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A remarkable number of scientific papers are available in the literature about the process of hydrothermal carbonization (HTC), also called wet or hydrous pyrolysis, applied to biomass substrates. However, the biggest share of it focuses on the characterization of HTC products obtained from different feedstocks. Only a few works are available on the process thermodynamics, particularly about the determination of the enthalpy change and the related heat release or absorption during HTC, which is a key parameter to understand the nature of the process and to evaluate the heat requirements for the design of industrial scale HTC plants. The present review summarizes the research carried out with the aim of assessing the process enthalpy for HTC. Two main approaches have been identified and described, and the research works are sorted into two categories: enthalpy calculation based on the direct application of the Hess’s law and enthalpy evaluation based on differential heat measurement. The hypotheses and results obtained by the different authors are critically analysed and discussed, and directions for further research are proposed.

We report H2 adsorption capacities reaching 0.05 wt % at 303 K and at 1 atm H2 pressure on solid-state CuCl-exchanged [Al]-SSZ-13 and [B]-SSZ-13 zeolites. Differential heat of H2 adsorption is found in the range between 16 and 48 kJ mol H2–1 on Cu(I)-SSZ-13 at 323 K and isosteric heat of adsorption is found between 20 and 55 kJ mol H2–1 on Cu(I)-[B]-SSZ-13 at temperatures between 293 and 323 K. Strong interactions between H2 and the copper cations in Cu(I)-SSZ-13 are evidenced using Rietveld refinements of neutron powder diffraction patterns revealing Cu–deuterium (D2) distances of 2.3(2) and 2.41(1) A. A temperature-dependent Cu(I) migration—away from the six-membered ring (6MR) and eight-membered ring (8MR)—is related to the high adsorption capacities of the samples at 303 K. At 10 K, access to Cu(I) at 6MR is sterically hindered by framework oxygen atoms (Cu–Oframework distance of 2.196(5) A), rationalizing the low H2 adsorption capacities of Cu(I)-SSZ-13 samples as compared to Na-SSZ-13 at 77 K.

We present the critical analysis of the utilization of CO2 adsorption calorimetry/volumetry and TPD-CO2 for the determination of the Mg–Al mixed oxide basicity. The aim of work is the description and the evaluation of both methods with respect to the fact when the same types of CO2 adsorption complexes are involved. Critical parts of basic sites determination are originally discussed for both methods. In TPD-CO2, the process of the purging of non-specifically physisorbed CO2 is stressed. In CO2 adsorption calorimetry, the differential heat of CO2 distinguishing CO2 adsorption on weak basic sites and non-specific CO2 physisorption is stressed. Both methods are applied on series of selected Mg/Al mixed oxides varying in Mg/Al molar ratio and alkali co-cation. We show that the generally used TPD-CO2 does not provide complete information about basic sites since some weak sites form unstable CO2 species and these species could not be involved in TPD experiments. All our TPD-CO2 experiments reflect at 0–485 °C those CO2 adsorbed in the range of the differential heat of CO2 above 30–32 kJ mol−1.

The adsorption of CO2 coupled to calorimetry is a state-of-the-art technique for characterizing the basic properties of solids. In this paper, we show that the differential heat and entropy curves measured upon CO2 adsorption on a basic solid can be reasonably estimated from a single CO2 isotherm with no need for any independent heat (calorimetric) measurement. Our method relies on two important observations: (1) formulation of generalized F-H-TS thermodynamic isotherms, the former (F) being directly generated from the raw CO2 isotherms, and (2) the presence of unexpected enthalpy-entropy compensation effects upon CO2 adsorption linking the integral enthalpy and entropy of adsorption until saturation for different solids. Our thermodynamic method has been validated using a broad library of basic solids with variable site strength and heterogeneity. Finally, a new scale of basicity is proposed using the parameters fitted from the thermodynamic isotherm (free energy basis) as descriptors of basic strength. This method opens an avenue to the inference of site strength of basic solids without the need for expensive calorimeters.

The isotherms and differential heats of water vapor adsorption on Na- and Ca-saponite samples are measured. It is shown that the successive stages of hydration of the internal surface of this mineral appear as waves or inflections in the adsorption isotherms and maxima in the dependences of the differential heat on the adsorption value. The compositions of Na+ and Ca2+ aquacations in single- and double-layer saponite hydrates are determined. The heats of interaction between water molecules and interlayer Na+ cations in single-layer saponite hydrates and between Na+ cations and the ion exchanger matrix are estimated.

Molecular dynamics simulations of hydrated Na–LSX zeolite at 300 K were performed with the explicit inclusion of the polarization of water. The Si/Al ratio of LSX is 1 and the number of water molecules per unit cell ranged from 0 to 224 to represent a range of hydration. The calculation results show that the dipole moments of water molecules increase with increasing hydration. By using the SPC–FQ water model instead of the SPC/E water model, the differential heat of adsorption showed similar trends in both models, whereas the differential potential energies between water–water and between water–zeolite are more sensitive to hydration.

The specific heat capacities of aqueous solutions of 2-(hexyloxytetraethoxy)ethanol (C 6 E 5 ) have been measured from 283 to 338 K within the whole composition range by DSC. Changes of specific, partial and apparent molar heat capacities of investigated system were analysed and considered as a effect of structural transformations. For each solution, the temperature dependences of the differential heat flow were also analysed in order to find the curve of phase coexistence, i.e. the boundary between one- and two-phase area for the examined system.

