High-temperature Dehydration Research Articles

Structure characterization of native cellulose during dehydration and rehydration

The goal of this study is to investigate the hydration and dehydration induced structural changes of native cellulose. Never dried cotton, and never dried bacterial cellulose with and without added matrix polymer xyloglucan, are examined under the influence of dehydration and rehydration. Significant crystal structure changes were observed in the later stage of drying for both cotton and bacterial cellulose (BC). The 1 % lateral expansion in glucan chain spacing and 17 % decrease of calculated Scherrer dimension were detected for cotton due to the distortion of the structure possibly caused by mechanical stresses associated with drying. No detectable changes on average glucan chain spacings were observed for large BC crystals. However, an average width decrease by 4.4 nm was discovered in the (010) direction, which was more significant than that observed in the (100) and (110) directions. It is hypothesized that co-crystallized elementary fibrils preferentially disassociate along the (010) plane resulting in a significant reduction of crystal width. In the BC-xyloglucan model composite, the presence of xyloglucan does not interfere with the dehydration behavior. Rehydration leads to some structural changes but to a lesser extent than the initial drying. High temperature dehydration induced deformation and crystal size changes are found to be non-reversible due to the removal of the last hydration layer on the cellulose surface.

Reactivated cementitious materials from hydrated cement paste wastes

Hydrated cement pastes subjected to high temperature dehydration have been shown to develop a cementitious behavior upon rehydration that could enable recycling of hydrated cement wastes as alternative binders of high environmental value. In order to evaluate the potential of this recycling option it is first necessary to identify material and process factors affecting the performance of the reactivated cementitious materials produced. This paper presents the findings of a fractional factorial experiment designed to screen factors based on their effect on the strength developed by pastes incorporating materials reactivated from laboratory sourced hydrated cement pastes. Results allowed identification of factor and factor-interaction effects involving 7 of the 9 factors under study, which would be relevant in optimizing the recycling process. Highest strengths observed in the experimental region explored were 20, 32.8 and 39MPa at 7, 28, and 90days, respectively, for reactivated material pastes mixed at 0.7 W/CM ratio.

U–Th–Pb geochronology of zircon and monazite from syenite and pincinite xenoliths in Pliocene alkali basalts of the intra-Carpathian back-arc basin

Phreatomagmatic eruptions in the Lučenec Basin in Slovakia ejected fragments of igneous rocks of unknown age and ranging in composition from gabbro to syenite and orthopyroxene granodiorite – pincinite. Two kinds of syenites with different Fe 3+ contents composed of anorthoclase and interstitial metaluminous trachyte-to-alkali rhyolite glass represent the final products of alkali basalt differentiation at depths of 10 and 15–18 km. Pincinite composed of plagioclase, quartz, orthopyroxene, ilmenite and interstitial peraluminous dacite glass is a quenched supersolidus anatectic melt formed at the depth of 17–20 km by high-temperature dehydration melting of biotite-bearing gneissic protolith. Zircon from pincinite and syenite, and monazite from syenite were dated using excimer laser ablation ICP-MS. The obtained ages cluster at 5.8 ± 0.1 and 5.4 ± 0.1 Ma, thus corroborating the genetic link between the two rock-types and constraining the residence time of at least 300 ± 100 ka of the parental basalt in the deep crustal magma storage zones. The inferred ages overlap the Upper Miocene–Pliocene boundary, and are considerably younger than spatially associated basaltic lava flows dated using the K/Ar method. Consequently, the fluviolacustrine Poltár Formation overlying the maar structure must have sedimented during the Pliocene and not during the Upper Miocene (Pontian) as previously assumed.

