Sequential Impregnation Method Research Articles

Optimization of greenhouse gas valorization over ceria‐promoted Co–Ni/graphene oxide catalytic materials using response surface methodology

AbstractBackgroundThe mitigation of global warming effect requires intensified research efforts to reduce greenhouse gas emissions. This study was aimed at investigating the valorization of two principal greenhouse gases, namely carbon dioxide (CO2) and methane (CH4), over CeO2‐doped Co–Ni/GO catalytic materials. The CeO2‐doped Co–Ni/GO catalysts were synthesized using a sequential wet impregnation method and employed for CO2 reforming of CH4. The catalytic materials were characterized using various instrumental techniques. Response surface methodology (RSM) was employed to investigate the impact of process factors, namely reaction temperature (ranging from 700 to 800 °C), CeO2 loading (ranging from 5% to 15%) and feed flowrate (ranging from 10n to 50 mL min−1), on the CH4 conversions.ResultsThe three factors were observed to have significant influence on the CH4 conversion based on analysis of variance. The analysis of the RSM quadratic model revealed that the optimum conditions of 800 °C, 14.22% and 10.00 mL min−1 were obtained for the reaction temperature, CeO2 loading and feed flowrate resulting in maximum CH4 conversion of 98.24%. The desirability function for these results was calculated to be 0.934. The predicted process parameters aligned with the results of the actual experimental analysis.ConclusionThis study has demonstrated that the conversion of CH4 to value‐added products such as syngas can be optimized using RSM. The optimum conditions obtained could be used to improve the process performance. © 2024 Society of Chemical Industry (SCI).

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.

Investigation of the promotion effect of metal oxides on the water-gas shift reaction activity over Pt-MOx/CeO2 catalysts for aqueous phase reforming

Aqueous phase reforming (APR) of methanol is a potential pathway for the effective hydrogen production under relatively mild conditions. The Pt/CeO2 and a series of Pt-MOx/CeO2 (M = Fe, Cr, Mg, Mn) catalysts were prepared by sequential impregnation method and their APR reaction performances were studied. The catalyst properties including valence state of the promoters, the amount of oxygen vacancies, the metal distributions, the adsorption properties of CO and the acidity/basicity of catalysts were characterized and analyzed by XPS, XRD, TEM, CO-TPD, NH3-TPD, CO2-TPD, etc. It was found that the addition of MOx weakened the Pt-CeO2 interaction and promoted the generation of Ptδ+ species with lower valence state, which contribute to the C–H bond cleavage and facilitate methanol conversion. The highest hydrogen production (164.78 mmol) and relatively low CO and CH4 selectivities were obtained over the Pt-MgO/CeO2, while the highest CH4 selectivity was obtained over the Pt-CrOx/CeO2 (2.21%). Over the Pt/CeO2 and Pt-MOx/CeO2 (M = Fe, Cr, Mg, Mn) catalysts, CO2/CH4 ratio correlated well with the catalyst basicity, indicating that the basicity promotes the dissociation adsorption of H2O as well as the water-gas shift (WGS) reaction activity and decreases the methanation activity.

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.

Impact of impregnation sequence on the structure of CoPt/Nb2O5 Fishcer-Tropsch catalysts on the same dispersion basis

Three Nb2O5 supported Pt-promoted cobalt catalysts were prepared by co-impregnation and sequential impregnation methods. The dispersion of cobalt species was controlled by glow discharge plasma technique, and cobalt particle size on all three catalysts are in the same level (4.2–4.6 nm). It was found that the metal precursor impregnation sequence significantly affected the interaction among Co, Pt and Nb2O5, and thus results in different H2 adsorption capacity. Compared to the catalyst prepared by first impregnation of Pt precursor (Pt-Co/Nb2O5), the catalysts prepared by simultaneous impregnation of Co and Pt precursors (CoPt/Nb2O5) and first Co impregnation (Co-Pt/Nb2O5) obtained a significantly decreased interaction among Co and Nb2O5. Moreover, high cobalt reducibility (>88 %) was realized at such high cobalt dispersions on these two catalysts, the corresponding weaker H2 adsorption strength and more active sites resulted in their 1.8 times higher FTS activities than Pt-Co/Nb2O5.

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.

