Preparation of mesoporous activated carbons from coal liquefaction residue for methane decomposition

Mesoporous activated carbons were prepared from direct coal liquefaction residue （CLR） by KOH activation method, and the experiments were carried out to investigate the effects of KOH/CLR ratio, solvent for mixing the CLR and KOH, and carbonization procedure on the resultant carbon texture and catalytic activity for catalytic methane decomposition （CMD）. The results showed that optimal KOH/CLR ratio of 2 ： 1; solvent with higher solubility to KOH or the CLR, and an appropriate carbonization procedure are conductive to improving the carbon pore structure and catalytic activity for CMD. The resultant mesoporous carbons show higher and more stable activity than microporous carbons. Additionally, the relationship between the carbon textural properties and the catalytic activity for CMD was also discussed.

Adsorption separation performance of H_2/CH_4 on ETS-4 by concentration pulse chromatography

To exploit an effective adsorbent to separate hydrogen and methane, microporous titanium silicate molecular sieve NaETS-4 was synthesized and modified by strontium. The adsorption characteristics and diffusion behaviors of the prepared titanosilicate molecular sieve were studied by concentration pulse chromatography. And the effects of ion-exchange and dehydration temperature on adsorbent structure and gas diffusion were also discussed. The results showed that the thermal stability and Henry＇s Law constants were enhanced and micropore diffusivity decreased after exchanging Na＋ with Sr2＋. With the increase of dehydration temperature, Henry＇s Law constant and micropore diffusivity of CI-I4 decreased in both NaETS-4 and SrETS-4. While for 1-12 in SrETS-4, the increase of Henry＇s Law constant and the decrease of diffusion rate can be attributed to the shrinks of pore diameter resulting from the relocation of Sr2＋. Correspondingly, the kinetic selectivity of H2/CH4 reached 8.91 indicating its potentiality in separating H2 and CH4.

Influence of plasma-induced reflected wave variations on microwave transmission characterization of supersonic plasma excited in shock tube

In this work,the theoretical analysis and experiment results investigating the influence of plasma-induced reflected wave variations on microwave transmission characterization are presented.Firstly,an analytical transmission line model for transmission characterization of plasma in shock tube is derived and validated against full-wave simulation.Then,the theoretical analysis of transmission characterization based on a time-dependent reconstruction algorithm that takes into account the variations of reflected wave is presented and the influence of reflection variations under various states of plasma is also investigated.The unusual increase in the amplitude of transmitted wave is theoretically predicted and experimentally demonstrated as well.Finally,the experiment results are also presented to illustrate the effects of reflected wave variations in practical microwave transmission characterization of supersonic plasma excited in shock tube.

Preparation of bimetallic catalysts Ni-Co and Ni-Fe supported on activated carbon for methane decomposition

Bimetallic catalysts(Ni-Co/AC and Ni-Fe/AC)supported on activated carbon(AC)were prepared via one-step method from coal as AC precursor with the addition of metal salts by KOH activation.The effects of the introduction of second metal(Co or Fe)into Ni/AC on the textural structure of the resultant bimetallic catalysts and their catalytic performances for methane decomposition were investigated.The results showed that active metals can be directly supported on AC by the reaction of metal species with carbon during the activation.The addition of Co or Fe to Ni/AC resulted in the decrease of specific surface area and pore volume.With increasing the loading of Co or Fe,metal alloys were formed and total surface area and pore volume declined,but the mesoporosity was increased.Bimetallic Ni-Co/AC and Ni-Fe/AC catalysts exhibited better catalytic activity and stability for methane decomposition compared than Ni/AC.The introduction of Co mainly improved initial catalytic activity;however,Ni-Fe/AC catalyst showed better behaviors in terms of reducing the deactivation rate of Ni-based catalyst than Ni-Co/AC catalyst,which is relative with the formation of Ni-Fe alloy and carbon fibers over Ni-Fe/AC.This work provides a simple and efficient approach to improve catalytic performances of Ni-based catalyst for methane decomposition.