January 24, 2011
Catalytically crack naphtha with little coke formation. A long-time goal of industry has been to produce ethylene and propylene by catalytically cracking hydrocarbon feedstocks. Almost all of the world’s ethylene and ~60–65% of the world’s propylene comes from noncatalytic steam cracking. A challenge to developing a catalytic method is the high temperatures needed to overcome the inherent thermodynamics of the required reactions. At these temperatures, there is a propensity to form coke, which coats catalyst surfaces and kills their activity.
J.-h. Kang and co-inventors disclose a catalyst system that gives higher yields of ethylene and propylene than are achieved with noncatalytic naphtha steam cracking and keeps coke formation to a minimum. The optimum catalyst described in the patent contains 20 wt% KMgPO4 supported on α-Al2O3.
In an example of the process, naphtha and water (2:1 wt ratio) are passed over the catalyst in a quartz tube reactor at 880 °C and a naphtha flow rate equivalent to a liquid hourly space velocity of 10 h–1. Ethylene and propylene yields are 31.6 and 17.1%, respectively, with only 0.67 wt% coke formation on the catalyst. Under the same conditions but without the catalyst, ethylene and propylene yields are 23.9 and 12.3%.
This invention has the potential to improve the production economics of these two olefins. The key to commercializing the process will be to demonstrate sufficient catalyst activity over time. (LG Chem [Seoul] and LG Petrochemical [Jeollanam-Do, Korea]. US Patent 7,863,494, Jan. 4, 2011; Jeffrey S. Plotkin)