Catalytic Sorbent Research Articles

Ru/K2CO3–MgO catalytic sorbent for integrated CO2 capture and methanation at low temperatures

In this study, we have developed a Ru/K2CO3–MgO (Ru/KMg) catal-sorbent for integrated CO2 capture and methanation (ICCM) at low temperatures. The Ru primarily existed as a K2RuO3 phase, which was not observed after reduction at 400 °C. In addition, the crystallite size of Ru0 is smaller than that of Ru/MgO because Ru species as K2RuO3 phase, instead of RuO2, is dispersed well throughout the MgO support material. Here, the CO2 capture and regeneration properties of Ru/KMg catal-sorbents after carbonation at different temperatures (60, 120, 150, and 320 °C) were studied under N2 or H2 conditions, respectively. The optimal carbonation temperature was 150 °C when considering 100% CO2 conversion to CH4. 20 consecutive cycles of ICCM were conducted at 150 °C for carbonation (10 vol% CO2 and 10 vol% H2O) and 320 °C for methanation (90 vol% H2). The results showed stable CH4 productivities of 1.07–1.19 mmol CH4/g with 100% CH4 selectivity and 96.2%–101.3% CH4 yield.

Tailoring lattice oxygen triggered NiO/Ca9Co12O28 catalysts for sorption-enhanced renewable hydrogen production

Sorption-enhanced steam reforming of ethanol shows potential of supplying high-quality hydrogen with in situ CO2 capture, but suffers from sorbent deactivation. This paper describers the design of functionalized xNiO/Ca9Co12O28 materials, whose phases can be segregated once triggered by the lattice oxygen consumption via NiO/Ca9Co12O28-O2-→Ni-Co+CaO, thus acting as the catalytic sorbent. Their superiorities are demonstrated in: (i) low-temperature activation via lattice oxygen induction; (ii) recyclability via lattice oxygen replenishment; iii) high-quality hydrogen actuation via in situ CO2 adsorption. Hydrogen concentration of 95.56 vol% and near-complete ethanol conversion can be achieved. Moreover, stability across 50 repeated cycles without obvious reduction in catalytic reforming and CO2 adsorption is demonstrated. In situ XRD studies demonstrate the formation of the Ni-Co alloy and the reorganization of the catalytic sorbent. The adsorption energies of ethanol on the surface of Ni(111), Co(111), and Ni-Co(111) were studied by DFT calculations, reaffirming the higher catalytic activity of Ni-Co alloys.

Simultaneous enhancement of the H2 yield and HCl removal efficiency from pyrolysis of infusion tube under novel mayenite-based mesoporous catalytic sorbents

The promising pathway of turning energy-containing waste into renewable and sustainable energy has effectively alleviated the excessive dependence on traditional fossil energy. In this study, two different mesoporous catalytic sorbents i.e. Ca12Al14O33@mCaO and Ca12Al14O33@mCu/CaO were synthesized by sol-gel method and their promotion effect on H2 yield and simultaneous removal of harmful HCl gas during the pyrolysis of infusion tube (IT) was explored. Results indicated that the abundant internal mesoporous structure of Ca12Al14O33@mCaO made the specific surface area and pore volume of 10.26 m2/g and 0.0541 cm3/g, respectively, which provided a larger contact area for the catalytic reaction. Maximum H2 yield of 59.01 μmol g−1·min−1 was obtained under the optimal conditions while maximum HCl removal efficiency was as high as 93.36%. Compared to that of the Ca12Al14O33@mCaO, higher H2 yield (73.23 μmol g−1·min−1) recovered over Ca12Al14O33@mCu/CaO and the HCl removal efficiency also remained stable at about 90%. Both synthesized mesoporous catalytic sorbents showed an increase in H2 yield and a good removal effect on HCl during the pyrolysis process of IT.

