Research on the effects of hydrothermal synthesis conditions on the crystal habit of MIL-121

Abstract

The investigation of the influence of hydrothermal synthesis conditions such as synthetic temperature, the amount of solvent, addition of additives including sodium hydroxide, lithium chloride and 2-methylimidazole on the morphology and size of MIL-121 was carried out. The experimental results indicated the significant impact of hydrothermal synthesis conditions on the morphologies and sizes of MIL-121 crystals. The synthesis temperature has little effect on the morphology, which is mainly reflected in the change of the aspect ratio, but the effect on the size is significant under low-temperature conditions. Additives have an important influence on the morphology and size of MIL-121. Our study provides a potential for the improvement of MIL-121 adsorption performance.

The Influence of Hydrothermal Temperature on Alumina Hydrate and Ammonioalunite Synthesis by Reaction Crystallization

“…The results showed that a hydrothermal reaction condition of over 177 • C was required to obtain NH 4 Al 3 (SO 4 ) 2 (OH) 6 . Reaction (12) was similar to reaction (13), while the only different reactant was OH − in reaction ( 12) when compared with H 2 O in reaction (13). Therefore, the values of ∆G T 0 are close together and similar.…”

“…The following products may be produced during reaction crystallization: boehmite, diaspore, gibbsite, and bayerite. However, it is noted that alumina hydrate cannot be formed at a high temperature as reaction (12) may occur and ammonioalunite (NH 4 Al 3 (SO 4 ) 2 (OH) 6 ) is obtained when NH 4 + , Al 3+ , and SO 4 2− exist simultaneously in the solution [19,20]. However, ammonioalunite is not a common compound.…”

“…Yang et al [19] found that ammonioalunite can be obtained, via the hydrothermal synthesis method, in an ammonium aluminum sulfate solution without other raw materials at temperatures of over 180 • C. Additionally, the morphology of ammonioalunite is constituted by irregular particles. If reaction (12) happens in a reaction crystallization system between NH 4 Al(SO 4 ) •12H 2 O and NH 3 •H 2 O, it will be the first time that ammonioalunite has been synthesized in the alkaline initial environment.…”

“…As it is an important chemical synthesis method, reaction crystallization has been used widely in industrial fields. Moreover, hydrothermal reaction crystallization is a method through which crystallization takes place in hydrothermal reactors, and it allows one to obtain supersaturation via a coordination reaction [12]. Huang et al [13] found that hierarchically boehmite and urchin-like hollow alumina microspheres with interconnected needle-like building blocks can be synthesized using hydrothermal methods.…”

Anomalous Temperature-Induced Particle Size Reduction in Manganese Oxide Nanoparticles

“…One-dimensional Mn 3 O 4 nanorods were obtained by high-temperature calcination of MnOOH . Recently, several works on low-temperature-assisted methods ,, have been reported, such as the irregular block shape of Mn 3 O 4 by the hydrothermal method at 180 °C and monodispersed Mn 3 O 4 tetragonals with highly regular walls using a simple mild solution route at 60 °C …”