Catalysts formulation additives

Catalyst contamination from sources such as turbine lubricant and boiler feed water additives is usuaUy much more severe than deactivation by sulfur compounds in the turbine exhaust. Catalyst formulation can be adjusted to improve poison tolerance, but no catalyst is immune to a contaminant that coats its surface and prevents access of CO to the active sites. Between 1986 and 1990 over 25 commercial CO oxidation catalyst systems operated on gas turbine cogeneration systems, meeting both CO conversion (40 to 90%) and pressure drop requirements. 

Consider reformulating the catalyst—custom formulations are available. Increasing rare-earth content can reduce the wet gas rate. Catalyst is usually selected for properties other than its ability to flow. However, if it does not flow, it is not going to work well. Catalyst physical properties should be compared with those of catalysts that have circulated well. Evaluate the economics of using metal passivation additives and other catalyst enhancing additives. 

One promising extension of this approach Is surface modification by additives and their Influence on reaction kinetics. Catalyst activity and stability under process conditions can be dramatically affected by Impurities In the feed streams ( ). Impurities (promoters) are often added to the feed Intentionally In order to selectively enhance a particular reaction channel (.9) as well as to Increase the catalyst s resistance to poisons. The selectivity and/or poison tolerance of a catalyst can often times be Improved by alloying with other metals (8,10). Although the effects of Impurities or of alloying are well recognized In catalyst formulation and utilization, little Is known about the fundamental mechanisms by which these surface modifications alter catalytic chemistry. 

An important class of industrial catalysts consists of an active component dispersed in the form of very small particles over high surface area solids. As the field of industrial heterogeneous catalysis has developed, catalyst formulations have evolved such that state-of-the-art catalysts often contain two or more metals and/or main group elements. The additives may promote a desired reaction, prevent undesirable side reactions, or enhance catalyst longevity.Bimetallic nanoparticle catalysts in particular are widely... 

How to Solve the Deactivation Problem. Solutions to the deactivation problem are difficult. The patent literature (42) has claims that either sodium, manganese or phosphorous added to alumina prevents deactivation by silica. In addition, removal of matrix silica from cracking catalyst formulations should prevent further deactivation because zeolitic silica, as we have shown, migrates more slowly. There is at least one patent relating to very high alumina matrix cracking catalysts (43). Another solution is to use more active SOx catalysts such as magnesia-based materials. 

The ATR of glycerol has also been examined over Pt- and Rh-based catalysts supported on alumina foams [298]. High selectivity to H2 can be achieved by adjusting the fuel-to-air and fuel-to-steam feed ratios, and also the catalyst formulation. The addition of ceria to AI2O3 provides a catalyst vhich shows high fuel conversion and high selectivity to H2. 

Alternative catalyst formulations for methane ATR based on bimetallic catalysts have been studied, aiming at increasing the activity of nickel catalysts by the addition of low contents of noble metals. 

Many available catalyst additives that can be used to meet a specific objective are listed in Table 6.2. These have become a necessary adjunct to FCC operations. Originally, catalyst suppliers tried to incorporate the function into the catalyst but a myriad of needs or the catalyst manufacturing scheme employed made a single all-encompassing catalyst formulation impossible. 

The iodide content of the catalyst formulation is the key to avoiding these problems of competing reactions and achieving maximum acetic acid selectivity. The addition of iodide ensures that any initially formed methanol (7) is rapidly (H) converted to the more electrophilic methyl iodide. However, further increases in the quantities of iodide beyond that needed for methanol conversion to methyl iodide may lead to a portion, or all, of the catalytic-ally active cobalt carbonyl reverting to catalytically inactive cobalt iodide species - e.g. the [Col4] anion identified in this work, or possibly the cationic [Co(MeOH) (CO) I species (9). 

The aim of this review paper is to give an extensive overview of the different promoters used to develop new or improved Co-based F-T catalysts. Special attention is directed towards a more fundamental understanding of the effect of the different promoter elements on the catalytically active Co particles. Due to the extensive open and patent literature, we have mainly included research publications of the last two decades in our review paper.In addition, we will limit ourselves to catalyst formulations composed of oxide supports, excluding the use of other interesting and promising support materials, such as, e.g., carbon nanofibers studied by the group of de Jong. ... 