H2S catalytic removal at low temperature over Cu- and Mg- activated carbon honeycombs

A series of monometallic and bimetallic Cu/Mg oxide-based structured catalytic sorbents were synthesized by impregnation of extruded activated carbon honeycombs and tested for the purification of simulated biogas from H2S at room temperature. Dynamic H2S (100ppmv) removal tests were run at short contact time under moist conditions in the presence of O2 to compare sulfur capture capacities and to investigate kinetic aspects of the oxidation reactions involved in the mechanism at varying the composition of the active phase. Fresh, exhausted and thermally regenerated honeycomb catalytic sorbents were characterized by N2-adsorption, PSD, XPS, TG-MS to shed light on the specific nature of S-species formed upon catalytic oxidation, the maximum capacity and the efficacy of a simple thermal regeneration treatment at 600 °C. Under moist conditions, the surface chemistry resulted dominated by the basic nature of MgO, and bimetallic CuMg catalytic sorbents show fast H2S removal rates and large S-capacity coupled to easy and complete regenerability.

Integrated capture and conversion of CO2 into methane using NaNO3/MgO + Ru/Al2O3 as a catalytic sorbent

Catalytic sorbents are prepared by physically mixing NaNO3/MgO sorbents and Ru/Al2O3 catalysts and the ability of the composite materials to capture and convert CO2 to methane in a combined capture and conversion cycle is evaluated. The catalytic sorbents are prepared using two preparation methods: i) packing the two components in two separate beds and ii) packing as a single bed after mixing and pelletization of the two components. The catalytic sorbents prepared as two separate beds are more effective, showing an elevated CO2 sorption capacity of 3.24 mmol CO2/g and methane production capacity of 2.21 mmol CH4/g. Mixing and pelletizing the two components together is found to significantly decrease the CO2 sorption capacity of the catalytic sorbent. CO2 methanation reaction pathways are also investigated over 1% Ru/Al2O3 catalysts and 5% NaNO3/1% Ru/Al2O3 catalysts via combination of kinetic studies elucidating the apparent CO2 and H2 reaction orders combined with insitu FTIR measurements. For 1% Ru/Al2O3, it is hypothesized that carbonyl species are reaction intermediates and formate species are spectator species, while for the 5% NaNO3/1%Ru/Al2O3 catalyst, both carbonyl species and formate species are potentially reaction intermediates for the methanation reaction. Hypothetical reaction mechanisms and rate laws are proposed for the two types of catalysts as well.

CO2 sorption-enhanced steam reforming of phenol using Ni–M/CaO–Ca12Al14O33 (M = Cu, Co, and Ce) as catalytic sorbents

Abstract In this study, two kinds of Ni/CaO–Ca12Al14O33 catalytic sorbents were synthesized by wet impregnation using different CaO–Ca12Al14O33 as supports, which were prepared via calcination hydration (CH) and sol–gel/loading (SL) methods. Sorption-enhanced steam reforming (SESR) for hydrogen production was investigated using phenol as a tar model compound in a laboratory-scale fixed bed reactor. The Ni/CaO–Ca12Al14O33(CH) exhibited a higher hydrogen production activity compared to Ni/CaO–Ca12Al14O33(SL). The optimum operation condition for SESR process was obtained as temperature of 650 °C with S/C ratio of 3.0. Under this condition, the maximum H2 concentrations of 69.75% and 67.68% were achieved for Ni/CaO–Ca12Al14O33(CH) and Ni/CaO–Ca12Al14O33(SL), respectively. The corresponding H2 yields were 1.61 L/g and 1.45 L/g. However, a rapid deactivation of the Ni/CaO–Ca12Al14O33 catalytic sorbents occurred during the cyclic tests. Thus, bimetallic catalytic sorbents, Ni–M/CaO–Ca12Al14O33 (M = Cu, Co, and Ce), were developed by introducing the guest metal oxides. Among the three bimetallic catalytic sorbents, Ni–Co/CaO–Ca12Al14O33(CH) had the greatest potential for hydrogen production due to the synergistic catalytic effect of Co and Ni. The maximum H2 concentration of 82.23% and the maximum H2 yield of 2.31 L/g at 650 °C with S/C = 3.0 were observed for Ni–Co/CaO–Ca12Al14O33(CH). During the cyclic tests, the slight decrease in the H2 yield of Ni–Co/CaO–Ca12Al14O33(CH) was attributed to the decrease in the CO2 sorption capacity. The Ni–Ce/CaO–Ca12Al14O33(CH) showed a stable CO2 sorption/desorption ability, but the H2 yield decreased sharply due to the sintering of Ni particles and carbon deposition. Although the CO2 sorption capacity of Ni–Cu/CaO–Ca12Al14O33(CH) was well below the other two, it exhibited excellent stability. The results suggest that Ni–Co/CaO–Ca12Al14O33 and Ni–Cu/CaO–Ca12Al14O33 catalytic sorbents have great potential for the steam reforming of tar.

