13 research outputs found
New technologies in the production of motor fuels from renewable materials
This work presents resources of the Autonomous Province of Vojvodina
available for bioethanol and motor fuels (gasoline and diesel fuel) from
sustainable resources: corn-stalks, straw, sweet sorghum, pork fat. The
physicochemical basis for novel processes for motor fuel production is
coupling microwave pyrolysis of oil shale and catalytic cracking of purified
pyrolysis oil, hydrothermal liquefaction of algae and swine manure. The
effects of the degree of purification of crude pyrolysis oil and oil shale on
the degree of their conversion to gasoline and diesel fuel, as well as the
product distribution are investigated. The effects of the duration and
temperature of hydrothermal liquefaction of microalga, Botryoccocus braunii,
and swine manure on their degrees of conversion into bio-oil and its thermal
properties are investigated. The development of novel strategy of biofuel in
the Autonomous Province of Vojvodina is presented
The kinetics of ethanol adsorption from the aqueous phase onto zeolite NaZSM-5
The kinetics of the isothermal adsorption of ethanol from an aqueous solution onto a hydrophobic zeolite of the NaZSM-5 type in the temperature range 298-333 K was investigated. Specific shape parameters of the adsorption degree curves were determined. The changes in the specific shape parameters of the adsorption degree curves with temperature were determined. The kinetic parameters of ethanol adsorption (E-a, ln A) were determined by the initial rate, the saturation rate and the maximum rate methods as well as from the Johnson, Mehl and Avramy equation. The kinetic model of ethanol adsorption kt=[1-(1-alpha)(1/3)] was determined by the "model fitting" method. Ethanol adsorption from aqueous solution onto NaZSM-5 is a kinetically controlled process limited by the rate of three-dimensional movement of the boundary layer of the adsorption phase. A model for the mechanism of ethanol adsorption onto NaZSM-5 is suggested on the basis of the kinetic model. Ethanol molecules in aqueous solution are associated in clusters. The activation energy of the adsorption process corresponds to the energy required for the detachment of an ethanol molecule from a cluster and its adsorption onto the zeolite
Isothermal kinetics of exchange of water absorbed in calcium alginate hydrogel with ethanol
The isothermal kinetics of the exchange of absorbed water in calcium alginate hydrogels with ethanol was investigated. The isothermal kinetic curves were measured within the temperature range from 297 to 316 K. By the application of differential isoconversional methods, it was found that the process of exchange of water absorbed in calcium alginate hydrogel with ethanol has a unique rate determining step (a single step process). Using the model fitting method, it was determined that the kinetics of the exchange can be mathematically described with the kinetic model of the first-order chemical reaction. The values of the kinetic parameters of water exchange: the rate constants (km), energy of activation (Ea = 18.0 kJāmolā1), and the pre-exponential factor (ln[A/minā1] = 4.0) were calculated. By using Eyring's equation, the values of thermodynamics parameters: standard enthalpy of activation (ĪH*), standard entropy of activation (ĪS*), and Gibbs energy of activation (ĪG*) were calculated. It was found that the rate of rearrangements of the bound water around hydrophilic groups of a polymeric network has a dominant effect on the kinetics of the exchange of the absorbed water with ethanol. The mechanism of the exchange of adsorbed water with ethanol was suggested. [Project of the Serbian Ministry of Education,
Science and Technological Development, Grant no. 172015
Effect of UV/ozone treatment on the nanoscale surface properties of gold implanted polyethylene
The effect of ultraviolet (UV) ozone treatment on the surface properties of gold implanted high density polyethylene (HDPE) was investigated at a nanoscale using Atomic Force Microscopy (AFM). HDPE samples were modified by the implantation of gold ions at a dose of 5 x 10(15) ions/cm(2), using energies of 50, 100, 150, and 200 keV, and subsequently treated with UV/ozone. AFM surface topography images revealed that after UV/ozone treatment, the surface roughness of all Au/HDPE samples increased, while Power Spectral Density function increased only for samples implanted using higher energies, with a maximum for 150 keV. The chemical surface composition was homogenous in all cases, which was evidenced by appearance of single peaks in the histograms obtained from the phase AFM images. For UV/ozone treated samples, the shift of the peaks positions in the histograms to the higher values of the phase lag with respect to untreated ones indicated the decrease of surface hardness. Besides, a significant change of fractal dimension of surface grains is observed after UV/ozone treatment
