Thiophene carbon adsorption

VOCs are the most well-known air contaminants released by chemical, petrochemical, and other industries. Benzene, toluene, xylenes, hexane, cyclohexane, thiophene, diethylamine, acetone, and acetaldehyde are examples of VOCs [77,78], Possibly, presently the most relevant technology for VOC control is adsorption on activated carbon [135-145], It is a recognized technology, largely applied in industrial processes for the elimination and recovery of hydrocarbon vapors from gaseous streams [77,136], Additionally, it offers several benefits over the others, that is, the opportunity of pure product retrieval for reuse, high removal efficiency at low inlet concentrations, and low fuel/ energy costs [135],... 

Carbon disulfide At room temperature, only physisorption occurs on Pt film [2], while partly reversible adsorption takes place on Pd film [31 with 0.7 chemisorbed coverage. The adsorption is believed to be dissociative over this latter surface [3]. Hydrogen can be adsorbed over CS2-covered Pt film [2] but cannot over CS2-covered Pd film [3]. Thiophene At room temperature, chemisorption occurs through the lone pair of sulfur... 

In view of the difference of a factor of 10 or more in peak delay between butene and thiophene at similar temperatures, butene adsorption was checked to see that chemisorption was in fact occurring below 200° C. Using the 50-foot propylene carbonate column, it was found that some butane was formed in spite of the H2S present down to 150° C. (without H2S butene was almost completely hydrogenated at this temperature) and both cis-trans and double bond isomerization of the butenes went to completion at temperatures below 100° C., indicating that chemisorption of butene must have occurred. It is therefore felt that extrapolation of the butene sorption results obtained to the temperature range of the desulfurization reaction (above 200° C.) should be valid. 

First results on n-complexation sorbents for desulfurization with Ag-Y and Cu(I)-Y zeolites have been reported recently [3,4]. In this work, we included the known commercial sorbents such as Na-Y, Na-ZSMS, H-USY, activated carbon and activated alumina (Alcoa Selexsorb) and made a direct comparison with Cu(l)-Y and Ag-Y which were the sorbents with n-complexation capability. Thiophene and benzene vapors were used as the model system for desulfurization. Although most of these studies can be applied directly to liquid phase problems, Cu-Y (auto-reduced) and Ag-Y zeolites were also used to separate liquid mixtures of thiophene/benzene, thiophene/n-octane, and thiophene/benzene/n-octane at room temperature and atmospheric pressure using fixed-bed adsorption/breakthrough techniques. These mixtures were chosen to understand the adsorption behavior of sulfur compounds present in hydrocarbon liquid mixtures and to study the performance of the adsorbents in the desulfurization of transportation fuels. Moreover, a technique for regeneration of the adsorbents was developed in this study [4]. 

Fig. 6.3 Calculated adsorption energies of carbon monoxide (a), atomic sulfur (b), sulfur dioxide (c) and thiophene (d) on the metal carbides (Ti carbides, V carbides and Mo carbides) as a function of the C/M ratio. The C/M values of 0.5, 1 and 1.5 correspond to bulk M C, bulk MC, and metcar M Cj, respectively. Reprinted with permission from [16]. Copyright 2004 by the American Institute of Physics...

Zhou, A.N., Ma, X.L., and Song, C.S. Liquid-phase adsorption of multi-ring thiophenic sulfur compounds on carbon materials with different surface properties. The Journal of Physical Chemistry. B, 2006, 110, 4699. 

As with all catalysts, palladium and its alloys are susceptible to poisoning [69]. Catalysts must be designed with resistance to poisoning, and proper precautions must be taken to minimize exposure of the membranes to catalyst poisons [69]. Typical poisons for palladium include H2S and other compounds of sulfur such as carbon disulfide (CS2), carbonyl sulfide (COS), aromatic thiophenes and mercap-tans (thiols, R-SH). Palladium is poisoned by the Group VA elements, P, As, Sb and Bi, the halides (Cl, Br, I), and Si, Pb and Hg. Alkenes and unsaturated organic compounds can poison palladium as can elemental carbon deposited from decomposition of carbonaceous materials. Carbon monoxide in high concentrations and at low temperatures can form a monolayer which blocks adsorption and dissociation of molecular hydrogen. Carbon monoxide can also decompose to produce car-... 

As already mentioned in the preceding section on Modes of Adsorption of Sulfur-Containing Compounds, thiophene can exhibit very different adsorption geometries. Indeed, thiophene can form sulfur bonded, jj -carbon, / -carbon, or f-(7r)-bonded complexes (159). 

As a result of very good adsorption capacity, active carbon has great desulfurization potential. The adsorptive removal of thiophene and dibenzothiophene from Hquid fuels was tested on modified active carbon. Activation with H2SO4 and HNO3 resulted in an increased desulfurization capacity [56-58]. Wang and Yang... 

C. Liang, F.Tian, Z. Li, Z. Feng, Z. Wei, and C. Li, 2003, Preparation and adsorption properties for thiophene of nanostructured W2C on ultrahigh-surface-area carbon materials, Chem. Mater., 15,4846-4853... 

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