Process Intensification and Modular Production for Converting Stranded Gas to Value-Added Products

In the United States and rest of the world, there are abundant gas resources which are either physically or economically stranded. These gases include flaring gas in shale oil field, refinery off-gas, coal-bed methane, shale gas in disadvantaged locations. Upgrading of these gases to value-added liquid products could reduce the demand on crude oil by about 20% in the United States.

On-site modular production of value-added products from stranded gases become attractive. Due to economy of scale, modular production typically doesn’t compete well with conventional large scale production. As a result, process intensified modularity becomes important because it will enhance productivity, energy efficiency and flexibility that allows the modular production to be economically viable. What is process intensified modular production? It consists of novel apparatuses and techniques that, compared to those conventionally practiced today, are expected to bring dramatic improvements in manufacturing and processing, substantially decreasing the ratio of equipment size to production capacity. Most importantly, the process intensification should reduce energy consumption, waste production, and ultimately resulting in cheaper and sustainable technologies. Illustrated in this presentation are synergistic integration of the following unit operations: reactor design, heat management and separation. Process intensification sets the foundation for small modular production to achieve both energy efficiency economic production.

Indirect conversion of natural gas to liquid products (GTL) via syngas has been commercialized but it requires huge capital investment, varying from $15 to 20 billion for a 100-140 bbl/d plant. Direct conversion of natural gas without going through syngas route has been under investigation in the past 5 decades, but no commercial processes are practiced to date. A large number of studies have been published on the subject over the past 50 years.

This study emphasizes the direct conversion of short chain parafins (C₁-C₃) into aromatics and olefins using transition metal promoted ZSM-5 zeolite catalysts. Catalyst activity, selectivity, deactivation and regeneration of metal-promoted ZSM-5 zeolite catalysts will be discussed. We will introduce a new approach that employs low temperature plasma to intensify catalytic reaction for natural gas conversion. Under low reaction severity, this approach synergistically integrates plasma reaction chemistry with novel heterogeneous catalysis that decouples methane activation from catalytic surface reaction, shifting rate-determining step from methane activation (cracking C-H bond) to surface C-C formation.

In summary, this presentation illustrates experimental research on direct non-oxidative conversion of natural gas via process intensified production. The challenge in advance the fundamental science aspects presented in direct natural gas conversion is discussed. By comparing with commercial hydrocarbon conversion processes, the industrial perspective on direct methane conversion is illustrated. Specifically, the strategies on the selection of reactor configuration, heat management and catalyst regeneration are highlighted. These commercialization strategies along with technoeconomic analysis are critical for direct natural gas conversion to value-added chemicals.