Pyrolysis Step Research Articles

Biomass derived functional carbon from Sargassum Wightii seaweed for supercapacitors

In this present work, microporous functional carbon is prepared by a single step pyrolysis method of dried SargassumWightiiseaweeds (SW) as crushed powder without activation and tested for supercapacitors. Although the complete study presented here on seaweeds of SargassumWightii(SW), the synthesis technique is standard and relevant to most forms of dried biomass. The morphological studies were characterized by X-ray diffraction (XRD), Energy dispersive X-ray spectroscopy (EDS), Raman spectroscopy (RAMAN), field emission scanning microscopy (FE-SEM) and Fourier-transform infrared spectroscopy (FTIR). The behaviour of the functional carbon were performed by using cyclic voltammetry (CV), galvanostatic charge and discharge (CD) and Impedance analysis. In aqueous electrolyte (1M H2SO4), by using three-electrode system shows highest capacitance of 354 F/g. Furthermore, it was observed that the carbonized temperature has significant role in the electrochemical performance, as the carbonized sample at 700°C showed best activity compared to the samples carbonized at 800°C and 900°C without any external activation. The electrochemical act obviously shows that the carbon produced from dried SW seaweeds can be used as a favourable material for electrodes in the application of supercapacitors.

Understanding Pyrolysis of PGM-Free Electrocatalysts with X-Ray Computed Tomography

Atomically dispersed Fe-N-C electrocatalyst is the emerging advanced type of PGM-free catalyst. Its activity arises from a multitude of active sites, often viewed as co-catalytic (bifunctional sites), such as atomically-dispersed iron in nitrogen coordination (FeNx) and pyridinic and pyrrolic nitrogen moieties in graphene structures. The synthesis of Fe-N-C electrocatalysts involves a pyrolysis step, for which physical and chemical transformations are not well understood. Various ramps and temperature holds are currently used to evaporate precursors and solvents and to achieve the electrocatalyst’s high electric conductivity. An additional pyrolysis step, termed second pyrolysis, is sometimes used. Recipes exist with the pyrolysis of various precursors to arrive at catalyst that contains a high content of nitrogen. Here, Fe(NO3)3 .9 H2O and an aromatic amine charge-transfer organic salt, nicarbazin, was used. Custom pyrolysis furnace built by the Advanced Light Source’s (ALS) 8.3.2 beamline scientists was used that was capable of having gas circulation, high temperature and, at the same time, a rotating stage for x-ray computed tomography (CT) imaging. After ball-milling, the sample was placed on a ceramic stage of the vertical furnace with a circulating gas mixture of nitrogen and 7 % hydrogen. The catalyst was inserted at 525°C and then furnace temperature was increased; first to 900°C in 12 min (31.25 °C/min) and then to 975°C in 8 min (9.375 °C/min). After a 45 min hold time, the catalyst was removed from the furnace. Seven X-ray CT scans were performed during this pyrolysis process. This is the first study to use micro X-ray CT to observe the morphological changes of a catalyst powder during a pyrolysis process. Figure 1 shows the schematic of the stage, the quartz tube used to seal the gases and the ceramic stage for the catalyst placement. A photograph of our mounted catalyst within the pyrolysis chamber on the rotating stage is shown by Figure 1b and a temperature profile by Figure 1c. We have found that most of the changes in the catalyst morphology happen during the temperature ramp to 975oC and during cool down. The temperature hold at 975°C did not result in significant powder morphological changes. A follow-up study was conducted where the temperature ramp was studied in more detail with X-ray CT scans taken every 100°C. Furthermore, a second pyrolysis study was conducted where morphological changes were not observed. Figure 1. a) Schematic of pyrolysis stage and gases circulation, b) a photograph of our sample mounted within the pyrolysis chamber at 8.3.2 ALS during imaging, c) the temperature ramp during pyrolysis and d) the evolution of catalyst morphology during temperature ramp. Figure 1

Effect of Carbon Support on Fe-N3/C Model Active Site for the Oxygen Reduction Reaction

