Raney Copper Catalysts Research Articles

Modelling the development of pore structure during the preparation of raney copper catalysts for fixed bed operation

The pore structure and surface area of Raney copper pellets, partially leached at 50°C, have been predicted using a combination of phase transformation theory for the initial leaching and a dissolution-reprecipitation mechanism for the coarsening of the structure. Good agreement was found between the calculated and experimental surface areas of the pellets. The coarsening process results in the high surface area material initially formed at the external surface of the pellet being converted to a coarsely porous structure. This decreases the activity of the material but may have an advantage in reducing the extent of fouling by polymer by-products in several industrial processes.

A comparison of Raney copper-zinc and coprecipitated copper-zinc-aluminium oxide methanol syntheses catalysts

A Raney catalyst prepared from an alloy consisting of 43 wt.% copper, 39 wt.% aluminium and 18 wt.% zinc and a commercial copper oxide-zinc oxide-alumina catalyst were tested in methanol synthesis in the temperature range 430–530 K, using a GHSV of 10000 h −1, and constant total pressure of 5000 kPa. Total carbon oxide concentration in the synthesis gas was in the range 15–20 vol.%. It was found that the catalysts had the same activity per unit area of copper and showed almost identical responses to changes in process conditions despite the different morphologies resulting from the methods of catalyst preparation. A Raney copper catalyst, prepared from CuAl 2 and containing less than 1% of residual aluminium, was found to be active in methanol synthesis. The results suggest that the same active species are involved in methanol synthesis in both types of catalyst, and that these active species involve copper metal.

Catalysis by amorphous metal alloys. Part 3.—Catalytic activity of raney copper catalysts prepared from amorphous Cu62Zr38 powder

Raney-type copper catalysts were prepared by treating the pulverized amorphous and crystalline Cu62Zr38 alloys with dilute HF. The catalytic activity for the hydrogenation of olefins was much greater with the catalyst from the amorphous alloy. The great enhancement of the activity of this catalyst was ascribed to its porous structure, the high surface concentration of copper, the high frequency of the distribution of active sites and the electronic state of the surface site, which were clarified by studies of the surface states using ESCA, XRD, SEM and carbon monoxide chemisorption techniques.

Hydrolysis of acrylonitrile over incompletely leached raney copper catalysts

The hydrolysis of acrylonitrile has been studied over catalysts prepared by caustic leaching of 2.0 to 2.3 mm particles of a Cu-50.2 wt % Al alloy at 313 K for periods between 40 minutes and 24 hours. Initial rate measurements showed that the copper surface is most effectively used in the hydrolysis reaction when the alloy is only slightly leached (to a depth of ca. .85 mm). With increased leaching the rate of reaction per unit copper surface decreased due to increased diffusional resistance in the thicker catalyst rim. The rate of catalyst deactivation decreased with increasing rim thickness due to the mechanism of fouling and the observed increase in pore diameter with increased time of leaching.

KINETICS OF THE HYDROLYSIS OF ACRYLONITRILE TO ACRYLAMIDE OVER RANEY COPPER

Measurements of the kinetics of the hydrolysis of acrylonitrileover Raney copper catalysts have been made in the temperature range 40 to 100°C in a tubular reactor operated differentially with and without recycle and over concentration ranges of 0-25 weight percent acrylonitrile, 0-35 weight percent acrylamide and 40-99 weight percent water. For the concentration range 0 to 7 wt. % acrylonitrile and 0 to 7 wt. % acrylamide, data were fitted by an adsorption model of the type A + K,CA + KCCC and at higher concentrations by the powers law expression The activation energy for the reaction was found to be 49.2kJmol−1. Both models showed that the product acrylamide strongly inhibits the reaction.

Structural and reactivity effects in the copper-catalyzed hydrogenolysis of aliphatic esters

The hydrogenolysis of a series of alkyl esters to their corresponding alcohols has been studied over a Raney copper catalyst in the temperature range 210–280 °C. Generally, the rate of hydrogen-olysis was found to increase with molecular weight while the selectivity to alcohol, derived from the acyl part of the ester, decreased due to transesterification reactions. The rate data correlated well to a Taft equation in which inductive effects were more important than steric effects, provided the equation included a term to account for the hydrogens on the α-carbon atoms. Reaction kinetics for ethyl acetate hydrogenolysis were found to be first order in hydrogen and −0.5 order in ethyl acetate.

Pore structure of raney copper according to adsorption and mercury porosimetry

Raney copper catalysts have been reacted with nitrous oxide at 200°C. An oxygen uptake of equivalent to four monolayers was found to be sufficient to passivate the catalyst. Pore volumes and pore radii determined by nitrogen adsorption and mercury intrusion have been found to agree closely. The passivation is reversed by reduction in hydrogen at 200°C and both BET and copper surface areas are restored.

