Thermal Reaction of Aluminum Alkoxide in Glycols

Thermal reaction of aluminum isopropoxide in glycols at 300°C yielded the glycol derivatives of boehmite. The physical properties of the products and the aluminas obtained by calcination strongly depended on the crystallite size of the boehmite derivatives, which seems to be controlled by the heterolytic cleavage of the C-O bond of HO(CH₂) _n OAI = formed by alkoxide exchange between aluminum alkoxide and glycol. The product had a unique honeycomb texture, which was preserved on calcination to form a transition alumina.     

Synthesis of morphology-controlled mesoporous transition aluminas derived from the decomposition of alumina hydrates

Aluminum hydroxides were synthesized through the acidification of sodium aluminate solution using single organic diester or diacid as pH adjustor and aluminum chelating agent. The obtained alumina hydrates are investigated by XRD, SEM, IR and TG. Bayerite firstly formed at room temperature, and its morphology greatly varied with the pH adjustors used, which probably attributes to different kinetics of the acidification. The bayerite can evolve to gibbsite and boehmite after the hydrothermal treatment at 100 °C and 145 °C, respectively, where these alumina hydrates show diverse morphologies. After the calcination, these alumina hydrates of bayerite, gibbsite and boehmite could pseudomorphically transform to the corresponding η-, χ- and γ-aluminas, respectively, exhibiting different structural and textural properties. Interestingly, the transition aluminas derived from the aluminum tri-hydroxides, bayerite and gibbsite, both display locally organized mesopores, while no such meso-structure can be observed in γ-alumina obtained from the aluminum mono-hydroxide, boehmite. The changes of bayerite during calcination are investigated detailed. The dehydration of non-porous bayerite accompanied with the formation of meso-structured transition aluminas, where the meso-structure becomes more and more clearly defined and pore size expands with the calcination temperature increasing.     

氢氧化铝活化对水热法制备勃姆石的影响

采用氢氧化铝粉体为原料,活化后通过水热法制备勃姆石。研究了氢氧化铝活化对勃姆石颗粒尺寸的影响,并讨论了相关机理。研究结果表明：未活化氢氧化铝水热反应所得产物颗粒粒径为2μm,经过加热（160～220℃）活化的氢氧化铝,水热反应所得产物的颗粒粒径在0.3～2μm变化。对活化氢氧化铝和水热反应中间产物进行表征,由结构分析推测作用机制：氢氧化铝加热活化过程中生成少量勃姆石,这些勃姆石在氢氧化铝水热反应转化为勃姆石（AlOOH）的过程中成为晶种,活化温度升高和活化时间延长,勃姆石晶种数量增加,氢氧化铝水热反应所得产物的颗粒粒径减小,并且加快了水热反应速率。该工作有望提供一种氢氧化铝水热法制备勃姆石的新途径和相关基础理论。     

Pore structure of aluminas derived from the alkyl derivatives of boehmite

The alkyl derivatives of boehmite (alkoxyalumoxanes; AlO(OH)_1?x (OR) _x ) were synthesized by the reaction of aluminum triisopropoxide in straight-chain primary alcohols at 300 °C for 2 h in an autoclave. In the present work, pore structures of aluminas obtained by calcination of the alkyl derivatives of boehmite were examined. The alumina obtained from the ethyl derivative of boehmite had a broad pore-size distribution, while the pore-size of the alumina obtained from the dodecyl derivative of boehmite distributed in a narrow range in the mesopore region. The mode pore diameter of the latter alumina increased with the increase in calcination temperature (as-syn., 39 Å; 600 °C, 54 Å; 800 °C, 58 Å; 1000 °C, 68 Å), but narrow pore-size distribution was maintained even after calcination at high temperatures.     

