Catalyst, alumina piperidine

Catalyst, alumina, 34, 79 35, 73 ammonium acetate, 31, 25, 27 copper chromite, 31, 32 36, 12 cuprous oxide-silver oxide, 36, 36, 37 ferric nitrate, hydrated, 31, 53 piperidine, 31, 35 piperidine acetate, 31, 57 Raney nickel, 36, 21 sulfuric acid, 34, 26 Catechol, 33, 74 Cetylmalonic acid, 34, 16 Cetylmalonic ester, 34,13 Chlorination, by sulfuryl chloride, 33, 45 ... 

Catalyst alumina from aluminum isopropoxide with piperidine. 2-B = 2-butanol 2-P = 2-pentanol 3-P = 3-pentanol. 

Temperature, 275" catalyst, alumina from aluminum isopropoxide with piperidine. 

Tetrahydrofurfuryl alcohol reacts with ammonia to give a variety of nitrogen containing compounds depending on the conditions employed. Over a barium hydroxide-promoted skeletal nickel—aluminum catalyst, 2-tetrahydrofurfur5iarnine [4795-29-3] is produced (113—115). With paHadium on alumina catalyst in the vapor phase (250—300°C), pyridine [110-86-1] is the principal product (116—117) pyridine also is formed using Zn and Cr based catalysts (118,119). At low pressure and 200°C over a reduced nickel catalyst, piperidine is obtained in good yield (120,121). 

Ethylamines. Mono-, di-, and triethylamines, produced by catalytic reaction of ethanol with ammonia (330), are a significant outlet 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, siUca, or sihca—alumina. In this reductive amination under a hydrogen atmosphere, the ratio of the mono-, di-, and triethylamine 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 W-ethylpiperidine [766-09-6] (332). 

A refers to alumina prepared from aluminum isopropoxide. A(10% pip.) refers to reaction on catalyst A where the alcohol feed was mixed with 10% by weight of piperidine. B2 refers to alumina prepared from sodium aluminate and washed twice. 

The dehydration of the two alcohols over alumina catalyst in the presence of piperidine was studied by Pillai and Pines [84). The experimental results which are given in Table X indicate that, although carbonium ion mechanism can interpret the products obtained from the tertiary alcohols, another mechanistic path has to prevail in order to account for the formation of the various dehydration products from 3,3-dimethyl-2-pentanol. The mechanism, as proposed above for the dehydration of 3,3-dimethyl-2-butanol, would also explain the hydrocarbons formed from the dehydration of 3,3-dimethyl-2-pentanol. 

Pure alumina catalyst prepared either by hydrolysis of aluminum isopropoxide or by precipitation of aluminum nitrate with ammonia, and calcined at 600-800°, contains intrinsic acidic and basic sites, which participate in the dehydration of alcohols. The acidic sites are not of equal strength and the relatively strong sites can be neutralized by incorporating as little as 0.1 % by weight of sodium or potassium ions or by passing ammonia or organic bases, such as pyridine or piperidine, over the alumina. 

Dibutylamine, piperidine, N-ethylcyclohexylamine, N-ethyldicyclohexylamine, and the ketones were reagent grade chemicals. The 5% palladium on carbon, 5% platinum on carbon, sulfided 5% platinum on carbon and sulfided 5% rhodium on carbon catalysts were obtained from Engelhard Industries. The 20% molybdenum sulfide on alumina (Girdler T-318) was obtained from the Chemetron Corp. Palladium chloride was obtained from Matheson, Coleman and Bell. Ruthenium trichloride was obtained from Ventron. 

The work by Mills et al. (32) includes an early example of catalytic titration behavior. Figure 10 taken from their study shows that cumene cracking at 425°C drops sharply as nitrogen bases are chemisorbed in increasing amounts on silica-alumina catalyst. Base effectiveness decreases in the order quinaldine > quinoline > pyrrole > piperidine > decylamine > aniline. 

Fig. 10. Poisoning effect of amines on cumene cracking over silica-alumina catalyst 1, quinoline 2, quinaldine 3, pyrrole 4, piperidine 5, decylamine 6, aniline (32). (Reprinted with permission of the American Chemical Society.)...

Acid catalysts such as zeolites can be readily poisoned by basic organic compounds. One of the earlier studies of the deactivation of silica-alumina cracking catalysts by organic nitrogen compounds such as quinoline, quinaldine, pyrrole, piperidine, decylamine and aniline was done by Mills et al (6). The results of their partial poisoning studies showed an exponential dependence of the catalyst activity for cumene cracking reaction or... 

