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The hydrogenation of polyaromatic compounds (PACs) present in mineral oils is of great importance when it comes to the desired product properties and the minimization of health hazards; however, the presence of organonitrogen inhibits the conversion of these compounds. In this study, the inhibition effects of different types of organonitrogen compounds (acridine (ACR) and carbazole (CBZ)-basic and nonbasic organonitrogen) on the hydrodearomatization (HDA) of phenanthrene over a sulfided commercial NiMo/Al2O3 catalyst were investigated in a microflow trickle-bed reactor at a temperature range of 280 to 320 °C and at a total pressure of 120 barg. Analysis of the experimental results shows that the hydrogenation of phenanthrene is significantly decreased in the presence of organonitrogen, with acridine showing stronger inhibiting effects. The extent of hydrodenitrogenation (HDN) is shown to correlate with the inhibition degree with a higher extent of HDN being achieved for carbazole than for acridine. Results from co-feeding different nitrogen types (acridine and carbazole) indicate that basic nitrogen is the dominating type of organonitrogen inhibitor. Recovery of catalyst activity in the absence of organonitrogen indicates fully reversible deactivation suggesting that inhibition relates to competitive adsorption and slower reaction rate of HDN compared to HDA. [ABSTRACT FROM AUTHOR]

Fatty acid methyl ester (FAME) biodiesel contains some trace amounts of Na, K, P, Ca, and Mg. Our objective was to investigate whether the presence of such elements can poison a diesel oxidation catalyst that has been used for an entire regulatory lifetime in a heavy-duty truck fueled by FAME biodiesel. The investigated vehicle-aged catalyst contained high loadings of S, P, and Na, as well as a visible layer of soot. Activity in the NO oxidation reaction was severely decreased compared to a fresh catalyst of the same type, while the CO and C3H6 oxidation reactions were less affected. Subsequent selective trace element removal procedures, followed by activity tests, were used to decouple the effect of different poisons. Sintering was observed to be the main cause of catalyst deactivation. Of the trace elements present on the catalyst, P had the greatest effect on catalyst activity, while the other trace elements had little effect. [ABSTRACT FROM AUTHOR]

We have investigated how the exhaust gases from a heavy-duty Euro VI engine, powered with biogas impact a vanadium-based selective catalytic reduction (SCR) catalyst in terms of performance. A full Euro VI emission control system was used and the accumulation of catalyst poisons from the combustion was investigated for the up-stream particulate filter as well as the SCR catalyst. The NOx reduction performance in terms of standard, fast and NO2-rich SCR was evaluated before and after exposure to exhaust from a biogas-powered engine for 900 h. The SCR catalyst retains a significant part of its activity towards NOx reduction after exposure to biogas exhaust, likely due to capture of catalyst poisons on the up-stream components where the deactivation of the oxidation catalyst is especially profound. At lower temperatures some deactivation of the first part of the SCR catalyst was observed which could be explained by a considerably higher surface V4+/V5+ ratio for this sample compared to the other samples. The higher value indicates that the reoxidation of V4+ to V5+ is partially hindered, blocking the redox cycle for parts of the active sites. [ABSTRACT FROM AUTHOR]

• Phosphorus-exposure results in deactivation of both Cu-SSZ-13 and V 2 O 5 -WO 3 /TiO 2. • Cu-SSZ-13 is more severely deactivated by P than V 2 O 5 -WO 3 /TiO 2. • The low-temperature performance of Cu-SSZ-13 is severely suppressed by sulfur. • The SCR performance of V 2 O 5 -WO 3 /TiO 2 is slightly promoted by sulfur. • A DOC in front of the SCR catalyst protects this catalyst by capturing phosphorus. Two different SCR catalysts, V 2 O 5 -WO 3 /TiO 2 and Cu-SSZ-13, were exposed to biodiesel exhausts generated by a diesel burner. The effect of phosphorus and sulfur on the SCR performance of these catalysts was investigated by doping the fuel with P-, S-, or P + S-containing compounds. Elemental analyses showed that both catalysts captured phosphorus while only Cu-SSZ-13 captured sulfur. High molar P/V ratios, up to almost 3, were observed for V 2 O 5 -WO 3 /TiO 2 , while the highest P/Cu ratios observed were slightly above 1 for the Cu-SSZ-13 catalyst. Although the V 2 O 5 -WO 3 /TiO 2 catalyst captured more P than did the Cu-SSZ-13 catalyst, a higher degree of deactivation was observed for the latter, especially at low temperatures. For both catalysts, phosphorus exposure resulted in suppression of the SCR performance over the entire temperature range. Sulfur exposure, on the other hand, resulted in deactivation of the Cu-SSZ-13 catalyst mainly at temperatures below 300-350 °C. The use of an oxidation catalyst upstream of the SCR catalyst during the exhaust-exposure protects the SCR catalyst from phosphorus poisoning by capturing phosphorus. The results in this work will improve the understanding of chemical deactivation of SCR catalysts and aid in developing durable aftertreatment systems. [ABSTRACT FROM AUTHOR]

