The Ostwald process is one of the commercial pathways for the production of nitric acid (HNO3), a key component in the production of nitrate fertilizers. The Ostwald process is a mature, extensively studied, and highly optimized process, and there is still room for further intensification. The process can be further intensified by catalyzing the homogeneous oxidation of nitric oxide to nitrogen dioxide. In this work, we explore the NO to NO2 oxidation capacity of ruthenium on gamma-Al2O3 support wash-coated on to a cordierite monolith. In a lab-scale setup with simulated feed comprising 10% NO, 6% O2, 15% H2O and rest Ar, and 8% NO, 2% NO2 5% O2, 15% H2O and rest Ar, the ruthenium and gamma-Al2O3 wash-coated monoliths attained a steady conversion of 72 and 56%, respectively. A remarkable steady conversion of 20% more than the gas phase for 65 h over 4 days was presented by the RuWc,gamma-Al2O3,Cordierite catalyst in one of the pilot plants at Yara, a Norwegian fertilizer company. The results presented in this work clearly provide evidence to support the idea that ruthenium on a gamma-alumina catalyst support can oxidize NO to NO2 under industrial nitric acid production conditions and mark an important step in the intensification of the Ostwald process.

Nitric acid is a key component in the production of nitrate fertilisers and is industrially produced using the Ostwald process. The Ostwald process can be further intensified by oxidising nitric oxide to nitrogen dioxide using heterogeneous catalysts. We have explored various monometallic and bimetallic catalysts for NO to NO2 oxidation and found ruthenium supported on ceria, containing 10 wt.% manganese to be a promising catalyst for oxidising NO to NO2 at low temperatures at industrially relevant conditions. For a feed comprising 10% NO, 6% O2, 15% H2O and rest Ar, and 8% NO, 2% NO2 5% O2, 15% H2O and rest Ar, the ruthenium-manganese catalysts attained NO-NO2 equilibrium below 400∘C. For the 5wt.% ruthenium and 10 wt.% manganese on ceria catalyst, an apparent activation energy of 39.4 kJ/mol and 85.4 kJ/mol were observed in the absence and presence of NO2, respectively. These findings demonstrate the potential of supported bimetallic ruthenium-manganese catalysts for efficient oxidation of NO to NO2 at low temperatures which can lead to significant process intensification of nitric acid plants.

Low-temperature nitric oxide oxidation using silver promoted manganese catalyst can reduce energy footprint of industrial nitric acid production.

Oxidation of nitric oxide is one of the main steps in the Ostwald process for industrial nitric acid production. This work summarises the use of gamma-Al2O3 supported Ru catalyst to study the oxidation of NO to NO2 at ambient and 4 bar pressure with a feed of 10% NO, 6% O-2, 15% H2O, and rest Ar. The catalyst was synthesised using wet impregnation and characterised by BET, CO chemisorption, H-2-TPR, XPS, XRD, in-situ XAS-XRD and DRIFTS. We report the activity and kinetics of supported ruthenium catalyst for NO oxidation under realistic nitric acid plant conditions. The catalyst exhibited a promising low-temperature activity of 72% at 340 degrees C in complete nitric acid condition and 37% at 420 degrees C in partial nitric acid condition. An apparent activation energy of 152 kJ/mol was observed and the overall rate was determined to be r = k(f) center dot K-G center dot P-NO(2) center dot P-O2/P-NO(2), where k(f) and K-G represents forward rate and equilibrium rate constants respectively. The reaction was found to be second order with respect to NO, first order with respect to O-2 and inversely dependent on NO2 partial pressure. The stability of the catalyst was also tested during 45 h of isothermal NO oxidation at ambient pressure. From in-situ XAS-XRD and DRIFTS experiments it was revealed that during isothermal NO oxidation the reaction oscillates as the ruthenium surface goes through redox cycles. A plausible reaction mechanism that fits with our experimental observations and the oxidative nature of ruthenium is proposed. This study demonstrates and explains the capacity of supported ruthenium catalysts to oxidise NO to NO2 in industrial nitric acid production conditions.

