Adsorption Microcalorimetry Research Articles

New insights in large-pores mesoporous silica microspheres for hemostatic application

Hemorrhages are still considered a common cause of death and despite the availability of different hemostatic agents it is still necessary to develop more effective hemostats for bleeding managements in emergency situations. Herein, large-pores mesoporous silica microspheres (MSM) were synthesized, and their surface was modified to enrich the hydroxyls population with the aim of achieving a material with enhanced water adsorption capacity and high hemostatic ability. The success of surface modification was investigated by Fourier Transform Infrared spectroscopy (FT-IR) and thermogravimetric analysis (TGA), which confirmed the increase in the amount of surface hydroxyl groups. A hemolysis assay as well as a clotting test were carried out to evaluate the hemocompatibility and hemostatic ability, respectively. It was found that the modified material presented the lowest hemolytic ratio and the lowest clotting time. The novelty of the paper is mainly due to the coupling of the hemostatic ability test with the adsorption microcalorimetry of water. In fact, being the water adsorption on the material surface a crucial factor in the hemostatic activity, microcalorimetry was used for the first time to study the adsorption of water and estimate its heat of adsorption. The data obtained showed that the modified MSM presents a surface able to adsorb a higher amount of water, compared to the pristine MSM, with a low molar heat of adsorption (about 35 kJ/mol), which renders the modified MSM presented in the present study an excellent candidate for producing novel hemostats.Graphical

Influence mechanism of leaching agent anions on the leaching of aluminium impurities in ionic-type rare earth ores: A DFT simulation combined with experimental verification

The aluminium impurity present during the leaching process of ionic-type rare earth ores increases the complexity and cost of the subsequent dealumination procedure, causing the loss of rare earth elements. Understanding the interactions between minerals and impurities is crucial for grasping interfacial reactions. However, the mechanism by which anions influence the adsorption behaviour of Al3+ remains unclear. This study examined the impact mechanisms of four typical leaching agent anions (SO42-, Cl-, NO3–, and CH3COO–) on the interaction between Al3+ and the kaolinite (001) surface using density functional theory (DFT). According to DFT calculations, the order of adsorption energy of Al3+ on the kaolinite (001) surface in the presence of anions is as follows: Al3+ < Al3+ in aluminium sulfate < Al3+ in aluminium chloride < Al3+ in aluminium nitrate < Al3+ in aluminium acetate. The adsorption strength of Al3+ on the kaolinite (001) surface is weakened to varying degrees by the presence of anions. Specifically, under the influence of acetate anions, it is difficult for Al3+ to adsorb and form bonds on the kaolinite (001) surface. In contrast, Al3+ can still adsorb mainly through Al-O ionic bonds under the influence of the other three anions. The density of states analysis showed that the 3p orbitals of Al atoms and the 2p orbitals of O atoms primarily contribute to the Al-O bond near the Fermi energy level. Experimental results from adsorption capacity tests, microcalorimetry, and zeta potential measurements support the DFT simulations, indicating that Al2(SO4)3 is the most easily adsorbed on the kaolinite surface, followed by AlCl3 and Al(NO3)3, with (CH3COO)3Al being the most difficult to adsorb. Column leaching tests further verified that adding CH3COO– to the leaching agent solution at pH > 4.5 can inhibit the leaching of aluminium impurities, enabling the efficient separation of rare earth elements from aluminium impurities, and reducing the aluminium content in the leachate.

Accurate Measurements of NH3 Differential Adsorption Heat Unveil Structural Sensitivity of Brønsted Acid and Brønsted/Lewis Acid Synergy in Zeolites.

Differential adsorption heats of NH3 on a series of zeolites, including MOR, MFI, FER, and BEA, are accurately measured to probe their acidity using flow-pulse adsorption microcalorimetry. Initial adsorption heats of NH3 at Brønsted acid sites (BAS) vary between 105 to 136 kJ/mol, depending on framework aluminum amounts and topography structures of zeolites. A Brønsted/Lewis acid synergy between BAS and proximate tricoordinated framework-associated aluminum species is identified to generate super acid sites with initial adsorption heats of NH3 around 150 kJ/mol, but occurs only in the MFI zeolites and sensitively depends on the Si/Al ratio. These accurate data of NH3 differential adsorption heats unveil structural sensitivity of BAS and Brønsted/Lewis acid synergy in zeolites and provide experimental benchmark data for fundamental understanding of acidity and acid-catalysis of zeolites.

