The complex field of catalysis encompasses various disciplines such as homogeneous, photocatalysis, biocatalysis, heterogeneous, and electrocatalysis. It also includes areas that are inherently linked to the reaction process and cannot be separated from it, such as reactor design and process engineering. Scientific progress in catalysis relies on both experimental and computational methods.

For solid-state catalysts, there is a strong connection to materials science, while biocatalysis closely interacts with microbiology and molecular biology.
The following sections provide a more detailed overview of the individual branches of catalysis.

 

 

 

 

HETEROGENEOUS CATALYSIS

Today, most chemical processes are catalytically assisted: catalysts accelerate reactions, or make them possible in the first place, without being consumed in the process. In heterogeneous catalysis, the catalyst and the reactants exist in different “phases,” as chemists say that is, in different physical states.

The catalyst is often solid, such as in an automotive catalytic converter, while the reactants, gases or liquids, flow past it and are triggered into reaction through contact. Compared to homogeneous catalysis, heterogeneous catalysis offers advantages: reactants and products are easier to separate, and the catalyst can be more easily regenerated.

The term catalysis was coined in the 19th century by Jöns Jakob Berzelius, who observed similarities in very different chemical reactions for example, the dehydrogenation of alcohols to aldehydes on glowing metals, or the breakdown of ethanol into ethylene and water over alumina. In these cases, alongside the reactants and products, there is always a third substance involved one that appears to remain unchanged.

 

HOMOGENEOUS CATALYSIS

Catalysts control and accelerate nearly all chemical and biochemical reactions without appearing in the final product. Chemists refer to homogeneous catalysis when all reactants involved in the process are in the same physical state, most commonly as a solution in the liquid phase.

A classic catalytically influenced process is alcoholic fermentation from sugar, first practiced by the Sumerians around 8,000 years ago in Mesopotamia.

The lead chamber process by Desormes and Clément (1806) is considered the first technical procedure for producing a bulk chemical sulfuric acid. Enzyme catalysis dates back to the early 20th century, with examples like the enzymatic cleavage of sucrose into glucose and fructose. Today, enzyme catalysis underpins the resource-efficient production of pharmaceuticals, fine chemicals, vitamins, and detergents.

Homogeneous catalysts often involve transition metals, named for their position in the periodic table. The reactive metal center is typically embedded in a molecular framework, called a ligand, which also influences key parameters of the reaction, such as turnover or selectivity.

Historically, homogeneous catalysis developed as the "workhorse" of organic chemistry, which is carbon-based and predominantly product-oriented. Among its advantages over heterogeneous catalysis are milder reaction conditions (lower pressures and moderate temperatures) and higher selectivity, which leads to fewer side products. However, recovery of the catalyst after the reaction remains a challenge.

Today, the previously rigid boundary between homogeneous and heterogeneous catalysis is increasingly blurred. Modern research reflects this convergence, especially as inorganic chemistry, more analytical and theory-driven, contributes to the understanding of catalytic mechanisms across both domains.

ELECTROCATALYSIS / PHOTOCATALYSIS

Photocatalysis, electrocatalysis, and their combination, photoelectrocatalysis, are catalytic processes of fundamental importance for addressing the major challenges in renewable energy conversion and storage. These systems combine heterogeneous or homogeneous catalysis with additional photo- and/or electrochemical parameters such as wavelength, current, or potential. Together, they represent some of the most complex interfacial charge-transfer processes in catalysis.

In photocatalysis, the generation, transport, and participation of “free” charge carriers (electrons and holes) at the surface is directly linked to the catalytic transformation of chemical bonds—i.e., the breaking and forming of molecules. When photons of a specific wavelength are absorbed by a semiconductor, electron–hole pairs are generated. These can be used, for example, to split water catalytically.

In electrocatalysis, the catalytic transformation takes place at or across the electrode–electrolyte interface, where free charge carriers tunnel into or out of more localized electronic states (i.e., chemical bonds). This type of electric interface is essential for systems like fuel cells, electrolyzers, and the electrochemical production of chemicals and metals.

BIOCATALYSIS

In biocatalysis, enzymes are used to catalyze a wide variety of chemically relevant reactions. These natural catalysts facilitate a broad spectrum of syntheses under mild reaction conditions. One of their greatest advantages is their chemo-, regio-, and stereoselectivity, allowing for the production of highly (optically) pure target compounds.

Compared to conventional chemical methods, biocatalytic processes often avoid the need for toxic reagents such as heavy metals, protecting group strategies, and, in many cases, organic solvents, making them significantly more environmentally friendly.

Historically, enzymes were isolated from microorganisms, plants, or animal extracts. Today, modern biotechnological methods allow for the recombinant production of enzymes at industrial scale for example, in E. coli or S. cerevisiae. Enzymes can also be tailored to industrial needs through protein engineering, using either rational design based on 3D structure or directed evolution (awarded the Nobel Prize in Chemistry in 2018).

Biocatalysis is widely applied in the production of flavors and fragrances, in the food industry, in organic synthesis, oleochemistry, and most notably in the large-scale synthesis of pharmaceutical compounds and intermediates. Enzymes such as proteases, amylases, cellulases, and lipases are also common components in laundry detergents, where they help break down stains under mild conditions—once again contributing to sustainability and environmental protection.

 

Further Links                                                             Want to learn more? 

Fundamentals of Biocatalysis                                                                      The key fundamentals can be found here:

Nobel Prize in Chemistry 2018                                                                    Biocatalysts and Enzyme Technology

Website of U. Bornscheuer

 

PROCESS ENGINEERING

In more than 80% of industrial chemical processes, catalysts are used. A catalyst increases the reaction rate and improves yield, without being consumed in the reaction. Due to the variety of chemical processes and catalyst types, there is a broad range of chemical reactors and equipment designed to ensure safe and efficient catalytic operations.

In addition to the effective contact and mixing of reactants with the catalyst, heat transfer and flow characteristics, especially narrow residence time distribution, play a crucial role in reactor selection. Reactants must be properly conditioned, and the resulting reaction mixture needs to be efficiently processed and separated. In many cases, the separation and recycling of reactants or catalyst materials determine the economic viability of a process.

Process development for a specific product typically begins in the laboratory, with extensive experimental work supported by analytical methods and simulations. Once optimized, the process is scaled up to the pilot plant level, and often through several stages, into full production. From the lab onward and especially at pilot scale, sensors, analytical technologies, and the process control system become increasingly important for optimal process operation.

A wide variety of separation techniques are available for processing reaction mixtures, depending on the phases involved, concentrations of components, and the energy required. Here, too, recycling streams and energy/material integration are key to achieving economically and environmentally sustainable processes.

INFORMATION TECHNOLOGY

Planned National Data Infrastructure

A key goal of NFDI4Cat is the development and implementation of both local and cross-cutting data infrastructures, as illustrated in the accompanying figure. This includes a distributed repository infrastructure and additional services—both local and community-wide—that are essential for creating a national environment for catalysis-related research data.

To ensure sustainability and future-readiness, the infrastructure will be built on existing standards and principles, and will be aligned with efforts from other NFDI consortia and scientific communities. Open-source solutions based on modern technologies, especially knowledge graphs, will be prioritized.