Ni catalyst

Diamine. 2,2-Dimethyl-l,3-propanediamine [7328-91-8] (5) has been prepared by amination of neopentyl glycol by treating the glycol with ammonia and hydrogen at 150—250°C at 10—31 MPa (1500—4500 psig) over a Ni catalyst. The diamine is useflil for preparation of crystalline polyureas by reaction with diisocyanates (36). 

H-acid, l-hydroxy-3,6,8-ttisulfonic acid, which is one of the most important letter acids, is prepared as naphthalene is sulfonated with sulfuric acid to ttisulfonic acid. The product is then nitrated and neutralized with lime to produce the calcium salt of l-nitronaphthalene-3,6,8-ttisulfonic acid, which is then reduced to T-acid (Koch acid) with Fe and HCl modem processes use continuous catalytical hydrogenation with Ni catalyst. Hydrogenation has been performed in aqueous medium in the presence of Raney nickel or Raney Ni—Fe catalyst with a low catalyst consumption and better yield (51). Fusion of the T-acid with sodium hydroxide and neutralization with sulfuric acid yields H-acid. Azo dyes such as Direct Blue 15 [2429-74-5] (17) and Acid... 

Amination. Amyl alcohols can react with ammonia or alkylamines to form primary, secondary, or tertiary-substituted amines. Eor example, 3-methyl-butylamine [107-85-7] is produced by reductive ammonolysis of 3-methyl-1-butanol over a Ni catalyst at 150°C (59). Some diisoamyl- and triisoamyl amines are also formed in this reaction. Good selectivities (88%) of neopentyl amine [5813-64-9] are similarly produced by reductive ammonolysis of neopentyl alcohol (60). 

Dehydrogenation ofy -menthadienes and a-piuene ia the vapor phase over catalysts such as chromia—alumina produces y -cymene (70). / -Menthadienes can be disproportionated over a Cu—Ni catalyst to give a mixture of yvmenthane andy -cymene (71). 

Most current industrial vitamin C production is based on the efficient second synthesis developed by Reichstein and Grbssner in 1934 (15). Various attempts to develop a superior, more economical L-ascorbic acid process have been reported since 1934. These approaches, which have met with htde success, ate summarized in Crawford s comprehensive review (46). Currently, all chemical syntheses of vitamin C involve modifications of the Reichstein and Grbssner approach (Fig. 5). In the first step, D-glucose (4) is catalytically (Ni-catalyst) hydrogenated to D-sorbitol (20). Oxidation to L-sotbose (21) occurs microhiologicaRy with The isolated L-sotbose is reacted with acetone and sulfuric acid to yield 2,3 4,6 diacetone-L-sorbose,... 

The l,4-dichloro-2-butene can also be separated and hydroly2ed with aqueous NaOH to form 1,4-butenediol, which is hydrogenated with Ni catalyst to produce 1,4-butanediol. In 1971 this process was commerciali2ed in Japan (55). The plant is now shut down because of unfavorable economics. 

Hydrogenation of trisodium citrate over a Ni catalyst at 8.6 MPa (85 atm) and a temperature of 220—230°C results in hydrogenolysis fragments. 

These reactors for hquids and liquids plus gases employ small particles in the range of 0.05 to 1.0 mm (0.0020 to 0.039 in), the minimum size hmited by filterability. Small diameters are used to provide as large an interface as possible since the internal surface of porous pellets is poorly accessible to the hquid phase. Solids concentrations up to 10 percent by volume can be handled. In hydrogenation of oils with Ni catalyst, however, the sohds content is about 0.5 percent, and in the manufacture of hydroxylamine phosphate with Pd-C it is 0.05 percent. Fischer-Tropsch slurry reac tors have been tested with concentrations of 10 to 950 g catalyst/L (0.624 to 59.3 IbiTi/fF) (Satterfield and Huff, Chem. Eng. Sci., 35, 195 [1980]). 

In the massive state none of these elements is particularly reactive and they are indeed very resistant to atmospheric corrosion at normal temperatures. However, nickel tarnishes when heated in air and is actually pyrophoric if very finely divided (finely divided Ni catalysts should therefore be handled with care). Palladium will also form a film of oxide if heated in air. 

An example of a biphasic, Ni-catalyzed co-dimerization in ionic liquids with weakly coordinating anions has been described by the author s group in collaboration with Leitner et al. [12]. The hydrovinylation of styrene in the biphasic ionic liq-uid/compressed CO2 system with a chiral Ni-catalyst was investigated. Since it was found that this reaction benefits particularly from this unusual biphasic solvent system, more details about this specific application are given in Section 5.4. 

Interestingly, the specific environment of the ionic solvent system appears to activate the chiral Ni-catalyst beyond a simple anion-exchange reaction. This becomes obvious from the fact that even the addition of a 100-fold excess of Fi[(CF3S02)2N] or Na[BF4] in pure, compressed CO2 produced an at best moderate activation of Wilke s complex in comparison to the reaction in ionic liquids with the corresponding counter-ion (e.g., 24.4 % styrene conversion with 100-fold excess of Fi[(CF3S02)2N], in comparison to 69.9 % conversion in [EMIM][(CF3S02)2N] under otherwise identical conditions). 

However, attempts to reuse the ionic catalyst solution in consecutive batches failed. While the products could readily be isolated after the reaction by extraction with SCCO2, the active nickel species deactivated rapidly within three to four batch-wise cycles. The fact that no such deactivation was observed in later experiments with the continuous flow apparatus described below (see Figure 5.4-2) clearly indicate the deactivation of the chiral Ni-catalyst being mainly related to the instability of the active species in the absence of substrate. 

