The Research On The Preparation And Activity Of Ru-based Confined In Carbon Nanotubes Catalyst In Supercritical Water

With the progress of human society and the development of social civilization, the demand for new materials and renewable energy is becoming higher. The exploitation and utilization of new materials and energy can greatly promote the development of the world economy and the progress of human society. Therefore, the research and development of new materials and renewable energy has always been one of the important and concerned issue of research scholars. In this work, based on the previous research of nanomaterial carbon nanotubes’preparation and application, Ru nanoparticles was confined in Multi-walled carbon nanotubes (MWCNTs) in supercritical water with carbon nanotubes as the carrier. The heterogeneous Ru/MWCNTs catalysts was used to catalyze phenol gasification in supercritical water for detection of catalytic activity. The main results and conclusions are as follows:(1) Ru nanoparticles was confined in Multi-walled carbon nanotubes in sub/supercritical water. In this work, Ru/MWCNTs were prepared successfully by two-step supercritical hydrothermal synthesis method. But the wet impregnation, microwave polyol synthesis method and the sol-gel method only support the load on the surface of carbon nanotube. In comparison, the load metal ruthenium in the multi-walled carbon nanotubes (Ru/MWCNTs) catalyst has a wider application in catalytic activity and selectivity. In this paper, six kinds of carbon nanotubes to be used, the 4 wt%,2 wt%, 1wt% Ru nanoparticles were successfully confined in Multi-walled carbon nanotubes (MWCNTs).(2) The activity of the Ru/MWCNTs catalyst be detected:the catalytic gasification of phenol in supercritical water. In the article, the Ru/MWCNTs catalyst has been characterized with HR-TEM and XPS. HR-TEM results showed that the Ru nanoparticles could successfully dispersed into the inner pores of MWCNTs. Homogeneous distribution and Ru nanoparticles confined in MWCNTs can be observed when 60-100 nm,>5μm MWCNT were used. Gasification efficiency has almost reached the similar conversion rate by 1 wt% Ru/60-100 nm,>5μm MWCNT compared with commercial catalyst (Ru/C, containing 5wt% Ru). Over 70% carbon conversion and 100% gas yield can be achieved, representing nearly 10-fold enhancement of gasification efficiency compared to the noncatalytic case. It is interesting to note that ruthenium confined in MWCNTs will change the selectivity to gaseous products. The products C2H6 and H2 were dramatically increased. By two-step supercritical hydrothermal synthesis method, Ru nanoparticles can be confined efficiently in MWCNTs and present high activity and different selectivity for gasification of phenol.(3)The molecular simulation is used to understand the process of nanoparticles confined in Multi-walled carbon nanotubes in supercritical water with Materials Studio computer software. 300 water molecules,6 RuCl3 molecules and 300 water molecules are built in this study. The energy of 300 water molecules,6 RuCl3 molecules and 300 water molecules increases with the rising simulation temperature. And the energy of 6 RuCl3 molecules and 300 water molecules is higher than the energy of 300 water molecules. This indicates that with the temperature rising, the density of supercritical water and the intermolecular force decrease, but the intermolecular distance increases, leading that the number of hydrogen bonds decreases and the solute diffusion resistance becomes weaker. We can conclude that RuCl3 molecules are more easily diffused in the water and uniformly distributed at low temperatures. But when the temperature rose to 380℃ in supercritical conditions, the RuCl3 molecules distance increases, leading that ruthenium chloride solution is insoluble in aqueous solution, the ruthenium ions in the gap and ports of the MWCNT will enter the interior of carbon nanotubes.