580784 The Role of Phosphorus on Vanadia Catalyst for the Selective Oxidation of n-Butane to Maleic Anhydride

Wednesday, June 5, 2019: 3:21 PM
Texas Ballroom A (Grand Hyatt San Antonio)
Jingxiu Xie1, Christian Schulz1, K. Knemeyer2, R. Naumann d‘Alnoncourt2, Benjamin Frank1, Ralph Kraehnert1 and Frank Rosowski1, (1)BasCat – Unicat BASF JointLab, Berlin, Germany, (2)BasCat - Unicat BASF JointLab, Berlin, Germany

The Role of Phosphorus on Vanadia Catalyst for the Selective Oxidation of n-Butane to Maleic Anhydride


J. Xie1, C. Schulz1, K. Knemeyer1, R. Naumann d‘Alnoncourt1, B. Frank1, R. Kraehnert1, F. Rosowski1,2


1  BasCat – Unicat BASF JointLab, Hardenbergstr. 36, Berlin, 10623, Germany

2 BASF SE, Carl-Bosch-Straße 38, Ludwigshafen, 67056, Germany


Selective oxidation of lower alkanes (ethane, propane, and n-butane) converts these less reactive molecules to valuable chemicals in a resource-efficient and environmentally friendly approach. The selective oxidation of n-butane to maleic anhydride, catalyzed by vanadyl pyrophosphate (VPP), is an important industrial process with a worldwide capacity of more than 500 kton annually. However, its reaction mechanism and active sites remain debatable due to the complexity and dynamic surfaces of VPP under reaction conditions. In this work, the role of phosphorus on the reaction network and mechanism for the selective oxidation of n-butane to maleic anhydride (MAN) is investigated.

The study focuses on two catalysts, namely V2O5 and phosphorus-modified V2O5, (POxV2O5), which was synthesized by atomic layer deposition (ALD) of phosphorus on the V2O5 surface. Parameter field studies of POxV2O5 and V2O5 were carried out to compare the reaction networks. Additional co-feed studies of 1-butene and MAN were performed to probe deeper into specific reaction pathways, such as consecutive reactions of 1-butene and MAN.

The elemental loading of P was measured by ICP to be 0.1 %wt., which is 0.7 theoretical monolayer coverage of V surface atoms. From the parameter field study, both catalysts produced MAN and depositing 0.1 w% P via ALD increased MAN selectivity. The combined selectivities to MAN, CO and CO2 was more than 90 % for both catalysts, and the minor products include 1-butene, acrylic acid, acetic acid, and acetaldehyde. 1-butene and MAN were identified play important roles in the reaction mechanism, thus additional co-feed studies were performed. Complete conversion of the 1-butene co-feed were observed for both catalysts, but n-butane conversion was not significantly affected by the co-feeding of 1-butene. This demonstrates the higher reactivity of 1-butene in comparison to n-butane, and the possibly lack of competitive adsorption between n-butane and 1-butene. From Figure 1a, product selectivities of n-butane and 1-butene were similar, thereby suggesting that P deposition has negligible influence on product selectivities from 1-butene.  With MAN co-fed, the consecutive oxidation of MAN was largely suppressed upon P addition (Figure 1b). Without P deposition, MAN was oxidized mainly to CO and CO2 (Figure 1c). The difference in CO/CO2 ratio of n-butane. 1-butene and MAN is also used as a descriptor for selective oxidation. The results underline the strong impact of P on the kinetics of the reaction network. This contribution will discuss and compare the reaction networks for both catalysts in order to reveal the role of P in the selective oxidation of n-butane to MAN.

Figure 1. A) Product selectivities of n-butane and 1%v 1-butene co-feed, B) MAN outlet concentrations as a function of MAN co-feed concentrations and C) products from 0.5 %v MAN co-feed at 420 °C, 1 bar, C4H10/O2/H2O= 2/20/3 %v, 2000 h-1.


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