Real-Time Monitoring of Trace Gas Concentrations in Syngas

A Proton Transfer Reaction Mass Spectrometer (PTR-MS) was implemented for real-time monitoring of volatile trace compounds in syngas in an industrial Fischer-Tropsch process. In industrial gas processes the knowledge about the exact gas composition is closely monitored and controlled. Beside the main constituents which typically appear in percent concentrations, also trace gas impurities at much lower concentrations can play a crucial role.

A poisoning effect of some impurities is a major problem in many catalytic reactions, especially hydrogen reaction such as methanation of coal synthesis gas or reforming of naphthas.  Furthermore, when large amounts of off-gas are being released, also trace concentrations of compounds of extreme toxicity induce environmental risk.

A PTR-MS is a gas analytical device for the sensitive detection of volatile compounds. These devices are well established in several fields of research where their capability to analyze samples in real-time yields insight into system dynamics. Prime examples are the environmental monitoring, food and flavour science, medical and biotechnology research.

We demonstrate the extension of the PTR-technique to the monitoring of trace compounds in syngas. Together with a multiplexer this allows for real-time monitoring of the contaminations at different stages of a Fischer Tropsch process. Several volatile compounds, such as HCN, H₂S, RSH, carbonyls, acids, alcohols and others) have been measured in syngas down to parts per trillion levels. The potential of this novel approach is exemplified by a filter break-through.

We describe the setup to monitor syngas using PTR-MS. We summarize the result of this proof-of-principle project and outline the great potential for process monitoring.