Highly selective and stable multimetallic catalysts for propane dehydrogenation

Abstract

Different mono (Pt), bi (Pt±Sn, Pt±Pb, Pt±Ga) and trimetallic (Pt±Sn±Ga) catalysts based on Pt and supported on different materials (Al 2 O 3 , Al 2 O 3 ±K and ZnAl 2 O 4 ) were tested under severe process conditions in the propane dehydrogenation reaction (both in continuous and in pulse reactors). Results show that the Pt±Sn±Ga/ZnAl 2 O 4 catalyst has a better and more stable performance in propane dehydrogenation (high yield to propene and low coke deposition), than the other bi-and trimetallic systems and a commercial catalyst. Thus, the use of an adequate support (ZnAl 2 O 4 ) in combination with the addition of Ga to the Pt±Sn bimetallic system enhances the catalytic performance. INTRODUCTIONThe selective propane dehydrogenation to propene is a very important industrial process since it produces a valuable raw material for polypropene manufacture. This process can be carried out by using supported metallic catalysts, though several dif®culties should be avoided in order to develop catalysts with a good performance. In this sense, both the inhibition of hydrogenolysis and cracking reactions, and the minimisation of the coke deposition, are major requirements in order to increase the selectivity to propene and the catalytic stability. From the development of the STAR Process, 1 different bimetallic supported systems have been studied in this reaction. The utilisation of non-acidic and thermal stable supports, such as MgAl 2 O 4 or ZnAl 2 O 4 , 2±4 appears as an important factor in order to increase the stability of the metallic phase during successive operational cycles. Besides, the addition of Sn to Pt improves alkene formation and reduces coke deposition. 5 Hence, both the selection of an adequate support and the composition of the metallic phase can be considered as relevant factors in order to develop better catalysts for this process.In this paper, the behaviour of different catalysts (Pt, Pt±Sn, Pt±Ga, Pt±Pb and Pt±Sn±Ga supported on Al 2 O 3 , K±Al 2 O 3 and ZnAl 2 O 4 ) in the propane dehydrogenation reaction are compared with a commercial catalyst used for dehydrogenation of alkanes on an industrial scale. The effects of the three different supports and the addition of several inactive metals of

Electronic density enrichment of Pt catalysts by coke in the propane dehydrogenation

“…There have been many studies on catalytic stability in the propane dehydrogenation [8][9][10][11]. However, they focused on decrease in catalytic activity by the coke formation or change in coke mobility due to the interaction of the second metal with Pt.…”

Propane Dehydrogenation Over PtSn Catalysts Supported on ZnO-Modified MgAl2O4

“…Pt/A1 2 O 3 and PtSn/A1 2 O 3 catalyst have been widely used in hydrocarbon dehydrogenation [1][2][3][4][5][6], however, regarding the stability of the catalysts, the dehydrogenation performance of PtSn catalysts is still not satisfactory, several researches have been reported in improving the catalytic stability of supported PtSn catalysts for low paraffin dehydrogenation by adding various promoters to PtSn/c-Al 2 O 3 catalyst [7][8][9][10][11] and by using other supports instead of c-Al 2 O 3 [12][13][14][15][16][17]. MgAl 2 O 4 and ZnAl 2 O 4 have characteristic of thermal stability, high mechanical strength, low surface acidity, which can be better adapted to low-carbon alkane dehydrogenation process of severe reaction conditions [18,19].…”

Propane dehydrogenation to propylene over Pt-based catalysts

“…Numerous studies have shown that Sn promoter is a crucial component of platinum-based catalysts for the high dehydrogenation performance of light paraffin [1][2][3][4]. Nowadays, a lot of research work is being carried out to further improve the stability, selectivity and activity of Pt-Sn catalysts by the addition of some alkali metals such as Li, Ba, K, Ca and others, or by the utilization of non-acidic and thermal stable supports, such as MgAl 2 O 4 and ZnAl 2 O 4 [5][6][7][8]. However, the dehydrogenation performance of Pt-Sn catalysts is still not very satisfactory, especially in the stability and selectivity.…”