Sequential Incipient Wetness Impregnation Research Articles

Synthesis and evaluation of novel Cu-based adsorbent-containing catalysts for CO2 hydrogenation to methanol and value-added products

In this work, sequential incipient wetness impregnation method was used to synthesize Cu/Al2O3, Cu/Na2O/Al2O3 and Cu/CaO/Al2O3 catalysts in different compositions for CO2 conversion to value-added products. Synthesized catalysts were characterized using various analytical techniques and their performances for CO2 catalytic conversion were tested in a high-pressure packed bed reactor under reaction conditions of P = 60 bars, T = 300 °C, and H2/CO2 = 3. The obtained results revealed that the type of adsorbent had a significant impact on CO2 conversion, with CaO-containing catalyst being more efficient for methanol selectivity. Increased Cu content from 10 wt% to 30 wt% with fixed CaO content of 10 wt% resulted in a small increase in CO2 conversion where the highest CO2 conversion of 16.44% and the highest methanol selectivity (17.75%) were obtained for catalyst containing 20 wt% of copper. The best performing catalyst was further promoted using 0.5 wt% Rh promoter which improved both methanol selectivity and space time yield to 23.2% and 0.08 gMeOHgcat−1h−1, respectively. The comparative high performance of the Rh-promoted catalyst was attributed to smaller metal oxide particle size with uniform dispersion, presence of effective hydrogen spill over, moderate basic sites, surface defects and presence of induced copper species.

Carbon dioxide hydrogenation to value-added products using Cu-based catalytic materials

In this work, we report on the synthesis and evaluation of catalytic materials composed of copper/calcium oxide/alumina (Cu/CaO/Al2O3) for carbon dioxide conversion to value-added products. Catalytic materials were synthesized using sequential incipient wetness impregnation method. Synthesized materials with different compositions of copper and adsorbent were tested in a high-pressure packed bed reactor under a pressure P =60 bars, temperature T=300 °C, and hydrogen to carbon dioxide ratio (H2/CO2 = 3) to determine their performances and catalytic activities. The results of the activity revealed that CaO-based catalysts were very active in converting CO2 to methanol and carbon monoxide. Catalyst containing 30%Cu10%CaO achieved the highest CO2 conversion of 16.5% and a maximum methanol selectivity of 17.8%, while the lowest selectivity towards carbon monoxide (CO) were obtained using 20%Cu-containing catalyst. Reducing CaO content from 10wt% to 5wt% boosted the CO2 conversion to 18% with higher selectivity towards CO compared to the catalyst containing 10%CaO.

Synthesis and evaluation of novel and efficient Ni-based dual functional materials (DFMs) for integrated CO2 capture and hydrogenation

We report on the synthesis and evaluation of novel, highly active and stable bimetallic DFMs for simultaneous CO2 adsorption and subsequent hydrogenation to value added products. The DFMs contain various combinations of Ni (5–15 wt%) and Cu (5–15 wt%) with Na2O (5–15 wt%) as adsorbent supported on alumina (γ-Al2O3). The DFMs were synthesized via sequential incipient wetness impregnation method and were thoroughly characterized by combination of various surface sensitive and bulk sensitive analytical tools such as XRD, XPS, BET surface area, HR-TEM and H2-TPR. The DFMs were evaluated for CO2 capture and subsequent hydrogenation in a fixed-bed quartz tubular reactor connected with an online gas analyzer. The results demonstrated that at an operating temperature of 320℃, the DFM with a composition of 10 wt%Ni5wt%Cu/10 wt%Na2O.Al2O3 resulted in exceptionally high CO2 adsorption (310.84 μmol/g) and subsequent hydrogenation to methane (249.2 μmol CH4/gDFM). The XPS analysis revealed that this DFM contains comparatively larger percentage of highly ionized and/or induced Ni2+ as well as Cu+1 species. The results of H2-TPR also clearly indicated improvement in its reducibility. Moreover, the TEM analysis results revealed the presence of well-dispersed and smaller metal oxide particles in the bimetallic 10 wt%Ni5wt%Cu/10 wt%Na2O.Al2O3 DFM. In this regards, the exceptional high performance of the 10 wt%Ni5wt%Cu/10 wt%Na2O.Al2O3 DFM was attributed to the synergistic effects of the bimetallic combination of Ni with Cu resulting in enhanced physicochemical properties and thus demonstrated exceptionally higher performance.

