Nonisothermal Kinetics of Dehydration Process of [Sm（m-CIBA）3phen]2·2H2O and [Sm（p-CIBA）3phen]2·2H2O

Compounds [Sm（m-CIBA）3phen]2.2H20 and [Sm（p-CIBA）3phen]2·2H20（m-CIBA=m-chlorobenzoate, pClBA=p-chlorobenzoate, phen=l,10-phenanthroline） were prepared. The dehydration processes and kinetics of these compounds were studied from the analysis of the DSC curves using a method of processing the data of thermal analysis kinetics. The Arrhenius equation for the dehydration process can be expressed as lnk=-38.65-243.90×l0^3/RT for [Sm（m-CIBA）3phen]2·2H2O, and lnk=38.70-172.22×103/RT for [Sm（p-CIBA）3phen]2·2H2O. The values of △H^1, △G^1, and △S^1 of dehydration reaction for the title comnonnds are determined respectively.     

Dehydration performance of a hydrophobic DD3R zeolite membrane

The all silica DDR membrane turns out to be well suited to separate water from organic solvents under pervaporation conditions, despite its hydrophobic character. All-silica zeolites are chemically and hydrothermally more stable than aluminum containing ones and are therefore preferred for membrane applications, including for dehydration, even though these type of membranes are hydrophobic. Permeation of water, ethanol and methanol through an all-silica DDR membrane has been measured at temperatures ranging from 344 to 398 K. The hydrophobic membrane shows high water fluxes (up to 20 kg m⁻² h⁻¹). The pure water permeance is insensitive to temperature and is well described assuming weak adsorption. Excellent performance in dewatering ethanol (N=2$N=2$ kg m⁻² h⁻¹and _αw=1500${\alpha }_{\text{w}}=1500$ at 373 K and _xw=0.18$x_{\text{w}}=0.18$) is observed and the membrane is also able to selectively remove water from methanol (N=5$N=5$ kg m⁻² h⁻¹ and _αw=9${\alpha }_{\text{w}}=9$). Water could also be removed from methanol/ethanol/water (_αwater_/EtOH=1500${\alpha }_{\text{water}/\text{EtOH}}=1500$, _αMeOH_/EtOH=70${\alpha }_{\text{MeOH}/\text{EtOH}}=70$ at 373 K) mixtures, even at water feed concentrations below 1.5 mol%.     

A theoretical study of the dehydration and the dehydrogenation processes of alcohols on metal oxides using MOPAC

Using a semi-empirical molecular orbital method, PM3, and 2-propanol as an example, the dehydration and the dehydrogenation processes of alcohol on oxide catalysts were studied. The catalysts addressed here were four kinds of oxides (Al₂O₃, SiO₂, ZnO, CdO) whose reaction selectivities had been experimentally determined. The usual models consisting of a surface metal ion, several oxide ions and an isopropoxy group were used in calculations. For the dehydration, heats of formation of the models were calculated at each point of the process where the distance between a β-hydrogen of the group and a basic site (i.e. oxygen of the group or a surface oxide ion) or a metal ion was gradually shortened, or where the length of the C–O bond of the group was gradually increased. A reasonable dehydration mechanism was estimated by comparing activation energies calculated from the transitions of the heats of formation. The most probable dehydrogenation mechanism was also estimated in a similar way by gradually making an -hydrogen close to a surface oxide ion, the metal ion or a surface proton. It was concluded that the dehydration proceeds by scission of the C–O bond of the group after its oxygen was attacked by some electrophile on the surface and that the dehydrogenation proceeds by a mechanism in which an -hydrogen of the group was extracted by the metal ion.

Based on the dehydration mechanism thus deduced, alkoxy groups generated by adsorption of the primary, secondary and tertiary alcohols on SiO₂ were calculated in order to estimate the activation energies of their decompositions. In result, the order of the energies was found to be in good agreement with that of the decomposition rates experimentally determined by Kitahara. This agreement gives support to the validity of the mechanism deduced for the dehydration of alcohol.     

Formamide reactions on rutile TiO2(0 1 1) surface

The reaction of formamide over the (0 1 1) faceted TiO₂(0 0 1) surface has been studied by Temperature Programmed Desorption (TPD) and X-ray Photoelectron Spectroscopy (XPS). Two main reactions were observed: dehydration to HCN and H₂O and decomposition to NH₃ and CO. The dehydration reaction was found to be three to four times larger than the decomposition at all coverages. Each of these reactions is found to occur in two temperature domains which are dependent upon surface coverage. The low temperature pathway (at about 400 K) is largely insensitive to surface coverage while the high temperature pathway (at about 500 K) shifts to lower temperatures with increasing surface coverage. These two temperature pathways may indicate two adsorption modes of formamide: molecular (via an η¹(O) mode of adsorption) and dissociative (via an η²(O,N) mode of adsorption). C1s and N1s XPS scans indicated the presence of multiple species after formamide absorption at 300 K. These occurred at ca. 288.5 eV (-CONH-) and 285 eV (sp³/sp² C) for the C1s and 400 eV-(NH₂), 398 eV (-NH) and 396 eV (N) for the N1s and result from further reaction of formamide with the surface.     

