Effect on catalyst activity

Table IX lists the substances included in this study. The general conditions are given in Table X. Each impurity was added separately to the gas mixture and passed over C150-1-03 in order to determine its effect on catalyst activity. These tests were run under the primary methanation conditions, but in a small 3/8-in. tube reactor on sized, 10 X 12 mesh, catalyst.

One of the key challenges for this process is dealing with the wide range of contaminants in the waste HBr stream. Both inorganic and organic contaminants may be present. These contaminants are typically reactants and products of the upstream bromination process which generated the waste HBr. In addition, they may include corrosion products of upstream equipment or ionic materials present in the water used to scrub the gaseous bromination process effluent. The main concerns about contaminants in the feed streams are their effect on catalyst activity and stability and their effect on bromine product quality. 

The presence of halogen atoms appears to exert little, if any, effect on catalyst activity, but it can influence the course of the metathesis reaction. Vinylic halides are unreactive, as exemplified by the ring-opening polymerization of l-chloro-l,5-cyclooctadiene, which afforded a perfectly alternating copolymer of butadiene and chloroprene (7/2) via polymerization exclusively through the unsubstituted double bond. 

The molar ratio of the phosphorus ligand to rhodium has pronounced effects on catalyst activity and selectivity. It is well established that increasing the molar ratio of the ligand to the rhodium leads to a higher linear to branched isomer ratio at the... 

This result, caused by the proximity effect between peripheral catalytic sites, can translate into higher or lower catalytic activity of the metallodendrimer in homogeneous catalysis, and is commonly termed the dendritic effect. In the above case, a negative dendritic effect is observed. An interesting example of a positive dendritic effect on catalyst activity was reported by Jacobsen et al. in the hydrolytic kinetic resolution of terminal epoxides by peripherally Co(salen)-substituted PAMAM dendrimers [39]. 

Acetylenes and/or allenes that can be present as impurities in BD have a detrimental effect on catalyst activities. In order to obtain reproducible results these impurities are removed by the pretreatment of the monomer with a catalyst suspension [165,166]. 

Since water is the byproduct, and also has an undesired inhibitory effect on catalyst activity, it must be separated efficiently from the reaction mixture. To achieve this, both conventional reactive distillation and reactive membrane separation are considered as process alternatives. In the latter process, a Knudsen-membrane is applied. Consequently, the mass transfer matrix [/c] has a diagonal structure and the diagonal elements are the Knudsen-selectivities - that is, the square-roots of the ratios of the molecular weights Mr. 

Sulfated catalyst activity was determined with the S02 free feedstream in the absence of water The light-off temperatures reported in Fig 3a for propene oxidation show that sulfation by SO2 induces the same effects on catalyst activity than SO2 in the feedstream in the course of the oxidation reaction (Fig 1b). Thus Pt-Rh catalyst activity is not affected by sulfation while monometallic platinum catalysts are far less active after sulfur storage with 20 ppm SC>2 We must note also that a small inhibiting effect appears after sulfur storage with 4 ppm SO2. 

Since chemical reaction engineering considerations apply to nondcterministic as well as deterministic methods they will be briefly dealt with separately. The interaction of chemical kinetics and transport processes and their effect on catalyst activity and selectivity in reaction networks will be emphasized. Some attention will be also paid to catalyst deactivation. 

Activation energy—Continued effect on reaction rates, 261 hydrogen desorption, 183 use of differences for selectivity control, 260 Active metals content, effect on catalyst activity, 283,285/... 

The liquid phase catalysis of a Diels-Alder reaction hy zeolites Y, EMT, beta and ZSM-5 has heen studied. The use of a silica binder has an effect on catalyst activity and selectivity, depending on catalyst pretreatment. EMT exhibits a higher activity than zeohte Y heta and ZSM-5 offer higher selectivity than Y and EMT. 

The morphology of metal deposition has a profound effect on catalyst activity. If m represents the number of monolayers of coverage, then the catalyst activity under... 

In this set of runs, sample pretreatment seems to have little effect on catalyst activity. All of these pretreatments (H2, CO or syngas) gave comparable long term performance. 

One of the most active noble metal sulfides in hydrotreating reactions is Ir sulfide. Its exceptional activity was reported in HDN of different compounds [8] and in the parallel HDN of pyridine and HDS of thiophene [9,10]. Recently, we found a positive effect of the addition of a small amount of Ir to an Mo/alumina catalyst during HDS and HDN [11]. The aim of this contribution is to focus on some factors during preparation of mixed Ir-Mo sulfide catalysts and to evaluate their effect on catalyst activity. 

Other systems studied are catalyst coke [56,57] and catalyst supports [58-61]. The nature of the support has a profound effect on catalyst activity. Surprisingly, the origin of the carbon, whether peat, wood or coconut shells, is reflected at all length scales from the macroscopic to the atomic level. Carbon blacks of various types and with varying treatments have also been studied [62,64], as has diesel soot [64] and carbon anodes [66-68]. 

Ligand and solvent effects on catalyst activity in propylene oligomerization... 

One of the most interesting results of this approach of using "two-valent" chromium species is the effect on catalyst activity. Yields as high as 16 kg g 1 h 1 were obtained, which was more than twice that of the chromium oxide parent, and many times more than that of the chromium alkyl when deposited on silica. The induction time of chromium oxide was eliminated, and also the declining kinetics profile of the chromium alkyl catalyst. That is, the hybrid catalyst seemed to have incorporated the best aspects of both parents to yield unusually high polymerization activity. 

Thus adjustment of time or of temperature can lead to equivalent effects on catalyst activity and polymer properties. Trading higher temperature for shorter hold time is one way of streamlining the activation cycle and increasing activator output. 

---