRSEM results, the thermal stability, hydrophobicity and structural changes of DCP and CBC samples were established. Similarly, the thermal stability of CBC samples increased with increasing pyrolysis temperature. Biochar with optimum fuel properties was produced at 600 °C due to the highest carbon content and high heating value (HHV). Improved kinematic viscosity (3.87 mm2/s) and density (0.850 g/cm3) were reported at the temperature of 300 °C and heating rate of 30 °C/min, while a higher pH (4.96), HHV (42.68 MJ/kg) and flash point (53.85 min) were presented by the bio-oil at the temperature of 600 °C and heating rate of 30 °C/min. Hence, DCP produced value-added biochar and bio-oil as renewable energy.

Fast peroxydisulfate oxidation of the antibiotic norfloxacin catalyzed by cyanobacterial biochar

Peroxydisulfate (PDS) is a common oxidant for organic contaminant remediation. PDS is typically activated by metal catalysts to generate reactive radicals. Unfortunately, as radicals are non-selective and metal catalysts may cause secondary contamination, alternative selective non-radical pathways and non-metal catalysts need attention. Here we investigated PDS oxidation of commonly detected antibiotic Norfloxacin (NOR) using cyanobacterial nitrogen rich biochars (CBs) as catalysts. NOR was fully degraded by CB pyrolysed at 950 °C (CB950) within 120 min. CB950 caused threefold faster degradation than low pyrolysis temperature (PT) CBs and achieved a maximum surface area normalized rate constant of 4.38 × 10−2 min−1 m−2 L compared to widely used metal catalysts. CB950 maintained full reactivity after four repeated uses. High defluorination (82%) and mineralization (>82%) were observed for CB950/PDS. CBs were active over a broad pH range (3−10), but with twice as high rates under alkaline compared with neutral conditions. NOR is degraded by organic, •OH and SO4•− radicals in low PT CBs/PDS systems, where the presence of MnII promotes radical generation. Electron transfer reactions with radicals supplemented dominate high PT CBs/PDS systems. This study demonstrates high PT biochars from algal bloom biomass may find use as catalysts for organic contaminant oxidation.