Experience in introducing a cobalt catalyst technology for the synthesis of hydrocarbons from CO and H<Subscript>2</Subscript>

The experience in introducing the technology of for the production of a silica-supported cobalt catalyst under industrial conditions is summarized. The catalyst is designed for the selective synthesis of С₅₊ hydrocarbons from СО and Н₂, including macromolecular hydrocarbons С₃₅₊. The technology has been implemented at ZAO Samara Catalyst Factory. Parameters of the technological process are adjusted to allow for the features of existing equipment in preparing an experimental industrial lot of catalysts. The optimum technological mode of support preparation (evacuation to avoid granule cracking), its impregnation (at 80°С over 30 min), and the thermal treatment of the catalyst (in programmed mode at a maximum temperature of 400°С over a total of 9 h) are determined. The catalysts of an experimental industrial lot of 1 m³ conform to the new technical conditions in their physicochemical and catalytic properties.     

Inhibiting HDS and HYD reactions with quinoline on Co(Ni)–PMo(W)/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalysts: Effect of active phase composition on stability in the hydrotreatment of a model petroleum raw material

Со(Ni)–PMo(W)/Al₂O₃ catalysts are prepared using Keggin heteropoly acids H₃PMo(W)₁₂O₄₀ and cobalt (nickel) citrate. The physicochemical properties of the catalysts are studied via low-temperature nitrogen adsorption, X-ray photoelectron spectroscopy, and high-resolution transmission electron microscopy. Their catalytic properties are determined in the hydrotreatment of a model raw material containing dibenzothiophene, naphthalene, and different amounts of quinoline (up to 1000 ppm of nitrogen), and in the hydrotreatment of a straight-run diesel fraction and vacuum gas oil. The composition of Со(Ni)–PMo(W)/Al₂O₃ catalysts plays an important role in the hydrotreatment of a complex hydrocarbon raw material. Ni–PW/Al₂O₃ catalyst is more resistant to organonitrogen inhibitors than Ni(Co)–PMo/Al₂O₃ samples with more reactive active sites. Ni–PW/Al₂O₃ catalyst provides the greatest depth of conversion for sulfur- and nitrogen-containing compounds and polycyclic aromatic hydrocarbons in the hydrotreatment of vacuum gas oil.     

Supercritical fluid CO<Subscript>2</Subscript>-extraction regeneration of nickel–molybdenum catalyst for hydrotreatment

Results from studying the supercritical fluid СО₂-extraction regeneration of DN-3531 industrial nickel–molybdenum hydrotreatment catalyst in the temperature range of 323.15–383.15 K, at pressures of up to 30 MPa, and with modification of the basic extragent with such polar compounds as chloroform, methanol, ethanol, acetone, and dimethylsulfoxide (DMSO), are presented. The order of modifiers corresponds to the increase in the solubilizing ability of modified supercritical carbon dioxide (SC-СО₂) with respect to catalyst- deactivating deposits. With DMSO as the most efficient modifier, however, not only are deactivating compounds removed but nickel and molybdenum as well, considerably reducing the final activity of a regenerated sample. During extraction regeneration, the content of coke in the catalyst is reduced by two-thirds, while the specific surface area and the pore volume grow. The activity of the deactivated catalyst in dibenzothiophene hydrodesulfurization (HDS) and naphthalene hydrogenation grows by several hundred per cent after one-time SC-CO₂ treatment and is 2.5 times higher than for a sample regenerated using the traditional oxidative method.     

Influence of phosphorous addition on Bi<Subscript>3</Subscript>Mo<Subscript>2</Subscript>Fe<Subscript>1</Subscript> oxide catalysts for the oxidative dehydrogenation of 1-butene

Bi₃Mo₂Fe₁P _x oxide catalysts were prepared by a co-precipitation method and the influence of phosphorous content on the catalytic performance in the oxidative dehydrogenation of 1-butene was investigated. The addition of phosphorous up to 0.4mole ratio to Bi₃Mo₂Fe₁ oxide catalyst led to an increase in the catalytic performance; however, a higher phosphorous content (above P=0.4) led to a decrease of conversion. Of the tested catalysts, Bi₃Mo₂Fe₁P_0.4 oxide catalyst exhibited the highest catalytic performance. Characterization results showed that the catalytic performance was related to the quantity of a π-allylic intermediate, facile desorption behavior of adsorbed intermediates and ability for re-oxidation of catalysts.     

