Nickel-kieselguhr catalysts preparation

In an effort to obtain a less temperature-sensitive system, lower nickel content catalysts were prepared on an alumina support and tested for demethylation activity. The first, Preparation A, with a nominal nickel content of 50 wt % was activated at 700°F in a slow stream of hydrogen at atmospheric pressure for 16 hours. This catalyst was tested at conditions similar to those employed with the nickel-kieselguhr catalyst reported above. The results are given in Table II. 

Once near steady-state activity had been reached (19 hours), the temperature was decreased 15 °F, and the effect of decreased temperature on conversion and selectivity established, Run 4. An estimated activation energy for the conversion of methylcyclohexane is 28 kcal/mole, only 2 kcal less than the approximate value for the nickel-kieselguhr catalyst. The effect of decreased operating pressure is shown by the data of Run 5. Conversion increased, and efficiency to cyclohexane decreased slightly. The same effect was noted previously in fixed bed tests with Preparation A. 

Copper can also be used as a catalyst, like nickel, alone, on carriers, or as a mixed catalyst with metals of the first to the eighth Group of the Periodic Table. The temperature needed for reduction of the catalyst, usually containing the copper as oxide, hydroxide, or basic carbonate, is 150-300°. Preparation of a copper-kieselguhr catalyst is similar to that of a nickel-kieselguhr catalyst.175... 

Nickel-kieselguhr catalysts with or without a small percentage of magnesia and thoria These catalysts were prepared by precipitation of the metals as carbonates from the solutions of their nitrates holding a suspension of B.D.H. kieselguhr. The carbonates were subsequently decomposed to the oxides in a current of air and the nickel reduced by hydrogen at 300°. 

A. Nickel-Kieselguhr Catalyst It was prepared by precipitating nickel carbonate from a hot solution of nickel nitrate by hot potassium carbonate solution in presence of kieselguhr, washing and drying the mass, and reducing it in situ in the reaction bomb itself by a stream of hydrogen at 300-350°. 

Adkins investigated the preparation of nickel and copper hydrogenation catalysts in 1931 and attempted to optimize a nickel oxide/kieselguhr catalyst preparation. A typical method of production was to add sodium carbonate solution to a sluny of kieselguhr with a nickel salt solution and precipitate basic nickel carbonate. The mixed solid was then filtered, washed, dried, calcined at 400°C, and pelletted with a lubricant such as graphite. 

The parent 7-oxanorbomane, 1, is commercially available. Its preparation starts with the catalytic hydrogenation of hydroquinone to generate a mixture of trans-and cfs-cyclohexane-l,4-diol [15-18]. cfs-Cyclohexane-l,4-diol can be isomerized into the more stable trans isomer with metallic sodium [17]. Dehydratation of the latter on A4 zeolites, on alumina [19], or over nickel-kieselguhr catalyst [20] provides 1. This reaction is exergonic (ArG° = ArH° — TArS° = -3.1 2.5 kcal/mol) at room temperature as its standard gas phase heat of reaction amounts to ArH° = -1-7.3 2.5 kcal/mol. A variation of entropy of reaction of ca. -1-35 eu is assumed for this fragmentation, what leads to —TArS° = 298(0.035) = — 10.4 kcal/mol. The standard gas phase heat of formation of frans-cyclohexane-1,4-diol (Scheme 1) is estimated from that of cyclohexanol (—69.0 2.0 kcal/mol) and the standard heat of oxidation of cyclohexane into cyclohexanol (—39.5 kcal/ mol) [21]. Chickos and Acree [22] give AfH°(l) = -43.4 0.5 kcal/mol (see also [23-25]). 

The nickel catalyst (about 50 wt% nickel on kieselguhr) was prepared by an ordinary precipitation method. Sodium carbonate solution was added to a slurry of kieselguhr and nickel nitrate solution at 70 °C and precipitate was obtained. This precipitate was washed with water thoroughly and then was dried at 105 C for 12 hrs, crushed to 60-150 mesh, calcined at 350 C for 4 hrs. This was activated with 100% hydrogen at 200, 300 and 350 "C for 4 hrs. These prepared catalysts were stored in nitrogen atmospheric bottle and desiccator. 

Nickel catalysts (a), Raney type. The Raney Catalyst Division and the Davison Chemical Division of W. R. Grace and Co. supply an identical 50% sponge nickel catalyst prepared by the method of Raney by leaching 1 1 nickel-aluminum alloy with alkali. The catalyst is similar to the W-catalysts described in the next section. Harshaw Chem. Co. supplies similar nickel catalysts. Universal Oil Products Co. catalyst kieselguhr pellets are reduced with hydrogen and pulverized before use (.see Org. Syn., Coll. Vol., 3,278 (1955). 

