The development of heat flow calorimetry as a tool for process optimization and process safety

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:

Reaction rates

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.     

Thermoanalytical control of paint-shop wastes prior to disposal

The paint-shop wastes under study originated from metallurgical factory painting houses. Displaying a high toxicity and flammability, they are classified as specifically hazardous to the natural environment. Paint-shop wastes can be disposed of in the following ways:

solidification and deposition in sanitary landfills;

storage on a special dumping ground;

incineration.

This paper presents the physicochemical composition and thermal analysis (DTA and TG) of paint-shop wastes and their mixtures with various components. Thermoanalytical measurements were carried out in a dynamic atmosphere of air. Enthalpies were calculated from the peak areas of the DTA curves. Thermoanalytical data were compared with calorimetric results obtained with an oxygen bomb.     

The mechanism of plasma-induced deposition of amorphous silicon from silane

Time-resolved mass spectrometric data show that the concentration of di- and trisilane, which are formed from monosilane under discharge conditions typical for the deposition of high electronic quality amorphous silicon, correlate with the measured deposition rate of a-Si. The data can be quantitatively and self-consistently described by a simple set of consecutive reactions:

1. SiH₄ →-SiH₂ + H₂
2. SiH₂ + SiH₄ → Si₂H₆
3. SiH₂ + Si₂H₆ → Si₃H₈
4. Si _n H_{2(n + 1)} →n ·a-Si:H+(n+1)H₂,n=2,3

The only fitting parameter necessary for an excellent fit of the measured data over a wide range of experimental parameters is the value of the reactive sticking coefficient .for the decomposition of di- and trisilane (reaction 3). The resultant value agrees well with the published data of other authors and with those calculated from the measured deposition rate and Si₂H₆, concentration. We did not find and physically meaningful way to lit the measured data with the various “SiH₃ models” proposed by other authors who assumed that the dominant species responsiblefor the deposition of a-Si: H is the SiH₃, radical. For this and some additional reasons mentioned in the present paper. the SiH₃ model is in disagreement with available experimental data.     

Theoretical study of the visible photodissociation spectrum of Ar 3 +

The photodissociation of Ar ₃ ⁺ is studied following a consistent theoretical approach from the Potential Energy Surfaces to the dynamics. Six P.E.S. are computed according to a D.I.M.-like model Hamiltonian. Transition dipole moments are determined using a similar method. The 4-D dynamics of this system is obtained with the H.W.D. method (Hemiquantal dynamic with the Whole DIM basis). All the 4 nuclear degrees of freedom and all the 6 electronic states are involved in the dynamical calculations, allowing for very general investigations. The main theoretical results are:

1. the spectrum essentially results from a Σ → Σg transition to the second excited electronic state along with a symmetric stretching motion
2. excited Ar ₃ ⁺ molecules almost all dissociate in Ar⁺ + 2 Ar
3. dissociation in Ar ₂ ⁺ + Ar requires special conditions such as low laser excitation and is predicted to increase with a specific excitation of the bending mode
4. the dominant symmetric stretching motion induces a bimodal kinetic energy distribution of the fragments.

All these points are in close agreement with experimental results.     

Mikrobestimmung von monosubstituierten Acetylenverbindungen durch Bestimmung des aktiven Wasserstoffs mit Alanat

1. The determination of monosubstituted acetylenic compounds was investigated at various temperatures (?60° to +95°C) by the alanate method described byMerz.
2. At 90°C all active hydrogen atoms were determined with sufficient accuracy and good precision, but at 0° C the active hydrogen atom of the ethinyl group in monosubstituted acetylenes did not react. This is the basis of a method for determining the acid hydrogen in the ethinyl group: the active hydrogen reactive at 0° C is first determined, then the temperature is raised to 90° C, when all the remaining active hydrogen atoms are determined.
3. The Merz method for determining active hydrogen is in our opinion the most suitable chemical method for determining ethinylcarbinols.
4. It has been shown that active hydrogen atoms react faster with alanate (sodium diethyldihydridoaluminate) than with Grignard reagent. The active hydrogen atoms in certain compounds do not react quantitatively with Grignard reagent within the normal tune. The alanate method is thus more generally applicable than the Grignard method.

