Oxidant catalyst development

Benzoraffln A hydrofining process for treating naphtha fractions derived from coal. It is a fixed-bed, gas-phase process using a cobalt/molybdenum oxide catalyst. Developed jointly by BASF, Veba-Chemie, and Lurgi, Ground 1960. 

Ionic liquids based on imidazolium cations and either [BF4]- or [PF6] anions have been used to immobilize transition metal based oxidation catalysts developed... 

Surprisingly perhaps, oxidation of C3 and C4 olefins over bismuth oxide alone leads mainly to oxidative dimerization to Cg or Cg dienes, and small amounts of cyclic hydrocarbons. The surface is possibly highly reduced, providing many Lewis acid centres for olefin coordination but few oxide ions for hydrogen abstraction and transfer. (The supported gallium oxide catalyst, developed by BP, leads to further hydrogen abstractions and significant yields of aromatics from lower olefins). 

The high-pressure process relied on large and complex plants that required careful process control. Therefore, the discovery in 1953 of the appropriate catalysts that allowed the process to be carried under low pressure ( 500 psi) was welcomed by the industry [7]. Three types of catalysts were developed about that time the Ziegler-type catalysts typically obtained by reacting alkyl aluminum compounds with titanium chloride metal oxide catalyst systems, developed by Phillips Petroleum in the United States, typically made of chromium oxide supported on a silicaceous carrier [8]) and a different type of oxide catalyst developed by Standard Oil Company. The first plants based on the Ziegler catalyst went on line in Germany by 1955 and a plant based on the Phillips catalyst in Texas opened in 1957. The third catalyst system developed much slower and was picked up by the Japanese plastics industry in a plant opened in 1961. 

Table 11.1. Selective oxidation catalysts developed at SABIC company.

Further improvement of selectivity to acrylonitrile has been achieved by cofeeding CO2. According to the data reported in the Mamedov patent, increasing the CO2 percentage in the feed from 0 to 40 enhanced selectivity to acrylonitrile on the WVSbAl oxide catalyst from 60 to 72%. The positive effect of CO2 was reversible and catalyst specific. For instance, in the presence of CO2 selectivity of the WVSbMg oxide catalyst improved by 8%, while the selectivity of the VSbSnTi oxide catalyst developed by BP Chemical increased by only 2%. 

Several multicomponent metal oxide catalysts, developed for this process, have achieved excellent product selectivity with a high conversion of propene Mo-Bi-Fe-Co-M-K-O (M = V or W) used for the first step can attain >90% acrolein yields [6,7] while for the second step Mo-V-Cu-based oxides can lead to >97% acrylic acid yields [8,9], giving, in theory, an overall acrylic acid yield from propene of 87%. In addition to the compositional differences in fhe catalysis for the two-step process, there is also a difference in the optimal reaction temperatures 320-330°C for the first step and 210-255°C for the second step. One has to keep in mind that propene and oxygen can form an explosive mixture and therefore, certain limitations in the feed composition (propene oxygen (air) steam) exist. In addition, the acrylic acid easily dimerises at temperatures above 90 C, meaning that the reactor effluent should be quickly quenched after the second catalyst bed to temperatures below this critical value. 

Processes have been developed whereby the oxygen is suppHed from the crystal lattice of a metal-oxide catalyst (5) (see Acrylonitrile Methacrylic acid AND derivatives). 

The Reaction. Acrolein has been produced commercially since 1938. The first commercial processes were based on the vapor-phase condensation of acetaldehyde and formaldehyde (1). In the 1940s a series of catalyst developments based on cuprous oxide and cupric selenites led to a vapor-phase propylene oxidation route to acrolein (7,8). In 1959 Shell was the first to commercialize this propylene oxidation to acrolein process. These early propylene oxidation catalysts were capable of only low per pass propylene conversions (ca 15%) and therefore required significant recycle of unreacted propylene (9—11). 

Manufacture and Processing. Until World War II, phthaUc acid and, later, phthaUc anhydride, were manufactured primarily by Hquid-phase oxidation of suitable feedstocks. The favored method was BASF s oxidation of naphthalene [91-20-3] by sulfuric acid ia the presence of mercury salts to form the anhydride. This process was patented ia 1896. During World War I, a process to make phthaUc anhydride by the oxidation of naphthalene ia the vapor phase over a vanadium and molybdenum oxide catalyst was developed ia the United States (5). Essentially the same process was developed iadependendy ia Germany, with U.S. patents being granted ia 1930 and 1934 (6,7). 

