High Initial Conversion Research Articles

Immobilization study of a monomeric oleate hydratase from Rhodococcus erythropolis

AbstractThe chemical, pharmaceutical, and cosmetic industries are currently confronted with the challenge of transitioning from traditional chemical processes to more sustainable biocatalytic methods. To support that aim, we developed various heterogeneous biocatalysts for an industrially relevant enzyme called oleate hydratase that converts oleic acid to 10-hydroxystearic acid, a fatty emollient substance useful for various technical applications. We used cheap support matrices such as silica, chitosan, cellulose, and agarose for further scale-up and economic feasibility at the industrial level alongside more sophisticated supports like metal–organic frameworks. Different physical and chemical binding approaches were employed. Particularly, by immobilizing oleate hydrates on a 3-aminopropyltriethoxysilane surface-functionalized cellulose matrix, we developed an enzyme immobilizate with almost 80% activity of the free enzyme. The long-term goal of this work was to be able to use the developed heterogeneous biocatalyst for multiple reuse cycles enabling profitable biocatalysis. Despite high initial conversion rate by the developed cellulose-based immobilizate, a depletion in enzyme activity of immobilized oleate hydratase was observed over time. Therefore, further enzyme modification is required to impart stability, the optimization of operational conditions, and the development of carrier materials that enable economical and sustainable enzymatic conversion of oleic acid to meet the commercial demand. Graphical abstract

Pt confined in Sn-ECNU-46 zeolite for efficient alkane dehydrogenation

Highly dispersed and stable Pt-based catalysts play a crucial role in constructing efficient catalytic systems for alkane dehydrogenation. In this study, a novel bimetallic Pt–Sn catalyst confined in extra-large-pore ECNU-46 zeolite (denoted as Pt/Sn-ECNU-46) is prepared by post-treatment. The open-site framework Sn species ((SiO)3Sn–OH) serve as anchors to interact with Pt species, favoring the high dispersion of Pt. On the other hand, the framework Sn species act as the second metal to regulate the geometrical and electronic environment of Pt species, thus suppressing their accumulation. Pt/Sn-ECNU-46 achieves a good performance in propane dehydrogenation reaction with high initial propane conversion (46%) and propylene selectivity (> 99%) as well as regeneration ability. In addition, Pt/Sn-ECNU-46 is also active in the dehydrogenation of n-hexane. This study explores the application of extra-large-pore zeolite as support in constructing metal-confined catalysts for alkane dehydrogenation.

Development of cyanate ester-oligosiloxane copolymers for deployable satellite applications

Binary blends of an α,ω-hydroxyoligosiloxane (with degree of polymerization, n = 39) with an oligomeric cyanate ester (Primaset™ PT-30, 1) are prepared as microphase-separated, monolithic samples. The uncured blends display complex viscosities of 21–97 Pa s at 30 °C depending on composition, rendering them suitable for infusion processes at 70 °C. This α,ω-hydroxyoligosiloxane undergoes co-reaction with (1) to yield network structures. Initiation using copper(II) acetylacetonate/nonylphenol reduces the onset of polymerization of the 190210 binary blend by some 99 °C and a value of 61–62 kJ/mol cyanate groups is obtained for the ucatalyzed polymerization of the homopolymer (1) and the binary blend 19525, while there was little difference in the enthalpy when catalyzed with copper (64 kJ/mol. OCN), cobalt (66 kJ/mol. OCN), and iron (60 kJ/mol. OCN), although the shape of the exotherm and thus the mechanism were changed significantly. A short initial cure cycle (170 °C, 1 h) effects a high initial conversion of >80 %, while a second post cure step (200 °C 1 h) yields an ultimate conversion of at least 93 %. The cured binary 190210 binary blend displays good thermal stability (Tdec5% = 429 °C and char yield = 62.4 % at 800 °C, compared with (Tdec5% = 433 °C and char yield = 68.0 % at 800 °C).

Hexanary blends: a strategy towards thermally stable organic photovoltaics

Non-fullerene based organic solar cells display a high initial power conversion efficiency but continue to suffer from poor thermal stability, especially in case of devices with thick active layers. Mixing of five structurally similar acceptors with similar electron affinities, and blending with a donor polymer is explored, yielding devices with a power conversion efficiency of up to 17.6%. The hexanary device performance is unaffected by thermal annealing of the bulk-heterojunction active layer for at least 23 days at 130 °C in the dark and an inert atmosphere. Moreover, hexanary blends offer a high degree of thermal stability for an active layer thickness of up to 390 nm, which is advantageous for high-throughput processing of organic solar cells. Here, a generic strategy based on multi-component acceptor mixtures is presented that permits to considerably improve the thermal stability of non-fullerene based devices and thus paves the way for large-area organic solar cells.