     

Drug targeting by drug entrapment into ultrafine compartments as carriers

The incorporation of drugs into vesicles is one of several technological methods for the optimization of targeted drug delivery and controlled drug targeting. The main problems will always remain

? To design inert auxiliary accompanying materials in order to overcome side reactions

? To use body-friendly and biodegradable macromolecular carrier materials for the therapeutic system

? To miniaturize the dosage form dramatically in the submicroscopic size range in order to eliminate foreign body irritations

? To develop ultrafine solid and amorphous vesicular compartments (nanocapsules, nanopellets, nanoparticles) to get stable systems with good tissue transfer and organ targeting properties

The actual stand of the incorporation of drugs and biologic active material into ultrafine colloidal solid capsules is reviewed here as for instance:

? Immunoactive material

? Fluorescent indicators in body fluids

? Controlled and sustained release systems

? Nonspecific drug targeting of the first-order (passage through endothelial tissues)

? Second-order targeting (a specific transparenchymal migration), and a highly specific targeting of the third-order (transcellular passage, especially lysosomal transports)

Examples for some of these applications are given. It can be shown that such ultrafine vesiculated capsules offer some advantages when applied parenterally, but also partly for oral application. In the future, still more studies are necessary finally to clarify the importance and practical use of such ultrafine targeting carriers.     

Kompressionsverhalten und Gleichgewichtsspreitungsdrücke binÄrer monomolekularer Dimyristoylkephalin/Dilauroylkephalin-Mischungen

1. The concentration dependence of theF/A-isotherms (premixed spreading, separate spreading) and the equilibrium spreading pressuresF ^e of the system dimyristoyl-cephaline/dilauroyl-cephaline were studied atT=295 K. The results were analysed and compared with respect to the miscibility using thermodynamical criteria.
2. It was shown that various spreading techniques lead to different experimental results. In the case of the premixed spreading it is formed initially an equilibrium monolayer. The analysis of the concentration dependence of the phase transition point (liquid expanded → condensed) shows that the components are completely miscible.
3. From theF/A-isotherms of premixed spreading the A(area)-x ^τ (surface concentrations-diagrams were calculated. The deviation from the ideal behaviour of the A-x ^τ-curves is caused by a phase separation.
4. From the concentration dependence of the equilibrium spreading pressures by means of the surface phase rule follows that the components are approximately ideally miscible.
5. By the analysis of the collapse and equilibrium spreading pressures follows that the mixed films during the compression are in a metastabile state.

     

Thermal analysis and microstructure of solids and solid state reactions

Thermoanalytical and microstructural measurement techniques allow the characterization of solids, their transformation, decomposition, specific surface and pore structure. These techniques are of importance for solids with high specific surface and/or porosity. Thermoanalytical techniques are applied to detect solid state reactions, to determine reaction temperatures and to monitor the progress of the reaction. They are useful to simulate thermal processes in the industry and to receive meaningful results with small samples in a short time. Specific surface, cumulative pore volume and pore volume distribution are obtained by intrusion and absorption techniques. Here selected applications of thermoanalytical and microstructure investigations in modern fields of materials research will be presented, as:

-pore analysis of sintering steps of ceramics,

-secondary structure of catalyst granules,

-template decomposition in zeolites,

-firing process in a composide ceramic tape,

-ignition of coke.

