Thermal Chemical Conversion of High-Density Polyethylene for the Production of Valuable Carbon Nanotubes Using Ni/AAO Membrane Catalyst

© 2017 American Chemical Society. Thermal chemical conversion of waste plastics for syngas production is a promising alternative method for the management of waste plastics. However, one of the challenges of facilitating the deployment of this technology is the low economic benefit of waste-plastic recycling. By producing a high-value carbon nanotubes (CNTs) byproduct, an interesting alternative solution is provided. To further enhance the quality of CNTs produced from catalytic thermal chemical conversion of waste plastics, a template-based catalyst (Ni/anodic aluminum oxide, AAO) is proposed in this work. In addition, reaction temperature, Ni content and water injection were studied for their influences on the formation of CNTs on Ni/AAO using a two-stage fixed bed reactor. Various analytical methods, e.g., scanning electronic microscopy (SEM) and X-ray diffraction (XRD), were used to evaluate the performance of catalyst in relation to the production of CNTs. The results show that a higher loading of Ni on AAO resulted in the formation of metal particles with various sizes, thus leading to the production of nonuniform CNTs. In addition, an optimal catalytic temperature of 700 °C is suggested for the production of CNTs. Because the catalyst might not be activated at 600 °C, which produced a low yield of CNTs. However, a reaction temperature of 800 °C resulted in a low yield of CNTs. Carbon deposition decreased with an increase of steam injection, but the quality of CNTs formation in relation to the uniform of CNTs seemed to be improved in the presence of steam

Direct and highly selective conversion of captured CO2 into methane through integrated carbon capture and utilization over dual functional materials

Excessive atmospheric CO2 emission is regarded as one of the main factors causing global climate change. Thus, there is an urgent need to explore the possibility of CO2 capture and converting the captured CO2 to fuels or value-added products. Recently, an integrated carbon capture and utilization (ICCU) process performed in a single reactor under isothermal conditions draws intensive attentions due to the reduction of energy requirement for sorbent regeneration. However, from literature, normally a low loading of sorbent in dual functional materials (DFMs) was applied resulting in a very low CO2 capture capacity and consequent low CH4 yield in the ICCU process. Herein, we demonstrate the intermediate-temperature DFMs using inexpensive high-capacity MgO sorbent. The synthesized DFMs are a physical mixture of sorbent and Ru/CeO2 catalyst by the mass ratio of 2:1 allowing simultaneous regeneration of sorbent and conversion of CO2 in a single reactor at 300 °C. During the 1st cycle of ICCU process, 10Ru/CeO2-MgO exhibits the best ICCU performance with the highest CH4 yield of 7.07 mmol g−1 and CO2 conversion of 89 %. However, after 10 cycles of ICCU process, 5Ru/CeO2-MgO exhibits the highest CH4 yield (3.36 mmol g−1) and CO2 conversion (79 %), which are much higher than that of 2.5Ru/CeO2-MgO (1.13 mmol g−1 and 39 %) and 10Ru/CeO2-MgO (2.31 mmol g−1 and 69 %). It is mainly attributed to that more oxygen vacancies are remained in 5Ru/CeO2-MgO resulted from the metal-support interaction

Development of Ca/KIT-6 adsorbents for high temperature CO2 capture

The incorporation of CaO into an inert porous solid support has been identified as an effective approach to improve the stability of adsorbents for CO2 capture. In this work, we focus on enhancing the capacity of carbon capture and cyclic stability of CaO by impregnating CaO particles into a three-dimensional mesoporous silica (KIT-6) support. At a low CaO loading, the three-dimensional mesoporous support was filled with CaO nano-particles. The further increase of CaO loading resulted in the aggregation of CaO particles on the external surface of the support material, as identified by electron microscopy analysis. These CaO/KIT-6 adsorbents show excellent high-temperature CO2 carbonation/calcination stability over multiple cycles of CaO carbonation and calcination. The enhancement of the performance of carbon capture is attributed to the interaction between CaO and the silica skeleton of KIT-6 through the formation of interfacial CaSiO3 and Ca2SiO4 which enhanced the resistance of CaO sintering

Integrated CO2 capture and methanation on Ru/CeO2-MgO combined materials: Morphology effect from CeO2 support

Integrated CO2 capture and methanation (ICCM) is attracting more attention to promote the reduction of CO2 emission. This work developed and applied a set of combined materials using Ru/CeO2 as catalyst and physically mixed Li, Na, K-doped MgO as adsorbent for the ICCM process. The influences of morphologies of CeO2 (rod, particle, and cube) in combined materials are investigated explicitly in terms of CO2 conversion and CH4 yield. Compared to the CeO2 with cube morphology, the CeO2 with rod and particle morphologies showed better Ru dispersion and more abundant support-metal interaction (SMI). The combined materials with rod and particle morphologies CeO2 (Ru/rod-CeO2-MgO and Ru/particle-CeO2-MgO) show more superior catalytic performance (0.33 and 0.29 mmol/g for CH4 yield and 55.7% and 59.8% for CO2 conversion, respectively) than that with Ru/cube-CeO2-MgO. Furthermore, the Ru/rod-CeO2-MgO shows excellent catalytic stability and reusability during 9 cyclic ICCM evaluations. In situ DRIFTS of Ru/CeO2-MgO revealed that the formates and dissociated CO2 (Ru-CO) might be the critical methanation intermediates in ICCM