Dried catalysts

As you are about to see, the standard methods for using the NaBH(OAc)3 catalyst call for it to be in a dried, powder form. Strike supposes the benzene in the above reaction can be distilled off to leave dry catalyst. But don t quote Strike on that Maybe it could be made in situ in the DCE solvent of the reaction to come (don t ask). Aw hell Just go and buy the shit ... 

Early efforts to prepare metal soaps involved attempts to dissolve the natural materials in oils. By the latter part of the nineteenth century, substantial progress had been made in the preparation of fused resinates and linoleates of lead and manganese. The utiUty of cobalt as a drying catalyst was discovered close to the turn of the century, but the factors that led to its ultimate discovery are not recorded. 

B. Palladium on carhon catalyst (5% Pd). A suspension of 93 g. of nitric acid-washed Darco G-60 (Note 10) in 1.21. of water contained in a 4-1. beaker (Notes 3 and 4) is heated to 80°. To this is added a solution of 8.2 g. (0.046 mole) of palladium chloride in 20 ml. (0.24 mole) of concentrated hydrochloric acid and 50 ml. of water (Note 2). Eight milliliters (0.1 mole) of 37% formaldehyde solution is added. The suspension is made slightly alkaline to litmus with 30% sodium hydroxide solution, constant stirring being maintained. The suspension is stirred 5 minutes longer. The catalyst is collected on a filter and washed ten times with 250-ml. portions of water. After removal of as much water as possible by filtration, the filter cake is dried (Note 11), first in air at room temperature, and then over potassium hydroxide in a desiccator. The dry catalyst (93-98 g.) is stored in a tightly closed bottle. 

A platinum on silica gel catalyst was prepared by impregnation of silica gel (BDH, for chromatographic adsorption) by a solution containing 0.5% (wt.) of sodium hydroxide and 0.5% (wt.) of chloroplatinic acid (both of analytical grade). The dried catalyst contained 1% (wt.) of platinum and a corresponding amount of the alkaline component. The BET surface area of the catalyst was 40 m2/g, the mean pore radius 150 A. The catalyst was always reduced directly in the reactor in a stream of hydrogen at 200°C for 2 hr. 

Figures 2.a-c show the pyridine adsorption results. Bronsted acidity is manifested by the bands at 1440-1445,1630-1640 and 1530-1550 cm . Bands at 1600-1630 cm are assigned to pyridine bonded to Lewis acid sites. Certain bands such as the 1440-1460 and 1480-1490 cm can be due to hydrogen-bonded, protonated or Lewis-coordinated pyridine species. Under continuous nitrogen purging, spectra labeled as "A" in Figures 2a-c represent saturation of the surface at room temperature (90 25 unol pyridine/g found in all three tungsta catalysts) and "F" show the baseline due to the dry catalyst. We cannot entirely rule out the possibility of some extent of weakly bound pyridine at room temperature. Nevertheless, the pyridine DRIFTS experiments show the presence of Brpnsted acidity, which is expected to be the result of water of reduction that did not desorb upon purging at the reduction temperature. It is noted that, regardless of the presence of Pt, the intensity of the DRIFTS signals due to pyridine are...

Catalyst filtration rates were measnred by passing a slnrry of bnffer solntion containing 5 g (dry) catalyst through a filter cloth (BHS Werk Sonthofen PAN 2326 multiful Luftdl. 20 L / m2s bei 20 mm WS) at 0.1 MPa N2 pressure. 

The initial screening of the resin catalysts was done in a batch reactor at supercritical for butene-1 conditions of temperature 155 °C, pressure of 1000 psig and at molar ratio of 1-butene water of 5.5. The reaction was stopped after predetermined period of time and the products analyzed. It was found that under the standard reaction conditions, for all of the catalysts studied, a constant concentration in the sec-butanol concentration was achieved within a 1-2 hour reaction time. Using only the linear section of the concentration-time plot, the one hour result was used to evaluate the catalyst activity, which was normalized as mmol of SBA/ per proton/ per hour (a), as mmol of product/ per gram of dry catalyst/ per hour (b) and mmol of product/ per ml of wet catalyst/ per hour (c). 

