Josephine M. Hill

A sponge-like luminescent coordination framework via an Aufbau approach

A luminescent mixed-metal coordination network with sponge-like sorption features is formed by stepwise assembly.

Pyrolysis of wood to biochar: increasing yield while maintaining microporosity.

The objective of this study was to determine if biochar yield could be increased by the deposition of volatile pyrolysis species within the bed during production, without negatively influencing the microporosity and adsorption properties. Aspen (Populus tremuloides) wood chips were loaded into three vertically stacked zones within a reactor and heated in nitrogen to temperatures between 420 and 650°C (i.e., pyrolyzed). The yield did increase from the zone at the reactor inlet to the subsequent zones as volatile species deposited and carbonized, and importantly, the carbonized deposits had a similar microporous structure and organic vapor uptake (1,1,1,2-tetrafluoroethane) to that of the primary biochar. Based on these results, bio-oil from previous runs at 600°C was recycled to the bed, which further increased the yield while maintaining the desirable adsorption properties of the biochar.

Barium oxide promoted Ni/YSZ solid-oxide fuel cells for direct utilization of methane

Conventional Ni/YSZ solid-oxide fuel cell (SOFC) anodes work well with hydrogen but require modification to tolerate hydrocarbon fuels and not accumulate carbon, which degrades cell performance and eventually damages the anode microstructure. In this work, barium oxide (BaO) was incorporated into Ni/YSZ anodes of SOFC by two different methodologies: impregnation and microwave irradiation. The performance of the BaO incorporated cells was measured in H2 and CH4 at 1073 K. With the impregnation technique, BaO was distributed both on Ni and YSZ grains. The BaO was stable on Ni but interacted with YSZ causing a morphological change and volume expansion of YSZ, which is problematic in this solid device. As such, an alternative method, based on microwave irradiation, was developed to selectively deposit BaO only on Ni and minimize the interaction between BaO and YSZ. The anode developed by this microwave irradiation technique showed comparable electrochemical performance in dry CH4 to that of conventional and impregnated anodes, and lower carbon accumulation than the conventional anode at 1073 K.

Removal and biodegradation of naphthenic acids by biochar and attached environmental biofilms in the presence of co-contaminating metals.

This study evaluated the efficacy of using a combined biofilm-biochar approach to remove organic (naphthenic acids (NAs)) and inorganic (metals) contaminants from process water (OSPW) generated by Canadas oil sands mining operations. A microbial community sourced from an OSPW sample was cultured as biofilms on several carbonaceous materials. Two biochar samples, from softwood bark (SB) and Aspen wood (N3), facilitated the most microbial growth (measured by protein assays) and were used for NA removal studies performed with and without biofilms, and in the presence and absence of contaminating metals. Similar NA removal was seen in 6-day sterile N3 and SB assays (>30%), while biodegradation by SB-associated biofilms increased NA removal to 87% in the presence of metals. Metal sorption was also observed, with up to four times more immobilization of Fe, Al, and As on biofilm-associated biochar. These results suggest this combined approach may be a promising treatment for OSPW.

Enhancing biochar yield by co-pyrolysis of bio-oil with biomass: Impacts of potassium hydroxide addition and air pretreatment prior to co-pyrolysis

The influence of KOH addition and air pretreatment on co-pyrolysis (600 °C) of a mixture of bio-oil and biomass (aspen wood) was investigated with the goal of increasing biochar yield. The bio-oil was produced as a byproduct of the pyrolysis of biomass and recycled in subsequent runs. Co-pyrolysis of the biomass with the recycled bio-oil resulted in a 16% mass increase in produced biochar. The yields were further increased by either air pretreatment or KOH addition prior to co-pyrolysis. Air pretreatment at 220 °C for 3 h resulted in the highest mass increase (32%) compared to the base case of pyrolysis of biomass only. No synergistic benefit was observed by combining KOH addition with air pretreatment. In fact, KOH catalyzed reactions that increased the bed temperature resulting in carbon loss via formation of CO and CO2.

Reducibility and toluene hydrogenation activity of nickel catalysts supported on γ-Al2O3 and κ-Al2O3

Metastable κ-Al2O3 was produced by thermal treatment of γ-Al2O3 and then Ni catalysts were prepared on both κ-Al2O3 and γ-Al2O3. Catalysts containing both low (5 wt.%) and high (20 wt.%) amounts of Ni were tested for activity towards toluene hydrogenation and characterized with X-ray diffraction, temperature-programmed reduction, and transmission electron microscopy. In order to better understand the behaviours of these catalysts, total reducibility, surface oxide reducibility, metal dispersion, and number of adsorption sites were compared with catalytic activity. Of these factors, only surface oxide reducibility was directly correlated with activity – the more easily the surface oxide was reduced the more active the catalyst was. Catalytic activity increased in the following order: Ni5/γ-Al2O3<Ni5/κ-Al2O3<Ni20/κ-Al2O3<Ni20/γ-Al2O3. The number of metallic active sites is usually considered as a major factor to determine the corresponding activity, but in this study reducibility changes in surface Ni sites were more influential to the activity than the number of active sites.