Non-precious metal catalysts for the oxygen reduction reaction (ORR) are of great interest for fuel cell technology due to their low cost and wide availability of materials. Development of these catalysts has been a constantly growing area. However, there have been very few literature reports that provide insights into the precise nature of the structure and geometry of the catalytically active sites formed in these materials. In the current literature, the most commonly proposed catalytically active site(s) for ORR corresponds to Fe-N2+2/C geometry. This is typically produced through a high temperature pyrolysis step to obtain this desired configuration in the active sites[1]. However, the pyrolysis step is very disadvantageous due to the production of a distribution of nitrogen functional groups on the surface which can negatively affect the activity of the catalyst, since only nitrogen functionalities with specified geometry are considered to be the most active for ORR[2,3]. As well, high temperature treatments increase the cost of production, and can be quite energy demanding. Thus, high-temperature treatment makes it difficult to design a surface rich in a specific active site for the desired application. The work presented here demonstrates a model system for a non-precious metal catalyst for the ORR achieved by covalently functionalizing a conventional carbon support with a nitrogen-rich ligand. The terpyridine ligand geometry allows the formation of well-defined active catalytic sites when covalently attaching an N3/C functionality to the carbon surface, leaving exposed the most active sites for the ORR. Room temperature metal-ligand coordination with Fe results in desired Fe-N3/C moieties on the surface. We demonstrate that this system can be prepared using mild reaction conditions and does not require high temperature treatment for improved activity, in fact heat treatment to this system was detrimental to the activity. The Fe-N3/C support was subjected to electrochemical studies in both acidic and basic aqueous media and demonstrates the potential of this system to be used as a model for an Fe-N3/C active site for ORR.

Energy characteristics of the char obtained by two steps pyrolysis of chicken manure

The thermal treatment of chicken manure is an ecological alternative of neutralizing this kind of waste with energy recovery. In this regard, a two-stage pyrolysis process was chosen, the first stage having the purpose of preheating and moisture elimination. The drying process up to the starting point of volatile matter release, about 200-250°C was taken into consideration. As a result of the moisture elimination in the first step of the pyrolysis process, a gas fuel riched in CO, CH4, H2 will be obtained. The experimental determinations consisted in the proximate and ultimate analysis of the initial residue and tests of the pyrolysis process in a pilot plant that allows the pyrolysis of a quantity of waste in range of 40-200g. A sample of a 140 g was subjected to the pyrolysis process at 500°C and the char (an organic, solid, consistent and odourless product) was obtained. The carbon (C), nitrogen (N), hydrogen (H) and sulphur (S) contents of the final product of pyrolysis were determined by a Costech 4120 Elemental Analyser that allows us to calculate the Lower Heating Value (LHV) of the char. For the evaluation of the energy potential, a theoretical balance of the energy consumption in the process of pyrolysis and the energy developed by combustion of the char, has been made. This theoretical balance was verified by determining the energy developed by combustion of char based on the composition determined in the laboratory. The laboratory results confirmed the existence of an energy potential of the pyrolysis product, which offers a technological alternative.

Pyrolysis-induced shrinking of three-dimensional structures fabricated by two-photon polymerization: experiment and theoretical model

The introduction of two-photon polymerization (TPP) into the area of Carbon Micro Electromechanical Systems (C-MEMS) has enabled the fabrication of three-dimensional glassy carbon nanostructures with geometries previously unattainable through conventional UV lithography. Pyrolysis of TPP structures conveys a characteristic reduction of feature size—one that should be properly estimated in order to produce carbon microdevices with accuracy. In this work, we studied the volumetric shrinkage of TPP-derived microwires upon pyrolysis at 900 °C. Through this process, photoresist microwires thermally decompose and shrink by as much as 75%, resulting in glassy carbon nanowires with linewidths between 300 and 550 nm. Even after the thermal decomposition induced by the pyrolysis step, the linewidth of the carbon nanowires was found to be dependent on the TPP exposure parameters. We have also found that the thermal stress induced during the pyrolysis step not only results in axial elongation of the nanowires, but also in buckling in the case of slender carbon nanowires (for aspect ratios greater than 30). Furthermore, we show that the calculated residual mass fraction that remains after pyrolysis depends on the characteristic dimensions of the photoresist microwires, a trend that is consistent with several works found in the literature. This phenomenon is explained through a semi-empirical model that estimates the feature size of the carbon structures, serving as a simple guideline for shrinkage evaluation in other designs.

