Hydrodesulfurization process description

In this chapter, brief descriptions of the various hydrodesulfurization processes are presented with some attempt to illustrate how the processes vary in their capacity to treat the heavier feedstocks to yield the desired low-sulfur products. There are many processes described in the technical and commercial literature, but a large proportion of these processes (although actively reported) have not yet left the pilot (or exploratory) stage and are, perhaps, a considerable way from commercialization. Thus, the processes described in this chapter are the more common, but commercially proven, processes with the inclusion of some of the more promising processes that have entered the demonstration stage. 

In this section, we attack the problem of kinetics in multicomponent mixtures, and we dedicate attention mostly to the case where one is only interested in, or may only be able to determine experimentally, some overall concentration of species of a certain class, such as sulfurated compounds in an oil cut during a hydrodesulfurization process. The presentation is given in terms of a continuous description special cases of the corresponding discrete description are discussed as the need arises. Instead of working with the masses of individual species, we will work with their mass concentration distribution c x). In the case of a batch reactor, the distinction is irrelevant, but in the case of a plug flow reactor the concentration-based description is clearly preferable. The discussion is presented in purely kinetic terms for, say, a batch reactor. 

From the preceding discussion, it can be seen that the mathematical description of the chemical transformations involved in product formation can be extremely difficult. However, knowledge of the response of HDS reaction rates to different kinds of feed components and byproducts is extremely important for designing new processes that will allow refineries to meet the stringent standards of the future. The following text attempts to summarize the observations reported in the literature on the effects of inhibitors on the hydrodesulfurization rates of alkyl-substituted dibenzo-thiophenes. It is quite possible that many reports have been overlooked, and the present authors apologize for any oversights that may have occurred in this review. 

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