Gas-phase epoxidation of butadiene: Effect of the concentration and distribution of cesium on the properties of the Ag/α-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalyst

Using the well-known patent methods, we have synthesized 1,3-butadiene epoxidation α-Al₂O₃ supported catalysts containing 15 wt % of Ag and 250–1500 ppm of Cs (Johnson Matthey, H16P07). The physicochemical properties of samples are systematically studied by varying the dispersion of supported silver, the amount of an introduced promoter, and its distribution over the surface of a catalyst. Catalytic tests of samples show that the optimum amount of a promoter depends directly on the surface of a catalyst. With optimum promotion, the steady-state activity of catalysts is determined by the dispersion of supported silver. In the course of catalytic tests, it is established that the shape of kinetic curves is governed by the excess or lack of Cs in a catalyst, thus providing a method for optimizing the concentration of the promoter. An analysis of the energy dispersion spectra (EDS) is applied for the first time to study the distribution of Cs over the surface of promoted catalysts. It is shown that thermal treatment favors the uniform distribution of a promoter over the surface of a catalyst and shortens the time required to attain its steady-state activity in catalytic tests. In our work, the steady-state productivity of catalysts reaches 0.5 g of 3,4-epoxy-1-butene per gram of the catalyst per hour, thus exceeding the claimed patent values.     

Investigating active centers of industrial catalysts for the oxidative chlorination of ethylene on a γ-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> surface

Selecting the best catalyst for large-scale industrial processes of the oxychlorination of ethylene (OCE) is a practical task of great importance. In such processes, even a slight reduction in selectivity results in considerable losses of raw materials. The enhancement of selectivity requires knowledge of the structure of the catalysts’ surfaces and the mechanism of the process of oxidative chlorination of ethylene into 1,2-dichloroethane (1,2-DCE). The structure of active sites of copper chloride catalysts on the surface of alumina was studied by physicochemical methods of IR spectroscopy and DTA. The structure was described for the active sites of catalysts for the oxidative chlorination of ethylene into (1,2-DCE) of two types, CuCl₂ and CuCl on γ-Al₂O₃: H1 (Harshow, United States) and OXYMAX-B (MEDC-B) (Sǜd-Chemie Catalysts, Germany). It was ascertained that complex compounds with [CuCl₄]⁻² and [CuCl₂]⁻¹ are formed upon interaction between the active phase of the catalyst (copper chlorides CuCl₂ or CuCl), and the surface groups of the support γ-Al₂O₃ (≡Al-OH) (this observation does not fall into the known theory of their structure). In accordance with the results from our study, a method was elaborated for synthesizing a catalyst with the optimum properties for OCE, and a pilot setup for the detailed investigation of this process was built. The possibility of cutting ethylene losses in half during deep oxidation and eliminating the formation of side products by a factor of 1.5–2 was demonstrated by the industrial production of 1,2-DCE and vinyl chloride at OOO Karpatnaftokhim in Kalush. The method for producing 1,2-DCE is protected by a Ukranian patent.     

Oxidative reforming of methane on structured Ni-Al<Subscript>2</Subscript>O<Subscript>3</Subscript>/cordierite catalysts

The catalytic properties of Ni/Al₂O₃ composites supported on ceramic cordierite honeycomb monoliths in oxidative methane reforming are reported. The prereduced catalyst has been tested in a flow reactor using reaction mixtures of the following compositions: in methane oxidation, 2–6% CH₄, 2–9% O₂, Ar; in carbon dioxide and oxidative carbon dioxide reforming of methane, 2–6% CH₄, 6–12% CO₂, and 0–4% O₂, and Ar. Physicochemical studies include the monitoring of the formation and oxidation of carbon, the strength of the Ni-O bond, and the phase composition of the catalyst. The structured Ni-Al₂O₃ catalysts are much more productive in the carbon dioxide reforming of methane than conventional granular catalysts. The catalysts performance is made more stable by regulating the acid-base properties of their surface via the introduction of alkali metal (Na, K) oxides to retard the coking of the surface. Rare-earth metal oxides with a low redox potential (La₂O₃, CeO₂) enhance the activity and stability of Ni-Al₂O₃/cordierite catalysts in the deep and partial oxidation and carbon dioxide reforming of methane. The carbon dioxide reforming of methane on the (NiO + La₂O₃ + Al₂O₃)/cordierite catalyst can be intensified by adding oxygen to the gas feed. This reduces the temperature necessary to reach a high methane conversion and does not exert any significant effect on the selectivity with respect to H₂.     