Regenerable Ce–Mn/TiO2 Catalytic Sorbent for Mercury Removal with High Resistance to SO2

Mn/TiO2 (MT), Ce/TiO2 (CT), and Ce–Mn/TiO2 (CMT) for mercury removal were prepared by an impregnation method, and mercury adsorption tests were conducted in a fixed-bed reactor. Regeneration experi...

Vanadium silicate (EVS)-supported silver nanoparticles: A novel catalytic sorbent for elemental mercury removal from flue gas.

Vanadium silicate (EVS) is a vanadium-substituted form of titanosilicate that has a high potential for use as a sorbent for mercury removal. In the present study, EVS with supported silver nanoparticles (EVS-Ag100) as the catalytic sorbent was synthesized for elemental mercury (Hg°) capture. The physical and chemical properties of the sorbents were investigated. The raw EVS exhibited a poor Hg° capture capacity (7.7 μg g-1), because most of the vanadium species in the structure of EVS were V4+. The loading of the silver could significantly enhance the Hg° capture capacity (63.4 μg g-1). EVS-Ag100 exhibited a superior Hg° capture performance at temperatures of approximately 150 °C. Silver nanoparticles that formed on the EVS were the active sites. In addition, the vanadium species of EVS-Ag100 exhibited higher Hg° oxidation activity than those in the framework of raw EVS. The XPS results revealed the activation of the vanadium species by the silver nanoparticles. After the capture of Hg° in the presence of O2, more V5+ was observed on the surface of EVS-Ag100. Exposure of EVS-Ag100 to a continuous simulated flue gas at 150 °C with a gas hourly space velocity of 220,000 h-1 led to Hg° removal efficiency of >96% in a 1 h test.

Inherent thermal regeneration performance of different MnO2 crystallographic structures for mercury removal.

Manganese oxides with different crystallographic structures were investigated for gas-phase elemental mercury removal. The inherent thermal regeneration performance and mechanism of α- and γ-MnO2 were studied. The manganese dioxides were found to possess a mercury removal efficiency of higher than 96% even after 120 min mercury exposure except for β-MnO2 which removed much less mercury than Mn2O3. The α-MnO2 was found to have a higher recyclability of mercury capture and better durability for regeneration than γ-MnO2. During the first 1 h of exposure, α-MnO2 showed an excellent mercury capacity of 128 μg/g over 5 regeneration cycles. While for γ-MnO2, the mercury capacity of the fifth cycle was reduced to 68.74 μg/g, which is much lower than 131.42 μg/g for the first cycle. The microstructure of α-MnO2 was maintained throughout regeneration cycles due to its capability to retain lattice oxygen. In comparison, γ-MnO2 experienced reconstruction and phase transformation induced by oxygen vacancies due to lattice oxygen loss during regeneration process, leading to a degradation in mercury capture. The α-MnO2 oriented composite was found to be better developed into a regenerable catalytic sorbent for mercury removal from flue gases of coal-fired power plants.

