Direct conversion of natural gas to a green alternative fuel to diesel for power generation

O. Marin-Flores, S. Ha, M.G. Norton
Washington State University,
United States

Keywords: natural gas conversion, dimethyl ether, diesel, power generation

Summary:

The oil & gas (O&G) industry, which is the most energy-intensive of all industrial processes, has a great potential for efficiency improvements. The O&G is currently consuming about 20% of its output for its own process needs. Moreover, energy efficiency of O&G Exploration & Production (E&P) is low by any standards, as it hardly reaches 20%. For instance, approximately 110 billion cubic meters of natural gas gets flared/vented in O&G rigs annually worldwide contributing not only to an energy loss of ~$16 billion but also to a significant increase in greenhouse gas emissions with the subsequent severe negative impacts on the environment. Numerous efforts have been undertaken by major O&G companies to improve the efficiency from drilling, through extraction and crude product transportation, and final processing and refining. Making use of the advances in drilling technologies has been recognized as a potential factor to increase oilfield production capacities and cost-effectiveness. Energy needs on drilling rigs are usually supplied by diesel engines, which typically use 20–30 m3 diesel fuel per day, depending on the operations performed. However, the expenses associated to the amount of fuel required by O&G rigs could be attenuated by converting the natural gas wasted into an alternative fuel to efficiently run diesel engines. Dimethyl ether (DME) is a clean-burning and non-toxic renewable fuel. Its high cetane value (55-60) and quiet combustion make it an excellent inexpensive diesel alternative that meet strict emissions standards. DME has been used for decades as an energy source in China, Japan, Korea, Egypt, and Brazil. Our technology is aimed at increasing the energy efficiency in the O&G industry by using the flared/vented natural gas to produce DME, an alternative green fuel to be used in power generators to thus meet the energy demands from O&G drilling rigs. To achieve this goal, we have developed a proprietary catalytic material that can directly convert methane into DME as primary oxygenated compound, under mild conditions of pressure and temperature. Figure 1 shows a TEM image of the nanostructured catalytic material, with nanoparticles of the active phase (~2-5 nm) highly dispersed on the catalyst carrier. The particular activity of our catalytic material is attributed to a synergistic effect between the acidic and metallic sites present on the surface of the catalytic material, which lead to the formation of appropriate intermediates species that eventually gives rise to the reaction products. Figure 2 shows a typical performance of the catalytic material at atmospheric pressure and within the temperature range 200-450°C. As observed two main oxygenated compounds can be detected, DME and formaldehyde, with the former being the more abundant one. With this technology it will be feasible to construct compact reactor modules for the onsite generation of DME using natural gas as starting material. In doing so, we should be able to increase the energy efficiency of the drilling process and produce savings of up to ~1,000,000 $/yr per rig, while minimizing harmful emissions to the environment.