Hydroprocessing of straight run diesel mixed with light cycle oil from fluid catalytic cracking,using sulfide NiMo catalyst on zeolite-containing supports

It is proposed that the sulfide NiMo system supported on alumina-SAPO-31 composite (NiMo/Al₂O₃-SAP catalyst) be used to obtain high-quality diesel fuel from a mixture of straight run diesel (SRGO) and light cycle oil (LCO) produced by fluid catalytic cracking (FCC). It is shown that the use of this catalyst ensures the synthesis of diesel fuel of higher quality upon hydroprocessing a feedstock with 30 wt % LCO, compared to the traditional sulfide NiMo/Al₂O₃ or CoMo/Al₂O₃ catalysts. It is found that the content of aliphatic hydrocarbons is raised in the products of hydrotreatment, compared to the initial feedstock. This confirms the ability of NiMo/Al₂O₃-SAP catalyst to facilitate the reaction of ring opening. Using the proposed catalyst should improve the quality of diesel fuels obtained via the hydroprocessing of LCO-containing feedstock.     

Regeneration of H<Subscript>3</Subscript>PW<Subscript>12</Subscript>O<Subscript>40</Subscript> catalyst in the direct preparation of dichloropropanol (DCP) from glycerol and hydrochloric acid gas

Methods for regenerating H₃PW₁₂O₄₀ catalyst in the solvent-free direct preparation of dichloropropanol (DCP) from glycerol and hydrochloric acid gas were investigated. Regenerated H₃PW₁₂O₄₀ catalyst was then applied to the solvent-free direct preparation of DCP. In the solvent-free direct preparation of DCP, selectivity for DCP over H₃PW₁₂O₄₀ catalyst regenerated by method I (recovery of solid H₃PW₁₂O₄₀ catalyst by evaporating homogeneous liquidphase product solution) significantly decreased with increasing recycling run, while that over H₃PW₁₂O₄₀ catalyst regenerated by method II (regeneration of H₃PW₁₂O₄₀ catalyst by oxidative calcination of solid product recovered by method I) was slightly decreased with no significant catalyst deactivation with respect to recycling run. On the other hand, selectivity for DCP over H₃PW₁₂O₄₀ catalyst regenerated by method III (regeneration of H₃PW₁₂O₄₀ catalyst by recrystallization and subsequent oxidative calcination of solid product recovered by method II) was the same as that over fresh catalyst without any catalyst deactivation with respect to recycling run. Thus, method III was found to be the most efficient method for the regeneration of H₃PW₁₂O₄₀ catalyst.     

Catalytic performance of CuCl<Subscript>2</Subscript>-modified V<Subscript>2</Subscript>O<Subscript>5</Subscript>-WO<Subscript>3</Subscript>/TiO<Subscript>2</Subscript> catalyst for Hg<Superscript>0</Superscript> oxidation in simulated flue gas

CuCl₂-SCR catalysts prepared by an improved impregnation method were studied to evaluate the catalytic performance for gaseous elemental mercury (Hg⁰) oxidation in simulated flue gas. Hg⁰ oxidation activity of commercial SCR catalyst was significantly improved by the introduction of CuCl₂. Nitrogen adsorption, XRD, XRF and XPS were used to characterize the catalysts. The results indicated that CuCl₂ was well loaded and highly dispersed on the catalyst surface, and that CuCl₂ played an important role for Hg⁰ catalytic oxidation. The effects of individual flue gas components on Hg⁰ oxidation were also investigated over CuCl₂-SCR catalyst at 350 oC. The co-presence of NO and NH₃ remarkably inhibited Hg⁰ oxidation, while this inhibiting effect was gradually scavenged with the decrease of GHSV. Further study revealed the possibility of simultaneous removal of Hg⁰ and NO over CuCl₂-SCR catalyst in simulated flue gas. The mechanism of Hg⁰ oxidation was also investigated.     

