Thermal Deoxygenation Research Articles

Electrochemical Exfoliation and Thermal Deoxygenation of Pristine Graphene for Various Industrial Applications

The transition of graphene from the lab to consumer goods is still a challenging job that necessitates efficient and cost-effective large-scale graphene production. This study combines electrochemical exfoliation in an aqueous solution of sulfuric acid (1M H2SO[Formula: see text] and hydrogen peroxide (3% H2O[Formula: see text] followed by thermal deoxygenation at a temperature of 800[Formula: see text]C within the ambient environment. This method allows the inexpensive synthesis of pristine graphene for various industrial applications. X-Ray diffraction (XRD) results for pristine graphene showed a distinct peak at 2[Formula: see text] with a corresponding interplanar distance ([Formula: see text] of 3.3754 Å and a crystallite size of 18 nm. XRD statistics indicated that the crystal structure of the original graphene was preserved. The crystalline structure was recovered and the interplaner distance was decreased following the high temperature thermal reduction. According to Raman spectroscopy, the impurity degree (I[Formula: see text]/I[Formula: see text] region fraction of pristine graphene was 0.211. This indicates that the original graph produced by the current method has little distortion. Raman analysis shows that there is a linear red shift in peaks D-band (D), G-band (G), and second order of the D-band (2D) due to the increase in phonon–phonon nonlinear interactions with increasing temperature, so that peaks (D), (G) and (2D) shifts are shown. The majority of the functional groups were discovered to be eliminated after high temperature thermal treatment. The three-dimensional graphene sheet is highly defined and intricately coupled in the microstructure analysis, resulting in a laxer and porous structure. When treated at a temperature below 800[Formula: see text]C, there was only minor damage to the reduced graphene oxide (RGO) microstructure. The results of the Atom Force Microscope (AFM) demonstrated that the flaws spread over time from the layer boundaries and pores to the edges and eventually resulted in a separate RGO archipelago. According to TGA analysis, at temperatures up to 800[Formula: see text]C, the RGO sheet loses up to 45% of its weight.

New insights on energetic properties of graphene oxide (GO) materials and their safety and environmental risks

Graphene oxide (GO) has been recognized as a thermally unstable and energetic material, but surprisingly its environmental and safety risks were not fully explored, defined, and regulated. In this study, systematic explosivity and flammability characterizations of commercial GO materials were conducted to evaluate the influence of key parameters such as physical forms (paste, powders, films, and aerogels), temperature, heating rate, mass, and heating environment, as well as their potential safety and environmental impacts. Results based on thermogravimetric analysis (TGA) showed that GO in paste and powder forms have lower temperature thresholds (>180–192 °C) to initiate micro-explosions compared to GO film and aerogels (> 205 °C and 213 °C) regardless of the environment (inert, air, or oxygen). The observed explosive behavior can be explained by thermal runaway reactions as a result of thermal deoxygenation and decomposition of oxygen functional groups. Flammability rating and limiting oxygen index (LOI) results confirmed that GO films are flammable materials that can spontaneously propagate flame in a low oxygen environment (~11 %). These results provided new insights about potential safety and environmental risks of GO materials, which somehow were not considered, suggesting urgent actions to improve current safety protocols for labeling, handling, transporting, and storage practices from manufacturers to the end-users.

Combustion dynamics of crude and upgraded Thermal DeOxygenation oils in a compression ignition engine

Thermal DeOxygenation (TDO) is a robust thermochemical conversion scheme to produce hydrocarbons from biomass feedstock. The process targets the carbohydrate fraction of biomass to yield a broad mixture of primarily aromatic hydrocarbons within a boiling point range of 348–798 K with low oxygen content (<4 wt%). The resulting materials are amenable to traditional hydrotreating and distillation processes with approximately 70% by mass in the distillate fuel range. The simple conversion scheme combined with commercially viable upgrading routes makes TDO oils a feasible alternative fuel for transportation applications. This paper is the first systematic treatment of fit-for-purpose testing of TDO oils in a compression ignition engine. Blends of partially upgraded TDO oils (e.g. whole oil, distilled oil, hydrotreated oil and hydrotreated-distilled oil) are prepared with certified ultra-low sulfur diesel at 5%, 10%, 15% and 20% by volume. The resulting fuels are analyzed for fuel characteristics and combustion dynamics in an instrumented single-cylinder compression ignition engine. All fuel blends at 10% blend level by volume exhibited adequate engine performance. Hydrotreating of the oils is a necessary step to meet cetane number and EPA soot emissions requirements at 20% blend volume. Combined distillation and hydrotreatment meet or exceed all fuel specification and engine performance benchmarks. Partially upgraded TDO oils are suitable fuel options for compression ignition applications.

