Solid phosphoric acid catalyst

The transportation fuels produced and marketed (Table 18.9)40 met the South African fuel specifications of that time and included some coal-derived liquids (not shown in Figure 18.5). Although the refinery originally produced no jet fuel, it was demonstrated that the hydrogenated kerosene range oligomers from olefin oligomerization over a solid phosphoric acid catalyst met the requirements for jet fuel.38 (Semisynthetic jet fuel was approved in 1999 and fully synthetic jet fuel was approved in 2008 DEFSTAN 91-91/Issue 6). 

Much ethanol is manufactured by the hydration of ethene. The reaction is an addition reaction between steam and ethene at 300 °C, in the presence of a solid phosphoric acid catalyst, at a pressure of about 70 atmospheres. 

Cumene is produced by an alkylation reaction, and most cumene has been produced over solid phosphoric acid catalyst, although some quantities have been produced by liquid phosphoric acid and aluminum chloride. Cumene is used as a raw material for the production of phenol and acetone by oxidation. 

Figure 3 shows a flow diagram of a unit for the production of ethylbenzene using aluminum chloride catalyst, and Fig. 4 shows a flow diagram of a similar unit employing solid phosphoric acid catalyst. 

Fig. 4. Typical ethylbenzene unit with solid phosphoric acid catalyst.

The most important chamber type alkylation units are the UOP type using solid phosphoric acid catalyst for making cumene and ethylbenzene... 

Reaction time is interrelated with catalyst activity and, within limits, to operating pressure. The Solid Phosphoric Acid catalyst is the most ac-... 

The Solid Phosphoric Acid catalyst is produced from a controlled mixture of liquid phosphoric acid and kieselguhr. The catalyst is white or gray cylindrical-shaped pellets. It is hard when dry but picks up water on exposure to moist air for extended periods of time. 

Early commercial units utilized 10- to 20-mesh quartz but, because of the low surface area and consequent low activity of the catalyst, the quartz size was reduced to 28 to 35 mesh. The quartz is activated by pumping the reactor full of 75% phosphoric acid, allowing the excess acid to drain out, and then charging hot hydrocarbon to the unit. Even with the smaller quartz particles the catalyst activity is much lower than that of the Solid Phosphoric Acid catalyst. This lower activity has resulted in lower olefin conversion in this type of unit. Increased conversion has been obtained by separating the olefins from the product with very efficient fractionators and returning them to the reactor. However, this factor requires relatively large units with high utility consumption. 

Oligomerization of butene over HMordenite has been carried out at 5 MPa and 523 K. The reaction gave mainly dimers and trimers with a minor fraction of tetramers and pentamers.[13] In contrast, oligomerization of butene over solid phosphoric acid catalyst gave mainly dimers. 

Cumene manufacture consumed about 10 percent (2.2 billion lb) of the propylene used for chemicals in the United States in 1998. It is prepared in near stoichiometric yield from propylene and benzene with acidic catalysts (scheme below). Many catalysts have been used commercially, but most cumene is made using a solid phosphoric acid catalyst. Recently, there has been a major industry shift to zeolite-based catalyst. The new process has better catalyst productivity and also eliminates the environmental waste from spent phosphoric acid catalyst. It significantly improves the product yield and lowers the production cost. Cumene is used almost exclusively as feed to the cumene oxidation process, which has phenol and acetone as its coproducts. 

Polymerization units use phosphoric acid as a catalyst in the reactor. Because solid phosphoric acid catalysts do not cause corrosion, carbon steel can be used. However, liquid phosphoric acid is very corrosive to carbon steel, so corrosion resistant materials are required. At a phosphoric acid concentration of 100%, type 304L SS is satisfactory up to 120 F (50 C), and type 316L SS is required from 120 to 225°F (50 to 107°C). 

In the case of cumene, UOP introduced a liquid-phase process in the 1940s to compete with aluminum chloride technology. The catalyst is SPA, a solid phosphoric acid catalyst in which the phosphoric acid is supported on silica. Many improvements were made to the SPA catalyst and process over the years, leading to 70% of the world s cumene being produced with SPA by the 1990s. In 1996, UOP introduced the Q-Max process, featuring a zeolitic catalyst and operating in the liquid phase (21). A new Q-Max catalyst, QZ-2001 , was introduced in 2001. 

Wet compounding is another way to hasten the formation of a solid solution. In this method, a homogenous solution or a colloidal solution containing active components of the catalyst is mixed with other components of the catalyst in solid form. The reaction between solution and solid is activated by vigorous mixing and subsequent calcination. Solid phosphoric acid catalyst for hydrocarbon polymerization is prepared by this method. ... 

The continuous increase of isoprene demand has determined the enhancement of researches focused on the elaboraticxi of new and efficient routes for the industrial synthesis of this valuable diene. The acid-catalyzed cc ensation of formaldehyde and isobutene, known as Prins reacticxi, is already a recognized industrial route for the isoprene synthesis, being applied as two-stages process, condensation to form 4,4-dimethyl-l,3-dioxane in the presence of an aqueous sulphuric acid and its decomposition to isoprene using solid phosphoric acid catalysts. 

Ipatieff developed the solid phosphoric acid catalyst which has been employed for... 

The catalyst can be deactivated by the modification of the acid components if it does not contain the proper amount of water.Excessive water causes the catalyst to get soft and the pellet to collapse, increasing the pressure drop in the bed. Too little water dehydrates the phosphoric acid to inactive polyphosphoric aeids therefore small quantities of water are added to the reaction mixture to maintain the optimum degree of hydration. 350 — 400 ppm H2O is the range for 473 — 593 K. The solid phosphoric acid catalysts are not easily regenerable. 

Solid phosphoric acid catalysts are also used for producing isopropylbenzene from a mixture of benzene and a refinery stream containing propene and propane. The carbonylation of alkenes and the hydration of olefins are also effected by supported phosphoric acid. 

The hydration of oleflns is important for the direct synthesis of alcohols from olefins in the pietroleum industry and has been extensively studied over various solid acid catalysts. In the case of ethanol synthesis from ethylene and water, silicotungstic acids, silicophosphoric acids, solid phosphoric acids, metal sulfates, " and metal oxides have been studied as solid acid catalysts. In its industrial process, a solid phosphoric acid catalyst (Shell patent) is widely used throughout the world. The nature of the active (acidic) sites which exhibit high catalytic activity and selectivity is discussed below together with the hydration mechanism involving the catalytic behavior. 

Isobutylene polymerization (solid phosphoric acid) catalyst ... 

---