Solid acid catalysts comprising heteropoly acids supported on SiO2, TiO2 and ZrO2: A microcalorimetric investigation of catalyst acidity and new insight into the mechanism of alcohol dehydration over HPA

Keggin-type heteropoly acids (HPAs) have strong Brønsted acidity and are widely used as acid catalysts. The aim of this work is the systematic characterisation of the acid strength of HPA catalysts comprising H3PW12O40 and H4SiW12O40 supported on SiO2, TiO2 and ZrO2 with 10–100% HPA loading and testing their activity in dehydration of alcohols to gain new mechanistic insight regarding the role of bulk-type and surface-type HPA catalysis in this reaction. The HPA catalysts were prepared by impregnation from an aqueous solution and characterised using BET, XRD, TGA, DRIFTS and ICP–OES. The acid strength of HPA catalysts was determined by NH3 adsorption microcalorimetry and found to decrease in the order HPA/SiO2 > HPA/TiO2 > HPA/ZrO2. For each type of HPA catalyst, the acid strength increased with increasing HPA loading. This can be attributed to HPA-support interaction reducing the strength of HPA proton sites at low HPA loadings. The activity of HPA catalysts was tested in the gas-phase dehydration of MeOH and i-PrOH in a fixed-bed reactor. Evidence was obtained that alcohol dehydration over HPA catalysts in a steady-state flow system occurs via the surface-type rather than bulk-type catalysis as suggested hitherto. This follows from a strong correlation between the reaction rate and the number of surface proton sites in HPA catalysts.

Low-Energy Ion Scattering Intensities from Supported Nanoparticles: The Spherical Cap Model

Supported nanoparticles are of great importance to many technologies like fuel processing and chemical synthesis using catalysts and electrocatalysts, energy storage and generation using fuel cells and batteries, electrochemistry, magnetic information storage, and more. Low-energy ion scattering spectroscopy (LEIS) with noble gas ions like He+ is a powerful tool for the characterization of nanoparticles dispersed across flat support surfaces due to its ability to probe the elemental composition in the topmost atomic layer of a surface, providing quantitative information regarding the size and number density of nanoparticles. In this work, we present a derivation of the LEIS intensities expected from nanoparticles and the support material as a function of the average particle size, their number per unit area, and their contact angle with the support when modeled as spherical caps of the nanoparticle material dispersed over the surface of a flat support. The model assumes that the ion intensities are determined only by the physical blocking of linear ion trajectories and independent of the tilt angle of the local surface relative to the incident and scattered ion directions, an assumption we support by quantitative modeling of published data which tested tilt-angle effects. The model is a generalization to arbitrary contact angles of the hemispherical cap model, which assumes 90° contact angle and has been widely used to model spectroscopic signals in LEIS (and also in Auger and photoelectron spectroscopies) during nanoparticle growth. This new model quantitatively reveals how LEIS signals are sensitive not only to the diameter and number density of the nanoparticle but also to their contact angle (or height/diameter ratio). With the use of additional data (e.g., from microscopy or adsorption microcalorimetry), the model presented here will enable more accurate determination of the average size, shape, and number density of supported nanoparticles based on LEIS intensity measurements.

Soft-templated NiO–CeO2 mixed oxides for biogas upgrading by direct CO2 methanation

The catalytic performance in the direct CO2 methanation of a model biogas is investigated on NiO–CeO2 nanostructured mixed oxides synthesized by the soft-template procedure with different Ni/Ce molar ratios. The samples are thoroughly characterized by means of ICP-AES, XRD, TEM and HR-TEM, N2 physisorption at −196 °C, and H2-TPR. They result to be constituted of CeO2 rounded nanocrystals and of polycrystalline needle-like NiO particles. After a H2-treatment at 400 °C for 1 h, the surface basic properties and the metal surface area are also assessed using CO2 adsorption microcalorimetry and H2-pulse chemisorption measurements, respectively. At increasing Ni content the Ni0 surface area increases, while the opposite occurs for the number of basic sites. Using a CO2/CH4/H2 feed, at 11,000 cm3 h−1 gcat−1, CO2 conversions in the 83–89 mol% range and methane selectivities >99.5 mol% are reached at 275 °C and atmospheric pressure, highlighting the very good performances of the investigated catalysts.

Aluminosilicate-Supported Catalysts for the Synthesis of Cyclic Carbonates by Reaction of CO2 with the Corresponding Epoxides.

