Extraction Coupled Oxidative Desulfurization of Fuels to Sulfate and Water-Soluble Sulfur Compounds Using Polyoxometalate Catalysts and Molecular Oxygen

Abstract

Our contribution demonstrates a new way of fuel desulfurization, namely selective oxidation of organic S-compounds present in fuels to water-soluble sulfur compounds followed by in situ extraction of the latter into an aqueous phase. Different from common oxidative desulfurization (ODS) processes, we demonstrate a technique that converts sulfur compounds in fuel to a large extent to sulfate (60–70%) using oxygen as the oxidant and an aqueous H8PV5Mo7O40 (HPA-5) solution as the catalyst phase. Other water-soluble desulfurization products are sulfoacetic acid (SAA) with a share of 10–20%, 2-sulfobenzoic acid (2-SBA), and 2-(sulfooxy)­benzoic acid (2-SOBA), the latter two with a share of <10%. The new desulfurization method has been optimized for removing benzothiophene from isooctane, giving the best results with a degree of desulfurization of 99% applying 120 °C, 20 bar oxygen pressure, and 1000 rpm of 6 h reaction time using a volume water/oil ration of 10/1. Furthermore, we also successfully demonstrated the desulfurization of a domestic fuel oil with 973 ppmw sulfur content with a degree of desulfurization of 28% under nonoptimized conditions.

Unique Thia‐Baeyer–Villiger‐Type Oxidation of Dibenzothiophene Sulfoxides Derivatives

“…Various pathways proposed for OBDS of dibenzothiophene (DBT) were reported, wherein typically including one step of C−S cleavage reaction that is just challenging the artificial or biomemic methodology potential. ODS at presence normally leads to DBT sulfoxide ( DBTO ) or DBT sulfone ( DBTO 2 ) that both of them keep C−S bonds A few reports involved C−S cleavage but had to performe under the harsh conditions or using strong oxidant like persulfate oxidant, therefore the products had neither selectivity nor biological activity. Since scission desulfurization of DBT and its derivatives ( DBTs ), abundant and refractory compounds in the fossil fuels, under the mild condition are extremely necessary for the atom‐economic desulfurization, to learn C−S bond cleavage from OBDS and understand the molecular aspect of this reaction is paramount.…”

Investigations on Catalyst Stability and Product Isolation in the Extractive Oxidative Desulfurization of Fuels Using Polyoxometalates and Molecular Oxygen

“…In this first study also a proof-of-concept for catalyst recycling was given, however, combined with a certain degree of catalyst deactivation. [16] Consequently, we were interested to study the catalyst deactivation behavior in the ECODS process in more detail. For this purpose, we conducted catalyst recycling experiments with a tenfold increase of the sulfur content compared to our abovementioned previous work.…”

“…However, a still open point in the ECODS concept is the effective separation and recycling of the catalyst. This aspect is particularly important as all polar products accumulate in the aqueous catalyst phase and some of the reaction intermediates lead to catalyst deactivation . From a general point of view the following approaches may be considered as feasible and worth investigating: (i) heterogenization of the Keggin‐POM by immobilization on a support material, or complexation with an organic or inorganic cation, combined with filtration of the heterogenized catalyst; (ii) separation of the catalyst from the oxidation products by distillation; (iii) separation of the catalyst from the oxidation products by extraction; or (iv) separation of the catalyst from the oxidation products by membrane separation processes …”

Porous MoO3@SiC hallow nanosphere composite as an efficient oxidative desulfurization catalyst

“…The sulfur compounds in the oil products are one of the most important pollutants that must be removed due to the generation of the toxic sulfur compounds during the combustion and subsequently air pollution and acid rain. [1][2][3] There are several ways to remove the sulfur compounds from crude oil and commercial fuels. HDS (Hydrodesulfurization) is the most popular desulfurization method that is widely used in the oil industries.…”