Trimetallic Sulfide Catalysts for Hydrodesulfurization

The more stringent environmental regulations enacted throughout the world have increased the need of more active hydrotreating (HDT) catalysts, in the petroleum refining industry. Usually, the catalysts used for diesel oil hydrotreatment are ?-Al2O3 supported molybdenum or tungsten sulfides promoted with cobalt or nickel. Current strategies for the design of novel HDS catalysts often include variations in the support formulation, catalyst preparation method and active phase formulation. In this sense, the new generations of catalysts, such as NEBULA®, are based on a totally different concept of bulk-like. In this chapter, we present recent research related to the synthesis, characterization and performance of trimetallic sulfide nanocatalysts for hydrodesulfurization. The present chapter analyses the state of art of the ternary sulfide hydrotreating catalysts.

Advances in Nanotechnology Transition Metal Catalysts in Oxidative Desulfurization (ODS) Processes

Organosulfur compounds show a negative environmental impact because of SOx emissions by combustion of fuel oils. As a consequence, removal of sulfur is becoming a worldwide challenge. The hydrodesulfurization (HDS) process achieves limited performances in the case of refractory S-containing aromatic compounds, such as thiophene and substituted benzothiophenes (BTs), which require highly energy-demanding conditions (high temperature and pressure conditions). Oxidative desulfurization (ODS) is considered the most promising alternative to HDS. During ODS treatment, the organosulfur compounds are oxidized to corresponding sulfoxides and sulfones, which can be successively removed by extraction with polar solvents. Different stoichiometric oxidants have been used in the ODS processes with a different degree of efficacy and environmental impact. The design and development of catalytic procedures can increase the ODS energy efficiency as well as make it more economical and environmentally acceptable. Here we describe the advances in nanostructured organometallic catalysis and biotechology applied to ODS treatment.

Polyoxometalates-Based Nanocatalysts for Production of Sulfur-Free Diesel

In the last decade, polyoxometalates have been demonstrated to be efficient catalysts for the activation of oxidants in desulfurization processes. Successful results on desulfurization using polyoxometalates and hydrogen peroxide to desulfurize model oils and liquid fuels were reported and can be found in the literature. The desulfurization is an actual subject with notable interest for refineries and fuel cost, and consequently it is important to focus the scientific community to work in desulfurization technology in order to develop catalytic systems based on polyoxometalates capable to be reused, stable, efficient and selective. Therefore, the main goal is the design of heterogeneous polyoxometalate based catalysts. This chapter pretends to inform the research society about the scientific directions that have been taken using heterogeneous polyoxometalate catalysts in oxidative desulfurization of simulated and real liquid fuels. In addition, future perspectives are proposed to cover the actual needs of this area.

Nanotechnology Applied to the Biodesulfurization of Fossil Fuels and Spent Caustic Streams

The use of nanostructured materials in combination with desulfurizing microorganisms is a promising technique that would improve the desulfurization processes of gaseous fuels, oil, and some wastewater. Nanoparticles are highly versatile and tunable depending on the necessities of each particular contaminated media. The chapter shows the current technological options for the biodesulfurization of natural gas, oil and wastewater produced from the petroleum refining, where the application of nano-sized materials combined with desulfurizing microorganisms would improve the desulfurization capacities. In addition, advantages, disadvantages and opportunities of this hybrid technology are presented.

Ni/ZnO Nano Sorbent for Reactive Adsorption Desulfurization of Refinery Oil Streams

The aim of this chapter is to present the Ni/ZnO nano-sorbent for reactive adsorption desulfurization (RADS) of refinery oil steams. The preparation and modification of nano-sorbent are reviewed. Various characterizations involving in the relation of properties with components, structures and dynamic phase change during RADS, are extensively provided. The mechanisms of desulfurization, sulfur transfer and sulfur adsorption are proposed. The contradictories in literature about active structures and reaction mechanism are discussed and the solutions are suggested. This chapter unfolds the impressive application of RADS of Ni/ZnO nano-sorbent to produce a cleaner gasoline. It also delves into the inadequately engineer areas which require further attention so as to make the RADS process more economic and more efficient. The perspective applications other than gasoline desulfurization are also presented.

Sulfur and Nitrogen Chemical Speciation in Crude Oils and Related Carbonaceous Materials

This chapter gives an overview of sulfur x-ray absorption near edge spectroscopy (XANES) studies performed on some carbonaceous materials, viz. crude oil and related materials (asphaltenes, kerogens, bitumens, and resins), and coals. Thiophene, sulfide, sulfoxide, sulfone, pyrite, and sulfate are found in varying amounts in these materials. In source rock bitumens, sulfoxide is more abundant than in the kerogens, while within the kerogens, the less aromatic Type I samples show a smaller ratio of thiophenic/sulfidic sulfur than in Type II samples. Petroleum asphaltenes have a similar sulfur chemistry, regardless of the source or the burial depth. Resins and oil fractions retain the polar sulfoxide species of the parent oil similar to the more polar asphaltenes fractions. More aromatic sulfur species also dominate in the more matured coals than in the younger coals. Studies of nitrogen XANES also reveal that aromatic forms of nitrogen prevail in samples with increased aromatic carbon.