     

Limits of cyclodextrin application in oral drug preparations

Cyclodextrins are applied to facilitate formulation problems, to improve stability and bioavailability. Following factors are determining whether or not cyclodextrins can be applied in oral pharmaceutical preparations:

- properties of the selected CD: solubility, price, specific catalytic properties,

- the drug to be complexed: molecular weight, polarity, solubility,

- drug dose

- solubility properties of the complex and the “super solubility” /temporary over-saturation/

- complex stability and possibility to shift the dissociation equilibrium toward the appropriate direction

- legislative procedures

     

Applications of pattern recognition

This poster illustrates the lecture on Pattern Recognition and gives recently published and unpublished examples, mainly from the laboratory from the first author. The applications concern:

- the determination of metabolic pathways of branched chain fatty acids (by clustering),

- the development of a genetic classification of meteorites (by clustering),

- the classification of cholinergic agents according to their interaction with different receptors (by clustering),

- the structure of a data set consisting of gaschromatographic profiles in samples collected in pollution monitoring stations (by factor analysis and pattern recognition),

- factors determining GLC behaviour of solutes (by factor analysis and multiple regression),

- the classification of olive oils according to geographic origin (by principal components and pattern recognition),

- the diagnosis of thyroid status (by pattern recognition).

     

Charakterisierung der Mischbarkeitseigenschaften binärer Monoschichten durch Messung der Gleichgewichtsspreitungsdrucke

1. The equilibrium spreading pressures were studied as a function of composition of the following binary systems by use of the Wilhelmy-method atT=295 K on aqueous substrate:

octadecyldiethylphosphine oxide/1-hexadecanol (I)

octadecyldiethylphosphine oxide/1-eicosanol (II)

octadecyldiethylphosphine oxide/stearic acid (III)

1. The equilibrium spreading pressures of the pure components of the systems I und II, respectively, decrease due to addition of the corresponding components of mixture. A minimum occurs at the mole fractionx=0,50. The equilibrium spreading pressures of mixtures of system III rise with increasing mole fraction of octadecyldiethylphosphine oxide.
2. The three spreading diagrams are based on one general type. The phase rule is applied and shows that the components of the 3 systems must be immiscible in the monolayer but miscible in the bulk phase.

     

An experimental study of the surface rheology of adsorbed protein layers

Adsorbed gelatin layers have been characterized by measuring the surface equilibrium tension and surface rheological parameters of shear, found by surface creep experiments. After the determination of these parameters the solution below the adsorption layer (gelatin + phosphate buffer) was substituted by a gelatin-free phosphate-buffer-solution. The differences of the parameters calculated before and after the substitution of the bulk phase allowed us to prove some model assumptions of the protein adsorption and to characterize the physical contents of some of the surface rheological parameters determined. The parameters calculated and measured permit the distinction of three different concentration ranges of gelatin:

1. the range of reversible adsorption layer.
2. the ranges of saturated, irreversible adsorption layer, and
3. the range of multilayer formation.

     

Theoretical discussion of methods of elimination of matrix effects in non-dispersive X-ray analysis

Theoretical consideration concerning some possibilities for the elimination of matrix effects in non-dispersive X-ray fluorescence and absorption analysis are discussed. The theoretical treatment is concerned with the following methods:

1. double-channel absorption edge analysis,
2. concentration increase and dilution method in fluorescence analysis,
3. fluorescence-absorption method,
4. emission-transmission method,
5. fluorescence-Compton scattering method,
6. method of multicomponent analysis.

On the basis of the derived formulas, nomographic methods of interpretation of the data are given. Using these methods it is possible to determine unambiguously the concentration of the relevant element. The formulas are also convenient for numerical interpretation. The introduction of the concept of “generalized sensitivity” allows the comparison of various radiometric methods.     

Parameter distortion by unappropriate nonisothermal treatment

The aim of this contribution is to draw attention to the following problems:

1. boundary conditions of kinetic models,
2. distortion of kinetic data by cutting-off the peak ends,
3. regression analysis involved in the evaluation of kinetic data.

     

A family of explicit linear six-step methods with vanished phase-lag and its first derivative

A family of explicit linear sixth algebraic order six-step methods with vanished phase-lag and its first derivative is obtained in this paper. The investigation of the above family of methods contains:

theoretical study of the new family of methods and

computational study of the new family of methods.

The theoretical study of the above mentioned family of methods contains:

1. the development of the method,
2. the computation of the local truncation error,
3. the comparative local truncation error analysis. The comparison is taken place between the new family of methods with the corresponding method with constant coefficients and
4. the stability analysis of the new family of methods. The stability analysis is taken place using test equation with different frequency than the frequency of the test equation used for the phase-lag analysis of the methods.

