Catalysts Formulations

Future Methanol Processes. The process route for methanol synthesis has remained basically unchanged since its inception by BASF in 1923. The principal developments have been in catalyst formulation to increase productivity and selectivity, and in process plant integration to improve output and energy efficiency while decreasing capital cost. 

Process water streams from vinyl chloride manufacture are typically steam-stripped to remove volatile organics, neutralized, and then treated in an activated sludge system to remove any nonvolatile organics. If fluidized-bed oxychlorination is used, the process wastewater may also contain suspended catalyst fines and dissolved metals. The former can easily be removed by sedimentation, and the latter by precipitation. Depending on the specific catalyst formulation and outfall limitations, tertiary treatment may be needed to reduce dissolved metals to acceptable levels. 

Over the years, HteraHy thousands of catalyst formulations have been evaluated and those available today are significantly more active, which has allowed considerable improvement in productivity and plant operation. Today, a typical catalyst contains approximately 93 wt % Fe O, and about 1 wt % potassium oxide, 3 wt % alumina, 3 wt % calcium oxide, and 0.5 wt % siHca, which is actually an unnecessary impurity. 

The most popular SCR catalyst formulations are those that were developed in Japan in the late 1970s comprised of base metal oxides such as vanadium pentoxide [1314-62-1J, V20, supported on titanium dioxide [13463-67-7] Ti02 (1). As for low temperature catalysts, NO conversion rises with increasing temperatures to a plateau and then falls as ammonia oxidation begins to dominate the SCR reaction. However, peak conversion occurs in the temperature range between 300 and 450°C, and the fah-off in NO conversion is more gradual than for low temperature catalysis (44). 

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. 

In the late 1980s, however, the discovery of a noble metal catalyst that could tolerate and destroy halogenated hydrocarbons such as methyl bromide in a fixed-bed system was reported (52,53). The products of the reaction were water, carbon dioxide, hydrogen bromide, and bromine. Generally, a scmbber would be needed to prevent downstream equipment corrosion. However, if the focus of the control is the VOCs and the CO rather than the methyl bromide, a modified catalyst formulation can be used that is able to tolerate the methyl bromide, but not destroy it. In this case the methyl bromide passes through the bed unaffected, and designing the system to avoid downstream effects is not necessary. Destmction efficiencies of hydrocarbons and CO of better than 95% have been reported, and methyl bromide destmctions between 0 and 85% (52). 

The catalyst used for these studies was one that had been rejected by laboratory short tubular reactor experiments as a hotspot-type catalyst. This same type was recommended by another corporate lab with experience in catalyst formulations. The hotspot-type catalyst gave 3-... 

Performance of an FCC unit is often maximized when the unit is operated against multiple constraints simultaneously. It is essential that the specified constraints allow for minimum comfort zones. An operator-friendly advanced control program, coupled with proper selection of catalyst formulation, would allow optimizing the performance of the unit on a daily basis. 

Future catalyst formulation will be customized to meet the individual refiner s needs. Catalyst manufacturers will be tailoring catalysts to meet each refiner s requirements. 

The chapter by Bridger and Woodward deals with methanation as a means for removing carbon oxides from ammonia synthesis gas. This technology, together with earlier pioneer work by Dent and co-workers (I), are the forerunners of all modern methanation developments. The chapter deals with catalyst formulation and characterization and with the performance of these catalysts in commercial plants as a function of time on-stream. 

L. Winsor (Bechtel Associates Professional Corp.) Can carbon lay-down be avoided dependably by catalyst formulation ... 

Solutions to these problems require improved catalyst formulations and the development of altanative processes. Howeva most reactions satisfyhig these objectives are very diflScult to achieve... 

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. 

The present study was initiated to understand the causes of large differences in perfonnance of various catalyst formulations after accelerated thermal aging on an engine dynamometer. In particular, we wished to determine whether performance charaderistics were related to noble metal dispersion (i.e. noble metal surface area), as previous studies have suggested that the thermal durability of alumina-supported Pd catalysts is due to high-temperature spreading or re-dispersion of Pd particles [20-25]. 

At higher reaction temperatures (>300°C), micro- or meso-porous materials and/or oxides containing transition metals are preferable. The performances are considerably dependent on the type of reductant, besides the characteristics of the catalyst and the type of transition metal. Although all possible combinations have been explored, including the usage of high-throughput methods, identification of a suitable catalyst formulation active in HC-SCR under practical conditions, especially to decrease by more than... 

However, some areas of future research need to be highlighted (1) noble metal-based formulations which do not form N20, (2) novel catalyst formulations which decompose/reduce N20 below 300°C, (3) on-board routes to form oxygenated reductants, (4) NTP technologies, (5) maintain catalyst within peak operating temperature window and (6) techniques for storing NO, emissions during cool exhaust conditions followed by re-injection of the stored NO when the catalyst has achieved light-off conditions. There is already an active research on these topics, but a further intensification would be necessary. 

Very seldom does an industrial catalyst consist of a single chemical compound or metallic element. Most often a catalyst formulation consists of a multitude of components, each of which performs an essential task in the creation of a commercially viable catalyst. Figure 6.7,... 

Through the years, several catalyst formulations have been employed, but one of the traditional catalytic agents has been vanadium pentoxide. Calderbank (114) has indicated that for a catalyst consisting of V205 supported on silica gel, the kinetic data are represented by a rate expression of the form... 

In recent years, considerable research effort has been invested in trying to develop an oxidative process to accomplish the desired transformation. Several catalyst formulations with good selectivities for the desired reaction have been developed, and you are asked to determine the desirability of using one of these formulations in a fixed bed reactor configuration. Several advantages are claimed for the oxidative processes ... 

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