Combined Molten Salt Research Articles

A combined leaching and electrochemical activation approach to converting coal to capacitive carbon in molten carbonates

The impurities of coal plague its values not only for fuels but also for preparing functional carbon materials. Herein, we aim to develop a clean and one-step strategy to prepare activated carbon by molten salt leaching and electrolysis approach to converting anthracite/lignite to carbon for electrochemical supercapacitors. First, the major impurities such as silica and alumina were removed by a combined molten salt and water leaching process without using any toxic acid or alkaline solutions. Meanwhile, the carbonization and activation of coals take place together in the water- and oxygen-free molten salt medium. Moreover, the electrolysis can further increase the specific capacitance of the coal-derived carbon by the electrochemical regulation of carbon in molten salt using a low-cost and oxygen-evolution inert anode. The as-obtained carbon delivers a capacitance of 190 F g−1 at 5 A g−1 and shows nearly no capacitance loss after 10,000 cycles. This paper provides a clean molten salt approach to utilizing both high-rank and low-rank coals for the preparation of capacitive carbons.

Preparation of CaZrO<sub>3</sub> powders by a microwave–assisted molten salt method

CaZrO3 powders were synthesized by a combined molten salt and microwave heating technique, i.e., microwave–assisted molten salt synthesis (MMSS) technique, using ZrO2 and CaCl2 as the main raw materials, and molten LiCl and Na2CO3 as a reaction medium. Phase pure CaZrO3 powders can be synthesized at 900°C for 3 h by using the MMSS method. This synthesis temperature was at least 100°C lower than that required by the conventional molten salt synthesis method. Microstructures and phase compositions of as-prepared CaZrO3 powders were examined by field emission–scanning electron microscopy (FE–SEM) and transmission electron microscope (TEM), revealing that the crystalline size of the as-prepared CaZrO3 powders was about 100–300 nm, and the “template formation” mechanism played a dominant role in the synthesis process of MMSS.

Combined molten salt–Ni/Al2O3 as synergistic medium for high-quality syngas production

Proposed synergistic use of a combined medium of molten salt and Ni/Al2O3 (MS-Ni) was investigated for its enhancement of cellulose pyrolysis for high-quality syngas production. Clean renewable solar energy is to be stored at a high temperature in molten salt (MS) and provides the heat of pyrolysis. The MS-Ni medium could increase H2 yield by 3-folds while CO yield slightly increased by 15%, compared to the case of only MS medium. The peak rate of H2 production nearly quadrupled while the peak rate of CO production increased 2.5times at about 150 and 80K lower temperatures, respectively. The ratio of selectivity of syngas to undesired CH4 was nearly doubled. Arrhenius rate expressions for pseudo-first-order pyrolytic reaction are derived from the experimental data to give activation energies of 206 and 128kJmol−1 for the MS and the MS-Ni mediums, respectively. The experimental results clearly validated the role of MS-Ni as a synergistic medium for high-quality syngas production from cellulosic biomass pyrolysis.