Efficient removal of oxytetracycline from aqueous solution using magnetic montmorillonite-biochar composite prepared by one step pyrolysis

Three adsorbents, namely, original biochar (CLB), montmorillonite (MMT)-biochar composite (MBC), and magnetic MMT-biochar composite (MMBC) were successfully fabricated by one step pyrolysis of original cauliflower (Brassica oleracea L.) leaves, mixture of cauliflower leaves and MMT, and FeCl3-laden mixture of cauliflower leaves and MMT under limited oxygen atmosphere, respectively. The characterizations of samples indicated that substantial MMT mineral particles and Fe3O4 nanoparticle were dispersed on the surface of MMBC. Due to the introduction of Fe3O4, MMBC performed excellent magnetization property. The adsorption experiments of oxytetracycline (OTC) indicated that the maximum adsorption ability of MMBC was 58.85 mg·g−1, which was 2.63 times as large as CLB, also, larger than that of MBC. Meanwhile, pH, ionic strength, and humic acid (HA) performed slight effects for adsorption of OTC on MMBC. In addition, MMBC still removed 92% OTC after five regeneration cycles. Finally, primary mechanisms of OTC adsorption onto MMBC were attributed to hydrogen bonding and π-π reaction, and ion exchange reaction was considered to exist. Meanwhile, functional groups including Si-O-Al, Si-O-Si, Si-O, and Fe3O4 nanoparticles would provide extra binding sites for OTC adsorption. Therefore, MMBC had an obvious potential to apply into water purification as a reliable, low-cost, and environmentally friendly adsorbent.

Sustainable Magnetic Materials (from Chitosan and Municipal Biowaste) for the Removal of Diclofenac from Water.

The photodegradation of an aqueous solution of diclofenac (DCF) has been attempted in the presence of hydrogen peroxide and organic/inorganic hybrid magnetic materials under simulated and real solar light. The hybrid magnetic materials have been prepared via coprecipitation synthesis starting from iron(II) and iron(III) inorganic salts in the presence of bioderived organic products (i.e., chitosan or bio-based substances isolated from commercially available composted urban biowastes) acting as stabilizers of the iron-containing phase. In addition to the as prepared hybrid materials, the corresponding materials obtained after a pyrolytic step at low temperature (550 °C) have been tested. The obtained results evidenced the capability of the materials to activate hydrogen peroxide at mild pH promoting DCF (photo) degradation. All the materials feature also as adsorbents since a decrease of DCF is observed also when working in the dark and in the absence of hydrogen peroxide.

Two-step catalytic co-pyrolysis of walnut shell and LDPE for aromatic-rich oil

A novel two-step catalytic co-pyrolysis (TSCCP) process is proposed through coupling advantages of conventional two-step catalytic pyrolysis (TSCP) and one-step catalytic co-pyrolysis (OSCCP) for producing aromatic-rich oil using walnut shell (WNS) and LDPE as feedstock. Co-pyrolysis of three WNS components (hemicellulose, cellulose and lignin) with LDPE are performed to validate the necessity and rationality of TSCCP. And effects of first step pyrolysis temperature (T1) and residence time (Rt1) on product distributions of TSCCP are investigated. When T1 and Rt1 are 550 °C and 7.5 s respectively, the oil yield is increased by 59.1% and 15.7% respectively compared with that of conventional TSCP and OSCCP. The selectivity toward aromatics is as high as 82.5%, and the selectivity of oxygenates is reduced to less than 1%. The excellent results of TSCCP are attributed to preventing secondary reactions led by higher temperature for hemicellulose and cellulose components, the enhanced conversion due to activation effect from lignin component, and the synergetic effect between WNS-derived oxygenates and LDPE-derived hydrocarbons.