Niobium- and Tantalum-Doped Pt-Sn/Al2 O3 as Efficient Catalysts for Propane Dehydrogenation.

The Pt-Sn/Al2 O3 catalyst has been successfully commercialized for propane dehydrogenation, but it is still highly desirable to further improve its catalytic performance for maximizing the utilization efficiency of noble metal Pt. Herein, this work demonstrates that doping Nb and Ta into Pt-Sn/Al2 O3 has great impacts on its structure, and significantly improved catalytic performances are achieved in Pt-Sn-X/Al2 O3 (X=Nb and Ta). It is found that the incorporation of Nb and Ta into Pt-Sn/Al2 O3 can promote the dispersion of Pt-Sn particles, which results in Pt-Sn clusters being highly dispersed at the surface of Al2 O3 . Moreover, the presence of Nb and Ta makes the SnOx species less reducible, and thus the Pt-Sn particles become more stable at high temperature. Systematic exploration allows to obtain the optimized Pt-Sn-Nb5.0 /Al2 O3 and Pt-Sn-Ta1.0 /Al2 O3 , and these two catalysts exhibit high initial propane conversion (above 43.8 % and 50.4 %) with propylene selectivity of above 98 %. Most importantly, they show excellent regeneration in propane dehydrogenation, and their catalytic performance can be completely restored by a simple calcination.

Barrier identification, analysis and solutions of hydrogen energy storage application in multiple power scenarios based on improved DEMATAL-ISM approach

China is ambitiously moving towards “carbon emission peak” and “carbon neutral” targets, and the power sector is in the vanguard. The coordination of power and hydrogen energy storage (HES) can improve energy utilization rate, promoting the deep decarbonization of power industry and realizing energy cascade utilization. However, limited by technology, cost, environment, society and other factors there are few application projects. Identifying major barriers and eliminating unimportant factors can make problem solving more efficient. Decision-making trial and evaluation laboratory (DEMATEL) combined with interpretative structural modeling (ISM) method is innovatively used to establish a barrier analysis framework for HES applied in multiple power scenarios. This method can show the direction and degree of the impact relationship between barriers and determine key ones, which is conducive to presenting targeted and effective solutions. Additionally, the interval type-2 fuzzy set (IT2FS) is introduced to reduce the distortion of evaluation information and ensure the rationality of analysis. Specifically, a comprehensive barrier system taking into account both commonalities and characteristics is established firstly. For different decision considerations, four typical power scenarios are screened to better illustrate how critical barriers play different roles in different scenarios. Then, the proposed analytical framework is applied to identify the key barriers in each scenario and find out the interlinking relationship among the barriers. The results suggest that technical barriers tend to dominate the fundamental barriers. Among that, immature hydrogen storage and transportation technology is a prevalent and fundamental barrier. Besides, high initial investment cost and high P2X conversion costs are crucial reasons that prevent relevant investors from entering the market. And inadequate policy has led to a poor environment for HES development. It's worth noting that, other key barriers focused on each scenario are not the same, and also are discussed in detail in this study. Finally, comprehensive solutions and policy suggestions to eliminate or reduce the barriers are presented.

Efficient Non‐Precious Metal Catalyst for Propane Dehydrogenation: Atomically Dispersed Cobalt‐nitrogen Compounds on Carbon Nanotubes

AbstractA hybrid catalyst comprising atomically dispersed cobalt‐nitrogen compounds anchoring on oxidized carbon nanotubes (OCNTs) is prepared and applied in propane dehydrogenation (PDH) reactions. The proposed non‐precious catalyst exhibits high initial conversion (∼20 %) and excellent selectivity of propene (>95 %), which is superior to those of metal‐free nanocarbon and some metal‐based catalysts. The chemical composition and structure of the proposed hybrid catalysts are elucidated by a series of characterizations and control experiments with a single component. These characterization results combined with the kinetic analysis indicate that the catalytic activity mainly originates from the cobalt‐nitrogen (Co−N) species supported on the OCNT surface. The present work sheds light on the structure‐function relationships of CoN catalysts, paving the way to develop non‐precious catalysts for PDH reactions.

