Reuse of runs

Table 4. Example of experimental runs added at each stage and used in each analysis multiple stage with orthogonal plans at each stage and no reuse of runs...

The decision to use orthogonal plans or to allow nonorthogonal plans, and the decision to allow or disallow the reuse of runs from stage to stage, are related operational issues. They individually and jointly affect the performance of a screening plan and the complexity of calculations required to assess analytically that performance. Depending on characteristics of the application, such as the degree of measurement error and the need to account for block effects in sequential experimentation, either or both may be important considerations. 

Phosphate is sometimes present in MU water sources (say, 1-2 ppm or more) usually as a result of field and factory run-off or from the deliberate addition as a city water threshold agent to prevent corrosion and deposition in the mains. The steady growth in the reuse of secondary water sources such as municipal and industrial waste waters means that phosphate is increasingly likely to be present in MU. If the phosphate remains undetected, it likely will scale and foul FW lines by forming amorphous calcium orthophosphate [tricalcium phosphate Caj(P04)2] sludge before it reaches the boiler section. 

This allows for easy reuse of the catalyst in the reaction of allylation of secondary amines like piperidine or morpholine for several runs. The leaching of palladium was less than 0.001% of the initial amount. 

An important group of products are the secondary products or co-products. These are important for modeling the reuse of a co-product and hence cycles in the production process. There can be forward and backward cycles. Sometimes cycles need an initial quantity to start with. Some cycles should stay in a stationary state, others are only used to run until a material in stock is processed and then change to an alternative production. 

Attempted recychng and reuse of the heterogeneous catalyst (10) led to dramatic losses of activity. Following quantitative RCM of diethyl diallyhnalonate and simple filtration, the recovered resin was notably less active (<40% conversion) in a second run and the reaction mixture was dark in color. Such comphcations were attributed to the instability [14, 21] of Ru methylene (11) (Scheme 11.2) that propagates during the RCM of terminal diene substrates. In an effort to offset this solution-phase decomposition, the use of alkene additives was investigated. The... 

HRP/IL phase. The electrical conductivity of the PANI films prepared by solvent casting from the aqueous solutions showed a relatively high and similar value even after the fifth run (Fig. 12), which demonstrates the validity of our approach and the ease of recyclability and reuse of the enzyme inside the IL. For the PEDOT, the process of recovery and reuse was successfully repeated up to ten times using the same HRP/EDOT catalytic phase (Fig. 13), further confirming the success of the synthetic approach and the ease of recyclability and reuse of the enzyme inside the EDOT monomer phase. 

The Sonogashira coupling of haloazines can be effected by a series of catalyst systems. Recently a lot effort was devoted to the development of a recyclable catalyst system. Kotschy and co-workers recently reported the use of palladium on charcoal as a convenient palladium source for this process, which allows for the separation and reuse of the catalyst at the end of the reaction (7.35.), The authors also demonstrated that, in spite of the absence of any substantial catalyst leaching, the catalytic activity of the reused Pd/C decreases on each run,49 a surprising phenomenon which was attributed to the dissolution and reprecipitation of the active catalyst in the course of the process. Pd(OH)2 on charcoal exhibited a similar activity in the Sonogashira coupling of bromopyridines.50... 

Hutchings el al. (102,103) synthesized enantioselective Mn catalysts by adsorption of chiral salen ligands on Mn-exchanged Al-MCM-41 and used the materials in selective epoxidation of dv-stilbcnc with PhlO. Although the simplicity of this approach is appealing, reuse of the material in a second run led to a dramatic decline of the epoxide yield from 69 to 18%, and of the ee of the trans epoxide from 70 to 30%. 

The expected number of runs required by a sequential screening plan depends, sometimes heavily, on (1) whether a response value may be used only once in the analysis immediately following the experimental stage in which it is acquired or may be reused in subsequent analyses, and (2) whether the experimental designs... 

In the classical oxidative alkyne-dimerisation reaction large quantities of solvent are often required which makes alternative procedures attractive. With 20 mol% CuCl and 20 mol% TMEDA, the dimerisation product of phenylacetylene, viz. 1,4-diphenyl-1,3-butadiene, was obtained at ambient temperature in [C4Ciim][PF6] in 95% y ield.1 2 Products were isolated by extraction of the ionic liquid phase with toluene and reuse of the catalyst was possible, but addition of further catalyst was necessary every two runs to keep reaction rates more or less constant. 

The same reaction was also investigated using the palladium-carbene complex, 58, as catalyst (Scheme 9.12).1401 Of the different ionic liquids studied, tetrabutylammonium bromide gave by far the best results while imidazolium based solvents afforded only poor conversions. At atmospheric pressure, only iodobenzene was carbonylated. The conversion of less reactive arylhalides not only required higher CO-pressures, but also the addition of a phosphine ligand. Reuse of the catalyst after extraction of the product with diethyl ether was possible for at least 6 runs with only a moderate decrease in activity. 

R-phenylglycinate-R,R-hydrogen tartrate [2], a key building block for the P-lactam antibiotic, ampidllin. The addition of one mole each of benzalde hyde and R,R-tartaric add to a 10% solution of racemic methyl phenyl-glycinate [IJ in ethanol results in predpitation, after 24 hr, of the desired salt [2] in 85% 3deld. Reuse of the salt mother liquors as feed in subsequent runs results in, ultimately, an overall 95% conversion to the desired material (8). The presence of benzaldehyde greatly fadlitates the racemiza-tion process by forming, reversibly, a Schiff base. 

Solvents are selected to increase reaction rates, to increase the reproducibility and ease of running reactions, and to ensure that the desired quality and yield of product is reached. Other important considerations are to decrease waste and allow for efficient solvent recovery and reuse. Each of these goals has a direct efiect on productivity and product cost for a manufactured product. In early stages of development, providing material by any means is crucial, and solvents are selected to ensure that the desired product can be prepared within the timeline with minimal difficulty. 

The Pueblo Chemical Stockpile Outreach Office maintains a mailing list of more than 2,000 people, publishes a newsletter and project updates, and runs a speakers bureau that makes presentations to civic groups, business organizations, local officials, and more than 3,000 students each year. In particular, the committee is pleased with the outreach office s efforts to inform difficult-to-reach constituencies, such as Spanish-speaking migrant workers in the community of Avondale, near PCD. The outreach office also supports the quasi-govemmental local reuse authority, which is planning for the reuse of PCD real estate once demilitarization is completed. 

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