Diesel posttreatment

Two chemical processes have been selected by automotive makers lean NO e trap (LNT) [11] or NO c storage reduction (NSR) and selective catalytic reduction by ammonia (SCR-NH3) [12]. For LNT process, the cost is very expensive, because a large amount of noble metal is required. It is why the second possibility (SCR-NH3) has paid attention and has been developed first on trucks and bus. The result is positive in terms of efficiency and decrease of pollutants, but the required location remains a major problem especially when the technology must be applied to a particular vehicle. In order to improve the process, a new concept has been proposed and involves bringing together two technologies into one. In this chapter, we will describe the integration of the SCR-NH3 catalyst in the structure of the particles filters for application in diesel posttreatment. 

The catalytic cracking unit is often referred to as the gasoline workhorse of a refining unit. As shown in Fig. 18.9, feeds to the catalytic cracking unit are gas oils from the atmospheric and vacuum distillation columns and delayed coker. These heavier fractions also carry metals such as nickel, vanadium, and iron. More important, sulfur compounds concentrate in the heavier product fractions. Table 18.8 lists a typical mass balance for sulfur.25 FCC blend-stocks comprise 36 percent of the volume of the gasoline pool. However, this stream also contributes 98 percent of the sulfur concentration to blended procucts.25 As specifications on sulfur concentrations in diesel and gasoline tighten, more efforts are focused on how feeds and product streams from the FCC are pre- and posttreated for sulfur concentrations. 

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