Acetylene, continuous catalytic conversion

Acetaldehyde decomposition, reaction pathway control, 14-15 Acetylene, continuous catalytic conversion over metal-modified shape-selective zeolite catalyst, 355-370 Acid-catalyzed shape selectivity in zeolites primary shape selectivity, 209-211 secondary shape selectivity, 211-213 Acid molecular sieves, reactions of m-diisopropylbenzene, 222-230 Activation of C-H, C-C, and C-0 bonds of oxygenates on Rh(l 11) bond-activation sequences, 350-353 divergence of alcohol and aldehyde decarbonylation pathways, 347-351 experimental procedure, 347 Additives, selectivity, 7,8r Adsorption of benzene on NaX and NaY zeolites, homogeneous, See Homogeneous adsorption of benzene on NaX and NaY zeolites... 

Continuous Catalytic Conversion of Acetylene to Higher Hydrocarbons over a Metal Modified Shape Selective Zeolite Catalyst... 

In the original German process acetylene is injected into an aqueous solution of mercuric sulfate acidified with sulfuric acid at 90-95°C and about 1-2 atm. As a result of side reactions, the catalytically active mercury(II) ions are reduced to mercury. To prevent this process ferric sulfate is continuously added to the reactor. Since ferric ions are reduced to ferrous ions, the catalyst solution requires reactivation, which is accomplished by hot nitric acid and air. Excess acetylene and acetaldehyde formed are removed, cooled, absorbed in water, and then separated by distillation. Excess acetylene is recycled. Conversion per pass is bout 55%. The Montecatini process89 operates at 85°C and provides 95% overall yield. A modification developed by Chisso90 allows lower operating temperature (70°C) without excess acetylene. Since side reactions are less important under these conditions, higher yields may be achieved. 

Catalytic conversions were experimentally studied in Russia toward the end of the nineteenth century, and especially in the twentieth century, and regularities were empirically established in a number of cases. The work of A. M. Butlerov (1878) on polymerization of olefins with sulfuric acid and boron trifluoride, hydration of acetylene to acetaldehyde over mercury salts by M. G. Kucherov (1881) and a number of catalytic reactions described by V. N. Ipatieff beginning with the turn of the century (139b) are widely known examples. S. V. Lebedev studied hydrogenation of olefins and polymerization of diolefins during the period 1908-13. Soon after World War I he developed a process for the conversion of ethanol to butadiene which is commercially used in Russia. This process has been cited as the first example of commercial application of a double catalyst. Lebedev also developed a method for the polymerization of butadiene to synthetic rubber over sodium as a catalyst. Other Russian chemists (I. A. Kondakov I. Ostromyslenskif) were previously or simultaneously active in rubber synthesis. Lebedev s students are now continuing research on catalytic formation of dienes. 

At the end of the nineteenth century, A. F. Favorskil and his students were studying catalytic conversions of acetylene, including those occurring in the presence of alcoholic potash. His students have continued this series with work on vinylation, hydrolysis of some of the vinyl alkyl ethers (M. F. Shostakovskil), and conversions of vinylethynylcarbinols (I. N. Nazarov). 

A selective poison is one that binds to the catalyst surface in such a way that it blocks the catalytic sites for one kind of reaction but not those for another. Selective poisons are used to control the selectivity of a catalyst. For example, nickel catalysts supported on alumina are used for selective removal of acetjiene impurities in olefin streams (58). The catalyst is treated with a continuous feed stream containing sulfur to poison it to an exacdy controlled degree that does not affect the activity for conversion of acetylene to ethylene but does poison the activity for ethylene hydrogenation to ethane. Thus the acetylene is removed and the valuable olefin is not converted. 

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