Ex Situ Catalytic Pyrolysis of a Mixture of Polyvinyl Chloride and Cellulose Using Calcium Oxide for HCl Adsorption and Catalytic Reforming of the Pyrolysis Products

In the context of chemical recycling of mixed plastics and paper, multitemperature step pyrolysis has shown good potential for the separation of oxygenated products from hydrocarbons. Here, we repo ...

Recycling of Commercial E-glass Reinforced Thermoset Composites via Two Temperature Step Pyrolysis to Improve Recovered Fiber Tensile Strength and Failure Strain

Economic and regulatory pressures on the global composites industry have encouraged the research and development of technology for the recycling of fiber reinforced polymer composites. Although significant advancements have been made in the recycling of carbon fiber composites, more progress is needed in the recovery of glass fibers, which make up the overwhelming volume of the composites market. In this study, wind turbine blades and automotive sheet moulding compound (SMC) were subjected to a two temperature step pyrolysis. This multistep process yielded improvements in the recovered E-glass fiber’s tensile strength, by as much as 19%, and strain to failure, by as much as 43%, over a single high temperature step pyrolysis. Despite these gains, pre-pyrolysis fiber measurements indicate that pre-existing damage may inherently limit the quality of glass fiber recoverable from pyrolysis without any post processing.

Differences in Formation and Oxidation of Colombian Coal Chars in Air and Oxy-fuel Atmospheres

The increasing interest towards more efficient and clean technologies, specially paying attention to CO2 neutral processes is encouraging the investigation of coal thermochemical conversion under oxy-fuel atmospheres (i.e. without N2). The process offers many advantages such as easy separation of the CO2 produced and low NOX/SOX emissions. While coal conversion in air is already well understood, full understanding of the influences of CO2-rich atmospheres is still required. A series of experiments in thermogravimetric analyser, drop-tube reactor and flat-flame burner were performed using a mid-range bituminous coal (Colombian coal) to understand the differences in the chars obtained after the pyrolysis step. Comparing the pyrolysis in N2 and CO2 atmospheres, significant differences were observed in the resulting chemical (composition) and physical properties of the chars, whereas mass loss was very similar for short residence times (< 130 ms). Afterwards, the chars obtained were submitted to oxidation and gasification, under several different operating conditions, in order to evaluate the difference in reactivity of these chars. Chars obtained under CO2 atmospheres revealed a lower reactivity, despite their higher surface area. These aspects cannot be explained and captured by a model which does not focus on some important details. In this paper, the results obtained in these experiments are summarized and discussed on the point of view of the POLIMI modelling approach for thermochemical conversion of solids. This model offers several advantages, such as being flexible to improvements, requiring simple experimental data of the fuel and offers an all-in-one solution for describing the kinetics of the whole process. The developments accounted for a wide range of experimental data, which allowed its calibration for several fuels, mostly in air combustion. It was first developed to describe the pyrolysis step, and later char oxidation/gasification was included in a simplified approach. The detailed mechanism of homogeneous gas phase reactions of the volatiles is also coupled. In order to extend the predictive capabilities of the model for oxy-fuel conditions, dedicated experiments must be considered for future improvements. In this work these missing effects are discussed, identifying the main necessary improvements, allowing this model to be extended and applied also for the designing of reactors that use oxy-fuel technologies.

Highly Active, High Specific Surface Area Fe/C/N ORR Electrocatalyst from Liquid Precursors by Combination of CO2 Laser Pyrolysis and Single NH3 Thermal Post-Treatment

This paper reports original results on the synthesis and characterization of Fe/C/N ORR electrocatalysts obtained by a combination of CO2 laser pyrolysis and thermal post-treatment. The precursor liquid media, consisting in a 14 g·L−1 iron III acetylacetonate solution in toluene, was aerosolized and then exposed to a CO2 laser beam for pyrolysis in continuous flow. Ammonia was used in the pyrolysis process, both as the laser wavelength absorbing gas (i.e., energy transfer agent) and as the sole source of nitrogen. After the laser pyrolysis step, the material was submitted to thermal post-treatment under argon on the one hand, and ammonia on another hand. The three materials—one as-prepared, one thermally treated under argon, and one thermally treated under ammonia—were characterized, in particular, through specific surface area determination, XPS analysis, and ORR measurement. It was found that both kinds of thermal treatment significantly improved the ORR performances, which were evaluated on porous electrodes. Indeed, while the as-prepared material showed an ORR onset potential at ≈790 mV vs. the standard hydrogen electrode (SHE) in HClO4 1M, the argon treatment increased the latter to ≈820 mV, and the ammonia treatment led to a very high value of ≈910 mV. Selectivities of 3.65 and 3.93 were measured for the argon and ammonia treated materials, respectively. The outstanding ORR performance resulting from the ammonia treatment is probably related to the very high BET specific surface area measured at 1130 m2·g−1, which was notably obtained without using any templating or sacrificial component in the precursor media.

