Heterogeneous synthesis

M. T. Drexler, M. D. and Amiridis, Heterogeneous Synthesis of Flavanone over MgO, Chemical Industries (Dekker) Catal. Org. React.) 451-457 (2000). 

To understand a heterogeneous synthesis process, the following preliminary experiments were performed in a homogeneous solution (1) In the absence of zeolite, the sonochemical reduction of [Pd(NH3)4]2+ to Pd° was found to occur, but the rate of [Pd(NH3)4]2+reduction was much slower than that of [PdCL(]2 reduc-tion. (2) It was confirmed that 2-propanol acted as a precursor to form reductants under ultrasonic irradiation. 

Drexler, M. T. and Amiridis, M. D. Kinetic investigation of the heterogeneous synthesis of flavanone over MgO, Catal. Lett., 2002, 79, 175-181. 

The results of a complex investigation of the process and catalysts for heterogeneous synthesis of butadione (diacetyl) are presented. A series of the dehydrogenating catalysts for this reaction was investigated. The attention was focused on the study of... 

Solution The net reaction we seek is the sum of the heterogeneous synthesis and the reverse of the vaporization of liquid bromine ... 

Drexler, MT Amiridis. MD. The etTect of solvents on the heterogeneous synthesis of fiavanone over MgO. Journal of Catalysis. 2(K)3 214. 136-145. 

Common industrial methods to form polymers are summarized in Table 5. The label heterogeneous is also used to describe industrial polymer syntheses that have a two phase structure to the reaction mixture. However, these mixtures do not always contain the catalyst used in a heterogeneous chain polymerization synthesis. The two labels ate based on the same phenomena of a reaction mixture containing several phases but are distinct in that the industrial, heterogeneous synthesis method has no limit on what constitutes the second phase in the reaction. 

Abargues, R., Gradess, R., Canet-Ferrer, J., Abderrafi, K, Valdes, J. L, and Martinez-Pastor, J. (2009) Scalable heterogeneous synthesis of metallic nanoparticles and aggregates with pol5wlnyl alcohol. New J. Cftem., 33(4), 913-917. 

K. Osseo-Asare, F. J. Arriagada, and J. H. Adair, "Solubility Relationships in the Coprecipitation Synthesis of Barium Titanate Heterogeneous Equihbria in the Ba—Ti—C2O4—H2O System," in G. L. Messing, E. R. Fuller, Jr., and Hans Hausin, eds.. Ceramic Powder Science Vol. 2,1987, pp. 47-53. 

Oxo Synthesis. Ad of the synthesis gas reactions discussed to this point are heterogeneous catalytic reactions. The oxo process (qv) is an example of an industriady important class of reactions cataly2ed by homogeneous metal complexes. In the oxo reaction, carbon monoxide and hydrogen add to an olefin to produce an aldehyde with one more carbon atom than the original olefin, eg, for propjiene ... 

The proposed mechanism by which chlorinated dioxins and furans form has shifted from one of incomplete destmction of the waste to one of low temperature, downstream formation on fly ash particles (33). Two mechanisms are proposed, a de novo synthesis, in which PCDD and PCDF are formed from organic carbon sources and Cl in the presence of metal catalysts, and a more direct synthesis from chlorinated organic precursors, again involving heterogeneous catalysis. Bench-scale tests suggest that the optimum temperature for PCDD and PCDF formation in the presence of fly ash is roughly 300°C. 

The effect of pH and the piC of the thiol has been discussed. This reaction is not of great synthetic interest, primarily because it yields a mixture of products, but it is of commercial consequence. It is also appHcable ia polysulfide synthesis, where the presence of small amounts of thiols can cause significant problems for the stabiUty of the polysulfide (51). A similar reaction between thiols and sulfides has also been described (52). In this instance, the process is heterogenous and acid-cataly2ed. 

Polyacetylenes. The first report of the synthesis of a strong, flexible, free-standing film of the simplest conjugated polymer, polyacetylene [26571-64-2] (CH), was made in 1974 (16). The process, known as the Shirakawa technique, involves polymerization of acetylene on a thin-film coating of a heterogeneous Ziegler-Natta initiator system in a glass reactor, as shown in equation 1. 

The use of azide reagents is also important for the synthesis of cyclic sulfur(VI)-nitrogen systems. The reaction of SOCI2 with sodium azide in acetonitrile at -35°C provides a convenient preparation of the trimeric sulfanuric chloride [NS(0)C1]3 (Eq. 2.16). " Thionyl azide, SO(N3)2 is generated by the heterogeneous reaction of thionyl chloride vapour with silver azide (Eq. 2.17). This thermally unstable gas was characterized in situ by photoelectron spectroscopy. The phenyl derivative of the six-membered ring [NS(0)Ph]3 can be prepared from lithium azide and PhS(0)Cl. ... 

Attenlion should be drawn to ihe use of tin oxide systems as heterogeneous catalysts. The oldest and mosi extensively patented systems are the mixed lin-vanadium oxide catalysis for the oxidation of aromatic compounds such as benzene, toluene, xylenes and naphthalene in the. synthesis of organic acids and acid anhydride.s. More recenily mixed lin-aniimony oxides have been applied lo the selective oxidaiion and ammoxidaiion of propylene to acrolein, acrylic acid and acrylonilrile. 

Because diacetylene is unstable, a stable diacetylene derivative, 1-methoxybut-l-en-3-yne (65CB98), is often employed in the synthesis of pyrroles. The reaction with ammonia proceeds under conditions of heterogeneous catalysis (a mixture of reagent vapors is passed through a catalyst-containing reactor heated to 150°C), approaching a yield of 50-70% but with primary aromatic amines, the yield drops to 20%. 

---