Biodiesel surrogate and ethane evaluation for green carbon black and turquoise hydrogen synthesis via thermal plasma

Abstract

The impact of feedstock variation on conversion, yield (hydrogen and solid carbon), carbon black size, structure and morphology is examined by means of a thermal plasma reactor. In particular, two feedstock alternatives (ethane and methyl oleate – a biodiesel surrogate) are investigated for their aforementioned impacts relative to a common primary feedstock, methane (a natural gas surrogate). In both studies, high feedstock conversion rates (>99%), and yields (>97%) were observed. The results also indicate carbon black particles potentially suitable for tires, treads and industrial rubber applications that require high durability elastomer components due to their high reinforcing properties. Despite molecular variations in feedstock degree of bond saturation, hydrocarbon chain length, and functional group content, only minor differences in particle quality were observed. TEM of carbon produced from the feedstock alternatives indicates similar features to that produced with a methane feedstock. Carbon dating analysis shows that for a 50–50 methane – methyl oleate feedstock composition (carbon molar loading basis), 82% of the initial bio-based carbon was recovered in the carbon black product, demonstrating that bio-based carbon can be primarily converted into chemically inert solid carbon, and thus essentially sequestered. Finally, a life cycle assessment is performed using the GREET model for all feedstocks in a thermal plasma pyrolysis reactor. The results indicate that the carbon intensity of hydrogen production is 0.91 kg of CO2e per kg of product with a natural gas feedstock and 0.85 kg of CO2e per kg of product with a 50% methane and 50% methyl oleate feedstock (biodiesel surrogate) without biogenic CO2 credits, much lower when accounting for biogenic CO2 credits. The use of natural gas alternatives in a thermal plasma reactor provides numerous benefits including supply chain flexibility, reduced process energy intensity, and reduced process carbon intensity while maintaining equivalent hydrogen and carbon black quality and yield.