Sulfur materials

Rigorous hydrogenating conditions, particularly with Raney Nickel, remove the sulfur atom of thiophenes. With vapor-phase catalysis, hydrodesulfurization is the technique used to remove sulfur materials from cmde oil. Chemically hydrodesulfurization can be a valuable route to alkanes otherwise difficult to access. 

It is in the field of middle distillates and fuel oils that sulfur may confront some refiners with major problems that will grow as the production of higher sulfur crudes increases. It may be worth while to consider in some detail the case of high speed Diesel oil, for which discussion about sulfur content is controversial. Curiously enough it is in the United States, where low-sulfur material has been in relatively plentiful supply, that... 

An ongoing study of sulfur materials taken from an Icelandic Norse-trading site context (55) has used this combination of simultaneous co-incident X-ray micro-fluorescence and micro-diffraction analyses. The compositional data from the fluorescence results are used to constrain the multi-phase analysis of the diffraction data. This approach reduces the requirement for accuracy in the... 

Iberian Peninsula, production centers, majolica pottery found on Canary Islands, 384, 385-398 Icelandic Norse-trading site, sulfur materials, simultaneous co-incident x-ray micro-fluorescence and microdiffraction analyses, 204-205 ICP-MS. See Inductively coupled plasma-mass spectrometry ICP-OES. See Inductively coupled plasma-optical emission spectroscopy. 

Table II. Composition of Sulfur Materials Modified by Dicyclopentadiene0...

Figure 4. Gel permeation chromatograms of the styrene-modified sulfur materials. Samples are identified by percentage of styrene used (w/w sulfur) and heating time at 140°C. (a)...

Figure 5. Shore D hardness vs. log time plots of modified sulfur materials. Samples are identified by percentage of modifier used (w/w sulfur) and heating time at 140°C. The onset of sample shattering is indicated by X. (a) Sulfur (b) 5% dicyclo-pentadiene, 3 hr (c) 10% dicyclopentadiene, 3 hr (d) 25% dicyclopentadiene, 3 hr (e) 5% styrene, 3 hr (f) 10% styrene, 3 hr (g) 25% styrene, 3 hr (h) 25% myrcene, 0.8 hr.

Increases in the UTS of the polypropylene fabric by impregnation with sulfur materials ranged from 24 to 87% the highest increases were obtained with dicyclopentadiene-modified sulfur materials. Merely heat-... 

The surface courses for the selected pavements were assumed to consist of either conventional asphaltic concrete with limestone aggregate, sulfur-asphalt concrete with beach sand aggregate, or recycled Boulder asphaltic concrete with sulfur. Material properties used as VESYS IIM input data for these four surface layers are listed in Table IV. 

Figures 1 and 2, respectively, show the old and new processes. The major innovations are use of (1) a spray dryer absorber in place of the wet venturi, absorber, centrifuge, rotary dryer combination (2) a cyclic hot-water reheat system interconnecting thermally the calciner product solids and the effluent gas from the spray dryer absorber and (3) a coal-fired, fluidized-bed reactor for conversion of magnesium sulfite (MgSO ) and sulfate (MgSO ) to MgO and SO gas. Otherwise, the two systems are very similar, utilizing a regenerable absorbent to recover the sulfur material as a usable commercial grade of concentrated sulfuric acid.

A method, using differential scanning calorimetry, has been developed to estimate quantitatively orthorhombic and monoclinic sulfur in sulfur materials. Sulfur cooled from the melt at 120°C immediately gives monoclinic sulfur which reverts to orthorhombic sulfur within 20 hr. Limonene, myrcene, alloocimene, dicyclopentadiene, cyclododeca-1,5,9-triene, cycloocta-1,3-diene, styrene, and the polymeric polysulfides, Thiokol LP-31, -32, and -33 each react with excess sulfur at 140° C to give a mixture of poly sulfides and unreacted sulfur. In some cases substantial amounts of this unreacted sulfur may be held indefinitely in a metastable condition as monoclinic sulfur or S8 liquid. Limonene, myrcene, and dicyclopentadiene are particularly effective in retarding sulfur crystallization. 

Table IV. Tensile Strength of Modified Sulfur Materials Prepared at 140°C...

Table VI. Composition of Modified Sulfur Materials After Storage4...

Figure 3. Variation with time of percentage of crystalline sulfur (Sa + Sp) expressed as a percentage of the total free sulfur in Thiokol/sulfur materials. 1 Thiokol LP-31. 2 Thiokol LP-32. 3 Thiokol LP-33.

Since sulfur gases poison nickel methanation catalysts, sulfur material balances were done to determine the extent of sulfur buildup on the catalyst. This was accomplished by determining the total sulfur in the methanation catalyst and coal charged to the reactor and again on the ash and catalyst removed from the reactor. Representative results for 10 independent runs under similar experimental conditions are in Table IV. These data demonstrate that some of the sulfur is lost to the system, some remains in the ash, and some reacts with the catalyst. Furthermore, the considerable variance of the data for the independent runs indicates that the fate of the sulfur is very sensitive to experimental conditions. 

Sulfur material balances on the system showed that the sulfur contained in the coal charge became primarily distributed between the ash and methanation catalyst while some was lost to the system. The buildup of sulfide sulfur on the nickel catalyst amounted to 25-45% of that initially contained in the coal. This acquisition of sulfur by the methanation catalyst indicates that periodic catalyst regeneration would probably be necessary to maintain it in a sufficiently active form. In spite of the coal s predominant form of sulfur being organic, the sulfur remaining in the ash was predominantly in the sulfate form. 

The specific gravity of sulfur is almost 2, whereas many of the materials that sulfur seeks to compete with such as plastics have specific gravities in the range of 0.9 to 1.4. Usually the sulfur material must equate with these other materials on a volume basis rather than on a weight basis for structural reasons. Figure 2 shows how the costs are altered upward when this factor is considered. 

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