Abstract: In the work presented here, nitrogen-doped graphene materials were synthesized and used as metal-free electrocatalysts for oxygen reduction reaction (ORR) under alkaline conditions. Paraphenylenediamine was used as N precursor. The N-doped graphene was synthesized under hydrothermal treatment at 200°C. All the materials have been characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Transmission electron microscopy (TEM) and X-ray photo-electron spectroscopy (XPS). Moreover, for electrochemical evaluation of samples, Rotating Disk electrode (RDE) and Cyclic Voltammetry techniques (CV) were employed. The resulting material exhibits an outstanding catalytic activity for the oxygen reduction reaction (ORR) as well as excellent resistance towards methanol crossover effects, indicating their promising potential as ORR electrocatalysts for alkaline fuel cells.
Abstract: The transesterification of dimethyl malonate (DMM)
with phenol has been studied in vapour phase over cordierite
honeycomb coated with solid acid catalysts such as ZrO2,
Mo(VI)/ZrO2 and SO42-/ZrO2. The catalytic materials were prepared
honeycomb coated, powder forms, and characterized for their total
surface acidity by NH3-TPD and crystalinity by powder XRD
methods. Phenyl methyl malonate (PMM) and diphenyl malonate
(DPM) were obtained as the reaction products. A good conversion of
DMM (up to 82%) of MPM with 95% selectivity was observed when
the reactions were carried out at a catalyst bed temperature of 200 °C
and flow-rate of 10 mL/h in presence of Mo(VI)/ZrO2 as catalyst.
However, over SO4^2-/ZrO2 catalyst, the yield of DPM was found to be
higher. The results have been interpreted based on the variation of
acidic properties and powder XRD phases of zirconia on
incorporation of Mo(VI) or SO42– ions. Transesterification reactions
were also carried out over powder forms of the catalytic materials
and the yield of the desired phenyl ester products were compared
with that of the HC coated catalytic materials. The solid acids were
found to be reusable when used for at least 5 reaction cycles.
Abstract: The world crude oil demand is projected to rise to 108.5 million bbl/d by the year 2035. With reserves estimated at 869 billion tonnes worldwide, coal remains an abundant resource. The aim of this work was to produce a high value hydrocarbon liquid product using a Direct Coal Liquefaction (DCL) process at, relatively mild operating conditions. Via hydrogenation, the temperature-staged approach was investigated in a dual reactor lab-scale pilot plant facility. The objectives included maximising thermal dissolution of the coal in the presence of tetralin as the hydrogen donor solvent in the first stage with 2:1 and 3:1 solvent: coal ratios. Subsequently, in the second stage, hydrogen saturation, in particular, hydrodesulphurization (HDS) performance was assessed. Two commercial hydrotreating catalysts were investigated viz. NickelMolybdenum (Ni-Mo) and Cobalt-Molybdenum (Co-Mo). GC-MS results identified 77 compounds and various functional groups present in the first and second stage liquid product. In the first stage 3:1 ratios and liquid product yields catalysed by magnetite were favoured. The second stage product distribution showed an increase in the BTX (Benzene, Toluene, Xylene) quality of the liquid product, branched chain alkanes and a reduction in the sulphur concentration. As an HDS performer and selectivity to the production of long and branched chain alkanes, Ni-Mo had an improved performance over Co-Mo. Co-Mo is selective to a higher concentration of cyclohexane. For 16 days on stream each, Ni-Mo had a higher activity than Co-Mo. The potential to cover the demand for low–sulphur, crude diesel and solvents from the production of high value hydrocarbon liquid in the said process, is thus demonstrated.
Abstract: Oxygen Reduction Reaction (ORR) performance of
iron and nitrogen co-doped porous carbon nanoparticles (Fe-NPC)
with various physical and (electro) chemical properties have been
investigated. Fe-NPC nanoparticles are synthesized via a facile
soft-templating procedure by using Iron (III) chloride hexa-hydrate as
iron precursor and aminophenol-formaldehyde resin as both carbon
and nitrogen precursor. Fe-NPC nanoparticles shows high surface area
(443.83 m2g-1), high pore volume (0.52 m3g-1), narrow mesopore size
distribution (ca. 3.8 nm), high conductivity (IG/ID=1.04), high kinetic
limiting current (11.71 mAcm-2) and more positive onset potential
(-0.106 V) compared to metal-free NPC nanoparticles (-0.295V)
which make it high efficient ORR metal-free catalysts in alkaline
solution. This study may pave the way of feasibly designing iron and
nitrogen containing carbon materials (Fe-N-C) for highly efficient
oxygen reduction electro-catalysis.
