Solid acidities

Phosphonic acid, H3PO3, often called just phosphorous acid , is prepared by the hydrolysis of phosphorus trichloride a stream of air containing phosphorus trichloride vapour is passed into ice-cold water, and crystals of the solid acid separate ... 

Corrosive liquids and solids (acids, acid chlorides, etc.) are easily manipulated, and no impurities are introduced into the product from the apparatus. 

Acids are not limited to liquid (or gaseous) systems. Solid acids also play a significant role. Acidic oxides such as silica, silica-alumina, etc. are used extensively as solid acid catalysts. New solid acid systems that are stronger than those used conventionally are frequently called solid superacids. 

Many superacid-catalyzed reactions were found to be carried out advantageously not only using liquid superacids but also over solid superacids, including Nafion-H or certain zeolites. We extensively studied the catalytic activity of Nafion-H and related solid acid catalysts (including supported perfluorooctanesulfonic acid and its higher ho-... 

To explain how solid acids such as Nafion-H or HZSM-5 can show remarkable catalytic activity in hydrocarbon transformations, the nature of activation at the acidie sites of such solid acids must be eon-sidered. Nafion-H contains acidic -SO3H groups in clustered pockets. In the acidic zeolite H-ZSM-5 the active Bronsted and Tewis acid sites are in close proximity (—2.5 A). 

Solid acid catalyst Solid bridges Solid carbon dioxide... 

K. Tanabe, Solid Acids and Bases, Kodansha, Tokyo, 1976, p. 1. 

J. Chen, CDTECHAromaticA/ /ation Technologies, Worldwide Solid Acid Process Conference, Houston, Tex., Nov. 14,1993. 

Slotted plate for catalyst support designed with openings for vapor flow Ion exchanger fibers (reinforced ion exchange polymer) used as solid-acid catalyst None specified Hydrolysis of methyl acetate Evans and Stark, Eiir. Pat. Appl. EP 571,163 (1993) Hirata et al., Jap. Patent 05,212,290 (1993)... 

Dissolve in distilled H2O and acidify with dilute HCl to pH 3.5. Filter off the solid acid and wash well with H2O. Redissolve ca lOg in 300mL H2O containing 12g of NaOAc. Ppte again by adding HCl, filter and wash with H2O. Add the solid to 200mL of EtOH stir for Ih and filter. Repeat the EtOH wash and dry the bright yellow solid in a vacuum. This acid decomposes on heating at ca 180°. See below for the prepn of the Na salt. [Anal Chem 28 882 1956]. 

Reaction of 1 mole of aminals 352 with 4 mol of methyl 3-aminocrotonate in the presence of the solid acids montmorillonte clay (Kio) and ZF520 zeolite as strong Bronsted acidic catalysts, gave 1,4-dihydropyridines 353 and 2-methyl-4//-pyrido[l, 2-n]pyrimidin-4-one (99MI8). 

The apparatus employed in the preceding experiment is used. To 600 g of 98% sulfuric acid at O " (ice-salt bath) is added about 3 ml of 88 % formic acid. When the rapidly stirred solution becomes foamy with evolution of carbon monoxide, 50 g of decahydro-2-naphthol and 100 g of 88% formic acid are added from two dropping funnels over 3 hours. During the addition, the temperature is kept below 5° the mixture continues to foam. Work-up as for the cis acid gives about 85% of solid acid, predominantly trans. After three recrystallizations from acetone, about 7 g of the pure acid is obtained, mp 135-136°. 

On oxidation the glycol yields a dibasic acid, CjgHjgO, called ascaridolic acid (melting-point, 116-5° to 117° C.), and another solid acid, melting at 186° to 187° C., to which Nelson attributes the formula... 

Inspired by the separation ability of cyclic selectors such as cyclodextrins and crown ethers, Malouk s group studied the synthesis of chiral cyclophanes and their intercalation by cation exchange into a lamellar solid acid, a-zirconium phosphate aiming at the preparation of separation media based on solid inorganic-organic conjugates for simple single-plate batch enantioseparations [77-80]. 

Both sulfuric acid and hydrofluoric acid catalyzed alkylations are low temperature processes. Table 3-13 gives the alkylation conditions for HF and H2SO4 processes. One drawback of using H2SO4 and HF in alkylation is the hazards associated with it. Many attempts have been tried to use solid catalysts such as zeolites, alumina and ion exchange resins. Also strong solid acids such as sulfated zirconia and SbFs/sulfonic acid resins were tried. Although they were active, nevertheless they lack stability. No process yet proved successful due to the fast deactivation of the catalyst. A new process which may have commercial possibility, uses... 