Ashes to ashes: Characterization of organic matter in Andosols along a 3400 m elevation transect at Mount Kilimanjaro using analytical pyrolysis

Tropical mountain ecosystems cover a broad variety of climatic and vegetation zones and are global hotspots of biodiversity. These ecosystems are severely threatened by climate and land-use change, which also strongly affect soil properties. Mt. Kilimanjaro, with its large elevation gradient and relatively homogeneous geology of volcanic rocks and ashes, provides a unique opportunity to study and interpret soil organic matter (SOM) responses to climatic changes.Our objectives were to identify key SOM compounds in six elevation zones (covering ecosystems from tropical dry-lowland, through montane forest, up to alpine heathlands) that are affected by the climatic changes along a 3400 m transect, and to relate these SOM changes to ecosystem specific characteristics. The SOM composition in four topsoils (0–10 cm) samples per ecosystem was characterized by analytical double-shot pyrolysis-gas chromatography–mass spectrometry (Py-GC/MS). Evolving-gas analysis-mass spectrometry (EGA-MS) was used to quantitatively compare the thermal desorption (first shot: <280 °C) and pyrolysis step (second shot: 280–600 °C).The percentage of thermally desorbed compounds increased 10 fold from lowland (<900 m) to mountain forest soils (>2000 m), followed by a 40% decrease in alpine ecosystems (>4000 m). Alkanes/-enes/-ols contributed between 4% and 30% to the identified SOM composition, with a maximum at mid elevation (2120 m). Fatty acids and fatty acid esters contributed with <3% to SOM composition and decreased to a minimum of <1% at Podocarpus forest soils (2900 m), followed by a re-increase at higher elevation. The percentage of lignin-derived compounds followed a similar pattern but also responded to reduced woody inputs above the tree line.Two main factors that seem to affect SOM quality and composition at Mt. Kilimanjaro were: 1) the rate and composition of organic matter inputs that in turn are controlled by climatic characteristics and the vegetation type and 2) the decomposition rate and efficiency, mainly controlled by soil pH, temperature and water availability. High forest productivity at mid elevations (2200 m) leads to high amounts of volatile compounds and increases stable SOM pools. The overall carbon accumulation in Andosols of Mt. Kilimanjaro is linked to the percentage of bound lipids (mainly alkanes, alkenes and alcohols), while site specific input patterns (e.g. vegetation or wild fires) are strongly reflected by sterols, lignin derived compounds or polycyclic aromatic compounds in SOM.

Biomass catalytic gasification performance over unsupported Ni‐Ce catalyst for high‐yield hydrogen production

AbstractCatalytic gasification of a residual biomass, obtained from yellow horn (YH) (Xanthoceras sorbifolia Bunge), an energy crop, was conducted to obtain a fuel gas rich in hydrogen. Unsupported nickel‐based catalyst modified with cerium was developed, characterized, and used in the advanced catalytic gasification of this residual biomass, using H2O + CO2 as the gasifying agent. Tests were performed in a thermobalance coupled to a mass spectrometer to identify the different steps involved in the gasification process and to correlate them with the estimated kinetic parameters. The sequential processes identified were: dehydration‐devolatilization, pyrolysis and gasification. The main pyrolysis step presented a calculated activation energy value of 102 kJ mol−1. A positive effect was observed for the catalyst in the syngas obtained. A synergistic effect of CO2 and H2O used as gasifying agents was found in the gas yield. Hydrogen production was promoted by several reforming and cracking reactions, aided by CeO2‐NiO catalyst able to co‐activate H2O + CO2. © 2019 Society of Chemical Industry and John Wiley &amp; Sons, Ltd

