Commercial catalyst composition

Kany properties of the catalyst affect the coking rate, including composition metal loading, surface area altimina type, chloride level, and the number of regenerations, A fev limited runs were made to compare coking differences of the three commercial catalyst composition types commonly used, namely, Pt/Al Oj. Ft-Re/Al203, and Ft-Sn/Al203. Results are shown in Table 1 with the factors normalized to the standard Ft catalyst,... 

Single-reaction-step processes have been studied. However, higher selectivity is possible by optimizing catalyst composition and reaction conditions for each of these two steps (40,41). This more efficient utilization of raw material has led to two separate oxidation stages in all commercial faciUties. A two-step continuous process without isolation of the intermediate acrolein was first described by the Toyo Soda Company (42). A mixture of propylene, air, and steam is converted to acrolein in the first reactor. The effluent from the first reactor is then passed directiy to the second reactor where the acrolein is oxidized to acryUc acid. The products are absorbed in water to give about 30—60% aqueous acryUc acid in about 80—85% yield based on propylene. 

Extensive efforts have been made to develop catalyst systems to control the stereochemistry, addition site, and other properties of the final polymers. Among the most prominant ones are transition metal-based catalysts including Ziegler or Ziegler-Natta type catalysts. The metals most frequentiy studied are Ti (203,204), Mo (205), Co (206-208), Cr (206-208), Ni (209,210), V (205), Nd (211-215), and other lanthanides (216). Of these, Ti, Co, and Ni complexes have been used commercially. It has long been recognized that by varying the catalyst compositions, the trans/cis ratio for 1,4-additions can be controlled quite selectively (204). Catalysts have also been developed to control the ratio of 1,4- to 1,2-additions within the polymers (203). 

Composition. The results of elemental analyses are almost always included among the specifications for a commercial catalyst. Depending on the accuracy desired and whether or not the catalyst can be rendered soluble without great difficulty, elemental analysis may be performed by x-ray methods, by one of the procedures based on atomic absorption, or by traditional wet-chemical methods. Erequentiy it is important to determine and report trace element components that may have an effect on catalyst performance. 

Dehydrogenation, Ammoxidation, and Other Heterogeneous Catalysts. Cerium has minor uses in other commercial catalysts (41) where the element s role is probably related to Ce(III)/Ce(IV) chemistry. Styrene is made from ethylbenzene by an alkah-promoted iron oxide-based catalyst. The addition of a few percent of cerium oxide improves this catalyst s activity for styrene formation presumably because of a beneficial interaction between the Fe(II)/Fe(III) and Ce(III)/Ce(IV) redox couples. The ammoxidation of propjiene to produce acrylonitrile is carried out over catalyticaHy active complex molybdates. Cerium, a component of several patented compositions (42), functions as an oxygen and electron transfer through its redox couple. 

Silver-containing catalysts are used exclusively in all commercial ethylene oxide units, although the catalyst composition may vary considerably (129). Nonsdver-based catalysts such as platinum, palladium, chromium, nickel, cobalt, copper ketenide, gold, thorium, and antimony have been investigated, but are only of academic interest (98,130—135). Catalysts using any of the above metals either have very poor selectivities for ethylene oxide production at the conversion levels required for commercial operation, or combust ethylene completely at useful operating temperatures. 

From the catalyst metal and catalyst support studies PNNL settled on a preferred catalyst composition. We joined UOP in a DOE funded program to commercialize the process. A simplified process flow diagram is shown in Figure 34.9. 

Parameters representing the catalyst bed were taken from Briggs et al. (1977,1978) transport coefficients for heat and mass were calculated from well-established correlations, whereas the kinetic parameters came from measurements on Russian catalysts (Ivanov and Balzhinimaev, 1987) of about the same composition as the commercial catalyst used by Briggs. These parameters are collected in Table VI. The model used by Silveston et al. contained, therefore, no adjustable parameters. 

The anchoring and the reduction methods of precious metal precursors influence the particle size, the dispersion and the chemical composition of the catalyst. The results of SEM and H2 chemisorption measurements are summarised in Table 3. The XPS measurements indicate that the catalysts have only metallic Pd phase on their surface. The reduction of catalyst precursor with sodium formate resulted in a catalyst with lower dispersion than the one prepared by hydrogen reduction. The mesoporous carbon supported catalysts were prepared without anchoring agent, this explains why they have much lower dispersion than the commercial catalyst which was prepared in the presence of a spacing and anchoring agent (15). 

