Oxygen Removal Efficiency Research Articles

Catalytic aqueous hydrodeoxygenation of palmitic acid with in-situ hydrogen donor

Algal bio-oil obtained from hydrothermal liquefaction of algae contains a large amount of water and long-chain fatty acids. High acidity and corrosiveness seriously restrict the application of algal bio-oil. The aqueous-phase catalytic upgrading was a promising approach to solve this problem, and the hydrogen donor was one of the most important parameters to the conversion of the algal bio-oil and the quality of the products. Catalytic transfer hydrogenation (CTH) reaction was an efficient, economical and green method for hydrogenation reaction, which can directly transfer hydrogen from the hydrogen donor to the reaction substrate. In this work, the CTH reaction of algal bio-oil model compound palmitic acid was investigated to deal with the problem of high oxygen content in the algal bio-oil. Several common hydrogen donors, included methanol, ethanol, formic acid, and isopropanol, as well as different reaction conditions were experimented to study the CTH process of palmitic acid. The results showed that, with the reaction conditions of 350 °C and 10 h, formic acid achieved the best oxygen removal, carbon retention and energy efficiency, the C16 selectivity reached the highest at 33.3 % as the formic acid addition ratio was 1:2, and the C15 selectivity reached the highest at 48.3 % as the formic acid addition ratio was 1:3. In general, the best ratio of formic acid added was 1:3, which showed the highest yield of C15 and above alkanes of 79.6 %. This result indicates that the catalytic transfer hydrogenation reaction of formic acid has practical value in improving the combustion performance of algal bio-oil.

High-efficient removal of Oxygen(O2) impurity from H2 flow on nickel-manganese Oxide: Regulating the exposed crystal plane, structure-activity relationship and determination of active sites

The presence of oxygen (O2) impurity in hydrogen produced by water electrolysis can pose safety hazards when hydrogen is used as a power source. Therefore, oxygen (O2) impurities must be removed from H2 flow to meet the strict purity requirements. In this work, nickel manganese oxide is applied to remove oxygen from H2 flow. It is synthesized via the co-precipitation method using different precipitants, manganese and nickel precursors. The results of the oxygen removal test show that NiMn-4 catalyst, prepared using oxalic acid, manganese acetate and nickel nitrate as the precursors, has the best performance in removing oxygen impurities from the hydrogen flow. The catalyst could retain an oxygen removal efficiency of nearly 70 % at the reaction temperature of 80 °C. Also, XRD, Raman spectra and HRTEM analysis results show that the crystal phase of NiMn-4 (Ni6MnO8) exhibits much stronger crystallinity than the other catalysts and has (400) and (222) planes of Ni6MnO8. H2/O2-TPD and H2-TPR analysis results indicate that NiMn-4 catalyst has much more adsorbed oxygen species, overflow hydrogen and hydrogen consumption at per specific surface area compared to the other catalysts. The XPS results of Ni2p and O1s imply that there is much higher valence of Ni (Ni3+).

Influence of the Geometry of the Oxygen Removal Chamber on the Oxygen Concentration in a PEM Water Electrolysis System

In this paper, we investigate the optimization of an oxygen removal system for water electrolysis plants because high oxygen concentrations can be dangerous and compromise the quality of the hydrogen produced. The design of an oxygen removal system was investigated using numerical analysis. The results showed that the diameter of the chamber had a significant effect on the oxygen removal efficiency, and a diameter twice the size of the gas inlet was found to be optimal. The porosity of the catalyst layer also played a crucial role in the efficiency, with a lower porosity resulting in higher removal rates. Additionally, the optimal chamber length was found to be 76.8 D to achieve an oxygen mole fraction of 2.4 ppm after the chamber, which satisfied the safety criterion of 4.0 ppm. These results can aid in the design of oxygen removal systems for water electrolysis plants, providing a more efficient and safer operation.