Synthesis of carbon nanospheres and piezoresistive study of carbon nanospheres-PEDOT:PSS nanocomposite flexible thin film for strain sensing applications

Microporous carbon nanospheres were synthesized using the single step pyrolysis method with oil palm leaves as a precursor. Non-hazardous bio-wastes from oil palm leaves were used for pyrolysis which was carried out at 700 °C in the nitrogen atmosphere. Nanocomposites consisting of different concentrations of carbon nanospheres(0.025 wt%, 0.05 wt%, 0.075 wt%, 0.1 wt%) and poly(3, 4-ethylenedioxythiophene) polymerized with poly(4-styrenesulfonate) polymer were prepared and were spin coated on flexible polyethylene terephthalate substrates to form nanocomposite thin films. These nanocomposite thin films were characterized for their nanostructure and elemental composition. The films were subjected to incremental strain from 0 to 6% at the speed of 0.2 mm min−1 and subsequently evaluated for their piezoresistive response. The carbon nanospheres-poly(3, 4-ethylenedioxythiophene) poly(4-styrenesulfonate) thin film with 0.05 wt% of carbon nanospheres(which is the wt% of carbon nanospheres close to the percolation threshold) in poly(3, 4-ethylene dioxythiophene) poly(4-styrene sulfonate) exhibited highest gauge factor of 34.57 with correlation coefficient 0.869 96 at 6% strain and the highest conductivity of 39.27 S m−1 for 0.1 wt% of carbon nanospheres was achieved. Hence, the fabricated thin film was found to be suitable in piezoresistive flexible strain sensing applications.

Bulk synthesis of graphene nanosheets from plastic waste: An invincible method of solid waste management for better tomorrow

Waste plastic management and converting it into value added products is one of the greatest challenges before the scientific community. The present work reports a cost effective, environment friendly and mass production capable method for upcycling of solid plastic waste into value added product (graphene). A two step pyrolysis processes i.e. firstly at 400 °C in presence of nanoclay followed by at 750 °C under nitrogen atmosphere was performed to obtain a black charged residue. Raman spectroscopy was performed on the obtained residue, where the observed D and G bands at 1342 cm−1 and 1594 cm−1, respectively, confirm the synthesis of graphene nano sheets. In addition, a broad 2D band at 2790 cm−1 confirm the presence of few layer graphene nano sheets. The obtained graphene nanosheets were also confirmed through the computational data by Gaussian09, where the peaks at 1379 cm−1 and 1596 cm−1 for D and G band, respectively, make a good agreement with experimental data. TEM, FT-IR and EDX spectroscopy were also performed to confirm the synthesis of graphene nanosheets including the functional group identification and quantitative analysis for elements, respectively.

Torrefaction of Various Biomass Feedstocks and Its Impact on the Reduction of Tar Produced during Pyrolysis

The aim of this study is to investigate the reduction of tar produced during biomass pyrolysis by torrefaction pretreatment. In this study, various biomass feedstocks (pine, ash wood, miscanthus, and wheat straw) with different particle sizes were torrefied at 280 °C. The results indicated that both particle size and biomass composition have a significant effect on the yield and properties of the torrefied products. With increasing particle size, the yield of solid product increased, while the yield of condensable liquid and noncondensable gases decreased. The raw biomasses and torrefied biomasses were then subjected to pyrolysis at 500 °C. The results clearly showed that torrefaction had a significant effect on the yield and composition of tar generated during subsequent pyrolysis. For all biomasses, the tar yields of biomasses after torrefaction were 42–62% lower compared to direct pyrolysis of raw biomasses. However, when considering the condensable liquid produced combining torrefaction and pyrolysis, the total yield of condensable liquid produced decreased 3–12% compared to the direct pyrolysis. This suggests that not only some volatiles were released during the torrefaction process, but the thermal pretreatment also transformed the biomass structure to less favor tar production in subsequent pyrolysis step.

