Dehydration reactions in polyfunctional natural products

Here, we review methods for chemical dehydration of alcohols to alkenes and discuss the potential of late-stage functionalization by direct, site- and chemo-selective dehydration of complex molecular substrates.

Mechanical and chemical dehydration for pre-drying of black oat silage

This study aimed to evaluate mechanical and chemical methods of forage dehydration in the production of black oat pre-dried silage (Avena strigosa Schreb) under different dehydration times. The experiment was conducted in a randomized block experimental design with five replications and arranged in a 2 x 6 factorial scheme. We assessed two methods of dehydration, mechanical and chemical, over six dewatering times, being made at 0, 3, 6, 9, 12, and 15 days after cutting or application of glyphosate. Harvest took place at 88 days after emergence, at pre-flowering. We evaluated dry biomass production at harvest, dry matter losses during dehydration in the field, losses during ensiling, gauging effluent output, and pre-dried silage chemical composition. There was an interaction between dehydration method and harvest time for most of the production characteristics. Chemical dehydration showed an enhanced dry matter recovery at the field level, however, unsuitable for pre-dried silage. The longer the dehydration period, the lower the losses for both analyzed methods; nevertheless, the chemical method reached unsatisfactory DM contents to produce good quality silage.

Catalytic Pyrolysis of Sewage Sludge

Pyrolysis of dried sewage sludge samples treated with the additives silica zeolite, calcium oxide, dolomite, ammonium sulphate or diammonium sulphate were conducted by thermal gravimetric anaysis (TGA). The pyrolysis of the untreated sewage sludge showed four regions in which differential thermal gravimetry (DTG) peaks was observed. These peaks were identified as being due to: dehydration of the physically bound water in the sludge; chemical dehydration of carbohydrates in the sludge; decomposition of hemicellulose, cellulose and proteins in the sludge, and; decomposition of lignin and plastics in the sludge. Addition of chemical additives changed the mass-loss due to chemical dehydration, with the dolomite additive reducing the mass-loss and AS or DAP increasing the mass-loss. AS and DAP also changed the mass-loss kinetics of the decomposition of hemicellulose and cellulose. At temperatures greater than 750°C, the proportion of sludge converted to char was unaffected by the type of additive used. The observed mass-loss data was modelled with a three or four step kinetic mechanism; the calculated kinetic parameters are reported.