scispace - formally typeset
Search or ask a question
Author

P. Arnoldy

Bio: P. Arnoldy is an academic researcher from University of Amsterdam. The author has contributed to research in topics: Temperature-programmed reduction & Calcination. The author has an hindex of 11, co-authored 12 publications receiving 1292 citations.

Papers
More filters
Journal ArticleDOI
TL;DR: In this article, it was shown that temperature-programmed reduction (TPR) is a sensitive technique for the characterization of Co and Co-Aloxidic phases in CoOAl2O3 catalysts.

611 citations

Journal ArticleDOI
TL;DR: In this paper, a consistent interpretation of the complex TPR results is constructed, in which the extent of H/sub 2/ dissociation catalyzed by low-valent Mo atoms plays a central role.
Abstract: The reduction of MoO/sub 3/ and MoO/sub 2/ is studied by temperature-programmed reduction (TPR). TPR patterns appear to be highly dependent on H/sub 2/O content of the reducing mixture, sample size, precalcination temperature, and heating rate. Activation energy values for reduction have been calculated from TPR series with various heating rates. A consistent interpretation of the complex TPR results is constructed, in which the extent of H/sub 2/ dissociation catalyzed by low-valent Mo atoms plays a central role. The formation of these Mo catalytic sites is found to depend on H/sub 2/O pressure, concentration of surface defects, and surface area. Reduction of MoO/sub 3/ to MoO/sub 2/ and of MoO/sub 2/ to Mo metal both can be catalyzed, in which case the rate-determining step is either H/sub 2/ dissociation, when the formation of catalytic sites is limited, or Mo-O bond breaking, when excess catalytic sites are present. Reduction of MoO/sub 3/ to MoO/sub 2/ can also take place noncatalyzed, with oxygen diffusion as rate-determining step. MoO/sub 2/ and Mo metal are also formed, as intermediates, in temperature-programmed sulfiding (TPS) of MoO/sub 3/. MoO/sub 2/ production is faster in H/sub 2//H/sub 2/S than in H/sub 2/ due to a different reductionmore » mechanism involving H/sub 2/S as primary reactant. The formation of Mo metal is also faster, due to a higher porosity of the MoO/sub 2/ formed in situ. 48 references, 13 figures, 1 table.« less

214 citations

Journal ArticleDOI
TL;DR: In this article, temperature-programmed reduction (TPR) gives new information on the reducibility of CoOMoO3Al2O3 catalysts.

108 citations

Journal ArticleDOI
TL;DR: The sulfidability and hydrodesulfurization (HDS) activity of Mo catalysts supported on SiO{sub 2, carbon and Al{sub O{sub 3} have been studied in this article.

96 citations

Journal ArticleDOI
TL;DR: In this paper, temperature-programmed reduction (TPR) has been applied to characterize the reducibility of Al2O3, SiO2-, and carbon-supported Re2O7 catalysts, over a wide range of transition metal content.

74 citations


Cited by
More filters
Journal ArticleDOI
01 Jan 1998-Carbon
TL;DR: In this paper, the increasing importance of carbon materials in catalytic processes is analyzed in terms of the most important characteristics of these materials when acting as catalysts or catalyst supports, such as surface area, porosity, chemical inertness and oxygen surface groups.

1,620 citations

Journal ArticleDOI
TL;DR: The as-prepared cobalt oxide (assigned as CoO x ) was fabricated by precipitation-oxidation from aqueous cobalt nitrate solution using sodium hydroxide and oxidation with hydrogen peroxide as mentioned in this paper.

707 citations

Journal ArticleDOI
TL;DR: In this paper, the causes of deactivation and the influence on reaction rate are discussed and methods for minimising catalyst deactivation, by tailoring catalyst properties and/or process operations, are presented.
Abstract: Catalyst deactivation is usually inevitable, although the rate at which it occurs varies greatly. This article discusses the causes of deactivation and the influence on reaction rate. Methods for minimising catalyst deactivation, by tailoring catalyst properties and/or process operations, are presented, as well as reactor configurations suitable for the regeneration of deactivated catalysts. Alkane dehydrogenation is used as an example to demonstrate the variety of engineering solutions possible.

639 citations

Journal ArticleDOI
TL;DR: Manganese oxides of different crystallinity, oxidation state and specific surface area have been used in the selective catalytic reduction (SCR) of nitric oxide with ammonia, indicating a relation between the SCR process and active surface oxygen.
Abstract: Manganese oxides of different crystallinity, oxidation state and specific surface area have been used in the selective catalytic reduction (SCR) of nitric oxide with ammonia between 385 and 575 K. MnO2 appears to exhibit the highest activity per unit surface area, followed by Mn5O8, Mn2O3, Mn3O4 and MnO, in that order. This SCR activity correlates with the onset of reduction in temperature-programmed reduction (TPR) experiments, indicating a relation between the SCR process and active surface oxygen. Mn2O3 is preferred in SCR since its selectivity towards nitrogen formation during this process is the highest. In all cases the selectivity decreases with increasing temperature. The oxidation state of the manganese, the crystallinity and the specific surface area are decisive for the performance of the oxides. The specific surface area correlates well with the nitric oxide reduction activity. The nitrous oxide originates from a reaction between nitric oxide and ammonia below 475 K and from oxidation of ammonia at higher temperatures, proven by using 15NH3. Participation of the bulk oxygen of the manganese oxides can be excluded, since TPR reveals that the bulk oxidation state remains unchanged during SCR, except for MnO, which is transformed into Mn3O4 under the applied conditions. In the oxidation of ammonia the degree of oxidation of the nitrogen containing products (N2, N2O, NO) increases with increasing temperature and with increasing oxidation state of the manganese. A reaction model is proposed to account for the observed phenomena.

634 citations