Combustion Dynamics of Crude and Upgraded Thermal Deoxygenation Oils in a Compression Ignition Engine

Combustion Dynamics of Crude and Upgraded Thermal Deoxygenation Oils in a Compression Ignition Engine

Comparative, reusability and regeneration study of potassium oxide-based catalyst in deoxygenation reaction of WCO

In this work, the comparative study on the performance of K 2 O/SiO 2 and calcined dolomite catalysts was conducted via deoxygenation of waste cooking oil (WCO). KSi catalyst has the potential as a deoxygenation catalyst due to mesoporous structure catalyst with high base properties which enhance oxygen removal. The result found that K 2 O/SiO 2 catalyst could be used in the deoxygenation of WCO generating a high yield of pyrolysis oil as compared to thermal deoxygenation and calcined dolomite catalyst. Besides that, the reusability and regeneration of the K 2 O/SiO 2 catalyst were evaluated in the deoxygenation reaction using WCO as a feedstock. Five consecutive runs of reusability test and three successive cycles with two regenerations were performed. The reusability and followed by regeneration tests were conducted at conditions: 30 min of reaction time, 390 ± 5 °C reaction temperature and 150 cm 3 /min of N 2 flow rate. The liquid products obtained from each cycle were analyzed by GC–MS. The deoxygenation of WCO using K 2 O/SiO 2 catalyst rendered higher selectivity towards diesel products (C 13 -C 24 ). The K 2 O/SiO 2 catalyst presented a good performance in reusability and regenerability test with only ∼19.3–22.4% dropped in pyrolysis oil yield after 5 consecutive runs and only ∼11.20–13.23% drop in diesel yield after regeneration. The results showed that K 2 O/SiO 2 catalyst has tremendous stability in the deoxygenation of WCO into green diesel and could be the alternative deoxygenation base catalyst for the deoxygenation process.

Structural control of highly oxidized carbon nanotube networks for high electrochemical performance

Carbon nanotubes (CNTs) are one of the most suitable candidates for electrochemical applications because of their high electrical conductivity and large specific surface area. However, the bundling behavior of single-walled CNTs (SWCNTs) due to π–π interaction limits their solution processability and structural control. Herein, we report a fabrication method for highly conductive and porous CNT network films exhibiting a high electrochemical performance in aqueous media. This was achieved through the filtration of a dispersant-free dispersion of oxidized carbon nanotubes by less defective chlorate-based oxidation and thermal deoxygenation in air. To increase the proportion of mesopores in the film, oxidized long multi-walled CNTs (Ox-LMWCNTs) were incorporated into Ox-SWCNT networks. The Ox-SWCNT/Ox-LMWCNT (1/1 wt.%) hybrid film exhibited a large surface area of 492 m2/g, which decreased to 225 m2/g after thermal treatment at 200 °C in air with increasing electrical conductivity up to 29,500 S/m. In particular, the proportion of mesopores increased from 65 to 89%. The enhanced electrochemical capacity of the hybrid films (147 F/g and 99% retention at 10 A/g) could be attributed to the increased mesopores and enhanced electrical conductivity of LMWCNTs after thermal deoxygenation even in air.

