Ethylene production using a Pd and Ag-Pd-Y-zeolite catalyst in a DC plasma reactor

The interest in natural gas utilization has increased tremendously over the last decade. Natural gas is being looked at as an energy source, as well as a basis for the production of many chemicals. New technologies are needed for smaller scale, remote and niche applications to match many natural gas resources that will not be suitable for large-scale production of distillate products via syngas. Low temperature plasma reactors have been shown to be an effective method for the conversion of methane, and under some conditions have low power consumption. The advantage of low temperature processing potentially reduces the energy intensity of the process and therefore the cost. The feed reactants for this study consist of methane, hydrogen, and oxygen (less than 2.5%). For the do plasma reactor using NaOH-treated Y-zeolite, the primary products are acetylene, hydrogen, and small amounts of carbon monoxide. However, recent efforts have focused on the in situ selective hydrogenation of the acetylene to ethylene. Palladium on a supported catalyst is commonly used in industry for the selective hydrogenation of small amounts of acetylene in the purification of ethylene produced in crackers. The addition of palladium to the NaOH-treated Y-zeolite maintains the same methane conversion (20-60%), but allows for the selective hydrogenation of the acetylene to ethylene. The catalyst is most selective around 45 C, where it produces an ethylene to ethane ratio of about 4-1 with no acetylene. The addition of silver to the Pd-Y-zeolite serves two functions. It increases the ethylene to ethane ratio from 4 to at least 7, and as high as 11. In addition, the temperature at which the high ethylene to ethane ratio achieved is shifted to higher temperatures as well as extended over a wider temperature range. Ethylene yields as high as 30% and hydrogen yields as high as 40% have been obtained without attempting to optimize these yields; and it is expected, based on preliminary results, that higher yields can be obtained. (C) 2003 Elsevier B.V. All rights reserved.