Methanol synthesis over raney copper-zinc catalysts. III. optimization of alloy composition and catalyst preparation

Methanol synthesis was studied over Raney copper catalysts made by selectively leaching Al and Zn from Al-Cu-Zn alloys with aqueous sodium hydroxide. Methanol yields in excess of that obtained from an industrial catalyst under identical conditions were obtained. Catalysts made from alloys containing the ternary phase Cu 3Al 3Zn had the highest specific activity but developed only low surface areas due to the resistance to leaching of Al and Zn in the ternary phase. Evidence is presented of synergism between Raney copper and zinc oxide reprecipitated during extraction. It is thought likely that the copper is present under methanol synthesis conditions as Cu o. Copper as Cu I is not believed to be present in these catalysts.

Zinc-Promoted Raney Copper Catalysts for Methanol Synthesis

Zinc-Promoted Raney Copper Catalysts for Methanol Synthesis

Bulk and surface composition of Raney copper catalysts

1. It was established that considerable differences exist in the chemical composition of catalysts on the surface and in the interior. 2. A direct relation does not exist between the chemical composition of the surface and the activity of Raney copper catalysts.

Enantioselective hydrogenation on heterogeneous metal catalysts

The rate of formation of the excess of one enantiomeric product in the enantioselective hydrogenation of ethyl acetoacetate (EAA) and acetylacetone (acac) on a Raney copper catalyst modified with chiral aminoacids (AmA) correlates with the formation constants of the mixed complexes [CU EAA AmA] and [Cu acac AmA].

Asymmetric hydrogenation of acetoacetic ester on raney cobalt and copper catalysts modified with D-(+)-tartaric acid

1. On Raney Cu and Co catalysts modified with D-(+)-tartaric acid acetoacetic ester is hydrogenated asymmetrically. 2. The optical yield of (-)-ethyl-3-hydroxybutyrate depends on the nature of the catalyst and the experimental conditions: on Cu catalyst the optical yield reaches 20–24% and is close to the optical yield obtained on modified Ni catalyst: on Co catalyst the optical yield is considerably less (2–8%). With increase in the quantity of catalyst the optical yield on these catalysts passes through a maximum.

X-ray diffraction line broadening studies of Raney copper and nickel

X-Ray diffraction line broadening analysis has been used to determine crystallite sizes, microstrains and stacking fault probabilities in Raney nickel and Raney copper catalysts prepared by different methods. The data for the Raney catalysts were compared with those for ball-milled copper and nickel powders. Time and temperature of digestion of the Raney alloys affect the defect structures. The crystallite size in the (111) direction was mainly determined by the digestion temperature. On aging a highly active Raney nickel, a rapid decrease of microstrain was observed. This was followed by a steady growth in the (100) direction, while little change occurred in the (111) direction. Aging the catalyst and increasing the digestion time of the Raney alloy were shown to cause similar changes in defect structure. The microstrain and stacking fault probability were observed to be inversely related to crystallite size.

AldehydecollidineD erivatives. I-II. I. High Pressure Hydrogenation of Aldehydecollidine with Raney Nickel and Raney Copper Catalysts

石油化学工業の発展により,パラアルデヒドとアンモニア,あるいはアセチレンまたはビニルエーテルとアンモニアとから合成されるいわゆるペトロピリジンと称されるアルデヒドコリジン(2-メチル-5-エチルピリジン,以下MEPと略す)の合成が工業化されるに至り,その生産が増大してきた。著者らはMEPの還元生成物ならびにその誘導体の合成を試み,まずラネー触媒を用いてMEPを高圧水素添加し,2-メチル-5-エチルピペリジンを得る反応における水素添加反応速度を測定し,最適反応条件を検討した。MEPの水素添加反応は,その初期においては芳香核の高圧水素添加反応の反応速度式-dp/dt=kp,logpn/p-kt/2.303Vが適用されることが明らかとなった。水素添加の最適反応温度は,ラネーニッケル触媒の場合は180℃,ラネー銅触媒では200℃であった。

Decrease of the Surface Area of Raney-type Catalysts in the Aluminium dissolution Process

Abstract Variations of the surface area in the dissolution process were investigated on a Raney copper catalyst “No. 16” (for dehydrogenation of cyclohexanol) and a Raney nickel catalyst. It has been found that nascent bare atoms of copper or nickel formed at the initial step move rapidly, perhaps particularly in alkali solution, to reconfigurate the surface-structure to a more stable one. That is to say, the surface area reaches a maximum at an initial step, where only a small quantity of aluminium is dissolved out, then rapidly decreases to a stable value in spite of successive dissolution of aluminium. The rate of decrease is much greater than that recognized on reserving the catalyst in its dried state or in water. By calculating reliable “n” values, the number of adsorbed molecular layers on the surface area from the modified B.E.T. equation, it has been deduced that the average catalytic activity per unit area of the surface may be decreased in process of dissolution of aluminium.

(97)Raney銅触媒による芳香核の水素添加

(97)Raney銅触媒による芳香核の水素添加