The reaction occurs in the liquid phase at relatively low temperatures (about 50°C) in the presence of a solid acid catalyst. Few side reactions occur such as the hydration of isohutene to tertiary hutyl alcohol, and methanol dehydration and formation of dimethyl ether and water. However, only small amounts of these compounds are produced. Figure 5-8 is a simplified flow diagram of the BP Etherol process. 

D.G. Barton, M. Shtein, R.D. Wilson, S.L. Soled, and E. Iglesia, Structure and Electronic Properties of Solid Acids Based on Tungsten Oxide Nanostmctures, J. Phys. Chem. 103(4), 630-640 (1999). 

Industrial Engineering Chemistry Research 34, No.12, Dec.1995, p.4514-9 CHEMICAL RECYCLING OF WASTE PS INTO STYRENE OVER SOLID ACIDS AND BASES... 

As a further illustration of the compensation effect, we use solid-acid-catalyzed hydrocarbon activation by microporous zeolites. A classical issue in zeolite catalysis is the relationship between overall rate of a catalytic reaction and the match of shape and size between adsorbate and zeolite micropore. 

The center of the line is located at 126 ppm. The shape and position of the lines are comparable to those observed in the spectra of pyrogenic deposits (sp -hybridized carbon), for example, in coked catalysts where carbon is produced during the deactivation of solid acid catalysts [30, 31]. 

K. Tanabe and WF. Holderich, Industrial Applications of Solid Acid-Base Catalysts , Applied Catalysis A, General, 1999, 181, 399. 

Figure 1 shows the methyl ester yield as a function of the reaction time for the transesterification of cottonseed oil catalyzed by the solid bases and acids. Of the solid bases, CaO and Mg0-Al203 were more effective for this reaction. Over 90% methyl ester was obtained in less than 3 hours. The reactions catalyzed by the solid acids were slower than that by the solid bases, which need about 9 hours to reach high concentration of ME. The different plateau values of the solid bases may be caused by the deactivited of the catalysts. 

Proceedings of the Annual International AlChE Meeting, Washington, DC, November 27-December 2, 1988 edited by M.L. Occelli and R.G.Anthony Volume 51 Mew Solid Acids and Bases.Their Catalytic Properties... 

Solid acids can also be prepared from these materials by transformation of the sulphur group to the sulphonic acid, very closely related to sulphuric acid, one of the most commonly used acids industrially. The material can be easily recovered and easily handled since the acidity resides within pores, it cannot come into contact with living tissue. Important transformations, such as the formation of synthetic lubricants and intermediates for fragrances, have already been reported using these materials. The scope for such materials in future is enormous. 

Zeolites are used in various applications such as household detergents, desiccants and as catalysts. In the mid-1960s, Rabo and coworkers at Union Carbide and Plank and coworkers at Mobil demonstrated that faujasitic zeolites were very interesting solid acid catalysts. Since then, a wealth of zeolite-catalyzed reactions of hydrocarbons has been discovered. Eor fundamental catalysis they offer the advantage that the crystal structure is known, and that the catalytically active sites are thus well defined. The fact that zeolites posses well-defined pore systems in which the catalytically active sites are embedded in a defined way gives them some similarity to enzymes. 

The major disadvantage of the alkylation process is that acid is consumed in considerable quantities (up to 100 kg of acid per ton of product). Hence, solid acids have been explored extensively as alternatives. In particular, solid super acids such sulfated zirconia SO/ IZr02) show excellent activities for alkylation, but only for a short time, because the catalyst suffers from coke deposition due to oligomerization of alkenes. These catalysts are also extremely sensitive to water. 

Another recent new application of a microporous materials in oil refining is the use of zeolite beta as a solid acid system for paraffin alkylation [3]. This zeolite based catalyst, which is operated in a slurry phase reactor, also contains small amounts of Pt or Pd to facilitate catalyst regeneration. Although promising, this novel solid acid catalyst system, has not as yet been applied commercially. 

A non-acidic isomerization catalyst system has unexpectedly emerged from recent studies by French workers [4] in the area of Mo-oxycarbides. Although at an early stage of development, these new materials exhibit high selectivities for the isomerization of paraffins such as n-heptane. An alternative non-carbenium ion mechanistic route to achieve isomerization of higher alkanes could potentially overcome some of the limitations of conventional solid acid based catalyst systems. 

K.Tanabe, Solid Acids and Bases, Academic Press, New York, 1970 Catalysis by Acids and Bases(B.Imelik, C.Naccache, G.Couduier, YBen Taarit and J.C. Vedrine eds.), Elsevier, Amsterdam, 1984, p.l. 

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