The chemical industry still produces its main raw materials almost entirely from natural gas and naphtha, a product of petroleum. What is needed to replace this basis is outlined in a study published by DECHEMA on July 20. The German Association for Chemical Engineering and Biotechnology conducted the research for the research agency IREES, examining the chemical industry in Germany.
According to the study, three carbon sources can eventually replace natural gas and naphtha. The first is CO2 from sources where emissions are unavoidable, such as cement and lime factories, and from biogenic sources such as biogas plants. The second is biogenic residues and waste streams. The third is plastic waste. For each source, the researchers describe the entire chain, from the pre-processing of the raw material to the major petrochemical platform chemicals upon which the rest of the chemical industry builds. By comparing these chains with one another, they arrive at what they call efficiency processes. These are already technically quite advanced, offer a clear view of lower costs and lower energy consumption, and, moreover, require little raw material.
Three routes to the same building blocks
For the conversion itself, the study distinguishes three main routes. The first is called power-to-X. In this process, CO2 and green hydrogen combine to produce methanol, from which basic substances are derived. A variant is the Fischer-Tropsch route, which supplies synthetic raw materials for the steam cracker, the plant in which the chemical industry produces its building blocks. The second route is biomass gasification, after which the synthesis gas is further converted. The third is thermochemical recycling of plastics, primarily via pyrolysis, in which waste is heated without oxygen until raw materials remain that the cracker can handle.
These routes do not necessarily compete with each other. DECHEMA points out that some processes complement one another. Plastics and biomass, for example, can be gasified together, and pyrolysis and Fischer-Tropsch synthesis can run side by side to feed the cracker. There are therefore multiple technical pathways to the same chemical building blocks, as long as alternative carbon and renewable energy come together.
What needs to happen outside the lab
Before this operates on an industrial scale, further research is needed on individual process steps, plus experience from pilots and demonstration plants. The study identifies four areas: raw material pretreatment, catalyst development, reaction technology, and product processing. These four must be considered in conjunction, as only then can real gains be made in terms of energy and raw materials. According to the researchers, processes that are technically still immature but highly efficient, such as homogeneously catalyzed methanol synthesis and the direct production of olefins from synthesis gas, are also among the priorities.
In addition, the study identifies three conditions that lie outside of technology. Factories switching to electricity need a power price that can compete internationally. Supra-regional transport networks for CO2 and hydrogen must be established more quickly. And politicians should clearly opt for the material application of biomass and plastic waste over incineration for energy.
The researchers do add a caveat to this. The shift makes the chemical industry less dependent on fossil fuel imports, but not self-sufficient. The dependency shifts to hydrogen and hydrogen derivatives from countries with abundant cheap renewable energy. The question remains who will pay for this. To retain value in Germany and Europe, the study favors converting existing factories over expensive new construction on vacant land.
The study originated within EE4InG2, a research project funded by the German Ministry of Economic Affairs and Energy. The report is available for free download.
Source: DECHEMA
