Hossein Toghiani

Biodiesel production by in situ transesterification of municipal primary and secondary sludges

The potential of using municipal wastewater sludges as a lipid feedstock for biodiesel production was investigated. Primary and secondary sludge samples obtained from a municipal wastewater treatment plant in Tuscaloosa, AL were freeze-dried and subjected to an acid-catalyzed insitu transesterification process. Experiments were conducted to determine the effects of temperature, sulfuric acid concentration, and mass ratio of methanol to sludge on the yield of fatty acid methyl esters (FAMEs). Results indicated a significant interactive effect between temperature, acid concentration, and methanol to sludge mass ratio on the FAME yield for the insitu transesterification of primary sludge, while the FAME yield for secondary sludge was significantly affected by the independent effects of the three factors investigated. The maximum FAME yields were obtained at 75 degrees C, 5% (v/v) H(2)SO(4), and 12:1 methanol to sludge mass ratio and were 14.5% and 2.5% for primary and secondary sludge, respectively. Gas chromatography (GC) analysis of the FAMEs revealed a similar fatty acid composition for both primary and secondary sludge. An economic analysis estimated the cost of

Adsorption of precious metal ions onto electrochemically oxidized carbon fibers

3.23/gallon for a neat biodiesel obtained from this process at an assumed yield of 10% FAMEs/dry weight of sludge.

Vapor-liquid equilibria for methyl tert-butyl ether + methanol and tert-amyl methyl ether + methanol

Electrochemically oxidized carbon fibers (ECF) adsorbed a prodigious amount of Ag+ in contrast to oxygen plasma and nitric acid treated carbon fibers. The amount of adsorbed Ag+ reached 3700 μmol/g after 5652 C/g of electrochemical oxidation. This value approaches the 4050 μmol/g of Ag+ which adsorbed onto steam-activated Kenaf-based carbon (with a surface area of 1284 m2/g determined by N2/BET) under the same adsorption conditions. ECF oxidized to 9540 C/g adsorbed more than its own weight of Ag+ (12 608 μmol/g). These fibers exhibited a surface area of 115 m2/g (CO2–DR). Two different reactions occurred during Ag+ adsorption. These reactions were ion exchange adsorption between Ag+ and acidic functions (carboxyl) and redox adsorption between Ag+ and reducing functions such as catechol groups on these electrochemically oxidized fibers (ECF). The redox capability was expressed by the reaction electric potential (E) using the Nernst equation. High resolution XPS C 1s spectra of ECFs (level of oxidation 5300 C/g), before and after Ag+ adsorption, showed that the carbon atoms present in phenolic, alcohol or ether groups and those present in carbonyl or quinone groups increased after Ag+ adsorption. X-ray diffraction and X-ray photoelectron spectroscopy (XPS) Ag 3d spectra of the ECF showed that adsorbed Ag+ was reduced to Ag0 after both Ag+ adsorption and subsequent post-heat treatment of the fibers under N2 at 550°C for 30 min. Only about one-third as much Au3+ adsorption occurred versus the extent of electrochemical oxidation as was observed for Ag+. This ratio matches the requirement that three electrons are required to convert Au3+ to Au0 versus one to convert Ag+ to Ag. High resolution angle resolved XPS (ARXPS) Pd 3d and Pt 4f spectra show that there are two different Pd oxidation states and three different Pt oxidation states present after adsorption of Pd2+ and Pt2+ onto ECF. The peak areas as a function of take off angle showed that substantial amounts of Pd0 and Pt0 are present in addition to Pd2+ and Pt2+ and Pt4+ on the outermost surface regions of oxidized fibers.

Optical fiber evanescent wave absorption spectrometry of nanocrystalline tin oxide thin films for selective hydrogen sensing in high temperature gas samples

Vapor-liquid equilibrium data are reported for the binary systems MTBE/methanol and TAME/methanol. These data were obtained using a modified Stage-Muller equilibrium still. For the MTBE/methanol system, isobaric data at 53.33 and 101.33 kPa are given as are isothermal data at 313.15 and 333.15 K. Results at 101.33 kPa are in excellent agreement with available literature data. For the TAME/methanol system, isothermal data at 333.15 and 343.15 K are reported. A search of the literature revealed no isothermal data available for the TAME/methanol binary pair. Pure component vapor pressures were measured in the same apparatus and correlated using the Antoine equation.