Abstract: As a by-product of the biodiesel industries, glycerol
has been vastly generated which surpasses the market demand. It is
imperative to develop an efficient glycerol valorization processes in
minimizing the net energy requirement and intensifying the biodiesel
production. In this study, base-catalyzed transesterification of
glycerol with dimethyl carbonate using microwave irradiation as
heating method to produce glycerol carbonate was conducted by
varying grades of glycerol, i.e. 70%, 86% and 99% purity, that is
obtained from biodiesel plant. Metal oxide catalysts were used with
varying operating parameters including reaction time, DMC/glycerol
molar ratio, catalyst weight %, temperature and stirring speed. From
the study on the effect of different operating parameters it was found
that the type of catalyst used has the most significant effect on the
transesterification reaction. Amidst the metal oxide catalysts
examined, CaO gave the best performance. This study indicates the
feasibility of producing glycerol carbonate using different grade of
glycerol in both conventional thermal activation and microwave
irradiation with CaO as catalyst. Microwave assisted
transesterification (MAT) of glycerol into glycerol carbonate has
demonstrated itself as an energy efficient route by achieving 94.2%
yield of GC at 65°C, 5 minutes reaction time, 1 wt% CaO and
DMC/glycerol molar ratio of 2. The advantages of MAT
transesterification route has made the direct utilization of bioglycerol
from biodiesel production without the need of purification. This has
marked a more economical and less-energy intensive glycerol
carbonate synthesis route.
Abstract: Synthesis of gold nanoparticles has attracted much
attention since the pioneering discovery of the high catalytic activity
of supported gold nanoparticles in the reaction of CO oxidation at
low temperature. In this research field, we used Na-montmorillonite
for gold nanoparticles stabilization; various gold loading percentage
1, 2 and 5% were used for gold nanoparticles preparation. The gold
nanoparticles were obtained using chemical reduction method using
NaBH4 as reductant agent. The obtained gold nanoparticles stabilized
in Na-montmorillonite were used as catalysts for the reduction of 4-
nitrophenol to aminophenol with sodium borohydride at room
temperature. The UV-Vis results confirmed directly the gold
nanoparticles formation. The XRD and N2 adsorption results showed
the formation of gold nanoparticles in the pores of montmorillonite
with an average size of 5 nm obtained on samples with 2% gold
loading percentage. The gold particles size increased with the
increase of gold loading percentage. The reduction reaction of 4-
nitrophenol into 4-aminophenol with NaBH4 catalyzed by Au-Namontmorillonite
catalyst exhibits remarkably a high activity; the
reaction was completed within 9 min for 1%Au-Na-montmorillonite
and within 3 min for 2%Au-Na-montmorillonite.
Abstract: The use of titanium fluoride and iron fluoride
(TiF3/FeF3) catalysts in combination with polutetrafluoroethylene
(PTFE) in plain zinc- dialkyldithiophosphate (ZDDP) oil is important
for the study of engine tribocomponents and is increasingly a strategy
to improve the formation of tribofilm and provide low friction and
excellent wear protection in reduced phosphorus plain ZDDP oil. The
influence of surface roughness and the concentration of
TiF3/FeF3/PTFE were investigated using bearing steel samples
dipped in lubricant solution at 100°C for two different heating time
durations. This paper addresses the effects of water drop contact
angle using different surface; finishes after treating them with
different lubricant combination. The calculated water drop contact
angles were analyzed using Design of Experiment software (DOE)
and it was determined that a 0.05 μm Ra surface roughness would
provide an excellent TiF3/FeF3/PTFE coating for antiwear resistance
as reflected in the Scanning electron microscopy (SEM) images and
the tribological testing under extreme pressure conditions. Both
friction and wear performance depend greatly on the PTFE/and
catalysts in plain ZDDP oil with 0.05 % phosphorous and on the
surface finish of bearing steel. The friction and wear reducing effects,
which was observed in the tribological tests, indicated a better micro
lubrication effect of the 0.05 μm Ra surface roughness treated at
100°C for 24 hours when compared to the 0.1 μm Ra surface
roughness with the same treatment.