A comparison of mesophotic and shallow sponge holobionts resilience to predicted future temperature elevation

Climate change is predicted to have detrimental impacts on sessile invertebrates, including sponges. Mesophotic ecosystems have been suggested to play a major role as refugia for coral reef sponge species, however knowledge regarding the ability of mesophotic sponges to cope with thermal stress is scarce. In this study we compared the response of the sponge Diacarnus erythraeanus, a widespread Red Sea sponge, from the shallow and mesophotic reef, to moderate and acute temperature elevation (2°C and 6°C, respectively) for short and long term periods (two and 35 days, respectively) by measuring physiological parameters (respiration, oxygen removal, pumping rates, and photosynthetic efficiency), and the microbiome composition change. The results indicated that mesophotic and shallow populations of D. erythraeanus are highly tolerant to both moderate and acute heat stress, demonstrating a high survival rate (100%) across the experimental treatments, with no visible signs of bleaching or necrosis. Exposure to heat stress resulted in significant alterations in the physiological parameters of sponges, including higher respiration rate and lower photosynthetic efficiency. These alterations were accompanied by correspondingly significant microbial adjustments, thus emphasizing the essential role of the microbiome in the host’s ability to persist when facing essential environmental stress. Moreover, while shallow and mesophotic sponges showed similar physiological tolerance to heat stress, their microbial response differed: while the microbiome diversity of the mesophotic sponges remained stable throughout the experiment, the shallow one significantly changed. This result suggests that their underlying coping mechanisms might differ between mesophotic and shallow populations. Since the associated-microbiome is largely regulated by the sponge-host genetics, difference in microbial adjustments to stress between populations, could indicate genetic variability between hosts. Therefore, while the results of this study support the hypothesis that mesophotic coral reefs could serve as thermal refugia for some sponge species, it raises the question regarding the validity of MCEs as a refuge for shallow populations. Finally, it emphasizes the crucial need to elucidate the underlying mechanisms governing the sponge-microbiome interactions, specifically in the context of the anticipated climate change scenarios.

Effect of preparation method of NiMo/γ-Al2O3 on the FAME hydrotreatment to produce C15–C18 alkanes

The second-generation biodiesel is a clean, green and renewable energy. Herein, NiMo/γ-Al2O3 catalysts were prepared by different methods and used for hydrodeoxygenation of fatty acid methyl ester (FAME) to produce C15–C18 alkanes. The Al–Ni spinel (NiAl2O4) and NiMoO4 species can be formed during the impregnation method, while NiAl2O4 and NiMoO4 can be inhibited by co-precipitation method. The Ni3+ species on the catalyst surface from impregnation and co-precipitation method was assigned to NiMoO4. Ni15Mo5/γ-Al2O3-CP (co-precipitation method) with smaller particle size of active metal oxides, large pore size, and more contents of low chemical valence states from active metal species (Ni2+ and Mo4+) shows a higher hydrodeoxygenation performance than Ni15Mo5/γ-Al2O3-IM (impregnation method). The liquid yield, conversion, oxygen removal efficiency, and selectivity of C15-18 alkanes over Ni5Mo5/γ-Al2O3-CP are 76%, 100%, 99.05%, and 92.45%, respectively. It also shows a stable catalytic performance during 200 h test.

Gas-pressurized torrefaction of biomass wastes: Self-promoted deoxygenation of rice straw at low temperature

Gas-pressurized (GP) torrefaction of biomass, proposed in our previous work, has a much higher oxygen removal efficiency compared to conventional torrefaction, but how the pressure promoted the deoxygenation remains unclear. In this work, the GP torrefactions under different partial pressures of volatiles (Pvol) and total pressures (Ptot) were conducted. The results revealed that the Pvol was the root cause rather than the Ptot of the acceleration of biomass decomposition and deoxygenation for the first time. This process can be regarded as a self-promoted deoxygenation process, and consisted of three stages. Stage 1 was the volatiles formation stage, where hemicellulose decomposed, volatiles formed and the Pvol increased. Stage 2 was self-promoted dehydration stage, where the hydroxyl in biomass was dramatically removed. Stage 3 was structure rearrangement stage, where the aromatic structure formed. The stage 2 and stage 3 were highly correlated with the Pvol, and resulted in the deep deoxygenation of biomass. This study should be not only suitable for the GP torrefaction, but can also be extended to pressurized pyrolysis and gasification of biomass.

Renewable Hydrocarbon Production from Waste Cottonseed Oil Pyrolysis and Catalytic Upgrading of Vapors with Mo-Co and Mo-Ni Catalysts Supported on γ-Al2O3.