Characterization of K2CO3/Co-MoS2 catalyst by XRD, XPS, SEM, and EDS

SnO(2) nanocrystalline material was prepared with a sol-gel process and thin films of the nanocrystalline SnO(2) were coated on the surface of bent optical fiber cores for gas sensing. The UV/vis absorption spectrometry of the porous SnO(2) coating on the surface of the bent optical fiber core exposed to reducing gases was investigated with a fiber optical spectrometric method. The SnO(2) film causes optical absorption signal in UV region with peak absorption wavelength at around 320 nm when contacting H(2)-N(2) samples at high temperatures. This SnO(2) thin film does not respond to other reducing gases, such as CO, CH(4) and other hydrocarbons, at high temperatures within the tested temperature range from 300 degrees C to 800 degrees C. The response of the sensing probe is fast (within seconds). Replenishing of the oxygen in tin oxide was demonstrated by switching the gas flow from H(2)-N(2) mixture to pure nitrogen and compressed air. It takes about 20 min for the absorption signal to decrease to the baseline after the gas sample was switched to pure nitrogen, while the absorption signal decreased quickly (in 5 min) to the baseline after switching to compressed air. The adhesion of tin oxide thin films is found to be improved by pre-coating a thin layer of silica gel on the optical fiber. Adhesion increases due to increase interaction of optical fiber surface and the coated silica gel and tin oxide film. Optical absorption spectra of SnO(2) coating doped with 5 wt% MoO(3) were observed to change and red-shifted from 320 nm to 600 nm. SnO(2) thin film promoted with 1 wt% Pt was found to be sensitive to CH(4) containing gas.

Classical micromechanics modeling of nanocomposites with carbon nanofibers and interphase

Abstract MoS 2 , Co–MoS 2 and K 2 CO 3 /Co–MoS 2 catalysts have been characterized by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). XRD analysis indicates that Co–MoS 2 is a primary phase in K 2 CO 3 /Co–MoS 2 catalyst and the diffraction lines of Co–MoS 2 are not changed by the addition of K 2 CO 3 . Co 9 S 8 phase is not present at Co/Mo mole ratio of 0.5 using a co-precipitation method for preparation of cobalt–molybdenum catalyst. The binding energies (BEs) of chemical species present on the surface of the catalysts are compared through the course of catalyst preparation. K 2 CO 3 /Co–MoS 2 catalyst has been investigated as a function of dispersion of K on the surface and exposure to a mixture of carbon monoxide and hydrogen (syngas) by scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS). The distribution of potassium on the surface of the K-promoted catalyst is not uniform.

Effect of Temperature on the Shear-Thickening Behavior of Fumed Silica Suspensions

A micromechanics parametric study was performed to investigate the effect of carbon nanofiber morphology (i.e. hollow vs. solid cross-section), nanofiber waviness, and both nanofiber–resin interphase properties and dimensions on bulk nanocomposite elastic moduli. Mori–Tanaka and self-consistent models were developed for composites containing heterogeneities with multilayered coatings. For a given nanofiber axial force–displacement relationship, the elastic modulus for hollow nanofibers can significantly exceed that for solid nanofibers resulting in notable differences in bulk nanocomposite properties. In addition, the development of a nanofiber–resin interphase had a notable effect on the bulk elastic moduli. Consistent with results from the literature, small degrees of nanofiber waviness resulted in a significant decrease in effective composite properties.

