Apparatus for Catalytic Reduction

In general if the drop in pressure is less than 0.03 atm. (0.5 lb.) in the time indicated the apparatus may be considered sufficiently free from leaks for ordinary work. 

The bottom of the tank is cut off, the filling removed, and the bottom welded on again. 

A copper tube may be used for this connection but is less satisfactory since the shaking tends to wear it out at the joints. 

It is advisable to boil the tube and stopper with several portions of 20 per cent sodium hydroxide until the solution is no longer colored yellow, after which the boiling is carried out several times with distilled water. 

The motor, pulley and the supports for the reaction vessel must be attached firmly to a heavy wooden stand which will allow as little motion as possible in the apparatus during shaking, thus reducing to a minimum the possibility of the gradual formation of leaks. 

---

Adams, R. Voorhees, V. Apparatus for Catalytic Reduction Organic Syntheses Volume VIII pgs 10-16... 

The catalyst is previously prepared in an apparatus for catalytic hydrogenation, in which are placed 0.5 g. of palladous chloride, 3.0 g. of Norite, and 20 ml. of distilled water. The bottle is swept out with hydrogen and then shaken with hydrogen for 2-3 hours at 2-3 atmospheres (40 lb.) pressure. The palladium on carbon is collected on a Biichner funnel, washed with five 50-ml. portions of distilled water, then with five 50-ml. portions of 95% ethanol, and finally twice with ether. Upon drying, about 3 g. of the catalyst is obtained. It is stored in a vacuum desiccator over solid sodium hydroxide. If the reduction of the chloro-lepidine does not proceed normally, the used catalyst should be removed by suction filtration and a fresh 3-g. portion of catalyst added. Failure of the reduction step is usually due to an inactive catalyst or to impurities in the acetic acid or chlorolepidine. The palladium catalysts, prepared as described elsewhere in this volume, are presumably also satisfactory for the reduction of 2-chlorolepidine (p. 77). 

Fiq. 41. Cross-sectional view of apparatus used for catalytic reduction to carbon skeleton. Catalyst tube measures 21.7 cm X 0.7 cm o.d. Reproduced from Adhikary and Harkness (A4) with permission. 

DSC tests show a substantial reduction of the hydrogen desorption onset (red circles) (T J and peak (T ) temperatures due to the catalytic effects of n-Ni as compared to the hydrogen desorption from pure MgH also milled for 15 min. (Fig. 2.57). It is interesting to note that there is no measurable difference between spherical (Fig. 2.57a) and fdamentary (Fig. 2.57b) n-Ni, although there seems to be some effect of SSA. We also conducted desorption tests in a Sieverts apparatus for each SSA and obtained kinetic curves (Fig. 2.58), from which the rate constant, k, in the JMAK equation was calculated. The enhancement of desorption rate by n-Ni is clearly seen. At the temperature of 275°C, which is close to the equilibrium at atmospheric pressure (0.1 MPa), all samples desorb from 4 to 5.5 wt.% within 2,000 s. 

The volume of fhe ventiiatior gas by washing for a 6-lane tunnel 1 km in length is approximately 1.5 million m h-, which is almost equivalent to that from middle-size power station plants, while the concentration of NO and other pollutants is much lower. To treat the ventilation air, about 4,000 units of the apparatus in Fig. 8.25 may be necessary. This is considered to be a very large system, but it is estimated that this system is smaller in scale and more cost-effective than those systems using concentrations of NO and NH3, the selective catalytic reduction method. Furthermore, the scale can be smaller if more active air-purifying materials are developed. 

Mossbauer spectroscopy may be important and useful when applied to electrodes which contain ferromagnetic components. It is basically an in situ tool which provides valuable information on possible orientation and oxidation states of ferromagnetic species in the electrodes as a function of the electrochemical process and the potential applied. For example, electrodes for oxygen reduction may be highly catalytic when containing macrocycles with transition metal cations such as Fez+, Niz+, Coz+ [89,90], A typical apparatus for this technique is described in Ref. 91. 

In recent times, the reduction of nitrobenzene to aniline by hydrogen or water gas, in the presence of suitable catalysts, has been introduced. Compared to the iron reduction method, the catalytic method has the advantage of being a continuous process and therefore requiring a considerably smaller apparatus for the same production. ... 

The amount of metallic nickel in catalysts was determined by a DTA method by Macak and Malecha (84). Nickel produced by the reduction of nickel oxide was reoxidized by oxygen and the AT of the oxidation reaction was determined by the apparatus. The maximum value of AT between the reactor for catalytic reaction and that with inert Si02 packing was proportional to the amount of nickel in the catalyst sample. Accuracy of the method was about 4%. 

The activity of this catalytic system is very high. Although comparisons between data collected in different laboratories should be made with caution, it appears that [PPN][Rh(CO)4] is the most active homogeneous catalyst ever reported for the reduction of nitrobenzene to aniline. In the paper, only forcing conditions were used, in order to reach the highest turnover frequencies. However, we have observed in model studies that nitroarenes reduction to anilines with this catalyst can occur even at room temperature and atmospheric CO pressure. So the reaction appears to be very versatile and easily tuneable depending on the activities required and the apparatus available. 

---