Catalyst deactivation mechanism

Attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), 24 111-114 Attenuation, 77 132-133 Attenuation length (AL), 24 87-89 Attrition, catalyst deactivation mechanism, 5 256t... 

Solid soil detergency, 8 423-424, 428-433 Solid-solid reactions, catalyst deactivation mechanism, 5 256t, 278-280 Solid-solid sedimentation, 22 50 Solid solutions... 

The Rh-BINAP catalysts are very sensitive to impurities such as oxygen, moisture, and carbon dioxide. If an excess of water ([H20]/[Rh] = 15) is present in the reaction mixture, the isomerization is stopped aftera few turnovers with precipitation of air-stable red-brown crystals, which were found to be [ Rh(BINAP) 3()I3-0H)2 C104. X-Ray analysis of this complex (H20 was replaced by DzO) revealed a unique structure of a triangular Rh3 core capped with two triply bridging OH groups (Fig. 3.1). This Rh(I)-trinuclear complex was totally inactive as an isomerization catalyst, which suggests a catalyst deactivation mechanism [12], The effect of several additives on the isomerization of 2 with [Rh(BINAP)(COD)]+ has been examined, and the results are summarized in Table 3.3. 

The method is useful for kinetics under diffusion controlled conditions, for measuring actual internal diffusivities under reaction conditions, provided the kinetics are known and, above all, to study catalyst deactivation mechanisms and to establish what type of poisoning occurs. 

With the advent of more sophisticated testing methods and a better understanding of testing phenomena, we can expect to see more interest for the basic understanding of the underlying processes involved, such as Hydrocarbon Conversion Kinetics, Catalyst Deactivation Mechanisms, Multiphase Mass Transfer and Diffusion,etc. 

Understanding Claus Catalyst Deactivation Mechanisms Optimization of Alumina Using Physico-chemical Parameters... 

The catalytic epoxidation step may be considered to be the heart of the SMPO process. Tlie catalyst is prepared in a multistep gas-phase process by treatment of a silica carrier wifh fifanium tetrachloride, heating the obtained material, followed by steaming and silylation. Possible improvements to this process and research on the support material have already been reviewed [1]. Here, we discuss the nature of the active site, the mechanism of epoxidation, and the various catalyst deactivation mechanisms that exist for fhis unique cafalysf. 

Like every technically used and therefore real catalyst, the complex HRh(CO)-(TPPTSjj and the excess ligand TPPTS undergo a degree of decomposition that determines the catalyst s lifetime as measured in years. The catalyst deactivation mechanism is known in detail and depicted in Scheme 1 [5]. 

Of course, depending on the assumption for the underlying catalyst deactivation mechanism, the parameters n and m of Eq. (2.3.9) may have different values and, consequently, quite different equations can occur. Note that in the case of catalyst poisoning by a reaction the situation in the reactor can become rather complicated. For example, in a tube reactor, the catalyst deactivation process becomes then a function of the position in the tube. 

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