Heterogeneous copper

Interest in the hydrocyanation of nonactivated olefins with nickel catalysts arose from the discovery that finely divided nickel or nickel cyanide on inert supports gives higher yields of nitrile products at less severe reaction conditions than do cobdt or copper heterogeneous catalysts. ... 

Mitsui Toatsu Chemical, Inc. disclosed a similar process usiag Raney copper (74) shortiy after the discovery at Dow, and BASF came out with a variation of the copper catalyst ia 1974 (75). Siace 1971 several hundred patents have shown modifications and improvements to this technology, both homogeneous and heterogeneous, and reviews of these processes have been pubHshed (76). Nalco Chemical Company has patented a process based essentially on Raney copper catalyst (77) ia both slurry and fixed-bed reactors and produces acrylamide monomer mainly for internal uses. Other producers ia Europe, besides Dow and American Cyanamid, iaclude AUied CoUoids and Stockhausen, who are beheved to use processes similar to the Raney copper technology of Mitsui Toatsu, and all have captive uses. Acrylamide is also produced ia large quantities ia Japan. Mitsui Toatsu and Mitsubishi are the largest producers, and both are beheved to use Raney copper catalysts ia a fixed bed reactor and to sell iato the merchant market. 

Pyrrohdinone can be alkylated by reaction with an alkyl haUde or sulfate and an alkaline acid acceptor (63,64). This reaction can be advantageously carried out with a phase-transfer catalyst (65). Alkylation can also be accompHshed with alcohols and either copper chromite or heterogenous acid catalysts... 

The reaction is cataly2ed by all but the weakest acids. In the dehydration of ethanol over heterogeneous catalysts, such as alumina (342—346), ether is the main product below 260°C at higher temperatures both ether and ethylene are produced. Other catalysts used include siUca—alumina (347,348), copper sulfate, tin chloride, manganous chloride, aluminum chloride, chrome alum, and chromium sulfate (349,350). 

Heterogeneous nucleation is most likely to occur when there is a strong tendency for the crystal to stick to the surface of the catalyst. This sticking tendency can be described by the angle of contact, 6, shown in Fig. 7.3 the smaller 6, the better the adhesion. Anyone who has tried to get electronic solder to stick to a strip of copper will understand this well. If the copper is tarnished the solder will just roll around as a molten blob with 6 = 180°, and will not stick to the surface at all. If the tarnished... 

The phase rule is a mathematical expression that describes the behavior of chemical systems in equilibrium. A chemical system is any combination of chemical substances. The substances exist as gas, liquid, or solid phases. The phase rule applies only to systems, called heterogeneous systems, in which two or more distinct phases are in equilibrium. A system cannot contain more than one gas phase, but can contain any number of liquid and solid phases. An alloy of copper and nickel, for example, contains two solid phases. The rule makes possible the simple correlation of very large quantities of physical data and limited prediction of the behavior of chemical systems. It is used particularly in alloy preparation, in chemical engineering, and in geology. 

A low-pressure process has been developed by ICl operating at about 50 atm (700 psi) using a new active copper-based catalyst at 240°C. The synthesis reaction occurs over a bed of heterogeneous catalyst arranged in either sequential adiabatic beds or placed within heat transfer tubes. The reaction is limited by equilibrium, and methanol concentration at the converter s exit rarely exceeds 7%. The converter effluent is cooled to 40°C to condense product methanol, and the unreacted gases are recycled. Crude methanol from the separator contains water and low levels of by-products, which are removed using a two-column distillation system. Figure 5-5 shows the ICl methanol synthesis process. 

A heterogeneous mixture of copper sulfate crystals (blue) and saud. 

Two mixtures. On the left is brass, a homogeneous mixture of copper and zinc. On the right is a piece of granite, a heterogeneous mixture that contains discrete regions of different minerals (feldspar, mica, and quartz). 

The situation has now changed and currently an area of considerable research interest is in heterogenizing homogeneous catalysts. One such instance is to be found in the ethylene based manufacture of vinyl acetate (11). A homogeneous catalytic process based on palladium and copper salts was first devised, but corrosion problems were made much less serious in a heterogeneous system based on the same chemical principles. 

On the basis of information on the properties of the nickel-hydrogen and nickel-copper-hydrogen systems available in 1966 studies on the catalytic activity of nickel hydride as compared with nickel itself were undertaken. As test reactions the heterogeneous recombination of atomic hydrogen, the para-ortho conversion of hydrogen, and the hydrogenation of ethylene were chosen. 

The temperature behavior of the alloy catalysts in the heterogeneous recombination of hydrogen atoms was different for rich in nickel alloys from one side and for rich in copper from the other. For the three alloy catalyst films, i.e. Ni97Cu3, Ni77Cu23, and Ni57Cu43 (numbers represent... 

On the basis of the related experimental evidence and its discussion one can regard the poisoning effect of the hydride hydrogen in nickel and its alloys with copper as normally accompanying the heterogeneous recombination of hydrogen atoms on these catalysts at lower temperatures. 

Copper oxide, oxidation of CO over, 86 Coupled heterogeneous catalytic reactions, kinetics of, 1-49, see also Kinetics coupling through catalytic surface, 9-13 experimental studies, 22-49 apparatus and procedure, 25, 26 catalysts, 26-28... 

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