The complexes of [Sm(o-MOBA)3bipy]2·H2O and [Sm(m-MOBA)3bipy]2·H2O (o(m)-MOBA = o(m)-methoxybenzoic acid, bipy-2,2′-bipyridine) have been synthesized and characterized by elemental analysis, IR, UV, XRD and
molar conductance, respectively. The thermal decomposition processes of the two complexes were studied by means of TG–DTG
and IR techniques. The thermal decomposition kinetics of them were investigated from analysis of the TG and DTG curves by
jointly using advanced double equal-double steps method and Starink method. The kinetic parameters (activation energy E and pre-exponential factor A) and thermodynamic parameters (ΔH≠, ΔG≠ and ΔS≠) of the second-step decomposition process for the two complexes were obtained, respectively.
In this study, four oil-shale samples (Niğde-Ulukışla) excavated from Central Anatolia Turkey were analyzed where this region
is believed to have a high potential of oil in its shale rich outcrops. The samples (∼40 g) were combusted at 50 psi gas injection
pressure, at an air injection rate of 1.5 L min−1 in a combustion-reaction cell. All the experiments were conducted up to 600°C. The percentages of oxygen consumption and
carbon monoxide and carbon dioxide production were obtained instantaneously with respect to time. The combustion periods and
relative reaction rates were determined by examining the effluent gas concentration peaks. Activation energies of the samples
were determined using Weijdema’s approach. It was observed that the activation energies of the samples are varied between
22–103 kJ mol−1.
Authors:C. Ampelli, D. Di Bella, D. Lister, G. Maschio, and J. Parisi
A small ultraviolet-visible absorption spectrometer which uses fibre optic coupled immersion probes has been incorporated
into a laboratory scale reaction calorimeter. The combined instrument has been tried out using the hydrolysis of acetic anhydride
as a test reaction. With the calorimeter operating in the isoperibolic mode good agreement is found for the pseudo-first order
reaction rate constant as determined from spectroscopic and calorimetric measurements. Experiments have been made in order
to follow the reaction indirectly using optical pH measurements with acid-base indicators. The possibility of determining
the temperature dependence of the rate constant in a single experiment has also been investigated.
The solvent-free reduction of benzophenone and five substituted benzophenones with sodium borohydride to the corresponding alcohols was studied by thermal analysis, X-ray powder diffractometry, NMR spectroscopy, and scanning electron microscopy. In most cases, the reaction occurs via liquid eutectic phases that are formed between the benzophenone and the resulting benzohydrol. Nevertheless, this reaction can be carried out without the need for a solvent, leading to pure alcohol without side products. In some cases, heating may be necessary to achieve a reasonably short reaction time. In conclusion, this reaction type appears to be feasible as a preparative organic reaction that avoids a solvent.
The activation energies of the same process are often reported to have different values, which are usually explained by the
differences in experimental conditions and sample characteristics. In addition to this type of uncertainty, which is associated
with the process (ΔEprocess) there is an uncertainty related to the method of computation of the activation energy (ΔEmethod). For a method that uses fitting single heating rate data to various reaction models, the value of ΔEmethod) method is large enough to explain significant differences in the reported values of the activation energy. This uncertainty
is significantly reduced by using multiple heating rate isoconversional methods, which may be recommended for obtaining reference
values for the activation energy.
The reaction calorimeter CAP202 (chemical process analyzer) determines thermal effects by measuring the true heat flow (THF)
based on unique design principles. In particular, measurements can be performed without requiring any calibration procedures
and the obtained results are most reliable and exhibit extremely stable baselines. The benefits in respect of experimental
speed, data quality and long term performance are obvious. Due its broad dynamic range the instrument can be employed for
measurements ranging from small physical heat to energetic chemical reactions. The CPA allows running experiments seamlessly
with reaction volumes between 10 and 180 mL. This volume flexibility simplifies the investigation of multi-step operations
and is the basis for various applications employing precious or highly energetic compounds. Due to the fact that calibrations
are not required, altering conditions during a single experiment like changes in viscosities, liquid levels or stirring speeds
do not affect the results of the measurements.
This research was aimed
to investigate the role of clay on the combustion and kinetic behavior of
crude oils in limestone matrix. For this purpose, simultaneous TG (thermogravimetry)
and DTA (differential thermal analysis) experiments were performed at three
different heating rates as 10–15 and 20C min–1,
respectively. A uniform trend of decreasing activation energies was observed
with the addition of clay. It was concluded that clays surface area affects
the values of Arrhenius constant, while it is the catalytic properties of
clay, which lower the activation energies of all the reactions, involved in
the combustion process.
Classical thermo-analytical micro methods (DTA, DSC) are still very useful for process work, but medium scale instruments based on heat flow measurement are attaining an increasingly important role in this domain.
As in many areas, development of reaction calorimetry for industrial applications was driven by needs and by available means (technical capabilities).
The needs have been fairly constant over the past decades. There are data needs:
-Heat release rates
-Heat of desired reactions and decompositions
-Heat capacities and heat transfer capacities
It took the specialists of calorimetry a long time to recognize and to accept the operational needs, namely:
-Working under controlled temperature conditions (constant temperature, temperature ramps)
-Adding components during runs (continuously or in portions)
-Simulation of industrial mixing conditions
The main driving force for the development of process oriented calorimetric instruments was the evolution of electronic hardware which made the control of heat flow on a (non micro) laboratory scale easy.
The paper gives an overview on the principles of heat flow control and reviews the developments of the fifties and sixties, when the matching of heat flow with heat release by reactions was the goal.
With the advent of fast and powerful laptop computers, the focus has shifted. Now, the deduction of true heat release rates from signals which may be badly distorted, is the goal.
Some recent developments are reviewed and the hope is expressed that calorimetric equipment, inexpensive enough to be affordable for every laboratory engaged in process work, will be available soon.