Haldor Tops e have described a number of sulphur resistant catalyst formulations.131 132 For example, metals of Groups VB or VIB with Fe, Co, or Ni on a porous ceramic (A1203 or Ti02) as support can give gases containing large amounts of hydrocarbons in addition to methane in the... 

In an age of increasing environmental concerns, many of the tools that formulators had utilized in the past are no longer acceptable. Use of solvents has been drastically curtailed. Plasticizers must often be used in limited amounts. Regional regulations place demands that total VOC emissions be kept to a minimum. Certain catalysts and additives are discouraged because of safety or health issues. 

There are also catalyst formulations which have highly dispersed metals which are deliberately heterogeneously distributed on a support. If the microscopist is aware of the situation, he can take precautions in the sample preparation. This type of sample is the worst possible case to analyze because not only does the analyst have a complex mixture of components to sort out, but the analysis statistics are very poor. Consequently, additional time is usually required to survey the catalyst particles in order to establish a consensus of how it was constructed. Specialized specimen preparation such as ultramicrotoming and scraping the exterior of a sphere or extrudate may alleviate some of the interpretation problems. Additional aid may be solicited from a scanning electron microscope wherein an elemental distribution of a polished cross section of the catalyst sphere or extrudate can be made. 

Alcoa s rehydratable CP alumina powders can be used effectively to improve a viable FCC catalyst formulation. Well-formed microspheres which have superior attrition resistance can be fabricated by controlling the pH and viscosity of the FCC slurry. At this time, the preferred formulation uses CP-2 as the free alumina source and a silica sol which has aged at conditions conducive to the formation of chains of polysilicic acid aggregates. The addition of the rehydratable alumina can also have a beneficial effect on the cracking activity of the catalyst. The conversion and selectivity of a CP-2 formulated sample were comparable to a commercial grade catalyst and an experimental reference, which was alumina-free. After heavy metals poisoning, the CP-2 material had activity which was superior to the reference formulation. 

The advantages of phosphorus addition to catalyst formulations found in patents can be approximately categorized as follows (i) optimization of the catalyst pore structure by addition of phosphorus to be applied with certain types of feedstocks such as residual oil, (ii) optimization of the dispersion of Co(Ni) I Mo-containing phases by the presence of phosphorus, (iii) optimization of synergistic effects resulting from complex chemical combinations of phosphorus and other incorporated elements, (iv) optimization of catalyst preparation by use of specific phosphorus precursors, and (v) the use of phosphorus-containing catalysts under specific reaction conditions or processes as well as their use in combination with other hydrotreating catalysts. 

Typical metallic monoliths in use today, illustrated in Fig. 10, have cell densities in the range 15-78 cells cm (100-500 cells inch ), corresponding to individual cell dimensions of 1.1-2.5 mm. To minimize additional back pressure due to the catalyst formulation, it is essential that the eoating be applied in a controlled manner. It is difficult to define a typical thickness of the catalyst layer (often referred to as washcoat layer ), since this inevitably differs from one catalyst manufacturer to another, depending upon the precise processing techniques used and the application for the finished catalyst. However, usually it is about as thick as the metal foil, typically 0.04-0.05 mm. 

The most common catalyst, the so-called COC (conventional oxidation catalyst), was based on platinum and palladium on an alumina support. However, as legislation tightened further, it became necessary to control the NO emissions also. This brought two further requirements closer control around the stoichiometnc air-fuel ratio, and the addition of a further catalytic metallic component, rhodium, to the catalyst formulation to enable the NOx to selectively reduced to nitrogen, as in Eqs (6) and (7). 

As with alumina, ceria has several roles to play within the catalyst formulation. It has some effect on stabilizing alumina surface area at high temperatures, and it is also capable of stabilizing the dispersion of platinum in these systems, important because the effect is particularly marked in the 600-800°C region, where many present-day catalysts operate. In addition, ceria allows two other more directly performance-related phenomena to take place oxygen storage and the water gas shift reaction shown in Eq. (9) ... 

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