Optimality conditions

Integrated Chemical Processes. Edited by K. Sundmacher, A. Kienle and A. Seidel-Morgenstem Copyright 2005 WILEY-VCH Verlag GmbH Co. KGaA, Weinheim ISBN 3-527-30831-8 

Two emerging trends endorse the concept of heat-integrated processes first, the production of basic chemicals is moved close to oil and gas wells where crude oil or natural gas is processed in large stand-alone units [1]. Second, fuel cell systems require on-site and on-demand hydrogen production from primary fuels (i.e., natural gas, liquid hydrocarbons or alcohols) [2]. Net heat generation in these processes is equivalent to raw material and energy loss, and is therefore undesirable. 

While many publications in the field of heat-integrated processes focus on specific processes such as dehydrogenation of paraffins or hydrogen production [3-5], this chapter is more focused on general conceptual trends in process and apparatus design. 

The intended purpose of heat-integrated processes for endothermic reactions is illustrated by the example of methane steam reforming for hydrogen generation, which is of high practical relevance [6] and features typical characteristics of the considered process class. The reaction is given by the following stoichiometric equation  

Taking the amount of heat required for bridging the temperature gap (Tequ - To) for the endothermic mixture as a reference, the normalized heat loss is given by the following expression  

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Consider changing from batch to continuous operation. Batch processes, by their very nature, are always at unsteady state and thus are difficult to maintain at optimal conditions. 

For the case of electro-magnets, inclusions detection in welds situated at 1-2 mm of depth is very important, because the reluctance variation between the two mediums is not important, and thus the detection of this type of defect is very difficult. It will be sufficient to be in optimal conditions to eliminate this problem. 

Optimal conditions conespond to a magnetic excitation value such as permeability of the material is maximum. 

Defect identification, in height and width, is established by tlie magnetization spectrum surfaeic measure, by respecting the latest optimization conditions. The Spectrum sensibility could give us necessary information about the defect depth. 

Intrinsic bioremediation is becoming an acceptable option in locations where the contaminated groundwater poses Htde threat to environmental health. Nevertheless, although intrinsic bioremediation is appealingly simple, it may not be the lowest cost option if there are extensive monitoring and documentation costs involved for several years. In such cases it may well be more cost effective to optimize conditions for biodegradation. 

In these cases, it is better to protect the carboxyl group. Optimized conditions for A/-acetylation have been studied (78). A/-Acylation can be utilized for protecting the amino group in the reaction of amino acids, for example in peptide synthesis. 

The rate of side-chain cleavage of sterols is limited by the low solubiUty of substrates and products and thek low transport rates to and from cells. Cyclodextrins have been used to increase the solubiUties of these compounds and to assist in thek cellular transport. Cyclodextrins increase the rate and selectivity of side-chain cleavage of both cholesterol and P-sitosterol with no effect on cell growth. Optimal conditions have resulted in enhancement of molar yields of androsta-l,4-diene-3,17-dione (92) from 35—40% to >80% in the presence of cyclodextrins (120,145,146,155). 

Reaktions of complexes formation of In(III) with bis-(2,3,4-trioxy-phenylazo)benzidine (R) in presence of papaverine (Pap), dibazole (Dib), urotropine (Ur) has been studied by the spektrophotometric method. It has been established that the optimal conditions of complex formation for complexes of In(III) R-Pap, In(III) R-Dib and In(III) R-Ur are pH=2. 

Kinetic mles of oxidation of MDASA and TPASA by periodate ions in the weak-acidic medium at the presence of mthenium (VI), iridium (IV), rhodium (III) and their mixtures are investigated by spectrophotometric method. The influence of high temperature treatment with mineral acids of catalysts, concentration of reactants, interfering ions, temperature and ionic strength of solutions on the rate of reactions was investigated. Optimal conditions of indicator reactions, rate constants and energy of activation for arylamine oxidation reactions at the presence of individual catalysts are determined. 