Functionalized aluminosilicate materials were studied as catalysts for the conversion of different cyclic carbonates to the corresponding epoxides by the addition of CO2. Aluminum was incorporated in the mesostructured SBA-15 silica network. Thereafter, functionalization with imidazolium chloride or magnesium oxide was performed on the Al_SBA-15 supports. The isomorphic substitution of Si with Al and the resulting acidity of the supports were investigated via 27Al magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy and NH3 adsorption microcalorimetry. The Al content and the amount of MgO were quantified via inductively coupled plasma optical emission spectroscopy (ICP-OES) analysis. The anchoring of the imidazolium salt was assessed by 29Si and 13C MAS NMR spectroscopy and quantified by combustion chemical analysis. Textural and structural properties of supports and catalysts were studied by N2 physisorption and X-ray diffraction (XRD). The functionalized systems were then tested as catalysts for the conversion of CO2 and epoxides to cyclic carbonates in a batch reactor at 100 or 125 °C, with an initial CO2 pressure (at room temperature) of 25 bar. Whereas the activity of the MgO/xAl_SBA-15 systems was moderate for the conversion of glycidol to the corresponding cyclic carbonate, the Al_SBA-15-supported imidazolium chloride catalysts gave excellent results over different epoxides (conversion of glycidol, epichlorohydrin, and styrene oxide up to 89%, 78%, and 18%, respectively). Reusability tests were also performed. Even when some deactivation from one run to the other was observed, a comparison with the literature showed the Al-containing imidazolium systems to be promising catalysts. The fully heterogeneous nature of the present catalysts, where the inorganic support on which the imidazolium species are immobilized also contains the Lewis acid sites, gives them a further advantage with respect to most of the catalytic systems reported in the literature so far.

TiO2 Catalyzed Dihydroxyacetone (DHA) Conversion in Water: Evidence That This Model Reaction Probes Basicity in Addition to Acidity

In this paper, evidence is provided that the model reaction of aqueous dihydroxyacetone (DHA) conversion is as sensitive to the TiO2 catalysts' basicity as to their acidity. Two parallel pathways transformed DHA: while the pathway catalyzed by Lewis acid sites gave pyruvaldehyde (PA) and lactic acid (LA), the base-catalyzed route afforded fructose. This is demonstrated on a series of six commercial TiO2 samples and further confirmed by using two reference catalysts: niobic acid (NbOH), an acid catalyst, and a hydrotalcite (MgAlO), a basic catalyst. The original acid-base properties of the six commercial TiO2 with variable structure and texture were investigated first by conventional methods in gas phase (FTIR or microcalorimetry of pyridine, NH3 and CO2 adsorption). A linear relationship between the initial rates of DHA condensation into hexoses and the total basic sites densities is highlighted accounting for the water tolerance of the TiO2 basic sites whatever their strength. Rutile TiO2 samples were the most basic ones. Besides, only the strongest TiO2 Lewis acid sites were shown to be water tolerant and efficient for PA and LA formation.

Structural and acidity analysis of heteropolyacids supported on faujasite zeolite and its effect in the esterification of oleic acid and n-butanol

Most of the supporting catalytic materials seek to improve classical chemical processes that are less environment-friendly. The association of heteropolyacids (HPA) and zeolites has shown to be interesting for heterogeneous catalysis. In the present study, zeolite Y (faujasite) was modified by the incipient insertion of 12-tungstophosphoric (HPW) and 12-tungstosilicic (HSiW) acids for application in the esterification reaction of oleic acid with n-butanol. The fine chemical product (butyl oleate) is used in a variety of applications (e.g., plasticizers, lubricants). The catalysts (x%HPA/Y; x = 3, 6 and 12%) were characterized by EDXRF, XRD, FT-IR, multinuclear MAS NMR (27Al, 29Si, and 31P), SEM, low temperature N2 physisorption, thermal methods (TG/DTG), pyridine (Py) gas desorption (Py-TPD) and microcalorimetry of Py adsorption in liquid phase. The resulting acid composites showed advantages over both pristine solids with adequate nature, dispersion, stability, accessibility, and strength of active sites. High oleic acid conversions (70% for 12%HSiW/Y and 96% for 12%HPW/Y) with 100% selectivity to butyl oleate were obtained under these conditions: acid: alcohol ratio 1:2; 0.2 g of catalyst; 100°C and 1 h reaction. No leaching of the active phases was detected, and the best catalysts were used three times, keeping fair their initial conversion.