Application of metal triflate catalysts for the trans-esterification of Jatropha curcas L. oil with methanol and higher alcohols

This paper describes an experimental study on the application of metal triflate salts for the (trans‐) esterification of fatty esters (triolein, methyl oleate, methyl linoleate), fatty acid (oleic acid), as well as Jatropha curcas L. oil with methanol and higher alcohols (ethanol, n‐propanol, iso‐propanol, iso‐butanol, tert‐butanol). The effect of the metal type (scandium, bismuth, aluminium, lanthanum, copper, zinc) and process conditions on reaction performance were evaluated. Highest conversions were obtained with Al(OTf)₃. Reaction of triolein with methanol gave 99 mol% conversion at 165 °C for 1 h and the main product was the methyl ester. In addition, partial methoxylation of the carbon–carbon double bonds in the fatty acid chains was observed, though their fraction in the mixture was less than 20 mol%. The trans‐esterification reaction was also successfully performed using higher alcohols, giving >95 % conversions for ethanol, n‐propanol, iso‐propanol and iso‐butanol, whereas tert‐butanol was not reactive. For the reaction of oleic acid with methanol, quantitative esterification, partial methoxylation of the carbon–carbon double bonds and the formation of small amounts of a lactone was observed. The methodology using Al(OTf)₃ was successfully performed on the trans‐esterification reaction of JO (FFA content of 2.1 wt%) with various alcohols. Key properties (viscosity, pour point and cloud points) of the (branched) Jatropha esters were determined. The best cold‐flow properties were obtained for the iso‐propyl esters of JO, with cloud point and pour point of ?3 and ?24 °C, respectively.     

Dissolution of coal with NaOH-alcohol: Effect of alcohol species

Methanol, ethanol, straight-chain propanol, isopropanol, straight-chain butanol, sec-butanol, tert-butanol, straight-chain pentanol, and iso-pentanol were used for the reaction of coal with NaOH-alcohol at 290 °C for 1 h. All the products dissolved in pyridine with an extraction yield > 80 wt%. Straight-chain alcohols are less reactive than the secondary alcohols owing to the differences in hydrogen donating ability.     

Porosity of alumina gels prepared from solutions of aluminium nitrate in various alcohols

Mercury porosimetry and nitrogen adsorption measurements have been made on a series of alumina gels prepared by the passage of gaseous ammonia into solutions of aluminium nitrate nonohydrate in various alcohols. The values of surface area calculated from mercury intrusion curves and nitrogen isotherms (BET method) are in reasonable agreement with the macroporous gels, but the restricted penetration of mercury into the mesopore structures results in larger values of areas when calculated by nitrogen adsorption. Marked differences have been obtained in the pore size distribution of gels prepared in various alcohols, including the isomers of propanol and butanol. The alcohol appears to play a double role: (a) by replacing water at the solid-liquid interface (it promotes aggregation-cementation); (b) by decreasing the solubility (it reduces the rate of Ostwald ripening). Propan-1-ol and propan-2-ol tend to promote aggregation-cementation and hence the formation of a well-defined mesopore structure, whereas butan-1-ol and heptan-1-ol appear to favour particle growth and the development of larger pores.     

3-D micro-ceramic components from hydrothermally processed carbon nanotube–boehmite powders by electrophoretic deposition

Boehmite/multi-wall carbon nanotube (MWCNT) composite powders were prepared by hydrothermal processing. Starting chemical of aluminum acetate powders (2Al(OH)(C₂H₃O₂)₂) and MWCNTs were mixed for the formation of stoichiometric boehmite powders in an attempt to synthesize MWCNT-reinforced boehmite nano-powders via hydrothermal synthesis at 200 °C for 2 h. Kinetically stable suspensions of MWCNT–boehmite composite powders were prepared and subsequently electrophoretic deposition (EPD) was applied to obtain complex shape products in the form of micro-gears. It is shown that the EPD technique is a powerful tool to manufacture small components in a short time. Detail TEM observations also indicated that hydrothermal processing provides an ideal environment to obtain homogeneous mixtures of MWCNT–boehmite powders due to effective surface functionalization of MWCNTs under hydrothermal conditions.     

