Effects of Temperature and Equivalence Ratio on Carbon Nanotubes and Hydrogen Production from Waste Plastic Gasification in Fluidized Bed

Abstract

The waste plastic gasification in a fluidized bed for a continuous carbon nanotube (CNT) and hydrogen coproduction is a potential method for sustainable management. Ni/Al 2 O 3 catalysts have been synthesized by the impregnation method to upgrade hydrogen production and CNT synthesis. However, few studies investigated the effect of operating parameters for upcycling waste plastics into CNTs and hydrogen in the fluidized-bed system. The reaction temperature and the equivalence ratio (ER) were evaluated for CNT and hydrogen coproduction. Increasing the reaction temperature and lowering the ER enhanced the methane dry reforming, hydrocarbon dry reforming, and hydrocarbon direct decomposition for hydrogen and CNT coproduction. While increasing the reaction temperature from 500 to 700 °C can obtain higher CNT yield and H 2 production rate, the system heated to 700 °C and maintained at this temperature should provide more energy. Moreover, the gas composition at 600 °C with 0.1 ER contained more CH 4 and C 2 −C 5 hydrocarbons compared with that with a higher ER, which could be used as the carbon source of CNTs. The reaction temperature of the fluidized bed in the waste plastic gasification system controlled at 600 °C with 0.1 ER and the gasified products upgraded through a catalytic fixed-bed reactor at 680 °C exhibited an optimal catalytic performance of less-defective CNTs in 22.0% yield and H 2 production rate (385.1 mmol/h-g catalyst).

Effect of Preparation Solvent and Calcination Atmosphere on Ni@SiO2 Catalyst for Simultaneous Production of Hydrogen and Carbon Nanotubes from Simulated Plastic Waste Syngas

“…The carbon yield was calculated according to the weight loss of CNTs between 400 C and 700 C from the TGA curve using the following equation Carbon yield ð%Þ ¼ ðWeight loss between 400 C and 700 CÞ% 100% À weight loss% Â 100% (7) Supporting Information…”

“…In contrast, the main weight loss of Ni@SiO 2 -E-H 2 and Ni@SiO 2 -I-H 2 occurred at 400-700 C, indicating the oxidation of CNTs, as shown in Figure 7b. In addition, CNT production was calculated using formula (7) and is listed in Table 2.…”

“…Different types of plastic waste, such as polyethylene (PE), polypropylene (PP), and polystyrene (PS), have been converted into H 2 and carbon materials. Ni‐based catalysts have been widely used in methane reforming reaction because of their high catalytic activity and stability for the decomposition of hydrocarbon.…”

“…Wu et al discussed different Ni loadings on a SiO 2 support applied to the ethanol steam reforming reaction for carbon production . Additional Ni on Mg—Al was beneficial for enhancing the H 2 production from PP, PS, and HDPE pyrolysis, and the effect of temperature and equivalence ratio for the CNT and H 2 coproduction by the Ni/Al 2 O 3 catalyst from PE and PP gasification was examined in the research of Yang et al However, several significant drawbacks of the gasification process are related to the high‐temperature reaction, which causes sintering of the metal catalysts. Then, exceeding the non‐ordered carbon deposition might result in catalyst deactivation .…”

“…[17,[24][25][26][27][28][29] The gasification of solid waste is a complex process, involving a series of physicochemical interactions and occurring at a temperature over 600 C. However, the precise temperature is based on the type of reactor and the properties of the waste. [7,30] The reactions among the hydrogen and carbon production pathways are as follows: (1) dry reforming of methane; (2) methane cracking; (3) the Boudouard reaction; (4) reduction of CO to carbon; and (5) the reverse WGSR. [31][32][33]…”