Thiophene poisoning

Hydrogenolysis of adsorbed thiophene (poison) is the rate determining step. Sulfur resistance was Pt > Pt-Ir > Pt-Re.65 66 ... 

The purpose of the present paper is an experimental and modeling study of the effects of thiophene poisoning on the behaviour of diffusionally influenced Ni/Al203 pellet during benzene hydrogenation. 

The problem of decrease in catalyst activity due an irreversible adsorption of poison was solved numerically using a single point collocation approximation. The numerical results are compared with experimental data obtained by measuring concentration changes due to thiophene poisoning of Ni/AljO in benzene hydrogenation. 

Equations 9 and 10 show how the thiophene mole fraction in the gas and the concentration of unpoisoned sites varies with time (T) and position (m ) in the reactor and both of these equations can be graphed using the calculated values for the rate of thiophene poisoning and active site concentration as well as the experimental conditions. Figures 2 and 3 show the ratio of the instantaneous to initial thiophene mole fraction and active site balance, respectively, as a function of reduced length down the bed at several different reduced times for Catalyst A . Figures 4 and 5 show the same ratios for Catalyst C . 

A comparison of Figures 1 and 2 shows that at 16 hours (T = 1.44), the benzene conversion for Catalyst A is around 45% but greater than 60% for thiophene. Similarly, a comparison of Figures 1 and 4 shows that at 16 hours (T=0.29) for Catalyst C , benzene conversion is still about 78% but the conversion of thiophene is around 40%. These results suggest that Catalyst C is less susceptible to thiophene poisoning which results in better benzene conversion over the life of the catalyst. This makes Catalyst C a good choice for benzene hydrogenation unless the amount of residual sulfur in the product exceeds specifications. 

Catalytic hydrogenation converts pyrrole and furan into the corresponding saturated heterocycles, pyrrolidine and tetrahydrofuran. Since thiophene poisons most catalysts, tetrahydrothiophene is synthesized instead from open-chain compounds. 

COMPARATIVE STUDY OF THE DEACTIVATION OF GROUP VIII METAL CATALYSTS BY THIOPHENE POISONING IN ETHYLBENZENE HYDROGENATION... 

The deactivation of Group VIII metal catalysts by thiophene poisoning In ethylbenzene hydrogenation has been studied. With the exception of Pt, the sequence of sulfur resistance found, Pt < Pd < N1 < Rh < Ru, correlates with the decreasing order of the density of states at the Fermi level. This behavior is explained by a competitive adsorption of both ethylbenzene and thiophene on the metal sites, which is related to the basicity of the organic compounds and the electronic structure of the metals. This hypothesis is supported by XPS analysis of both the fresh and poisoned catalysts. 

S. Zmcevic, Z. Gomzi and E. Kotur, Thiophene poisoning of Ni-Si02-Al203 in benzene hydrogenation. Deactivation Kinetics, Ind.Eng.Chem.Res. 29(1990)774. 

By ESR study of nickel catalysts supported on K-clinoptilolite containing iron, a correlation was fotmd between the Ni-Fe interaction and the resistance of the catalyst to thiophene poisoning [93 A2]. 

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