The reactivity and initial carbonization of an Unsupported Nickel catalyst in dry reforming of methane

High speed product gas analysis during the dry reforming of CH4 allows the observation of transient elevated H2 and CO production rates, combined with high initial conversions of CH4 and CO2. The transients are observed in the first 120 s of the reaction, followed by a lower steady-state production rate after 3–5 min. The catalytic reactivity in the initial 120 s is important in understanding the catalyst performance and determining the reactions responsible for carbon deposition. Monitoring the changes in the H2 and CH4 partial pressures from the start, through the transient production regime, and on through the steady-state regime, shows that the transient reactivity is directly related to the decomposition of CH4. This finding is further supported by the linear trend found between the H2/CO ratio and the carbon deposition in the peak region of the product gas profile. Although significant amounts of carbon are deposited on the Ni surface, it is not completely deactivated at any of the reaction temperatures in the 500–800 °C range explored herein. Characterizing the initial reactivity in terms of carbon deposition and catalyst performance in dry reforming of CH4 may lead to changes in the sampling technique for researchers working with reforming reactions, and optimized catalysts that exhibit reduced initial carbon deposition.

Flow Process for Ketone Reduction Using a Superabsorber-Immobilized Alcohol Dehydrogenase from Lactobacillus brevis in a Packed-Bed Reactor.

Flow processes and enzyme immobilization have gained much attention over the past few years in the field of biocatalytic process design. Downstream processes and enzyme stability can be immensely simplified and improved. In this work, we report the utilization of polymer network-entrapped enzymes and their applicability in flow processes. We focused on the superabsorber-based immobilization of an alcohol dehydrogenase (ADH) from Lactobacillus brevis and its application for a reduction of acetophenone. The applicability of this immobilization technique for a biotransformation running in a packed bed reactor was then demonstrated. Towards this end, the immobilized system was intensively studied, first in a batch mode, leading to >90% conversion within 24 h under optimized conditions. A subsequent transfer of this method into a flow process was conducted, resulting in very high initial conversions of up to 67% in such a continuously running process.

Effect of the preparation method on particle size and reaction selectivity on naphthalene hydrogenation over Ni/H-MOR catalysts

Three Ni catalyst supported on mordenite zeolite with the same content of nickel, ∼2 wt.%, were prepared by incipient wetness impregnation (IWI), ionic exchange (IE), and deposition-precipitation (DP) methods. The catalysts were characterized by, X-ray diffraction (XRD), textural properties, temperature-programmed reduction (TPR), transmission electron microscopy (TEM) and scanning electron microscopy / energy-dispersive spectroscopy (SEM/EDS). For all the catalysts conversion and selectivity were studied in naphthalene hydrogenation without or with thiophene in the feedstock. Despite the low nickel content, the three preparations showed a high initial total naphthalene conversion up to 94%. The Ni-IWI catalyst exhibited high selectivity to tetralin and deactivated very fast. Ni-IE catalyst had good activity; however, it shows deactivation and the main products are related to acid reactions. The Ni-DP shows high hydrogenation activity and was the most active catalyst, it generated decalins, especially cis-decalin and at a long reaction time on stream, the catalyst remains active. TEM and TPR results suggest that this behavior is related to the crystal sizes which in turn is conected with the preparation method. In presence of thiophene, all the catalysts deactivate; but the Ni-DP deactivation was slower.

Deactivation mechanism of activated carbon supported copper oxide SCR catalysts in C2H4 reductant

