Distillate Production by Oligomerization of Fischer−Tropsch Olefins over Solid Phosphoric Acid

Abstract

The conversion of Fischer-Tropsch derived olefins over solid phosphoric acid (SPA) is practiced commercially. Although it is mostly used for motor-gasoline production, it is also used to produce distillates to increase refinery flexibility. During distillate production, the distillate yield can be increased by recycling some of the naphtha from the process or by cofeeding naphtha-range Fischer-Tropsch olefins. The SPA catalyzed conversion of Fischer-Tropsch olefins and other olefinic naphtha feed materials was investigated at pilot plant scale in the range of 175-260°C and 3.8 MPa. Contrary to expectations based on propene tetramermode operation, it was found that the distillate yield was limited to 70% when processing olefinic feed mixtures containing propene and naphtha. The weak interaction of long chain olefins with phosphoric acid mechanistically limited distillate production, and naphtha-range olefin oligomerization was disrupted by short chain olefins, like propene, which became the main carbocation source. Inhibition of the oligomerization reaction was also found when processing some of the oxygenate containing Fischer-Tropsch material. A processing methodology could be suggested to improve distillate selectivity by separate processing of the short chain and naphtharange olefins, but no productivity advantage was demonstrated.

Improved THETA-1 for Light Olefins Oligomerization to Diesel: Influence of Textural and Acidic Properties

“…Processes based on silica-supported phosphoric acid (SSPA) have been described for the production of highly branched naphtha range oligomers [4][5][6][7], and are still being operated, despite the numerous drawbacks related to feed hydration level or corrosion, among others [8].…”

An improved solid phosphoric acid catalyst for alkene oligomerization in a Fischer–Tropsch refinery

“…To increase the overall gasoline yield, the FT C 3 -C 5 olefins can be oligomerized over a solid phosphoric acid (SPA) catalyst to produce branched products which have higher octane numbers [2]. The need for an increased overall diesel yield can be addressed by C 3 -C 5 olefin oligomerization operated in the ''tetramer mode'' using SPA as catalyst [3], and the fraction thus produced can then be blended with the high-quality diesel. This provides extra flexibility to respond to changes in market demands with regards to the required gasoline:diesel ratio.…”

Light FCC gasoline olefin oligomerization over a magnetic NiSo4/γ‐Al2o3 catalyst in a magnetically stabilized bed

“…Solid acid catalysts such as zeolites, [8][9][10][11][12] aluminosilicates 13,14 and solid phosphoric acid catalysts 15,16 are all effective catalysts for the olefin oligomerization reaction. Some metal sulfates, including NiSO 4 , CuSO 4 , Zr(SO 4 ) 2 , and Ti(SO 4 ) 2 can generate fairly large numbers of moderate or strongly acidic sites when calcined at 623-973 K and, especially when supported on metal oxides, exhibit excellent catalytic performances in olefin oligomerization.…”