Oxidative Dehydrogenation of <Emphasis Type="Italic">n</Emphasis>-Butene to 1,3-Butadiene over Sulfated ZnFe<Subscript>2</Subscript>O<Subscript>4</Subscript> Catalyst

Oxidative dehydrogenation of n-butene to 1,3-butadiene over sulfated ZnFe₂O₄ catalyst was carried out in a continuous flow fixed-bed reactor. The effect of sulfation on the catalytic performance of ZnFe₂O₄ was investigated. Sulfated ZnFe₂O₄ catalyst showed a better catalytic performance than ZnFe₂O₄ catalyst in the oxidative dehydrogenation of n-butene. Acid–base property of sulfated ZnFe₂O₄ catalyst was measured by TPD experiment, with an aim of correlating the catalytic performance with the surface acid–base property of the catalyst. It was revealed that the catalytic performance of sulfated ZnFe₂O₄ catalyst was closely related to the surface weak-acid density of the catalyst. The enhanced acidity of sulfated ZnFe₂O₄ catalyst was responsible for its high catalytic performance in the oxidative dehydrogenation of n-butene. Thus, sulfation served as an efficient method for improving catalytic performance of ZnFe₂O₄ in the oxidative dehydrogenation of n-butene.     

Unexpected Support Effect in Hydrotreating: Evidence of a Metallic Character for ReS<Subscript>2</Subscript>/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> and ReS<Subscript>2</Subscript>/SiO<Subscript>2</Subscript> Catalysts

Abstract  

Rhenium sulfide based catalysts were prepared by the incipient wetness impregnation method over alumina and silica supports and evaluated for 4,6-dimethyldibenzothiophene hydrodesulfurization in a high-pressure stirred-tank reactor. The catalyst prepared over silica was about six times more active for hydrodesulfurization than the corresponding catalyst prepared over alumina and a NiMo/Al₂O₃ industrial reference catalyst. This surprising and positive SiO₂ support effect was explained by a metallic character of the supported sulfide, which was demonstrated using a kinetic approach of competitive hydrogenations and by XPS characterization.     

Hydrocracking of Vacuum Gasoil on NiMoW/AAS-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> Trimetallic Catalysts: Effect of the W : Mo Ratio

The effect of the W: (W + Mo) atomic ratio in NiMoW trimetallic catalysts on their catalytic and physicochemical properties is studied. The catalysts are prepared by impregnating a carrier containing amorphous aluminosilicate (AAS) and aluminium oxide with an aqueous solution containing Ni, Mo, W compounds, and citric acid. They are studied via XRF, TEM, NH₃ TPD, and low-temperature nitrogen adsorption and are tested in the hydrocracking of vacuum gasoil (VGO). The average length of a sulfide active component layer shrinks as the amount of Mo increases and the amount of W in the catalyst is reduced. XPS data indicate that the degree of sulfidation of tungsten in NiMoW trimetallic catalysts is lower than in NiW catalyst. Testing of the catalysts in hydrocracking of a straight-line VGO at 390–420°C, 16 MPa, a feedstock hourly space velocity (FHSV) of 0.71 h^?1, and a H₂: VGO ratio of 1200 L/L shows the activities of hydrodesulfurization, hydrodenitrogenation, hydrogenation, and hydrocracking grow along with the W: (W + Mo) ratio. When the process pressure is high and the amount of sulfur in the NiW feedstock is low, the catalysts have higher activity in the target reactions of VGO hydrocracking than NiMo catalyst.     

Effect of Nickel as Dopant in Mn/TiO<Subscript>2</Subscript> Catalysts for the Low-Temperature Selective Reduction of NO with NH<Subscript>3</Subscript>

Nickel doped manganese oxide supported on titania materials were investigated for the low-temperature NH₃-SCR. For this purpose, a series of Ni modified Mn/TiO₂ catalysts were prepared and evaluated for the low-temperature SCR of NO with ammonia in the presence of excess oxygen. The catalytic performance of these materials was compared with respect to the nickel weight percentage in order to examine the correlation between physicochemical characteristics and reactivity of optimized materials. It was found that the 5% Mn–2% Ni/TiO₂ catalyst showed the highest activity and yielded 100% NO conversion at 200 °C. XRD results reveal highly dispersed manganese–nickel species on TiO₂ support for the Mn–Ni/TiO₂ catalysts. Our TPR data results suggested an increase in reducibility of manganese species in Mn–Ni/TiO₂ catalysts. The absence of the high-temperature (736 K) peak indicates that the dominant phase is MnO₂. This increase of reducibility and dominant MnO₂ phase seems to be the reason for the enhanced activity and time on stream patterns of nickel-promoted titania-supported manganese catalysts. BET results illustrate that the high NO conversion is strongly dependant on the specific surface area and pore volume of this catalyst. All the physicochemical techniques we used suggested that the composition of manganese and nickel oxides on the support surface is playing an important role for the enhancement of NO conversion and the prominent time on stream stability.     

