Both feedstock and energy efficiency are decisive factors in achieving economic ­viability and competitiveness in chemical production. At the same time they determine the sustainability of chemical pro­cesses. To enhance feedstock and energy efficiency is therefore an ongoing target.

As an integrated chemical manufacturer BASF has an advantage with respect to value creation by optimizing product and energy streams of the network system consisting of a large number of production plants. Furthermore, this integration offers flexible adaptation to changing market conditions. Developing new processes with significantly improved feedstock and energy costs is the cornerstone of this strategy. A prerequisite for the successful introduction of these new processes is that their production costs are lower than the variable cost of the established processes to be replaced. Examples of recently introduced processes include:

• 2-Propylheptanol: A raffinate II based alcohol replacing a propylene based alcohol for plasticizer and detergent applications;
• Propylene oxide process: avoiding coupled products by using hydrogen peroxide as the oxidant;
• Flexible use of renewable materials: A new nonionic detergent made by ethoxylation of mixtures of 2-Propylheptanol and native Octadecanol; or
• Use of waste streams: N₂O as an oxidant in a new production process for cyclododecanone.

Use Less and Cheaper Feedstock's

Different options may be followed to achieve this goal. One is to optimize the yield of large-scale processes by ongoing research efforts. The current technology for acrylic acid is based on catalytic gas phase propylene oxidation. This two-stage pro­cess with acrolein as the intermediate was introduced commercially more than 30 years ago. At that time, propylene was a cheap raw material and overall yield was only approximately in the range of 80 %. Total oxidation was a ­serious side reaction and about 600 kg of carbon dioxide were produced per ton of acrylic acid. Improved catalysts and process optimizations have increased the acrylic acid yield by about 10 % and have cut carbon dioxide formation to one third. At the same time the productivity of acrylic acid by reactor volume could be doubled which is partially due to the lower heat production based on the reduced rate of total oxidation.

Another option is to evaluate the relative value for carbon in hydrocarbon streams and to increase preferentially the use of the lower priced streams. Looking at steam cracker products, propylene value has increased in recent years due to a strong market demand for polypropylene. In comparison, the C4-cut containing butadiene, n/i-butenes and butanes has a much lower value. The same is true for streams derived thereof such as raffinate I or raffinate II. The replacement of propylene-based 2-ethylhexanol by raffinate-II-based 2-propylheptanol is an example for this strategy. The superior properties of this alcohol in plasticizer and detergent applications add favorably to the improved feedstock economics and support its successful introduction into the market.

Coupled synthesis of large volume products are economically disfavored if the growth rates or the market cycles of those products differ. It also requires increased investment and logistics to handle two or more sales products, possibly in different markets. This is the case in the styrene monomer propylene oxide (SMPO) process, where propylene oxide enjoys a higher growth rate compared to styrene. This disadvantage can be overcome by the hydrogen peroxide to propylene oxide (HPPO) process, where propylene is oxidized catalytically by hydrogen peroxide to propylene oxide with water as the only coupled product. In addition, this process offers improved energy, feedstock, and process water efficiency.

Renewable Feedstock's

Renewable materials such as detergent alcohols from fatty acids are regarded neutral with respect to carbon dioxide emissions. They have been used for many years in the chemical industry to produce non-ionic detergents. Depending on the fluctuation of harvests due to weather conditions and on competing consumption in the food chain the availability of these products varies. BASF has therefore established a flexible production system for non-ionic detergents based both on in-house petrochemical as well as on native alcohols. Even combinations of native and petrochemical alcohols can be used very efficiently. The recently introduced non-ionic detergent Lutensol M is based on the ethoxylation product of a mixture of the above mentioned 2-propylheptanol and octadecyl alcohol. The superior properties of this detergent over standard non-ionic surfactants have largely contributed to the market success. Furthermore, an eco-efficiency analysis by BASF has shown that during production it causes fewer emissions into waste water and consumes less energy than other standard surfactants.

At the same time processes were actively developed at BASF to make use of glycerol, a coupled product of native fatty alcohol as well as of biodiesel production. An example is a hydrogenation process to yield 1,2-propanediol which is ready for commercial application. Another successful implementation of a renewable material is the replacement of ethylene based synthetic ethanol by bioethanol in the synthesis of ethylamines. This catalytic conversion with ammonia requires careful separation of catalyst poisons such as sulfur compounds.

Carbon Footprint Improvements

N₂O is a greenhouse gas which is 310 times more harmful than carbon dioxide. It is emitted in the production of nitric acid/nitrate fertilizers as well as in the production of adipic acid. The efficient control of these emissions is therefore a top priority. BASF has successfully introduced and applied catalytic N₂O destruction technology and is an experienced producer of advanced catalysts with improved properties. By using our catalyst, one large customer alone will reduce his emissions of CO₂ equivalents by 10 million tons per year.

In addition, technology was developed to utilize N₂O as a chemical feedstock. This waste stream will serve as an oxidant to produce cyclododecanone, an intermediate for nylon-12. Compared to established cyclododecanone technology the new synthesis involves only three instead of five steps and offers lower investment costs and improved selectivity. Further attempts to use greenhouse gases as feedstocks are explored in a joint research project with the Technical University of Munich and the University of Hamburg. The aim is to produce polycarbonates from alkene oxides and carbon dioxide.

BASF has established highly integrated network (Verbund) sites in Europe, the U.S. and Asia where heat and electricity is produced most efficiently in combined cycle power plants and where products as well as heat are exchanged between production plants to achieve best in class energy and feedstock consumption. As the first chemical company we have also determined and published our corporate carbon dioxide footprint originating from our different production sites and compared it to the energy (or CO₂) savings that can be achieved with our products. The results which have been examined by the neutral Oeko-Institut in Freiburg, Germany revealed a threefold excess of CO₂ savings by our customers compared to the overall CO₂ emissions caused directly or indirectly by BASF.

Better Economic Results and Sustainability

The examples demonstrate how development and introduction of energy and feedstock efficient production processes and the increased integration of product and energy streams from chemical plants help to further improve the CO₂ balance. The gratifying result is that optimizing the production system of an integrated manufacturer not only increases economic value but also minimizes the carbon footprint.