Nitric acid (HNO3) is an important building block in the chemical industry. Industrial production takes place via the Ostwald process, where oxidation of NO to NO2 is one of the three chemical steps. The reaction is carried out as a homogeneous gas phase reaction. Introducing a catalyst for this reaction can lead to significant process intensification. A series of LaCo1−xMnxO3 (x = 0, 0.25, 0.5 and 1) and LaCo1−yNiyO3 (y = 0, 0.25, 0.50, 0.75 and 1) were synthesized by a sol-gel method and characterized using N2 adsorption, ex situ XRD, in situ XRD, SEM and TPR. All samples had low surface areas; between 8 and 12 m2/g. The formation of perovskites was confirmed by XRD. The crystallite size decreased linearly with the degree of substitution of Mn/Ni for partially doped samples. NO oxidation activity was tested using a feed (10% NO and 6% O2) that partly simulated nitric acid plant conditions. Amongst the undoped perovskites, LaCoO3 had the highest activity; with a conversion level of 24.9% at 350 °C; followed by LaNiO3 and LaMnO3. Substitution of LaCoO3 with 25% mol % Ni or Mn was found to be the optimum degree of substitution leading to an enhanced NO oxidation activity. The results showed that perovskites are promising catalysts for NO oxidation at industrial conditions.

Three catalyst supports containing from 84 to 100% alpha-alumina prepared by heat treatment of gamma-alumina have been impregnated with cobalt and rhenium. The catalysts were tested for Fischer-Tropsch synthesis (FTS) under dry and enhanced water vapor pressure conditions. Both activity and selectivity to higher hydrocarbons respond positive to water added or generated in situ by the reaction. A linear trend between formation of methane and C5+. products was found, but displaced to higher C5+, values compared to catalysts on gamma-alumina. Calculation of chain propagation probabilities (alpha(n)) for alpha-alumina supported catalysts discloses that the first step, characterized by alpha(1), increases the most under higher water partial pressure. Moreover, alpha(1) is significantly higher for alpha- compared to all gamma-alumina supports irrespective of pore sizes of the latter. These results are ascribed to suppression of hydrogen coverage on the cobalt surface, linked to more regular cobalt crystallites, accompanied by enhanced water assisted generation of CHx polymerization monomers. Surprisingly, the following alpha(2) probability is comparably low for alpha-alumina supports, although it increases significantly with water concentration. Linear correlations are found between each pair of parameters alpha(1), alpha(2), alpha(4)' and SC5+; giving support to a mechanistic model where all products are interlinked, including methane. Transients observed when water was added or removed from the system are ascribed to pore diffusion. Selectivities in these periods follow closely the general selectivity trends found for different process conditions. (C) 2019 Elsevier Inc. All rights reserved.

The oxidation of nitric oxide (NO) to nitrogen dioxide (NO2) is a key step both in NOx abatement technologies as well as in the Ostwald process for nitric acid production. A 1 wt.% Pt/Al2O3 catalyst was used to study oxidation of nitric oxide at two different concentrations of NO; 400 ppm NO (representative of engine exhaust treatment) and 10% NO (nitric acid plant). The catalyst was characterised using N-2 adsorption and CO chemisorption. The effect of temperature and feed concentration on catalytic activity was investigated. For a feed comprising of 10% NO and 6% O-2, Pt/Al2O3 exhibits significant catalytic activity above 300 degrees C. Addition of 15% H2O in the feed had an insignificant effect on activity of the catalyst. We report for the first time the kinetics for oxidation of NO to NO2 under nitric acid plant conditions. An apparent activation energy of 33 kJ/mol was observed. The rate equation for the overall reaction was determined to be r = k(f)K(G)(Po-2)(0.5), where k(f) is the forward rate constant. The reaction is independent of NO concentration while it has half order dependency on oxygen. The reaction mechanism which fits our experimental observation consists of dissociative adsorption of oxygen, associative adsorption of nitric oxide with desorption of nitrogen dioxide as the rate limiting step.