Dynamic mechanical analysis and optimization of vapor-grown carbon nanofiber/vinyl ester nanocomposites using design of experiments

Shear-thickening fluids (STFs) can be subjected to a significant temperature variation in many applications. Polymeric or oligomeric fluids are commonly used as suspending media for STFs. Because the viscosities of polymeric fluids are strongly temperature-dependent, large temperature changes can profoundly affect the shear-thickening responses. Here, the effect of temperature on the shear-thickening behavior of four low-molecular-weight polymeric glycols/fumed silica suspensions is reported. The dispersed-phase volume fraction, its surface chemistry, and the chemical compositions of the suspending media were varied. These factors influence the viscosity and the interactions between the suspended particles and the suspending media. Fumed silica particles with two different silanol-group surface densities were suspended in the polymeric glycols, where these silanol surface groups formed hydrogen bonds with the suspending medias glycols and internal oxygen atoms. Steady-shear experiments were performed over a temperature range spanning approximately 100 °C. The critical shear rate for the onset of shear thickening decreased with decreasing temperature. The critical shear rates were inversely proportional to the viscosity of the pure suspending media over these same temperature ranges. The response of STFs to varying both the temperature and shear rate investigated here will help to design application-specific STFs. Mitigation of a hypervelocity (6.81 km/s) impact on an aluminum facesheet sandwich composite filled with one of these STFs was demonstrated.

Hydroformylation of α- and β-pinene catalysed by rhodium and cobalt carbonyls

A design of experiments approach demonstrated how four formulation and processing factors (i.e., nanofiber type, use of dispersing agent, mixing method, and nanofiber weight fraction) affected the dynamic mechanical properties of carbon nanofiber/vinyl ester nanocomposites. Only <0.50 parts of nanofiber per hundred parts resin produced a 20% increase in the storage modulus vs. that of the neat cured resin. Statistical response surface models predicted nanocomposite storage and loss moduli as a function of the four factors and their interactions. Nanofiber type and weight fraction were the key interacting factors influencing the mean storage modulus. Nanofiber weight fraction, mixing method, and dispersing agent had coupled effects on the mean loss modulus. Employing this methodology, optimized nanocomposite properties can be predicted as a function of nanocomposite formulation and processing.

Effective property estimates for composites containing multiple nanoheterogeneities: Part II nanofibers and voids

Abstract α- and β-Pinene were hydroformylated to their respective aldehydes and alcohols at 60–130°C and 600 psi of CO/H 2 . Employing Rh 6 (CO) 16 as a catalyst precursor the main product is 10-formylpinane, 2 . In contrast, mononuclear rhodium complexes containing phosphine ligands typically give 3-formylpinane, 1 , as the major product. 3-Formylpinane, 1 , was also the main product upon employing either Co 2 (CO) 8 or phosphine-modified Rh 6 (CO) 16 . The turnover frequency drops sharply as the total rhodium concentration increases upon using Rh 6 (CO) 16 to catalyze α-pinene hydroformylation at 130°C and 600 psi of H 2 /CO (1:1). This shows that cluster fragmentation occurs to generate the active catalytic species of lower nuclearity. Furthermore, the product distribution at equivalent α-pinene conversions remains the same at different total rhodium concentrations under Rh 6 (CO) 16 catalysis, suggesting there is only (predominantly) one catalytically active species operating in the reaction. Hydroformylation with triphenylphosphite-modified Rh 6 (CO) 16 was initially faster but the catalyst life is short due to hydrogenolysis of triphenylphosphite which produces phenol. Hydrogenation of α- and β-pinene (Pd/C, 1 atm H 2 , ambient temperature) generated the two pinane isomers, 10 and 11 , which result from the hydrogen addition to the two faces of the double bond. The only hydrogenation byproduct detected during Rh 6 (CO) 16 -catalyzed hydroformylations was 11 where hydrogen addition occurred to the face of the double bond which was cis to the C(CH 3 ) 2 bridge. Use of the mixed metal carbonyl systems: CO 2 (CO) 8 /Rh 6 (CO) 16 , CO 2 (CO) 8 /Ru 3 (CO) 12 , Rh 6 (CO) 16 /Ru 3 (CO) 12 /PPh 3 and CO 2 (CO) 12 /Rh 6 (CO) 16 /PPh 3 in toluene at 100°C and 600 psi H 2 /CO = 1:1 did not lead to any synergistic rate enhancements in the hydroformylation of α-pinene.