Synthesis, characterization and catalytic applications of mesoporous γ-alumina from boehmite sol

In this study, boehmite sols were used as aluminum precursors for preparing mesoporous alumina (MA) having crystalline framework walls in the presence of non-ionic surfactants as structure directing agents. Nitrogen physisorption showed that aluminas prepared in this way displayed very rich porosities with large mesopores, and both the pore volumes and the pore sizes increased with the surfactant concentration. The improved textural parameters in the samples should be attributed to the three-dimensional interconnected scaffold-like channels, which were formed by randomly ordered stacking and condensing of rigid boehmite nanoparticles with the aid of the surfactant. TEM observations revealed that the precursor morphology had an important effect on the textural properties of the mesoporous alumina. The sample with a corrugated platelet-like morphology exhibited a large surface area of 463 m²/g, which was reduced to 81 m²/g after calcination at 1200 °C, indicating a strong resistance to sintering. This material, with its improved textural properties, crystalline framework walls and high thermal stability, not only could increase the dispersion of the active catalytic species, but also could enhance the diffusion efficiency and mass transfer of reactant molecules when employed as catalyst supports. As examples, our MA samples demonstrated a remarkable enhancement in the catalytic performances for both reactions of SO₂ catalytic reduction by CO and catalytic combustion of methane.     

Low-Temperature Formation of Aluminum Orthophosphate

Factors influencing the low-temperature formation of AIPO₄ and its precursor phases, AIPO₄· x H₂O (1 x 2), were investigated. AIPO₄ formed by reaction between 33.3 wt% H₃PO₄ solution and alumina. Five aluminas (three anhydrous and two hydrated) were utilized. Each differed in particle size, surface area, and crystallinity. The reaction temperatures investigated were 113°, 123°, and 133°C. The high-surface-area aluminas were sufficiently reactive in the phosphoric acid solution at these temperatures to produce crystalline reaction products. However, only hydrated forms of AIPO₄, AIPO₄· x H₂O (1 x 2), crystallized directly out of solution. x generally decreased as the curing temperature was increased. Upon dehydration of these hydrated reaction products, anhydrous AIPO₄ was formed, primarily in the berlinite and/or cristobalite modifications. Both the temperature of reaction and the alumina used influence the hydrates that form. In turn, the hydrates which form, the macroscopic assemblages into which they may crystallize, and the morphologies of the crystallites all affect the polymorphic form and the crystallinity of the anhydrous AIPO₄ phase ultimately produced on dehydration. Phase-pure and highly crystalline AIPO₄-cristobalite (the high-temperature modification) was formed by the dehydration of AIPO₄·H₂O at a temperature as low as 113°C.     

Structural and textural factors influencing the rate of butene isomerization on aluminas

The isomerization ofn-butene was used as a model reaction on a series of aluminas in order to find relationships between their catalytic activity and their structural and textural characteristics. The results show that the nature of the precursor, either gibbsite or boehmite, from which the alumina is obtained plays an important role in the catalytic activity. If the same precursor is considered the presence of pentacoordinated aluminum on the surface generates sites which influences deeply the product selectivity. Thus, besides structural aspects, detectable by MAS NMR, and textural factors such as surface area and pore size distribution, there are more subtle effects linked to the nature of the precursor which are not explained so far.     

A study on the aliphatic energetic plasticizers containing nitrate ester and nitramine

The aliphatic energetic plasticizers with three and four –CH₂ between nitrate ester and nitramine were synthesized to obtain a plasticizer that is more stable than N-butyl-N-nitratoethyl nitramine (BuNENA) with two –CH₂. First, amino alcohol compounds such as propylamino propanol (PAP) and ethylamino butanol (EAB) as a precursor of energetic plasticizer were synthesized. However, unlike in BuNENA synthesis, various side reactions occurred in the nitration of amino alcohols. Fortunately, it was possible to considerably suppress the formation of side products in the nitration of PAP by using a solvent and an appropriate concentration of nitric acid. In addition, an energetic plasticizer with higher oxygen content was obtained through the nitration of intermediate, amide alcohol, which was formed in the synthesis of EAB.     