Detailed structural elucidation of different lignocellulosic biomass types using optimized temperature and time profiles in fractionated Py-GC/MS

Fractionated pyrolysis coupled to gas chromatography and mass spectrometry experiments (Py-GC/MS) were carried out on eight woody and agricultural biomasses, including beech, poplar, pine forest residues, Scot Pine bark, reed canary grass, corn cob, grape seed cake and wheat straw. The selected temperature and duration for each fractionated pyrolysis step allowed separating the volatile pyrolysis products in function of their origin from biomass. As a result, carbohydrate derivatives from hemicelluloses were released at earlier fractionated pyrolysis steps, compared to those produced from cellulose degradation. Phenolic derivatives, mainly produced by lignin, were stepwise produced in function of the length and the nature of their side-chain substituents. Protein derivatives were also released in the whole Py-GC/MS temperature range. Macromolecular composition and biomass family were shown to play a crucial role in the thermal degradation of the biomasses of study. Production profiles exhibited resemblances per chemical species between deciduous and coniferous woods, while they appear to be more heterogeneous for agricultural biomasses. Herbaceous crops showed an intermediate behaviour between woods and agricultural biomasses.

Mild hydrotreating of bio-oils with varying oxygen content produced via catalytic fast pyrolysis

Several biomass catalytic fast pyrolysis oils produced over HZSM-5 at varying levels of catalyst of deactivation, and therefore exhibiting oxygen contents ranging from 6 wt% to 33 wt% (enabled due to catalyst deactivation) were subjected to mild hydrotreating over Ru/C at 140 °C. The purpose of this study was to evaluate the performance of these catalytic pyrolysis oils in this process, which is often used as a stabilization step prior to exposure of the bio-oil to more severe hydrodeoxygenation conditions in pyrolysis based biorefinery concepts. This will help better define the desired deoxygenation rate during CFP, and inform decisions about yield/quality and cost tradeoffs during CFP. High liquid product recoveries were achieved for the mild hydrotreating in all samples with varying O-contents, meaning the yield of hydrogenated liquids from biomass was nearly exclusively dependent on the catalytic pyrolysis step. However, a trend was observed that the bio-oils were more responsive to the hydrogenation with increasing oxygen content. For example, no aromatic ring hydrogenation was observed for the bio-oils with <20 wt% oxygen content but ring saturation was observed for bio-oils with oxygen contents of 25–30 wt%. The bio-oils with about 25–30% oxygen content had the largest increase in H/C ratio upon hydrogenation. This trend may be attributed in part to a solvent effect, where the more polar bio-oils acting as their own solvents, helped promote hydrogenation. With regard to product stability an increase in the average molecular weight of the bio-oils with >25 wt% oxygen content was observed for exposure to the hydrogenation conditions, suggesting some oligomerization occurred prior to hydrogenation in these cases. Taken together, bio-oils with about 25 wt% oxygen content responded well to the mild hydrotreatment and were stable to the conditions, and offered a 2–3 fold increase in carbon yield from biomass over the bio-oils that were more severely deoxygenated during catalytic pyrolysis. This suggests that severe reduction of oxygen in the CFP step may be not needed to economically produce fungible, stabilized biofuel intermediates in high carbon yield.

From Supramolecular Species to Self-Templated Porous Carbon and Metal-Doped Carbon for Oxygen Reduction Reaction Catalysts.

The preparation of carbon materials usually involves the decomposition of precursors and the reorganization of the as-generated fragments. However, the cleavage of bonds and the simultaneous formation of new bonds at nearly the same positions prevents effective yet precise fabrication. Herein, a supramolecular precursor, cucurbit[6]uril, that contains multiple bonds with distinct bond strengths is proposed to decouple the twin problem of simultaneous bond cleavage and formation, allowing multistage transformations to hierarchical porous carbon and metal-doped carbon in a single yet effective pyrolysis step without the need of a template or additional purification. As a proof-of-concept, the Fe-doped carbon electrocatalysts realized a Pt/C-like half-wave potential of 0.869 V vs. RHE and small Tafel slope of 51.3 mV dec-1 in oxygen reduction reaction.