Selective catalytic reduction of NOX with ammonia over Mn-Ce-OX/TiO2-carbon nanotube composites

Mn-Ce-O_X catalysts loaded on TiO₂-carbonaceous materials were prepared by sol-gel method. Selective catalytic reduction of NO_X was conducted in a fixed-bed flow-reactor over catalysts coated on aluminum plates. A de-NO_X efficiency of more than 90% was obtained over the Mn-Ce-O_X/TiO₂-carbon nanotubes (CNTs) catalyst between 75 °C and 225 °C under a gas hourly space velocity (GHSV) of ~ 36,000 h⁻¹. This activity improvement is attributed to the increase of the BET surface area, and the occurrence of reaction between adsorbed NO_X and NH₃. Moreover, the de-NO_X efficiency was increased to 99.6% by adding 250 ppm SO₂ between 100 °C and 250 °C.     

Reaction characteristics of two-step methane reforming over a Cu-ferrite/Ce–ZrO2 medium

Methane was reformed over a Cu-ferrite/ZrO₂ medium in a two-step process, consisting of a syn-gas production step and a water-splitting step. In the syn-gas production step, increase in Cu content in the Cu_xFe_3−xO₄/ZrO₂ medium suppressed carbon deposition and enhanced the reaction rate for stoichiometries of x ≤ 0.7. In the water-splitting step, the addition of Cu promoted the gasification of the deposited carbon. Furthermore, the addition of Ce as a binder in the Cu_0.7Fe_2.3O₄/Ce–ZrO₂ medium also improved reactivity in the syn-gas production step and yielded the highest reactivity when the molar ratio of Ce/Zr was 3/1. As a result of the co-addition of Cu and Ce, the Cu_0.7Fe_2.3O₄/Ce–ZrO₂ medium showed high durability, with a constant evolution of the synthesis gas and hydrogen in ten repeated cycles. It is thus expected that the Cu-ferrite/Ce–ZrO₂ medium is favourable for two-step methane reforming.     

Hydrogen production in steam reforming of glycerol by conventional and membrane reactors

The aim of this study is to produce hydrogen through the glycerol steam reforming process. The reaction is carried out in a traditional reactor and an electrolessly plated Pd/Ag alloy membrane reactor, with varying reaction temperature, weight hourly specific velocity (WHSV) and water glycerol molar ratio (WGMR). The non-catalytic test was also employed for comparative purposes. The results show that the reaction is highly depending on temperature, and the maximum glycerol conversion achieved to 96.24% at 800 °C with a hydrogen yield of 5.82 mol-H₂/mol-C₃H₈O₃. It also found that the Pd/Ag membrane can effectively separate hydrogen from the reaction side and subsequently enhance the reaction rate in the membrane reactor. TGA measurements were employed to quantify the amounts of deposited carbon and the results also confirmed that the CeO₂ modified catalyst can improve the carbon resistance as well as activity and stability.     

Improved oxygen permeability of Ce0.8Sm0.2O2−δ–PrBaCo2O5+δ dual-phase membrane by surface-modifying porous layer

A porous PrBaCo₂O_5+δ or Ce_0.8Sm_0.2O_2−δ–50 vol.% PrBaCo₂O_5+δ (SDC–PBCO (5/5)) layer was deposited on dense Ce_0.8Sm_0.2O_2−δ–40 vol.% PrBaCo₂O_5+δ (SDC–PBCO (6/4)) membrane (450 μm) to enhance the oxygen permeability by increasing the surface area contacting with air. The oxygen permeation flux was measured in the temperature range of 825–945 °C. The results revealed that the oxygen permeation performance of Ce_0.8Sm_0.2O_2−δ–PrBaCo₂O_5+δ membranes can be significantly enhanced by coating SDC–PBCO (5/5) porous layer alone on the surface of feed side. The thickness of modification layer has obvious effect on the permeability of surface modified membrane. The modification on the feed side has much better effect than that on the permeate side. At 945 °C, the oxygen permeation flux of dense SDC–PBCO (6/4) membrane modified by porous SDC–PBCO (5/5) layer is 3.56 × 10⁻⁷ mol cm⁻² s⁻¹, 26% higher than that of the unmodified one.     

High specific surface area supports for highly active Rh catalysts: Syngas production from methane at high space velocity

A series of high specific surface area mesoporous supports (CeO₂, CeO₂-Al₂O₃, and Al₂O₃) were synthesized by the surfactant-assisted precipitation method using cetyltrimethylammonium bromide (CTAB) as template. Highly dispersed Rh-based catalysts were prepared by the wetness impregnation technique. The physico-chemical properties of the as-prepared supports and catalysts were investigated by N₂-physisorption, CO-chemisorption, XRD, and H₂-TPR measurements. Catalytic performance was evaluated towards the methane steam reforming (MSR) reaction up to 300 h of time-on-stream varying temperature (700–800 °C), steam-to-carbon (S/C = 2–3), and space velocity (88–200 SL·g_cat^?1·h^?1); turnover frequencies were calculated at each reaction condition. All catalysts exhibited high activity strictly connected with high specific surface area (105–325 m² g^?1) and metal dispersion (34.3–84.0%). Significant enhanced stability was observed for Al₂O₃-containing catalysts towards the MSR reaction at high space velocity.