High-temperature dehydration behavior and protonic conductivity of RbH2PO4 in humid atmosphere

The high-temperature (HT) properties of RbH{sub 2}PO{sub 4} have been investigated here by several methods. Two anomalies at T{sub p} ({approx}109 {sup o}C) and T{sup '}{sub p} ({approx}276 {sup o}C) in differential scanning calorimetry (DSC) measurement are due to structural transition from tetragonal (phase III) to monoclinic (phase II) and monoclinic to an unidentified phase I, respectively. The initial dehydration event in RbH{sub 2}PO{sub 4} occurs at {approx}250 {sup o}C, leading to the formation of dimer crust (Rb{sub 2}H{sub 2}P{sub 2}O{sub 7}) on the external surface of crystal particles which decelerates the further dehydration process. The conductivity measurement was performed under a highly humidified N{sub 2} condition P{sub H{sub 2O}}{approx}0.56atm to suppress its dehydration. It revealed two reversible superprotonic phase transition at T{sub p} and T{sup '}{sub p}. For the one at T{sup '}{sub p}, the conductivity increases sharply by {approx}2 orders of magnitude and the high-conductivity phase I was stable till melting. However, the other one at T{sub p} shows a relatively small jump in conductivity.

Surface Chemistry of 2-Propanol on TiO2(110): Low- and High-Temperature Dehydration, Isotope Effects, and Influence of Local Surface Structure

Dosed on rutile TiO2(110) at 100 K, the thermal chemistry of 2-propanol in three formsC3H7OH, C3D7OD, and C3H7ODwas characterized using temperature-programmed desorption. Only 2-propanol, propene, and water desorb with no evidence for acetone. The propene forms and desorbs by two paths, a heretofore unreported low-temperature path extending from 300 to 450 K and, concurring with prior work, a high-temperature path peaking between 570 and 580 K. Both paths exhibit isotope effects. The high-temperature path is interpreted in terms of decomposition of 2-propoxy species located on bridging oxygen atom rows. The low-temperature path is attributed to 2-propanol dehydration on undercoordinated Ti4+ ions of the Ti4+ rows. The low-temperature path characteristics vary with the long-range order and bridge-bonded oxygen atom vacancy concentration.

N/p-Type changeable semiconductor TiO2 prepared from NTA

A novel kind of nano-sized TiO2 (anatase) was obtained by high-temperature (400–700°C) dehydration of nanotube titanic acid (H2Ti2O4(OH)2, NTA). The high-temperature (400–700°C) dehydrated nanotube titanic acids (HD-NTAs) with a unique defect structure exhibited a p-type semiconductor behavior under visible-light irradiation ( $$\uplambda\ge420$$ nm, E photon=2.95 eV), whereas exhibited an n-type semiconductor behavior irradiated with UV light ( $$\uplambda=365$$ nm, E photon=3.40 eV).

Room, low, and high temperature dehydration and phase transitions of kernite in vacuum and in air

AbstractKernite Na2B4O6(OH)2·3H2O dehydration in air at high temperature and in vacuum at room temperature has been studied. It was found that kernite easily dehydrates forming a new phase‐I both on heating and in vacuum. The chemical formula Na2B4O6(OH)2·1.5H2O of the new phase‐I has been estimated on the basis of thermogravity analysis. It is triclinic with the unit cell parameters a = 7.047(8), b = 8.76(1), c = 13.08(2) Å, α = 93.40(9), β = 95.32(9), γ = 90.28(9)° changing slightly on pressure reduction. Due to the relatively low temperature (353 K) and reversibility of the kernite ⟷ phase‐I transition an anion of the new phase‐I likely consists of the same chains [B4O6(OH)2]2– like in kernite structure. The high anisotropy of kernite thermal expansion was explained by approaching of NaO chains due to the initial removing of water molecules from kernite crystal structure. The behaviour of the new phase‐I at low temperatures in vacuum was also investigated. A formation of an additional new phase II has been detected at the temperature of 93 K. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Comment on: ?High-temperature dehydration melting and decompressive P?T path in a granulite complex from the Eastern Ghats India? by S. Bhattacharya and R. Kar