In this work, the production of renewable hydrocarbons was explored by the means of waste cottonseed oil (WCSO) micropyrolysis at 500 °C. Catalytic upgrading of the pyrolysis vapors was studied using α-Al2O3, γ-Al2O3, Mo-Co/γ-Al2O3, and Mo-Ni/γ-Al2O3 catalysts. The oxygen removal efficiency was much lower in non-catalytic pyrolysis (18.0%), whilst γ-Al2O3 yielded a very high oxygen removal efficiency (91.8%), similar to that obtained with Mo-Co/γ-Al2O3 (92.8%) and higher than that attained with Mo-Ni/γ-Al2O3 (82.0%). Higher conversion yields into total renewable hydrocarbons were obtained with Mo-Co/γ-Al2O3 (61.9 wt.%) in comparison to Mo-Ni/γ-Al2O3 (46.6%). GC/MS analyses showed a relative chemical composition of 31.3, 86.4, and 92.6% of total renewable hydrocarbons and 58.7, 7.2, and 4.2% of oxygenated compounds for non-catalytic bio-oil (BOWCSO), BOMoNi and BOMoCo, respectively. The renewable hydrocarbons that were derived from BOMoNi and BOMoCo were mainly composed by olefins (35.3 and 33.4%), aromatics (31.4 and 28.9%), and paraffins (13.8 and 25.7%). The results revealed the catalysts’ effectiveness in FFA decarbonylation and decarboxylation, as evidenced by significant changes in the van Krevelen space, with the lowest O/C ratio values for BOMoCo and BOMoNi (O/C = 0–0.10) in relation to the BOWCSO (O/C = 0.10–0.20), and by a decrease in the presence of oxygenated compounds in the catalytic bio-oils.

Activated carbons from co-carbonization of waste truck tires and spent tea leaves

This study reports the co-carbonization of waste truck tires (WTT) and spent tea leaves (STL) at different blend ratios using chemical activating reagents (KOH and ZnCl2) carried out at 800 °C. The highest BET surface area from blends was 527.24 m2/g, obtained using ZnCl2 activation at a blend ratio of 1:3 (WTT/STL). Activated carbons yields in the blends were the highest at a blend ratio of 3:1 (WTT/STL) for both chemical activations. They were 24.37 wt% for KOH activation and 41.59 wt% for ZnCl2 activation. ZnCl2 activation produced higher carbon and lower oxygen content than those using KOH activation. Regardless of the type of feed, the oxygen removal efficiency of ZnCl2 was higher than that of KOH under identical conditions. Among all the activated carbons produced, the BET surface area of the activated carbons obtained from the carbonization of STL alone was highest for both activations. The BET surface area of the activated carbons produced in this study was comparable to that of activated carbons produced commercially.

Gas-pressurized torrefaction of biomass wastes: The optimization of pressurization condition and the pyrolysis of torrefied biomass

A novel gas-pressurized (GP) torrefaction with high oxygen removal efficiency at mild temperature was proposed in our previous work. However, the optimal condition of the GP torrefaction and subsequent pyrolysis of the torrefied biomass were not clear. In this work, the effect of pressure on the GP torrefaction and pyrolysis product properties of the torrefied biomass were studied in detail. The results show that the pressure increasing from 1.7 MPa to 5.0 MPa just slightly contributed to further oxygen removal, and 1.7 MPa was thus selected as the optimum pressure. The GP torrefaction significantly improved the product property of biomass pyrolysis compared to the conventional torrefaction (AP torrefaction). The acids content in bio-oil was reduced from 15–20% to less than 5%, and the calorific value of biogas increased to as high as 16.57–19.31 MJ/Nm3. Furthermore, an overall conversion mechanism of combined GP torrefaction and subsequent pyrolysis of biomass was proposed.

