Application of Aspen Plus to a Life Cycle Inventory of fine chemicals: a case study of [Bmim][BF4]

It is well known that one of the most critical phases of the Life Cycle Assessment (LCA) is the compilation of the inventory. Indeed we need data that are often not readily available because they relate to processes and emerging technologies where disclosure is limited, for instance when the LCA is involved in a product whose production is not extended on an industrial scale, or is still on an experimental basis. In these cases we can rarely use primary data collected directly on site and representative of the system under review, but we must be satisfied with secondary data, obtained from databases. The case study submitted in this work represents a LCA ‘cradle to the gate’ of a compound of fine chemicals, the [Bmim] [BF4] (1-butyl-3-methyl-imidazolium tetrafluoroborate), whose industrial application is limited and for which the compilation of the inventory is particularly complex and affected by uncertainty. The [Bmim] [BF4] belongs to the class of ionic liquids (ILs) and several research activities have focussed on it. ILs are organic salts that are liquid at room temperature, consisting of asymmetric and bulky ions that prevent the molecular framework necessary to crystallization. Developed over the last decade to be used as “eco-compatible” substitutes of traditional organic solvents, they have found many different and unexpected applications. This study was carried out with the support of the calculation software GaBi IV. Data necessary for the stage inventory, not present in the GaBi IV database, have been implemented using the Aspen Plus engineering software that can run the simulation and dimensioning of industrial chemical plants. The synergy of the two software applications made it possible to reconstruct the entire production process of [Bmim] [BF4] and to identify the steps that more deeply affect the environmental point of view.