Thiophenes hydrodesulfurization models

Figure 7.18. Dependence of the rate of thiophene hydrodesulfurization on the partial pressures of thiophene at different temperatures, along with fits according to the Langmuir-Hinshelwood model, Eq. (32). [Fron A. Borgna and J.W. Niemantsverdriet, to be published (2003).]...

Some samples of the TS and P series have been chosen for tests using model compounds in order to evaluate the deactivation. Conversions obtained for toluene hydrogenation at 3509C, cyclohexane isomerization at 380 and 400°C and thiophene hydrodesulfurization at 220°C are reported in Table 1. 

The texture and morphology of the synthesized objects were studied by the set of the instrumental methods XRD, FT-IR, SEM, TEM, BET, N2 adsorption-desorption. Model reaction of thiophene hydrodesulfurization (HDS) was used to investigate the chemical mobility of Ni-containing particles obtained by different ways. 

P. Mills, S. Korlaim, M.E. Bussell, M.A. Reynolds, M.V. Ovchinnikov, R.J. Angelici, C. Stinner, T. Weber R. Prins (2001). J. Phys. Chem. A, 105, 4418-4429. Vibrational study of organometallic complexes with thiophene ligands Models for adsorbed thiophene on hydrodesulfurization catalysts. 

Here we illustrate how to use kinetic data to establish a power rate law, and how to derive rate constants, equilibrium constants of adsorption and even heats of adsorption when a kinetic model is available. We use the catalytic hydrodesulfurization of thiophene over a sulfidic nickel-promoted M0S2 catalyst as an example ... 

Thiophene is the typical model compound, which has been extensively studied for typifying gasoline HDS. Although, some results are not completely understood, a reaction network has been proposed by Van Parijs and Froment, to explain their own results, which were obtained in a comprehensive set of conditions. In this network, thiophene is hydrodesulfurized to give a mixture of -butenes, followed by further hydrogenation to butane. On the considered reaction conditions, tetrahydrothiophene and butadiene were not observed [43], The consistency between the functional forms of the rate equations for the HDS of benzothiophene and thiophene, based on the dissociative adsorption of hydrogen, were identical [43,44], suggesting equivalent mechanisms. 

In this paper deactivation of the hydrodesulfurization (HDS) catalysts is examined using the results obtained for the thiophene conversion on the supported phosphormolybdenum heteropolyacid as a model catalyst. 

Removal of thiophene impurities from petroleum feedstocks is accomplished by a process called hydrodesulfurization (HDS) which involves the insertion of metals into the thiophene ring between the C-S bond. In order to better understand the mechanism of this reaction, different groups have utilized selenophene model systems due to the enhanced NMR characteristics of Se. Metal complexes of selenophenes that have been studied include rhodium <19970M2751>, molybdenum <2006POL499>, manganese <20010M3617, 19950M332>, chromium... 

Because of these special characteristics the complex [(triphos)Ir(Ti -benzene)]BF4 has been successfully used as a precursor in modeling a complete stepwise hydrodesulfurization reaction in solution by the sequential addition of thiophene, H and H as shown in Fig. 4.3 [27],... 

Allied with design and preparation, catalyst testing is the exploratory screening of candidate catalysts. This phase does not yield either kinetics or process variables but merely ranks performance. Bench reactors used should be as simple and rapid as possible, for many samples are usually tested. For ease in operation and interpretation, model compound reactions are helpful. Thus, for example, cumene dealkylation is a model for catalytic cracking, and thiophene hydrogenolysts for hydrodesulfurization. Care must be taken to ensure that the model system does indeed parallel process performance. 

In a further work, Tang and Curtis26 have studied the influence of the tyre components by replacing coal with model compounds 4-(l-naphthylmethyl)-bibenzyl (NMBB), dibenzothiophene and 5-methyl-8-(l-methylethyl)dibenzo-thiophen-4-ol (MMDH). Carbon black was active for the NMBB hydrocracking, whereas little activity was found with SBR, waste tyres and waste tyre liquefaction residues. However, when the latter residues were previously heat treated to remove organic coatings and recover the carbon black component, significant NMBB conversions were observed. Moreover, both carbon black and heat-treated residues were active for the hydrodesulfurization of dibenzothiophene and MMDH, particularly when combined with Mo naphthenate and S. These results confirm the catalytic properties of carbon black in coal-tyre coliquefaction, provided that its surface area is accessible. 

Studies of nucleophilic attack on the 7r-bound benzo[b]thiophene (BT) complexes [CpRu(BT)] and [Cp Ir(BT)] have been undertaken as potential models for the reactions of BT on hydrodesulfurization (HDS) catalysts. In these complexes, the BT coordinates to the metal via the benzene rather than the thiophene ring. A range of nucleophiles, including hydrides and sulfides which are proposed to be present on HDS catalyst surfaces, add to the benzene ring to give primarily C-7 adducts see Eq. (24). However, products that might be precursors to, or are similar to, proposed intermediates in the HDS of BT, such as... 

A major advantage of the models of Rieckmann and Keil [44] and Wood et al. [16] was that, unlike earlier studies, any general reaction kinetics could be incorporated into the computer simulation. This means that reactions of industrial interest, which are typically represented by Langmuir-Hinshelwood kinetics, could be represented. Wood et al. [16] chose the hydrodesulfurization of thiophene as an example reaction, using the kinetic measurements of Van Parijs et al. [45] in their simulations. The kinetic model assumes that first thiophene is hydrogenated to butene, then butene is hydrogenated to butane ... 

Hydrodesulfurization. Several model compound studies have been undertaken to understand the mechanism of sulfur removal during coal liquefaction. Hydrodesulfurization of thiophene has been reported by Amberg and his co-workers (86-91), Schuit and Gates (92), Lipsch and Schuit (67) and Shah and Cronauer (55). 

Satterfield, C.N., M. Modell and J.R. Mayer. "Interaction between Catalytic Hydrodesulfurization of Thiophene and Hydrode-nitrogenation of Pyridine." AIChE J. (6) (1975) 1100. 

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