Recycle solvents, analysis

Table V summarises the data of the sulphur analysis of the hydrocracked liquids and the various bpt fractions for CoMo and NiMo catalysed experiments. The sulphur contents of neither the total hydrocracked liquids nor the individual bpt fractions showed any dependence on repeat contact or catalyst type. The values did show that the sulphur concentrated in the recycle solvent fraction (275-450°C), suggesting that, even under the relatively strong conditions used, certain sulphur-containing compounds will survive to be recycled in the solvent However, the sulphur content of the coal liquid feed was reduced by about 50% and the sulphur content of the likely upgradable product was low.

The analysis of Wyodak recycle solvent by SEC-GC-MS shows that certain distribution order exists for species in coal liquids with respect to their size and degree of isomerization. The alkanes increase in chain lengths without any appreciable degree of isomerization, except for some biological markers such as pristane and phytane. Phenols and aromatics vary in size and extent of isomerization which causes the liquid to contain a large number of species. 

Gaschromatograph Analysis of SEC Fractions of Wyodak Recycle Solvent... 

Samples Preparation. The coal liquids were derived from the catalytic liquefaction of Pittsburgh Seam bituminous and Wyoming sub-bituminous coals. The analysis of these coals is given in Table I. The coals were liquefied in a bench-scale catalytic unit using cyclone overhead product as recycle solvent to insure that the liquid products were derived from the coal and not the solvent. The product streams from... 

J. F. Haw, T. E. Glass, and H. C. Dorn, Analysis of coal conversion recycle solvent by liquid chromatography with nuclear magnetic resonance detection. Anal. Chem. 53 (1981), 2332-2336. 

Analysis of Solvent-Refined Coal, Recycle Solvents, and Coal Liquefaction Products... 

Analysis of coal-derived distillates is done often by modified petroleum analytical procedures. In other studies (7,8,9) as in this one, mass spectrometry is the primary tool for characterizing the complex mixtures encountered. Recycle solvents and distillates were subjected to high-resolution mass spectrometry (MS) for compound identification and low-voltage MS for quantitative measurement of components (10). 

Approximately 10% of the Wilsonville SRCs are distillable at 250°C and 1 torr. There is, however, essentially no solvent residue left in the coal, since MS analysis of distillate from the SRC is shown to contain higher molecular weight molecules than make up the recycle solvent. The distillate material in the solvent-refined coal product is composed mainly of phenanthrene/anthracene and pyrene/fluoranthrene, together with lesser amounts of alkylated homologs. Since these three- and four-ring condensed aromatics are not solvent residue, some coals are being depolymerized to produce these compounds. 

Outline an overall process flow sheet and material balance including solvent recovery and recycle. This should be done with the aid of process simulation software. [See Seider, Seader, and Lewin, Product and Process Design Principles Synthesis, Analysis, and Evaluation, 2d ed. (Wiley, 2004) and Turton et ah. Analysis, Synthesis, and Design of Chemical Processes, 2d ed. (Prentice-Hall, 2002)]. In the flow sheet include methods needed for controlling emissions and managing wastes. Carefully consider the possibility that impurities may accumulate in the recycled solvent, and devise methods for purging these impurities, if needed. 

The above analysis was applied to a wider group of coals (including 44 coals from the Exxon Library and a number of coals from the Pennsylvania State University coal bank) and several sets of chars, tars and recycle solvents. Several improvements were also made in the spectral synthesis routine. 

Quantitative Analysis Quantitative analysis of liquids may be obtained by using a cell of known thickness and determining the sample density. A cell of 10 to 20 microns is adequate for most hydrocarbon liquids of interest. The cell width may be calibrated using interference fringes. Results for a coal recycle solvent are illustrated in Fig. 20 (plotted in abs. units/mg per 1.33 cm ). A KBr pellet was prepared for the same solvent for comparisons. Fig. 21. The two spectra agree within 5%. The pellet spectrum has an extra peak near 3500 wavenumbers due to water absorbed by the KBr. 