This study investigates the effect of biodiesel-derived contaminants on vanadia-based NH 3 -SCR catalysts in heavy-duty exhaust aftertreatment. The aim was to study, not only the effect of single contaminants on the catalyst performance, but also of possible interaction effects between poisons. The effect of six potential catalyst poisons (Na, K, Mg, P, S and Zn) was evaluated using an experimental design and multivariate data analysis. Monolithic V 2 O 5 -WO 3 /TiO 2 catalysts were subjected to accelerated laboratory-scale aging, where the six contaminants were fed simultaneously using a wet impregnation method. In addition to NO x conversion tests, the catalysts were characterized by means of ICP-OES, SEM-EDX, XPS, N 2 physisorption and NH 3 -TPD. The lab-aged samples were compared to fresh and vehicle-aged catalysts. The accelerated aging method showed good reproducibility and gave rise to surface compounds similar to those found in vehicle-aged catalysts. Despite plausible differences regarding penetration depth of the contaminants into the walls of the catalyst, the aging method appears to be an efficient way to point out significant chemical poisons. The model obtained from the experimental design was found to correlate well with the experimental data and can therefore be used to predict effects of the various poisons and poison interactions. Significant effects on the NO x conversion were found for P, S, Na, Mg and K as well as for the interactions P × Na, P × K and S × Na. A poisoning effect was found for Mg, Na, K, P × K, and P × Na, where Na and K exhibited the strongest poisoning effect. The deactivating effect of alkali was lowered in the presence of phosphorus and sulfur, which is explained by the formation of phosphates and sulfates, preventing the interaction of the alkali metals with the vanadia active sites. [ABSTRACT FROM AUTHOR]

• Suppressed redox and decreased long-distance movement of Cu-ions are seen for the SO 2 -poisoned catalyst in SCR-related gases. • Both ammonium and copper sulfates inhibit the reduction processes in the SO 2 -poisoned catalyst. • High structural disorder and differences in Cu-carbonyl species are observed for the SO 2 -poisoned catalyst compared to the fresh. • Developed an understanding of the nature of deactivation of the SO 2 -poisoned catalyst during standard NH 3 -SCR. • Revealed a possible deactivation pathway for the Cu-SSZ-13 catalyst in a combined LNT-SCR system. Fresh and SO 2 -poisoned Cu-SSZ-13 selective catalytic reduction (SCR) catalysts were studied using near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) in the presence of NH 3 , O 2 , and NO, as well as by in situ X-ray absorption spectroscopy (XAS) using H 2 , He, and CO. In contrast to the fresh catalyst, inhibited reduction of Cu-species and the absence of Cu-metal nanoparticles was found in the SO 2 -poisoned catalyst during heating/cooling in H 2 and CO. High structural disorder and differences in the formation of Cu-carbonyl species were seen for the SO 2 -poisoned catalyst compared to the fresh catalyst. Suppressed oxidation-reduction and low mobility of Cu-species during exposure to NH 3 -SCR-related gases were observed in the SO 2 -poisoned catalyst, unlike in the fresh catalyst. These observations help explain catalyst deactivation during the standard NH 3 -SCR reaction. The formation of Cu-metal nanoparticles in the fresh catalyst revealed another possible deactivation pathway for the SCR-catalyst in combined LNT-SCR systems during fuel-rich periods. [ABSTRACT FROM AUTHOR]

• Cu-SSZ-13 catalysts for SCR were studied as fresh and SO 2 -poisoned samples. • In-situ Cu K-edge XANES studies of the oxidation/reduction of Cu in these catalysts was correlated with SCR performance and catalyst characterization. • H 2 -TPR was used to determine Cu sites present in the catalyst. • Cu K-edge XANES spectra were used to follow oxidation and reduction of these Cu ion sites for fresh and SO2-poisoned samples. • Differences in the ease of Cu ion reduction is observed for fresh vs. SO2-poisoned samples in different temperature regions. SO 2 -poisoning results in deactivation of Cu-CHA SCR under standard SCR conditions; however regeneration at 700 °C completely restores the SCR performance. To understand the nature of these effects, Cu-species in the fresh and poisoned catalysts were characterized by in-situ temperature-dependent time-resolved Cu K-edge X-ray absorption spectroscopy using the multivariate curve resolution alternating least squares (MCR-ALS) approach and continuous Cauchy wavelet transforms. The extracted chemically-meaningful reference spectra of Cu-species were analyzed by DFT-assisted XANES calculations. Cu-bisulfates were found as the most energetically favorable poisoned Cu-species. The response of Cu-species to a reducing environment differs in the fresh and SO 2 -poisoned catalysts. Differences in reducibility are related to the formation of quasi-linear Cu-complexes in the SO 2 -poisoned catalyst formed during heating in H 2 /He. Heating in H 2 /He leads to partial desulfurization of the poisoned catalyst. Cooling in H 2 /He after heating results in more facile formation of Cu-metal clusters in fresh catalyst than in SO 2 -poisoned. [ABSTRACT FROM AUTHOR]