Pyrolysis and Gas-Solid Catalytic Reactions (In-situ Mass Spectrometry in Mechanism Studies)

Pyrolysis is the process by which a substance decomposes upon heating in an isolated or inert atmosphere; catalysis, on the other hand, is the conversion of reactants on the surface of a catalyst. In gas-solid catalysis, the reactants are predominantly gases and the catalyst is a solid; the reaction is often accompanied by a large number of adsorbed species and gas-phase intermediates, including short-lived free radicals. To understand the reaction mechanism, it is necessary to ‘observe’ these intermediates.

Traditional catalyst evaluation often utilises fixed-bed reactors connected to a gas chromatograph at the outlet; this method can only analyse stable products and is unable to detect reactive intermediates. Consequently, mechanistic studies frequently rely on indirect inference of surface species using techniques such as infrared, ultraviolet and nuclear magnetic resonance spectroscopy. The New Ceyuan ProC-1C in-situ catalytic/pyrolysis mass spectrometry analysis system employs photo-composite soft ionisation technology to perform single-pass ionisation and real-time online analysis of all components resulting from light- or heat-induced catalysis, pyrolysis and oxidation, enabling the in-situ capture of reactive intermediates such as methyl radicals, peroxymethyl radicals and formaldehyde. Examples from the literature include: the confirmation of acetylene as a key intermediate in the mechanism of olefin production from synthesis gas (where CO and H₂ first form CH₂-containing compounds on the surface of a metal oxide, which are then converted into acetylene; this is subsequently transformed into low-carbon olefins via the pore channels of SAPO zeolite, enabling selectivity to exceed the limits of conventional Fischer-Tropsch synthesis) ; detection of methyl/peroxymethyl radicals and formaldehyde in OCM; and tracking the dynamics of formaldehyde in MTH.

In terms of operation, the system supports both constant-temperature and programmed-temperature modes, with a temperature range of 25–1,400 °C and a pressure range of 1 Torr–0.5 MPa. Optional configurations include atmospheric/low- and high-pressure pyrolysis reactors, as well as in-situ thermal/ photocatalytic reactors, combustion reactors, flow tube reactors and JSR reactors, suitable for the pyrolysis and gasification of coal, biomass and solid waste, as well as various catalytic systems. For researchers studying reaction mechanisms, it extends the scope from ‘observing stable products’ to ‘observing the entire reaction process’—from the entry of reactants and the accumulation of intermediates to product formation and catalyst deactivation, all of which can be visualised with a temporal resolution on the order of seconds. This is also the meaning of the term ‘in situ’: direct measurement at the actual site of the reaction, without being disrupted by sampling.