It is promising strategy in recent years to design and prepare metal/carbon-based functional materials with different structures using metal-organic framework (MOF) composite precursors. Hollow ...multi-shell nanomaterials with large specific surface area and abundant active sites have become high energy conversion catalytic materials. The first prepared the transition metal chalcogenides of the nano-structure of the hollow core-shell and then grew the zeolitic imidazolate frameworks-67 in situ on the nanoparticles of core-shell. Then, through pyrolysis to obtain multilayer core-shell particles with porous outer shell of Co/N-doped carbon skeleton. WS.sub.2@Co.sub.9S.sub.8-2@N/C is applied in dye-sensitized solar cells as counter electrode material, showing good catalytic performance for I.sup.-/I.sub.3.sup.- redox reaction, and the power conversion efficiency is as high as 9.85%. As the electrode material of oxygen reduction reaction, the half-wave potential can reach E.sub.1/2 = 0.855 V. For oxygen evolution reaction tests, there is a low overvoltage of 1.757 V when the current density is 10 mV cm.sup.-1. In addition, the MOF can be grown in situ in different nanostructures, which can gain its advantages as a multifunctional material in terms of structure and multi-element, and this method can be applied to the fabricate of composite materials with different structures.
The impedance matching is a very important part to influence materials' microwave absorption performance. However, a way to further discuss the impedance matching is still weak. We build a novel ...dielectric-magnetic impedance matching (DMIM) model to analyze the real part and imaginary part of materials' impedance matching. To verify the practicality of the DMIM model, using MIL-100(Fe) as precursor, a series of Fe.sub.xNi.sub.1-x@C are synthesized via one-step pyrolysis by controlling the samples' Fe-Ni ratio, changing their dielectric loss tangent and magnetic loss tangent and successfully regulating their impedance matching to optimize microwave absorption properties. In addition, the minimum reflection loss for MOF-derived Fe.sub.0.8Ni.sub.0.2@C can arrive at -71.3 dB at 10.3 GHz with a thickness of 3.1 mm, and the effective absorption bandwidth is 5.3 GHz. And combining with the RLGC equivalent circuit model to further indicate the Fe.sub.xNi.sub.1-x@C's energy loss mechanism. The method of using DMIM model and RLGC model to discuss materials' impedance matching and energy loss mechanism paves a new way to fabricate high-performance microwave materials with balanced electromagnetic distribution and further reveal the materials' microwave absorbing mechanism. Graphic abstract
In the process of pyrolyzing waste plastics, the generation of Clsub.2 gas can pose a problem. During the pyrolysis processing, incomplete combustion of organic compounds containing chlorine can lead ...to the formation of toxic chemicals, which can cause issues in subsequent processing stages. Therefore, an adsorbent plays an important role in removing Clsub.2 in the dechlorination process, and alkaline adsorbents and metal oxides are generally used. Waste red mud is composed of Fe metal oxide and alkaline components, so it is intended to be used as a Clsub.2 adsorbent. The Clsub.2 removal ability of red mud with different redox status of iron oxides was assessed. Hydrogen treatment was performed at various temperatures to control the reduction potential of the Fe in the metal oxides, and phase changes in the Fe oxide component of red mud were confirmed. In the case of red mud hydrogenated at 700 °C, most of the Fesub.2Osub.3 structure could be converted to the Fesub.3Osub.4 structure, and the Fesub.3Osub.4 structure showed superior results in Clsub.2 adsorption compared to the Fesub.2Osub.3 structure. As a result, red mud at an Hsub.2 treatment temperature of 700 °C showed about three times higher Clsub.2 adsorption compared to red mud without Hsub.2 treatment.
Energy from biomass is increasingly gaining attention amidst the environmental challenges of coal and fossil fuels. This study investigated the effects of inert gases (Nsub.2, COsub.2, and ...Nsub.2/COsub.2) on intermediate pyrolysis and product properties from Bambara Groundnut Shells (BGS) (shells from an underutilized crop, which has high nutritional values). Nsub.2/COsub.2 atmosphere roughly represents flue gas. The results showed that the inert gases did not significantly affect the yields of bio-oil, biochar, and syngas. The pH of bio-oil ranged from 5.2–5.8, indicating the minimum presence of acids in bio-oil. The CHNS analysis showed that all bio-oil and biochar had their carbon content within 50.04–60.49 wt.%. The FESEM resulted in a wide range of pore sizes in biochar produced in an Nsub.2/COsub.2 atmosphere. The GC-MS (Gas Chromatography-Mass Spectrometry) analysis revealed the presence of compounds which can be categorized as alkene, acid, benzene derivatives, ketone, phenol derivatives, alcohol, aldehyde, alkyl, and ester. However, the presence of Nsub.2/COsub.2 gas favored alcohol and phenol production significantly.
