Heteroatom poisoning

Hydrotreated naphthas (combined) were then reformed over a 0.6% Pt on A1203 catalyst at 500°C, 500 psig, 3 LHSV, and 5 M scf H2/bbl. This simple catalyst was chosen in preference to the more advanced bi- and trimetallic catalysts because of its probably lower sensitivity to heteroatom poisoning. The reformates were analyzed by gas chromatography... 

Heteroatoms nitrogen, oxygen, sulfur, and metals) are found in every crude oil, and the concentrations have to be reduced to convert the oil to transportation fuel. This is caused by the fact that if nitrogen and sulfur are present in the final fuel during combustion, nitrogen oxides (NO ) and sulfur oxides (SO ) form, respectively. In addition, metals affect many upgrading processes adversely, poisoning... 

M02C.4 Metal carbide catalysts have the additional advantage of displaying high tolerance towards poisoning, and effectiveness in heteroatom removal.6 Both the technological applications of early transition metal carbides and the physical properties underlying their correspondence to the precious metals are under study. 

There is still a lack of acidic poisons and the search for suitable and unreactive acidic compounds is strongly needed. Furthermore, the study of the chemisorp-tive behavior of bifunctional molecules, such as diketones, diamines, and cyclic compounds such as diazines (400), with two heteroatoms in varying relative orientations seems to be promising, since such compounds may shed some light on the configurations of exposed cations and on their geometric arrangements in the exposed crystal faces. 

Propynylnaphthalene 15 furnishes dinaphthylacetylene 20 in near quantitative yield. On the other hand, the Mori system performs somewhat less well if heteroatoms are present in the substrates, suggesting that the catalytic system is poisoned by the presence of the heteroatom through complexation and/or chelation of the active molybdenum center. Cyano groups and bromides/iodides inhibit the reactivity of the catalyst system. However, both propynylated phenols (16) and esters (17) give satisfactory dimerization results (21, 22). 

Consistent with the fact that thiophene is a poison in metal-catalyzed hydrogenation reactions, thiophene is deuterated only slowly on the prereduced transition metals listed in Table XII, except for iridium. In both hydrogenation115 and exchange89 the poisoning has been attributed to the influence of the heteroatom in the adsorption process, presumably as species (30), or even of elemental sulfur as a consequence... 

Despite the fact that polar entities are catalyst poisons, a variety of acyclic olefins containing a heteroatom functional group can undergo metathesis in the presence of a suitable catalyst, although at a high catalyst level. These include unsaturated esters, ethers, ketones, amines, nitriles, halogens, etc. [14]. In particular metathesis reactions - including ethenolysis - of unsaturated fatty esters and fatty oils are of interest, as they have perspectives for the oleochemical industry [15]. 

If the metal cation is too electrophilic, CO coordination will be too strong, possibly by coordination via its oxygen atom, and CO will act as a poison rather than participating in the polymerization [40], The moderate electrophilicity of Pd" catalysts makes them tolerant also to a variety of heteroatom functionalities in the olefin substrate. In this respect, polyketone catalysis can have a wider applicability than early transition metal catalysis of polyolefins, which is highly intolerant of functional groups. 

The various factors that can contribute to deactivation of iron Fischer-Tropsch (FT) catalysts include transformation of the active phase into an inactive constituent, poisoning by carbonaceous species and heteroatoms, and loss of active phase surface area. Progress in elucidating the causes of deactivation is hampered by the inability to conclusively identify the active phase in iron FT catalysts. In recent work involving doubly promoted, unsupported iron catalysts, the sequence of phase transformations shown in Figure 1 that take the catalyst from its as-prepared hematite phase to iron carbide [1,2] was postulated. 

It is the polynuclear aromatic system and the heteroatom species that pose the greatest limitation to resid conversion. The polynuclear aromatic and heteroatom species 1) have high thermal stability 2) poison catalysts by deposition of heteroatoms and metals and 3) readily form coke that deposits on the catalyst and detracts from liquid production. 

The x-ray fluorescence analysis is used by crude oil chemists as an express method for the determination of the metal contents in crude oil and its products. This is very important because the metals in crude oil are poisons for cracking catalysts, and are also undesired in the fuels, since they lead to environmental pollution. All the elements with atomic number greater than eleven in the periodic table can be analyzed by x-ray fluorescence spectrometry. An important task of this method in crude oil chemistry is the determination of heteroatoms such as sulfur, oxygen, and nitrogen. Frequently, x-ray fluorescence spectrometry is used to verify the presence of certain additives in oils. 

Furthermore, to avoid catalyst poisoning or reduction in catalyst activity, it is essential that as much nitrogen and heavy metals as possible are removed from the feedstock. It has been shown [9] that a greater part of the heteroatoms (nitrogen, oxygen and sulfur) and the heavy metals are contained in or associated with asphaltenes. It is necessary for the cracking processes that asphaltenes are removed from the cracking feedstock. 

The palladium-catalyzed amination of heteroaromatic halides, or the arylation of heteroaromatic containing amines, is complicated by the Lewis basicity of the heteroatom. The heterocycle may thus act as a ligand for palladium and cause catalyst inhibition and/or poisoning. R. Dommisse demonstrated that by using excess K2CO3 with the Pd/BINAP or L5 catalyst system, a series of pyridyl chlorides could be efficiently aminated by either anilines or aminopyridines.63... 

Coordination polymerization involves the use of transition metal catalysts. Examples are Ziegler-Natta polymerization by Tl/Al systems, metallocene polymerization with Ti, Zr, Hf catalysts, or metathesis polymerization with W, Mo, Re metals. Synthesis of functional polymers by organometallic catalysts are particularly difficult because transition metds are not only l ed by protic functionality, they are often poisoned by heteroatoms (e.g. N, O). 

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