Conversion of Residual Palm Oil into Green Diesel and Biokerosene Fuels under Sub- and Supercritical Conditions Employing Raney Nickel as Catalyst

A comprehensive study of the thermal deoxygenation of palm residue under sub- and supercritical water conditions using Raney nickel as a heterogeneous catalyst is presented in this paper. Hydrothermal technology was chosen to replace the need for hydrogen as a reactant, as happens, for example, in catalytic hydrotreatment. Several experiments were carried out at different reaction temperatures (350, 370, and 390 °C) and were analyzed with different times of reaction (1, 3.5, and 6 h) and catalyst loads (5, 7.5, 10 wt.%). No hydrogen was introduced in the reactions, but it was produced in situ. The results showed the selectivity of biokerosene ranged from 2% to 67%, and the selectivity of diesel ranged from 5% to 98%. The best result was achieved for 390 °C, 10 wt.% catalyst load, and 3.5 h of reaction, when the selectivities equal to 67% for biokerosene and 98% for diesel were obtained. The Raney nickel catalyst demonstrated a tendency to promote the decarboxylation reaction and/or decarbonylation reaction over the hydrodeoxygenation reaction. Moreover, the fatty acid and glycerol reforming reaction and the water−gas shift reaction were the main reactions for the in situ H2 generation. This study demonstrated that a hydrothermal catalytic process is a promising approach for producing liquid paraffin (C11−C17) from palm residue under the conditions of no H2 supply.

Towards continuous deoxygenation of acetic acid catalyzed by recyclable mono/bi/trimetallic zeolite catalysts

A series of mono (Ni, Cu, Co), bi (NiCu, NiCo, CuCo), and trimetallic (NiCuCo) mordenite supported catalysts were characterized and evaluated for the continuous, near-atmospheric pressure, thermal deoxygenation of acetic acid. Acetic acid was selected as a model reactant due to its abundance in both biomass pyrolysis upgrading streams and its analogous structure to carboxylic acids found in vegetable oil upgrading streams. Surface area and metal loading were nearly constant for all studied catalysts, allowing an in-depth direct comparison of the metallic activity for reaction pathways including gasification, decarboxylation, decarbonylation, hydrodeoxygenation, and ketonization. In the absence of Ni or in the absence of H2, the observed catalytic activity was low. Results from the bimetallic samples at 400 °C highlighted the importance of Ni for H2 activation and Co for the simultaneous promotion of hydrodeoxygenation and gasification. A nearly linear correlation between the Ni content and the conversion of acetic acid was observed at 400 °C. Cryogenic argon isotherms revealed the location of metal sites within the mordenite pore, further emphasizing the impact of confining environments on the deoxygenation of bio-derived compounds. TGA, TPR, and TPD studies provided information on catalyst stability, reducibility, and acidity, respectively. HRTEM indicated that agglomerates formed under the studied reaction conditions. The fresh Ni/MOR catalyst, under differential conversion conditions, was stable for ~ 24 h at 460 °C, for an additional ~ 20 h upon regeneration at 460 °C, and for an additional 30 h upon regeneration at 500 °C. Long-exposure activity was observed in the Ni/MOR catalyst, favoring hydrodeoxygenation and decarbonylation for at least 70 h under integral conversion conditions. In the bimetallic NiCo/MOR catalyst, Co stabilized Ni active sites in a co-located configuration which promoted hydrodeoxygenation, but also promoted gasification, and eventually lead to coking/lower conversion.

Intensification of Biomass Thermal Deoxygenation via a Two-Stage Process

Thermal deoxygenation (TDO) is a promising reaction scheme for producing low oxygen bio-oil from biomass carbohydrate. The primary step in bio-oil production involves pyrolysis of alkaline earth metal-neutralized biomass hydrolysates at 723 K yielding bio-oil, chars, carbonates, and light gases. Reactor scaling from bench to floor-scale, however, reduced carbon yields from 80% to 48% of theoretical, respectively. This paper details a two-stage process to intensify the TDO process, improving carbon yields to 79% of theoretical. The scheme involves a 523 K thermal pretreatment (stage I) to yield a polysalt and transition of a melt-phase. The resulting solid polysalt is reduced to powder to improve material handling and reaction rates during decomposition at 723 K (stage II). Resulting bio-oil yield is shown to improve from 0.082 to 0.16 kg-oil/kg-feed. A two-step reaction model is developed detailing the reaction rates and regimes which can guide continuous process design efforts.

