Loading of catalyst

At a certain point (0.08 % w/w catalyst to substrate ratio) there ensued a drop in reaction rate, together with a gradual loss of selectivity. Thus, a treadeoff point was chosen so that a minimal load of catalyst could be used in the process, without an undue sacrifice in rate or selectivity. 

Table 1 Selective oxidation of geraniol using air as oxidant. Conditions 0.085mol geraniol in toluene, 5wt.% loading of catalyst (dry weight), 60°C, 3bar air, 600rpm, 6h.

Enantioselective arylation of ketones can be realized either with the standard BINAP ligand, which requires harsh conditions and a high loading of catalyst to produce high yields (53),202 or with newer, MOP-type ligands (L4) (Section 9.6.3.4.2) under mild conditions and only one-tenth as much catalyst., 204... 

Substantial improvements are made by using the cobalt nanoparticles. Contrary to the previous cases, much lower CO pressure (5 atm) is enough for the completion of the reaction. However, high loading of catalysts (45 mol%) seems to be a drawback. Nevertheless, this system can be reused, and one of them is compatible with water solvent. ... 

Lithium triethyl(l-methylindolyl-2)borate has been introduced as a convenient source of indolyl residue for carbonylative cross-coupling with aryl iodides, alkenyl iodides, or triflates. The reaction requires elevated CO pressure and high loading of catalyst (5mol.%) (Equation (15)). Aryl and alkenyl bromides, as well as aryl iodides... 

The reaction of epoxides with C02 affords either CCs or polymers [119], and many reports have been made [120-125] and different active catalysts described [126-130] such as alkyl ammonium-, phosphonium-salts and alkali metal halides, in this respect. The main drawbacks here are the need for a high catalyst concentration, a high pressure (5 MPa of C02), and a temperature ranging from 370 to 400 K. The recovery of the catalysts for reuse is also a key issue, and in order to simplify the recovery process various hybrid systems have been developed, an example being that prepared by coupling 3-(triethoxysilyl)propyltriphenylphosphonium bromide with mesoporous silica [131]. In this case, the reaction was carried out in the absence of solvent, under very mild conditions (1 MPa, 263 K, 1 mol% loading of catalyst, 6h), such that the hybrid catalyst could be recovered and recycled several times. 

Unsymmetrical substitution of BINOL with a bulky group gives enhanced activity 95% ee was achieved with <1 mol% loading of catalyst, compared with comparable conditions employing 20 mol% BINOL.221... 

A range of asymmetric alkyl additions to ketones have been carried out using highly concentrated or solvent-free conditions to produce greener conversion 292 The loading of catalyst - a bis-sulfonamide - can be significantly decreased under these conditions. 

Economics The ISBL 2004 Gulf Coast location erected cost, including first load of catalysts and chemicals, with 30% allowance for offsites. 

Figure 7 presents the parameters of the reactor model and the operating conditions simulated. A packed bed of catalyst with a loading of catalyst equivalent to 0.11 gr of Shell 105 catalyst/void cc of reactor is assumed. A membrane 5 microns thick with 20 A pore radii is placed on inner side of a 3/8" I.D. porous support. The pore size of this support is considered to be large enough that it does not exhibit any resistance to mass transfer. A tortuosity... 

In contrast to the -enolates derived from cyclic ketones, addition of propiophenone trichlorosilyl enolate (Z)-21 to aldehydes requires longer reaction times and higher loadings of catalyst. Although the yields of the aldol products remain high, both the diastereo- and enantioselectivities are attenuated as compared to their E counterparts (eq 9, Table 8). 

The loading of catalyst particles influences cost, and values have been decreased over time, with the lowest ones about 14 pg/cm achieved by using a... 

Many desirable characteristics of honeycomb monolithic catalyst beds were illustrated by these two examples (1) catalyst loading lower than on pellets was adequate to maintain activity (2) the axial heat transfer rate resulted in rapid heat dissipation from the reaction zone (3) a vanation of void-to-caialysi-surface ratio with new turbulent interfaces at each interval introduced a convenient control over the extent of reaction. Two other variables that were investigated are loading of catalyst over bed length and type of catalyst used however, the comparative analyses have not been as systematically demonstrated for the particular operation described in these tests. 

The price of adsorbents and catalysts varies very widely depending on the nature of the material. The cheapest catalysts and adsorbents cost less than l/lb, while more expensive catalysts containing noble metals such as platinum and palladium have costs that are mainly determined by the amount of precious metal on the catalyst. In some cases, the value of the noble metal on a load of catalyst is so high that the chemical plant rents the catalyst rather than buying it, and when the catalyst is spent, it is returned to the manufacturer for precious metal recovery. 

Protect catalysts and adsorbents. Deactivated catalysts and adsorbents are solid wastes from the process. In some cases, relatively small amounts of contaminants can cause a load of catalyst or adsorbent to become useless. The catalyst... 

Important A loading of catalyst less than 1.8 mol % relative to the amount of 2,7-bis(N,N-diethylcarbamoyloxy)naphthalene gave erratic results. For example, 1.2-1.3 mol % sometimes gave an incomplete conversion, but additional catalyst (1.0 mol %) ensured completion of the reaction. This step was checked at least five times, each time with reproducible yields in the range of 86-89%. NiCl2(dppp) was used as received from Acros Organics. 

Nooy, F.M. Dense loading of catalyst improves hydrotreater performance. Oil Gas J. 1984, 12, 152. 

The range of strengths that are required are usually found from experience. A given reactor design will address this problem, but care should be taken not to violate specifications in selecting a fresh load of catalyst. 

High resolution transmission electron microscopy (TEM) (Jeol lOOCX) was employed to determine the size of the metal particles on the surface of the catalyst support, and the composition of individual metal particles was ascertained (for thin sections cut with an ultramicrotome) using a field-emission scaiming transmission electron microscope (STEM) (VG HB 501) (at 1.5 mm resolution) and an energy dispersive X-ray (EDX) analyser. The metal loading of catalysts was determined by ICP-AES (Spectro D), following dissolution in concentrated hydrochloric and sulphuric acids. Direct analysis of aqueous samples taken from the reaction medium, using the same analytical technique, allowed the corrosion of metallic components from the catalyst surface to be studied. 

---