Abstract: In recent research copper and manganese systems
were found to be the most active in CO and organic compounds
oxidation among the base catalysts. The mixed copper manganese
oxide has been widely studied in oxidation reactions because of their
higher activity at low temperatures in comparison with single oxide
catalysts. The results showed that the formation of spinel
CuxMn3−xO4 in the oxidized catalyst is responsible for the activity
even at room temperature. That is why the most of the investigations
are focused on the hopcalite catalyst (CuMn2O4) as the best coppermanganese
catalyst. Now it’s known that this is true only for CO
oxidation, but not for mixture of CO and VOCs. The purpose of this
study is to investigate the alumina supported copper-manganese
catalysts with different Cu/Mn molar ratio in terms of oxidation of
CO, methanol and dimethyl ether. The catalysts were prepared by impregnation of γ-Al2O3 with
copper and manganese nitrates and the catalytic activity
measurements were carried out in two stage continuous flow
equipment with an adiabatic reactor for simultaneous oxidation of all
compounds under the conditions closest possible to the industrial. Gas
mixtures on the input and output of the reactor were analyzed with a
gas chromatograph, equipped with FID and TCD detectors. The
texture characteristics were determined by low-temperature (- 196oС)
nitrogen adsorption in a Quantachrome Instruments NOVA 1200e
(USA) specific surface area & pore analyzer. Thermal, XRD and
TPR analyses were performed. It was established that the active component of the mixed Cu-
Mn/γ–alumina catalysts strongly depends on the Cu/Mn molar ratio.
Highly active alumina supported Cu-Mn catalysts for CO, methanol
and DME oxidation were synthesized. While the hopcalite is the best
catalyst for CO oxidation, the best compromise for simultaneous
oxidation of all components is the catalyst with Cu/Mn molar ratio
1:5.
Abstract: A comparison of activity and stability of the as-formed
Pt/C, Pt-Co and Pt-Pd/C electrocatalysts, prepared by a combined
approach of impregnation and seeding, was performed. According to
the activity test in a single Proton Exchange Membrane (PEM) fuel
cell, the Oxygen Reduction Reaction (ORR) activity of the Pt-M/C
electrocatalyst was slightly lower than that of Pt/C. The j0.9 V and
E10 mA/cm2 of the as-prepared electrocatalysts increased in the order of
Pt/C > Pt-Co/C > Pt-Pd/C. However, in the medium-to-high current
density region, Pt-Pd/C exhibited the best performance. With regard to
their stability in a 0.5 M H2SO4 electrolyte solution, the
electrochemical surface area decreased as the number of rounds of
repetitive potential cycling increased due to the dissolution of the
metals within the catalyst structure. For long-term measurement, Pt-
Pd/C was the most stable than the other three electrocatalysts.
Abstract: This work studies the effect of chemical composition
on the activity and selectivity of γ–alumina supported CuO/
MnO2/Cr2O3 catalysts toward deep oxidation of CO, dimethyl ether
(DME) and methanol. The catalysts were prepared by impregnation
of the support with an aqueous solution of copper nitrate, manganese
nitrate and CrO3 under different conditions. Thermal, XRD and TPR
analysis were performed. The catalytic measurements of single
compounds oxidation were carried out on continuous flow equipment
with a four-channel isothermal stainless steel reactor. Flow-line
equipment with an adiabatic reactor for simultaneous oxidation of all
compounds under the conditions that mimic closely the industrial
ones was used. The reactant and product gases were analyzed by
means of on-line gas chromatographs.
On the basis of XRD analysis it can be concluded that the active
component of the mixed Cu-Mn-Cr/γ–alumina catalysts consists of at
least six compounds – CuO, Cr2O3, MnO2, Cu1.5Mn1.5O4,
Cu1.5Cr1.5O4 and CuCr2O4, depending on the Cu/Mn/Cr molar ratio.
Chemical composition strongly influences catalytic properties, this
influence being quite variable with regards to the different processes.