Sustainable syngas production by oxy-steam reforming of simulated biogas over NiCe/MgAl hydrotalcite-derived catalysts: Role of support preparation methods on activity

Herein, a series of hydrotalcite-derived MgAl supports were prepared by co-precipitation and hydrothermal methods. NiCe/MgAl catalysts were prepared by loading Ni (10 wt%) and Ce (2.5 wt%) on supports using sequential incipient wetness impregnation and tested in oxy-steam reforming of simulated biogas to produce syngas. N2-physisorption, XRD, XPS, SEM, TEM, ICP-OES, TGA, and Raman were used for catalyst characterization. Reactivity was evaluated at 600 °C, 700 °C, and 800 °C with a constant GHSV (45,000 ml gcat−1 h−1) and feed ratio (CH4/CO2/O2/H2O = 1/0.67/0.1/0.3). The results demonstrate that increasing the co-precipitation aging temperature and the hydrothermal reaction temperature affected the surface area, pore volume, and Ni crystallite size. However, no significant change in reactivity was observed. The NiCe/MgAl catalyst with co-precipitation aging temperature of 140 °C (NCMA140-Co) exhibited lower carbon deposition probably due to higher Ce4+ concentration. Therefore, NCMA140-Co provided high stability and conversions of CH4 (94%) and CO2 (82%) with H2/CO ratio (1.6) at 800 °C without carbon deposition.

Greenhouse gas mitigation and hydrogen generation via enhanced ethylene glycol dry reforming on La-promoted Co/Al2O3 catalyst

The first investigation of La-promoted Co/Al2O3 catalysts in Ethylene Glycol-CO2 conversion (EGCC) for syngas (H2 + CO) production was conducted in this work. Co/Al2O3 catalysts modified with different La promoter loadings (1, 3, and 5%) were generated through sequential incipient wetness impregnation technique and employed for EGCC. The physicochemical attributes of the generated catalysts were examined via Brunauer-Emmett-Teller (BET), H2 temperature-programmed reduction (H2-TPR), X-ray diffraction (XRD), Raman, and temperature-programmed oxidation (TPO). 3%La-promoted catalyst owned the largest specific surface area, smallest Co crystallite size of 9.8 nm, and lowest reduction temperature among the promoted catalysts. These excellent properties resulted in the highest catalytic performance on the 3%La-promoted catalyst (i.e., C2H6O2 conversion = 77.6 %, CO2 conversion = 43.1 %, H2 yield = 75.3 %, and CO yield = 76.8 %). The significant reduction in carbon deposition of the 3%La-promoted catalyst was due to the La capability in eliminating deposited carbon via the formation of intermediate lanthanum dioxycarbonate, La2O2CO3.

Coke-resistant Y2O3-promoted cobalt supported on mesoporous alumina for enhanced hydrogen production

In this work, the δ%Y–10%Co/MA (δ = 0, 1, 2, 3, and 5 wt%) catalysts synthesised by sequential incipient wetness impregnation were characterised and evaluated in CH4 dry reforming. Superior catalytic performances were shown by 3 wt% Y2O3 loading (CH4 conversion = 85.8%, and CO2 conversion = 90.5%), followed by 2 wt% > 5 wt% > 1 wt% > 0 wt% Y2O3 loading. This result was attributed to the favorable catalytic properties of 3 wt%Y–10%Co/MA including small Co particle size, high Co dispersion, high amount of atomic ratio (Co/Al), and high number of lattice oxygen vacancies. The excess Y2O3 addition (>3 wt%) led to inevitably blocked Co active sites and resulted in decreasing catalytic performance. The 3 wt% Y2O3 promoter loading recorded the lowest carbon deposited (7.0%) due to the highest oxygen vacancies (78.1%) compared to 1, 2 and 5 wt% Y2O3.

