Dynamic processes on vanadium phosphorous oxides for selective alkane oxidation

doi:10.1016/S0920-5861(96)00073-9

Catalysis Today

Volume 32, Issues 1–4, 16 December 1996, Pages 29-36

https://doi.org/10.1016/S0920-5861(96)00073-9 Get rights and content

Abstract

The use of complementary physicochemical tools (XRD, Raman spectroscopy, XPS, ³¹P NMR, and electron microscopy techniques), sometimes used in in situ conditions has allowed to evidence the dynamic processes occurring during the oxidation of light alkanes on the vanadium phosphorus oxide (VPO) system. The transformations of the VPO system in the course of the oxidation of n-butane to maleic anhydride and of the oxidation of propane to acrylic acid are contrasted in connection with the evolution of the catalytic performances.

References (19)

E. Bordes
Catal Today
(1987)
F. Ben Abdelouahab et al.
J. Catal.
(1992)
R.A. Overbeek et al.
M. Abon et al.
J. Catal.
(1995)
G.J. Hutchings
Appl. Catal.
(1991)
M. Ai
J. Catal.
(1986)
J. Haber
J.C. Védrine et al.
Catal. Today
(1996)
R.K Grasselli et al.

There are more references available in the full text version of this article.

Cited by (63)

Modeling the selective oxidation of n-butane to maleic anhydride: From active site to industrial reactor
2022, Catalysis Today
In this contribution to the Special Issue honoring 100 very successful years of Casale S.A., we review and critically discuss the current status of modeling the most demanding selective partial oxidation reaction industrially applied: the partial oxidation of n-butane to maleic anhydride. We examine theoretical model descriptions of this partial oxidation reaction covering all relevant length scales: from modeling the active site and elementary steps, microkinetic and macrokinetic models, to reactor models on all length scales from laboratory reactors up to industrial-size production reactors. We also include in our manuscript the latest CFD developments aiming at a better understanding of heat and mass transfer in industrial catalyst beds as well as effects of the local bed structure. The contribution also covers relevant experimental findings with respect to the catalytically active species or sites on the catalyst surface, the reaction mechanism as well as microkinetic considerations. 60 years of research have greatly improved our understanding of the selective partial oxidation reaction. However, a critical review of the different aspects of the n-butane oxidation and its industrially used catalyst reveals on all length scales that there still remain unanswered questions, and that there are still some inconsistencies in our fundamental understanding. This situation arises from the fact that the catalyst for n-butane partial oxidation is a highly complex and dynamic system and its performance depends on all details of its generation and its operational history.
Transient behavior of vanadyl pyrophosphate catalysts during the partial oxidation of n-butane in industrial-sized, fixed bed reactors
2016, Applied Catalysis A: General
Citation Excerpt :
This scheme does also explain the relation between phosphorus content, activity and selectivity, according to the works of Cavani et al. [13,14], and finally, the enormous impact of the addition of only small amounts of TMP to the industrial reactor. On the other hand, too high phosphorus contents prevent the oxidation of the VPP bulk (, , , in Fig. 9) [9,13,16,25] and inhibit the formation of the active surface. If additionally water is not added to the system, the excess phosphorus cannot diffuse easily into the bulk of the catalyst.
The industrially important application of vanadium phosphorus oxide catalysts is the partial oxidation of n -butane in multi-tubular fixed bed reactors. Despite many decades of investigation about the functionality of the catalyst, the reaction mechanism is still under debate. However, the loss of phosphorus from the catalyst as a technically important phenomenon was until now hardly considered in the scientific literature: this phosphorus loss during long term operation has a strong effect on the temperature distribution in the reactor, which in turn significantly affects the catalyst selectivity. Therefore, technical reactor operation usually requires the addition of ppm levels of an organic phosphorus compound together with water to the reactor feed. For a macro-scale investigation of the phosphorus dynamics, the present study reports elaborated experiments in an industrial scale fixed bed reactor. The experiments revealed significant changes in catalyst activity and reactor performance induced by only minor variations in the feed contents of phosphorus and water as function of butane feed and space velocity, as well as strong interactions between these two additional feed components. These observations are further related to the many literature reports about the active catalyst surface. Common aspects explaining the dynamic catalyst behavior were combined in a new scheme for the VPP/VPO surface chemistry.
Effect of water on oxidative scission of 1-butene to acetic acid over V<inf>2</inf>O<inf>5</inf>-TiO<inf>2</inf> catalyst. Transient isotopic and kinetic study
2011, Applied Catalysis A: General