Mesoporous Zirconium Oxide Prepared by Anchoring W, Mo, Nb, Ta Using Peroxo Precursors: Influence of the Oxoanions on the Pores Size and the Hydrothermal Catalysts Stability for Cellulose Conversion

Efficient and sustainable cellulose conversion into chemicals requires the design of heterogeneous catalysts with controlled acid–base properties, mesoporosity and excellent stability in hydrothermal conditions. To this end, modified zirconia with anchored W, Mo, Ta and Nb oxoanions were prepared by ionic exchange using peroxo precursors of the selected transition metals. Modified zirconia samples were characterized by X-ray diffraction, N2 isotherms, FTIR of pyridine adsorption and microcalorimetry of ammonia adsorption. If the nature of the oxoanion tunes slightly the catalysts Lewis acid strength or density, it influences strongly their mesoporosity with mesopores in the range of 10 nm for ZrTa and ZrNb. Upon Pt loading, all the Pt-modified zirconia are effective to catalyze C–C and C-O cleavage during cellulose hydrogenolysis leading to PG as main short polyols with the co-formation of 2,5-hexanedione over ZrNb and ZrTa. Most important, ZrNb and ZrTa exhibit excellent water tolerance without any leaching nor structure modification. Combined to their mesoporosity, these features make ZrNb and ZrTa, true solid Lewis acids with high potential in the frame of bulky biomass conversion in hot waterierGraphical Abstract

On the design of mesostructured acidic catalysts for the one-pot dimethyl ether production from CO2

Dimethyl ether (DME) production from hydrogenation of CO2 based on two-function (redox and acidic) catalysts is receiving increasing attention due to the high demand for alternative and green fuels. In this work, we propose different mesostructured acidic metal oxides as methanol dehydration catalysts to be used as physical mixtures in combination with a commercial Cu-based redox catalyst (CZA) for the CO2-to-DME one-pot production. Al-MCM-41, TiO2 and TiO2-ZrO2 mixed oxides, obtained through Sol-Gel methods, either in a conventional or Evaporation-Induced Self-Assembly approach were selected as mesostructured acidic systems and compared with a commercial zeolite (ferrierite). The regular mesoporous structure should render the active sites of the acidic catalyst easily accessible for CO2 and H2 and allow a homogeneous dispersion of the redox phase inside the mesopores in view of a possible development of bifunctional catalysts (redox + acidic). With the aim of understanding how the textural and acidic properties can be correlated with the performances and eventually design efficient dehydration catalysts, a careful study on the acidic sites was performed by both adsorption microcalorimetry with ammonia and FTIR-monitored adsorption of pyridine. The results of the performances highlighted a higher activity toward methanol dehydration for catalysts featured by Brønsted sites (zeolite and Al-MCM-41); as for catalysts with Lewis sites only (TiO2, Ti0.77Zr0.23O2) better performances were shown in case of systems presenting sites of moderate strength (Ti0.77Zr0.23O2). In the light of the above, Al-MCM-41 and TiO2-ZrO2 demonstrated to be the most promising mesostructured dehydration catalysts in terms of selectivity to DME.

The dehydrogenation of butane on metal-free graphene

The dehydrogenation of alkane feedstock to produce alkenes is a significant and energy intensive industrial process, generally occurring on metals and metal oxides. Here, we investigate a catalytic mechanism for the dehydrogenation of butane on single-layer, metal-free graphene using a combination of ab initio quantum chemical calculations and adsorption microcalorimetry. Dispersion-corrected Density Functional Theory (DFT) is employed to calculate transition states and energy minima that describe the reaction pathways connecting butane to the two possible products, but-1-ene and but-2-ene. The deprotonations occur with moderate energy barriers in the 0.54 eV-0.69 eV range. A strong agreement is observed between the results of the adsorption energies calculated by DFT (0.40 eV) and the measured differential heat of adsorption of n-butane on a graphitic overlayer. We conclude that the active-site for this catalytic reaction is a metal-free graphene vacancy, created by removing a carbon atom from a single-layer graphene sheet.

