Analysis of the Liquid Phase

To begin the exploration of actual reaction pathways in complex pyrolyses of aromatic substances, we have carried out a detailed experimental and theoretical analysis of the liquid-phase pyrolysis of bibenzyl. This pyrolysis system has been studied by others (44,45,46), and the general kinetic features of this reaction system are now rather well agreed on. Complete details of this work will appear elsewhere (38a) and a few implications of this work of particular relevance to coal reactions will be discussed here. 

All sol-gel derived catalysts were stable under reaction conditions, except the rhodium and iridium catalysts, whose colour changed significantly during reaction. The catalysts could easily be separated from the reaction mixture by simple filtration. The filtrated liquid product, that flew out colourless, exhibited no further catalytic activity. GC analysis of the liquid phase indicated the production of dmf with 100% selectivity in all cases, except for the platinum containing catalyst (Table 1). 

Three types of activated carbon with different oxidative pretreatments and different PZCs are shown in Table 3. Adsorption of cationic and anionic Pt is measured as a function of pH, using constant metal concentration. As before, the extent of uptake is determined by ICP analysis of the liquid phase before and after contact with the support. 

Ko. M.K. Mass Transfer Analysis of the Liquid Phase methanol Synthesis process, Ph.D. dissertation. University of Skron, Akron, OH, 1987. 

Impressive enantioselectivities (up to >99.9% enantiomeric excess) were observed with a large range of thioethers. However, moderate yields were obtained [ca. 30-40%), which was attributed to a kinetic resolution in the oxidation of sulfoxide to sulfone, thus reducing the yield in sulfoxide. The heterogeneous nature of the catalyst was confirmed by inductively coupled plasma (ICP) spectroscopic analysis of the liquid phase (<1 ppm of titanium). The catalyst was recycled by simple filtration, and was reused at least 8 times in oxidation of thioanisole without any loss of enantioselectivity. 

It is possible to investigate the flow structure in bubble column reactors by means of hot wire anemometers. The analysis of the liquid-phase velocity data results in consistent descriptive functions on the turbulent motion. The large-scale structures of these flows are determined by the column diameter, and a coherent circulation cell structure must be taken into account. Further measurements are required to establish quantitative relations between the flow structures and disperging properties of turbulent flows. 

All the experiments were performed in a water thermostat. Equilibrium was ascertained by repeated analysis of the liquid phase, which was separated from the solid phase by filtration through a mat of platinum wires. Phosphate was determined gravimetrically as Mg2P2 7 Sodium was determined as Na2S04 after phosphoric acid had been removed as lead phosphate. 

The Isothermal method was used. Equilibrium was checked by repeated analysis of the liquid phase. The liquid and solid phases were separated from each other by filtration through a platinum wire mat. Analyses were done gravlmetrlcally phosphate as Mg2P20 > and potassium as KCIO. ... 

Let us now assume that the mixture is one of n-hexane(l)and n-heptane(2), and that after equilibrium is reached at a bath temperature of 60°C, analysis of the liquid phase gives JCj - X2 - O.S. Since experimental measurements are time-consuming and costly, they are avoided whenever possible. To this purpose, let us then consider the following two questions ... 

The principle of headspace sampling is introduced in this experiment using a mixture of methanol, chloroform, 1,2-dichloroethane, 1,1,1-trichloroethane, benzene, toluene, and p-xylene. Directions are given for evaluating the distribution coefficient for the partitioning of a volatile species between the liquid and vapor phase and for its quantitative analysis in the liquid phase. Both packed (OV-101) and capillary (5% phenyl silicone) columns were used. The GG is equipped with a flame ionization detector. 

Gal-Or and Hoelscher (G5) have recently developed a fast and simple transient-response method for the measurement of concentration and volumetric mass-transfer coefficients in gas-liquid dispersions. The method involves the use of a transient response to a step change in the composition of the feed gas. The resulting change in the composition of the liquid phase of the dispersion is measured by means of a Clark electrode, which permits the rapid and accurate analysis of oxygen or carbon dioxide concentrations in a gas, in blood, or in any liquid mixture. 