The long term effect of up to 10 ppm H2S was studied for Fischer–Tropsch conversion of syngas by catalytic testing at 240 °C, 5 bar, H2/CO = 2.1 and GHSV = 2400 Nml/gcat h. Sulphur was dosed after ~ 300 or ~ 1000 h time on stream and the effect was monitored using on-line GC. The activity declined, and the effect correlated to the concentration of H2S in the feed. However, dosing after ~ 1000 h caused a stronger effect than dosing after ~ 300 h. The effects of sulphur are significant with respect to operational risks and mitigation but are substantially less severe than for a standard Co-based catalyst operated at 20 bar for wax production. The spent catalyst consisted of a mixture of cubic (Co, Mn)O, hexagonal Co, Co2C and sulphurous deposits; mainly MnSO4. It could not be concluded that sulphur had a direct effect on product selectivity, but it may have impacted water-gas-shift activity, and sudden changes in shift activity was found to correlate to changes in hydrocarbon selectivity.

Modern wood stoves can achieve high efficiency and relatively low levels of harmful emissions. However, controlling wood logs' combustion remains challenging, and the emission levels of unburnt compounds are generally higher than for e.g. wood pellet stoves. One solution is to upgrade the fuel quality, enabling a more stable combustion process. Thermal upgrading of wood through carbonization yields the highest achievable quality of solid fuel from wood. In this work, two types of charcoal were tested in a commercially available wood stove at various loads, with and without a retrofitted custom-design catalytic converter. The test procedure was adapted from the Norwegian test standard NS 3058 for higher repeatability and comparison with existing data. Emission levels were continuously measured using both a conventional- and a FTIR gas analyser. Particle emissions were measured both using a dilution tunnel with a total filter and an Electric Low Pressure Impactor (ELPI).The test results show that for the selected stove, without any modifications, the emission performance for most of the measured compounds was in a similar range to wood logs. CO emissions were significantly higher, though with the addition of a catalytic converter, measured CO emissions could be cut by 74-83% on average. The test campaign demonstrates that combustion stability improvement and reduced heat output throughout a longer combustion time can be achieved by using charcoal in a wood stove, but highlights the need for both design and operational changes to reach commercial solutions. (C) 2017 The Authors. Published by Elsevier Ltd.

Recent and ongoing research on F ischer– T ropsch catalysts for biomass conversion typically focus on the effects of impurities common in bio‐derived synthesis gas, and also on the effect of different synthesis gas compositions expected from biomass gasifiers. Cobalt and iron catalysts share the sensitivity toward some, but not all of the impurities. The most profound difference is the strong negative effect of alkali, alkaline earth, and nitrogen containing compounds on cobalt catalysts while these impurities have a negligible or no effect on iron catalysts. CO 2 appears to mainly act as a diluent in cobalt‐based processes while iron catalysts respond differently to this component depending on catalyst design. In particular, iron catalysts containing A l 2 O 3 as a structural promoter display a high stability, C 5+ selectivity, and activity in CO 2 rich synthesis gas. This article is categorized under: Bioenergy > Science and Materials

Cobalt and rhenium promoted cobalt catalysts with particle sizes in the range 7–40nm, supported on different modified aluminas, were investigated for CO hydrogenation. Steady-state isotopic transient kinetic analysis (SSITKA) was carried out at 483K, 1.85bar, and H2/CO/inert=15/1.5/33.5Nml/min. A loading-dependent adverse effect of zinc was found, and loss in methanation activity could be explained by an increased surface residence time of CHx (kCH4≡1/τCHx) and decreased selectivity to CH4. The surface concentration of CO (NCO) was largely unaffected by Zn and thus uncorrelated to activity. The relative effect of Zn on hydrocarbon formation decreased with increasing chain length, indicating that hydrogenation was more strongly affected than chain propagation. In situ measurements prior to and during CO hydrogenation suggested that the surface was largely covered by monomeric carbon species experiencing competitive adsorption from other species. As expected, no particle size effect was observed.

Elementary reactions that are relevant to catalytic hydrogen production have been evaluated over a wide range of transition metals. The UBI-QEP formalism was used to estimate heats of chemisorption and activation energies. The reactions were evaluated on a clean surface with the primary purpose of illustrating relative differences of intrinsic properties. The results were supportive of what is typically observed experimentally, in particular with respect to the relative difference between classical combustion catalysts (Pt, Pd) and state-of-art reforming catalysts (Ni, Rh). The likely scrambling of CHx species was also predicted which is in accordance with isotopic tracer studies in the literature.