Liquefaction The ability to do quantitative structural analysis makes FT-IR a good tool for coal liquefaction research As an example. Fig 33 compares the feedstock and the product in a liquefaction process (47) The feedstock consists of 33 3% coal plus 66 6% recycle solvent The combined spectrum is compared with the spectrum of the product The lowest spectrum is the difference between the feedstock and the product The product is lower in oxygen groups but higher in aromatic hydrogen ... 

The preliminary modeling work on a variety of chromatographically stable metal systems established a basis to separate and detect metal components in the process recycle solvent. Preliminary quantitative total metal analysis showed only small amounts of a few metals. For this reason, neat injections of the sample were performed. 

The operation of an efficient recovery process should be the intention and primary goal of every user of solvents. However, this may not always be possible and a decision not to recycle solvent may be based on a cost/benefit analysis, or the technical difficulty. Indeed, even when operating a recovery process, waste will be generated which requires an environmentally acceptable disposal process. 

Other points to mention are that there has not been a real demonstration of recycling solvents for second time around usage, even as part of an undergraduate experiment, which has been documented in detail in the literature. Syntheses of specialized catalysts are not mentioned or included in the overall analysis of material efficiency of plans. There is a need to move away from expensive... 

Results of the GC-MS analysis indicated that the product distributions were related to the severity of the process. When the solvent stripping temperature was lowered in removing recycle solvent after reaction, the SRC solvent exhibits a much larger concentration of light components. 

As a matter of fact, the main advantage in comparison with HPLC is the reduction of solvent consumption, which is limited to the organic modifiers, and that will be nonexistent when no modifier is used. Usually, one of the drawbacks of HPLC applied at large scale is that the product must be recovered from dilute solution and the solvent recycled in order to make the process less expensive. In that sense, SFC can be advantageous because it requires fewer manipulations of the sample after the chromatographic process. This facilitates recovery of the products after the separation. Although SFC is usually superior to HPLC with respect to enantioselectivity, efficiency and time of analysis [136], its use is limited to compounds which are soluble in nonpolar solvents (carbon dioxide, CO,). This represents a major drawback, as many of the chemical and pharmaceutical products of interest are relatively polar. 

Another important parameter is the eluent composition. Binary mixtures (and obviously pure solvents) should be preferred to complex mixtures, since new systems perform an on-line analysis of the composition of binary eluents. These eluent systems allow the automatic eluent recycling, with a reduced number of controls. 

Hydrocarbons heavier than methane that are present in natural gases are valuable raw materials and important fuels. They can be recovered by lean oil extraction. The first step in this scheme is to cool the treated gas by exchange with liquid propane. The cooled gas is then washed with a cold hydrocarbon liquid, which dissolves most of the condensable hydrocarbons. The uncondensed gas is dry natural gas and is composed mainly of methane with small amounts of ethane and heavier hydrocarbons. The condensed hydrocarbons or natural gas liquids (NGL) are stripped from the rich solvent, which is recycled. Table 1-2 compares the analysis of natural gas before and after treatment. Dry natural gas may then be used either as a fuel or as a chemical feedstock. 

From this further analysis, the actual amount of waste (and its nature) per kilogram of product will become evident. At this stage it is also important to look forward and assess options for recycling or reusing the waste on site for example if a solvent can be efficiently recovered then this should be taken into account in calculating the E-factor. Although the choice of which route to fully optimize may not be obvious even from this further analysis, it will facilitate a reasoned discussion of the issues. 

Metal derivatives (Ti, Zn, Cd, Sn, Sb, Pb) and bromine from additives in recycled thermoplasts from consumer electronic waste were determined by dissolving the samples in an organic solvent, followed by TXRF analysis [56], The procedure proved considerably less time-consuming than conventional digestion of the polymer matrix. Results were validated independently by INAA. 

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