Performance of the ρ- Al2O3 based Ag promoted Pd/ Al2O3 catalyst during Acetylene hydrogenation with an ideal feed

Catalytic hydrogenation of acetylene was studied with an ideal feed with a catalyst prepared from different alumina support and with varying quantities of promoter addition. Silver promoted palladium alumina catalysts were prepared on the transition alumina, ρ-alumina and the catalyst performance was compared with the traditional palladium alumina catalyst based on α-alumina. The catalyst supports were prepared using the granulation technique and sequential impregnation method was used for the catalyst preparation. The silver metal loading was varied in the catalysts and the impact of varied promoter quantity was also studied. The supports were characterized for the acidity, alumina phase, and catalyst characterization was done using TEM, TPR, and BET method to understand the difference between catalysts prepared on different types of alumina support. A fixed bed catalyst reaction was used for the performance evaluation and an ideal gas with acetylene and nitrogen was used as the feed. The catalyst evaluation gives the comparative performance of the catalysts at different temperature conditions. Acetylene conversion and ethylene selectivity in the product were evaluated. The spent catalyst analysis was done using TGA and CHN analysis was performed to understand the carbon deposition and by-product formation during the reaction with different types of catalysts.

Improved methane dehydroaromatization reaction over Mo and Cr co-doped ZSM-5 catalyst

We prepared Mo and Cr co-loaded ZSM-5 (Mo/Cr/ZSM-5) by a sequential impregnation method and applied it to methane dehydroaromatization (MDA) reaction.

Decoration of Ru nanoparticles with mononuclear MoOx boosts the hydrodeoxygenation of amides to amines

The selective hydrodeoxygenation (HDO) of amides is a key methodology to producing amines, yet it remains a great challenge due to the highly stable amide molecular structure. In this study a series of 2RuxMo/SiO2 (x = 0 ∼ 3) catalysts were prepared with sequential impregnation method followed by reduction. The reaction tests showed that the target amine yield presented a volcano-shape dependence on the Mo content, and reached the highest value at the Mo content of 0.2 wt% which corresponded to a Mo/Ru atomic ratio of 0.11 and a Mo surface density of 0.08. By contrast, a higher Mo content resulted in dramatic decrease in both activity and selectivity. By using HAADF-STEM, X-ray absorption spectroscopy (XAS), H2-TPR and CO-chemisorption, the structure of the best-performance 2Ru0.2Mo/SiO2 catalyst was identified as Ru NPs of ∼ 2 nm decorated with mononuclear Mo5+Ox species, which was in contrast with the polymeric MoO2-like species partially covering the Ru surface for the 2Ru3Mo/SiO2. Kinetic studies revealed that the reaction order with respect to CyCONH2 was 1.2, −0.1 and −0.5 over the 2Ru/SiO2, 2Ru0.2Mo/SiO2 and 2Ru3Mo/SiO2, respectively, which indicated amide was selectively activated on the low-coordinated Mo5+Ox sites while H2 was activated on the Ru sites and the reaction proceeded at the Mo-Ru interface. The turnover frequency based on interfacial Ru-Mo sites reached 407.8 h−1, which was more than twofold higher than that of Ru-W system (175.6 h−1) we previously reported.

C–O Hydrogenolysis of C3–C4 Polyols Selectively to Terminal Diols over Pt/W/SBA-15 Catalysts

Pt/W/SBA-15 catalysts (with Pt-loading = 0.5–4 wt% and W-loading = 1 wt%) prepared by the sequential impregnation method were evaluated for selective C–O cleavage of erythritol and glycerol in an aqueous medium. The Pt and W particles dispersed on SBA-15 approached close proximity at higher Pt loadings and afforded synergistic enhancement in C–O hydrogenolysis activity/selectivity. 1,4-Butanediol yields of 30.9% (at 190 °C, 50 bar H2 and 24 h) and 1,3-propanediol yields of 34.4% (at 190 °C, 50 bar H2 and 12 h of reaction) were obtained over these catalysts. Pt nanoparticles (facilitating dissociative H2 adsorption and spillover) and W (present as acidic oligomeric WOx species; activating and coordinating the polyol via 1°-OH group) worked in tandem for the selective hydrogenolysis of polyols yielding terminal diols of industrial demand.

Improved propylene selectivity and superior catalytic performance of Ga-xMg/ZSM-5 catalysts for propane dehydrogenation (PDH) reaction

In recent years, Ga-based catalysts attract much attention in propane dehydrogenation (PDH) reaction due to environmental friendliness and low cost. Nevertheless, it is still challenging to obtain high selectivity of propylene under harsh reaction conditions. In this work, the supported catalysts (Ga-xMg/ZSM-5) were prepared with the sequential impregnation method and applied in the PDH reaction. The results show that MgO as an additive reduces the acidity of the catalysts, promotes the dispersion of Ga2O3 and improves the selectivity of propylene. As a result, the average particle size of the Ga/ZSM-5 catalyst is larger (4.5 nm), and the initial propylene selectivity is only 71.0 %. In contrast, the optimal Ga-0.7Mg/ZSM-5 catalyst shows the smallest particle size (2.4 nm) and the highest propylene selectivity of 90.8 %. In comparison with the previous GaOx catalysts in literatures, the Ga-0.7Mg/ZSM-5 catalyst exhibits a superior production rate of propylene (rC3H6) based on either catalyst weight or Ga2O3 weight.

