Raw material change in the chemical industry

Abstract:
Today oil is the main raw material for the chemical industry with a share of more than 75% [1]. In the first processing steps, the largest fraction of this oil is fragmented into smaller building blocks such as ethylene and propylene; most other chemicals are synthesized from these components. Due to the foreseeable worldwide shortage of fossil resources and the resulting increase in their prices, it becomes necessary to think about alternative raw materials. In these considerations biomass plays a key role. Although for energetic purposes biomass has a lower potential than other alternatives like photovoltaic, it is the only renewable carbon source. For substituting oil by biomass a main challenge of the near future is the systematic development of new production concepts. Possible routes for future application of biomass as raw material in the organic chemical industry are depicted in Fig. 1. Different approaches for the raw material change in the chemical industry are distinguished. In one approach biomass is converted to synthetic gas and all other products are built up from the so-called C1 building blocks. Natural gas and coal can be used for this route as well. In other approaches more complex molecular structures like glucose, lignin, plant oil etc., which are produced by plants, are used as intermediates, and all final products are obtained from these platform chemicals. In other words via this approach the synthesis power in plants is efficiently utilized. This reduces the required energy and input of other components like e.g. hydrogen in new biochemical concepts. In the present work we evaluate the potentials of these approaches either individually or in combination. In Fig. 2 typical organic products of the German chemical industry are shown as a function of their H:C and O:C ratio. The size of the circular symbols in Fig. 2 is proportional to the annual production rates of these products for 2007. Here it becomes clear, that bio-based reactants have a higher O:C ratio than common chemical products. The complex molecular structure and the polar oxygen of these bio-based reactants result in a higher viscosity and a lower vapour pressure of these components. Also an adaption of existing solvents is needed. To overcome these problems the surplus oxygen has to be removed via defined chemical reactions. Around these reactions mass and energy balances are established. In these terms we consider the caloric balances as enthalpy and exergy balances. Via these balances the ideal routes for producing specific final goods are determined, and the required amount of energy can be estimated. This is used to determine most feasible routes from the raw material to the final product.

Keywords:
Exergy balances, biomass, Raw material change in the chemical industry