Simultaneous production of hydrogen and carbon nanotubes from cracking of a waste cooking oil model compound over Ni‐Co / SBA ‐15 catalysts

Abstract

Hydrogen is considered an ideal energy carrier. However, the use of fossil fuels to produce hydrogen depletes natural resources and causes environmental problems. Therefore, there is an urgent need to find alternative raw materials and technologies for the production of hydrogen. Waste cooking oil (WCO) is a renewable energy source that has emerged as a potential raw material for hydrogen production. This study describes the production of hydrogen and carbon nanotubes (CNTs) by catalytic cracking of a WCO model compound (WCOMC) performed in a lab-scale fixed bed using Ni-Co/SBA-15 catalysts. The phase, structure and reduction properties of the catalyst were analysed by using different characterisation methods. The effects of the nickel-cobalt metal content and the reaction temperature on both the hydrogen production and the quality of the CNTs were investigated. The deposited carbonaceous products were characterised to analyse their external appearance, internal structure, oxidation stability and graphitisation degree. The results indicated that the catalyst containing 20% Ni and 30% Co showed the highest activity. When reaction temperature was 800 C, the instantaneous volume fraction of hydrogen was close to 43.5 vol% and the content of hydrogen in the gas product was close to 66.5 vol%. A few multi-walled CNTs having a small diameter and some CNTs with an open-topped structure were deposited on 10%Ni-40%Co/SBA-15 and 30%Ni-20%Co/SBA-15, respectively. Thermogravimetric analysis and Raman spectroscopic analysis indicated that all CNTs showed high oxidation stability and a high degree of graphitisation.

Carbon Deposit Analysis in Catalyst Deactivation, Regeneration, and Rejuvenation

“…Williams, for instance, reviews the formation of hydrogen and carbon nanotubes from plastic waste, [219] and Liu and Yuan describe the same products from cracking model compounds representing waste cooking oil. [220] The carburisation of biomass and plastics, but also of hydrocarbons, such as methane, may be an interesting option to prepare so-called "turquoise" hydrogen without producing CO 2 . Ma et al describe the structural effects of regeneration of coked catalysts used for lignin pyrolysis using NMR and electron microscopy, [221] but do not analyse the coke species themselves.…”

“…The analysis of carbon species during the conversion of biomass and plastics, illustrated in Figure 16, seems to focus more on the products formed than on catalyst deactivation. Williams, for instance, reviews the formation of hydrogen and carbon nanotubes from plastic waste, [219] and Liu and Yuan describe the same products from cracking model compounds representing waste cooking oil [220] . The carburisation of biomass and plastics, but also of hydrocarbons, such as methane, may be an interesting option to prepare so‐called “turquoise” hydrogen without producing CO 2 .…”

Combustion, Pyrolysis, and Gasification of Waste-Derived Fuel Slurries, Low-Grade Liquids, and High-Moisture Waste: Review

“…The content of hydrogen and carbon monoxide increased with shorter residence times, while the content of methane and ethane in the gas phase decreased [67]. Liu and Yuan [101] studied the catalytic pyrolysis of waste cooking oil. They found that the yield of hydrogen decreased from 42 to 31 vol% when residence time was 4 h, which indicated a decrease in catalyst activity over time.…”

“…Catalytic pyrolysis of waste cooking oil was investigated by Liu et al [101]. The effect of nickel-cobalt catalyst and reaction temperature on hydrogen production was studied.…”

Nitrogen Adsorption and Characteristics of Iron, Cobalt, and Nickel Oxides Impregnated on SBA-15 Mesoporous Silica

“…Fe, Co, and Ni are commonly selected as catalysts to enhance the different carbon sources for the formation of carbon nanomaterials [ 8 , 31 , 32 ]. In addition, nickel- and cobalt oxides-impregnated SBA-15 materials presented resistance to coke formation, with high activity and selectivity, and were applied to organic solvents (cyclohexane, n-hexane, propane, and CO) [ 33 ] and biomass-derived fuels (such as liquid hydrocarbons and diesel-range hydrocarbons) [ 34 , 35 ], the growth of carbon nanofibers [ 36 ], bio-oil to produce hydrogen and carbon nanotubes [ 37 ], and n-hexane, propane and CO oxidation [ 38 ]. Some literature indicated higher performance in converting methyl esters to produce green diesel (C11-C20 hydrocarbons) [ 39 ].…”