Fig. 8. Relationship between relative reactivities S and the ratios of the initial reaction rates rj°/VA° of alkylphenols to phenol in the hydrogenation on Ni-catalyst containing 8.4% (wt.) AUOa at 160°C and initial molar ratio of hydrogen to organic substances G = 19. Alkyl substituents in phenols Me—methyl, Et—ethyl, Pr—n-propyl, i-Pr— isopropyl, s-Bu—sec-butyl, t-Bu—terc-butyl.

Coordination-catalyzed ethylene oligomerization into n-a-olefins. The synthesis of homologous, even-numbered, linear a-olefins can also be performed by oligomerization of ethylene with the aid of homogeneous transition metal complex catalysts [26]. Such a soluble complex catalyst is formed by reaction of, say, a zero-valent nickel compound with a tertiary phosphine ligand. A typical Ni catalyst for the ethylene oligomerization is manufactured from cyclo-octadienyl nickel(O) and diphenylphosphinoacetic ester ... 

A mechanistic model for propane steam reforming on a bimetallic Co-Ni catalyst in fluidized bed reactor... 

Al/ni, the molar ratio of MAO and Ni catalyst Average rate of polymerization for the period of polymerization. 

Figure 8.4. Transmission electron microscope picture of carbon formation and filament growth on a Si02-supported Ni catalyst after exposure to a CH4 + H2 gas mixture at 1 bar...

Figure 8.7. Steam reforming of n-butane as a function of time for a conventional Ni catalyst and a novel Ni-Au alloy catalyst, showing the superior stability ofthe latter. [Adapted from...

Proven, industrially used catalysts are mostly based on either iron or cobalt. Ruthenium is an active F-T catalyst but is too expensive for industrial use. Both Fe and Co are prepared by several techniques including both precipitation and impregnation of (e.g. alumina or silica) supports. The more noble Ni catalyst produces nearly exclusively methane and is used for the removal of trace of CO in H2. 

Ni catalysts u g ZrOj as a unique support that seems crucial to minimize coking under reaction conditions applied for CH4/CO2 reforming. For two successfiiUy developed catalysts, (Pt and Ni on Z1O2) the present contribution outlines the sequence of the elementary steps and the catalytic chemistry of the active metal and the support in order to explain catalysts activity and stability. 

In contrast to the Pt catalysts discussed above, Ni based catalysts (i.e., also when supported on ZrO usually form coke at such a rapid rate that most fixed bed reactors are completely blocked after a few minutes time on stream (see Fig. 8) [16], The coke formed with the Ni catalysts is filamentous. The Ni particle remaining at the tip of the filament hardly deactivates as the coke formed on its surface seems to be transported through the metal particle into the carbon fibre, but the drastic increase in volume causes reactor plugging and prevents use of the still active catalyst (see Fig. 8). The TEM photographs indicate that the carbon filaments have similar diameters to those of the Ni particles. 

As the metal particle size decreases the filament diameter should also decrease. It has been shown that the surface energy of thirmer filaments is larger and hence the filaments are less stable (11,17-18). Also the proportion of the Ni(l 11) planes, which readily cause carbon formation, is lower in smaller Ni particles (19). Therefore, even though the reasons are diverse, in practice the carbon filament formation ceases with catalysts containing smaller Ni particles. Consequently, well dispersed Ni catalysts prepared by deposition precipitation of Ni (average metal particle size below 2-3 nm) were stable for 50 hours on stream and exhibited no filamentous coke [16]. 

The TPR profiles of the zirconia and silica series are shown in Fig 1 The silica series showed that the sulfated Ni catalysts are more difficult to reduce than the unsulfated ones The position of the maxima shifted 30-50°C to higher temperatures as sulfate was added As opposed to the silica series (see sample 6SSi), the zirconia series exhibited H2 consumption... 

Pyridine compounds 45 can also be produced by the NHC-Ni catalysed cycloaddition between nitriles 43 and diynes 44 (Scheme 5.13) [16]. The SIPr carbene was found to be the best ligand for the nickel complex in this reaction. The reaction required mild reaction conditions and low catalyst loadings, as in the case of cycloaddition of carbon dioxide. In addition to tethered aUcynes (i.e. diynes), pyridines were prepared from a 3-component coupling reaction with 43 and 3-hexyne 23 (Scheme 5.13). The reaction of diynes 44 and nitriles 43 was also catalysed by a combination of [Ni(COD)J, NHC salts and "BuLi, which generates the NHC-Ni catalyst in situ. The pyridines 45 were obtained with comparable... 

Vinyl cyclopropanes tethered to an aUcyne chain 127 were also subjected to the cycloisomerisation reaction in presence of the NHC-Ni catalyst system (Scheme 5.34) [39], The product formation depends on the substrate used and the NHC hgand. When SIPr carbene is used, three different products were obtained depending on the size of the R group attached to the alkyne moiety. If R is small (like a methyl) product 128 is obtained exclusively. If R is Et or Pr a mixture of 128 and 129 is obtained in 3 2 to 1 2 ratio, respectively. However, when R is large groups such as Bu or TMS only product 130 is obtained. When IfBu carbene 131 is used as the ligand, cycloisomerisation of 127 afforded product 128 exclusively, regardless of substituent size (Scheme 5.34) [39]. 

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