Highly cost-effective and sulfur/coking resistant VOx-grafted TiO2 nanoparticles as an efficient anode catalyst for direct conversion of dry sour methane in solid oxide fuel cells

In this work, we show that grafted metal oxide can be a highly cost-effective and active anode for solid oxide fuel cells for sour methane conversion. The developed electro-catalyst was composed of vanadium oxide grafted TiO2 nanoparticles (VOx/TiO2) infiltrated into a porous La0.4Sr0.5Ba0.1TiO3+δ electron-conductive composite. A number of chemisorbed vanadia species on TiO2 have been identified by XRD, FTIR, XPS and ToF-SIMS analyses; the morphologies of grafted TiO2 nanoparticles were characterized using SEM and TEM. The thermal stability of vanadia was greatly enhanced due to strong binding interaction with the support. In the chemical activity investigation using a fixed bed catalytic reactor, VOx/TiO2 showed significantly improved activity towards sour methane gas (0.5% H2S + CH4) oxidation in a diluted stream of oxygen. The electrochemical activity was determined using a SOFC that employed the VOx/TiO2 infiltrated titanate anode. This cell had a maximum power density of ∼160 mW cm−2 and a non-ohmic polarization resistance of <1 Ω cm2 in 0.5% H2S + CH4. Additionally, the performance of the novel anode material did not degrade during the 24 h test at 0.7 V with VOx/TiO2 suppressing coke formation on the anode.

Activation of Aspen Wood with Carbon Dioxide and Phosphoric Acid for Removal of Total Organic Carbon from Oil Sands Produced Water: Increasing the Yield with Bio-Oil Recycling

Several samples of activated carbon were prepared by physical (CO2) and chemical (H3PO4) activation of aspen wood and tested for the adsorption of organic compounds from water generated during the recovery of bitumen using steam assisted gravity drainage. Total organic carbon removal by the carbon samples increased proportionally with total pore volume as determined from N2 adsorption isotherms at −196 °C. The activated carbon produced by CO2 activation had similar removal levels for total organic carbon from the water (up to 70%) to those samples activated with H3PO4, but lower yields, due to losses during pyrolysis and activation. A method to increase the yield when using CO2 activation was proposed and consisted of recycling bio-oil produced from previous runs to the aspen wood feed, followed by either KOH addition (0.48%) or air pretreatment (220 °C for 3 h) before pyrolysis and activation. By recycling the bio-oil, the yield of CO2 activated carbon (after air pretreatment of the mixture) was increased by a factor of 1.3. Due to the higher carbon yield, the corresponding total organic carbon removal, per mass of wood feed, increased by a factor of 1.2 thus improving the overall process efficiency.

Ni Promotion of WP/SiO2 Catalysts for Pyridine Hydrodenitrogenation

WP/SiO2 catalysts promoted with Ni were prepared by wet impregnation with various molar ratios of Ni to W and then evaluated in the reaction of pyridine hydrodenitrogenation for pyridine conversion and product selectivity. The addition of Ni to the WP/SiO2 catalysts resulted in increased pyridine conversion and selectivity to pentane. The molar ratios of Ni:W:P are important, because nickel and tungsten compete for phosphorous and form WP, W3O, Ni2P and/or W crystals.Graphical Abstract

Impact of Pore Size on Fenton Oxidation of Methyl Orange Adsorbed on Magnetic Carbon Materials: Trade-Off between Capacity and Regenerability

The economic cleanup of wastewater continues to be an active area of research. In this study, the influence of pore size on regeneration by Fenton oxidation for carbon materials with adsorbed methyl orange (MO) was investigated. More specifically three carbon supports, with pore sizes ranging from mainly microporous to half microporous-half mesoporous to mainly mesoporous, were impregnated with γ-Fe2O3 to make them magnetic and easy to separate from solution. The carbon samples were characterized before adsorption and after regeneration with hydrogen peroxide at 20 °C. In addition, adsorption kinetics and isotherms were collected, and the Weber-Morris intraparticle diffusion model and Freundlich isotherm model fit to the data. The adsorption capacity increased with increasing microporosity while the regeneration efficiency increased with increasing mesoporosity. Further experiments with varying regeneration and adsorption conditions suggested that the regeneration process may be kinetically limited. The MO adsorbed in the micropores was strongly adsorbed and difficult to remove unlike the MO adsorbed in the mesopores, which could be reacted under relatively mild conditions. Thus, there was a trade-off between adsorption capacity and regeneration.