Significant distinction in rate constants of MDASA and TPASA oxidation reactions by periodate ions at the presence of individual catalysts allow to use them for differential determination of platinum metals in complex mixtures. The range of concentration rations iridium (IV) rhodium (III) is determined where sinergetic effect of concentration of one catalyst on the rate of oxidation MDASA and TPASA by periodate ions at the presence of another is not observed. Optimal conditions of iridium (IV) and rhodium (III) determination are established at theirs simultaneous presence. Indicative oxidation reactions of MDASA and TPASA are applied to differential determination of iridium (IV) and rhodium (III) in artificial mixtures and a complex industrial sample by the method of the proportional equations. 

The optimal conditions for accelerating of investigated reaction by ions Fe(III) and Ag(I) ai e the following pH 5,0 (acetic buffer), Cj. . =l,6T0 M, CpMSA=4T0 M, Cpp =2-10 M. Under these conditions, factors of sensitivity for kinetic determination of metals mentioned above were established as a slope s tangent of the calibration curves that is a plot of reaction velocity (change of optical density of ferroin s solution for 4 minutes) versus analyte s concentration. Factors of sensitivity for determination of Mn(II), Fe(III), Ag(I), Pd(II), Co(II) ai-e 5,5-10" 1,1-10" 2,5-10" 2,0-10" 8,0-10", respectively. 

Interaction of periodate with immobilized on the silica gel surface QAS - trinonyloctadecylammonium chloride has been studied. The optimal conditions of periodate sorption have been investigated. Interference of main components of sea water has been examined. 16500-fold excess of Ck, 11000-fold excess of Na+, 380-fold excess of K+, 420-fold excess of Ca +, 500-fold excess of Mg +, 60-fold excess of HC03, 20-fold excess of B03, 280-fold excess of SO do not interfere with the determination of periodate. 

As the result of the performed investigations was offered to make direct photometric determination of Nd microgram quantities in the presence of 500-fold and 1100-fold quantities of Mo and Pb correspondingly. The rare earth determination procedure involves sample dissolution in HCI, molybdenum reduction to Mo (V) by hydrazine and lead and Mo (V) masking by EDTA. The maximal colour development of Nd-arsenazo III complex was obtained at pH 2,7-2,8. The optimal condition of Nd determination that was established permit to estimate Nd without separation in solution after sample decomposition. Relative standard deviations at determination of 5-20 p.g of Nd from 0,1 g PbMoO are 0,1-0,03. The received data allow to use the offered procedure for solving of wide circle of analytical problems. 

The influence of temperature, solution s pH and other parameters in formation of ionic associate is investigated. As a result, optimal conditions of determination are established pH 4,0 volume of acetate buffer - 0,5 ml volume of 0,1% aqueous solution of CV - 0,3 ml extraction time - 3 minutes. The ratio of aqueous and organic phases is 1 1. Photometric measurement of toluene layer is carried out at = 606,0 nm. The accuracy of procedures checked by the method of additives. 

There are a number of the optimal conditions for sorption pointed below volume of extract - 4 ml ratio of aqueous and organic phases is 1 1 cyllindric foampolyurethan (marc - T 25-3,8) with diameter 8 mm, height - 4,5 mm, mass - 0.007 g. Time of full soi ption is 20 min. Completeness of soi ption is determined by spectrophotometric method. 

The copper(II) flux is directly proportional to the cuiTent density up to 10 mPJcrcf. The extraction degree of platinum(IV) into the strip solution is less than 0.1 % per hour of electrodialysis. About 55% of copper(II) is removed from the feed solution under optimal conditions. The copper(II) extraction process is characterized by high selectivity. Maximum separation factor exceeds 900 in the studied system. 

SG- PVSA composite film obtained in the presence of Tween 20 possesed the best cation exchange characteristics. The maximum soi ption capacity of SG-PVSA composite film obtained under optimal condition was, mol/g 6,2-10 for Fe (Phen), 2,3T0 for Phodamine 6G and 2,5T0 for protons. The optimal content of PVSA in sol was 4%. 

It was shown that Zn + adsorbed onto SG-PVSA composite film as Zn(Phen) complex. It can be detected spectrophotometrically after treatment with anionic dye Bengal Rose (BR). Ternary complex Zn + - Phen-BR formed on the surface under optimal conditions. SG-PVSA film was used for determination of Zn + by spectrophotometric method. The calibration graph was linear in the concentration range 2,5T0 - STO mol/l. 

