Sustainable Raw Material Base and Green Chemistry
New Raw Materials Create a New Set of Challenges for Green Chemistry
Catalysts Hold the Key to Sustainability
Catalysis is definitely the priority issue for achieving a sustainable raw material base. Catalysts hold the key to the avoidance of auxiliary substance utilization (e.g. “old timers” such as Friedel-Krafts alcylation). In addition, selective control of the reaction, high target product yields and minimum waste also reduce the effort needed for separation. The result is minimal energy consumption combined with maximum raw material efficiency. In conformance with the principles of green chemistry, the reactions should take place at low temperatures. Lower temperatures normally equate to higher selectivity, but it is important to keep in mind that particularly in integrated production environments waste heat can be utilized far more efficiently at higher temperatures.
Whatever the raw material base, recyclability and utilization cascading are essential aspects to consider during product development (this applies especially to plastics). Utilization of the tightly bound carbon in CO2 without using the energy content will probably restrict biodegradability to niche applications.
One key aspect is missing from the existing list of principles, namely water consumption. Water is vital for the production of plant-based biomass and for large-scale chemical production, but its availability is limited in many parts of the world. Water scarcity is a major factor which is limiting the expansion of coal-based chemical production in China's coal fields. The need to minimize water consumption and maximize water recycling will have to be added to chemical engineering principles 4, 5 and 12.