C. Supported Nickel Halide Catalysts Nickel iodide, nickel bromide, and nickel chloride, based on various supports, like silica gel, kieselguhr, kaolin, pumice, and charcoal, were prepared by almost similar methods. The halides were prepared by dissolving nickel hydroxide in the minimum quantity of hydriodic acid, hydrobromic acid or hydrochloric acid. 

When preparing a nickel oxide/kieselguhr catalyst, reaction between the components leads to the formation of nickel silicates, which are difficult to reduce. This can affect operation and the catalyst may require prereduction before use. The addition of a promoter such as copper oxide allows reduction at a lower temperature. 

The production of nickel oxide/kieselguhr catalysts illustrates that not only the composition but also the method of preparation of catalyst precursors determines... 

In the 1940 s Feitknecht and others recognized that a particular form of blue-green basic nickel/aluminum carbonate could be prepared from mixed nickel and aluminum solutions under specific conditions. The solid, as with the nickel oxide/ kieselguhr catalyst had the magnesia bracite structore, with part of the nickel layer replaced by aluminum and some of the hydroxyl groups replaced by carbonate. ... 

Nickel catalysts are universal and are widely used not only in the laboratory but also in the industry. The supported form - nickel on kieselguhr or infusorial earth - is prepared by precipitation of nickel carbonate from a solution of nickel nitrate by sodiiun carbonate in the presence of infusorial earth and by reduction of the precipitate with hydrogen at 450° after drying at 110-120°. Such catalysts work at temperature of 100-200° and pressures of hydrogen of 100-250 atm 43. ... 

Sasa prepared an effective nickel catalyst for the hydrogenation of phenol by decomposition of nickel formate in a high boiling solvent such as diphenyl ether and diphenyl. The catalyst thus prepared proved more active than Ni-kieselguhr in the hydrogenation phenol (eq. 11.12) and could be used repeatedly more than six times.71... 

Activated carbon finds many applications as a carrier for other catalysts. Apart from providing a large surface, various other benefits have been observed to attend the use of activated carbon as a carrier for other catalysts. One value is that the catalyst can be prepared at low temperatures—a feature generally desirable. Thus nickel salts deposited on activated carbon can be formed into an efficient catalyst at 350° to 400° C whereas temperatures of 420° to 450° C are required when kieselguhr is used as a support, and 550° C or higher with silica gel.6... 

Covert, Connor, and Adkins167 recommend the following procedure for preparation of a nickel catalyst on kieselguhr ... 

Nickel is by far the most commonly used catalyst in oil hardening. The catalyst problem consists of three phases (1) preparation of a suitable catalyst, (2) maintenance of its activity as long as possible, and (3) recovery and reactivation of the spent catalyst. Nickel catalysts are of different t3rpes, depending upon the operation in which they are used. They may be in a relatively fine state, particularly in those processes where stirring or other agitation of the oil is used, or they may be supported on inert mar-terials such as clays, kieselguhr, charcoal, or pumice, which extend the surface of the catalj t and facilitate the filtration of the catalytic mass from the oil. The decomposition of nickel formate produces a finely divided,... 

Nickel, cobalt, and iron catalysts are cmnmonly used for the Fischer-Tropsch s thesis. Nickel catalysts have been prepared by precipitation from a nitrate solution with potassium carbonate in the presence of thoria and kieselguhr in the proportions lOONiilSThOzilOO kieselguhr. It is not desirable to employ nickel catalysts at low temperatures and elevated pressures because the formation of nickel carbonyl is excessive. In the temperature range of 170-220°C at. low pressures, both liquid and gaseous products are obtained. As the temperature is increased to 300-350°C and the pressure increased to 300-400 psi, nickel catalysts produce only methane. Thus, these catal nsts can be used for making a gas from coal comparable in heating value to natural gas. 

Evidence has recently been provided by the work of de Lange and Visser (10) on nickel catalysts deposited on kieselguhr. This has established that the normal lattice of metallic nickel does not occur in materials prepared in this way, and that the reduced active catalyst is obtained as a result of the attack of hydrogen on a nickel hydrosilicate. By interaction of the diatomite and the nickel hydroxide deposited on it, an entirely new lattice is produced which provides a greatly increased total surface of catalyst, and which leads in the finished state to a widely dispersed and very stable arrangement of nickel atoms. It will be of great interest to obtain further evidence as to the exact distance between pairs of nickel atoms in this catalyst, which is of exceptionally high activity. 

---