Non-oxidative dehydrogenation of propane to propene over Pt-Sn/Al2O3 catalysts: Identification of the nature of active site

Supported platinum-tin over various oxide supports have been widely recognized as the efficient propane dehydrogenation catalysts due to their excellent activity, C3H6 selectivity and stability after oxidative regeneration. The nature of the active species of the Pt-Sn catalysts is still under debate. Here, by controlling the formation of Pt-Sn chloride complexes during the impregnation stage, we managed to tune spatial distribution of Pt and Sn species over Al2O3 and further influence the degree of alloying between reduced Pt and Sn. The structure characterization revealed the co-impregnation method tend to generate PtSn alloy active site, while sequential impregnation of Pt on pre-synthesized Sn/Al2O3 tend to form Sn partially modification of Pt. Performance evaluation demonstrated that the Pt clusters partially modified by reduced Sn exhibited much higher activity and longer life-time than PtSn alloy counterparts under similar C3H6 selectivity. With further optimization, the Pt-Sn/Al2O3 prepared by sequential impregnation method achieved over 64.1 μmol/gcat/h propylene formation rate at the 30% propane conversion with the C3H6 selectivity exceeding 99%.

Fuel grade bioethanol reforming in a fluidized bed reactor over highly durable Pt-Ni/CeO2-SiO2 catalysts

In this work, oxidative steam reforming reaction has been investigated in a fluidized bed reactor (FBR) under a fuel grade bioethanol feeding over a 2Pt-10Ni/CeO2-SiO2 catalyst. In a process intensification view, the selection of raw feeds produced from bioethanol paves the way towards a cheaper production of bio-hydrogen. The employed catalyst was prepared by the sequential wet impregnation method and was tested alone as well as in the presence of the bare support as filler of the FBR. Very long durability tests (hundreds of hours) were performed at 500°C under a stream with a water to ethanol ratio of 4 and oxygen to ethanol ratio of 0.5. When the catalyst was tested along with the support, a stable behaviour was recorded for 100 h of time-on-stream (TOS), corresponding to complete ethanol conversion and H2 yield values above 50%. However, for higher TOS, a gradual catalyst deactivation was observed and, after 400 h, hydrogen yield was below 10%. Conversely, the catalyst alone displayed complete conversion form more than 200 hours and, after a partial deactivation, a new stationary condition was reached with no more activity loss. Both the spent catalysts were characterized by several techniques, finding that the presence of the filler promote methane decomposition and coke deposition on catalyst surface. On the other hand, a very low carbon formation rate was recorded over the 2Pt-10Ni/CeO2-SiO2 catalyst, which was shown to be a very promising formulation in comparison with data available in the recent literature.

Interface-directed epitaxially growing nickle ensembles as efficient catalysts in dry reforming of methane

Supported nickel catalysts are promising candidates for dry reforming of methane, but agglomeration of Ni0 and coke deposition hinder the industrial applications. Herein, we report a novel interface-directed synthetic approach to construct distinct metal ensembles by carefully tuning the compositions of the carriers. A Zr-Mn-Zn ternary oxide-supported Ni catalyst, together with the respective binary oxide-supported analogues, was synthesized by adopting a sequential co-precipitation and wetness impregnation method. Combined characterization techniques identify distinct catalyst models, including (i) conventional NiO nanoparticles with different sizes on Zr-Mn and Zr-Zn, and (ii) epitaxially growing NiO ensembles of a few nanometers thickness at the periphery of MnZnOx particles. These catalysts exhibit divergent responses in the catalytic testing, with the ternary oxide system significantly outperforming the binary analogues. The strong electronic interactions between Mn-Ni increase Ni dispersion and the activity while the stability is strengthened upon Zn addition. Both high activity, high selectivity, and remarkable stability are attained upon co-adding Mn and Zn. The interfaces between Ni and Zr-Mn-Zn rather than the physical contacts of individual oxide-supported analogues through mechanical mixing are keys for the outstanding performance.

