Abstract: Nano fibers produced by electrospinning are of industrial and scientific attention due to their special characteristics such as long length, small diameter and high surface area. Applications of electrospun structures in nanotechnology are included tissue scaffolds, fibers for drug delivery, composite reinforcement, chemical sensing, enzyme immobilization, membrane-based filtration, protective clothing, catalysis, solar cells, electronic devices and others. Many polymer and ceramic precursor nano fibers have been successfully electrospun with diameters in the range from 1 nm to several microns. The process is complex so that fiber diameter is influenced by various material, design and operating parameters. The objective of this work is to apply genetic algorithm on the parameters of electrospinning which have the most significant effect on the nano fiber diameter to determine the optimum parameter values before doing experimental set up. Effective factors including initial polymer concentration, initial jet radius, electrical potential, relaxation time, initial elongation, viscosity and distance between nozzle and collector are considered to determine finest diameter which is selected by user.
Abstract: Three dimensional nanostructure materials have attracted the attention of many researches because the possibility to apply them for near future devices in sensors, catalysis and energy related. Tin dioxide is the most used material for gas sensing because its three-dimensional nanostructures and properties are related to the large surface exposed to gas adsorption. We propose the use of branch SnO2 nanowhiskers in interaction with ethanol. All Sn atoms are symmetric. The total energy, potential energy and Kinetic energy calculated for interaction between SnO2 and ethanol in different distances and temperatures. The calculations achieved by methods of Langevin Dynamic and Mont Carlo simulation. The total energy increased with addition ethanol molecules and temperature so interactions between them are endothermic.
Abstract: This research project aims to investigate difference in
relative rates concerning phosphoryl transfer relevant to biological
catalysis of DNA and RNA in the pH-independent reactions.
Activated Models of DNA and RNA for alkyl-aryl phosphate diesters
(with 4-nitrophenyl as a good leaving group) have successfully been
prepared to gather kinetic parameters. Eyring plots for the pH–
independent hydrolysis of 1 and 2 were established at different
temperatures in the range 100–160 °C. These measurements have
been used to provide a better estimate for the difference in relative
rates between the reactivity of DNA and RNA cleavage. Eyring plot
gave an extrapolated rate of kH2O = 1 × 10-10 s -1 for 1 (RNA model)
and 2 (DNA model) at 25°C. Comparing the reactivity of RNA
model and DNA model shows that the difference in relative rates in
the pH-independent reactions is surprisingly very similar at 25°. This
allows us to obtain chemical insights into how biological catalysts
such as enzymes may have evolved to perform their current
functions.
Abstract: This study investigates the in-situ regeneration of deactivated Pt-Pd catalyst in a laboratory-scale catalysis reactor. Different regeneration conditions are tested and the activity and characteristics of regenerated catalysts are analyzed. Experimental results show that the conversion efficiencies of C3H6 by different regenerated Pt-Pd catalysts were significantly improved from 77%, 55% and 41% to 86%, 98% and 99%, respectively. The best regeneration conditions was 52ppm ozone, 500oC, and 10min. Regeneration temperature has more influences than ozone concentration and regeneration time. With the comparisons of characteristics of deactivated catalyst and regenerated catalyst, the major poison species (carbon, metals, chloride, and sulfate) on the spent catalysts can be effectively removed by ozone regeneration.
Abstract: The acidity of different raw Jordanian clays
containing zeolite, bentonite, red and white kaolinite and diatomite
was characterized by means of temperature programmed desorption
(TPD) of ammonia, conversion of 2-methyl-3-butyn-2-ol (MBOH),
FTIR and BET-measurements. FTIR spectra proved presence of
silanol and bridged hydroxyls on the clay surface. The number of
acidic sites was calculated from experimental TPD-profiles. We
observed the decrease of surface acidity correlates with the decrease
of Si/Al ratio except for diatomite. On the TPD-plot for zeolite two
maxima were registered due to different strength of surface acidic
sites. Values of MBOH conversion, product yields and selectivity
were calculated for the catalysis on Jordanian clays. We obtained that
all clay samples are able to convert MBOH into a major product
which is 3-methyl-3-buten-1-yne (MBYNE) catalyzed by acid
surface sites with the selectivity close to 70%. There was found a
correlation between MBOH conversion and acidity of clays
determined by TPD-NH3, i.e. the higher the acidity the higher the
conversion of MBOH. However, diatomite provided the lowest
conversion of MBOH as result of poor polarization of silanol groups.
Comparison of surface areas and conversions revealed the highest
density of active sites for red kaolinite and the lowest for zeolite and
diatomite.