Razlaganje N2O na katalizatoru Cu-ZSM-5 - analiza modela reakcije
The model of mechanism of the nitrous oxide (N2O) decomposition over the catalyst Cu-ZSM-5 proposed in 1999 in the article of Ochs and Turek, is adapted for mentioned process in open reactor and analyzed by the stoichiometric network analysis. Under these conditions five reaction pathways that all contribute to same overall process with defined but different contributions are found. Analyzing stoichiometric reactions of all obtained reaction pathways, in only one of them the nitric oxide (NO) as a product of reaction is found. Controlling the contribution of this reaction pathway to overall process, the control of production of NO as pollutant is makes possible.Model mehanizma reakcije razlaganja azotsuboksida (N2O) na zeolitnom katalizatoru CuZSM-5 predložen 1999. godine u radu Ochsa i Tureka, podeÅ”en je za pomenuti proces u otvorenom reaktoru i analiziran stehiometrijskom mrežnom analizom. Pokazano je da pod tim uslovima model predviÄa pet reakcionih puteva. Svi oni doprinose ukupnom procesu sa definisanim, ali razliÄitim udelima. Analizom stehiometrijskih jednaÄina reakcionih puteva naÄeno je da se samo u jednom od njih pojavljuje azotmonoksid (NO) kao proizvod. Kontrolom doprinosa ovog reakcionog puta celokupnom procesu otvara se moguÄnost kontrole proizvodnje zagaÄivaÄa azotmonoksida (NO)
Razlaganje N2O na katalizatoru Cu-ZSM-5 - analiza modela reakcije
The model of mechanism of the nitrous oxide (N2O) decomposition over the catalyst Cu-ZSM-5 proposed in 1999 in the article of Ochs and Turek, is adapted for mentioned process in open reactor and analyzed by the stoichiometric network analysis. Under these conditions five reaction pathways that all contribute to same overall process with defined but different contributions are found. Analyzing stoichiometric reactions of all obtained reaction pathways, in only one of them the nitric oxide (NO) as a product of reaction is found. Controlling the contribution of this reaction pathway to overall process, the control of production of NO as pollutant is makes possible.Model mehanizma reakcije razlaganja azotsuboksida (N2O) na zeolitnom katalizatoru CuZSM-5 predložen 1999. godine u radu Ochsa i Tureka, podeÅ”en je za pomenuti proces u otvorenom reaktoru i analiziran stehiometrijskom mrežnom analizom. Pokazano je da pod tim uslovima model predviÄa pet reakcionih puteva. Svi oni doprinose ukupnom procesu sa definisanim, ali razliÄitim udelima. Analizom stehiometrijskih jednaÄina reakcionih puteva naÄeno je da se samo u jednom od njih pojavljuje azotmonoksid (NO) kao proizvod. Kontrolom doprinosa ovog reakcionog puta celokupnom procesu otvara se moguÄnost kontrole proizvodnje zagaÄivaÄa azotmonoksida (NO)
The Effects of Different Physical Fields on Swelling Kinetics of PMAA-LTA Zeolite Composite Hydrogel Under Controlled Isothermal Conditions
Composite hydrogels are the subject of intensive research due to there specific 3D cross-linked
structure with extraordinary physical and chemical properties which enables variety of applications In
spite of increasing interest for using different external fields in physical-chemical processes, three are
no available literature data about the effects of external fields on swelling and swelling kinetics of
hydrogels. Therefore, the effects of (conventional) thermal (TH), ultrasonic (US) and microwave (MW)
fields, on the swelling degree and swelling kinetics. A sample of poly(methacrylic acid) (PMAA) xerogel
with 10%wt of LTA-zeolite (PMMA-LTA) was synthesized and thoroughly characterized. The
isothermal kinetic swelling curves were determined within a temperature range T= 293-323K in the
TH, US and MW fields. The results were well fitted with the Peppasā kinetic model. At all applied
fields, with an increase in temperature, there is an increase in the equilibrium swelling degree (SDeq)
and the swelling rate constant (k), while the parameter of Pepass's model (n) decreases. The maximum
value of SDeq and parameter n is achieved at TH, while the US assisted process leads to the maximum
value of k. The minimum value of the activation energy (Ea) and at the same time the maximum value
of the pre-exponential factor (lnA) lnA were achieved by applying the MW field. The influence of US
and MW fields on the diffusion of water molecules through the polymer network, activation of the
polymer network for swelling and relaxation of the polymer network was analysed
Insight and Comparison of Property Improvement in LTA and MFI Zeolite Reinforced Poly(methacrylic acid) Highly Concentrated Composite Hydrogels