Thermodynamic and chemographic modelling of complex reaction textures observed in Mg-Al-rich pelitic granulites is an important tool to unravel the P–T evolutionary history of high-grade rocks. In the Eastern Ghats Belt, India, several studies have been carried out on these fascinating aluminous granulites, and the results of these studies have revealed complex P–T–t histories (Dasgupta and Sengupta 1995; Sengupta et al. 1999; Rickers et al. 2001a, 2001b; Gupta et al. 1999; Dobmeier and Simmat 2002; Dobmeier and Raith 2003). In recent communication, Bhattacharya and Kar (2002) reported reaction textures from a suite of Mg-Al granulites from the Paderu area of the Eastern Ghats Belt. Combining the textural relations and thermodynamic calibration of some construed reactions, the authors have put forward a single phase metamorphic evolution of the area along a ‘clockwise’ pressure–temperature trajectory. Combining the petrological features from the Paderu area with those reported from the Chilka Lake complex, the authors proposed a general tectonic model for the entire Eastern Ghats Belt. Incidentally, the rocks in and around Paderu have been studied in some detail by several other workers (Lal et al. 1987; Mohan et al. 1997; Sengupta et al. 1997). The purpose of this comment is to demonstrate that the conclusions made in the paper are inconsistent with the petrological features described in the text. Further, the thermodynamic treatment used in the paper has serious errors in many places, and hence, is often in complete disagreement with the existing experimental data and theoretical analyses on the Mg-Al-rich assemblages. There are also significant problems arising from the poor quality of the analytical database. Unfortunately, the authors cite only a few published works (mostly their own) ignoring many other relevant studies from this belt (cited above). Our observations are organised according to the sections of the paper.

High-temperature dehydration melting and decompressive P-T path in a granulite complex from the Eastern Ghats, India

The granulite complex of Paderu, in the south central sector of the Eastern Ghats belt, India, consists of closely related pelitic granulites and peraluminous granitoids which could be linked via dehydration melting in pelitic and greywacke-like precursors. The pelitic granulites, including high-Mg-Al sapphirine granulites with early deformation microstructures, also record a high-temperature decompression from ~10 to ~8 kbar at ~1,000 °C, preceding isobaric cooling from above 900 to ~600 °C at 8 kbar. Highly magnesian biotite in the pelitic granulites, the presence of spinel in some of the granitoids, and granitoids of two distinct compositions, namely granite and quartz-monzonite, all suggest dehydration melting in highly magnesian pelitic and greywacke-like precursors. Moreover, high-temperature melting in highly magnesian pelitic precursors is indicated by the migmatitic spinel-bearing layers which, besides having significant abundance of quartz and feldspar, also contain aluminous orthopyroxene and cordierite. These melting reactions, occurring above 9 kbar, may constrain the prograde arm of the P–T trajectory. This and the high-temperature decompression constitute a clockwise P–T path. This clockwise P–T path is consistent with the tectonic model in which crustal thickening and granulite metamorphism in the Eastern Ghats belt is interpreted as the result of homogeneous shortening in a compressional setting.

High-Temperature Reprocessing of Petroleum Oily Sludges

Summary Crude oil tank bottoms and other petroleum oily sludges and emulsions containing paraffins and volatile hydrocarbons can be economically reprocessed with heavy-oil dehydration facilities to recover residual hydrocarbons and to achieve volume reductions. The main factors affecting the use of this alternative are (1) the characteristics of the sludges requiring treatment, (2) the availability of waste heat or existing high temperature (>350°F) dehydration facilities, (3) air emissions from the process, and (4) effluent criteria for treated residues. This paper discusses operational variables that affect high-temperature reprocessing (HTR) and illustrates an application of the process. The example pilot project evaluated the feasibility of high-temperature reprocessing for tank-bottom sludges and skim oils from Kern County, CA, light- (>30°API) oil-producing leases. The process performance was quantified in terms of general operating parameters (flash point and paraffin, oil, water, and solids content); specific constituent analyses for benzene, toluene, ethylbenzene, and xylene (BTEX); and analyses for total petroleum hydrocarbons (TPH) content. Information on the percent removal of these parameters, characteristics of the treated residues, and the hydrocarbon recovery efficiency of the process are presented.

Dehydroxylation of the surface of magnesium oxide by temperature programmed desorption

The surface of magnesia acquires adsorptive-catalytic reactivity only after high temperature (HT) dehydration. Temperature-programmed desorption (TPD) of water reveals at least four energetically different forms of adsorbed water. The most significant HT desorption (above 1000 K) exposes low-coordinated (LC) MgO sites which are active sites for hydrogen chemisorption. Water and hydrogen TPD measurements allow the evaluation of the LC site concentration at about 7.5 × 10 17 and 7.1 × 10 17 site m −2, respectively, which corresponds to about 7% of the total ion surface population. The concentration of the LC sites confirms the much higher heterogeneity of the real MgO surface than that based on simple surface area modelling (about 2.1 × 10 17 site m −2). A dehydration mechanism for the energetically heterogeneous surface of magnesia is postulated.

