Recently discovered sources of shale gas, along with the technological improvements within the shale gas industry, have greatly increased the supply of natural gas in the United States. However, several challenges have emerged due to these developments, a critical one being the proper utilization of this resource into more valuable and highly demanded products via routes that are both economical and profitable. Since natural gas is the cleanest fossil fuel, these challenges present tremendous opportunities for the proper utilization of methane and have significantly increased interest in C1 chemistry across industries and within academia and government agencies.1To this extent, we propose novel methods for the production of high-value aromatics and olefins from natural gas via methanol. In the mid-2000s, almost all of the approximately 4.5 million metric tons per year of methanol produced in the United States utilized the synthesis gas route.
Conversion of natural gas into methanol as an intermediate for chemicals production is exceptionally promising and remains the most probable route for the widespread commercialization of natural gas based refineries in the United States. Olefins and aromatics are valuable petrochemical products and in high demand. In 2007, the worldwide consumption of ethylene was 115 million tons and the global demand of propylene was 73.5 million tons.2 Between 2005 and 2008, the global demand for benzene, para-xylene, ortho-xylene, and meta-xylene was approximately 40, 26, 6, and 0.4 million metric tons per year, respectively.2Thus, opportunities exist for widespread penetration of natural-gas based chemical refineries, albeit with challenges associated with which types of chemicals to produce and which technologies to invest in.
In this work, we propose a process synthesis superstructure that contains several direct and indirect commercialized natural gas conversion technologies, including autothermal reforming and steam reforming, among others.3,4 To address the economic barriers often associated with the utilization of alternative feedstocks, we develop a novel branch-and-bound global optimization framework that is capable of determining the optimal technologies to produce aromatics and olefins from natural gas at the highest profit.3-5 Several commercialized and promising olefins and aromatics production, upgrading, and separation alternatives are included within this process synthesis framework.6-9 This approach provides an adequate baseline for comparing competing technologies and identifying bottlenecks for natural gas conversion based technologies. Several case studies are presented that explore the effect of refinery capacity and product output. The key topological decisions and analysis of uncertain parameters will be discussed.
1. Mokrani T., Scurrel M. Gas conversion to liquid fuels and chemicals: the methanol route-catalysis and processes development. Catalysis Reviews 2009, 51:1-145
2. de Klerk, A. Fischer-Tropsch Refining; Wiley-VCH Verlag & Co. KgaA: Weinheim 2011
3. Onel, O.; Niziolek, A. M.; Elia, J. A.; Baliban, R. C.; Floudas, C. A. Biomass and natural gas to liquid transportation fuels and olefins (BGTL+C2_C4): Process Synthesis and Global Optimization. Industrial & Engineering Chemistry Research 2014, 54, 359-385.
4. Niziolek, A. M.; Onel, O.; Elia, J. A.; Baliban R. C.; Floudas, C. A. Coproduction of Liquid Transportation Fuels and C6_C8 Aromatics from Biomass and Natural Gas. AIChE Journal 2015, 61, 831-856.
5. Baliban, R. C.; Elia, J. A.; Misener, R.; Floudas, C. A. Global Optimization of a MINLP Process Synthesis Model for Thermochemical Based Conversion of Hybrid Coal, Biomass, and Natural Gas to Liquid Fuels. Computers and Chemical Engineering 2012, 42, 64-86.
6. Niziolek, A. M.; Onel, O.; Hasan, F. M.; Floudas, C. A. Municipal solid waste to liquid transportation fuels – Part II: Process synthesis and global optimization strategies. Computers and Chemical Engineering 2014, 74, 184-203.
7. Niziolek, A. M.; Onel, O.; Elia, J. A.; Baliban, R. C.; Xiao, X.; Floudas, C. A. Coal and Biomass to Liquid Transportation Fuels: Process Synthesis and Global Optimization Strategies. Industrial Engineering & Chemistry Research 2014, 53, 17002-17025.
8. Baliban, R. C.; Elia, J. A.; Floudas, C. A. Novel natural gas to liquids (GTL) technologies: Process synthesis and global optimization strategies. AIChE Journal 2013, 59, 505–531.
9. Baliban, R. C.; Elia, J. A.; Floudas, C. A. Biomass and Natural Gas to Liquid Transportation Fuels: Process Synthesis, Global Optimization, and Topology Analysis. Industrial & Engineering Chem Research 2013, 52, 3381–3406.
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