In a discussion of catalyst testing procedures, Dowden and Bridger Adv. Catalysis, 9 (669), 1957] have reported the effect of particle size and mass velocity on the rate of oxidation of S02 to S03. They studied this reaction at 400 and at 470 °C using commercial catalyst pellets (5.88 mm diameter) and two sizes of crushed pellets (2.36 and 1.14 mm diameter). In all runs the feedstream composition was kept constant. 

The screening of carriers, catalyst composition, particle sizes and shapes showed indeed, that a much more active catalyst could be made with Cs as a secondary promoter for the beds downstream the intermediate absorption tower. The best candidates were selected, and some m3 of each recipe were produced as 9-mm and 12-mm Daisy extrudates in a successful commercial-scale test production. The activities were as expected from the previous development work, and a 30 day activity test also confirmed it to be stable during this period. 

High Temperature Operation of the PEMFC The first generation of commercial PEMFCs will use presently known components, consisting of a perfluorosulfonic acid membrane as electrolyte and catalyst compositions as cited above. The electrolyte determines that the fuel cell needs to be operated at fully humidified conditions and limits the operating temperature to 80-90 °C. 

In addition to modification of surfaces by non-metals, the catalytic properties of metals can also be altered greatly by the addition of a second transition metaP ". Interest in bimetallic catalysts has arisen steadily over the years because of the commercial success of these systems. This success results from an enhanced ability to control the catalytic activity and selectivity by tailoring the catalyst composition . A long-standing question regarding such bimetallic systems is the nature of the properties of the mixed-metal system which give rise to its enhanced catalytic performance relative to either of its individual metal components. These enhanced properties (improved stability, selectivity and/or activity) can be accounted for by one or more of several possibilities. First, the addition of one metal to a second may lead to an electronic modification of either or both of the metal constituents. This... 

Secondly, we began research and development based on our own knowledge and experience with commercial catalyst manufacture and compositions. We also drew on many years of personal experience directing catalyst research and development, as well as our own speculations as to what properties might be most important. 

The other commercialized pentane isomerization process is that of the Standard Oil Co. (Indiana) (20). This process differs from the Indiana-Texas butane process in that the aluminum chloride is introduced as a slurry directly to the reactor and that about 0.5% by volume of benzene is added continuously in the feed to suppress side reactions. Temperature, catalyst composition, space velocity, and hydrogen chloride concentration are generally similar to those in the corresponding butane process, but the reactor pressure is about 100 pounds lower. The Pan American Refining Co. operated the Indiana pentane isomerization process commercially during the last nine months of the war and produced about 400 barrels of isopentane per calendar day. 

Having established reliable values for all of the important rate constants as a function of alkyl substitution on dibenzothiophenes, it is now possible to examine critically how these rate constants (and associated changes in product selectivity) are affected by other components of commercial gas oils and by the H2S that is produced during the HDS process. It is also possible to evaluate how these various rate constants are affected by changes in catalyst composition and by process conditions. Knowledge of the details of these effects can lead to novel catalyst modifications and process configurations that may be able to reach the new stricter standards of 0.05% S. These topics are discussed in later sections. However, for perspective, we will first summarize what is known about present-day catalyst compositions and catalytic mechanisms that bring about the transformations observed in HDS processes. 

The synthesis of polyoctenamer has been commercialized by Huels.150 In contrast with the transformation of cyclooctene to 1,9-decadiene [Eq. (12.31)], homogeneous catalyst compositions, such as WClg + EtAlCl2, are used to promote ring-opening metathesis polymerization of cyclooctene. A polymer of narrow molecular-weight distribution with high trans content (55-85%) called Vestenamer is produced and used as blend component in different rubbers and thermoplastics. 

During the history of a half century from the first discovery of the reaction (/) and 35 years after the industrialization (2-4), these catalytic reactions, so-called allylic oxidations of lower olefins (Table I), have been improved year by year. Drastic changes have been introduced to the catalyst composition and preparation as well as to the reaction process. As a result, the total yield of acrylic acid from propylene reaches more than 90% under industrial conditions and the single pass yield of acrylonitrile also exceeds 80% in the commercial plants. The practical catalysts employed in the commercial plants consist of complicated multicomponent metal oxide systems including bismuth molybdate or iron antimonate as the main component. These modern catalyst systems show much higher activity and selectivity... 

The catalyst composition in Fiberite 934 and Hercules 3501 prepregs was investigated by 19F NMR. The epoxy resin in these commercial C-fiber/TGDDM-DDS prepregs was dissolved in DMSO. 

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