Coordination Polymers and Polymer Nanofibers for Effective Adsorptive Desulfurization

Abstract

Desulfurization of fuel oils is an essential process employed in petroleum refineries to reduce the sulfur content to levels mandated for environmental protection. Hydrodesulfurization (HDS), which is currently being employed, is limited in treating refractory organosulfur compounds and only reduces the sulfur content in fuels to a range of 200-500 ppmS. In this chapter, several scientific and technological advances reported in the literature for the desulfurization of fuels are reviewed and discussed. Amongst these techniques, oxidative desulfurization (ODS) and adsorptive desulfurization (ADS) are proposed as additional steps to complement HDS in meeting the mandated ultra-low sulfur levels (10 ppmS). In the ODS technique, refractory organosulfur compounds are oxidized to organosulfones, followed by solvent extraction or adsorption of the organosulfones. The chemistry involved in the development and fabrication of sulfur/sulfone responsive adsorbents is also discussed. The use of molecular imprinted polymers (MIPs) and coordination polymers (CPs) for the selective adsorption of organosulfone compounds (in ODS) and/or organosulfur (in ADS) offers various properties such as imprinting effect, hydrogen bonding, π-π interactions, van der Waals forces, π-complexation, and electrostatic interactions. CPs, in particular metal organic frameworks (MOFs), have been reported to possess suitable features to overcome most of these challenges associated with adsorptive ultra-deep desulfurization when design strategies to achieve good selectivity are strictly followed. Matching the sizes of the cavities to the critical dimensions of the sulfur containing compounds (SCCs), using suitable metal centres which allow for coordinative interaction with the SCCs and using linkers with suitable functionality as to enhance specific interaction (dispersion forces) with the SCCs were considered to be pivotal features to prioritize. The prospects for the use of MIPs and CPs for future industrial applications in desulfurization are envisaged.

Perspectives on strategies for improving ultra-deep desulfurization of liquid fuels through hydrotreatment: Catalyst improvement and feedstock pre-treatment

“…Choice of solvent for the extraction of nitrogen-containing compounds from fuel oils is critical, it must be thermodynamically compatible with the compounds (Dembaremba et al, 2020). Polar solvents with low boiling points such as ethanol, ethanol and acetonitrile have been tested for denitrogenation of fuel oil but these solvents are too volatile for practical application on an industrial scale (Campos-Martin et al, 2010;Mokhtar et al, 2014).…”

Effect of Adding Chelating Ligands on the Catalytic Performance of Rh-Promoted MoS2 in the Hydrodesulfurization of Dibenzothiophene

“…Deleterious refractory organosulfur compounds in fuel oils have contributed to SOx emissions [1,2]. Therefore, it has become very important to remove these compounds due to the introduction of the strict environmental regulations of the Euro V limits of 10 ppmS in diesel fuels [1,2].…”

“…However, other methods of fuel desulfurization have been reported, and these techniques are bio-desulfurization (BDS), oxidative-desulfurization (ODS), adsorptive and extractive desulfurization (ADS and EDS) [1,2]. Bio-desulfurization (BDS), which involves the use of sulfur-consuming bacteria to desulfurize fuels, is nonetheless limited in meeting very deep desulfurization, as 50-200 ppmS have been reported [1]. The ODS process of recalcitrant sulfur-containing compounds such as dibenzothiophene have been reported to produce nonessential side products during oxidation [2].…”

“…Adsorptive and extractive desulfurization (ADS and EDS) is a process which employs the use of use of solid sorbents and extraction solvents for removing the recalcitrant sulfur-containing compounds, respectively. Adsorbents have been limited in organosulfur compound selectivity, as well as low adsorption capacity, while the organosulfur extraction solvents such as dimethylsulfoxide (DMSO) and N,N-dimethylformamide (DMF) have high boiling points, and hence the solvent recovery may be impossible [1,2]. The use of ODS, BDS, ADS and EDS desulfurization techniques are currently limited, as they may pose problems for larger scale applications [1,2].…”

“…Adsorbents have been limited in organosulfur compound selectivity, as well as low adsorption capacity, while the organosulfur extraction solvents such as dimethylsulfoxide (DMSO) and N,N-dimethylformamide (DMF) have high boiling points, and hence the solvent recovery may be impossible [1,2]. The use of ODS, BDS, ADS and EDS desulfurization techniques are currently limited, as they may pose problems for larger scale applications [1,2]. As a result, more attention is required to improve the HDS system by redesigning the current HDS catalysts' inadequacies and by introducing chelating ligands and precious metals (PGMs), which could drive HDS under mild conditions .…”