Ruthenium-Loaded Halloysite Nanotubes as Mesocatalysts for Fischer–Tropsch Synthesis

Abstract

Halloysite aluminosilicate nanotubes loaded with ruthenium particles were used as reactors for Fischer–Tropsch synthesis. To load ruthenium inside clay, selective modification of the external surface with ethylenediaminetetraacetic acid, urea, or acetone azine was performed. Reduction of materials in a flow of hydrogen at 400 °C resulted in catalysts loaded with 2 wt.% of 3.5 nm Ru particles, densely packed inside the tubes. Catalysts were characterized by N2-adsorption, temperature-programmed desorption of ammonia, transmission electron microscopy, X-ray fluorescence, and X-ray diffraction analysis. We concluded that the total acidity and specific morphology of reactors were the major factors influencing activity and selectivity toward CH4, C2–4, and C5+ hydrocarbons in the Fischer–Tropsch process. Use of ethylenediaminetetraacetic acid for ruthenium binding gave a methanation catalyst with ca. 50% selectivity to methane and C2–4. Urea-modified halloysite resulted in the Ru-nanoreactors with high selectivity to valuable C5+ hydrocarbons containing few olefins and a high number of heavy fractions (α = 0.87). Modification with acetone azine gave the slightly higher CO conversion rate close to 19% and highest selectivity in C5+ products. Using a halloysite tube with a 10–20-nm lumen decreased the diffusion limitation and helped to produce high-molecular-weight hydrocarbons. The extremely small C2–C4 fraction obtained from the urea- and azine-modified sample was not reachable for non-templated Ru-nanoparticles. Dense packing of Ru nanoparticles increased the contact time of olefins and their reabsorption, producing higher amounts of C5+ hydrocarbons. Loading of Ru inside the nanoclay increased the particle stability and prevented their aggregation under reaction conditions.

Sepiolite-Hydrogels: Synthesis by Ultrasound Irradiation and Their Use for the Preparation of Functional Clay-Based Nanoarchitectured Materials

“…S BET (m 2 g −1 ) S EXT (m 2 g −1 ) V micro (cm 3 g −1 ) V meso (cm 3 g −1 ) 2019b; Lo Dico et al, 2019;Lisuzzo et al, 2020a;Farinmade et al, 2020;Saleh et al, 2020;Stavitskaya et al, 2020). Moreover, this clay does not show toxic effects and it is biocompatible (Fakhrullin and Lvov, 2016;Rozhina et al, 2020;Rozhina et al, 2021).…”

Nanotubular Polyaniline/Reduced Graphene Oxide Composite Synthesized from a Natural Halloysite Template for Application as a High Performance Supercapacitor Electrode

“…[22] Compared with CNTs, the HNTs is cheaper, has more abundant reserves, is non-toxic and has good compatibility. In view of the above structural characteristics and lower economic costs, the HNTs have been widely used as composite fillers, [23][24] catalyst carriers, [25][26] environmentally friendly adsorbents, [27][28] micro-reactors, [29] and templates for synthesizing functional materials. [30][31][32] Studies have shown that aniline, pyridine, thiophene, etc.…”

Natural aluminosilicate nanotubes loaded with RuCo as nanoreactors for Fischer-Tropsch synthesis

“…The outer surface of nanotubes consists of silica, while the inner surface is made of alumina [ 21 ]. Tubular structure with possibilities for modification combined with thermal and mechanical stability, low acidity of halloysite make it an interesting support for FTS catalysts [ 22 , 23 ]. As the most active catalysts are those with 8–9 nm Co nanoparticles [ 24 , 25 ], the mesoporous lumen of halloysite is a perfect place for Co nanoparticles with the favourable size.…”