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Transition state theory (TST) based on activation parameters computed using quantum mechanics calculations combined with the polarizable continuum model (QM/PCM) is a fundamental tool for investigating reaction rates in the liquid phase. In conventional QM/PCM methods, thermodynamic data and partition functions for a solute are often derived from a quasi-ideal gas treatment (IGT) widely implemented in commercially available computation packages. This approach tends to overestimate entropy because calculations of thermodynamic parameters in the liquid phase ignore hindered translational and rotational modes in real solutions. The present work formulated partition functions for more realistic solutes hindered by surrounding solvent molecules in conjunction with the basic QM/PCM concept. In addition, a configuration partition function for solute molecules at a standard concentration of 1 mol dm−3 was incorporated using a simple lattice model. The canonical partition function and thermodynamic functions were derived based on statistical thermodynamics for localized systems. Expressions for rate coefficients within TST were also derived with a consistent formalism based on the standard state selected in partition function calculations. The performance of the proposed method was assessed by predicting rate coefficients for three different Diels–Alder reactions and comparing these with experimental results. QM/PCM calculations at the G4//ωB97X-D/6-311++G(d,p)/IEF-PCM level of theory with corrections for the dispersion and repulsion energies were performed to obtain the electronic structures of stationary points on potential energy surfaces as a means of finding activation enthalpy, entropy and Gibbs energy values based on revised partition functions as well as predicting rate coefficients. The activation Gibbs energies obtained from our proposed method were lower than those obtained from the IGT method due to reasonable entropy computations. The proposed method overestimated the rate coefficients by one to two orders of magnitude compared to the experimental values, whereas the IGT method underestimated them by the same amount. This discrepancy arises because the proposed method calculates the partition function from the viewpoint of a localized system, whereas the IGT method calculates it from the viewpoint of a non-localized system. Given that actual liquids exist in a state between non-localized and localized systems, it is essential to formulate the partition function in a way that more accurately represents the liquid state. [ABSTRACT FROM AUTHOR]

The ammonium dinitramide‐based ionic liquid propellant (ADN‐based ILP), which is a mixture of ADN, monomethylamine nitrate (MMAN), and urea, is a low toxic monopropellant with a higher performance than that of hydrazine. To clarify the combustion wave structure of ADN‐based ILP, which has low volatility, we focused on the relationship between the phase state and temperature in ADN‐based ILP combustion and on clarifying the gas‐liquid phase reaction. The combustion still image and temperature distribution of ADN‐based ILP were obtained by strand burning tests with a high‐speed camera. As a result, two stages of the stable temperature region were found in the gas‐liquid phase. The pressure dependences of temperature in the stable temperature region were compared with the vapor pressure curves of some chemical substances and with the decomposition temperatures of ADN, MMAN, and urea. Then, it was inferred that the thermal decompositions of ADN, MMAN, and urea, as well as the evaporation of urea had occurred at the first stage of the stable temperature region. Also, it was found that the liquid ammonium nitrate had been dissociated at the second stage of the stable temperature region. For a report on the existence of dissociation products of MMAN and urea vapor on the burning surface at 1.2 MPa, the dissociation of MMAN and evaporation of urea would occur at the first stage of the stable temperature region at 1.2 MPa. As stated above, the combustion wave structure of ADN‐based ILP was developed at 1.2 MPa. [ABSTRACT FROM AUTHOR]

Natural hazard triggering technological disasters (Natech) pose a major risk to chemical industries. Natural disasters, such as earthquakes, floods, and tsunamis, may cause massive fires, explosions, and toxic chemical release into the environment. Thus, Natech risks have recently attracted considerable research attention. Although Natech‐related case studies are seldom reported in the literature, the results obtained thereof facilitate concrete risk assessments and countermeasure implementation against natural hazards. This article presents a case study on tsunami risk assessment performed by Asahi Kasei Corporation, Japan, based on four steps: (1) review of Natech events caused by the 2011 Great East Japan Earthquake, (2) hazard identification at the plant, (3) risk assessment considering human casualties, equipment loss, environment, and business continuity, and (4) evaluation and implementation of appropriate countermeasures. The risks posed by tsunamis were identified and analyzed. The inundation heights of Level‐1 and Level‐2 tsunamis were estimated to be 1 and 10 m, respectively. A tsunami evacuation tower and tidal wall were built as appropriate countermeasures to prevent or mitigate fatalities, loss of containment, and business interruption. The results obtained in this study facilitate adequate preparedness of chemical plants against future tsunami occurrences. [ABSTRACT FROM AUTHOR]