Which one of the following is called 'syngas'?

Syngas, a shortened term for synthesis gas, is a fuel gas mixture primarily composed of carbon monoxide (CO) and hydrogen (H2) [3]. It is produced through the gasification of carbonaceous materials such as coal, biomass, or natural gas under high temperatures [1]. While the exact composition can vary depending on the feedstock and process—sometimes containing carbon dioxide, methane, or water vapor—the defining characteristic of syngas is the presence of CO and H2 as its main reactive components [4]. It serves as a critical intermediate in the chemical industry for producing ammonia, methanol, and synthetic fuels via the Fischer-Tropsch process [3]. Unlike producer gas, which contains significant nitrogen from air, syngas is typically generated using steam or oxygen to maintain a high concentration of combustible CO and H2 [3].

Sources

1. [3] https://pmc.ncbi.nlm.nih.gov/articles/PMC8003665/
2. [1] https://www.netl.doe.gov/research/coal/energy-systems/gasification/gasifipedia/syngas-composition
3. [2] https://www.sciencedirect.com/topics/earth-and-planetary-sciences/synthesis-gas
4. [4] https://www.sciencedirect.com/topics/chemical-engineering/syngas-generation