Crystallinity of AlN Film Deposited by Reactive Sputtering Method

Effects of water vapor in a sputtering chamber on the AlN film crystallinity deposited by reactive sputtering method have been investigated. A very small water vapor pressure of (2-6)×10-4Pa resulted in a degradation of the AlN crystals. High temperature dehydration before deposition made it possible to synthesize high-quality c-axis oriented AlN films at low temperature.

Adsorption and 129Xe n.m.r. of xenon in silver-exchanged Y zeolites: Application to the location of silver cations

The adsorption isotherms and 129Xe n.m.r. chemical shifts of xenon in silver-exchanged yAgNaY zeolites ( y from 5 to 100%) after high-temperature (400°C) dehydration as well as subsequent oxidation were measured at 26°C. A three-site sorption model taking into account adsorbateadsorbate interaction was developed that reproduces simultaneously the adsorption isotherms and the chemical shift vs. concentration curves up to xenon loadings of about 6 sol atoms supercage . The upfield displacements of the chemical shifts in the silver-exchanged zeolites with respect to NaY are attributed to the interaction of xenon with a small portion of the supercage silver cations, probably those unlocalized or residing on crystallographic SIII sites.

Partial melting and the origin of metapelitic granulites in the Southern Marginal Zone of the Limpopo Belt, South Africa

Two potentially realistic models exist to explain the origin of the granulite-facies rocks of the Southern Marginal Zone: (i) CO 2-fluxing, inducing the necessary high-temperature dehydration reactions and, (ii) melting of hydrous minerals to yield an H 2O-undersaturated granitic melt in equilibrium with a dehydrated granulitic assemblage. Petrographic and field evidence from the Bandelierkop Quarry in the Southern Marginal Zone indicate a sequence of melting reactions involving muscovite and biotite. Relict textural evidence indicates that the reaction responsible for the generation of most of the melt, Bi + Sil + Qz + Plag = Melt + Ga + Ksp, was fluid-absent. The melting reactions can be shown to have occurred during the prograde metamorphic path, with the highest-temperature reaction (Bi + Qz + Plag = Hy + Cord + Melt), occurring at approximately peak metamorphic conditions (850°C and less than 9.5 kbar). This suggests a fluid-absent mode of granulite formation. A subsequent retrograde reaction (Cord + Ksp + H 2O = Ky + Qz), related to a rise in α H 2O during in-situ crystallisation of the melt, did not destroy the granulite assemblages and hypersthene remains stable in areas of the Southern Marginal Zone that record pressures of greater than 6.5 kbar during retrogression.

秋田・新潟のグリーンタフの変質と貯留岩性状

Reservoir property of Green Tuff is controlled by the initial volcanic rock facies and alteration. Some hydrothemal alteration increases the secondary porosity and permeability. Altered basalt lava is the main reservoir in the Yurihara oil field. Four depth zones are defined by characteristic secondary minerals: 1) smectite, 2) thomsonite-corrensite, 3) laumontite-albite, 4) laumontite-prehnite-pumpellyite-chlorite. These alteration is estimated to have taken place at sub-seafloor right after the basaltic eruption by hydrothermal fluid originated from seawter. The main oil production zone is from the prehnite zone. High temperature (150-220°C) dehydration alteration have prevented porosity reduction caused by low temperature alteration. Green Tuff in the Katakai gas field is mainly composed of rhyolite. They are mostly recrystallized to form quartz, albite, sericite, calcite, dolomite, siderite, and chlorite. Rhyolite lava is rich in Na and albite, poor in K and sericite. In contrast, hyaloclastite (or pumice tuff) is rich in K and sericite, poor in Na and albite. The alteration in Green Tuff in the Katakai gas field is divided into dolomite-dominant type alteration, which is rich in Fe-Mg carbonate and poor in chlorite, and chlorite-dominant alteration. Dolomite type rhyolite lava is rich in intercystalline pore and dissolution pore, poor in pore plugging clay minerals, and serves as productive reservoir. Andesitic rocks in the MITI Sado-oki are suffered from diagenesis and hydrothermal alteration. The center of hydrothermal alteration zone is reached out by acidic fluid, and shows high permeability.