The rate of CO oxidation rapidly decrease with increasing of
chromium content in the active component while for the DME was
observed the reverse trend. It was concluded that the best
compromise are the catalysts with Cu/(Mn + Cr) molar ratio 1:5 and
Mn/Cr molar ratio from 1:3 to 1:4.
Abstract: In this work new macroporous Ni electrodes modified
with Au nanoparticles for hydrogen production have been developed.
The supporting macroporous Ni electrodes have been obtained by
means of the electrodeposition at high current densities. Then, the Au
nanoparticles were synthesized and added to the electrode surface.
The electrocatalytic behaviour of the developed electrocatalysts was
studied by means of pseudo-steady-state polarization curves,
electrochemical impedance spectroscopy (EIS) and hydrogen
discharge curves. The size of the Au synthetized nanoparticles shows
a monomodal distribution, with a very sharp band between 10 and 50
nm. The characteristic parameters d10, d50 and d90 were 14, 20 and
31 nm respectively. From Tafel polarization data has been concluded
that the Au nanoparticles improve the catalytic activity of the
developed electrodes towards the HER respect to the macroporous Ni
electrodes. EIS permits to obtain the electrochemically active area by
means of the roughness factor value. All the developed electrodes
show roughness factor values in the same order of magnitude. From
the activation energy results it can be concluded that the Au
nanoparticles improve the intrinsic catalytic activity of the
macroporous Ni electrodes.
Abstract: HZSM-5 zeolites modified by iron and phosphorus
were applied in catalytic cracking of butene. N2 adsorption and
NH3-TPD were employed to measure the structure and acidity of
catalysts. The results indicate that increasing phosphorus loading
decreased surface area, pore volume and strong acidity of catalysts.
The addition of phosphorus significantly decreased butene conversion
and promoted propylene selectivity. The catalytic performance of
catalyst was strongly dependent on the reaction conditions.
Appropriate reaction conditions could suppress side reactions and
enhance propylene selectivity.
Abstract: Copper (I) oxide microparticles with the morphology
of cubic and hollow sphere were synthesized with the assistance of
surfactant as the shape controller. Both particles were then subjected
to study the catalytic activity and observed the results of shape effects
of catalysts on rate of catalytic reaction. The decolorizing reaction of
crystal violet and sodium hydroxide was chosen and measured the
decreasing of reactant with respect to times using spectrophotometer.
The result revealed that morphology of crystal had no effect on the
catalytic activity for crystal violet reaction but contributed to total
surface area predominantly.
Abstract: WO3/SiO2 catalysts were modified by an ion exchange
method with sodium hydroxide or potassium hydroxide solution. The
performance of the modified catalysts was tested in the metathesis of
ethylene and trans-2-butene to propylene. During ion exchange,
sodium and potassium ions played different roles. Sodium modified
catalysts revealed constant trans-2-butene conversion and propylene
selectivity when the concentrations of sodium in the solution were
varied. In contrast, potassium modified catalysts showed reduction of
the conversion and increase of the selectivity. From these results,
potassium hydroxide may affect the transformation of tungsten oxide
active species, resulting in the decrease in conversion whereas
sodium hydroxide did not. Moreover, the modification of catalysts by
this method improved the catalyst stability by lowering the amount of
coke deposited on the catalyst surface.
Abstract: The effect of additional magnesium oxide (MgO) was
investigated by using the tungsten oxide supported on silica catalyst
(WOx/SiO2) physically mixed with MgO in a weight ratio 1:1. The
both fresh and spent catalysts were characterized by FT-Raman
spectrometer, UV-Vis spectrometer, X-Ray diffraction (XRD) and
temperature programmed oxidation (TPO). The results indicated that
the additional MgO could enhance the conversion of trans-2-butene
due to isomerization reaction. However, adding MgO would increase
the amount of coke deposit on the WOx/SiO2 catalyst. The TPO
profile presented two peaks when the WOx/SiO2 catalyst was
physically mixed with MgO. The further peak was suggested that
came from coke precursor could be produced by isomerization
reaction of undesired product. Then, the occurred coke precursor
could deposit and form coke on the acid catalyst.
