title: A microscopic model of the Tian-Calvet microcalorimeter, cell design for a faster response, and measurement by a continuous procedure.
abstract: The transient heat conduction equation was used as the microscopic model of the Tian-Calvet microcalorimeter. It was verified by comparing simulated and experimental calorimetric curves and used to guide sample cell design for a faster response time, for which it gave the guidelines to minimize the heat flow distance and use a heat flux that is uniform and onto the whole face of the thermopile sensor. The resulting sample cell was disc-shaped with the sample powder placed in it as a thin 0.2 mm layer on a stainless steel base with a wall thickness of 0.5 mm that covered the whole face of the thermopile on which it was placed. The rise time of the heat response curve to a step change in sample temperature, which is the response time for measuring the differential heat released, was 45 s. The response curve from a gas dose returned to the baseline within 400 s, which is the time needed to measure the integrated heat in a pulsed dosage. The accuracy of the heats measured by the calorimeter was verified by comparison with data in the literature on the adsorption of ethanol and ammonia on HZSM-5 and adsorption of methanol and ammonia on SAPO-34. The differential heat of methanol adsorption on SAPO-34 at 333 K and ammonia adsorption on HZSM-5 at 423 K were measured by both the conventional discontinuous procedure and a new continuous procedure. In the continuous procedure, gas was continuously dosed at a very slow flow rate that was kept slow enough for the gas and adsorbate to reach quasi-equilibrium. The continuous procedure has the advantages of high resolution results and a simpler experimental procedure, and a calorimetric curve could be measured within 3 h.
authors.affiliation: Department of Chemical Engineering, Tsinghua University, Beijing 100084, China.
authors.forename: Y
authors.initials: Y
authors.lastname: Kobayashi
authors.affiliation: Key Lab Orogen Belts and Crustal Evolut, School of Earth and Space Sciences, Peking University, Beijing 100871, China.
authors.forename: F
authors.initials: F
authors.lastname: Wang
authors.affiliation: Department of Chemical Engineering, Tsinghua University, Beijing 100084, China.
authors.forename: Q X
authors.initials: QX
authors.lastname: Li
authors.affiliation: Department of Chemical Engineering, Tsinghua University, Beijing 100084, China.
authors.forename: D Z
authors.initials: DZ
authors.lastname: Wang