Effect of H<Subscript>2</Subscript>O<Subscript>2</Subscript> modification of H<Subscript>3</Subscript>PW<Subscript>12</Subscript>O<Subscript>40</Subscript>@carbon for m-xylene oxidation to isophthalic acid

The production of isophthalic acid (IPA) from the oxidation of m-xylene (MX) by air is catalyzed by H₃PW₁₂O₄₀ (HPW) loaded on carbon and cobalt. We used H₂O₂ solution to oxidize the carbon to improve the catalytic activity of HPW@C catalyst. Experiments reveal that the best carbon sample is obtained by calcining the carbon at 700 °C for 4 h after being impregnated in the 3.75% H₂O₂ solution at 40 °C for 7 h. The surface characterization displays that the H₂O₂ modification leads to an increase in the acidic groups and a reduction in the basic groups on the carbon surface. The catalytic capability of the HPW@C catalyst depends on its surface chemical characteristics and physical property. The acidic groups play a more important part than the physical property. The MX conversion after 180 min reaction acquired by the HPW@C catalysts prepared from the activated carbon modified in the best condition is 3.81% over that obtained by the HPW@C catalysts prepared from the original carbon. The IPA produced by the former is 46.2% over that produced by the latter.     

CO and CO<Subscript>2</Subscript> Methanation Over Ni/SiC and Ni/SiO<Subscript>2</Subscript> Catalysts

Ni/SiC and Ni/SiO₂ catalysts prepared by both wet impregnation (WI) and deposition–precipitation (DP) methods were compared for CO and CO₂ methanation. The prepared catalysts were characterized using N₂ physisorption, temperature-programmed reduction with H₂ (H₂-TPR), H₂ chemisorption, pulsed CO₂ chemisorption, temperature-programmed desorption of CO₂ (CO₂-TPD), transmission electron microscopy, and X-ray diffraction. H₂-TPR analysis revealed that the catalysts prepared by DP exhibit stronger interaction between the nickel oxides and support than those prepared by WI. The former catalysts exhibit higher Ni dispersions than the latter. The catalytic activities for both reactions over Ni/SiC and Ni/SiO₂ catalysts prepared by WI increase on increasing the Ni content from 10 to 20 wt%. The Ni/SiC catalyst prepared by DP shows higher catalytic activity for CO and CO₂ methanation than that of the Ni/SiC catalyst prepared by WI. Furthermore, it exhibits the highest catalytic activity for CO methanation among the tested catalysts. The high Ni dispersion achieved by the DP method and the high thermal conductivity enabled by SiC are beneficial for both CO and CO₂ methanation.     

Hierarchical ordered meso/macroporous H<Subscript>3</Subscript>PW<Subscript>12</Subscript>O<Subscript>40</Subscript>/SiO<Subscript>2</Subscript> catalysts with superior oxidative desulfurization activity

A series of phosphotungstic acid (HPW)/SiO₂ materials with hierarchical meso/macroporous structure were synthesized by evaporation-induced self-assembly method (EISA), using nonionic surfactant (P123) and polystyrene (PS) spheres as templates. SEM images displayed uniform macropores with an average pore size of 210 nm. TEM, small-angle XRD and N₂ adsorption–desorption isotherms confirmed the existence of the ordered mesoporous structures, embedded in the wall of macropores. The wild-angle XRD and FT-IR spectra proved Keggin-type HPW dispersed homogeneously in the silica framework. With the amount of added PS spheres, the density of the macropores increased, the hierarchically ordered porous HPW/SiO₂ possessed two-dimensional (2D) hexagonal (p6mm) mesostructures and uniform periodic macropores. The ODS catalytic activity of these samples were tested, the result showed that the meso/macroporous HPW/SiO₂ catalyst with proper PS beads usage displayed much higher catalytic activity than other catalysts. In addition, the reusability of the meso/macroporous HPW/SiO₂ catalyst was investigated, the activity of catalyst has not obviously decreased even after eight times.     

