Phosphoric silica-supported

As the loading of STA on the catalyst support is decreased, incomplete anhydride conversion is observed and significant hydrolysis of the anhydride to form iso-butyric acid is observed (Table 2). Use of silica supported phosphoric acid results in lower ketone yields and significant hydrolysis of the iso-butyric anhydride. Blank reactions (catalyst and anhydride, 90°C, 30 min) indicates that hydrolysis of anhydride is observed in the presence of these catalysts and may result from either dehydroxylation of the silica support or residual water in the catalyst, ffowever this reaction is slow (42%STA/silica, 44% conversion and 70%P[3PO4/silica, 86% conversion respectively). 

To examine the differences in reactivity of various immobilized palladium pincer catalysts, small molecule, polymer-supported (poly(norbomene) - soluble, and Merrifield resin - insoluble), and silica-supported (SBA-15) pincer complexes were synthesized (Fig. 20.9) [44 6]. Both sulfur-containing (SCS) and phosphorous-containing (PCP) ligands were studied. 

Supports and Catalysts. The preparation of the supports used in this study was discussed in detail elsewhere. The two phosphate supports, A O AIPO and 4MgO lSA O 10A1P0 were co-precipi-tated using the necessary nitrate salts, phosphoric acid, and ammonium hydroxide at a fixed pH (.] ) Niobia was precipitated by adding ammonium hydroxide to a methanolic solution of niobium chloride (8). The niobia-silica support was prepared by impregnating SiO (Davison 952) to incipient wetness with a hexane solution of niobium ethoxide. The sample was then dried and calcined to obtain a homogeneous surface phase oxide (9). 

Cumene is produced by alkylating benzene with propene. The reaction needs a catalyst in recent years, zeolite-based catalysts have become almost universally used in cumene plants [2], although older plants using aluminum chloride (AICI3) or phosphoric acid supported on silica are still operating. 

Short-chain olefin oligomerization can provide gasoline, middle distillate, or lubricant oils. Typical acids used to catalyze these reactions are now solid-type catalysts such as silica-supported phosphoric acids or zeolites. 

Shaterian, H.R., Hosseinian, A., Ghashang, M. 2009. Reusable silica supported poly phosphoric acid catalyzed three-component synthesis of 2H-indazolo[2,l-f>]phthalazine-trione derivatives. ARKLVOC (ii) 59-67. 

The phosphate incorporation in silica supports is often achieved by impregnation with phosphoric acid [8] but in that case, the phosphate ions are only located at the pore surface. In the present work, supports with variable composition in the system Si02 - AlPO - AI2O3 are prepared by coprecipitation of all the support constituant. 

Hashimoto and Mitsutani found that phosphoric acid supported on silica, which were calcined at higher temperature (973—1473 K) had a high activity and selectivity for the preparation of isoprene by the decomposition of 4,4-dimethyl-meta-dioxane (MDO). 

Dehydration of amides is often carried out in the presence of ammonia. Acetonitrile, adiponitrile, and 6-aminocaprolactam ° are formed from acetamide, adipic acid and E-aminocaprolactam over MgiPiO , phosphoric acid supported on silica, and MgHP04, respectively in high yields. o-Chloronitrile can be produced from o-chlorobenzoic acid or its amide over alumina around 623... 

A wide variety of bases, nucleosides and nucleotides have been separated using porous layer bead ion exchangers. A representative chromatogram of the separation of ribonucleoside mono-phosphoric acids from the work of Smukler ( ) is shown in Figure 4. Recently, ion exchangers chemically bonded to small particle diameter (> 10 ym) silica have been successfully applied to the separation of nucleic acid constitutents (37). The rapid separations using such supports undoubtedly mean that they will find increasing use in the future. 

The reactor is a vessel with beds of solid catalyst. Most commercial processes use a catalyst called kieselguhr, which is phosphoric acid deposited on a silica/alumina pellet. Because of the weight of the pellets, supported beds at multiple levels in the vessel are used so the bottom layers wont be crushed.-... 

Ethylene is compressed to 1000 psi, mixed with water, and heated to 600°E The two reactants, both. in, a vapor phase, are fed down a catalyst-filled reactor. The catalyst is phosphoric acid (H3PO4) absorbed onto a porous inert support (usually diatomaceous earth or silica gel). 

Ethylamines. Mono-, di-, and triethyl amines, produced by catalytic reaction of ethanol with ammonia (330), are a significant oudet for ethanol. The vapor-phase continuous process takes place at 1.38 MPa (13.6 atm) and 150—220°C over a nickel catalyst supported on alumina, silica, or silica—alumina.. In this reductive amination under a hydrogen atmosphere, the ratio of the mono-, di-, and triethyl amine product can be controlled by recycling the unwanted products. Other catalysts used include phosphoric acid and derivatives, copper and iron chlorides, sulfates, and oxides in the presence of acids or alkaline salts (331). Piperidine can be ethylated with ethanol in the presence of Raney nickel catalyst at 200°C and 10.3 MPa (102 atm), to give IV-ethylpiperidine [766-09-6] (332). 

---