Abstract: Cu-mesoporous TiO2 is developed for removal acid
odor cooperated with ozone assistance and online- regeneration
system with/without UV irradiation (all weather) in study. The results
showed that Cu-mesoporous TiO2 present the desirable adsorption
efficiency of acid odor without UV irradiation, due to the larger
surface area, pore sizeand the additional absorption ability provided by
Cu. In the photocatalysis process, the material structure also benefits
Cu-mesoporous TiO2 to perform the more outstanding efficiency on
degrading acid odor. Cu also postponed the recombination of
electron-hole pairs excited from TiO2 to enhance photodegradation
ability. Cu-mesoporous TiO2 could gain the conspicuous increase on
photocatalysis ability from ozone assistance, but without any benefit
on adsorption. In addition, the online regeneration procedure could
process the used Cu-mesoporous TiO2 to reinstate the adsorption
ability and maintain the photodegradtion performance, depended on
scrubbing, desorping acid odor and reducing Cu to metal state.
Abstract: New lead-free ferroelectric relaxor ceramics were
prepared by conventional solid-state synthesis in the BaTiO3-Bi2O3-
Y2O3 systems. Some of these ceramics present a ferroelectric relaxor
with transition temperature close to room temperature. These new
materials are very interesting for applications and can replace leadbased
ceramic to prevent the toxic pollutions during the preparation
state. In the other hand, the energy band diagram shows the
potentiality of these compounds for the solar energy conversion.
Thus, some compositions have been tested successfully for H2
production upon visible light. The best activity occurs in alkaline
media with a rate evolution of about 0.15 mL g-1 mn-1 and a quantum
yield of 1% under polychromatic light.
Abstract: Carbonic anhydrases (CAs) has been focused as
biological catalysis for CO2 sequestration process because it can
catalyze the conversion of CO2 to bicarbonate. Here, codon-optimized
sequence of α type-CA cloned from Duneliala species. (DsCAopt) was
constructed, expressed, and characterized. The expression level in E.
coli BL21(DE3) was better for codon-optimized DsCAopt than intact
sequence of DsCAopt. DsCAopt enzyme shows high-stability at pH
7.6/10.0. In final, we demonstrated that in the Ca2+ solution, DsCAopt
enzyme can catalyze well the conversion of CO2 to CaCO3, as the
calcite form.
Abstract: The accelerated sonophotocatalytic degradation of
Reactive Red (RR) 120 dye under visible light using dye sensitized
TiO2 activated by ultrasound has been carried out. The effect of
sonolysis, photocatalysis and sonophotocatalysis under visible light
has been examined to study the influence on the degradation rates by
varying the initial substrate concentration, pH and catalyst loading to
ascertain the synergistic effect on the degradation techniques.
Ultrasonic activation contributes degradation through cavitation
leading to the splitting of H2O2 produced by both photocatalysis and
sonolysis. This results in the formation of oxidative species, such as
singlet oxygen (1O2) and superoxide (O2
-●) radicals in the presence of
oxygen. The increase in the amount of reactive radical species which
induce faster oxidation of the substrate and degradation of
intermediates and also the deaggregation of the photocatalyst are
responsible for the synergy observed under sonication. A
comparative study of photocatalysis and sonophotocatalysis using
TiO2, Hombikat UV 100 and ZnO was also carried out.
Abstract: Heterogeneous catalysis is vital for a number of
chemical, refinery and pollution control processes. The use of
catalyst pellets of hollow cylindrical shape provide several distinct
advantages over other common shapes, and can therefore help to
enhance conversion levels in reactors. A better utilization of the
catalytic material is probably most notable of these features due to
the absence of the pellet core, which helps to significantly lower the
effect of the internal transport resistance. This is reflected in the
enhancement of the effectiveness factor. For the case of the first order
irreversible kinetics, a substantial increase in the effectiveness factor
can be obtained by varying shape parameters. Important shape
parameters of a finite hollow cylinder are the ratio of the inside to the
outside radii (κ) and the height to the diameter ratio (γ). A high value
of κ the generally helps to enhance the effectiveness factor. On the
other hand, lower values of the effectiveness factors are obtained
when the dimension of the height and the diameter are comparable.
Thus, the departure of parameter γ from the unity favors higher
effectiveness factor. Since a higher effectiveness factor is a measure
of a greater utilization of the catalytic material, higher conversion
levels can be achieved using the hollow cylindrical pellets possessing
optimized shape parameters.
Abstract: Ionic liquids are well known as green solvents, reaction media and catalysis. Here, three different sulfonic acid functional ionic liquids prepared in the laboratory are used as catalysts in alkylation of p-cresol with tert-butyl alcohol. The kinetics on each of the catalysts was compared and a kinetic model was developed based on the product distribution over these catalysts. The kinetic parameters were estimated using Marquadt's algorithm to minimize the error function. The Arrhenius plots show a curvature which is best interpreted by the extended Arrhenius equation.
Abstract: Electrospinning is a broadly used technology to obtain
polymeric nanofibers ranging from several micrometers down to
several hundred nanometers for a wide range of applications. It offers
unique capabilities to produce nanofibers with controllable porous
structure. With smaller pores and higher surface area than regular
fibers, electrospun fibers have been successfully applied in various
fields, such as, nanocatalysis, tissue engineering scaffolds, protective
clothing, filtration, biomedical, pharmaceutical, optical electronics,
healthcare, biotechnology, defense and security, and environmental
engineering. In this study, polyurethane nanofibers were obtained
under different electrospinning parameters. Fiber morphology and
diameter distribution were investigated in order to understand them
as a function of process parameters.
