Thermal Degradation of Acetate-Intercalated Hydroxy Double and Layered Hydroxy Salts

Abstract

Synopsis:The gas-phase products from thermal degradation of zinccontaining layered metal hydroxides with intercalated acetate anions depend on the identity of metals in the hydroxide layers. Zinc hydroxy acetate and zinc/nickel hydroxy acetate precursors promote ketonization to produce acetone while this channel is suppressed in zinc copper hydroxy acetate. Growth of ZnO crystallites is also precursor dependent.NOT THE PUBLISHED VERSION; this is the author's final, peer-reviewed manuscript. The published version may be accessed by following the link in the citation at the bottom of the page.Inorganic Chemistry, Vol 45, No. 9 (April 2006): pg. 3766-3773. DOI. This article is © American Chemical Society and permission has been granted for this version to appear in e-Publications@Marquette. American Chemical Society does not grant permission for this article to be further copied/distributed or hosted elsewhere without the express permission from American Chemical Society. 2 AbstractTwo hydroxy double salts (HDSs), zinc copper hydroxy acetate (ZCA) and zinc nickel hydroxy acetate (ZNA), and an analogous layered compound, zinc hydroxy acetate (ZHA), have been prepared by a coprecipitation method. The thermal degradation of these materials was characterized via thermogravimetric analysis (TGA), differential thermal analysis (DTA), and TGA coupled with Fourier transform infrared spectroscopy of gas-phase products, TGA-FTIR. Loss of physisorbed and interlayer H2O was observed between 50 and 150 °C for all compounds. Acetic acid, acetone, water, and CO2 were released at high temperatures with relative acetone yields found to be dependent on precursor identity, with very little formed from ZCA compared with ZHA and ZNA. Combined FTIR and XRD analysis of solid residues extracted at different points in the heating profile suggests that ketonization occurs via dissociative adsorption of acetic acid on ZnO surfaces. Nanometer-sized ZnO particles were formed from ZHA, showing slight preferential growth in the ZnO (002) lattice direction, while the presence of a second metal, Ni or Cu, served to retard ZnO crystallite growth at temperatures below 600 °C and eliminate preferential growth. ZCA leads to the formation of reduced copper species (metallic copper and Cu2O) when heated to 250 °C.

Simple route for the synthesis of copper hydroxy salts

“…The second event with weight loss of 23%, occurring in the 150 ºC to 400 ºC interval, can be assigned to the thermal decomposition and destruction of the layered structure through dehydroxylation reactions and transformation of nitrate ions (present in the interlayer space) to nitrogen oxides, as reported in the literature for hydroxy salt materials. 5,[29][30][31] The most commonly accepted mechanism for the thermal decomposition of copper hydroxynitrate is described by equation 2, which does not include the decomposition of nitric acid. …”

A critical assessment of the methods for intercalating anionic surfactants in layered double hydroxides

“…Generally, the first step is due to the loss of interlayer water and is assumed to be complete at a temperature of 150 °C (Carlino & Hudson, 1995;Frost et al, 2003;Kandare & Hossenlopp, 2006; For the other LDH precursors prepared, the LDH nitrate and chloride showed two-step weight loss (see Figure 4.2 and Appendix II). This thermal profile is in agreement with those of and Bera et al (2000), who assigned the low-temperature (25-220 °C) mass loss to water being adsorbed or intercalated, and the loss at higher temperatures (225-450 °C) to decomposition or deanation.…”

Polytypic transformations during the thermal decomposition of cobalt hydroxide and cobalt hydroxynitrate

“…Metal hydroxide and hydroxysalts have been used in various applications such as catalysis, supercapacitors, rechargeable batteries, magnetic materials, ceramics, ion exchangers and organicinorganic nanohybrids [2][3][4][5]. The bivalent metal hydroxides and hydroxysalts derive their structure from mineral brucite-Mg(OH) 2 [6][7][8]. The crystal structure of bivalent metal hydroxide consists of a hexagonal close packing of hydroxyl ions, in which alternative layers of octahedral sites are occupied by the divalent metal ions.…”