Current state‐of‐the‐art NH3‐SCR technology based on vanadium catalysts suffers problems associated with NH3 slip and poisoning of the catalyst and blockage of heat recovery steam generators (HRSG). If environmentally‐friendly catalysts capable of efficient operation at lower temperatures could be developed that used a reductant other than NH3, the issues with current state‐of‐the‐art SCR could be significantly lessened. Hence, in this study, activated carbon (AC) supported copper oxide‐based catalysts for SCR while using C2H4 as a reductant was discussed. Reaction testing of catalysts demonstrated high initial NO conversion with steeply declining activity over 2 h of testing when C2H4 was used as the reductant; in comparison, with the same catalyst and NH3 as the reductant, stable, long‐term NO conversion was achieved, but at a lower rate than the initial reactivity with C2H4. As a consequence, catalyst characterization studies were performed to assess deactivation mechanisms when C2H4 was the reductant. These studies included x‐ray diffraction, BET surface area and porosity, temperature programmed reduction, scanning electron microscopy, Raman spectroscopy and x‐ray photoelectron spectroscopy of both fresh and deactivated catalysts. The analytical results showed the surface area and porosity of the catalyst remained unchanged and the initially highly‐dispersed Cu species became agglomerated and more crystalline during reaction testing. Furthermore, carbon black was also detected on the catalyst surface after testing, presumably formed during the decomposition of C2H4. Both agglomeration of the active Cu species and blockage by carbon deposits would decrease the availability of active sites and lead to decreased catalytic activity.

Ni-doped γ-Al2O3 as secondary catalyst for bio-syngas purification: influence of Ni loading, catalyst preparation, and gas composition on catalytic activity

In this work, Ni/γ-Al2O3 catalysts were prepared by sol-gel methods with different Ni loadings (10–50 wt.%) and used as secondary catalyst for the steam reforming of toluene. A sample prepared by wet impregnation with 10 wt.% of Ni was also synthesized and compared with the corresponding sol-gel sample. This study was divided in three main parts: the comparison of catalysts prepared by sol-gel process and impregnation, the influence of the gas composition on the catalytic performance of the sol-gel 10 wt.% Ni/γ-Al2O3 catalyst, and the influence of Ni loading on the catalytic activity. When sol-gel and impregnated samples are compared, the impregnated catalyst showed a high initial toluene conversion followed by a consequent and progressive deactivation. Contrarily, the sol-gel catalyst showed a stable catalytic activity and relatively low carbon deposit. Indeed, before the steam reforming of toluene at 650 °C, the sol-gel catalyst was only calcined and no reduction step was realized to reduce nickel oxide. So this sample was reduced during the catalytic test at 650 °C. Moreover, it was observed that if toluene was withdrawn from the syngas mixture during the catalytic test, the sol-gel sample was progressively reoxidized by CO2 and H2O, leading to higher deactivation. As the Ni loading increased, the nickel oxide with strong interactions (NiAl2O4) was progressively joined by nickel oxide with low interactions (NiO/Al2O3) and bulk nickel oxide (NiO). This led to a high initial conversion of toluene but also to a progressive loss of the catalytic activity throughout the catalytic test. It was shown that the sol-gel method developed throughout this work allowed preparing microporous/mesoporous Ni/γ-Al2O3 catalysts with a high dispersion of Ni nanoparticles.

ZnO Nanoclusters Supported on Dealuminated Zeolite β as a Novel Catalyst for Direct Dehydrogenation of Propane to Propylene

AbstractSmall ZnO nanoclusters supported on dealuminated β zeolite were prepared and evaluated for catalyzing direct dehydrogenation of propane to propylene (PDH), exhibiting high catalytic performance. N2 sorption, XRD, TEM, 27Al and 28Si MAS NMR, IR, XRF, DR UV‐vis, XPS, and NH3‐TPD techniques were employed to characterize the physicochemical properties of this novel catalyst system. It is found that the Zn species can be accommodated in the vacant T‐atom sites of dealuminated β zeolite due to the reaction of aqueous zinc acetate solution with silanol groups, and thus, producing massive small ZnO nanoclusters as active phases in PDH. Additionally, dealuminated β zeolite can greatly depress side reactions attributable to the absence of strong acid sites, thereby guaranteeing high catalytic activity, propylene selectivity and stability. As a result, the optimal catalyst of 10 wt% Zn loaded on dealuminated β zeolite exhibits a high initial propane conversion of around 53 % and a superior propylene selectivity of about 93 % at a space velocity of 4000 cm3 gcat−1 h−1, together with the high stability and satisfactory reusability. This study may open a new way to design and synthesize highly active PDH catalysts with high selectivity and stability.