Surface structure modulating of Ni-Pt bimetallic catalysts boosts n-dodecane steam reforming

Surface structure of bimetallic catalysts plays a vital role in converting liquid hydrocarbon fuels to on-site H2 for fuel cell application via steam reforming process. Herein, Pt-outer (Pt-Ni/Al2O3), Pt-outer & inner (NiPt/Al2O3) and Pt-inner (Ni-Pt/Al2O3) catalysts prepared through sequential impregnation and co-impregnation method were employed in n-dodecane steam reforming. Performance results showed that the activity was as followed: Ni-Pt/Al2O3 > NiPt/Al2O3 > Pt-Ni/Al2O3. Characterization results from XRD, H2-TPR, XPS, STEM-EDX, in situ CO-DRIFT and EXAFS suggest that Ni-Pt/Al2O3 catalyst was more preferable to form Nix+ species and NiPt alloy compared with Pt-Ni/Al2O3 and NiPt/Al2O3 catalysts. C2H6-TPSR and H2O-TPSR experimental indicated that Ni-Pt/Al2O3 catalyst and Nix+ species mostly contributed to CC, CH bond and H2O activation. The superior activity of Ni-Pt/Al2O3 bimetallic catalyst in n-dodecane steam reforming linked with the synergistic effect between Ni-enriched surface, Nix+ species and NiPt alloy which facilitated CHx group formation, H2O activation and CHx group oxidation.

Hydrogen Production through Autothermal Reforming of Ethanol: Enhancement of Ni Catalyst Performance via Promotion

Autothermal reforming of bioethanol (ATR of C2H5OH) over promoted Ni/Ce0.8La0.2O1.9 catalysts was studied to develop carbon-neutral technologies for hydrogen production. The regulation of the functional properties of the catalysts was attained by adjusting their nanostructure and reducibility by introducing various types and content of M promoters (M = Pt, Pd, Rh, Re; molar ratio M/Ni = 0.003–0.012). The composition–characteristics–activity correlation was determined using catalyst testing in ATR of C2H5OH, thermal analysis, N2 adsorption, X-ray diffraction, transmission electron microscopy, and EDX analysis. It was shown that the type and content of the promoter, as well as the preparation mode (combined or sequential impregnation methods), determine the redox properties of catalysts and influence the textural and structural characteristics of the samples. The reducibility of catalysts improves in the following sequence of promoters: Re < Rh < Pd < Pt, with an increase in their content, and when using the co-impregnation method. It was found that in ATR of C2H5OH over bimetallic Ni-M/Ce0.8La0.2O1.9 catalysts at 600 °C, the hydrogen yield increased in the following row of promoters: Pt < Rh < Pd < Re at 100% conversion of ethanol. The introduction of M leads to the formation of a NiM alloy under reaction conditions and affects the resistance of the catalyst to oxidation, sintering, and coking. It was found that for enhancing Ni catalyst performance in H2 production through ATR of C2H5OH, the most effective promotion is with Re: at 600 °C over the optimum 10Ni-0.4Re/Ce0.8La0.2O1.9 catalyst the highest hydrogen yield 65% was observed.

The Effect of ZrO2 as Different Components of Ni-Based Catalysts for CO2 Reforming of Methane and Combined Steam and CO2 Reforming of Methane on Catalytic Performance with Coke Formation

The role of ZrO2 as different components in Ni-based catalysts for CO2 reforming of methane (CRM) has been investigated. The 10 wt.% Ni supported catalysts were prepared with ZrO2 as a support using a co-impregnation method. As a promoter (1 wt.% ZrO2) and a coactive component (10 wt.% ZrO2), the catalysts with ZrO2 were synthesized using a co-impregnation method. To evaluate the effect of the interaction, the Ni catalyst with ZrO2 as a coactive component was prepared by a sequential impregnation method. The results revealed that the activity, the selectivity, and the anti-coking ability of the catalyst depend upon the ZrO2 content, the Ni-ZrO2 interaction, basicity, and oxygen mobility of each catalyst resulting in different Ni dispersion and oxygen transfer pathway from ZrO2 to Ni. According to the characterization and catalytic activation results, the Ni catalyst with low ZrO2 content (as a promoter) presented highest selectivity toward CO owning to the high number of weak and moderate basic sites that enhance the CO2 activation-dissociation. The lowest activity (CH4 conversion ≈ 40% and CO2 conversion ≈ 39%) with the relatively high quantity of total coke formation (the weight loss of the spent catalyst in TGA curve ≈ 22%) of the Ni catalyst with ZrO2 as a support is ascribed to the lowest Ni dispersion due to the poor Ni-ZrO2 interaction and less oxygen transfer from ZrO2 to the deposited carbon on the Ni surface. The effect of a poor Ni-ZrO2 interaction on the catalytic activity was deducted by decreasing ZrO2 content to 10 wt.% (as a coactive component) and 1 wt.% (as a promoter). Although Ni catalysts with 1 wt.% and 10 wt.% ZrO2 provided similar oxygen mobility, the lack of oxygen transfer to coke during CRM process on the Ni surface was still indicated by the growth of carbon filament when the catalyst was prepared by co-impregnation method. When the catalyst was prepared by a sequential impregnation, the intimate interaction of Ni and ZrO2 for oxygen transfer was successfully developed through a ZrO2-Al2O3 composite. The interaction in this catalyst enhanced the catalytic activity (CH4 conversion ≈ 54% and CO2 conversion ≈ 50%) and the oxygen transport for carbon oxidation (the weight loss of the spent catalyst in TGA curve ≈ 7%) for CRM process. The Ni supported catalysts with ZrO2 as a promoter prepared by co-impregnation and with ZrO2 as a coactive component prepared by a sequential impregnation were tested in combined steam and CO2 reforming of methane (CSCRM). The results revealed that the ZrO2 promoter provided a greater carbon resistance (coke = 1.213 mmol·g−1) with the subtraction of CH4 and CO2 activities (CH4 conversion ≈ 28% and CO2 conversion ≈ %) due to the loss of active sites to the H2O activation-dissociation. Thus, the H2O activation-dissociation was promoted more efficiently on the basic sites than on the vacancy sites in CSCRM.

