Enthalpy-Entropy Compensation Effect in Saturated Solutions on an Example of Polynuclear Aromatics According to Thermodynamics at Melting Temperature.

A thermodynamic the influence of temperature on the logarithm of the considered quantity is expressed by bifunctional functional terms (1/T, lnT). For this purpose, the Apelblat & Manzurola (A&M) equation was used for extended model dissolution analysis of 12 aromatic hydrocarbons in tetralin and decalin vs. temperature for saturated solutions. The A&M equation was found to be thermodynamically compensatory in the sense of Enthalpy-Entropy-Compensation (EEC) while limiting melting temperature Tm=∆mH∆mS. The coefficients for the functional terms A1 vs. A2 are a linear relationship, with a slope called the compensation temperature Tc, as ratio of average enthalpy to average entropy. From this dependence, it has been shown that the approximation of ∆cp=∆mS¯ is justified, also assuming the average entropy. Regarding the term representing the activity coefficients, modifications to the A&M equation were proposed by replacing the intercept and it was shown that the new form correctly determines ∆mH. However, the condition is that the molar fraction of the solute exceeds x > 0.5 moles. It has been shown that the simplest equation referred to van 't Hoff's isobar also allows the simultaneous determination of enthalpy and entropy, but these quantities do not always come down to melting temperature.

Ni-Supported Pd Nanoparticles with Ca Promoter: A New Catalyst for Low-Temperature Ammonia Cracking.

In this paper we report a new nanometallic, self-activating catalyst, namely, Ni-supported Pd nanoparticles (PdNPs/Ni) for low temperature ammonia cracking, which was prepared using a novel approach involving the transfer of nanoparticles from the intermediate carrier, i.e. nano-spherical SiO2, to the target carrier technical grade Ni (t-Ni) or high purity Ni (p-Ni) grains. The method that was developed allows a uniform nanoparticle size distribution (4,4±0.8 nm) to be obtained. Unexpectedly, the t-Ni-supported Pd NPs, which seemed to have a surface Ca impurity, appeared to be more active than the Ca-free (p-Ni) system. A comparison of the novel PdNPs/Ni catalyst with these reported in the literature clearly indicates the much better hydrogen productivity of the new system, which seems to be a highly efficient, flexible and durable catalyst for gas-phase heterogeneous ammonia cracking in which the TOF reaches a value of 2615 mmolH2/gPd min (10,570 molNH3/molPd(NP) h) at 600°C under a flow of 12 dm3/h (t-Ni).