Differential kinetic analysis

The l -value is very similar to that found from graphical calculations k = 0.021 min . Differential kinetic analysis would be much more accurate if experiments were performed in a CSTR. The rates would then be measured directly with greater accuracy and no differentiation error would be made. Moreover, the concentration of the reactant and products could then be varied independently. 

Several methods have been developed over the years for the thermochemical characterisation of compounds and reactions, and the assessment of thermal safety, e.g. differential scanning calorimetry (DSC) and differential thermal analysis (DTA), as well as reaction calorimetry. Of these, reaction calorimetry is the most directly applicable to reaction characterisation and, as the heat-flow rate during a chemical reaction is proportional to the rate of conversion, it represents a differential kinetic analysis technique. Consequently, calorimetry is uniquely able to provide kinetics as well as thermodynamics information to be exploited in mechanism studies as well as process development and optimisation [21]. 

The kinetic and thermodynamic characterisation of chemical reactions is a crucial task in the context of thermal process safety as well as process development, and involves considering objectives as diverse as profit and environmental impact. As most chemical and physical processes are accompanied by heat effects, calorimetry represents a unique technique to gather information about both aspects, thermodynamics and kinetics. As the heat-flow rate during a chemical reaction is proportional to the rate of conversion (expressed in mol s 1), calorimetry represents a differential kinetic analysis method [ 1 ]. For a simple reaction, this can be expressed in terms of the mathematical relationship in Equation 8.1 ... 

P.R. Fortes, S.R.P. Meneses, E.A.G. Zagatto, A novel flow-based strategy for implementing differential kinetic analysis, Anal. Chim. Acta 572 (2006) 316. 

In the absence of chemical reactions (with a coloured analyte), the recorded peak reflects the temporal variation of the analyte concentration due solely to the dispersion process. Conversely, the peak shape may provide useful information on reaction kinetics in situations involving chemical reactions. Successive measurements performed on a flowing sample can therefore be exploited, as illustrated by the spec-trophotometric determination of vanadium and iron in steel alloys [120], which relies on a novel strategy for implementing differential kinetic analysis. 

Ga, A1 Synthetic solutions UV-Vis 1-5, 20-100 mg L-1 60 Zone stopping at the detector/differential kinetic analysis/multivariate calibration [143]... 

This strategy is especially attractive in relation to analytical procedures relying on relatively slow chemical reactions (catalytic procedures and differential kinetic analysis) and/or exploiting different degrees of sample dispersion. The influence of zone recycling on sample dispersion and the potential, limitations and application range of the strategy are presented elsewhere [78,79]. 

D. Vendramini, V. Grassi, E.A.G. Zagatto, Spectrophotometric flow injection determination of copper and nickel in plant digests exploiting differential kinetic analysis and multi site detection, Anal. Chim. Acta 570 (2006) 124. 

H. Kagenow, A. Jensen, Differential kinetic analysis and flow injection analysis, Part 3. The (2.2.2) cryptates of magnesium, calcium and strontium, Anal. Chim. Acta 114 (1980) 227. 

D. Espersen and A. Jensen, Differential Kinetic Analysis and Flow Injection Analysis. Part II. The (2.2.1) Cryptates of Magnesium and Calcium. AnaL Chim. Acta, 108 (1979) 241. 

D. Espersen, H. Kagenow, and A. Jensen, Flow Injection Analysis and Differential Kinetic Analysis. Arch. Pharm. Chem. Sci. Ed., 8 (1980) 53. 97. K. Kina and N. Ishibashi, Rapid Automated Analysis by Flow Injection Analysis [in Japanese]. Kagaku Kyoto), 33 (1978) 1001. 

This final stage of the analytical process is a key to obtaining acceptable results, particularly in dealing with fast reactions and in differential kinetic analysis. Generated signal/time data pairs are converted into reaction rates or, directly, into analyte concentrations. How this final operation is performed depends on the nature of the applied method. 

Yezerets A, Currier N W, Kim D H, Eadler H A, Epling W S, Peden C H F (2005) Differential kinetic analysis of diesel particulate matter (soot) oxidation by oxygen using a step-response technique. Applied Catalysis B Environmental 61 120-129... 

---