Investigation of Prolonged Deactivation-Regeneration Regimes on the Dehydrogenation Activity of Platinum/Alumina Catalyst

Abstract

The various types of coke found deposited on a deactivated Pt/Al 2 O 3 reforming catalyst are described. They are claSsified into major types: oxidiZable (primary) coke, reducible (secondary) coke and non oxidizable and non reducible (tertiary) coke. Primary coke is generally non toxic to catalytic hydrocarbon conversion as its removal restores initial catalyst activity. The secondary and tertiary forms are, however, toxic to this reaction. A methodology for the prolongation of reforming catalyst life is evident from these results. In the new method, secondary coke is also removed from the catalyst surface subsequent to primary coke removal. Results of the application of this methodology using accelerated aging of Pt/Al 2 O 3 catalyst is presented. The overall catalyst life was extended for up to 52 deactivation-regeneration cycles from the 23 previously reported. Catalyst life was not correlated with the oxidizable and reducible * Present address: ORDER REPRINTS 284NGOMO AND SUSU coke content. These profiles were found to be aperiodic and exhibited a nonlinear dynamic behavior. In contrast, catalyst life per cycle of deactivation-regeneration correlate with the rate of oxidizable coke deposition. The model coking reaction investigated was the dehydrogenation of cyclohexane to benzene in nitrogen carrier at 430 • C on a commercial Pt/Al 2 O 3 catalyst using a Berty CSTR.

Long-Term Deactivation of Supported Pt Catalysts in the Dehydrogenation of Methylcyclohexane to Toluene

“…Developing a catalyst that can maintain high stability requires a deep understanding of the deactivation phenomena. Groups of researchers have investigated the deactivation of Pt/Al 2 O 3 catalysts in MCH dehydrogenation. – Some studies suggested that catalyst deactivation in MCH dehydrogenation is caused by two types of poison structures: one reversible and the other irreversible. – The reversible poison can be removed at normal operating temperature by a stream of pressurized hydrogen, whereas the irreversible poison cannot. The relative amount of each poison structure depends on the hydrogen partial pressure and the time “on-stream”.…”

“…Groups of researchers have investigated the deactivation of Pt/Al 2 O 3 catalysts in MCH dehydrogenation. [1][2][3][4][5][6][7][8] Some studies suggested that catalyst deactivation in MCH dehydrogenation is caused by two types of poison structures: one reversible and the other irreversible. [2][3][4] The reversible poison can be removed at normal operating temperature by a stream of pressurized hydrogen, whereas the irreversible poison cannot.…”

“…[1][2][3][4][5][6][7][8] Some studies suggested that catalyst deactivation in MCH dehydrogenation is caused by two types of poison structures: one reversible and the other irreversible. [2][3][4] The reversible poison can be removed at normal operating temperature by a stream of pressurized hydrogen, whereas the irreversible poison cannot. The relative amount of each poison structure depends on the hydrogen partial pressure and the time "on-stream".…”

Coke Removal in Fuel-Cooled Thermal Management Systems

“…5 It is important to note that there have been many books, papers, and patents on coke deposition research as well as coke removal and surface regeneration from catalyst surfaces. [6][7][8][9][10][11] The objective of this study is to investigate and assess the practicality of various in situ surface regeneration techniques for realistic passage sizes and to develop a safe, simple, and cost-effective in situ surface regeneration technique for hydrocarbon fuel-cooled thermal management systems. Thermogravimetric analysis (TGA) was adopted in this study for quickly evaluating various coke-removal processes and compiling a database for kinetic analysis.…”

“…In previous work, UTRC has also shown that different elements (e.g., carbon and sulfur) are burned off at different temperatures and that further development of the regeneration process is required . It is important to note that there have been many books, papers, and patents on coke deposition research as well as coke removal and surface regeneration from catalyst surfaces. − …”