Carbon modified with urea

New light on the importance of the specific surface features on the feasibil% of removal of methyl mercaptan on activation carbon was thrown after study of nitrogen-enriched carbons as media for methyl mercaptan removal [138,140], The capacity on carbons modified with urea was much higher than tliat on the as received adsorbents (Table 6) and even ten times enhancement can be obtained using this route of surface modification. The enhanced performance is attributed to the effect of basic nitrogen incorporated within the carbon matrix. 

Rhodium precipitation in solubilized rhodium-phosphite complex catalyzed liquid recycle hydroformylation may be minimized or prevented by carrying out product recovery in the presence of an organic polymer containing polar functional groups such as amides, ketones, carbamates, ureas and carbonates.[20] Patent examples include the use of polyvinylpyrrolidone and vinylpyrrolidone-vinyl acetate copolymer with diorganophosphite-modified rhodium catalysts. 

The method based on immunosorbents coupled on-line with liquid chromatography-atmospheric pressure chemical ionization mass spectrometry [109], discussed in section 9.4.2.1, has been applied to the determination of substituted urea type herbicides. Supercritical fluid extraction with methanol modified carbon dioxide has been applied to the determinants of sulfonyl urea herbicides in soil [261],... 

Cinchona alkaloids are amongst the most well-known natural products with exceptional medical history and widely recognised catalytic properties that are elaborated in several reviews and recently a book. For more information see also Chapter 14 of this volume. This chapter summarises their use in carbon-heteroatom bond-forming reactions the most used natural and modified Cinchona alkaloids are shown below, for modified alkaloids, only one pseudoenatiomer is shown. Quaternised, and urea and thiourea derivatives are included in Chapters 16 and 19 of this volume respectively. 

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