The preparation of zeolite rich polymeric materials presents a challenge due to the zeolite settlingduring synthesis, poor miscibility, the phase separation and generally insufficient interactionsbetween polymers and zeolites. Combination of LTA, i.e. MFI, zeolite and poly(methacrylic acid) in theform of soft hydrogel network provided the stabilization of the zeolite particles and enabled synthesisof composite hydrogels with very high zeolite concentrations (26-52 mass%).The investigated morphological, mechanical and primary structural properties, water swelling abilityand thermal stability revealed high dependence on zeolite concentration and type. Zeolite particleswere uniformly dispersed in PMAA matrix as confirmed by SEM and there was no agglomeration orzeolite leaching despite very high concentrations. FTIR spectra disclosed the existence of functionalgroups of PMAA network and both zeolite types that interacted mutually and led to increasedcrosslinking density. The established interactions changed the PMAA chain dynamics around theparticles, especially of the LTA type, as showed by XRD. Having much more surface groups capable togenerate interaction with PMAA, LTA zeolite stronger affected all of the investigated properties.Compositesā mechanics was improved both in dry and swollen state compared to the PMAA hydrogel(up to 21.8 times for the sample with the highest LTA concentration). Thermal stability of thecomposites increased with increasing zeolite concentration.The composition-property correlations were determined making this work the base for furtherdevelopment of tailor-made zeolite-PMAA composite hydrogels aimed for specific application.Composites were tested as low-cost, regenerative, environmentally friendly sorbents and showedbetter removal of cationic dye compared to both components (PMAA and zeolite) alone
Insight and Comparison of Property Improvement in LTA and MFI Zeolite Reinforced Poly(methacrylic acid) Highly Concentrated Composite Hydrogels
The preparation of zeolite rich polymeric materials presents a challenge due to the zeolite settling
during synthesis, poor miscibility, the phase separation and generally insufficient interactions
between polymers and zeolites. Combination of LTA, i.e. MFI, zeolite and poly(methacrylic acid) in the
form of soft hydrogel network provided the stabilization of the zeolite particles and enabled synthesis
of composite hydrogels with very high zeolite concentrations (26-52 mass%).
The investigated morphological, mechanical and primary structural properties, water swelling ability
and thermal stability revealed high dependence on zeolite concentration and type. Zeolite particles
were uniformly dispersed in PMAA matrix as confirmed by SEM and there was no agglomeration or
zeolite leaching despite very high concentrations. FTIR spectra disclosed the existence of functional
groups of PMAA network and both zeolite types that interacted mutually and led to increased
crosslinking density. The established interactions changed the PMAA chain dynamics around the
particles, especially of the LTA type, as showed by XRD. Having much more surface groups capable to
generate interaction with PMAA, LTA zeolite stronger affected all of the investigated properties.
Compositesā mechanics was improved both in dry and swollen state compared to the PMAA hydrogel
(up to 21.8 times for the sample with the highest LTA concentration). Thermal stability of the
composites increased with increasing zeolite concentration.
The composition-property correlations were determined making this work the base for further
development of tailor-made zeolite-PMAA composite hydrogels aimed for specific application.
Composites were tested as low-cost, regenerative, environmentally friendly sorbents and showed
better removal of cationic dye compared to both components (PMAA and zeolite) alone
Structureāproperty correlations for composite hydrogels based on poly(methacrylic acid) and high concentrations of LTA zeolite
High concentrations of LTA zeolite (27-52mass%) were embedded in poly(methacrylic acid) (PMAA) matrix to obtain composite hydrogels with porosity and active sites originating from both components. Substandard mechanics of PMAA and aggregation of zeolite particles, were thereby overcome. The composites had remarkably higher density than PMAA xerogel (1700 to1400 kg mā3), higher crosslinking density (54.8 to1.29 mol mā3) and lower swelling degree (41 to 420 kg kgā1). Zeolite particles were uniformly dispersed in PMAA matrix and there was no agglomeration or leaching of zeolite despite very high concentrations. XRD patterns revealed that the inclusion of zeolite particles affected the short-range order in the PMAA matrix. Being an active filler LTA zeolite notably improved thermal stability and mechanics of PMAA hydrogel, multiplying the storage modulus 5.2 times in dry and 21.8 times in swollen state. Structureāproperty correlations were provided making the base for further development of tailor-made zeolite-PMAA composite hydrogels