KINETIC AND PROCESS MODELS FOR THE UPGRADING OF BIOETHANOL AND CARBON DIOXIDE

Primary sources recycle, renewable energy production, and limitation of fossil carbon release as greenhouse gas are deeply connected scientific issues that have been quickly emerging for the last fifty years. Constant improvements of energetic cycles efficiencies and in the atom-economy of chemical reactions are effectively sided by the substitution of carbon and oil with biomass as source of building blocks and power. Sugars or cellulose, in turn, becomes all the more versatile and are exploited more efficiently if converted into methane, syngas or ethanol. This latter liquid has already been established for long as a renewable fuel, its transformation into green plastic is a mature technology thanks first to Alumina- or zeolite-based catalysts for ethylene production; its reforming into hydrogen has been made viable by the skillful use of Ni-based materials (beside more costly noble metals) and further reactions paths are being open on still different catalysts. This work presents three feasibility studies and basic process designs to upgrade ethanol into higher value chemicals: ethylene, ammonia, and acetonitrile. A fourth study is dedicated to the conversion of ethanol into the more versatile hydrogen, that acts also the pivot to feed indirectly a fuel cell and produce electricity, rather than thermal power. A fifth design makes hydrogen follow the reverse power-to-gas route: this key energy-carrier meets then the carbon dioxide released by other processes, and the two are recombined to yield methane. They are graphically shown in figure. This thesis consists of two parts. In the first, for each process are reviewed the basic reaction mechanism and the best-performing catalytic formulations, either inherited from the literature or tested directly in the laboratories of this University. The mass and energy balances from the reactor to the separation units are calculated mainly with Aspen Plusootnote{Aspen Technology Inc.}; several side-calculations have been performed with other software as specified. The second part reports the experimental study supporting the calculation of the separative blocks in the ethanol-acetonitrile process. Several experiments of drying, thermal decomposition, miscibility, batch distillation and micro-distillation have been carried out: they show the salting-out of acetonitrile from water in presence of ammonium salts, a phenomenon not always addressed by commonly used thermodynamic calculation packages.