Ionic liquid-promoted dehydration of aldoximes: a convenient access to aromatic, heteroaromatic and aliphatic nitriles

A simple and convenient procedure for the synthesis of nitriles by dehydration of aldoximes using an ionic liquid, 1-pentyl-3-methylimidazolium tetrafluoroborate, [pmim]BF₄ under organic solvent-free condition, has been developed. A variety of aromatic, heteroaromatic and aliphatic aldoximes are converted to the corresponding nitriles. The ionic liquid is recovered and reused for subsequent reactions.     

A concise synthesis of indolic enamides: coscinamide A, coscinamide B, and igzamide

A concise synthesis of indolic enamides coscinamide A, coscinamide B, and the brominated tryptamine derivative igzamide is described. Both E- and Z-isomers of these natural compounds were obtained during the thermally assisted dehydration reaction and were tested for antitumor activity. Coscinamide B was found to possess antitumor activity against DU145 with an IC₅₀ of 7.6 μg/mL.     

Effect of Sulfation of Zirconia on Catalytic Performance in the Dehydration of Aliphatic Alcohols

Catalytic dehydration of 2‐propanol and that of 1‐butanol were performed at atmospheric pressure and 150–300°C over ZrO₂ and sulfated ZrO₂ (S/ZrO₂) in a fixed‐bed, tubular reactor. The catalysts were characterized with XRD, elemental analysis, FT‐IR, N₂ physisorption, TG/DTA, TPD, and TPR. The main structures of ZrO₂ and S/ZrO₂ were monoclinic and tetragonal, respectively. As ZrO₂ was modified with sulfuric acid, its surface area and acid amount were greatly increased, whereas the pore volume, the pore diameter, and the particle size were reduced. Both samples owned weak basicity. For both reactions, only dehydration products of alkene and ether were obtained. The alcohol conversion enhanced remarkably with the catalyst acid amount and the surface area as well as the reaction temperature. In addition, the ether selectivity on S/ZrO₂ decreased with raising the reaction temperature. The activation energy was 81.0 kJ/mol in the propene formation from 2‐propanol over S/ZrO₂. The corresponding value was 94.4 kJ/mol for the dehydration of 1‐butanol.     

Kinetics of 2‐Propanol Dehydration over Montmorillonite Clays and Pillared Montmorillonites

Metal ion exchanged montmorillonites (AlM & CrM) and metal oxide pillared montmorillonite (AlPM & CrPM) were prepared and characterized with XRD, FT‐IR, nitrogen adsorption and TPD of ammonia. The pillaring process results in a remarkable increase of interlayer distance, surface area and acid amount of the catalyst. However, increasing the calcined temperature causes reverse effects for the CrPM catalyst. The acid amount decreases in the order of CrPM200 < CrPM300 < AlPM500 < CrM < CrPM400 ≥ CrPM500 ≥ AlM. In the dehydration of 2‐propanol to propene, the reaction follows first order kinetics and the apparent rate constant is related to the catalyst acid amount. Compensation effect occurs in this reaction over the series of catalysts.     

Low-temperature Heat Capacities and Thermodynamic Properties of Hydrated Sodium Cupric Arsenate [ NaCuAsO4·1.5H2O(s)]

Low-temperature heat capacities of the solid compound NaCuAsO4 · 1.5H2O(s) were measured using a precision automated adiabatic calorimeter over a temperature range of T = 78 K to T = 390 K. A dehydration process occurred in the temperature range of T = 368-374 K. The peak temperature of the dehydration was observed to be TD = (371.828±0.146) K by means of the heat-capacity measurement. The molar enthalpy and entropy of the dehyperimental values of heat capacities for the solid(Ⅰ) and the solid-liquid mixture(Ⅱ) were respectively fitted to two polynomial equations by the least square method. The smoothed values of the molar heat capacities and the fundamental thermodynamic functions of the sample relative to the standard reference temperature 298.15 K were tabulated at an interval of 5 K.     

Identification of sterene compounds produced during the processing of edible oils

Samples of maize, rapeseed, soyabean, sunflower, and palm oils, collected at different stages in their respective refining processes, have been analyzed for the presence of dehydrated sterols (sterenes). A total of fifteen compounds were detected. Four have been characterized using model systems designed to investigate their formation. Their elemental composition, and that of the other eleven sterenes, was determined by high resolution mass spectrometry and structures assigned to a further six compounds. These included the -3,5-, -2,5-, -4,6-,-3,5,22-, and -4,6,22- sterenes. Sterenes were not present in crude or alkali neutralized oils. Bleaching introduced a maximum concentration of 5 μg g^?1 of total sterenes into the edible oils. Deodorization is the dominant stage in sterene production resulting in a maximum total concentration of 163 μg g^?1. This increased concentration arises due to dehydration of the sterols and considerable isomerism of the sterenes.