Abstract: Lutein is a dietary oxycarotenoid which is found
to reduce the risks of Age-related Macular Degeneration
(AMD). Supercritical fluid extraction of lutein esters from
marigold petals was carried out and was found to be much
effective than conventional solvent extraction. The
saponification of pre-concentrated lutein esters to produce free
lutein was studied which showed a composition of about 88%
total carotenoids (UV-VIS spectrophotometry) and 90.7%
lutein (HPLC). The lipase catalyzed hydrolysis of lutein esters
in conventional medium was investigated. The optimal
temperature, pH, enzyme concentration and water activity
were found to be 50°C, 7, 15% and 0.33 respectively and the
activity loss of lipase was about 25% after 8 times re-use in at
50°C for 12 days. However, the lipase catalyzed hydrolysis of
lutein esters in conventional media resulted in poor
conversions (16.4%).
Abstract: The systematic manipulations of shapes and sizes of
inorganic compounds greatly benefit the various application fields
including optics, magnetic, electronics, catalysis and medicine.
However shape control has been much more difficult to achieve.
Hence exploration of novel method for the preparation of differently
shaped nanoparticles is challenging research area. II-VI group of
semiconductor cadmium sulphide (CdS) nanostructure with different
morphologies (such as, acicular like, mesoporous, spherical shapes)
and of crystallite sizes vary from 11 to 16 nm were successfully
synthesized by chemical aqueous precipitation of Cd2+ ions with
homogeneously released S2- ions from decomposition of cadmium
sulphate (CdSO4) and thioacetamide (CH3CSNH2) by annealing at
different radiations (microwave, ultrasonic and sunlight) with matter
and systematic research has been done for various factors affecting
the controlled growth rate of CdS nanoparticles. The obtained
nanomaterials have been characterized by X-ray Diffraction (XRD),
Fourier Transform Infrared Spectroscopy (FTIR),
Thermogravometric (DSC-TGA) analysis and Scanning Electron
Microscopy (SEM). The result indicates that on increasing the
reaction time particle size increases but on increasing the molar ratios
grain size decreases.
Abstract: Carboneous catalytical methane decomposition is an
attractive process because it produces two valuable products:
hydrogen and carbon. Furthermore, this reaction does not emit any
green house or hazardous gases. In the present study, experiments
were conducted in a thermo gravimetric analyzer using Fluka 05120
as carboneous catalyst to analyze its effectiveness in methane
decomposition. Various temperatures and methane partial pressures
were chosen and carbon mass gain was observed as a function of
time. Results are presented in terms of carbon formation rate,
hydrogen production and catalytical activity. It is observed that there
is linearity in carbon deposition amount by time at lower reaction
temperature (780 °C). On the other hand, it is observed that carbon
and hydrogen formation rates are increased with increasing
temperature. Finally, we observed that the carbon formation rate is
highest at 950 °C within the range of temperatures studied.
Abstract: Sol-gel method has been used to fabricate
nanocomposite films on glass substrates composed halloysite clay
mineral and nanocrystalline TiO2. The methodology for the synthesis
involves a simple chemistry method utilized nonionic surfactant
molecule as pore directing agent along with the acetic acid-based solgel
route with the absence of water molecules. The thermal treatment
of composite films at 450oC ensures elimination of organic material
and lead to the formation of TiO2 nanoparticles onto the surface of
the halloysite nanotubes. Microscopy techniques and porosimetry
methods used in order to delineate the structural characteristics of the
materials. The nanocomposite films produced have no cracks and
active anatase crystal phase with small crystallite size were deposited
on halloysite nanotubes. The photocatalytic properties for the new
materials were examined for the decomposition of the Basic Blue 41
azo dye in solution. These, nanotechnology based composite films
show high efficiency for dye’s discoloration in spite of different
halloysite quantities and small amount of halloysite/TiO2 catalyst
immobilized onto glass substrates. Moreover, we examined the
modification of the halloysite/TiO2 films with silver particles in order
to improve the photocatalytic properties of the films. Indeed, the
presence of silver nanoparticles enhances the discoloration rate of the
Basic Blue 41 compared to the efficiencies obtained for unmodified
films.
Abstract: The paper reports the preparation and photocatalytic
activity of ZnO/SnO2 and SnO2 nanoparticles. These nanoparticles
were synthesized by hydrothermal method. The products were
characterized by X-ray diffraction (XRD) and scanning electron
microscopy (SEM). Their grain sizes are about 50-100 nm. The
photocatalytic activities of these materials were investigated for
congo red removal from aqueous solution under UV light irradiation.
It was shown that the use of ZnO/SnO2 as photocatalyst have better
photocatalytic activity for degradation of congo red than SnO2 or
TiO2 (anatase, particle size: 30nm) alone.