Conversion of agricultural waste into stable biocrude using spinel oxide catalysts

Biomass, the feedstock for biocrude and ultimately renewable diesel is a low energy density feedstock. The transport of this feedstock over long distance has been proven to be a major burden on the commercialisation of biorefining. Therefore, it has been generally accepted that biomass should be upgraded to biocrude (a relatively high energy density liquid) in close proximity to the biomass sources. The biocrude liquid would then be transported to a biorefinery. Biocrude contains large amounts of oxygen (generally up to 38 wt%) that is removed from the crude in the refining process. In this study, we have synthesised a range of spinel oxide based catalysts to remove oxygen from the biocrude during the catalytic fast pyrolysis. The activity of spinel oxide (MgB2O4 where B = Fe, Al, Cr, Ga, La, Y, In) catalysts were screened for the pyrolysis reaction. While all the tested spinel oxides deoxygenated the pyrolysis vapour, MgCr2O4 was found to be effective in terms of oxygen removal efficiency relative to the quantity of bio oil produced.

Efficient and stable Ni-Cu catalysts for ex situ catalytic pyrolysis vapor upgrading of oleic acid into hydrocarbon: Effect of catalyst support, process parameters and Ni-to-Cu mixed ratio

To eliminate the problematic need for liquid phase, high temperature, and high pressure, as well as the excessive consumption of hydrogen and production of aromatic hydrocarbons, associated with traditional aviation oil preparation processes, Ni–Cu bimetallic catalysts were synthesized and evaluated for ex situ catalytic pyrolysis vapor upgrading of oleic acid under a N2 atmosphere. The effects of catalyst support (AC, Al2O3, ZrO2, HZSM-5, HUSY, Hβ and MCM-41), pyrolysis process parameters (pyrolysis temperature, catalytic temperature and amount of oleic acid injected), and the mixing ratio of modified metals (Ni:Cu = 0:1,2,1:1,1:2,1:0) on the catalytic conversion of oleic acid to high-quality chemicals were studied. The catalysts were characterized by XRD, BET and NH3-TPD. Modified bimetallic catalysts show great potential for green diesel production without the use of H2 feed. The abundance of Brønsted acid sites favors HDO routes (such as HZSM-5, HUSY, Hβ and MCM-41), while Lewis acid sites (such as ZrO2 and Al2O3) favor hydrogenation and decarbonylation reactions. The addition of Cu enhances the reducibility of Ni and inhibits the cracking reaction and deactivation caused by coke. The addition of Ni effectively promotes the conversion of oleic acid, accelerates the fracture of C–C and effectively improves the production of hydrocarbons. The highest conversion was 100% with 85.68% selectivity towards hydrocarbons under pyrolysis at 450 °C, a catalytic temperature of 500 °C, and a feed quantity of oleic acid of 0.25 ml/min using Ni–2Cu/MCM-41 catalysts, and the oxygen removal efficiency and selectivity of C17 hydrocarbon were the highest (85.68% and 26.77%, respectively). The main products were olefins. In addition, the regenerated catalyst had good stability and could be used for at least 3 reaction cycles without observation of significant deactivation.

Enhancement of the production of bio-aromatics from renewable lignin by combined approach of torrefaction deoxygenation pretreatment and shape selective catalytic fast pyrolysis using metal modified zeolites

In this work, combined approach of torrefaction deoxygenation pretreatment (TDP) and shape selective catalytic fast pyrolysis (SS-CFP) using bifunctional catalyst (metal modified HZSM-5) were employed to improve the yield of bio-BTX derived from the renewable starting material of lignin. Results showed that after TDP, the oxygen element could be removed effectively. The oxygen removal efficiency reached its maximum value of 22.27% at 300 °C, resulting in markedly decrease of unnecessary oxygenates in bio-oil. Compared to parent HZSM-5, all metal modified HZSM-5 (Ga/HZSM-5, Zn/HZSM-5, and Ga-Zn/HZSM-5) promoted the formation of bio-BTX. Zn/HZSM-5 showed the highest selective yield of bio-BTX because of the enhancement deoxygenation reaction of oxygenates and the aromatization reaction of olefins. The combined approach of TDP and SS-CFP remarkably improved the selective yield of bio-BTX, reaching the maximum value of 65.19%, which was much higher than that from single approach of TDP (33.84%) and SS-CFP (47.36%).