Oxidation of Carbon Monoxide on Co−Ce‐Modified ZSM‐5 Zeolites: Impact of Mixed Oxo‐Species

AbstractThe main idea of the present work is the creation of new types of redox active sites by using zeolite as a matrix. Structure and catalytic activity in CO oxidation were studied for catalysts based on Co−Ce‐modified ZSM‐5 synthesized by sequential incipient wetness impregnation. Synergy of action of the two additives is observed. The most active is the catalyst with the ratio Co : Ce=3 : 1. According to TEM, XPS, UV‐vis‐DRS, DRIFTS and in situ CO‐reduction studies, the interaction of metals occurs in the channels of the zeolite with the formation of previously unknown joint structures in which CoIII and CeIII are stabilized. Apparently, these structures are represented by mixed Co−Ce oxo‐cations [CoxCeOy]n+. A new absorption band at 2179 cm−1 appearing in the DRIFT spectra of adsorbed CO is associated with mixed species. The catalytic activity in the oxidation of CO correlates with amount of these structures.

Ethanol CO2 reforming on La2O3 and CeO2-promoted Cu/Al2O3 catalysts for enhanced hydrogen production

3%Ce- and 3%La-promoted 10%Cu/Al2O3 catalysts were synthesized via a sequential incipient wetness impregnation approach and implemented for ethanol CO2 reforming (ECR) at 948–1023 K and stoichiometric feed ratio. CeO2 and La2O3 promoters reduced CuO crystallite size from 32.4 to 27.4 nm due to diluting impact and enhanced the degree of reduction of CuO → Cu0. Irrespective of reaction temperature, 3%La–10%Cu/Al2O3 exhibited the highest reactant conversions, H2 and CO yields followed by 3%Ce–10%Cu/Al2O3 and 10%Cu/Al2O3. The greatest C2H5OH and CO2 conversions of 87.6% and 55.1%, respectively were observed on 3%La–10%Cu/Al2O3 at 1023 K whereas for all catalysts, H2/CO ratios varying from 1.46 to 1.91 were preferred as feedstocks for Fischer-Tropsch synthesis. Activation energy for C2H5OH consumption was also reduced with promoter addition from 53.29 to 47.05 kJ mol−1. The thorough CuO → Cu0 reduction by H2 activation was evident and the Cu0 active phase was resistant to re-oxidation during ECR for all samples. Promoters addition reduced considerably the total carbon deposition from 40.04% to 27.55% and greatly suppressed non-active graphite formation from 26.94% to 4.20% because of their basic character and cycling redox enhancement.

Effect of Co incorporation and support selection on deoxygenation selectivity and stability of (Co)Mo catalysts in anisole HDO

A series of supported Co modified Mo catalysts was prepared by varying the Co/Mo ratio in the range from 0 to 1 while maintaining the Mo loading at ca. 10 wt%. A sequential incipient wetness impregnation method, with Mo being introduced first, using aqueous solutions of the corresponding precursor salts was employed during the synthesis procedure. Three supports, i.e., Al2O3, ZrO2, and TiO2 differing in textural and acidic properties were investigated. Material physicochemical characteristics were evaluated through ICP-OES, N2-sorption, XRD, H2-TPR, NH3-TPD, O2-TPO, STEM-EDX and XPS techniques. The anisole HDO performance of these CoMo catalysts was evaluated at gas phase conditions in a fixed bed tubular reactor in plug flow regime. The catalysts performance is correlated with properties such as reducibility, acidity, and metal-support interactions. Cobalt addition enhanced the total HDO selectivity by 45% as compared to Mo catalysts. Alumina catalysts displayed higher initial activity (Xanisole≈97%) relative to titania and zirconia supported variants (Xanisole <40%) at identical operating conditions. Titania supported catalysts exhibited rather higher stability compared to zirconia and alumina catalysts over 50 h time on stream (TOS), while zirconia catalysts displayed the highest HDO selectivity (up to 86%). Characterization studies of pre and post-reaction catalysts indicate Mo5+ to be the main active phase while over-reduction to lower Mo states (Mo4+ and Mo3+) as well as carbon deposition are identified as the cause for catalyst activity decrease with TOS.