The application of the new family of linear six-step sixth algebraic order methods to the resonance problem of the one-dimensional time independent Schrödinger equation is used for the computational study of the new family of methods. The result of the above mentioned theoretical and computational investigation is that the new proposed family of linear explicit schemes are computationally and theoretically more effective than other well known methods for the approximate solution of the radial Schrödinger equation and related initial or boundary value problems with periodic and/or oscillating solutions.     

Ein Vektor-Schema für Trennvorgänge

Separation processes, based on different migration speeds of components in mixtures can be reduced to combinations of 3 elements:

1. Migrations, defined by different speeds of components,
2. Shifts, which move all components at the same speed,
3. Gradients, which influence the speed of components in migrations or shifts.

These elements are vectors. They can be used for the better understanding and improvement of existing processes or for planning of new separating methods. Examples for possible new processes are described.     

Einsatz der echten Integration in der Atomabsorptions-Spektroskopie

An improvement of the signal-to-noise ratio in atomic absorption spectroscopy may be obtained by each of the following three methods of signal averaging:

increase of the time constant

digital signal averaging

true integration of the signal

The most adequate of these methods appears to be true integration. Two examples are presented to demonstrate the improved signal-to-noise ratio due to the application of this method:

trace analysis of mercury in water by means of flameless AAS. The detection limit appears to be 0.2 ng which corresponds to a concentration of 2 · 10^?13 g/ml.

trace analysis of copper in human urine by means of flame AAS: 1,3 · 10^?8 g/ml copper could be detected without any solvent extraction process.

     

Investigation of the CeFe binary system

The CeFe binary system was investigated and an FeCe binary phase diagram was proposed. This system consists of

• 1.(i) two peritectic reactions, γ-Fe + L → Ce₂Fe₁₇ and Ce₂Fe₁₇ + L → CeFe₂, occurring isothermally at 1063°C and 925°C respectively;
• 2.(ii) a eutectic reaction, L → CeFe₂ + Ce, occurring isothermally at 592°C with eutectic containing 83.3 at.% Ce (92.6 wt.% Ce);
• 3.(iii) a peritectoid reaction, γ-Fe + Ce₂Fe₁₇ → α-Fe(Ce), occurring isothermally at 922 °C.

The solid solubility of cerium in iron in the temperature range 850–900 °C was found to be less than 0.04 at.% (0.1 wt.%). The Curie temperature of α-Fe(Ce) was slightly lowered with increasing cerium content in solid solution.     

Erratum to: “Current uses and trends in catalytic isomerization, alkylation and etherification processes to improve gasoline quality”

The original version of the article was published in Cent. Eur. J. Chem. 12(1) (2014) pp. 1–13. Unfortunately, the original version of this article contains some mistakes in the text:

• The caption of Figure 7. A fixed bed unit converted to the UOP Par-Isom Process?
• Par Isom Process should be written as Par-Isom Process?
• everywhere in the text LCC should be written as LLC

     

Thermogravimetric study of the kinetics of structural relaxation of amorphous silica

To determine the role of the forms of fixed water in the relaxation of the silica structure, silica as treated with hot water vapour in an autoclave, and the kinetics of its dehydration were studied by thermogravimetry. Five successive stages of relaxation were established:

1. Flocculation of globules, accompanied by evaporation of the polymolecular water layer situated in the interglobular space.
2. Formation of a glassy structure, accompanied by further water evaporation.
3. Transition of the glassy structure to cristobalite with the formation of large particles.
4. Formation of quartz seeds within each particle.
5. Aggregation of oriented seeds into monocrystals of quartz.

The crystallization of amorphous silica in all stages depends on the interaction of different water forms with fragments of the silicon-oxygen skeleton. The activation energy of water evaporation was calculated; it varies from 21 to 38 kJ/mol for the different stages of the process. The activation energy of silica relaxation was evaluated to be about 125 kJ/mol.