The Evaluation of Dissolved Oxygen Removal Efficiency for Membrane Degassing Process in Ultrapure Water

The Evaluation of Dissolved Oxygen Removal Efficiency for Membrane Degassing Process in Ultrapure Water

Mg/SiO2–Al2O3 supported nickel catalysts for the production of naphthenic hydrocarbon fuel by hydro-de-oxygenation of eugenol

Ni–Mg supported on both mesoporous Al2O3–SiO2 (10) and γ-Al2O3 with Al2O3–SiO2/Mg = 10 and γ-Al2O3/Mg = 10 ratio were prepared via wet impregnation method. The synthesized materials were characterized by XRD, N2-sorption study, NH3-TPD/H2-TPR, FT-IR, DRS-UV and used in hydrodeoxygenation (HDO) of eugenol to produce hydrocarbons in a high pressure reactor. The reactant molecules could be facilitated to yield hydrocarbon fuel by active nickel active sites. The high oxygen removal efficiency of 75% was achieved with C9 hydrocarbon selectivity. Evaluation of catalytic properties such as high hydrogen consumption of 145 μmol/g (H2-TPR) and enriched surface acidity of 2.35 mmol g−1 (NH3-TPD) was done. Ni/Mg-SA (10) exhibited the highest catalytic activity of 6.7 × 10−4 mol g−1 s−1 SRR and 10.27 s−1 TOF respectively. The stability of catalysts was found to be 185 mg/g for Ni/Mg-SA (10) catalyst by TGA analysis. The structure-activity relationship was studied and the product distributions were also discussed in detail.

Oxygen migration characteristics during bamboo torrefaction process based on the properties of torrefied solid, gaseous, and liquid products

Bamboo is a potentially renewable biomass resource which can be converted into bio-fuels and bio-chemicals by thermochemical conversion technology. Torrefaction deoxygenation pretreatment can effectively upgrade bamboo into high-grade fuels with a lower content of water and higher energy density. Therefore, it is essential to establish the deoxygenation mechanism and oxygen migration characteristics during the bamboo torrefaction process, based on the properties of torrefied solid, gaseous, and liquid products. In this study, these three types of torrefied product (solid, gaseous, and liquid) were produced at different torrefaction temperatures (210, 240, 270 and 300 °C) by the tube furnace, TGA−FTIR, and Py−GC/MS. Results showed that following a series of deoxygenation reactions, the oxygen removal efficiency of bamboo reached a maximum of 28.52% at 300 °C, resulting in the highest HHV of 23.12 MJ kg−1. Oxygen in the torrefied solid product was released in the form of torrefied gaseous components (CO2, H2O and CO) and torrefied liquid oxygen-containing compounds (E.g. acids, phenols, furans and ketones). CO2 was the dominant oxygen carrier in the torrefied gaseous product, with oxygen distribution in the torrefied gaseous components ranked in the order: CO2 (82.1–86.6%) > CO (10.9–13.9%) > H2O (2.4–4.1%). In the torrefied liquid product, oxygen transferred to acids, furans, ketones and aldehydes was favored under lower torrefaction temperatures, while more oxygen was transferred to phenols under higher torrefaction temperatures.

New sight on the lignin torrefaction pretreatment: Relevance between the evolution of chemical structure and the properties of torrefied gaseous, liquid, and solid products

In order to reveal the deoxygenation mechanism of lignin torrefaction, the relevance between evolution of chemical structure of torrefied lignin and the properties of torrefied gaseous, liquid, and solid products was established in this study. Results showed that the contents of oxygen element, βO4 linkages, oxygen-containing functional groups (aliphatic OH, aliphatic COOH, aromatic OCH3) in lignin decreased with the increase of the torrefaction temperature from 210 to 300 °C. The oxygen removal efficiency of lignin torrefaction reached the maximum value of 25.53% at 300 °C. The removed oxygen in the torrefied lignin was transferred into the torrefied gaseous product (e.g. CO2, H2O, and CO) and torrefied liquid product (e.g. G-type and P-type phenols, acids). Among the torrefied gaseous products, CO2 was the dominant oxygen carrier, followed by CO and H2O. Among the torrefied liquid products, G-type phenols were the dominant oxygen carrier, followed by P-type phenols and acids.