Scalable Processing of Low-Temperature TiO2 Nanoparticles for High-Efficiency Perovskite Solar Cells

Most high-efficiency perovskite solar cells (PSCs) rely on titanium dioxide (TiO 2 ) electron transport layers (ETLs) that are usually processed at high temperature (>450 °C). Consequently, a fully solution-based process of PSCs with TiO 2 ETL on inexpensive flexible polymer substrates is not feasible. Therefore, a scalable low-temperature TiO 2 ETL is developed based on presynthesized crystalline nanoparticle TiO 2 (np-TiO 2 ). The presented synthesis process offers control over the doping, the hydrodynamic diameter, and the solvent of the np-TiO 2 . High initial power conversion efficiency (PCE) of 19.5% (stabilized at 18.2%) of PSC processed on the np-TiO 2 ETL is demonstrated with spin-coated methylammonium lead iodide (CH 3 NH 3 PbI 3 ). Furthermore, it is shown that other perovskite absorber layers that include evaporated CH 3 NH 3 PbI 3 and triple cation perovskite, Cs 0.1 (MA 0.17 FA 0.83 ) 0.9 Pb(I 0.83 Br 0.17 ) 3 , also show very high initial PCE, 14.5% and 19%, respectively. The possibility of doping the np-TiO 2 with niobium (Nb 5+ ) also reduces the resistance of the np-TiO 2 ETL, allowing for thick ETLs that are beneficial for rough substrates. Facile upscaling of the deposition of the np-TiO 2 ETL by inkjet printing, blade coating, and slot-die coating is also demonstrated, having high uniformity, resulting in prototype PSCs with a stable PCE > 15%.

Ni-supported catalysts for ethanol steam reforming: effect of the solvent and metallic precursor in catalyst preparation

Ethanol steam reforming was studied over Ni/MgAl2O4–CeO2 catalysts. The catalysts were prepared using different impregnation media (ethanol or water) and Ni precursors (nitrate or acetate). The use of an alcoholic solution did not affect the specific surface area, but promoted the NiO formation reducible at lower temperature affecting the Ni-support interactions and the Ce3+/Ce4+ initial ratios. All catalysts were highly active in the reforming reaction of ethanol with a high initial conversion of ethanol under more severe conditions than those commonly used in literature. The best catalytic behavior was found over the catalyst prepared from an ethanolic solution of Ni(NO3)2. This sample showed a high Ce3+/Ce4+ ratio, an adequate interaction Ni-support and an average Ni diameter around 28 nm. This catalyst was stable under the reforming conditions used in this work: initial ethanol concentration: 9.4%, reaction temperature: 650 °C, W/F = 49 g min mol_{{{text{C}}_{ 2} {text{H}}_{ 5} {text{OH}}}}^{ - 1} and reaction time: 40 h. The ethanol conversion was almost complete with H2 selectivity around 78%.

Dehydrogenation of n-Butane to Butenes and 1,3-Butadiene over PtAg/Al<sub>2</sub>O<sub>3</sub> Catalysts in the Presence of H<sub>2</sub>

The Al2O3-supported PtAg catalysts were prepared and evaluated for the dehydrogenation of n-butane at 550°C in the presence of H2. The PtAg/Al2O3 catalyst prepared by an impregnation method using the Cl- removing Pt/Al2O3 and AgNO3 showed a higher activity and selectivity to butenes and 1,3-butadiene compared to the Pt/Al2O3 catalyst, but a large amount of coke (about 30 wt% versus the catalyst weight) was formed during the dehydrogenation. The free Ag metal on the prepared catalyst dramatically promoted the coke formation, because the dehydrogenation of 1-butene over the Ag/Al2O3 catalyst produced a large amount of coke. The Cl- addition to the Cl- free Pt/Al2O3 catalyst decreased the coke formation by the reaction of the free Ag particles and Cl to form AgCl which was inactive for the coke formation. The highest initial conversion (50.3%) was obtained with the selectivity to butenes and 1,3-butadiene (butenes = 80.2% and 1,3-butadiene = 5.9%) when the PtAg/Al2O3 catalyst modified with Cl- was used.

Influence of the conditions for reforming HDPE pyrolysis volatiles on the catalyst deactivation by coke

Pyrolysis of high density polyethylene (HDPE) has been carried out in a conical spouted bed reactor (500°C) and the volatiles have been reformed in-line over a Ni commercial catalyst in a fluidized bed reactor. The evolution of reaction indices (conversion, H2 yield and other gaseous product yields) with time on stream has been studied under the following operating conditions: temperature, 600–700°C; space-time, 8.3–20.8gcatmingHDPE−1, and steam/plastic ratio, 3–5. High initial conversion (>94.5%) and H2 yields (>76.7%) are attained under all the operating conditions studied, with HDPE conversion and H2 yield increasing when the three variables are increased, which is explained by the enhancement of the reforming reaction. However, a significant effect of operating conditions on catalyst stability has been observed. Thus, an increase in temperature, space-time and steam/plastic ratio decreases catalyst deactivation as a consequence of a lower rate of coke deposition on the catalyst due to both a lower C5+ coke precursor amount in the reaction medium and a higher gasification rate of the coke deposited.

