Tracy J. Benson

Looped carbon capturing and environmental remediation: case study of magnetic polypropylene nanocomposites

A waste-free process to recycle Fe@Fe2O3/polypropylene (PP) polymer nanocomposites (PNCs) is introduced to synthesize magnetic carbon nanocomposites (MCNCs) and simultaneously produce useful chemical species which can be utilized as a feedstock in petrochemical industry. The magnetic nanoparticles (NPs) are found to have an effective catalytic activity on the pyrolysis of PP. The PNCs (with a NP loading of 20.0 wt%) undergo a complete degradation with 2 h pyrolysis at 500 °C in a H2/Ar atmosphere and the degradation components exhibit a distribution of species with different numbers of carbon, while only 40% of pure PP is decomposed after applying the same pyrolytic conditions. The coked solid waste from the conventional process has been utilized as a carbon source to form a protective carbon shell surrounding the magnetic NPs. The magnetic carbon nanocomposites (MCNCs) pyrolyzed from PNCs containing 20.0 wt% NPs demonstrate extremely fast Cr(VI) removal from wastewater with the almost complete removal of Cr(VI) within 10 min. The pH effect on the Cr(VI) removal efficiency is investigated with a preferable value of 1–3. The adsorbent exhibits much higher adsorption capacity in acidic solutions than that in alkali solutions. The large saturation magnetization (32.5 emu g−1) of these novel magnetic carbon nanocomposites allows fast recycling of both the adsorbents and the adsorbed Cr(VI) from the liquid suspension in a more energetically and economically sustainable way by simply applying a permanent magnet. The significantly reduced treatment time required to remove the Cr(VI) makes these MCNCs promising for the efficient removal of the heavy metals from wastewater. Kinetic investigation reveals the pseudo-second-order adsorption of Cr(VI) on these novel magnetic carbon nanocomposite adsorbents.

Lipid storage compounds in raw activated sludge microorganisms for biofuels and oleochemicals production

Activated sludge contains a microbial population responsible for the biological treatment of wastewater. This microbial population mostly consists of heterothrophic bacteria which utilize the organic content of the wastewater for growth, either as part of their cellular structures or as energy and carbon storage compounds. These compounds are mostly lipidic in nature and are or could be important raw materials for a multitude of applications in biofuel and oleochemical industries. In this study, a municipal activated sludge was analyzed for lipid storage compounds and other compound classes present in significant concentrations. Three extraction techniques, namely; Bligh & Dyer (applied on dried and partially dewatered samples) and accelerated solvent extractions, were initially investigated to identify the one resulting in the highest gravimetric and biodiesel yields. The highest yields were obtained using the Bligh & Dyer of partially dewatered sludge samples and thus, the extracts from this extraction technique were subjected to a series of analytical procedures such as precipitation, solid phase extraction, thin layer chromatography (TLC), gas chromatography with flame ionization detector (GC-FID) and gas chromatography-mass spectrometry (GC-MS) to characterize the major compound classes present. Results indicated that the major compounds in the samples were polyhydroxyalkanoates, wax esters, steryl esters, triacylglycerides, free fatty acids, free sterols and phospholipids. Hydrocarbons, diacylglycerides and monoacylglycerides were also detected. These compounds are either synthesized by microorganisms or from exogenous contributions. Regardless of the source of these compounds, their persistent presence in activated sludge offers another feedstock for a wide range of applications.

Immobilization of triazabicyclodecene in surfactant modified Mg/Al layered double hydroxides

In recent years, layered double hydroxides (LDHs) have received much interest as host materials for the construction of organic–inorganic supramolecular structures by an anion exchange method. This study demonstrates the preparation of a series of solid base catalysts through attachment of triazabicyclodecene (TBD) to Mg/Al-LDH surfaces with different Mg/Al molar ratios (Mg/Al = 3, 4 and 5). A new three-stage approach was taken to obtain TBD-LDH materials: (i) an anionic surfactant, sodium dodecyl sulfate (SDS) was intercalated in parent LDH replacing nitrates from interlayer via anion exchange to widen the gallery of LDH, (ii) a silane coupling agent (3-glycidyloxypropyl) trimethoxysilane (3GPS) was used to attach TBD with the terminal glycidyl groups, and (iii) interlayer molecules from SDS-LDH gallery were replaced by the 3GPS moieties containing TBD. The surfactant modified Mg/Al LDH materials showed an increase in interlayer distance (maximum 44.8 A) as compared to unmodified Mg/Al LDH (8.8 A). Infrared and Raman spectroscopy results were in agreement with the proposed organic functionalized structure. Therefore, based on these observations, a schematic representation of the TBD functionalized LDH surface is also presented. The temperature programmed desorption (TPD) study on the different products showed approximately 3–5 times higher basic properties than those of pristine LDHs. Thermal decomposition was changed significantly after organic modification of LDHs. All TBD-LDHs are found to be effective catalysts for the transesterification of canola oil with dimethyl carbonate (DMC) for biofuel production under mild conditions (atmospheric pressure and 70 °C).

Catalytic Deoxygenation Chemistry: Upgrading of Liquids Derived from Biomass Processing

Abstract The composition of a typical pyrolysis oil is used to pose the problem of oxygen removal from this oil and to motivate a discussion of the different reactions for oxygen removal that are thermodynamically favored. From a consideration of this thermodynamics analysis of the favored reactions, the surface chemistry literature is surveyed to reveal those materials that allow the adsorption of oxygen-containing species. Included in this survey are experimental and theoretical studies. This consideration of adsorption of oxygen-containing species prompts a further examination of the literature of reaction mechanisms and reaction sequences to reveal the conventional pathways to remove oxygen from the substrates. Moreover, the literature of hydroprocessing is reviewed to show how traditional hydrodesulfurization catalysts have been studied as a hydrodeoxygenation (HDO) catalyst of the reactive species in pyrolysis oils. Furthermore, aqueous-phase reforming is discussed as an alternative to HDO.

Parametric Study on the Production of Renewable Fuels and Chemicals from Phospholipid-Containing Biomass

Heterogeneous catalytic cracking of lipids into transportation fuels and other specialty chemicals offers a unique opportunity to provide sustainable energy while utilizing the current petroleum infrastructure. This study addresses a possible route for the utilization of phospholipid-containing biomass for production of renewable fuels and chemicals. The first part of the study focused on reaction pathways associated with the catalytic cracking of model phospholipid into fuel-type compounds. The results indicated that phospholipid cracking proceeds via acid-catalyzed mechanisms, which resulted to cleavage of fatty acids and glycerol moieties. Microbial lipids, which contain large concentrations of phospholipids, are a potential non-food related feedstock to displace petroleum. Among possible sources of microbial lipids, activated sludge offers a distinct advantage for its availability and abundance at a potential fee. The second part of this work dealt with the conversion of activated sludge to chemicals of value as fuel components through fluidized-bed catalytic cracking. The effect of moisture level and catalyst loading were determined. Results indicated that moisture level of up to 15 % (weight) has no effect on total product yield. On the other hand, higher catalyst loading resulted to a higher yield of gaseous product. Significant coke deposition was inferred as indicated by the high proportion of phenolic compounds produced from pyrolytic reactions. The results of this study provide a potential route of utilizing bulk lipid feedstocks, without the removal of phosphorus-containing molecules, to produce fuel components.