Effect of Temperature on Structural and Optical Properties of Boehmite Nanostructure

The nanocrystalline boehmite, γ‐AlOOH, was synthesized by the hydrothermal method using AlCl₃·6H₂O and urea as precursors, and the effect of different annealing temperatures resulting in different phases of alumina (Al₂O₃) was obtained. The effects of different temperature on the phase and micrographs of the prepared γ‐AlOOH nanostructures were investigated. The obtained products were characterized by X‐ray powder diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy techniques. The XRD results show that with the increasing temperature, the transformation of boehmite into well‐crystallized α‐Al₂O₃ and the morphology from nanoplatelets with spindle‐like edges to vermicular structure take place. The crystallite size and lattice parameters were calculated by Rietveld refinement. The convincing evidence for the crystal phase of the as‐prepared and annealed samples was provided by FTIR spectra. The Raman spectra unveil the change in vibrational modes of the phase transition alumina.     

以三嵌段共聚物为模板介孔氧化铝的形貌控制合成

以三嵌段共聚物作为结构导向剂,采用水热法合成了片状和棒状介孔氧化铝,采用X射线衍射仪、场发射透射电子显微镜、低温氮气吸脱附实验对合成的介孔氧化铝的晶相、形貌和介孔结构进行表征。研究结果表明,三嵌段共聚物的引入能够有效调控氧化铝的形貌、介孔结构以及孔参数。三嵌段共聚物在氧化铝前驱体表面的吸附诱导了晶体的取向生长,并最终形成了棒状氧化铝。     

Surface and pore structure of alumina derived from xerogel/aerogel

The alkyl derivatives of boehmite were prepared by solvothermal reaction of aluminum isopropoxide in n-alcohols (ethanol, 1-butanol, 1-hexanol, 1-octanol and 1-dodecanol) and the products were recovered as aerogel/xerogel by the removal of the solvent at the end of reaction. Aerogel or xerogel can be obtained simply by using only a reaction vessel (autoclave) and the obtained products were composed of plate-like particles having a well-developed boehmite structure. The alumina powders obtained by calcination of these products had relatively large pore-volumes ranging from 1.35 to 2.56 cm³/g. Transformation into α-Al₂O₃ was retarded even after calcination at 1200 °C. The effect of n-alcohols used in the solvothermal reaction on the phase, morphology and pore-texture of the alumina samples are discussed.     

The relation between the adsorption characteristics of polar organic compounds (alcohols and acids) and their orientation polarization on activated carbon

The high temperature adsorption of n-alcohols (methanol, ethanol, propanol and butanol) and the aliphatic acids (formic, acetic, propionic and buteric) was studied on steam activated carbon using micro Chromatographic technique. In the light of the theory of polarization, it was found that the adsorption of these polar alcohols depends on their orientation polarization. A relation was found between the high temperature adsorption characteristics and the orientation polarization of the alcohols and the aliphatic acids on activated carbon.     

不同含磷物种对氧化铝性质的影响

采用NaAlO_2-Al_2(SO_4)_3法制备拟薄水铝石,在制备过程中分别加入不同的磷源前驱体,考察不同含磷物种对拟薄水铝石孔结构、热稳定性和红外酸的影响。结果表明:在合成拟薄水铝石过程中适当引入助剂磷能够制备出大孔容、大孔径的拟薄水铝石;磷改性拟薄水铝石的孔容、孔径与磷源前躯物盐的分子结构有关,其中,以单斜晶系晶体的磷酸氢二铵为磷源合成的拟薄水铝石的孔容、孔径最大,而以磷酸二氢铵为磷源的拟薄水铝石耐高温性能最强,酸性最高。     

Effect of vapor phase ethylenediamine crosslinking of matrimid on alcohol vapor sorption and diffusion