A comparison of Structure–Activity of Cu-Modified Over Different Mesoporous Silica Supports for Catalytic Conversion of Levulinic Acid

Catalytic hydrogenation of levulinic acid (LA) to γ-valerolactone (GVL) was investigated over four different types of mesoporous silica (SBA-15, MCM-48, MCM-41, and KIT-6) supported copper (5 wt.%) catalysts. The Cu was incorporated into mesoporous silica supports by a sequential impregnation method. A detailed investigation of the support structure–activity correlation and the performance of the catalysts in LA conversion was studied. Detailed characterisation techniques were used to evaluate the physical and catalytic properties of the studied catalysts. The structure type and physicochemical properties of the silica support had a significant effect on the overall performance of the catalysts. Among them, over Cu/SBA-15 catalyst, a complete levulinic acid (LA) conversion with ~ 98% gamma valerolactone (GVL) selectivity was achieved at 265 °C under ambient H2 pressure. The superior performance of Cu/SBA-15 catalyst was attributed to the high surface acidity, reducibility of Cu oxides species, and highly dispersed Cu particles over SBA-15 structure. The results confirmed that the activity of the catalysts is significantly influenced by the textural properties, surface acidity and copper dispersion. Durability of all the catalysts were also tested for 50 h time on stream and over SBA-15 catalyst, only a small drop in the activity was observed.

Hydrogen Production From Steam Gasification of Palm Kernel Shell Using Sequential Impregnation Bimetallic Catalysts

Zeolite β supported bimetallic Fe and Ni catalysts have been prepared using sequential impregnation method and calcined at temperatures between 500-700 ºC. The catalytic activity of these catalysts in a steam gasification of palm kernel shell was tested in a fixed-bed quartz micro-reactor at 700 ºC. Both Fe and Ni active metals present in FeNi/BEA and NiFe/BEA catalysts are corresponding to Fe2O3 and NiO. Different calcination temperatures and different sequence in metal addition have a significant effect to the catalytic activity where FeNi/BEA (700) shows the highest hydrogen produced than other catalysts.

The Effect of Addition Method of Impregnation Solution on Properties and Performance of Pd-Ag/Al2O3 Catalyst in Tail-End Acetylene Selective Hydrogenation

The impregnation of alumina support with PdCl2 solution was investigated in batch and semi-batch operation modes using a recycle packed-bed reactor. UV-visible analysis was used to evaluate the kinetics of Pd adsorption on alumina support. Transient palladium adsorption data showed that Pd adsorption was very rapid completing within few minutes. Bi-metallic Pd-Ag/Al2O3 catalysts were synthesized by sequential impregnation method. CO-chemisorption, CO-TPD and FE-SEM tests were used to characterize the synthesized bi-metallic samples. Catalytic performance of the samples was evaluated for tail-end acetylene selective hydrogenation process in a fixed-bed reactor. Moreover, the deactivation of the catalysts was evaluated mathematically by integral method of analysis, considering reaction kinetics as power laws in terms of nth orders in H2 and C2H2 partial pressures. It was observed that by batch-wise addition of Pd precursor solution, a sample was obtained with lowest amount of Pd dimmers that had highest ethylene selectivity and lowest hydrogenation reaction rate.