Lubrication base oils are produced in hydrotreaters using a wide range of feedstocks and process conditions. When either the feedstock or process conditions are changed, the catalyst activity appears to change requiring several days of operation to reach a stable activity state. In the present study, a feedstock switch is performed in a pilot hydrotreating unit using light and heavy vacuum gas oils (LVGO and HVGO), to investigate the transient reactor's behaviour and catalyst activity. To decouple the hydrodynamic and the kinetic effects, a tracer study was conducted utilizing standard refinery analytical methods. The obtained transient data was described and explained by a simplified mathematical model accounting for the hydrodenitrogenation (HDN) and hydrodearomatization (HDA) reactions. The experimental results indicate that the sequence of feedstock switch impacts the time to steady state with the LVGO to HVGO switch reaching a steady state after 40 h while the HVGO to LVGO required only 20 h. Moreover, the average boiling point (T50) was found to be a suitable tracer for characterizing the reactor's hydrodynamics. The developed model exhibited a good fit to the transient data obtained from the pilot unit. It was shown that the dynamics of the HDA closely follow those of HDN. Moreover, the adsorption rate coefficient and the HDN reaction rate coefficient were 30 % and 12 % higher, respectively, for the LVGO compared to the HVGO. In conclusion, this study provides a quantitative understanding of the feedstock switch supporting the optimization of hydrotreaters operation.

The selection of appropriate catalysts is critical for the efficient operation of hydrotreaters, due to the diverse types of reactions inherent to the process. In this study, various Type I and Type II sulfided NiMo/γ-Al<inf>2</inf>O<inf>3</inf> hydrotreating catalysts were prepared using chelating agents and support modification, and the apparent activity differences were evaluated using step response experiments. The experiments were conducted in a trickle bed reactor at 300 °C and 120 barg using phenanthrene and carbazole as model compounds while the apparent activities were elucidated using dynamic reactor modelling. It was found that the addition of citric acid to the impregnation solution to chelate the Ni leads to an average 30% increase in the active site density for hydrogenation (HDA) and hydrodenitrogenation (HDN), without significantly affecting the reaction rate coefficients suggesting similar activity per active site. Phosphorus modification of the support, however, results in larger reaction rate coefficients for both hydrogenation of phenanthrene as well as adsorption and reaction coefficients for carbazole, resulting in more active catalysts both for HDA and HDN. This enhanced activity is accompanied by increased selectivity to HDN suggesting that catalysts exhibiting higher activity for HDA reactions are more susceptible to inhibition by organonitrogen compounds. In addition, dynamic activity testing indicated that catalysts with superior HDN activity attain their new steady state in the shortest time. Thus, the selection of catalysts for efficient hydrotreater operation necessitates activity testing under dynamic conditions to account for competing and inhibitory reactions, rather than relying solely on steady-state activity. Such an approach, allows for the elucidation of the differences in HDA and HDN activity, providing valuable insights to support the catalyst selection process.

Oxidation catalysts can greatly improve the regeneration efficiency of diesel particulate filters (DPF) by providing sufficient levels of NO₂ for low-temperature soot oxidation. As for other automotive catalysts, catalyzed DPFs are subject to aging effects, resulting in decreased performance of the NO oxidation reaction. The life span of DPFs generally only considers the elevated back pressure as a consequence of the accumulation of ash. However, with reduced catalytic activity and impaired functionality of the regeneration process there is a risk of premature replacement of the catalyzed DPF or accumulation of soot above critical levels. In this study, a new exhaust aftertreatment system has been developed to accommodate laboratory-scale catalysts and DPFs for testing with full-size heavy-duty engines. The modified exhaust aftertreatment set-up was used together with a rig for accelerated soot and ash loading to assess the impact of catalyst aging on regeneration performance under real conditions. Experiments were conducted with and without diesel oxidation catalyst to limit or increase the concentration of NO₂. It could be demonstrated that the impaired catalytic activity can have a significant impact on the regeneration process. With a limited upstream concentration of NO₂ fed to the catalyzed DPF, a temperature increase from about 390 °C to 450 °C was required to initiate the oxidation of soot. Furthermore, an overall lower oxidation rate was observed. With the addition of a diesel oxidation catalyst, resulting in elevated upstream concentrations of NO₂, the effect of aging could be partially mitigated leading to more comparable soot oxidation rates with a temperature difference of 30 °C for soot ignition. These results highlight the importance of the catalytic activity for the functionality of the system, which should be considered for future catalyzed DPF design and regeneration strategies.

Low-temperature soot oxidation in catalytic diesel particulate filters (DPF) is important for maintaining high efficiency of heavy-duty vehicles. This can be achieved by coating DPFs with an oxidation catalyst. In this work, catalytic DPFs have been collected from real-world operating heavy-duty vehicles for assessment of their catalytic activity and subsequent characterization. Testing of catalytic activity revealed the diminishing nitric oxide (NO) oxidation of the aged catalysts. The apparent reaction rates showed that the number of available catalytic sites decreased with mileage explaining the loss in activity. Characterization of the samples showed a decreasing surface area as well as an accumulation of metals and poisonous elements. An important finding from SEM-EDS analysis is the evident accumulation of phosphorus and sulfur in the washcoat in the absence of other ash-related elements, potentially explaining the decreased activity.