Abstract: Pt/γ-Al2O3 membrane catalysts were prepared via an
evaporative-crystallization deposition method. The obtained Pt/γ-
Al2O3 catalyst activity was tested after characterization (SEM-EDAX
observation, BET measurement, permeability assessment) in the
catalytic oxidation of selected volatile organic compound (VOC) i.e.
propane, fed in mixture of oxygen. The VOC conversion (nearly
90%) obtained by varying the operating temperature showed that
flow-through membrane reactor might do better in the abatement of
VOCs.
Abstract: The effect of N2 pretreatment on the catalytic activity
of tungsten-based catalysts was investigated in the metathesis of
ethylene and trans-2-butene at 450oC and atmospheric pressure. The
presence of tungsten active species was confirmed by UV-Vis and
Raman spectroscopy. Compared to the WO3-based catalysts treated
in air, higher amount of WO4 2-tetrahedral species and lower amount
of WO3 crystalline species were observed on the N2-treated ones.
These contribute to the higher conversion of 2-butene and propylene
selectivity during 10 h time-on-stream. Moreover, N2 treatment led to
lower amount of coke formation as revealed by TPO of the spent
catalysts.
Abstract: Propylene self-metathesis to ethylene and butene was
studied over WOx/SiO2 catalysts at 450oC and atmospheric pressure.
The WOx/SiO2 catalysts were prepared by incipient wetness
impregnation of ammonium metatungstate aqueous solution. It was
found that, adding nano-sized extra supports (SiO2 and TiO2) by
physical mixing with the WOx/SiO2 enhanced propylene conversion.
The UV-Vis and FT-Raman results revealed that WOx could migrate
from the original silica support to the extra support, leading to a
better dispersion of WOx. The ICP-OES results also indicate that
WOx existed on the extra support. Coke formation was investigated
on the catalysts after 10 h time-on-stream by TPO. However, adding
nano-sized extra supports led to higher coke formation which may be
related to acidity as characterized by NH3-TPD.
Abstract: The effect of transition metal doping on Pt/Al2O3
catalyst used in propane dehydrogenation reaction at 500°C was
studied. The preparation methods investigated were sequential
impregnation (Pt followed by the 2nd metal or the 2nd metal followed
by Pt) and co-impregnation. The metal contents of these catalysts
were fixed as the weight ratio of Pt per the 2nd metal of around 0.075.
These catalysts were characterized by N2-physisorption, TPR, COchemisorption
and NH3-TPD. It was found that the impregnated 2nd
metal had an effect upon reducibility of Pt due to its interaction with
transition metal-containing structure. This was in agreement with the
CO-chemisorption result that the presence of Pt metal, which is a
result from Pt species reduction, was decreased. The total acidity of
bimetallic catalysts is decreased but the strong acidity is slightly
increased. It was found that the stability of bimetallic catalysts
prepared by co-impregnation and sequential impregnation where the
2nd metal was impregnated before Pt were better than that of
monometallic catalyst (undoped Pt one) due to the forming of Pt sites
located on the transition metal-oxide modified surface. Among all
preparation methods, the sequential impregnation method- having Pt
impregnated before the 2nd metal gave the worst stability because this
catalyst lacked the modified Pt sites and some fraction of Pt sites was
covered by the 2nd metal.
Abstract: Beta-glucosidase, chitinase, leucine-aminopeptidase, acid phosphomonoesterase and acetate-esterase enzyme activities in
the soils under the impact of metallurgical industrial activity in Lori
marz (district) were investigated. The results of the study showed that
the activities of the investigated enzymes in the soils decreased with increasing distance from the Shamlugh copper mine, the Chochkan
tailings storage facility and the ore transportation road. Statistical
analysis revealed that the activities of the enzymes were positively
correlated (significant) to each other according to the observation
sites which indicated that enzyme activities were affected by the
same anthropogenic factor. The investigations showed that the soils
were polluted with heavy metals (Cu, Pb, As, Co, Ni, Zn) due to
copper mining activity in this territory. The results of Pearson
correlation analysis revealed a significant negative correlation
between heavy metal pollution degree (Nemerow integrated pollution
index) and soil enzyme activity. All of this indicated that copper
mining activity in this territory causing the heavy metal pollution of
the soils resulted in the inhabitation of the activities of the enzymes
which are considered as biological catalysts to decompose organic
materials and facilitate the cycling of nutrients.