Preparation of Fe-Doped Carbon Catalyst for Methane Decomposition to Hydrogen

Fe-doped carbon catalysts were prepared from Shenmu sub-bituminous coal with addition of Fe(NO3)3 by KOH activation, and used for catalytic methane decomposition. The effects of Fe amount and carbonization/activation temperature on the structure and catalytic performance of resultant catalysts were investigated. The results showed that ferric nitrate mixed with coal could be directly reduced to Fe metal during the carbonization/activation process without a hydrogen reduction process. Methane conversion over Fe-doped carbon catalysts significantly increases as the amount of added Fe increases. When the amount of Fe added is 30 wt %, the resultant Fe-doped carbon has the highest catalytic activity and methane conversion increases from initial 20% to 58% at the reaction time of 9 h. Low carbonization temperature leads to high initial conversion. The active sites of the Fe-doped carbon catalysts prepared at higher temperature mainly come from metal Fe particles, thus leading to lower initial catalytic activit...

Role of Pt during hydrodeoxygenation of biomass pyrolysis vapors over Pt/HBEA

1.3wt% Pt/HBEA and HBEA were studied as catalysts for the hydrodeoxygenation of pine pyrolysis vapors at 500°C. Both catalysts showed high initial conversion of oxygenated pyrolysis products into aromatic hydrocarbons, while Pt/HBEA showed higher stability in terms of hydrocarbon productivity and deferred breakthrough of oxygenated compounds. Among 1-, 2- and 3-ring aromatic hydrocarbons, Pt/HBEA had a significantly higher selectivity than HBEA towards unalkylated aromatics (e.g., benzene) as compared to the corresponding alkylated aromatics (e.g., toluene and xylene). Additionally, Pt addition to HBEA decreased coke deposition and improved resistance to pore and acid site blockage as determined by TPO, N2 physisorption, and NH3 TPD. The ability of Pt to promote cleavage and hydrogenation of methoxy and methyl groups was observed by increased methane production over Pt/HBEA relative to HBEA. A progressive decrease in the methane production over Pt/HBEA correlated with deactivation in terms of reduced benzene formation, breakthrough of oxygenated products, and increased formation of polynuclear aromatics and their degree of substitution, which indicate coke formation. The increased methane yield and suppressed coke formation with the addition of Pt is attributed to hydrogen spillover, through which hydrogen activated on Pt can subsequently migrate to the HBEA support to reverse the coke-forming hydrogen abstraction reaction.

Highly Active Sb–V–CeO2/TiO2 Catalyst Under Low Sulfur for NH3-SCR at Low Temperature

The Cu based zeolite NH3-SCR catalysts are well-known for after treatment of exhaust gases from light-and heavy-duty diesel engines. However, these catalysts are easily deactivated under the co-presence of H2O and SO2. In the present study, Sb–V–CeO2/TiO2 catalyst showed superior conversion for the abatement of NOx with NH3 under H2O and SO2 condition compared to commercial Cu–SAPO-34 and CuFe–ZSM-5 zeolite catalysts. The physico-chemical properties of fresh and used catalysts were examined by BET surface area, TEM (Transition electron microscopy) with EDS/EDX (Energy dispersive spectrometer/X-ray), XPS (X-ray photoelectron spectroscopy), DRIFTS (in situ diffuse reflectance infrared Fourier transformed spectroscopy) and H2-TPR (temperature programmed reduction). Higher than 95% of initial NOx conversion was obtained over Sb–V–CeO2/TiO2 catalyst at 250 °C under 14% H2O and 50 ppm SO2 conditions. The SO2 on/off test of the CuFe–ZSM-5 and Cu–SAPO-34 catalysts indicated a drastic decrease of NOx conversion when SO2 was turned on. In contrast, Sb–V–CeO2/TiO2 catalyst maintained a high NOx conversion and initial NOx conversion was completely recovered when SO2 was turned off.