This work examines the sorption, diffusion, and polymer relaxation behavior for water and C1‐C7 alcohol vapors at 30 °C in ethylenediamine vapor‐phase crosslinked Matrimid. Ethylenediamine is sufficiently volatile that crosslinking can occur by exposing the polymeric film to saturated vapor, in contrast to more conventional means of dissolving the crosslinker in a solvent and immersing the polymeric film in the solution. The vapor‐phase exposure method avoids the use of additional solvent and undesired solvent‐induced swelling. Sorption isotherms demonstrate that water and C1‐C5 alcohols do not appreciably differ for unmodified and crosslinked Matrimid; however, an approximate 90% reduction in sorption was determined for hexanol and heptanol. A minor impact on diffusion coefficients for water, methanol, and ethanol was observed, while those of propanol and butanol were reduced over an order of magnitude. Relaxation kinetics were similarly unchanged for water and C1‐C3 alcohols, while being significantly reduced for butanol and higher alcohols. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44771.     

Effect of boehmite sol on the performance of alumina microfiltration membranes

Precursor film method was used to prepare highly permeable ceramic microfiltration membranes in this work. The performance of alumina microfiltration membranes was improved by adding boehmite sol in the membrane precursor film. With increasing the boehmite sol content, the effective average pore size of the membrane was continuously decreased and the separation efficiency of the membrane was increased. These improvements were due to that the boehmite sol not only helped the dispersion of the α-Al₂O₃ powder in the membrane forming slurry, but also formed γ-Al₂O₃ in the gaps among the existed α-Al₂O₃ particles which was beneficial for membrane sintering and pore size decreasing. For the membrane prepared with 45 wt% boehmite sol, the effective average filtration pore diameter was 178 nm and the water permeance of the membrane reached 1691 Lm⁻²h⁻¹bar⁻¹, which was much better than the values reported before. Moreover, the reusability of the membrane was confirmed using a recycling test.     

Zirconia aerogels and xerogels: Influence of solvent and acid on structural properties

High-surface-area zirconia aerogels with meso- to macroporosity have been prepared by an acid-catalyzed alkoxide-sol-gel route with tetrabutoxyzirconium(IV) and subsequent high-temperature supercritical drying at 578 K. The effect of solvent (ethanol, propanol, butanol, t-amylalcohol), amount of nitric acid, calcination temperature, and drying method was studied by nitrogen physisorption, X-ray diffraction, Fourier transform Raman and diffuse reflectance infrared Fourier transform spectrosopy, scanning electron microscopy, thermal analysis, and temperature-programmed desorption of NH₃. After calcination in air at 573 or 773 K, the aerogels possess specific surface areas of up to 270 or 180 m² · g^–1, respectively. The use of ethanol as solvent resulted in the highest specific surface areas and pore volumes (up to 1.5 cm³ · g^–1) among all samples studied, whereas bulky t-amylalcohol caused a shift of the maxima of the broad pore size distributions from 30 to 70 nm. With the corresponding xerogels, prepared via the same wet-chemical procedure but evaporatively dried at ambient temperature, butanol resulted in a maximum at 3 nm and t-amylalcohol in a bimodal pore size distribution with maxima at 3 and 15 nm. The variation of the acid-to-alkoxide ratio in the range 0.08–0.12 at a hydrolysis level of 4 did not significantly influence the structural properties of aerogels and related xerogels. In contrast to the aerogels, the xerogels had significantly lower specific surface areas and prominent microporosity. All uncalcined aerogels contained crystalline ZrO₂, whereas the corresponding uncalcined xerogels were X-ray amorphous and crystallized only during calcination at 573 K. Both aerogels and xerogels possessed Brønsted-type and Lewis-type acid sites. With the xerogels, the density of acid sites on the surface was significantly lower. This behaviour is attributed to the higher amounts of organic residues which persisted in and on the xerogels up to 773 K and thus blocked the acid sites partially.