HEAT TREATMENT OF CHOPPED ALFALFA IN ROTARY DRUM DRYERS

ABSTRACT This paper deals with the heat treatment of alfalfa chops during the high temperature dehydration process. It outlines the dryer characteristics, difficulties and potential errors in measuring temperatures in the dryer, computation techniques, the relationships between moisture and temperature during drying, and the potential effect of dehydration on the destruction of the insect Hessian Fly due to elevated temperatures. From the analysis based on an existing computer model for dehydration of alfalfa chops, and the available field data, it is shown that the dried chops will attain a temperature of 90°C or higher when the input temperatures are between 500°C and 800°C. These conditions apply to the drying of wet alfalfa (moisture content more than 55 percent wet basis). The plant material loses a large portion of its moisture in the first few seconds in the dryer. The rapid release of moisture may cause the rupture or detachment of particles such as eggs, larva, pupa, and insects from the plant ma...

The nutrient and glycoalkaloid content of a new potato meal

The nutrient and glycoalkaloid content of a new potato meal produced as a by-product of starch manufacture using low temperature dehydration was determined. Comparisons were made between the new potato meal and the previously manufactured meal which was prepared by high temperature dehydration. The glycoalkaloid content of the new potato meal was 15.53mg α-chaconine and 4.75mg α-solanine per 100g meal compared to 15.79mg α-chaconine and 7.83mg α-solanine in the potato meal produced by high temperature dehydration. The new potato meal contained 2% more protein and 1.9, 3.4 and 1.2 times more niacin, riboflavin and thiamin, respectively than the previous by-product. The potassium and phosphorus concentrations were approximately 2.0 and 0.2%, respectively. Other minerals were found in lesser concentrations with the sodium content being only 7.4mg/100g potato meal. A 28g serving would provide approximately 5, 7 and 4% of the RDA for protein, niacin and thiamin, respectively.

Surface characterization of some selected zinc oxide samples II: Zinc oxide prepared by thermal decomposition of zinc carbonate

Zinc oxide was thermally dehydrated in vacuo at different temperatures in the range 100 – 500 °C. Nitrogen adsorption measurements were carried out on the different samples; the specific surface areas, the total pore volumes and other surface parameters were estimated and correlated. The adsorption isotherms were characterized by hysteresis phenomena over the entire temperature range. The initial increase in the area of the hysteresis loop up to 300 °C is attributed to the increase in molecular water loss. The high temperature (greater than 300 °C) dehydration resulted in the appearance of high pressure hysteresis loops which are attributed essentially to the sinterability of the zinc oxide sample. The specific surface area initially increases at 200 °C and then gradually decreases to the maximum temperature studied (500 °C). The early increase in nitrogen surface area is due to the loss of physisorbed water together with a contribution revealed by the increase in the magnitude of the Brunauer-Emmett-Teller C constant. The gradual decrease in nitrogen surface area above 200 °C was followed by different methods of analysis, the V 1- t method, the n S- n R method and pore size distribution curves. The change in porosity characteristics accompanying the development of some narrower (or micro) pores was interrelated with the estimated adsorption values.

Phase transformation in the cupric magnesium oxide system

Due to the incomplete removal of OH groups, dehydration at 500°C of solid solutions of magnesium ions in Cu(OH)2 and of copper ions in Mg(OH)2 formed by coprecipitation leads to the formation of nonequilibrium cupric magnesium oxyhydroxide compounds with the structures of CuO and MgO, respectively. As a result of high-temperature dehydration, cupric oxide and solid solutions are formed in which up to 20 at. % of magnesium in MgO is replaced by copper ions.

High-temperature dehydration of NiNa 3P 3O 10.12H 2O : Yu G Zonov et al, Neorg Mater, 8 (6), June 1972, 1083–1089 ( in Russian)

High-temperature dehydration of NiNa 3P 3O 10.12H 2O : Yu G Zonov et al, Neorg Mater, 8 (6), June 1972, 1083–1089 ( in Russian)