Rational electrodeposition of Cu on highly oxidized multiwalled carbon nanotube films

Nanohybridization of carbon nanotubes (CNTs) and Cu is a promising strategy to enhance the electrical performance of CNT films or fibers for applications in electromagnetic shielding and for further uses as conductors. However, overcoming the hydrophobic characteristics of CNTs is one of the most appropriate problem faced during the fabrication of hybrid materials with foreign materials. In this study, we report a fabrication method for highly conductive long multiwalled CNTs (LMWCNTs)/Cu hybrid films based on electroplating. The wettability of the Cu plating solution and the electrical conductivity of the LMWCNT films were rationally controlled by thermal deoxygenation in air at temperatures below 200 °C. The thermal modification provides a highly conductive and hydrophilic surface on the CNT structure; these physical changes eventually enable uniform Cu electrodeposition in an aqueous electrolyte. The periodic morphological, electrochemical, electrical, and crystallographic analyses indicate that Cu nucleated from the inside of the CNT film during the initial stage of electrodeposition; further, the Cu nuclei subsequently grew on the CNT surface, resulting in a densely packed CNT-Cu composite.

Upgrading of coconut shell-derived pyrolytic bio-oil by thermal and catalytic deoxygenation

ABSTRACT The objective of this study is to upgrade the pyrolysis oil obtained from coconut shells via thermal deoxygenation and catalytic hydrodeoxygenation (HDO) and compare the elemental properties of the upgraded bio-oil samples. The crude coconut shell pyrolysis oil (cr-CSPO) was obtained in 33% yield by intermediate pyrolysis (575°C) of pre-dried coconut shells. The higher heating value (HHV) of cr-CSPO was found to be 16.46 MJ/Kg. The thermal and catalytic upgrading was done at 250°C, 30 bar of hydrogen pressure, a reaction time of 3 h, and a stirring speed of 350 rpm. In the case of catalytic upgrading, 10% Pd/C (10 wt% of cr-CSPO) was used as the catalyst. Thermally heating the cr-CSPO under identical conditions without the catalyst provided oil of HHV 25.94 MJ/kg. Catalytic HDO of the cr-PCSO showed a noticeable increase in the HHV value to 30.57 MJ/kg. The results indicate significant improvement in the combustion properties of cr-CSPO by thermal treatment and more so by the catalytic HDO chemistry.

Efficient oxidation and rational reduction of long carbon nanotubes for multifunctional superhydrophobic surfaces

The inclusion of conducting nanomaterials in superhydrophobic surfaces can widen their potential applications in terms of Joule heating, electromagnetic interference shielding, oil/water separation, and self-cleaning. Here, we demonstrate the fabrication of multifunctional superhydrophobic surfaces using dispersant-free conducting inks containing highly oxidized long multiwalled carbon nanotubes (Ox-LMWCNTs). Superhydrophobic surfaces with a high water contact angle (WCA) (>150°) were realized by deposition of a perfluorosilane sol and silica nanoparticle mixture solution onto the Ox-LMWCNT surface and subsequent thermal treatment. Importantly, the electrical conductivities of the Ox-LMWCNT films were dramatically increased from 78 S/m to more than 2000 S/m by thermal deoxygenation, even at low temperatures (<200 °C) in ambient air. The superhydrophobic LMWCNT films showed high electrical conductivity of more than 1000 S/m following thermal treatment at 150 °C in ambient air. These electrically conducting and self-cleaning surfaces also showed fast heating behavior when a direct current voltage was applied to the film. Moreover, sequential deposition of the LMWCNT and perfluorosilane sol solutions on a metal mesh produced an oil/water separation filter owing to the oleophilic properties of the LMWCNTs. As they are easily dispersed in solution and can undergo efficient thermal deoxygenation, Ox-LMWCNTs are promising for the realization of multifunctional surfaces.

Enhanced permeability of rGO/S-GO layered membranes with tunable inter-structure for effective rejection of salts and dyes

