Desulfurization ultradeep

Desulfurization processes are absolutely necessary for producing clean fuels. Possible strategies to realize ultradeep suffiirization currently include adsorption, extraction, oxidation, and bioprocesses. Oxidative desulfurization (ODS) combined with extraction is considered one of the most promising of these processes [13]. Ultradeep desulfurization of diesel by selective oxidation with amphiphilic catalyst assembled in emulsion droplets has given results where the sulfur level of desulfurized diesel can be lowered from 500 ppm to about 0.1 ppm without changing the properties of the diesel [12]. 

Ultradeep desulfurization of fuel oils is used for producing not only clean fuels but also sulfur-free hydrogen used in fuel-cell systems, in which the hydrogen can be produced potentially through the reforming of fuel oils. Fuel-cell systems must be run with little-to-no sulfur content, because sulfur can irreversibly poison the precious metal catalysts and electrodes used [12]. 

The ultradeep desulfurization of the current infrastructure fuels has become a bottleneck in the production of H2 for fuel cell applications. It is urgent to develop a more efficient and environmentally friendly process and technology for the ultradeep desulfurization of the hydrocarbon fuels. Consequently, many approaches have been conducted in order to improve the conventional HDS process and to develop new alternative processes. These approaches include catalytic HDS with improved and new catalysts, reactor and/or process, adsorptive desulfurization,27 oxidative desulfurization (ODS), extractive desulfurization (EDS), and biodesulfurization (BDS) by using special bacteria and others. Some of these works were reviewed recently by Topsoe et al.,15 Whitehurst et al.,28 Kabe et al.,29 Cicero et al.,30 Babich and Moulijn,31 Dhar et al.,32 Song,33 Song and Ma,16,34 Bej et al.,35 Mochida and Choi,36 Hemandez-Maldonado and Yang,37,38 Hemandez-Maldonado et al.,39 Topsoe,40 Brunet et al.,41 Gupta et al.,42 and Ito and van Veen.43... 

The present chapter will review the present state of the art and challenges in the ultradeep desulfurization of natural gas, gasoline, jet fuel, diesel, reformate, and syngas from coal gasifier by HDS, selective adsorption, solvent absorption, and ODS, respectively. 

As shown above, since the different adsorbents may be suitable for separating different sulfur compounds from different hydrocarbon streams and some coexisting species, such as polyaromatic hydrocarbons and moisture, in hydrocarbon streams might inhibit the adsorption of sulfur compounds on the sorbent, a combination of two or more sorbents in an adsorptive desulfurization process might be more efficient for a practical ultradeep desulfurization process. 

Current progress in HDS via improvement of conventional catalysts, reactors, and processes or development of new catalysts, reactors, and processes has allowed the refining industry to be able to produce the low-sulfur fuels to meet the new EPA regulation. However, the current HDS technology is still difficult or costly to produce the ultraclean liquid hydrocarbon fuels for fuel cell applications. Adsorptive desulfurization and ODS are two promising alterable technologies for ultradeep desulfurization of hydrocarbons fuels for fuel cell applications. 

A combination of multidesulfurization technologies together, such as HDS and ADS (adsorptive desulfurization), ODS and ADS, and solvent scrubbing and adsorption, has become a trend in research and development to achieve ultradeep desulfurization technology of the hydrocarbon fuels for environmental protection, hydrogen production, and fuel cell applications. 

A major challenge in the ultradeep desulfurization of hydrocarbon fuels is the inhibiting effects of fuel components (e.g., nitrogen compounds) and reaction products (e.g., hydrogen sulfide). While this area has been studied in catalysis literature, it is expected to gain increased attention because of the severity of the new sulfur specifications. ... 

Ultradeep desulfurization approaches include 1) improving catalytic activity by new catalyst formulation for HDS of 4,6-DMDBT 2) tailoring reaction and process conditions 3) designing new reactor configurations and 4) developing new processes. One or more approaches may be employed by a refinery to meet the challenges of producing ultraclean fuels at an affordable cost. 

Among the new process concepts, design approaches for ultradeep desulfurization focus on several different areas.Some researchers are looking at adsorption and sulfur atom extraction-removing sulfur by using... 

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