Increasing concern for air pollution together with the introduction of new types of fuels pose new challenges to the exhaust aftertreatment system for heavy-duty (HD) vehicles. For diesel-powered engines, emissions of particulate matter (PM) is one of the main drawbacks due to its effect on health. To mitigate the tailpipe emissions of PM, heavy-duty vehicles are since Euro V equipped with a diesel particulate filter (DPF). The accumulation of particles causes flow restriction resulting in fuel penalties and decreased vehicle performance. Understanding the properties of PM produced during engine operation is important for the development and optimized control of the DPF. This study has focused on assessing the reactivity of the PM by measuring the oxidation kinetics of the carbonaceous fraction. PM was sampled from two different heavy-duty engines during various test cycles. The heavy-duty engines were 6- and 8-cylinder direct injection diesel engines rated at 550 and 650 hp respectively. Reaction kinetics of the samples and characteristic oxidation temperatures were assessed by the non-isothermal thermogravimetric analysis (TGA) employing a multiple-ramp rates method in a 10% oxygen atmosphere. The oxidation of the diesel soot was compared with a model soot, Printex-U, and values were compared with the existing literature. The calculated activation energies range between 114.8 and 155.8 kJ/mol for diesel soot as well as the Printex-U samples indicating similar reactivity despite differences in engine configuration, fuel chemistry or, aging.

Noble metal-exchanged small-pore molecular sieves withchabazite topology are promising materials for automotive cold-start NOxemission control applications. A combination offirst-principles thermody-namics and density functional theory was applied for the prediction ofmonomeric palladium, platinum, and ruthenium species formed in 1Al or 2Alsites of six-/eight-membered rings of the SSZ-13 framework in the presenceof SO2, NO, O2, and H2O at temperatures between 0 and 1100 K.Calculations using gradient-corrected Perdew-Burke-Ernzerhof (PBE)functional and hybrid Heyd-Scuseria-Ernzerhof (HSE06) functionalshowed that the binding energy of NO adsorbed on Pd, Pt, or Ru ions is astrong function of exchange-correlation functional. Use of the PBEfunctional overestimated the binding strengths of NO to Pd, Pt, or Ru ions compared to the HSE06 functional. While PBE ledto the adsorption of two NO per Pd, Pt, or Ru ion, HSE06 predicted the adsorption of a single NO. Isolated Pd, Pt, or Ru ions in 1Alsites tended to bind NO stronger than their counterparts in 2Al sites. Both functionals revealed that Pd and Pt ions have moresimilarities in terms of both NO adsorption and sulfur resistance compared to Ru ions. The results of this study are beneficial forfurther modeling of passive NOxadsorbers with improved properties to deliver cleaner tailpipe emissions during engine cold start

Biodiesel is a promising renewable fuel, which may help to limit our dependence on fossil fuels. However, the presence of contaminants in biodiesel can affect the Cu speciation of the Cu-SSZ-13 selective catalytic reduction (SCR) catalyst, resulting in its deactivation and decreased durability. In situ Cu K-edge X-ray absorption fine structure (XAFS) scanning during a temperature-programmed reduction in hydrogen (H-2-TPR) has been applied here for the analysis of Cu speciation in Cu-SSZ-13 catalysts aged using pure and contaminated biodiesel fuels. XAFS data were analyzed using the multivariate curve resolution alternating least-squares (MCR-ALS) method. While only reduction from Cu-II to Cu-I was observed at temperatures below 500 degrees C for the catalyst aged using pure biodiesel, a one-step reduction of Cu-II to Cu-0 at temperatures between 400 and 500 degrees C was found for the catalyst aged using P-doped biodiesel. The transformation of isolated CuII species to Cu-II clusters was suggested for the catalyst as a result of aging using P-doped biodiesel. The catalyst aged using S-doped biodiesel showed mainly the reduction of isolated Cu-II to Cu-I, which was inhibited as compared to that observed for the catalyst aged using pure biodiesel. The reduction of the catalyst aged using P+S-doped biodiesel led to the reduction of Cu-II to both Cu-I and Cu-0. The phosphorus was responsible for the formation of Cu-II clusters during aging of the catalyst using P+S-doped biodiesel. This study reveals that the presence of phosphorus in biofuels should be strictly regulated to avoid major changes in the Cu speciation of Cu-SSZ-13 catalysts.

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 degrees 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.

Fresh and SO₂-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 NH₃, O₂, and NO, as well as by in situ X-ray absorption spectroscopy (XAS) using H₂, 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 SO₂-poisoned catalyst during heating/cooling in H₂ and CO. High structural disorder and differences in the formation of Cu-carbonyl species were seen for the SO₂-poisoned catalyst compared to the fresh catalyst. Suppressed oxidation-reduction and low mobility of Cu-species during exposure to NH₃-SCR-related gases were observed in the SO₂-poisoned catalyst, unlike in the fresh catalyst. These observations help explain catalyst deactivation during the standard NH₃-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.

Two different SCR catalysts, V2O5-WO3/TiO2 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 V2O5-WO3/TiO2, while the highest P/Cu ratios observed were slightly above 1 for the Cu-SSZ-13 catalyst. Although the V2O5-WO3/TiO2 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.