In this work, a novel rGO/S-GO laminated membrane was prepared by a pressure-assembly stacked method, followed with a thermal deoxygenation process. The neighboring interlayer spacing (d) between the composite layers are tunable due to the incorporation of S-GO. The nano-filtration performances of the rGO/S-GO laminated membranes were evaluated at a low-pressure condition. Molecule dynamics (MD) simulation was used to further investigate the size distribution of spacing between GO, rGO and S-GO sheets. The results of filtration experiments indicated that the obtained rGO/S-GO membrane showed a satisfied rejection performance for the removal of dyes and salts with a pressure of two bar. The rejection rates of MB, CR, RB and MO were 99.5%, 99.9%, 97.3% and 98.6%, while the rejection rates of Na2SO4, MgSO4, MgCl2 and NaCl were 86.3%, 40.9%, 35.7% and 60.5%, respectively. Compared to the pristine rGO membrane, the water permeation of rGO/S-GO laminated membrane was significantly improved from ∼0.98 to ∼3.78 L/(m2·h·bar) due to the enlarged ‘gateway’ for transport of water molecules. The results of classical MD simulation showed that the neighboring layer spacing of rGO, GO and S-GO was ∼8.4, ∼10.2, and ∼14.3 Å, respectively. Their neighboring layer spacing was dependent on the chemical functional groups on the edges of GO sheets. It was further confirmed that the introduction of chemical groups on the GO caused the expansion of the interlayer ‘gap’ between neighboring sheets, which was responsible for the enhanced permeability. These findings would contribute to the development of GO-based nanofiltration membranes with high permeability and understanding the transport mechanism of water molecule.

Deoxygenation of Biomass Pyrolysis Vapors via in Situ and ex Situ Thermal and Biochar Promoted Upgrading

Production of stable, partially deoxygenated biomass pyrolysis bio-oils is needed to increase the fungibility of bio-oil for refining into fuels and chemicals. While zeolite catalyzed upgrading is commonly used to produce such liquids, the associated catalyst deactivation is a significant hurdle to overcome. Our group has previously reported the thermal deoxygenation of pyrolysis vapors that is carried out under an atmosphere partially consisting of recycled tail gas and without the use of externally added catalysts. In this study, thermal deoxygenation was further studied in a new and scaled-down (laboratory scale) pyrolysis system to allow for a systematic study and to better understand the factors affecting vapor deoxygenation. Temperature excursions from the fast pyrolysis temperatures near 500 °C and/or the catalyzing effect of accumulated biochar were hypothesized to be potential key parameters affecting vapor deoxygenation. Therefore, experiments were conducted by utilizing a recycled gas and inert...

Economics of biofuels: Market potential of furfural and its derivatives

Production of biofuels from cellulosic materials continues to face major challenges in terms of economic profitability. Our research focuses on evaluating the economic potential of several major biochemical co-products derived from renewable fuel production that may help to overcome these challenges. In our thermal deoxygenation (TDO) process of renewable fuel production, furfural (a platform chemical) is produced in significant volumes. The quantity of furfural produced at commercial scale, however, will likely impact the national and world price of this industrial chemical. This will reduce its ability to play an important role in the total economic viability of the renewable fuel process. Thus, it is better to convert furfural to other products to have a smaller impact on market prices and, consequently, a higher profit margin for the renewable fuel process as a whole. In this paper we identify the furfural derivatives that have a considerable market size and can be derived from furfural in one or two steps of conversion. We then look at maximizing the profits of a multiproduct biofuel producer facing world demand curves that consider the effect of the producer's output on market prices. We solve the parameterized model using nonlinear optimization method under a variety of alternative assumptions and scenarios. Our results show that renewable fuel production can be made significantly more financially attractive through sales of furfural derivatives. A key issue to resolve is the elasticity and cross-elasticity of demand for our identified industrial chemical.

Techno-economic analysis of thermal deoxygenation based biorefineries for the coproduction of fuels and chemicals

The economic impact of coproduction of renewable fuels with platform chemicals is determined by assessing thermal deoxygenation (TDO) pathway based biorefineries with two distinct product suites: (1) fuel and furfural (a platform chemical) and (2) fuel and levulinic acid (a platform chemical). Greenfield and brownfield plant site scenarios are considered. Additionally, the economic viability of producing activated carbon from biochar, rather than burning it to produce energy, is assessed. The biorefinery in which wood is converted using the TDO pathway to furfural, renewable fuel, and biochar is found to be a product-driven biorefinery. The production of renewable fuel along with levulinic acid from recycled cardboard via the TDO pathway is determined to be an energy-driven biorefinery. The minimum selling price (MSP) of TDO oil produced in product-driven and energy-driven greenfield biorefineries are estimated at US$17 and US$18 per GJ or US$2.78 and US$2.92 per gallon of gasoline equivalent (GGE), respectively. It is found that capital investment for the product-driven and energy-driven biorefineries can be reduced by 23–27% through integrating the TDO process into an existing pulp and paper facility (brownfield site), provided the infrastructure and assets of pulp and paper mill are well maintained. It has been learned that the synergy arising through co-production of chemicals with fuels and vice versa can facilitate the sustainable production of both renewable fuels as well as platform chemicals. Moreover, there is a need for the development of new less energy intensive separation processes for purifying bio-products.

