Advances in Syngas Production Technologies: Catalysis and Engineering
Progress in Petrochemical Science , Volume 3, pp 1-3; doi:10.31031/pps.2020.03.000567
Abstract: Makarand R Gogate* Independent Consultant for Ch.E Education and Research, India *Corresponding author: Makarand R Gogate, Independent Consultant for Ch.E Education and Research, India Submission: June 05, 2020;Published: August 20, 2020 DOI: 10.31031/PPS.2020.03.000567 ISSN 2637-8035Volume3 Issue4 Methane is the principal constituent of natural gas and constitutes over 90% (v/v) by volume, regardless of the source. Coal, oil, and natural gas have traditionally been the 3 fossil fuels of choice for further conversion and upgrading to fuels and fuel additives, chemicals, and petrochemicals, and for generation of electric power. The advent of “Fracking”, a technology first commercialized in the United States around 2008, made it possible to harvest and recover huge quantities of shale gas and associated gas liquids, trapped within tight pore spaces of shale rock deposits or coal bed methane, considered to be 2 unconventional sources of methane [1-3], other than gas hydrates. The production of domestic natural gas saw a hugh spike in about 2008 (about 1Tnm3) and is expected to grow by up to 44% by 2035. The U.S. is now the world’s largest producer of natural gas, and the cost of natural gas is at about the lowest it has been in over 2 decades, at $1.85/MM BTU. The historical trends in the production and price of domestic natural gas, 1900 onwards to 2020, is shown in Figure 1. Instructively, the hugh spike in the production capacity of natural gas is clearly seen around 2005-2010, which coincides with the advent of new “Fracking” capacity in the United States . Figure 1: Historical trends in price of domestic natural gas, 1900 onwards to 2020 . Not surprisingly, natural gas surpassed coal (in 2007) for the largest installed electricity generation capacity in the United States. In addition, the E.I.A. estimates that the unconventional resource base (primarily shale and coal bed methane) of natural gas is around 65Tnm3, out of which about 5Tnm3 are considered to be “proven” reserves, i.e., recoverable under the current economic and environmental conditions . Natural gas, a versatile fuel feedstock, with a high calorific value - one with the lowest C footprint on account of its highest H:C ratio – is primarily used for electricity generation, and for home heating/cooking applications. More than 90% of U.S. domestic production is burned to create energy, for heating, cooking, and transportation purposes, or for generation of electric power (for residential and commercial use). The use of natural gas as a chemical feedstock for further conversion into fuels/fuel additives, chemicals, and petrochemicals, is still very limited. The reason for this is primarily economic in nature. Most natural gas wellhead locations/deposits are found in remote, inaccessible locations. Natural gas, a vapor under ambient conditions, has a very low mass and volumetric energy density, and is difficult and uneconomical to transport over long distances, using gas pipelines, or even LNG tanker trailers. Unfortunately, thus, apart from conversion to synthesis gas, hydrogen cyanide, acetylene, and chlorinated hydrocarbons, methane conversion pathways are not yet cost-competitive to oil-based fuels and chemicals/petrochemicals. However, natural-gas based indirect liquefaction technologies, based on syngas, offer a critical potential avenue (to reduce our dependence on oil and to reduce the C footprint), for further high-volume growth and market share in syngas-based bulk chemicals. The top 3 chemical products, based on natural gas-based syngas, are, ammonia (worldwide capacity 175MMtpa, 11MMtpa U.S.), methanol (110MMtpa, 4.5MMtpa U.S.), and F.-T.-based synfuels products (over 220,000bpd). While the U.S. capacity of the top-3 chemicals above is still a very small fraction of the worldwide capacity, more than a dozen methanol mega projects are currently in various stages of planning, design, and construction, all along the U.S. gulf coast. Natural-gas based syngas is an ideal feedstock for production of above 3 chemicals, as it affords a stoichiometric inlet H2:CO ratio of 2-2.5, directly possible with both conventional steam reforming and autothermal reforming (ATR), without need for any additional shift conversion [5-8]. In this article, we offer an insightful analysis of the current status of syngas production technologies and assess future projections and forecast for the industry. Steam reforming of natural gas is a conventional and now mature technology, for synthesis of “syngas”, a mixture of CO, CO2, and H2 [9-12]. In steam reforming, CH4 reacts with steam to reform CH4 into a mixture of CO, CO2, and H2, as given below: The synthesis reactions are highly endothermic and thus limited by chemical equilibrium; heat is supplied to the reformer tubes (in a vertical, parallel arrangement), by combustion of natural gas inside a firebox. The product gases leave the reformer unit at 855 oC and 2MPa. In industrial practice, heat is recovered from this gas stream by a series of heat exchange operations. As noted above, only 2 of the 3 reactions above are independent; the H2:CO ratio for the overall product gas is between 2-2.5. The kinetic studies on a commercial Ni/γ-Al2O3 or a ceramic support indicate that it is the reforming of CH4 to CO and the water gas shift reaction that take place under industrial conditions. The dry reforming reaction can also be postulated to occur in the overall series of reactions, as follows : As discussed above, steam reforming of natural gas is a mature process technology, and discussed extensively in several recent reviews [6,7,9-12]. Steam reforming is catalyzed by Group VIII transition metals, including Ru, Rh, Ir, and Ni. While extensive experimental and theoretical studies (DFT calculations, scaling relationships, and microkinetic models) show that Ru and Rh are the most active transition group metals for...
Keywords: Natural Gas / electricity generation / oil / electric power / Petrochemicals / syngas production technologies
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