Nickel has been reviewed as a catalyst and promoter in the Fischer-Tropsch synthesis (FTS). The main obstacle to its industrial application is the formation of volatile carbonyls, causing deactivation and loss of active phase, as well as a somewhat lighter product than from Co or Fe catalysts. Presented are both experimental and theoretical work pointing to suitable techniques for catalyst preparation, its composition and activation, as well as operating conditions where Ni is capable of producing long chain hydrocarbons in the FTS. Some important perspectives are also provided based on thermodynamic calculations and suggestions for further work are included.

The effect of 10 typical biomass-derived synthesis gas impurities on cobalt Fischer–Tropsch catalyst performance was investigated at industrially relevant conditions. Impurities (0–1000 ppmw) were introduced ex situ by incipient wetness impregnation to give 23 different compositions. The presence of alkali (Na, K) and alkaline earth elements (Ca, Mg) did not affect the ex situ-measured cobalt surface area but decreased the in situ activity, thereby decreasing the apparent turnover frequency. The C5+ selectivity increased and decreased upon addition of alkali and alkaline earth metals, respectively. Mn, Fe, and P had minor effects on catalyst performance. The presence of Cl decreased cobalt surface without affecting activity, thus increasing the turnover frequency. The changes in turnover frequency correlated with element electronegativity. In situ addition of H2S and (CH3)2S (2.5–10 ppm) decreased activity at all concentrations. However, product selectivity was not affected. Addition of NH3 (4 ppm) did not change catalytic performance.

Catalytic partial oxidation (CPO) of CH4 in air was investigated over Rh/Al2O3 catalysts (0.01, 0.05, 0.1 and 1 wt% Rh0) in co-feed modus in laboratory scale fixed-bed reactors. Main focus was on catalyst stability and selectivity at low temperatures (<700 °C). A particularly high selectivity to CO was observed, indicating existence of a direct pathway.

The effect of different modifications (Zn, Mg, Ni, Re) has been studied for alumina-supported 12 wt% Co-catalysts in the Fischer–Tropsch synthesis (FTS) using a fixed-bed reactor at 483 K, 20 bar, and H2/CO = 2. Different parameters including calcination temperature, loading, impregnation sequence, and water partial pressure during FTS have been studied. When compared to low surface area α-Al2O3, mechanical strength was substantially improved for Ni- and Mg-modified aluminas calcined at very high temperatures (>1400 K), thus making them more suitable for slurry or fluidized-bed operation. However, Mg was found to have a loading-dependent negative effect on both activity and selectivity. The wt% effect was stronger when co-impregnated with Co–Re and calcined at 773 K, than when impregnated on the support and calcined at a high temperature (1173 K) prior to impregnation with Co–Re. Co-impregnating Co–Re with Zn also had a strong loading-dependent negative effect on activity and selectivity, while impregnating Zn on the support and calcining at a high temperature (1173 K) prior to impregnation with Co–Re had no negative effect on the overall C5+ yield. The negative effects of Mg and Zn could not be explained by dispersion or particle size effects and were likely related to a chemical/site effect similar to that of alkalies reported on in the literature. The effect of water for the Ni-modified support was in accordance with the literature, improving reaction rates and C5+ selectivity, while inhibiting olefin hydrogenation, as demonstrated by the propene/propane ratio. The catalysts were characterized with H2 chemisorption, N2 sorption, mercury intrusion, X-ray diffraction, temperature-programmed reduction, and O2 titration.

We here illustrate the potential of inactive Ni- and Ni–Co aluminate spinels prepared at high temperatures (1393K) as precursors for the design of catalysts for partial oxidation (CPO) and steam methane reforming (SMR). By exposing the aluminate spinel to hydrogen atmosphere at 1073K for 2h, the inactive spinel was restructured to an active catalyst with excellent initial stability (20–40h). The hydrogen treatment enabled the growth of supported nano-sized (15–25nm) metal particles.