Engineering of oxygen vacancies (Vo) in nanomaterials allows diligent control of their physicochemical properties. SrTiOsub.3 possesses the typical ABOsub.3 structure and has attracted considerable ...attention among the titanates due to its chemical stability and its high conduction band energy. This has resulted in its extensive use in photocatalytic energy-related processes, among others. Herein, we introduce the use of Flame Spray Pyrolysis (FSP); an industrial and scalable process to produce Vo-rich SrTiOsub.3 perovskites. We present two types of Anoxic Flame Spray Pyrolysis (A-FSP) technologies using CHsub.4 gas as a reducing source: Radial A-FSP (RA-FSP); and Axial A-FSP (AA-FSP). These are used for the control engineering of oxygen vacancies in the SrTiOsub.3-x nanolattice. Based on X-ray photoelectron spectroscopy, Raman and thermogravimetry-differential thermal analysis, we discuss the role and the amount of the Vos in the so-produced nano-SrTiOsub.3-x, correlating the properties of the nanolattice and energy-band structure of the SrTiOsub.3-x. The present work further corroborates the versatility of FSP as a synthetic process and the potential future application of this process to engineer photocatalysts with oxygen vacancies in quantities that can be measured in kilograms.
Nowadays, the environmental challenges associated with plastics are becoming increasingly prominent, making the exploitation of alternatives to landfill disposal a pressing concern. Particularly, ...polyvinyl chloride (PVC), characterized by its high chlorine content, poses a major environmental risk during degradation. Furthermore, PVC recycling and recovery present considerable challenges. This study aims to optimize the PVC pyrolysis valorization process to produce effective adsorbents for removing contaminants from gaseous effluents, especially COsub.2. For this purpose, PVC waste was pyrolyzed under varied conditions, and the resulting solid fraction was subjected to a series of chemical and physical activations by means of hydroxides (NaOH and KOH) and nitrogen. Characterization of the PVC-based activated carbons was carried out using surface morphology (SEM), Nsub.2 adsorption/desorption, elemental analysis, and FTIR, and their capacity to capture COsub.2 was assessed. Finally, neuro-fuzzy models were developed for the optimization of the valorization technique. The resulting activated carbons exhibited excellent COsub.2 adsorption capabilities, particularly those activated with KOH. Optimal activation conditions include activations at 840 °C with NaOH at a ratio of 0.66 and at 760 °C using either NaOH or KOH with ratios below 0.4. Activations under these experimental conditions resulted in a significant increase in the adsorption capacity, of up to 25%, in the resulting samples.
This paper reports on the synthesis and characterization of Lasub.2Osub.3:Eusup.3+ luminescent aerogels fabricated by the sol–gel method and the supercritical drying technique. The % mol ...concentration of the Eusup.3+ ion was varied to study the effects on the luminescent properties of the aerogels. XRD and TEM analysis showed that the Lasub.2Osub.3:Eusup.3+ aerogels exhibited a semi-crystalline behavior regardless of whether the concentration of europium was increased. SEM micrographs revealed a porous structure in the aerogels, which were composed of quasi-spherical nanoparticles that were interconnected and formed coral-shaped agglomerates. Photoluminescence spectroscopy characterization showed that the aerogels had an infrared emission located at λ = 793 nm, and the maximum photoluminescence emission intensity was observed for the aerogel with 50% Eusup.3+. The results demonstrate that, without heat treatment, it is possible to manufacture luminescent aerogels of rare-earth oxides that can be used in opto-electronic devices.
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•Pyrolysis of individual biomass components required less heat input than pyrolysis of biomass.•Entropy generation is lower in pyrolysis of lignin than cellulose and ...hemicellulose.•Exergy destruction is higher in pyrolysis of biomass compared to pyrolysis of pseudo-components.•Bio-oil represents the stream with the lowest anergy in pyrolysis.