Acrolein production by oxidative coupling of alcohols over zinc and cobalt aluminate spinels enlightened by adsorption calorimetry study

This work reports on the production of acrolein by oxidative coupling of biosourced alcohols (methanol and ethanol). This reaction is performed in a two-step process using iron molybdate catalyst to produce formaldehyde and acetaldehyde and zinc and cobalt aluminate spinels, with or without vacancies, to perform the cross-aldolization of aldehydes. In this study, adsorption microcalorimetry of NH3 and SO2 was used to determine the acid-base properties of the catalysts. The catalytic activity was monitored and correlated to catalysts acid-base properties. Moreover, to enlighten the behavior of reactants over the surface and the mechanism of the reaction, an extensive adsorption microcalorimetric study using acetaldehyde and formaldehyde as probe molecules was performed to determine molar enthalpies, molar entropies, thermokinetic parameters but also energy spectra. This broad calorimetric study provided a better understanding of the reaction and allowed to confirm the preferential adsorption of formaldehyde compared to acetaldehyde thus justifying the absence of crotonaldehyde in the products of the catalytic reaction.

Surface functionalization of handleable silica-based mesoporous materials for CO2 sequestration: Synthesis, characterization and performance.

Two different types of silica monolith based on commercial hydrophobic Aerosil200 and hydrophilic Sipernat320 (Evonik) were successfully covalently functionalized with different amines as CO2 sequestrants. 3-aminopropyltriethoxysilane (AMPS) was used for a first functionalization and applied as it is or as linker to extend the chain length with diglycine (diGly) and triglycine (triGly). The physico-chemical characterization of the samples comprehends nitrogen adsorption at -196 °C to determine surface area and porosity and thermogravimetric analysis (TGA) to evaluate the thermal stability of the materials and quantify the extent of functionalization. CO2 and N2 adsorption microcalorimetry, coupled with FTIR spectroscopy, was used to evaluate the ability of the materials to selectively sequestrate CO2 against N2 in post-combustion procedures and the reversibility of the process. The comparison with a powdery commercial activated carbon, taken as reference, evidences the good adsorption capacity (comparable to that of the carbon reference) of monoliths from Sipernat 320 bringing a short aliphatic chain and terminal -NH2 groups (more than 700 μmol/g of CO2 sequestrated at 30 °C), and the advantages in term of easy storage and recoverability, with respect to powdery adsorbents.

Synthesis of Dimethyl Carbonate by Transesterification of Propylene Carbonate with Methanol on CeO2-La2O3 Oxides Prepared by the Soft Template Method.

In this study, CeO2, La2O3, and CeO2-La2O3 mixed oxide catalysts with different Ce/La molar ratios were prepared by the soft template method and characterized by different techniques, including inductively coupled plasma atomic emission spectrometry, X-ray diffraction, N2 physisorption, thermogravimetric analysis, and Raman and Fourier transform infrared spectroscopies. NH3 and CO2 adsorption microcalorimetry was also used for assessing the acid and base surface properties, respectively. The behavior of the oxides as catalysts for the dimethyl carbonate synthesis by the transesterification of propylene carbonate with methanol, at 160 °C under autogenic pressure, was studied in a stainless-steel batch reactor. The activity of the catalysts was found to increase with an increase in the basic sites density. The formation of dimethyl carbonate was favored on medium-strength and weak basic sites, while it underwent decomposition on the strong ones. Several parasitic reactions occurred during the transformation of propylene carbonate, depending on the basic and acidic features of the catalysts. A reaction pathway has been proposed on the basis of the components identified in the reaction mixture.

Texture and surface sites of treated and as-prepared SWNT using experimental and simulation methods

Surface properties of single wall carbon nanotubes (SWNT) subjected to different treatments were studied. Nitrogen, argon and carbon dioxide were used to study the adsorption properties and its influence by the presence of surface sites on SWNT, acid treated SWNT and heat treated SWNT. Special attention was paid to carbon dioxide adsorption, by means of adsorption microcalorimetry and Monte Carlo simulation considering the presence of surface oxygen groups. Monte Carlo simulation showed that these surface groups affect the adsorption properties of oxidized SWNT and their corresponding enthalpies of adsorption. The SWNT model systems, with open or closed nanotubes and with or without oxygen in their walls, showed agreement with the experimental enthalpies of adsorption. Thereby, Monte Carlo simulation and experimental enthalpies of adsorption are suggested as an adequate method of characterization of SWNT adsorption sites.

