Sulfur thermal-chemical removal from

The samples which were cured chemically with acetic anhydride and pyridine, and then heated to remove solvent, appeared to be incompletely imidized, and yielded lower molecular weights than thermally cured samples from the same polyamic acid. In addition, these samples produced a bright red solution in sulfuric acid, in contrast to the orange-gold color observed in solutions from thermally cured samples. The red color disappeared within 24 hours, when the molecular weights were determined. This color was also observed by Wallach (4), who carried out viscosity measurements on sulfuric acid solutions of chemically cured PMDA/DAPE polyimides. Wallach observed a slow decrease in the dilute solution viscosity with time over a period of hours from the initial preparation of the solution. We have not observed any decrease in viscosity for 24 hours for solutions prepared from thermally cured samples. Polyimide samples which have been cured chemically have been shown to contain a small percentage of isoimide, which is then converted to the more stable imide at higher temperatures (8-9). The observed red color in sulfuric acid solutions may be because protonation of... 

Description The SUPERFLEX process is a proprietary technology patented by ARCO Chemical Technology, Inc. (now LyondellBasell) and exclusively offered worldwide for license by KBR. It uses a fluidized catalytic reactor system with a proprietary catalyst to convert low-value feedstocks to predominantly propylene and ethylene products. The catalyst is very robust thus, no feed pretreatment is required for typical contaminants such as sulfur, water, oxygenates or nitrogen. Attractive feedstocks include C4 and C5 olefin-rich streams from ethylene plants, FCC naphthas or C4S, thermally cracked naphthas from visbreakers or cokers, BTX or MTBE raffinates, olefin-rich streams removed from motor gasolines, and Fischer-Tropsch light liquids. 

GRT of particle sizes from 1 to 3 mm was treated by applying thermal, chemical, and combined thermal and chemical treatments to prepare carbonaceous adsorbents for removal of mercury in aqueous solution (Gupta et al., 2011). The adsorbents were prepared by heating the rubber at 400 or 900 C for 2 h in the nitrogen atmosphere and then chemically treating with sulfuric acid, nitric acid, or their mixer solutions for 24 h. The heat treatment of the rubber developed mainly the microporosity, particularly the mesoporosity. The chemical treatment provided the creation of macropores. In the combined heat and chemical treatments, the predominant effects on the porous structure were caused by the treatment that provided the first effect. The adsorption capacity of mercury was larger for the adsorbents of higher microporosity. 

CH3(CH2CH20) CH3, where n is between 3 and 9. The Selexol solvent is chemically and thermally stable, and has a low vapor pressure that limits its losses to the treated gas. The solvent has a high solubility for C02, H2S, and COS. It also has an appreciable selectivity for H2S over C02. The sulfur content of the purified syngas from the Selexol absorber can be lower than 5ppmv. For a higher level of sulfur removal for downstream catalytic conversion, a guard bed using ZnO sorbents is usually required. 

The properties of the spent sulfuric acid vary widely. It might be acid, which is diluted but otherwise uncontaminated, to acid, which is less concentrated and contaminated with metals or other impurities, to acid which is both diluted and contaminated. Measures for recovery and recycle therefore vary in complexity from simple reconcentration, to water removal accompanied by chemical purification steps. Occasionally, thermal destruction of impurities accompanied by dissociation of the acid and recycle of the sulfur content for acid remanufacture may be required. For these reasons the appropriate acid recycle method depends on the use of the original acid, and the condition of the spent acid obtained. Specific examples follow. 

Results indicate that, far from being a necessary part of the active center as has sometimes been proposed, these hydroxyls may actually interfeiewith the active site. Hydroxyls could be removed by chemical as well as by thermal means to improve activity and melt index potential, such as by treating the catalyst in carbon monoxide, sulfur, or halides. 

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