Low-energy synthesis of kaliophilite catalyst from circulating fluidized bed fly ash for biodiesel production

Kinetics and Mechanism of Lithium Extraction from α-Spodumene in Potassium Hydroxide Solution

“…In this study, a low-temperature method of lithium extraction from α-spodumene in a KOH solution was proposed, and the leaching kinetics of Li during the reaction process was investigated. The study showed that the structure of α-spodumene could be destroyed directly by reacting with a 50 wt % KOH solution at a low temperature to produce the solid-phases Li 2 SiO 3 and KAlSiO 4 , while Li in Li 2 SiO 3 could be easily leached by acid leaching to obtain a lithium-containing leaching solution (Table S1, Supporting Information), and the main phase in acid residues was KAlSiO 4 (Figures S2 and S3, Supporting Information), which could be used as a heterogeneous catalyst and prepared for potassium-rich zeolites. , This process could avoid the challenge of separating lithium from a solution with relatively high potassium content and high-temperature calcination. The lithium extraction efficiency reached 89.9%, of which 84.1% was converted into solid phase Li 2 SiO 3 and 5.8% converted into the liquid phase under the following optimal process conditions: initial KOH concentration of 50 wt %, stirring speed of 500 rpm, mass ratio of KOH/ore of 2:1, leaching temperature of 523.15 K, and leaching time of 16 h. Compared with the NaOH method producing Li 2 SiO 3 , this paper showed the advantages in saving reaction time and reducing leaching pressure, which is also of great research value. The experimental data fitted well with the Avrami–Erofeev equation model, – ln­(1 – X ) = ( Kt ) n . The apparent activation energy and Avrami index were calculated as 106.37 kJ·mol –1 and 0.80, respectively.…”

Synthesis of KAlSiO4 by Hydrothermal Processing on Biotite Syenite and Dissolution Reaction Kinetics

“…The synthesis of two types of KAlSiO 4 was simpler and just involved one step, which fits with the green chemical production. Moreover, kalsilte also can be used as a heterogeneous catalyst for biodiesel production [41,42] and as an ingredient in dental ceramic materials [43,44]. In a general sense, the dissolution reaction behavior of some minerals such as montmorillonite [45] and diaspore [46] in alkaline solution was described by the rate law reported by Lasaga et al [47]:…”

Solid Green Biodiesel Catalysts Derived from Coal Fly Ash

“…In Table 5 are shown different catalysts and their catalytic performance for biodiesel production from various feedstock. Xiang et al [122] investigated alkali activated CFA modified by sodium sulfate under hydrothermal conditions, whereby transesterification reaction was carried out under microwave [23] and ultrasound [122] conditions. The high catalytic activity was achieved for short reaction time and it was shown that catalyst could be used even eight times without any loss of catalytic activity.…”