Propylene acidic promoters

Ghlorohydrination with Nonaqueous Hypochlorous Acid. Because the presence of chloride ions has been shown to promote the formation of the dichloro by-product, it is desirable to perform the chlorohydrination in the absence of chloride ion. For this reason, methods have been reported to produce hypochlorous acid solutions free of chloride ions. A patented method (48) involves the extraction of hypochlorous acid with solvents such as methyl ethyl ketone [78-93-3J, acetonitrile, and ethyl acetate [141-78-6J. In one example hypochlorous acid was extracted from an aqueous brine with methyl ethyl ketone in a 98.9% yield based on the chlorine used. However, when propylene reacted with a 1 Af solution of hypochlorous acid in either methyl ethyl ketone or ethyl acetate, chlorohydrin yields of only 60—70% were obtained (10). 

Isopropyl Ether. Isopropyl ether is manufactured by the dehydration of isopropyl alcohol with sulfuric acid. It is obtained in large quantities as a by-product in the manufacture of isopropyl alcohol from propylene by the sulfuric acid process, very similar to the production of ethyl ether from ethylene. Isopropyl ether is of moderate importance as an industrial solvent, since its boiling point Hes between that of ethyl ether and acetone. Isopropyl ether very readily forms hazardous peroxides and hydroperoxides, much more so than other ethers. However, this tendency can be controlled with commercial antioxidant additives. Therefore, it is also being promoted as another possible ether to be used in gasoline (33). 

Over An deposited on 3-D mesoporous Ti-Si02 with pore diameter of 9nm, one of the best results was obtained. At an SV of 4000 h/mL/g-cat., propylene conversion above 8%, PO selectivity of 91% giving a steady STY of 80 g PO/h/kg-cat. [84]. The surfaces of 3-D mesoporous Ti-Si02 were trimethylsilylated for rendering hydro-phobicity, which enables higher temperature operation of reaction [86]. As a solid phase promoter, alkaline or alkaline earth metal chlorides are efficient, however, chloride anions markedly enhance the coagulation of An particles in a short period [87]. Finally, Ba(N03)2 was selected as the best promoter which might kill the steady acid sites as BaO (after calcination) on the catalyst surfaces [84,88]. 

Alkymax A process for removing benzene from petroleum fractions. They are mixed with light olefin fractions (containing mainly propylene) and passed over a fixed-bed catalyst, which promotes benzene alkylation. The catalyst is solid phosphoric acid (SPA), made by mixing a phosphoric acid with a siliceous solid carrier, and calcining. Invented in 1980 by UOP... 

In alkylation of benzene with both ethylene and propylene di- and polyalkylates are also formed. In alkylation with propylene 1,2,4,5-tetraisopropylbenzene is the most highly substituted product steric requirements prevent formation of penta-and hexaisopropylbenzene. On the other hand, alkylation of benzene with ethylene readily even yields hexaethylbenzene. Alkylation with higher alkenes occurs more readily than with ethylene or propylene, particularly when the alkenes are branched. Both promoted metal chlorides and protic acids catalyze the reactions. 

Alkylation processes usually combine isobutane with an alkene or with mixed alkene streams (C3-C5 olefins from FCC units). The best octane ratings are attained when isobutane is alkylated with butylenes. Alkylation of higher-molecular-weight hydrocarbons (>C5) is less economic because of increased probability of side reactions. Phillips developed a technology that combines its triolefin process (metathesis of propylene to produce ethylene and 2-butenes) with alkylation since 2-butenes yield better alkylate than propylene.290 Since ethylene cannot be readily used in protic acid-catalyzed alkylations, a process employing AICI3 promoted by water was also developed.291... 

Lewis and protic acids, usually AICI3 and H2SO4, are used in the liquid phase at temperatures of 40-70°C and at pressures of 5-15 atm. Phosphoric acid on kieselguhr promoted with BF3 (UOP process)309 319 is used in gas-phase alkylation (175-225°C, 30-40 atm). In addition to the large excess of benzene, propane as diluent is also used to ensure high (better than 94%) propylene conversion. This solid phosphoric acid technology accounts for 80-90% of the world s cumene production. 

Acrolein and Acrylic Acid. Acrolein and acrylic acid are manufactured by the direct catalytic air oxidation of propylene. In a related process called ammoxida-tion, heterogeneous oxidation of propylene by oxygen in the presence of ammonia yields acrylonitrile (see Section 9.5.3). Similar catalysts based mainly on metal oxides of Mo and Sb are used in all three transformations. A wide array of single-phase systems such as bismuth molybdate or uranyl antimonate and multicomponent catalysts, such as iron oxide-antimony oxide or bismuth oxide-molybdenum oxide with other metal ions (Ce, Co, Ni), may be employed.939 The first commercial process to produce acrolein through the oxidation of propylene, however, was developed by Shell applying cuprous oxide on Si-C catalyst in the presence of I2 promoter. 

Post-synthesis alumination using A1(N03)3 as the precursor improves the acidity of siliceous MCM-41 materials significantly. FTIR results show that both Bronsted and Lewis acid sites are increased upon alumination. The number of acid sites increases with the Al content on MCM-41. NH3-TPD reveals the mild strength of these created acid sites. Due to the improved acidity, the catalytic activity for dehydration of isopropanol to propylene over these alumina-modified MCM-41 materials is considerably promoted by post-synthesis alumination. The results of XRD and N2 adsorption show that the enhancement of acidity for siliceous MCM-41 by postsynthesis alumination does not cause any serious structural deformation of the resulting material. 

Considerable effort has been put into minimizing the adverse effects of these olefins. It was found that alkylating propylene and pentylenes in a mixture with butylenes promoted the desired reactions and reduced the octane and acid consumption penalties. Furthermore, by optimizing temperature, isobutane-to-olefin ratio, acid strength, and other variables, the deleterious effects of propylene and pentylenes in the feed can be minimized (4, 8, 21). The decision as to how much of these olefins to include in the alkylation unit feed depends on many different factors, such as their value relative to alkylate, butylene and isobutane avails, alkylate volume and octane requirements, acid costs, etc. 

Consequently, stronger solid acids were needed to activate the ethylation reaction. The solid acids that were available earlier exhibited only limited acidity, which was sufficient to promote the propylation of benzene with propylene at reasonable temperatures and pressures, but it was not high enough to promote ethylation of benzene with ethylene under similar conditions. 

Improvement of Au/3-D mesoporous Ti-Si02 As for propylene epoxidation, alkaline or alkaline earth metal chlorides were efficient solid-phase promoters however, chloride anion markedly enhanced the coagulation of Au particles [147]. For Au/3D Ti-Si02, Ba(N03)2 was the best solid-phase promoter, which might be transformed into BaO after calcination at 573 K and might function by neutralizing acid sites on... 

In propylene epoxidation catalyzed by trimethylsilylated Au-Ba(N03)2/Ti-Si02, the introduction of the gas promoter trimethylamine (13-15 ppm) to the reactant gas stream appreciably improved catalytic performance [149] (Figure 3.20). Surprisingly, trimethylamine made the used catalysts better than fresh catalysts in catalytic performance. Possible reasons are (i) trimethylamine might destroy the mobile acid sites that appear and disappear intermittently, suppressing by-product formation from PO (ii) trimethylamine can also adsorb on the surfaces of Au and depress the combustion of H2 to form H20, thus leading to improved H2 utilization efficiency. 

---