Synthesis and characterization of Pt-, Pd-, and Ru-promoted Ni–Ce0.6Zr0.4O2 catalysts for efficient biodiesel production by deoxygenation of oleic acid

Herein, we prepared Pt-, Pd-, and Ru-promoted Ni–Ce0.6Zr0.4O2 catalysts with improved oleic acid deoxygenation performance and investigated their physicochemical properties by N2 adsorption-desorption, X-ray diffraction (XRD), NH3 temperature-programmed desorption (NH3-TPD), and X-ray photoelectron spectroscopy (XPS). Among the above catalysts, the highest oleic acid conversion, C9–C17 selectivity, and oxygen removal efficiency were observed for Pt/Ni–Ce0.6Zr0.4O2, which was mainly ascribed to its highest surface defect oxygen fraction and acidity.

Harvesting energy from leachates in microbial fuel cells using an anion exchange membrane

The aim of this work was to evaluate the performance of a single chamber microbial fuel cells (SC-MFCs) equipped with an anion exchange membrane, Zirfon membrane (ZF) with actual leachate as substrate, in terms of the volumetric power (PV) delivered and chemical oxygen removal efficiency (ηCOD). The SC-MFCs were loaded with three different mixtures of leachate with sulphate-reducing inocula (SR-I) as biocatalyst: 30% leachate + 70% SR-I (Period I); 70% leachate + 30% SR-I (Period II) and 50% leachate + 50% SR-I (Period III).From the start of the operation of the SC-MFC equipped with ZF, the PV values shown were encouraging: 4260 and 8050 mW m−3 for Periods I and II, respectively. Finally, in the Period III, the PV reached was up to 10 380 mW m−3, whereas the SC-MFC fitted with Nafion 117 membrane (NF) used as reference, delivered a substantially lower PV of only 104 mW m−3.In conclusion, membrane type played a significant role: the SC-MFC fitted with ZF in terms of PV outperformed the SC-MFC fitted with NF. The proportion of leachate and inoculum seemed to have a positive effect on the power delivery of only the MFC equipped with ZF, likely related to increased organic matter availability with increased concentration of leachate.

Application of a new ceramic hydrophobic membrane for providing CO2 in algal photobioreactor during cultivation of Arthrospira sp.

Biological sequestration of CO2 using microalgal route emerges as a promising option due to its cleaner approach which can be used to produce various forms of bioenergy. The current study reports on development of a new ceramic hydrophobic membrane and its application in an algal photobioreactor towards an efficient dissolution of CO2 during cultivation of Arthrospira sp. Clay-alumina based ceramic capillary support elements were coated with bentonite clay and surface modified using polydimethyl siloxane (PDMS) to impart hydrophobicity. The prepared membrane indicated pore size of 5.0nm with around 35.3% porosity and contact angle of 147°. A two-element membrane module having 150mm length, 3.16 outer diameter and 2.16mm inner diameter was used as a nano bubble sparger to provide CO2 in 1L of the culture medium and an enhanced overall mass transfer coefficient of about 38×10−4m/s was obtained using 19.5% CO2 gas mixture and 0.23m/s gas velocity. The membrane was efficient in removal of dissolved oxygen produced during photosynthesis, resulting in higher algal growth and higher CO2 sequestration. Algal growth of about 178.2g(dwt)/m3/day were obtained at 24h interval of CO2 supply in the photobioreactor and subsequent CO2 sequestration obtained was 13.99g/m3/h. Under optimized growth conditions the produced biomass yielded biodiesel content of about 5.82% of dry weight of algae. Application of the ceramic hydrophobic membrane thus enables enhanced mass transfer coefficient and dissolved oxygen removal efficiency making it suitable in photobioreactor application towards algal bio-sequestration of CO2 and subsequent biomass and biofuel production.

Electrochemical Oxygen Removal from Seawater in Industrial Scale Using Silver Cathode

In this study, electrochemical removal of oxygen from seawater in industrial scale is demonstrated. A test rig with an industrial scale electrochemical cell has been constructed and tested with filtrated oxygen rich seawater. The electrochemical cell was comprised of a silver mesh cathode and an iridium oxide anode with a cation exchange membrane. The effects of flow rate, pressure, and applied voltage on oxygen removal efficiency and resulting current were studied. Also, the differential pressure between the anode and cathode chambers affected the performance of the cell, and an overpressure of 0.20–0.30 bar in the anode chamber was optimal in order to obtain maximum oxygen removal. It was possible to achieve an oxygen concentration lower than 5 ppb in seawater at a flow rate of 5 L min–1. No scaling or biofilm problems were observed during a 200 h test period.