Catalytic combustion of volatile aromatic compounds over CuO-CeO<Subscript>2</Subscript> catalyst

Ce_1?x Cu _x O₂ oxide solid solution catalysts with different Ce/Cu mole ratios were synthesized by the one-pot complex method. The prepared Ce_1?x Cu _x O₂ catalysts were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and H₂ temperature-programmed reduction (H₂-TPR). Their catalytic properties were also investigated by catalytic combustion of phenyl volatile organic compounds (PVOCs: benzene, toluene, xylene, and ethylbenzene) in air. XRD analysis confirmed that the CuO species can fully dissolve into the CeO₂ lattice to form CeCu oxide solid solutions. XPS and H²-TPR results indicated that the prepared Ce_1?x Cu _x O₂ catalysts contain abundant reactive oxygen species and superior reducibility. Furthermore, the physicochemical properties of the prepared Ce_1?x Cu _x O₂ catalysts are affected by the Ce/Cu mole ratio. The CeCu₃ catalyst with Ce/Cu mole ratio of 3.0 contains abundant reactive oxygen species and exhibits superior catalytic combustion activity of PVOCs. Moreover, the ignitability of PVOCs is also affected by the respective physicochemical properties. The catalytic combustion conversions of ethylbenzene, xylene, toluene, and benzene are 99%, 98.9%, 94.3%, and 62.8% at 205, 220, 225, and 225 °C, respectively.     

A New <Emphasis Type="Italic">n</Emphasis>-Alkane Hydroisomerization Catalyst Modified with Nanosized Molybdenum Carbides and Its Catalytic Properties in Diesel Fraction Hydroisomerization. Part III: Comparison of the Catalytic Properties of Bifunctional SAPO-31 and SAPO-11 Based Catalysts

Part III of this work continues the study of the catalytic properties of new molybdenum carbide based hydroisomerization catalysts, which are resistant to sulfur compounds and allow the synthesis of waxy diesel fuels with the same quality characteristics as those of platinum-containing catalysts. The catalytic properties of such bifunctional catalysts as 7%Mo₂C/SAPO-31 (LCCH-2) and 7%Mo₂C/SAPO-11 (LCCH-2-2) in diesel fraction hydroisomerization in the temperature range of 320–400°C are compared. It is shown that LCCH-2 ensures a higher yield of the hydroisomerized diesel fraction with a lower freezing point as compared to LCCH-2-2 at temperatures above 320°C. The ratio between mono- and di-isomers in reaction products is analyzed. It is concluded that SAPO-31 based catalyst is more selective to the formation of terminal monosubstituted alkanes than SAPO-11 based catalyst. The resistance of both catalysts to deactivation with coke deposits (tests over 100 h at 320 and 360°C in hydroisomerization) is studied. It is established that LCCH-2-2 is less resistant to deactivation than LCCH-2. These findings are due to differences in acidity, the degree of uniformity in the distribution of acidic hydrogenating/dehydrogenating sites in the catalysts, and the structural type of their acidic supports.     

Single-step polyol synthesis of alloy Pt<Subscript>7</Subscript>Sn<Subscript>3</Subscript> versus bi-phase Pt/SnO<Subscript>x</Subscript> nano-catalysts of controlled size for ethanol electro-oxidation

Disordered alloy and bi-phase PtSn nanoparticles of nominal Pt:Sn ratio of 70:30 atomic % with controlled size and narrow size distribution were synthesized using a single-step polyol method. By adjusting the solution pH it was possible to obtain Pt₇Sn₃ nanoparticles of various sizes from 2.8 to 6.5 nm. We found that the presence of NaOH in the synthesis solution not only influenced the nanoparticle size, but as it was revealed by XRD, it apparently also dictated the degree of Pt and Sn alloying. Three catalysts prepared at lower NaOH concentrations (C_NaOH < 0.15 M) showed disordered alloy structure of the nominal composition, while the other three catalysts synthesized at higher NaOH concentrations (C_NaOH > 0.15 M) consisted of bi-phase nanoparticles comprising a crystalline phase close to that of pure Pt together with an amorphous Sn phase. These observations are plausibly due to the phase separation and formation of monometallic Pt and amorphous SnO_x phases. A proposed reaction mechanism of Pt₇Sn₃ nanoparticle formation is presented to explain these observations along with the catalytic activities measured for the six synthesized carbon-supported Pt₇Sn₃ catalysts. The highest catalytic activity towards ethanol electro-oxidation was found for the carbon-supported bi-phase catalyst that formed the largest Pt (6.5 nm) nanoparticles and SnO_x phase. The second best catalyst was a disordered alloy Pt₇Sn₃ catalyst with the second largest nanoparticle size (5 nm), while catalysts of smaller size (4.5–4.6 nm) but different structure (disordered alloy vs. bi-phase) showed similar catalytic performance inferior to that of the 5 nm disordered alloy Pt₇Sn₃ catalyst. This work demonstrated the importance of producing bi-metallic PtSn catalysts with large Pt surfaces in order to efficiently electro-oxidize ethanol.