Pictet-Spengler cyclization, 161 Pinacol rearrangements, 51 B-(3>a-Pinanyl-9-borabicyclo[3.3.1 ]-nonane, 320-321 Piperidine, 183 Piperidine enamines, 16 Piperidines, 18 Piperonal, 232 Piperylene, 372 N-Pivaloylaniline, 69 Platinum catalysts, 321 Podophyllotoxin, 165 Polygodial, 167 Polymethoxyarenes, 368 Polymethylpyrimidines, 345 Polynucleotides, 88 Polyphosphate ester, 437 Polyphosphoric acid, 321-322 Potassioacetone, 73 Potassium-Alumina, 322 Potassium bis(trimcthylsilyl)amide, 38 Potassium f-butoxide, 323 Potassium carbonate, 323 Potassium-18-Crown-6, 322 Potassium cyanide, 324 Potassium cyclopentadienide, 111 Potassium 2,6-di-f-butyl-4-methylphen-oxide, 48... 

Freifelder el al. found rhodium on carbon to be better suited than rhodium on alumina for reduction of the pyridine ring. The poisoning effect of the piperidine base formed can be overcome by use of sufficient catalyst. 

Fig. 2 a-c shows the activities of the Ir-Mo/alumina sulfide catalysts in HDS of thiophene, HY of pyridine and HDN of piperidine during the parallel HDN/HDS, plotted against Ir amount in the catalysts. It is seen that addition of Ir to the Mo catalyst led to a substantial increase of activity. This increase was about 2 in HDS and about 3 in both steps of pyridine HDN. The data show that an optimum Ir amount in modified catalysts was found between 0.3-0.5 %. Above this Ir content, the activities in HDS and pyridine HY remained almost unaffected while activity in piperidine HDN clearly diminished. This decrease was explained by a diminution of the Ir dispersion, as evaluated from TEM measurements. The mean diameter of the majority of the Ir particles in reduced Ir-Mo sample with 0.53 % Ir was below 0.8 nm and some particles approached 1 nm. On the other hand, when the Ir amount increased to 0.79 %, the mean size of the majority of the particles approached 0.8-1.5 nm and the mean size of some smaller fractions (=>10 %) increased up to 1.5-2.5 nm [11]. 

The advent of rhodium on a support (14) led to its use by other workers from the same laboratory who reduced pyridine to piperidine using an equal weight of 5% rhodium on alumina (15). Investigation of rhodium on carbon in the hydrogenation of a number of pyridines (16) showed it to be effective in a neutral medium when the catalyst ratio is high enough. 

Selective oxidation of primary OH groups in carbohydrate derivatives has been achieved using A -oxoammonium salts generated from (2,2,6,6-tetramethyl-piperidin-l-yl)oxy (TEMPO) and its derivatives as catalysts. The stoichiometric oxidants employed include sodium hypochlorite [48-50], sodium hypobromite [51, 52], and ammonium peroxodisulfate (using silver on alumina as a co-catalyst) [53, 54]. A representative protocol is shown in Scheme 12. 

Rhodium (5%) on carbon is a better catalyst for the reduction of the isomeric pyridinecarboxylic acids, their esters, and amides to the corresponding piperidine analogues than is rhodium on alumina. Reductions are generally slow, but yields are very satisfactory. Catalytic reductions of pyridylalkane... 

In general the reduction of a pyridine side-chain acid or ester using platinum oxide, Raney Nickel, rhodium-on-carbon, rhodium-on-alumina, or ruthenium oxide as the catalyst gives the piperidine acid or ester. Partial reduction of the pyridine ring to a tetrahydropyridine usually occurred when palladium-on-carbon was employed as the catalyst, although two exceptions were reported. Either a mixture of the piperidine and the tetrahydropyridine ester or the tetrahydropyridine ester alone was formed when sodium borohydride was used at room temperature in the reduction of pyridine side-chain ester salts. When the free bases were employed, reduction of the ester group occurred instead of nuclear reduction. The use of lithium aluminum hydride gave the same results (see Table XI-18). Many acetamides... 

Interestingly, simply heating the hydrochloride salts of 1,4-diaminobutane (putrescine) and 1,5-diaminobutane (cadaverine) also provides the corresponding cyclic derivatives. Thus, the former leads to pyrrolidine (azacyclopentane) (Equation 10.55) while the latter produces piperidine (azacyclohexane) (Equation 10.56). In the same vein, the unsaturated heterocychc compound pyrrole (aza-2,4-cyclopentadiene) can also be made by a substitution reaction. Thus, if furan (oxa-2,4-cyclopentadiene, Chapter 8, Scheme 8.102) and atmnonia (NH3) or furan and a primary amine (RNH2) are passed in the vapor phase over an alumina catalyst, pyrrole (aza-2,4-cyclopentadiene) (or an A -substituted pyrrole) forms (Equation 10.57). 

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