Elemental mercury removal over a novel starch-modified MnOx/bentonite composite

To improve the activity of elemental mercury (Hg0) removal over the bentonite supported MnOx material (MnOx/bentonite), a novel starch-modified MnOx/bentonite composite (MnOx/starch-bentonite) was synthesized for Hg0 capture. The Hg0 removal activity tested under the atmosphere of pure N2 and in the presence of O2 showed that the MnOx/starch-bentonite exhibited better activity and stability than MnOx/bentonite. It was evident that the Hg0 removal efficiency over the novel catalytic sorbent (BS10M2) only declined by 16.9%, while that over MnOx/bentonite fell by 68.7% after a 5 h test under the atmosphere of N2 + 6%O2 at 120 °C. The starch modification decreased the surface area but enhanced the surface activity of bentonite, and more activate sites were generated on the surface of bentonite after being impregnated with potassium permanganate (KMnO4) solution. The improved Hg0 removal performance was probably due to the generation of more Mn4+ and the newly introduced ester groups formed by the partial oxidation reaction between starch and KMnO4 on the support, which played essential roles in mercury catalytic oxidation and adsorption. The MnOx were generated in two ways: KMnO4 decomposition in a neutral solution condition and KMnO4 reduction by the starch with hydroxyl groups.

Catalytic processing of non-condensable pyrolysis gas from plastics: Effects of calcium supports on nickel-catalyzed decomposition of hydrocarbons and HCl sorption

Non-condensable pyrolysis gas is a suitable source of hydrocarbons for energy applications. The purpose of this study was to develop a catalytic process for selective decomposition of unsaturated hydrocarbons in the pyrolysis gas as these species compromise the operation of gas engines, gas turbines and fuel cells. The effect of different calcium supports, namely CaCO3, Ca(OH)2, CaO and their mixtures, on the performance of Ni-based catalytic sorbents during the decomposition of hydrocarbons and HCl sorption from non-condensable pyrolysis gas of mixed plastics was investigated. The plastic mixture containing low density polyethylene (40%), polypropylene (40%), polystyrene (10%) and polyvinyl chloride (10%) was initially pyrolyzed at 600 °C producing condensable oils and non-condensable gases. The non-condensable gases were further treated in a subsequent reactor at 700 °C in the presence of catalytic sorbents. All catalytic sorbents were effective for HCl sorption, decreasing the HCl concentration in the gas stream below detectable levels. However, the choice of calcium support had a substantial effect on the catalytic decomposition of hydrocarbons and the properties of produced carbon deposits. CaCO3, Ca(OH)2 and their mixture at 1:1 ratio by mass loaded with Ni showed higher catalytic activity towards the decomposition of hydrocarbons compared to CaO and a mixture containing CaO, CaCO3 and Ca(OH)2 at 1:1:1 ratio by mass. Furthermore, carbon deposits produced on the surface of Ni supported on CaCO3, Ca(OH)2 and their mixture contained multi-walled carbon nanotubes, whereas carbon deposits produced on Ni supported on CaO and the mixture containing CaO had non-filamentous morphology. The observed results can be attributed to the low BET specific surface areas and pore volumes of CaO-containing catalytic sorbents which could limit the dispersion of Ni resulting in low catalytic activity.

Waste into Fuel—Catalyst and Process Development for MSW Valorisation

The present review paper highlights recent progress in the processing of potential municipal solid waste (MSW) derived fuels. These wastes come from the sieved fraction (∅ < 40 mm), which, after sorting, can differ in biodegradable fraction content ranging from 5–60%. The fuels obtained from these wastes possess volumetric energy densities in the range of 15.6–26.8 MJL−1 and are composed mainly of methanol, ethanol, butanol, and carboxylic acids. Although these waste streams are a cheap and abundant source (and decrease the fraction going to landfills), syngas produced from MSW contains various impurities such as organic compounds, nitrogen oxides, sulfur, and chlorine components. These limit its use for advanced electricity generation especially for heat and power generation units based on high temperature fuel cells such as solid oxide fuel cells (SOFC) or molten carbonate fuel cells (MCFC). In this paper, we review recent research developments in the continuous MSW processing for syngas production specifically concentrating on dry reforming and the catalytic sorbent effects on effluent and process efficiency. A particular emphasis is placed on waste derived biofuels, which are currently a primary candidate for a sustainable biofuel of tomorrow, catalysts/catalytic sorbents with decreased amounts of noble metals, their long term activity, and poison resistance, and novel nano-sorbent materials. In this review, future prospects for waste to fuels or chemicals and the needed research to further process technologies are discussed.

