February 27, 2012
Produce benzene and ammonia from natural gas. The US petrochemical industry has regained global competitiveness in ethylene and ethylene derivatives such as polyethylene, poly(vinyl chloride), and monoethylene glycol. This renewed competitiveness stems from the availability of low-cost shale gas. Abundant shale gas gives US petrochemical producers an advantage, but this advantage does not extend to the aromatics value chain because almost all of the world’s aromatics (benzene, toluene, and xylenes) are produced by naphtha-based processes (e.g., reforming and steam cracking) and not from natural gas–based technology.
U. Mueller and H. Freiberger disclose a catalyst and operating conditions that convert natural gas to benzene. Their process also makes the valuable coproduct ammonia when it is carried out in the presence of nitrogen. The catalyst of the invention is based on a zeolite powder with a mordenite framework inverted (MFI) structure. To produce the catalyst, the MFI zeolite is
- treated with NH4NO3, then dried at 120 °C in air;
- treated with Ru(NH3)6Cl3, dried at 120 °C in air, and calcined at 400 °C in helium; and finally
- treated with Mo(CO)6 under vacuum at 130 °C and then at 80 °C.
In an example, 198 g catalyst is formed into a fixed bed in a microflow quartz reactor and gradually heated to 650 °C under flowing helium. At this temperature, the gas flow (25 mL/ min) is changed to a mixture of 58 vol% methane and 42 vol% nitrogen for several hours. [The patent does not specify the time.—Ed.] The ammonia content of the effluent is 10 mg/kg, and the benzene content is 30 mg/kg. No data are given concerning the decline of catalyst activity over time. (BASF [Ludwigshafen, Germany]. US Patent 8,084,658, Dec. 27, 2011; Jeffrey S. Plotkin)