Oscillatory Behavior and Anomalous Heat Evolution in Recombination of H2 and O2 on Pd-based Catalysts

• Published in: Industrial & engineering chemistry research 2015-07
• Main Authors: Lalik, Erwin, Drelinkiewicz, Alicja, Kosydar, Robert, Szumełda, Tomasz, Bielańska, Elżbieta, Groszek, Dan, Iannetelli, Angelo, Groszek, Martin
• Format: Article
• Language: English
• ISSN: 0888-5885; 1520-5045
• DOI: 10.1021/acs.iecr.5b00686

Gas flow-through microcalorimetry has been applied to study the Pd/Al2O3 type catalysts in the exothermic hydrogen recombination process: H2 + O2 → H2O, in view of the potential application in the passive autocatalytic recombination (PAR) technology. The flow mode experiments revealed thermokinetic oscillations, i.e., the oscillatory rate of heat evolution accompanying the process and the corresponding oscillations in the differential heat of process, in sync with oscillatory conversion of hydrogen. Mathematical evidence has been found for the deterministic character of the aperiodic oscillations. In the outburst of quasiperiodic oscillations of large amplitude, the instances of differential heats as high as 700 kJ/mol H2 have been detected, exceeding the heat of the gaseous water formation from elements (242 kJ/mol H2) by a factor of nearly 3. Another occurrence of anomalously high thermal effects has been measured in calorimetric oxygen titration using 0.09 μmol pulses of O2 injected onto hydrogen- or deuterium-saturated catalysts, including 2%Pd/Al2O3, 5%Pd/Al2O3 and 2%PdAu/Al2O3. Repeatedly, the saturation/oxidation cycles showed the heat evolutions in certain individual O2 pulses as high as 1100 kJ/mol O2, i.e., 550 kJ/mol H2, again 2 times as much as the heat of water formation. It has been pointed out that it seems prudent for the PAR technologists to assume a much larger rate of heat evolution than those calculated on the basis of a standard thermodynamic value of the heat of water formation, in order to account for the possibility of large thermokinetic oscillation occasionally appearing in the recombination process of hydrogen. A possible relation of the anomalous heat evolution to an inadvertent occurrence of low energy nuclear reaction (LENR) phenomena is also briefly considered.