The role of water in the oxidation of 1-butene to AcOH over VOx-TiO₂ was investigated using spectroscopic and transient isotopic exchange methods. It was shown that the influence of water strongly depended on the temperature of reaction. In particular, DRIFTS and NH₃-TPD studies confirmed the temperature influence on the acidity and the amount of adsorbed water. XPS investigations suggested that not only oxygen from vanadia, but also from the lattice of titania was involved in the oxygen transfer during the reaction. Formation of oxidation products proceeded over two types of active vanadium oxide centers, i.e., VOH and VO. Hydrated vanadium species exhibited high selectivity towards AcOH formation. On the other hand, VO centers favored total oxidation. Kinetic model was developed for an unambiguous interpretation of the experimental results. Modelled reaction constants of the formation of AcOH over VOH centers were ca. 3.5 times higher than over VO centers. At the same time, the reaction rate constant of total oxidation in the presence of water was ca. 3.2 times lower than in dry flow. Estimated values suggested that in the presence of water the number of VOH centers was substantially lower than VO sites; however their contribution to the rate of AcOH formation was much higher.
Vanadium Phosphate Materials as Selective Oxidation Catalysts
2011, Advances in Catalysis
Citation Excerpt :
A number of groups have disputed this one-phase hypothesis. They suggested that V5+-containing phases are important in the active catalyst and are formed as a result of a redox mechanism (106–108). Bordes (94) cited the apparent need for two opposing conditions during the oxidation of butane as evidence for a multiphase active catalyst.
Vanadium phosphates have been established as selective hydrocarbon oxidation catalysts for more than 40 years. Their primary use commercially has been in the production of maleic anhydride (MA) from n-butane. During this period, improvements in the yield of MA have been sought. Strategies to achieve these improvements have included the addition of secondary metal ions to the catalyst, optimization of the catalyst precursor formation, and intensification of the selective oxidation process through improved reactor technology. The mechanism of the reaction continues to be an active subject of research, and the role of the bulk catalyst structure and an amorphous surface layer are considered here with respect to the various V–P–O phases present. The active site of the catalyst is considered to consist of V⁴⁺ and V⁵⁺ couples, and their respective incidence and roles are examined in detail here. The complex and extensive nature of the oxidation, which for butane oxidation to MA is a 14-electron transfer process, is of broad importance, particularly in view of the applications of vanadium phosphate catalysts to other processes. A perspective on the future use of vanadium phosphate catalysts is included in this review.
The design of a new ZrO<inf>2</inf>-supported V/P/O catalyst for n-butane oxidation to maleic anhydride: The build-up of the active phase during thermal treatment
2010, Catalysis Today
This study concerns the generation of the active V/P/O phase in supported catalysts used for n-butane oxidation to maleic anhydride. Catalysts were prepared by impregnating a zirconia support with ammonium vanadate and phosphoric acid, with subsequent thermal treatment under various environments and temperatures. The catalysts were studied by means of in situ Raman spectroscopy and reactivity measurements. It was found that the nature of the active surface is greatly affected both by the composition of the gas phase used for the thermal treatment, and by the P/V ratio used for catalyst preparation. δ-VOPO₄ was initially formed by the high-temperature reaction of vanadium salt with phosphoric acid; however, in the sample prepared with only 10% excess phosphorus (P/V atomic ratio = 1.1), δ-VOPO₄ transformed into either V₂O₅, in a steam-enriched air stream, or α_II- and β-VOPO₄, in a dry air stream. δ-VOPO₄ was more stable in the sample prepared with a large excess of P, i.e., with P/V = 1.3 and 1.5. The latter catalyst showed the best catalytic performance in n-butane oxidation. However, the performance was worse than that of the commercial unsupported vanadyl pyrophosphate catalyst.
Oxidation of propane to acrylic acid and acetic acid over alkaline earth-doped Mo-V-Sb-O<inf>x</inf> catalysts
2010, Journal of Natural Gas Chemistry
Alkaline earth metal (Mg, Ca, Sr and Ba)-doped Mo-V-Sb-O_xcatalysts, prepared by a dry-up method, have been investigated for their catalytic performance in the oxidation of propane under different reaction conditions. The catalysts have been characterized by N₂ adsorption-desorption, temperature-programmed desorption (TPD) of NH₃, SEM and XRD. Influence of water vapor on the catalytic performance, particularly on the selectivities to acetic acid and acrylic acid, has also been studied. The selectivity to acrylic acid was improved significantly by the doping of alkaline earth metals to Mo-V-Sb-O_xcatalysts. The surface acidic sites of the catalyst decreased with the doping of the catalyst with alkaline earth metals, which ultimately was found to be beneficial for obtaining high selectivity to acrylic acid. The catalytic activity and product selectivities were found to be influenced by the reaction temperature, C₃H₈/O₂ ratio and space velocity. A significant improvement in the selectivity to acrylic acid has also been observed by the addition of water vapor in the feed of propane and oxygen in the oxidation of propane.

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LectureDynamic processes on vanadium phosphorous oxides for selective alkane oxidation

Abstract

Catal Today

J. Catal.

J. Catal.

Appl. Catal.

J. Catal.

Catal. Today

Lecture
Dynamic processes on vanadium phosphorous oxides for selective alkane oxidation