Addition of dry catalyst to 98% formic acid used as a hydrogenation solvent can be extremely hazardous, because hydrogen is released by decomposition of the acid. Addition of acid to the water-wetted catalyst is safer. 

In preparation for the reduction of a nitro compound, the tetrahydroborate solution is added to an aqueous supension of palladium-on-charcoal catalyst. The reversed addition of dry catalyst to the tetrahydroborate solution may cause ignition of liberated hydrogen. 

Particle Structure. First of all, the particle structure has a fundamental influence on the degradation propensity. The extent of degradation as well as its mode will strongly depend on whether the particle is a single crystal, has an amorphous structure or is an agglomerate. For example, spray-dried catalysts, which are often used in fluidized bed reactors, are... 

The catalytic experiments were carried out in a fixed bed flow-type apparatus in the gas phase at atmospheric pressure (p,otai 100 kPa). The carrier gas (N2, nominal purity 99.99 vol.-%) was loaded with vapors of the reactant(s) in (a) thermostated saturator(s). The mass of dry catalyst was ca. 200 mg. In the isomerization experiments, the partial pressure in the feed and the modified residence time were Pi M-Np = 2.0 kPa and W/Fi.M.Np =110 g-h/mol, respectively. In the alkylation experiments, the partial pressures in the feed amounted to P2-M-NP = 1-9 kPa and p oH = 0.95 kPa, and W/I -Np was 170 g h/mol. Product analysis was done by automatic on-line sampling and high resolution glc using a capillary column of 50 m length, OV-1 as stationary phase and H2 as carrier gas. Various temperature programs were employed depending on the product mixture to be analyzed. 

Platinum was introduced on the activated support by a competitive cation exchange technique. An amount of 100 g of a 8 wt% Pt solution of platinumtetrammine hydroxide (Johnson Matthey) was added dropwise to a suspension of 40 g graphite in 800 ml 1 M ammonia (Merck p.a.) and stirred at ambient temperature for 24 hours. The catalyst was subsequently separated by filtration on a Millipore filter (HV 0.45m), washed with distilled water and dried in a vacuum oven at 373 K. The dried catalyst was reduced in flowing hydrogen at 573 K for 2 hours and stored under air before use. 

Similar trends were found for the palladium leaching values when leaching fresh catalysts. However, the overall amount of palladium leached is higher in this case. The results of the leaching tests performed one day after the catalyst preparation show values between 140 and 240 ppm for the reduced and of 30 to 60 ppm for the non-reduced catalysts. A comparison of the decrease of metal leaching over time shows different aging effects for the dry catalysts compared to the wet catalysts of... 

Fig. 8. Effects of % RS and spacer-chain length on the amount of solvents imbibed into 100/200 mesh 2% CL catalysts at 25 °C on the basis of g solvent/g dry catalyst. Left, catalyst 1 center, catalyst 3 right, catalyst 4. (Reprinted with permission from Ref.80>. Copyright 1982 John Wiley and Sons. Inc.)...

Figure 3.7 Catalytic activity of subtilisin in anhydrous organic solvents ( n-hexane, diisopropyl ether, T THF) as a function of the KCI content in the dry catalyst. The activity is expressed in terms of kat/Km of the transesterification reaction between N-acetyl-L-phenylalanine ethyl ester and n-propanol, used in concentrations of lOmM and 0.85 M, respectively [88].

The pumice-supported copper oxide catalyst containing 16 weight % of copper was prepared by impregnating 20 to 40-mesh crushed ptimice stone with a copper nitrate solution and drying it at 105°C. for 6 hours The dried catalyst was subsequently calcined at 600°C. for 6 hours and placed in the reactor. The catalyst was activated by passing air over it for 12 hours before any experimental run was made. 

---