Methane bi-reforming over boron-doped Ni/SBA-15 catalyst: Longevity evaluation

A highly active and stable boron-promoted catalyst was successfully prepared by using the sequential incipient wetness impregnation technique and examined for methane bi-reforming reaction. The initial investigation found that the NiO and B2O3 particles were dispersed on the outer surface of the high surface area SBA-15 support. In addition, the catalytic activity was increased linearly with the tested reaction temperature due to the endothermic nature of the reaction. In fact, the catalyst achieved the CH4 conversion and H2/CO molar ratio of approximately 67.3% and 2.7, respectively at 1073 K. The resulting product ratio is highly suitable for downstream Fischer-Tropsch (FT) synthesis. The B-promoted catalyst showed the lowest degree of catalyst deactivation (4%) at 1023 K. Additionally, the XPS measurements unveiled that the boron facilitates the adsorption of CO2 by donating electrons to the neighbouring Ni cluster and thus improved its catalytic performance. Furthermore, Raman and XRD analysis revealed that the boron promotion on 10%Ni/SBA-15 could prevent the reoxidation and deposition of carbonaceous species.

K-Promoted Pt-Hydrotalcite Catalyst for Production of H2 by Aqueous Phase Reforming of Glycerol

The effect of potassium on the Pt supported hydrotalcite catalyst (Pt-KHT) was investigated in the aqueous phase reforming (APR) of glycerol for the efficient production of H2. Pt-KHT was prepared by the sequential incipient wetness impregnation method where impregnation of K was carried out first followed by incorporation of Pt. The catalyst was characterized by XRD, SEM, HRTEM, XPS, FTIR, TPR, and TPD. The TEM images of the catalyst showed highly dispersed Pt-species supported on hydrotalcite with needle-like structure. The addition of potassium (K+) increases the basicity of the Pt-KHT catalyst and enhances the production of hydrogen through APR of glycerol. The gaseous product formed over Pt-KHT at 250 °C was 99.4% which is higher than that obtained of Pt-HT catalyst, and an H2 selectivity of 67.4% was achieved over Pt-KHT after 3 h of reaction.

Combined steam and CO2 reforming of methane for syngas production over carbon-resistant boron-promoted Ni/SBA-15 catalysts

The unpromoted and B-promoted 10%Ni/SBA-15 catalysts synthesized via sequential incipient wetness impregnation approach were assessed for combined steam and CO2 reforming of methane (CSCRM) at various reaction temperatures of 973–1073 K and stoichiometric feed composition. An expected and noteworthy drop in mean NiO crystallite size and BET surface area with boron promotion from 1% to 5%B loading could be due to the agglomeration of B2O3 particles and deboration reaction during calcination and hence blocking mesopores of SBA-15 support at elevated B composition. The complete NiO reduction to metallic Ni0 form was achieved during H2 activation and the reduction temperature of NiO phase was shifted towards higher temperature with B-addition owing to enhancing interaction between the acidic B2O3 and basic NiO phases. For all reaction temperature employed, 3%B appeared to be the optimal promoter loading in terms of reactant conversions and 3%B-10%Ni/SBA-15 catalyst revealed the greatest H2 yield (69.4%) at 1073 K. In addition, CH4 and CO2 conversions were enhanced about 23.2% and 32.4%, correspondingly with rising reaction temperature from 973 to 1073 K. Ratio of H2 to CO varied from 1.26 to 2.71 and the desired H2/CO ratio of about 2 favored for Fischer-Tropsch synthesis was achieved on 3%B-10%Ni/SBA-15 sample at 973 K. Boron promoter suppressed graphitic carbon formation and the amount of carbonaceous deposition was reduced about 4 times. Noticeably, 3%B-10%Ni/SBA-15 was also resilient to metallic Ni0 re-oxidation throughout CSCRM.

