Properties of Tight Oils and Selection of Catalysts for Hydroprocessing

摘要

Tight oils (TOs) occurring in low-permeability formations are produced by the fracking method. The content of atmospheric distillates (AD) may approach 80% of the TO crude, while that of vacuum residue may be as low as 5%. A waxy behavior of TOs results from a high content of n-paraffins. Blending of TOs and/or TO-derived feeds requires attention because of compatibility issues. Safety precautions must be taken during all stages of the TO handling because of a high content of C-1-C-4 hydrocarbons. Hydroprocessing (HPR) of naphtha from TOs is necessary to increase octane number and that of middle distillates to attain cold flow properties of diesel fuel. HPR of atmospheric residue (AR) from TOs yields additional naphtha and middle distillate feeds. Because of a great variability in properties, the pre-HPR of TO feeds may be necessary. Hydroisomerization (HIS) is the principal reaction during the HPR of AD feeds, while hydrocracking (HCR) and ring opening (RO) are the principal reactions during the HPR of AR from TOs. A wide range of catalyst formulations has been evaluated for conversion of model compounds typical of those present in TOs. High paraffinic feeds such as syncrude from Fischer-Tropsch (FT) synthesis and wax from dewaxing of base oil were tested as well. Bifunctional catalysts comprising acidic supports and noble metals were tested for HIS, HCR, and RO reactions. Conventional HPR catalysts have limited applications because of a low content of sulfur in TO feeds.