Molecularly Imprinted Polymer Nanofibers for Adsorptive Desulfurization

Desulfurization of fuel oils is an essential process employed in petroleum refineries to reduce the sulfur concentration in fossil fuels in order to meet the mandated environmental protection limit of 10 ppm sulfur. The hydrodesulfurization (HDS) process, which is currently being employed for desulfurization, is limited in treating refractory organosulfur compounds as it only reduces sulfur content in fuels to a range of 200-500 ppm sulfur. Oxidative desulfurization (ODS) is considered a new technology for desulfurization of fuel oils as the process is capable of desulfurizing fuels to reach the ultra-low sulfur levels and can serve as a complementary step to HDS. The chapter discusses, briefly, the oxidation of refractory sulfur compounds found in fuels using vanadium as a catalyst to form organosulfones, a first step in ODS process. The chapter also discusses, in detail, the chemistry involved in molecular imprinting of organosulfones on functional polymers, and the electrospinning of the polymeric matrix to produce molecularly imprinted nanofibers employed for selective adsorption of organosulfones from the oxidized mildly hydrotreated fuels, a second step in the ODS process. Chemical interactions, apart from the imprinting effect, that can be exploited in molecularly imprinted polymers for selective extraction of organosulfones, such as hydrogen bonding, p-p interactions, van der Waals forces and electrostatic interactions, were discussed by employing density functional theory calculations. The possibilities of electrospinning on a large scale as well as prospects for future industrial applications of functional molecularly imprinted nanofibers in desulfurization are also discussed.

Polymolybdate Supported Nano Catalyst for Desulfurization of Diesel

The Catalytic oxidative desulfurization (Cat-ODS) comprises of molybdenum based catalyst, tert-butyl hydroperoxide (TBHP) as oxidant and dimethylformamide (DMF) as solvent for extraction. A series of polymolybdates supported alumina were prepared using the wet impregnation method. This potential catalyst was characterized by FTIR, FESEM-EDX and XPS for its physical properties. From catalytic testing, Fe/MoO3-Al2O3 calcined at 500°C was revealed as the most potential catalyst which gave the highest sulfur removal under mild condition .The sulfur content in commercial diesel was successfully reduced from 440 ppmw to 88 ppmw under mild condition followed by solvent extraction. Response surface methodology involving Box-Behnken was employed to evaluate and optimize Fe/MoO3/Al2O3 preparation parameters (calcination temperature, catalyst loading, and Fe loading) and their optimum values were found to be 550 ºC, 10 g/L, and 10%. of calcination temperature, catalyst loading, and Fe loading. Based on these results, the reaction mechanisms of peroxy oxygen were proposed.

Sulfur in Petroleum

This chapter describes the occurrence of organosulfur compounds in petroleum, their detrimental effects and various techniques for removal of these compounds. The sole commercial desulfurization process i.e. HDS is broadly discussed in terms of reaction conditions, different types of catalysts used, reactor design and mechanistic pathways in the process. The shortcomings of HDS and needs for developing new desulfurization techniques is also described. Various newly developed research techniques for desulfurization are also discussed with their technical backgrounds, commercial overview, advantages and shortcomings in the light of literature reports. These techniques include, Adsorptive desulfurization, Bio-desulfurization, Precipitative desulfurization, and Oxidative desulfurization with its sub types like ODS using H2O2- Polyoxometalates (POM), ODS with Ionic liquids, Photo-oxidative desulphurization and Ultrasound Assisted ODS.

Advances in the Reduction of the Costs Inherent to Fossil Fuels' Biodesulfurization towards Its Potential Industrial Application

Biodesulfurization (BDS) process consists on the use of microorganisms for the removal of sulfur from fossil fuels. Through BDS it is possible to treat most of the organosulfur compounds recalcitrant to the conventional hydrodesulfurization (HDS), the petroleum industry's solution, at mild operating conditions, without the need for molecular hydrogen or metal catalysts. This technique results in lower emissions, smaller residue production and less energy consumption, which makes BDS an eco-friendly process that can complement HDS making it more efficient. BDS has been extensively studied and much is already known about the process. Clearly, BDS presents advantages as a complementary technique to HDS; however its commercial use has been delayed by several limitations both upstream and downstream the process. This study will comprehensively review and discuss key issues, like reduction of the BDS costs, advances and/or challenges for a competitive BDS towards its potential industrial application aiming ultra low sulfur fuels.