Effects of Catalyst Properties on Hydrodesulfurization Activity for Sulfur Removal from Fluid Catalytic Cracking Decant Oils

Removing sulfur from larger ring systems in fluid catalytic cracking decant oils used as needle coke feedstock is the most effective way of reducing the needle coke sulfur content. The large sulfur compounds found in decant oil are incorporated into coke in larger proportions than smaller sulfur compounds upon carbonization. The desirable outcome of decant oil hydrodesulfurization is, therefore, removing sulfur selectively from large polyaromatic ring systems with minimum hydrogen consumption. This study investigates the effects of catalyst properties on hydrodesulfurization activity to remove sulfur from decant oils. Two decant oils (DO-HS and DO-LS) representing a high (2.5 wt %) and low (0.9 wt %) sulfur content decant oil and their vacuum distillation fractions were hydrotreated in a fixed-bed flow reactor. Four catalysts (with varying average pore sizes, promoter atoms, and supports) were prepared with sequential incipient wetness impregnation to evaluate their activities for hydrodesulfurization and...

Investigation of the preparation methodologies of Pd-Cu single atom alloy catalysts for selective hydrogenation of acetylene

Galvanic replacement, co-impregnation and sequential impregnation have been employed to prepare Pd-Cu bimetallic catalysts with less than 1 wt-% Cu and ca. 0.03 wt-% Pd for selective hydrogenation of acetylene in excess ethylene. High angle annular dark field-scanning transmission electron microscopy (HAADF-STEM) and H2 chemisorption results confirmed that Pd-Cu singleatom alloy structures were constructed in all three bimetallic catalysts. Catalytic tests indicated that when the conversion of acetylene was above 99%, the selectivity of ethylene of these three single atom alloy catalysts was still more than 73%. Furthermore, the single atom alloy catalyst prepared by sequential incipient wetness impregnation was found to have the best stability among the three procedures used. Open image in new window

Catalytic decomposition of 2,3-dihydrobenzofuran to monomeric cyclic compounds over Pd/XCs2.5H0.5PW12O40/OMC (ordered mesoporous carbon) (X = 10–30 wt.%) catalysts

A series of Pd/XCs2.5H0.5PW12O40/OMC (ordered mesoporous carbon) (X=10, 15, 20, 25, and 30wt.%) catalysts with different Cs2.5H0.5PW12O40 contents (X, wt%) were prepared by a sequential incipient wetness impregnation method for use in the catalytic decomposition of 2,3-dihydrobenzofuran to monomeric cyclic compounds. 2,3-Dihydrobenzofuran was used as a lignin model compound for representing β-5 linkage of lignin. Acidity of Pd/XCs2.5H0.5PW12O40/OMC catalysts served as an important factor determining the catalytic performance in the reaction. Conversion of 2,3-dihydrobenzofuran and total yield for main products (2-ethylphenol and ethylcyclohexane) increased with increasing acidity of Pd/XCs2.5H0.5PW12O40/OMC catalysts.

Methane partial oxidation over NiO-MgO/Ce0.75Zr0.25O2 catalysts

Methane partial oxidation (MPO) is considered as an alternative method to produce hydrogen because it is an exothermic reaction to afford a suitable H2/CO ratio of 2. However, carbon deposition on a catalyst is observed as a major cause of catalyst deactivation in MPO. In order to find suitable catalysts that prevent the carbon deposition, NiO-MgO/Ce0.75Zr0.25O2 (CZO) supported catalysts were prepared via the co-impregnation (C) and sequential incipient wetness impregnation (S) methods. The amount of Ni loading was fixed at 15 wt-% whereas the amount of MgO loading was varied from 5 to 15 wt-%. The results revealed that the addition of MgO shifted the light-off temperatures to higher temperatures. This is because the Ni surface was partially covered with MgO, and the strong interaction between NiO and NiMgO2 over CZO support led to the difficulty in reducing NiO to active Ni0 and thus less catalytic activity. However, among the catalysts tested, the 15Ni5Mg/CZO (S) catalyst exhibited the best catalytic stability for MPO after 18 h on stream at 750°C. Moreover, this catalyst had a better resistance to carbon deposition due to its high metallic Ni dispersion at high temperature.