Improvement of the Catalytic Oxidation of Dissolved Hydrogen with Palladium-Coated Sorbents

New improved process for the catalytic oxidation of dissolved hydrogen with the use of palladiumcoated sorbents was suggested, described, and performed. To implement the suggestion of the authors in accordance with the scheme of the experimental setup, dissolved hydrogen formed as a result of radiolysis of water is removed from a water heat-carrying agent by the method of catalytic oxidation on the surface of a palladium-coated sorbent when the heat carrier is filtered through a mixed-type ion-exchange filter to which a catalytic sorbent is added. The decrease in the concentration of hydrogen dissolved in the heat-carrying agent rules out its evolution into the gas phase in amounts forming explosive mixtures.

Upgrading of non-condensable pyrolysis gas from mixed plastics through catalytic decomposition and dechlorination

The non-condensable pyrolysis gas from plastic pyrolysis is a suitable fuel and precursor for chemical synthesis. Depending on downstream applications, the selective removal of unsaturated hydrocarbons and HCl released from polyvinyl chloride (PVC) is required. This study investigated the selective decomposition of unsaturated hydrocarbons with simultaneous dechlorination of non-condensable pyrolysis gas using a catalytic sorbent containing 5% NiO loaded on CaCO3 support (Ni-Ca) and pristine CaCO3 (Ca) at different temperatures, doses of catalytic sorbent and HCl contents. As a result, Ca removed 98.8% of HCl and decomposed 89% of alkynes and 23% of dienes at 700°C. When applying Ni-Ca, the HCl removal was above 99% at all studied temperatures, while 90% decomposition of alkenes, dienes and alkynes was achieved, depending on temperature, Ni-Ca dose and HCl content. The higher HCl content in gas (43mg against 13mg) negatively influenced the catalytic activity of Ni-Ca, while increasing the selectivity towards the decomposition of alkenes, dienes and alkynes compared to alkanes. At 700°C, 99.6% removal of unsaturated hydrocarbons by Ni-Ca was attained at only 10.1% conversion of alkanes. Thus, depending on the applied catalytic sorbent, either selective decomposition of alkynes and dienes (over Ca) or a mixture of unsaturated hydrocarbons (over Ni-Ca) was achieved with the simultaneous HCl removal from non-condensable pyrolysis gas.

Magnetically responsive catalytic sorbent for removal of Hg0 and NO

A novel class of magnetically responsive catalytic sorbents are proposed and synthesized with a potential application to simultaneous removal of Hg0 and NO at low temperature from the flue gases of coal-fired power plants. The catalytic sorbent consists of magnetite (Fe3O4), molecular sieve (HZSM-5), supported silver nanoparticles and catalytically reactive component of V2O5. Each of these materials provides a unique function for the purpose of capturing mercury, removing NO, and separation from fly ash. After separation from the fly ash, the spent sorbent can be regenerated and reused, leaving an uncontaminated fly ash product. The successful synthesis as designed was confirmed and properties of the catalytic sorbent were characterized by several methods. The synthesized catalytic sorbent was able to completely capture Hg0 at 150°C with a capture capacity as high as 32.4μg·g−1, while achieving 84% removal of NO at 150°C. Even at a relatively high space velocity, the catalytic sorbent achieved 97% Hg0 and 80% NO removal simultaneously, while maintaining a good stability after repetitive regeneration and recycle. The magnetically responsive catalytic composite was shown to be a promising candidate for multi-pollutant emission control from coal-fired power plants.

