Butene Oligomerization by Phosphoric Acid Catalysis:  Separating the Effects of Temperature and Catalyst Hydration on Product Selectivity

Abstract

Solid phosphoric acid (SPA) catalysts find commercial application in olefin oligomerization and in the alkylation of aromatics with olefins. The composition of strong phosphoric acids, the hydrolysis rate of different phosphoric acid species, and the effect of temperature and hydration (composition of phosphoric acid) on butene oligomerization, as well as two case studies to show these effects on commercial operation in a Fischer-Tropsch refinery, are discussed. It was found that the hydrolysis rate of higher phosphoric acid species is much faster than that of ortho-, pyro-and triphosphoric acids (P1-P3). This implies high hydration sensitivity for SPA catalysts when operated at low hydration levels. The initial product of hydrolysis is P3, and not P1 as previously suggested, indicating additional stability of the triphosphoric acid species, possibly due to intramolecular hydrogen bonding to create a P3 cage structure. Both temperature and the degree of catalyst hydration influence catalysis. The highest yield of the best quality hydrogenated motor gasoline (highest degree of branching) was obtained when operating in a "cold and wet" mode. Decreasing catalyst hydration, irrespective of temperature, increased distillate yield. No benefit was found for "hot and wet" operation. The operating region covered by the study is 150-250 °C and 100-115% H 3 PO 4 .

Catalysis in the Upgrading of Fischer–Tropsch Syncrude

“…63 In an analogous study by de Klerk et al, the effects of temperature and hydration were decoupled to investigate the relative contribution of each on the quality of the product for butene OLI ( Figure 5.6). 64 Thus, Figure 5.6 confirms that the degree of branching in the OLI product is a strong function of temperature, with low temperature favouring increased branching. Branching is less affected by the hydration level of the phosphoric acid, except at low temperatures, where branching is increased by increasing Chapter 5…”

“…Similar behaviour was reported for industrial operation with Fischer-Tropsch alkenes. 64 From Figure 5.6, it is also clear that catalyst hydration affects the mechanism independently. Catalyst hydration refers to the dynamic response of the SPA catalyst to changes in the water partial pressure that affects the phosphoric acid species present on the catalyst surface.…”

Transformation of Sorbitol to Biofuels by Heterogeneous Catalysis: Chemical and Industrial Considerations

“…The feeds for these processes are mixtures of short olefins that can be obtained from polyols by dehydration of alcohols or by dehydrogenation of paraffins. The oligomerisation process converts olefins into basic jet fuel or gasoline fuels in the presence of acidic catalysts such as Supported Phosphoric Acid (SPA) or amorphous silica alumina [116,117]. The use of zeolite catalysts allows production of medium distillates.…”

Fischer–Tropsch Syncrude

“…A more detailed analysis of the C 4 fraction is given in Table 4.3. 31 The composition of this fraction is consequently dependent on the amount of propene recovered. The Condensate 1 stream and C 5 /C 6 SLO (light naphtha) have an overlapping carbon number distribution, but the SLO light naphtha contains much more oxygenates.…”