Decomposition Reactions and Kinetics of Alkaline-Earth Metal Levulinate and Formate Salts

Decomposition of biomass-derived alkaline-earth metal levulinate and formate salts above 700 K, commonly called thermal deoxygenation (TDO), has previously been demonstrated to produce deoxygenated crude oil at 80% of theoretical yield suitable for refining to gasoline, jet, and diesel fuel. Decomposition in thermogravimetric experiments involves low-temperature (423–623 K) and high-temperature reaction (623–723 K) regimes. The current work presents results of isothermal decomposition and infrared techniques which provide insights into the low-temperature, or Stage I, reactions. Stage I reactions are shown to be primarily addition/condensation reactions between levulinate ketone groups evolving water which equates to 8–15 wt % of the sample. These Stage I reactions account for one-third of theoretical oxygen removal of the levulinate and formate salts while also increasing the molecular weight of the organic fraction. Therefore, Stage I is an important reaction step in the TDO process.

ChemInform Abstract: Deoxygenation of Biobased Molecules by Decarboxylation and Decarbonylation — A Review on the Role of Heterogeneous, Homogeneous and Bio‐Catalysis

AbstractReview: 222 refs.

Hydroprocessing of Biorenewable Thermal Deoxygenation Oils

Thermal deoxygenation (TDO) of neutralized biomass acid hydrolyzate, namely, levulinate and formate salt mixtures, is demonstrated to yield low oxygen bio-oils suitable for transportation fuels. The chemistry and upgrading potential are evaluated for TDO oils derived from calcium- and magnesium-neutralized model biomass acid hydrolyzate containing levulinate/formate salt mixtures at a 1:1 molar ratio. TDO oils were prepared using a 50 L semibatch reactor and analyzed for component chemistry and physicochemical properties. The TDO oils contain a broad distribution of monoaromatic and polyaromatic hydrocarbons with H:C ratio of ≅1:1. Crude oils were processed under hydrogen pressure in a vertical downflow tubular reactor, using a Ni/SiO2–Al2O3 catalyst. Sustained yields of 90+ wt % were achieved over 700 h operating without catalyst regeneration. Products were identified by GC-MS to contain primarily naphthenes, monoaromatics, partially saturated polyaromatics, and only trace oxygenates. Hydroprocessed oils...

Sintesis Senyawa Turunan 2-Metoksi-3H-Azepina Melalui Reaksi Termal antara Alkylnitrobenzena dan Tributilphosphina

Although photolysis of phenyazide has been widely reported to give 3 H -azepine, the thermal deoxygenation reaction of alkylnitrobenzene derived similar products hitherto unexplored. Novel synthesis of 2-methoxy-3 H -azepine derivatives was carried out using alkylnitrobenzene with tributylphosphine (Bu 3 P) reacted at 150°C for 24 hours in the presence of methanol. Reaction of m -nitrobenzene with the above methods gave two isomers of 3 H -azepine, namely, 2-methoxy-6-methyl-3 H -azepine and 2-methoxy-4-methyl-3 H -azepine in 61%. Reaction of 2,3-dimethylnitrobenzene with Bu 3 P afforded the three isomers, that is, 2-methoxy-6,7-dimethyl-3 H -azepine; 2-methoxy-3,4-dimethyl-3 H -azepine and 7-methoxy-5,6-dimethyl-4 H -azepine. Reaction of 3,5-dimethylnitrobenzene gave the sole product of 2-methoxy-4,6-dimethyl-3 H -azepine in 42%. In contrast, reaction of 2,6-dimethylnitrobenzene didn’t give any product because the steric effect of methyl groups attached on C2 and C6. Structure elucidation of all novel products have confirmed by HETCOR.