An extended dual kinetic model allows to fit the n-heptane cracking results working in a wide range of reaction conditions. The duality of the model is provided by the contribution of monomolecular and bimolecular cracking mechanisms. It takes into account the role played by the olefins formed on the global cracking or added within the feed. Furthermore by means of this model and the kinetic parameters obtained when cracking n-heptane on ZSM-5, it has been observed that, while some characterization techniques show a homogeneous zeolite surface from the point of view of the active sites, rigorous kinetic experiments point to the possibility that the reactant sees a heterogeneous surface with, at least, two groups of cracking active sites. Those differentiated active sites give different cracking rates and different activation energies for the process and, in the case of ZSM-5, could be assimilated to sites pointing to the 10R channels and sites pointing into the crossing of the 10R channels, mainly due to differences in kid site location and confinement effects. (C) 2015 Elsevier Inc. All rights reserved., Financial support by the Ministerio de Economia y Competitividad of Spain (MINECO) [Programa Estatal (Project MAT2012-31657) and Programa Consolider-Ingenio 2010 (Project MULTICAT)] is gratefully acknowledged.

The interactions of carbon monoxide with Lewis acid sites of zeolites were investigated using microcalorimetric and temperature programmed desorption (TPD) techniques. Carbon monoxide was adsorbed at 25°C on transition-metal ion-exchanged FAU (Y and X) and MOR type zeolites. The differential heats of adsorption ( Q dif ) indicate the heterogeneity of the acid sites, in all the investigated systems. The specific interactions of CO with the strongest acid sites were recognized. The results of TPD confirm that CO molecules were adsorbed on the sites of different strength.

The system polyacrylamide (PAA) — water at 018, it is equal to Q L. The mechanism of the gradual solution of PAA is proposed. As the system sorbs water, it passes through the consecutive stages of formation of the clathrate-like compounds AG·2H2O and AG·(17−18)H2O (AG is an amido group of PAA) with subsequent formation of a perfect aqueous solution of compound I.

For various chemical processes, heat and mass evaporative flows are generated through vacuum control in order to ensure isothermal operations or flexible tracking of temperature trajectories. To study such processes, a 5-liter bench-scale evaporative calorimeter is presented in this paper. As an example, the application of this microcomputer-controlled calorimeter to the on-line identification of the differential heat evolution during batch evaporative crystallizations is reported. It is shown that satisfactory estimated results are obtained by means of a recursive least-squares policy. These results could allow an extension of diagnostic and control possibilities for many common processes which operate in vacuum conditions.

An adsorption microcalorimeter for the simultaneous determination of the differential heat of adsorption and the adsorption isotherm for gas-solid systems are designed, built, and tested. For this purpose, a Calvet heat-conducting microcalorimeter is developed and is connected to a gas volumetric unit built in stainless steel to record adsorption isotherms. The microcalorimeter is electrically calibrated to establish its sensitivity and reproducibility, obtaining K=154.34±0.23 WV−1. The adsorption microcalorimeter is used to obtain adsorption isotherms and the corresponding differential heats for the adsorption of CO2 on a reference solid, such as a NaZSM-5 type zeolite. Results for the behavior of this system are compared with those obtained with commercial equipment and with other studies in the literature.

Solutions of blockcopolymers (POE-b-PI-b-POE) in fluids of interacting aqueous nanodroplets (W/O microemulsions) are studied. The interaction strength between the (pseudo) two components is measured by the shift of the percolation temperature relative to that of the pure microemulsion. A quantitative measure of the interaction, the differential heat of solution, is thermodynamically related to the slopes of the equilibrium temperature of the system with varying monomeric nanodroplet concentration and the experimental percolation line in the presence of copolymer.

Combined adsorption and calorimetric measurements have been used to examine the mechanism of micropore filling in active carbons. It appears that for carbons with medium and high degrees of burn-off (above 45–50%), the adsorption at low pressure does not correspond to the filling of narrow micropores, which are virtually absent, but to the initial step of the secondary filling (adsorption on the walls of wide micropores). The differential heat of adsorption is smaller than in narrow micropores and the extrapolation of the initial part of the non-linear Dubinin–Radushkevich plot corresponds approximately to the surface area of the supermicropores.

Carbon dioxide adsorption isotherms by synthetic mordenite are determined over the ranges 10 −5 atm P −5 atm P Differential heat curves show two adsorption ranges with different energetic characteristics. At the transition a very marked maximum appears. The integral molar entropy and specific heat of adsorbed phase are calculated. Two methods for adsorbed phase density determination are proposed: (i) The first, straight from maximal adsorbed amount at 50 atm. where adsorption isotherms level out. (ii) The second, based on adsorption potential theory with an elementary graphical determination. When the adsorbed phase density is so determined, Dubinin's equation can be successfully applied.

In this paper, high temperature calorimeter which is France SETARAM has been modified and introduced. Differential heats of adsorption for gas/solid system over the temperature range from ambient temperature to 800K could be carried out in this apparatus. In the experimental procedure the amount of adsorption for gas or vapour could he measured by a light spot microbarometer. The conversion factors for the apparatus have been determined through a electric heating me thod instead of standard materials which are usually used in temperature program process,fly using this apparatus the heat of adsorption for pyrodine on H-Y zeolite at different temperatures have been measured.

The present paper consists of an attempt to interpret theoretically the experiments of Solbakken and Reyerson on the magnetic susceptibility of nitric oxide adsorbed on silica gel. A primitive model is used in which the axis of the NO molecule is regarded as frozen in space and the crystalline field mixes the 3II1/2 and 3II3/2 states. To explain the experimental data it is necessary that the size of the crystalline potential increase with temperature. Possible justification of this assumption is found in the fact that the observed differential heat of adsorption increases with temperature. More refined calculations do not seem warranted in the absence of magnetic data over a wider temperature range including possibly magnetic resonance measurements.