In the present work, the technique of XO and MTB immobilization onto silica gel in the form of its complexes with Fe(III) and Bi(III) respectively were found. The acid - base and chemical-analytical characteristics of solid-phase reagents were examined. The optimal conditions of quantitative recovery of Pb(II) and Zn(II) from diluted solutions, such as acidity of aqueous phase, the mass of the sorbents, the volume of solutions and the time of equilibrium reaching, were found. The methods of and F" detenuination were based on a competitive reactions of Zr(IV) with immobilized MTB and or F". Optimal conditions of 0,0 and F" determination in solution using SG, modified ion associates QAS-MTB (pH = 1,5, = 5-10 mol/1). 

The tolerance limits of metal ions and foreign anions at the optimal conditions were investigated. 

In order to find optimal conditions for the soluble copper determination we examined the influence of electrolysis potential, electrolysis time, and the solution stirring rate on the accuracy and sensitivity of determination. We found that the optimal parameters for PSA determination of copper were electrolysis potential of -0.9 V vs. 3.5 mol/dm Ag/AgCl, electrolysis time of 300 s, and solution stirring rate of 4000 rpm. The soluble copper content in samples investigated in this study varied from 1.85 to 4.85 ppm. Very good correlation between the copper content determined by PSA and AAS indicated that PSA could be successfully applied for the soluble copper content determination in various dental materials. 

The triplet-state energy level of oxytetracycline, the excitation maximum (412 nm), lifetimes of Eu-OxTc (58 p.s) and Eu-OxTc-Cit (158 p.s), were determined. A 25-fold luminescence enhancement at 615 nm occurs upon addition of citrate within a short 5-min incubation time at neutral pH. It s accompanied by a threefold increase of the luminescence decay time. The optimal conditions for determination of OxTc are equal concentrations of Eu(III) and citrate (C = T lO mol-E ), pH 7.2. Eor determination of citrate, the optimal conditions concentrations of Eu(HI) and OxTc are 1 0,5 (Cg = MO Huol-E-i, = 5-10-HuohE-i) at pH 7.2. 

The optimal conditions for the complexation were found. The luminescence of Tb " in (L ) complex was established to observed in a range of pH 2,0-11,0 with maximum at 7,0-7,5. The Tb (III) luminescence in complex with (L ) aslo depends on amount of reagents, solvent nature, amount of surfactants and trioctylphosphinoxide (TOPO). It was shown that introduction into the system Tb-L the 3-fold excess sodium dodecylsulfate (SDS) increases the luminescence intensity by 40 times and introduction into the system Tb-L the 3-fold excess TOPO increases the luminescence intensity by 25 times by the order value connecting with the crowding out of water molecules from the inner sphere of complexes. 

It is known that Selenium catalyzes reaction of some dye reduction by Sulphide. On this basis spectrophotometric and test-techniques for Selenium determination are developed. Inefficient reproducibility and low sensitivity are their deficiencies. In the present work, solid-phase reagent on silica gel modified first with quaternary ammonium salt and then by Indigocarmine was proposed for Selenium(IV) test-determination. Optimal conditions for the Selenium determination by method of fixed concentration were found. The detection limit of Se(IV) is 10 ftg/L = 2 ng/sample). Calibration curve is linear in the range 50-400 ftg/L of Se(IV). The proposed method is successfully applied to the Selenium determination in multivitamins and bioadditions. 

Prepai ative isolation of nonvolatile and semivolatile organic compounds fractions (hydrophobic weak acids, hydrophobic weak bases, hydrophobic neutrals, humic and fulvic acids) from natural and drinking waters in optimal conditions was systematically investigated by solid-phase extraction method with porous polymer sorbents followed by isolation from general concentrate of antropogenic and/or toxic semivolatile compounds produced in chlorination and ozonation processes. 

Influence of the various factors in static conditions (concentration of heavy metals, both time of contact and ratio of solid and liquid phase, pH of medium) on solution of Pb(II), Cu(II), Cd(II) and Zn(II) from water solutions is studied and the optimal conditions of their extraction by organosilica sorbents modified by ions of Al(III) and Cu(II) are found. 

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