Several materials in the class of metal-organic frameworks (MOF) were investigated to determine their sorption characteristics for sulfur compounds from fuels. The materials were tested using different model oils and common fuels such as low-sulfur gasoline or diesel fuel at room temperature and ambient pressure. Thiophene and tetrahydrothiophene (THT) were chosen as model substances. Total-sulfur concentrations in the model oils ranged from 30 mg/kg (S from thiophene) to 9 mg/kg (S from tetrahydrothiophene) as determined by elementary analysis. Initial sulfur contents of 8 mg/kg and 10 mg/kg were identified for lowsulfur gasoline and for diesel fuel, respectively, by analysis of the common liquid fuels. Most of the MOF materials examined were not suitable for use as sulfur adsorbers. However, a high efficiency for sulfur removal from fuels and model oils was noticed for a special copper-containing MOF (copper benzene-1,3,5-tricarboxylate, Cu-BTC-MOF). By use of this material, 78 wt % of the sulfur content was removed from thiophene containing model oils and an even higher decrease of up to 86 wt % was obtained for THT-based model oils. Moreover, the sulfur content of low-sulfur gasoline was reduced to 6.5 mg/kg, which represented a decrease of more than 22 %. The sulfur level in diesel fuel was reduced by an extent of 13 wt %. Time-resolved measurements demonstrated that the sulfur-sorption mainly occurs in the first 60 min after contact with the adsorbent, so that the total time span of the desulfurization process can be limited to 1 h. Therefore, this material seems to be highly suitable for sulfur reduction in commercial fuels in order to meet regulatory requirements and demands for automotive exhaust catalysis-systems or exhaust gas sensors. IntroductionThe reduction in the level of sulfur compounds in commercial gasoline and diesel fuels is a major concern of the petrol, automotive and power generation industries. This aim is a necessity not only to meet regulatory requirements but also to enhance the life-time of exhaust gas aftertreatment systems and sensors or fuel cell components. Consequently, there is an increasing demand for ultra-low sulfur fuels (preferably down to 0.1 ppmw S ) [1].As a legal guideline, the European Union has mandated the reduction of sulfur levels (S-levels) in gasoline and diesel fuels to 10 mg/kg S (10 ppmw S ) by 2009 (directive 2003/17/EC). In addition, S-levels in diesel fuel for traction engines and heating purposes was reduced from the original value of 2000 mg/kg to 1000 mg/kg in 2008 [2]. Analog regulations of the federal government of the US and the EPA (U.S. Environmental Protection Agency) are proposing the implementation of ultralow sulfur diesel fuel with 15 ppmw S for 2010 [3, 4]. Similar to the EU proposals, the German government has also enacted the introduction of sulfur-free fuel (with a maximum tolerable level of sulfur of 10 mg/kg) in 2009 (Order 10. BImSchV) [5]. In order to meet these worldwide demands, oil refiners have been endeavoring to promote sulfur r...

We report on the long-term stability of the electrochemical reduction of CO 2 at copper sheet electrodes by continuously applying rectangular, pulsed voltage cycles in series. Each pulse cycle consisted of an anodic and a cathodic voltage level. The parameters of the pulse cycle were systematically modified: cathodic (−1.5...−1.8 V) and anodic voltage levels (−0.88...+0.15 V), and ratio of anodic to cathodic pulse duration (5 s:5 s...5 s:500 s). The electrolysis runs were conducted in a divided H-cell. Volatile reaction products (CO, CH 4 , C 2 H 4 , H 2 ) were analyzed with a gas chromatograph in intervals of 7.3 min. We achieved fairly stable faradaic efficiencies (FE) for hydrocarbon formation in the range of 20 to 35% FE for C 2 H 4 and 20 to 50% FE for CH 4 during 16 h of electrolysis and a remarkable suppression of hydrogen evolution reaction (HER) down to 10% FE. Additionally, we show data of two long-term electrolysis runs of 85 h and 95 h duration, respectively. Even for this prolonged electrolysis times, an outstanding, fairly constant suppression of HER and a high efficiency for the formation of carbon containing gaseous products (CO, CH 4 , C 2 H 4 ) was achieved.

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