Dehydrogenation polymers

Catalysts in this service can deactivate by several different mechanisms, but deactivation is ordinarily and primarily the result of deposition of carbonaceous materials onto the catalyst surface during hydrocarbon charge-stock processing at elevated temperature. This deposit of highly dehydrogenated polymers or polynuclear-condensed ring aromatics is called coke. The deposition of coke on the catalyst results in substantial deterioration in catalyst performance. The catalyst activity, or its abiUty to convert reactants, is adversely affected by this coke deposition, and the catalyst is referred to as spent. The coke deposits on spent reforming catalyst may exceed 20 wt %. 

McDougall G.J. (2001) Cell-wall proteins from stika spruce xylem are selectively insolubilised during formation of dehydrogenation polymers of conifeiyl alcohol // Phytochem V. 57. P. 157-163. 

Sasaki, S. Nishida, T. Tsutsumi, Y. Kondo, R. Lignin dehydrogenative polymerization mechanism a poplar cell wall peroxidase directly oxidizes polymer lignin and produces in vitro dehydrogenative polymer rich in P-O-4 linkage. FEBS Lett. 2004, 562, 197-201. 

The data presented in a recent communication by Freudenberg et al. (32) show that the methoxyl content of the dehydrogenation polymers of coniferyl alcohol do not change with condensation time. However, their reference to p-hydroxycinnamyl alcohols seems to indicate their appreciation of the significance of a p-hydroxyphenylpropane unit in the mechanism of lignin formation. 

Knshnan K (1988) Characterization of semiconductor silicon using the FT-TR microsampling techniques In Messerschmidt RG, Harthcock MA (eds) Infrared microspectroscopy theory and applications Marcel Dekker, New York, 139-151 Kuo MI, McClelland JF, Luo S, Chien PL, Walker RD, Hse CY (1988) Applications of infrared photoacoustic spectroscopy for wood samples Wood Fiber Sci 20 132-145 Lai Y-Z, Sarkanen KV (1975) Structrual variation in dehydrogenation polymers of comferyl alcohol Cellul Chem Technol 9 239-245... 

Brunow G, Lundquist K (1980) Comparison of a synthetic dehydrogenation polymer of comferyl alcohol with milled wood lignin from spruce, using H NMR spectroscopy Pap Puu 62 669-671... 

Yamasaki T, Hata K, Higuchi T (1972) Chemical properties of dehydrogenation polymer from p-coumaryl alcohol Mokuzai Gakkaishi 18 361-366... 

Robert D, Brunow G (1984) Quantitative estimation of hydroxyl groups in milled wood lignin from spruce and in a dehydrogenation polymer from comferyl alcohol using nC NMR spectroscopy Holzforschung 38 85-90... 

Photoyellowing of lignocellulosic materials has been studied with a new technique based on solid-state NMR analysis of C-enriched dehydrogenation polymer in cell wall tissue. The NMR analysis of unirradiated and irradiated tissue revealed a decrease in the relative amount of coniferalde-hyde and/or coniferyl alcohol end-groups during irradiation. 

G Jacquet, B Pollet, C Lapierre, C Francesch, C Rolando, O Faix. Thioacidolysis of enzymatic dehydrogenation polymers from /7-hydroxyphenyl, guaiacyl and syringyl precursors. Holzforschung 51 349-354, 1997. 

UP Agarwal and N Terashkna. FT-Raman Study of Dehydrogenation Polymer (DHP) Lignins. 12th International Symposium on Wood, Fiber and Pulping Chemistry, Madison, WI, 2003, 3, pp. 123-126... 

Ralph, J., Hehn, R. F., Quideau, S., and Hatfield, R. D. (1992) Lignin-feruloyl ester cross-links in grasses. Part 1. Incorporation of feruloyl esters into coniferyl alcohol dehydrogenation polymers. J. Chem. Soc., Perkin Trans. / (21), 2961-2969. 

Grabber, J. H., Ralph, J., Hatfield, R. D., Quideau, S., Kuster, T., and Pell, A. N. (1996) Dehydrogenation polymer-cell wall complexes as a model for lignified grass walls. J. Agr. Food Chem. 44(6), 1453-1459. 

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