The chromatograms of the liquid phase show the presence of smaller and larger hydrocarbons than the parent one. Nevertheless, the main products are n-alkanes and 1-alkenes with a carbon number between 3 to 9 and an equimolar distribution is obtained. The product distribution can be explained by the F-S-S mechanism. Between the peaks of these hydrocarbons, it is possible to observe numerous smaller peaks. They have been identified by mass spectrometry as X-alkenes, dienes and also cyclic compounds (saturated, partially saturated and aromatic). These secondary products start to appear at 400 °C. Of course, their quantities increase at 425 °C. As these hydrocarbons are not seen for the lower temperature, it is possible to imagine that they are secondary reaction products. The analysis of the gaseous phase shows the presence of hydrogen, light alkanes and 1-alkenes. 

The waxes, the organic phase, and the aqueous products, on the contrary, were unloaded daily from the collection traps and analyzed with an off-line GC (Hewlett-Packard model 6890) equipped with two flame ionization detectors and two identical columns (Hewlett-Packard HP-5), one connected to an on-column injector and dedicated to the analysis of waxes (dissolved in CS2 before the injection), and the other connected to a split/splitless injector and used for the analysis of the liquid reaction products (aqueous and organic phases). CH3CN was added to the aqueous sample prior to the injection as internal standard. 

The bioconversion process of Acid Orange 7 will be hereby analyzed. This is an incremental study with respect to that due to Lodato et al. [41], based on the operation of an airlift reactor with cells of Pseudomonas sp. 0X1 immobilized on natural pumice (density = 1,000 kg/m3 particle size = 800-1,000 pm). Details regarding the strain, medium, culture growth and main diagnostics of the liquid phase are reported by Lodato et al. [41]. Elemental analysis of dry biomass was obtained by a C/H/N 600 LECO analyzer. 

For the purpose of this case study we will select Isopropyl alcohol as the crystallization solvent and assume that the NRTL-SAC solubility curve for Form A has been confirmed as reasonably accurate in the laboratory. If experimental solubility data is measured in IPA then it can be fitted to a more accurate (but non predictive) thermodynamic model such as NRTL or UNIQUAC at this point, taking care with analysis of the solid phase in equilibrium. As the activity coefficient model only relates to species in the liquid phase we can use the same model with each different set of AHm and Tm data to calculate the solubility of the other polymorphs of Cimetidine, as shown in Figure 21. True polymorphs only differ from each other in the solid phase and are otherwise chemically identical. 

Principle The underlying principle of head space gas chromatography is the analysis of the vapour phase in equilibrium with the solid or liquid phase. 

The C and N Balances. The sum of the carbon and nitrogen contents of the solid and of the liquid phases was obtained by combustion for C and by Kjeldahl for N. It reproduces the initial content before reaction in all cases within the limits of the experimental error ( 0.3% for C and N). Since hydrocarbons are detected in the gas phase, this means that their total C content is smaller than the experimental error effecting the combustion analysis. 

Using the monomolecular rate theory developed by Wei and Prater, we have analyzed the kinetics of the liquid-phase isomerization of xylene over a zeolitic catalyst. The kinetic analysis is presented primarily in terms of the time-independent selectivity kinetics. With the establishment of the basic kinetics the role of intracrystalline diffusion is demonstrated by analyzing the kinetics for 2 to 4 zeolite catalyst and an essentially diffusion-free 0.2 to 0.4 m zeolite catalyst. Values for intracrystalline diffusivities are presented, and evidence is given that the isomerization is the simple series reaction o-xylene <= m-xylene <= p-xylene. 

The reduction of citral is performed in situ, in the same autoclave, without any exposure of the catalyst to air. After cooling down the reactor to room temperature and reducing the hydrogen pressure, a solution of 0.9 ml of citral and 0.4 ml of tetradecane (internal standard) in 10 ml of n-heptane is introduced under hydrogen in the autoclave. The temperature and the hydrogen pressure are then raised to respectively 340K and 7.6 MPa. The kinetic of the reaction is followed with time by analysis of samples of the liquide phase. The selectivity for a product X at 100% conversion (Sx) is defined by Sx = [X]10o/[Citral]0. (Citral]0 represents the initial concentration of Citral (2 and E) and and [X]iqo represents the concentration of X at 100% conversion. 

In the analysis of Eq. (1) we assume that the relative permittivity of the liquid phase is the same as that of the membrane phase, for simplicity. If this is not satisfied, Eq. (1) with i — 1 needs to be modified [32-34]. Although the solution procedure similar to those introduced above can be used, the analysis becomes much more complicated. 

---