Kerogen nanoscale structure and CO2 adsorption in shale micropores

Gas storage and recovery processes in shales critically depend on nano-scale porosity and chemical composition, but information about the nanoscale pore geometry and connectivity of kerogen, insoluble organic shale matter, is largely unavailable. Using adsorption microcalorimetry, we show that once strong adsorption sites within nanoscale network are taken, gas adsorption even at very low pressure is governed by pore width rather than chemical composition. A combination of focused ion beam with scanning electron microscopy and transmission electron microscopy reveal the nanoscale structure of kerogen includes not only the ubiquitous amorphous phase but also highly graphitized sheets, fiber- and onion-like structures creating nanoscale voids accessible for gas sorption. Nanoscale structures bridge the current gap between molecular size and macropore scale in existing models for kerogen, thus allowing accurate prediction of gas sorption, storage and diffusion properties in shales.

Accessibility and strength of H-acceptor hydroxyls of ordered mesoporous silicas probed by pyridine donor

Ordered mesoporous silica (OMS) is an important and useful material for a variety of applications, including catalysis, adsorption, sensing and controlled drug delivery. The surface chemistry and the silanol groups on OMS pores are key properties for the potential modification and application of this material. This research aimed to synthesize (using standard protocols) and differentiate the accessibility and strength of the H-acceptor Si–OH from FDU-12, SBA-16, MCM-41 and SBA-15 by pyridine (Py) donor, where the first two have cubic pore structures and the last two have hexagonal pore structures. Donor–acceptor properties were assessed by calculation of the surface Si–OH densities by thermogravimetry (TG), H2O-TPD/MS, and 29Si MAS and CP/MAS NMR. The nature of the Si–OH groups on these materials was determined to be hydrogen-bonding sites using FT-IR spectroscopy of Py adsorption. The reactivity of these silanol groups was probed by Py-TG and slurry microcalorimetry of Py adsorption in cyclohexane. Differences in accessibility and reactivity were discussed considering the total potential sites on the surface (nOH) versus the actual sites that can react with the Py molecule (nPy). By using microcalorimetry, it was possible to quantitatively distinguish the strength of the sites: The acidity order was approximately the same as the relative amount of silanol groups (Si–OH) and Py on the surface of the OMS materials (αPy): FDU-12 > MCM-41 ≥ SBA-16 > SBA-15.

Sustainable acrolein production from bio-alcohols on spinel catalysts: Influence of magnesium substitution by various transition metals (Fe, Zn, Co, Cu, Mn)

Acrolein is a widely used intermediate of synthesis for value-added compounds in a number of domains of application. This work reports on the sustainable synthesis of acrolein by oxidative coupling of bio-alcohols, which constitutes a very promising alternative to fossil fuel-based production. The synthesis is performed in two sequential reactors, using an iron molybdate catalyst for oxidation and then a magnesium aluminate spinel where magnesium is partly or totally substituted by transition metals (Fe, Zn, Co, Cu, Mn) as a catalyst for cross-aldolization. The acid-base properties of the latter catalysts were determined using SO2 and NH3 adsorption microcalorimetry. Adsorption microcalorimetry was also used to study the adsorption properties of the reactants, with formaldehyde, acetaldehyde and propionaldehyde as probe molecules, and was complemented by a FT-IR investigation of reactant adsorption in order to better understand the mechanisms of adsorption and reaction. Acrolein production was found to be correlated to the ionic radius of the transition metals used in the catalysts, indicating that electronic effects are likely a factor influencing the acrolein production.

Calcium Phosphate Catalysts for Ethanol Coupling to Butanol and Butadiene

The catalytic conversion of ethanol to butanol and butadiene at 633 K and atmospheric pressure (7 vol% ethanol) was studied over calcium phosphate materials pretreated over a wide temperature range. For calcium phosphate pretreated at or below 923 K, the resulting solid had an apatite structure identified by X-ray diffraction and strong acid sites probed by triethylamine (TEA) adsorption microcalorimetry. The low temperature pretreated materials were not effective at ethanol coupling reactions but instead were highly selective to acid-catalyzed products ethene and diethyl ether. Pretreatment of calcium phosphate at 973 K transformed the apatite structure to β-tricalcium phosphate, which exposed both acid and base sites evaluated by TEA and CO2 adsorption microcalorimetry. High temperature pretreated calcium phosphate catalysts formed the coupling products butanol and butadiene during ethanol reaction. The butadiene selectivity was improved by supporting calcium phosphate on zirconia. The influence of catalyst structure on the activity and selectivity of calcium phosphates was elucidated for the conversion of ethanol.