A new renewable route to acetonitrile: process design and life-cycle analysis

The research for new routes to acetonitrile developed of catalysts active for the ammoxidation of various substrates. Among these ethanol represents a good substrate in terms of atom economy and, being renewable, in principle can improve the sustainability of the process. A fully integrated process has been designed ex novo for the production of acetonitrile from bioethanol, with 10 kg/h of acetonitrile set as unit of production for calculations. The reactants are ethanol, ammonia and air, but in the separation train, further CO2 is consumed, besides all that produced in the process. All the byproducts, mainly ammonium bicarbonate and sodium cyanide, are recovered as marketable chemicals. In principle, all the carbon atoms and 90% of the nitrogen atoms are turned into reaction products, the main loss being gaseous N2. The Aspen Plus® process simulator has been used for process design and, further, a life cycle analysis was carried out including all the stages involved in the bioacetonitrile production (from raw materials extraction up to the gate plant). The results were then compared with those achieved for the traditional fossil route (SOHIO process), showing a sensible decrease of the environmental burdens in terms of non-renewable resources and damage to ecosystems (e.g., toxicity, climate change, etc.). Finally, a simplified sensitivity analysis was carried out by substituting the starting raw material for the production of bioethanol (corn) with other materials conventionally used worldwide, such as sugar cane and wood. The latter option seems to make the system more competitive in terms of carbon neutrality, thanks to the usage of the residual lignocellulosic fraction available on the market. The basic scheme of the process is reported in the following Figure.