A low carbon methanol process using natural gas pyrolysis in a catalytic molten metal bubble reactor.

• Optimized design of new natural gas pyrolysis reactor using catalytic liquid metal. • Designed new methanol process using natural gas pyrolysis and CO2 utilization. • Negative cradle-to-gate CO 2 emissions are achievable with new process. • Low CO 2 emissions from supply chains of natural gas and captured CO 2 are critical. • Process is economically profitable if the carbon produced by pyrolysis is sold. Due to its abundance and relatively low cost, natural gas will continue to be a common feedstock for methanol production, at least in the near to medium term. The present work focuses on natural gas pyrolysis in a catalytic liquid metal bubble reactor, combined with CO 2 utilization, as an alternative to traditional steam reforming processes. The pyrolysis reactor consists of multiple vertical tubes filled with molten Cu 0.45 Bi 0.55 alloy and heated in the radiant zone of a fired heater. The reactor geometry and operating conditions are optimized by rigorously accounting for the coupling of bubble flow hydrodynamics with the catalytic and non-catalytic kinetics of methane pyrolysis in molten metals. Pyrolysis generates hydrogen and solid carbon, which rise first through the liquid metal and then through a layer of molten salt (e.g., NaBr) whose purpose is to minimize the loss of liquid metal entrained with the carbon. The carbon forms a recoverable layer above the salt, and the hydrogen reacts with captured CO 2 in a separate methanol synthesis reactor. The cradle-to-gate and cradle-to-grave CO 2 emissions are 0.074 and 1.45 t CO 2 -eq/t methanol, respectively, for median supply chain emissions of natural gas and captured CO 2. This is a lower carbon footprint than other practical pyrolysis and steam methane reforming processes. Negative cradle-to-gate CO 2 emissions are achievable if natural gas and captured CO 2 are sourced from supply chains with low emissions. The estimated carbon production cost of $0.27/kg is well below the recent market price of carbon black in the United States. The production cost of carbon is most sensitive to the fixed capital investment of the plant, the captured CO 2 cost, the natural gas and methanol costs, and the discount rate. [ABSTRACT FROM AUTHOR]