Using milling balls as catalysts – Understanding the novel concept of direct mechanocatalysis

Project Information

Mechanocat

Grant agreement ID: 948521

DOI

10.3030/948521

Project closed

EC signature date 14 August 2020

Start date 1 November 2020

End date 31 October 2025

Funded under

• EXCELLENT SCIENCE - European Research Council (ERC)

Total cost

€ 1 496 350,00

EU contribution

€ 1 496 350,00

Coordinated by

RUHR-UNIVERSITAET BOCHUM
Germany

Periodic Reporting for period 4 - Mechanocat (Using milling balls as catalysts – Understanding the novel concept of direct mechanocatalysis)

Reporting period: 2025-05-01 to 2025-10-31

Summary of the context and overall objectives of the project

The ERC project Mechanocat developed a fundamentally new mode of catalysis—direct mechanocatalysis—driven solely by mechanical energy. Unlike conventional catalytic systems that rely on thermal, photochemical, or electrochemical activation, this approach harnesses the energy generated by the collisions of milling balls inside a mechanochemical reactor. The key innovation is that the milling media themselves act as the catalyst, eliminating the need for additional catalyst powders or complexes.

This concept addresses a central challenge in modern chemistry: the creation of sustainable, solvent-free, and recyclable catalytic processes. Conventional catalysis depends on solvents and complex recovery procedures, generating waste and reducing efficiency. Direct mechanocatalysis operates entirely in the solid state, with the catalyst surface constantly renewed during milling and easily separated and reused afterward—an inherently sustainable alternative.

The project achieved the following main objectives:

Establish and validate direct mechanocatalysis as a new catalytic methodology powered by mechanical energy alone.

Apply and optimize it for key reactions, including Suzuki–Miyaura, Sonogashira, Heck, Glaser, oxidation, hydrogenation, and cyanation transformations.

Elucidate its mechanistic principles using in situ characterization tools such as pXRD, Raman spectroscopy, and XPS.

Develop technological innovations, including galvanostatic coating of milling tools and adaptation to continuous reactors like extruders and acoustic mixers.

Demonstrate scalability and versatility, integrating reactive gases (e.g. H2, O2) for solid–gas mechanocatalytic processes.

All objectives were fully met. The core hypothesis—that catalysis occurs directly on the milling ball surface—was confirmed, and mechanical impact was shown to drive complex reactions without solvents. Mechanocat established direct mechanocatalysis as a new field of catalysis, combining sustainability, efficiency, and scalability, with clear industrial potential and societal benefits through greener chemical production.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

From its start, the ERC project Mechanocat aimed to establish a new catalytic methodology—direct mechanocatalysis—operating solely through mechanical energy. Over its duration, the concept was developed, experimentally validated, and extended toward industrial application.

The project began by proving the core hypothesis: that the milling ball or reactor surface acts as the active catalyst, with reactions occurring directly on its surface under mechanical impact. This was first shown in Pickhardt et al., Angewandte Chemie (2022) for the Pd-catalyzed Suzuki–Miyaura coupling, where XPS confirmed surface-based catalytic activity.

Building on this foundation, the team expanded direct mechanocatalysis to numerous metal-catalyzed transformations, including Sonogashira, Heck, and Glaser couplings, as well as oxidations, hydrogenations, and cyanation reactions. Detailed studies established how milling parameters (e.g. frequency, ball size, energy input) control catalytic performance, replacing conventional solution-based parameters.

A major technological milestone was the galvanostatic coating method, which deposits catalytically active metals on milling media and reactor walls. This innovation enabled new reactor types such as extruders and acoustic mixers, allowing continuous and milling-media-free mechanocatalysis. The technology was patented, with several related patents filed.

The project further incorporated reactive gases (e.g. H2, O2) using pressure-compatible reactors, extending the method to solid–gas catalytic processes—a major and unexpected advancement. Extensive in situ and operando studies (synchrotron XRD, Raman spectroscopy) provided mechanistic insight, confirming mechanical impact as a genuine energy source for catalysis.

The results were widely disseminated through over twenty high-impact publications, press releases, and more than fifty conference presentations, generating strong industrial interest and collaborations now applying the concept to real synthesis processes. The project also had substantial career impact, with team members advancing to leading roles in academia and industry.

Overall, Mechanocat transformed direct mechanocatalysis from an exploratory idea into a validated, scalable, and sustainable catalytic technology, establishing a new branch of catalysis based on mechanical energy and positioning the group as an international leader in this emerging field.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

We developed two methodologies that advance the state of the art:

First, we established the concept of Direct Mechanocatalysis, where catalytic reactions are carried out in mechanochemical reactors using the milling ball itself as the catalyst. This eliminates the need for solvents, ligands, or catalyst powders, creating a solvent-free, recyclable, and sustainable catalytic platform. The catalyst surface is continually renewed during milling, ensuring long lifetimes and stable activity. This represents a new catalytic mode powered solely by mechanical energy, providing a foundation for scalable solvent-free synthesis.

Second, we developed a galvanostatic coating process that allows milling balls and reactor vessels to be uniformly coated with catalytically active metals (Pd, Ni, Cu, Au). These coated tools retain catalytic activity under mechanical stress while drastically reducing the use of costly materials. The technique enables customizable catalytic systems and extends mechanocatalysis to continuous reactors such as extruders and acoustic mixers, bridging the gap to industrial implementation.

By the project’s end, both advances were fully realized. The scope of direct mechanocatalysis expanded from classical C–C couplings to oxidations, hydrogenations, and cyanations, including solid–gas reactions. Continuous mechanocatalytic processes were successfully demonstrated in extruder-based reactors, confirming scalability and industrial relevance.

Technology transfer was achieved through active collaborations with industry, where the method is now being integrated into real synthesis workflows. The project’s outcomes—protected by patents and disseminated through high-impact publications, conferences, and media—firmly established direct mechanocatalysis as a new paradigm in sustainable catalysis, with ongoing technological and industrial development beyond the ERC project.

MIlling Balls