Energy and exergy analyses were performed to evaluate the pyrolysis of the lignocellulosic biomasses, beech wood and flax shives, and the pyrolysis of biomass principal compounds (cellulose, hemicelluloses and lignin) as well. The reaction took place in a semi-continuous reactor at 500 °C within an intermediary pyrolysis regime. Lignin showed the lowest heat for pyrolysis, with 0.86 MJ/kgRaw material, followed by cellulose (1.21 MJ/kgRaw material) and hemicellulose (1.43 MJ/kgRaw material). The heat for pyrolysis for the pseudo-components was inferior to those obtained for the biomasses. Beech wood heat for pyrolysis was 1.97 MJ/kgBiomass and that for flax shives was 2.2 MJ/kgBiomass. The thermal behavior of the biomasses was similar to that of hemicellulose and cellulose, as the bio-oils seemed to have closest energetic and exergetic distribution of chemical families as compared to the lignin bio-oil. For all pyrolysis tests, bio-oil represented the stream with lowest anergy. As values were between 0.08 and 0.57 MJ/kgBio-oil. Pyrolysis of the pseudo-components showed lower exergy destruction rate than pyrolysis of the biomasses; this can be a result of the competition of thermal reactions between cellulose, hemicellulose and lignin within the biomass during pyrolysis. Meanwhile, less exergy was destroyed in flax shives pyrolysis (2.00 MJ/kgBiomass) than beech wood pyrolysis (2.1 MJ/kgBiomass).
The goal of this research work was to evaluate a novel iron-alumina catalyst for methane and ethane pyrolysis with high conversion rates to H2 with a long life time to address two major issues ...reported with previous catalysts. Fluidized bed tests demonstrated continuous hydrogen production while collecting carbon containing fines. During the 230 h fluid bed test the methane conversion rate to hydrogen at 700 °C remained above 80% for 160 h while creating valuable nano carbons. Similarly high catalyst lifetimes with high methane conversions have not been reported before. Ethane was more active than methane for pyrolysis with 100% conversion to H2. Transmission electron microscopy and Raman analysis of the carbon showed single and multiwall nanotubes and conglomerate nano-fibers. Ethane did not impact the allotrope of carbon formed. TGA was used to create a data array that was used for kinetic analysis and reaction model parametric regressions. Ethane had a higher rate of pyrolysis that was 2.3–2.8 times that of methane. Ethane pyrolysis was found to be more sensitive to temperature with a higher activation energy of 62 kJ/mol as compared to methane at 43 kJ/mol. The frequency factor, Ai, was significantly higher for ethane at 0.73 kmol/m3-sec/N/m2n compared to 0.03 for methane on the same basis. Both gases had a functional partial pressure order dependence of ∼0.6 based on the regression analysis.
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•Novel Fe based catalysts showed 80% CH4 conversion to H2 for 160 h.•Ethane conversion was 100%.•Continuous H2 production demonstrated in fluid bed tests.•Higher ethane conversion rates than that with methane.•Reaction rate models were developed for methane and ethane pyrolysis.
•Analyzing the recent developments in pyrolysis processes of microalgae.•Mechanism of the various types of pyrolysis was summarized.•Biochemical composition was discussed in detail.•Microwave ...assisted pyrolysis has achieved more significance than other process.•Quality of the bio-oil in catalytic pyrolysis was higher than thermal pyrolysis.
Algae become reasonable feedstock in recent times for biofuel production as they are environmentally benign, sustainable and renewable biomass. Biofuels are produced from algal biomass by chemical, biochemical, and thermochemical methods. Among the thermochemical techniques, pyrolysis is a well-known method involving high temperature and high pressure to produce biochar and bio-oil from numerous algal biomasses. Therefore, this review was undertaken to collate and discuss different pyrolytic processes employed for the conversion of algal biomass into biochar and bio-oil production. At the outset, different pyrolysis methods slow pyrolysis, fast/flash pyrolysis, catalytic pyrolysis, microwave assisted pyrolysis and hydropyrolysis operated for the conversion of various microalgae and cyanobacteria into biochar and bio-oil were reviewed using copious literature. Further, challenges arisen out of using above-said pyrolysis methods were critically highlighted to pave the way to choose an appropriate pyrolysis method for obtaining desirable quantity and quality of bio-oil from algae.
