Previous work has shown that very high yields of charcoal are obtained when pyrolysis of the biomass feedstock is conducted at elevated pressure in a closed vessel, wherein the pyrolytic vapors are held captive and in contact with the solid products of pyrolysis. In this paper, we show that, for some biomass species, the yield of carbon produced by this process effectively attains the theoretical value predicted to exist when thermochemical equilibrium is realized. Various agricultural wastes (e.g., kukui nut, macadamia nut, and pecan shells) and tropical species (e.g., eucalyptus, leucaena, and bamboo) offer higher yields of carbon than the hardwoods traditionally employed by industry in the U.S. and Europe. Moreover, the yields of carbon from oat and rice hulls and from sunflower seed hulls are nearly as high as the yields of carbon from hardwoods. There is a correlation between the yield of carbon and the acid-insoluble lignin content of the feed. Charcoal briquettes made from agricultural wastes and lump charcoal from tropical species are promising sources of renewable carbon for use in the smelting of metal ores.

Catalytic conversion of lactic acid to 2,3-pentanedione over sodium salts and base on low surface area silica support has been studied. Yield and selectivity toward 2,3-pentanedione are optimal at around 300 °C, 3−4 s residence time, and 0.5 MPa total pressure. Anions of initial salt catalysts used do not participate in lactic acid condensation to 2,3-pentanedione once steady-state conditions have been achieved; instead, sodium lactate has been identified by postreaction FTIR spectroscopy as the primary, stable species on the support during reaction. Sodium lactate is believed to be an intermediate in 2,3-pentanedione formation. Conversion of a sodium salt to sodium lactate is greatest when the salt used has a low melting point and a volatile conjugate acid; the extent of conversion depends weakly on reaction time and temperature within experimental conditions. At high temperature (∼350 °C), sodium lactate decomposes to sodium propanoate and sodium acetate, which may explain reduced 2,3-pentanedione yields at higher temperatures.

A novel, three-step process for the production of high-quality activated carbons from macadamia nut shell and coconut shell charcoals is described. In this process the charcoal is (i) heated to a high temperature (“carbonized”), (ii) oxidized in air following a stepwise heating program from low (ca. 450 K) to high (ca. 660 K) temperatures (“oxygenated”), and (iii) heated again in an inert environment to a high temperature (“activated”). By use of this procedure, activated carbons with surface areas greater than 1000 m2/g are manufactured with an overall yield of 15% (based on the dry shell feed). Removal of carbon mass by the development of mesopores and macropores is largely responsible for increases in the surface area of the carbons above 600 m2/g. Thus, the surface area per gram of activated carbon can be represented by an inverse function of the yield for burnoffs between 15 and 60%. These findings are supported by mass-transfer calculations and pore-size distribution measurements. A kinetic model for gasification of carbon by oxygen, which provides for an Eley−Rideal type reaction of a surface oxide with oxygen in air, fits the measured gasification rates reasonably well over the temperature range of 550−660 K.