These catalysts contained promoters to minimise SO2 oxidation. Second-generation systems are based on a combined oxidation catalyst and particulate trap to remove HC and CO, and to alleviate particulate emissions on a continuous basis. The next phase will be the development of advanced catalysts for NO removal under oxidising conditions. Low or 2ero sulfur diesel fuel will be an advantage in overall system development. 

Ethylene oxide (qv) was once produced by the chlorohydrin process, but this process was slowly abandoned starting in 1937 when Union Carbide Corp. developed and commercialized the silver-catalyzed air oxidation of ethylene process patented in 1931 (67). Union Carbide Corp. is stiU. the world s largest ethylene oxide producer, but most other manufacturers Hcense either the Shell or Scientific Design process. Shell has the dominant patent position in ethylene oxide catalysts, which is the result of the development of highly effective methods of silver deposition on alumina (29), and the discovery of the importance of estabUshing precise parts per million levels of the higher alkaU metal elements on the catalyst surface (68). The most recent patents describe the addition of trace amounts of rhenium and various Group (VI) elements (69). 

Ethylene oxide is produced in large, multitubular reactors cooled by pressurized boiling Hquids, eg, kerosene and water. Up to 100 metric tons of catalyst may be used in a plant. Typical feed stream contains about 30% ethylene, 7—9% oxygen, 5—7% carbon dioxide the balance is diluent plus 2—5 ppmw of a halogenated moderator. Typical reactor temperatures are in the range 230—300°C. Most producers use newer versions of the Shell cesium-promoted silver on alumina catalyst developed in the mid-1970s. 

Liquefaction. Liquefaction of coal to oil was first accompHshed in 1914. Hydrogen was placed with a paste of coal, heavy oil, and a small amount of iron oxide catalyst at 450° and 20 MPa (200 atm) in stirred autoclaves. This process was developed by the I. G. Earbenindustrie AG to give commercial quaUty gasoline as the principal product. Twelve hydrogenation plants were operated during World War II to make Hquid fuels (see CoAL... 

Catalytic Pyrolysis. This should not be confused with fluid catalytic cracking, which is used in petroleum refining (see Catalysts, regeneration). Catalytic pyrolysis is aimed at producing primarily ethylene. There are many patents and research articles covering the last 20 years (84—89). Catalytic research until 1988 has been summarized (86). Almost all catalysts produce higher amounts of CO and CO2 than normally obtained with conventional pyrolysis. This indicates that the water gas reaction is also very active with these catalysts, and usually this leads to some deterioration of the olefin yield. Significant amounts of coke have been found in these catalysts, and thus there is a further reduction in olefin yield with on-stream time. Most of these catalysts are based on low surface area alumina catalysts (86). A notable exception is the catalyst developed in the former USSR (89). This catalyst primarily contains vanadium as the active material on pumice (89), and is claimed to produce low levels of carbon oxides. 

Catalytic Unit. The catalytic unit consists of an activated coating layer spread uniformly on a monolithic substrate. The catalyst predominantly used in the United States and Canada is known as the three-way conversion (TWC) catalyst, because it destroys aU three types of regulated poUutants HC, CO, and NO. Between 1975 and the early 1980s, an oxidation catalyst was used. Its use declined with the development of the TWC catalyst. The TWC catalytic efficiency is shown in Figure 5. At temperatures of >300° C a TWC destroys HC, CO, and NO effectively when the air/fuel mixture is close to... 

Emission control systems for two-stroke engines depend heavily on an efficient oxidation catalyst. These may be based on Pt and/or Pd. Higher lube oil consumption characteristics of two-stroke engines may result in modification to the lube oil or require the development of oxidation catalysts more resistant to lube oil ash compounds. 

Kelkar and McCarthy (1995) proposed another method to use the feedforward experiments to develop a kinetic model in a CSTR. An initial experimental design is augmented in a stepwise manner with additional experiments until a satisfactory model is developed. For augmenting data, experiments are selected in a way to increase the determinant of the correlation matrix. The method is demonstrated on kinetic model development for the aldol condensation of acetone over a mixed oxide catalyst. 

The process which was developed hy DOW involves cyclodimerization of hutadiene over a proprietary copper-loaded zeolite catalyst at moderate temperature and pressure (100°C and 250 psig). To increase the yield, the cyclodimerization step takes place in a liquid phase process over the catalyst. Selectivity for vinylcyclohexene (VCH) was over 99%. In the second step VCH is oxidized with oxygen over a proprietary oxide catalyst in presence of steam. Conversion over 90% and selectivity to styrene of 92% could he achieved. ... 

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