Evaluation of filter media performance: Correlation between high and low challenge concentration tests for toluene and formaldehyde (ASHRAE RP-1557)

To guide the selection of gas phase filtration media in the air cleaning devices, it is important to understand and estimate the media performance under usage concentrations. Filters for improving indoor air quality are typically subject to low volatile organic compounds (VOCs) concentration levels (e.g., ∼50 ppb), while the current standard tests per ASHRAE 145.1 (ANSI/ASHRAE 2008). are performed at relatively high challenge concentrations (∼1–100 ppm level). The primary objective of this study was to determine if media that perform well at the high concentration test condition would also perform well under the low concentration. The secondary objective was to investigate if and how existing models of filtration by media bed can be applied to extrapolate the results from the high concentration tests to the low concentration condition. Experiments and simulations were carried out at both high concentrations (100 ppm for toluene and 1 ppm for formaldehyde) and low concentrations (0.05 ppm for toluene and formaldehyde) for six selected filtration media. The results show that (1) the high concentration test data were able to differentiate the relative performance among the media at the low concentration properly, confirming the validity of using ASHRAE 145.1 (ANSI/ASHRAE 2008) for relative performance comparison; (2) significant initial breakthrough observed at high concentration tests of large pellet media was not present at the low concentration tests, indicating the dependency of the adsorption capability of the sorbent media on the concentration level as well as the possible “by-pass” effects (i.e., not all the VOC molecules in the air stream had the same chance to contact with the sorbent media); and (3) existing models need to be improved by incorporating the concentration dependency of the partition coefficient and the by-pass effect in order to predict the breakthrough curve at low concentrations properly. Such an improved model was proposed, evaluated with the measured data, and was found to be promising for physical sorbent, but requires further development for chemical, catalytic sorbent and large pellet sorbent. The study provides previously unavailable experimental data and new insight into the behavior of the filtration media for volatile organic compounds as well as evidence in support of the application of ASHRAE Standard 145.1 (ANSI/ASHRAE 2008) for media performance evaluation.

The properties of carbon-carbonic condensate synthesized in the plasma arc

Physical and chemical properties of carbon-carbonic condensate synthesized by the plasma-arc technology have been studied experimentally. X-ray phase analysis has been performed, the isotherms of physical adsorption and sorption ability of the synthesized material have been measured. It has been concluded that this material offers promise as a carrier of catalytic nanoparticles and effective sorbent.

Tail-Gas Cleanup by Simultaneous SO2and H2S Removal

Tail-gas streams from refinery processes such as Claus units often contain and emit SO2 and H2S at levels exceeding permissible emission limits, which are currently set at 10 ppm H2S and 250 ppm SO2 (U.S.). Gas compositions vary widely depending on the application, with some containing high levels of SO2, H2S, and moisture. This publication describes the simultaneous removal of these sulfur-containing contaminants utilizing a regenerable catalytic sorbent. A simplified process with the potential to reduce a four-stage process to a two-stage process is presented. The new process would compete with currently established technologies such as amine scrubbers or Cansolv units (property of Cansolv Technologies Inc., Montreal, Quebec, Canada H2M 2N9).

04/02680 Low cost catalytic sorbents for NO x reduction.3. NO reduction tests using NH3 as reducing agent : Lázaro, M. J. et al. Fuel, 2004, 83, (7–8), 875–884

04/02680 Low cost catalytic sorbents for NO x reduction.3. NO reduction tests using NH3 as reducing agent : Lázaro, M. J. et al. Fuel, 2004, 83, (7–8), 875–884

04/00532 Low cost catalytic sorbents for NO x reduction. 2. Tests with no reduction reactives : Lázaro, M. J. et al. Fuel, 2003, 82, (7), 771–782..

04/00532 Low cost catalytic sorbents for NO x reduction. 2. Tests with no reduction reactives : Lázaro, M. J. et al. Fuel, 2003, 82, (7), 771–782..