Vanadium Pentoxide Catalyst Research Articles

Microstructural and chemical characterization of stabilized spent vanadium pentoxide catalyst in copper smelting slag

The purpose of this research is to perform a microstructural characterization of the stabilized spent vanadium pentoxide (V2O5) catalyst in the copper smelter slag. The spent V2O5 catalyst (SVC) is a discarded material from a sulfuric acid production plant. The used SVC is a catalyst material supported in SiO2. The used copper smelting slag (CSS) was from a copper refining mine. The toxic V2O5 compound present in the SVC was stabilized via pyrometallurgical processing with the CSS in an electric furnace with a CSS/SVC 4:1 ratio at 1250 °C to obtain a fused compound. The microstructural and chemical characterization of the CSS, SVC used materials and the obtained fused compound, were performed by scanning electron microscopy (SEM) coupled and Energy dispersed X-ray analyser (EDS), X-ray powder diffraction (XRD) and Differential Thermal Analyser (DTA-TGA). The fused compound was a complex slag that comprised of Fe2SiO4 and FeVO4 phases.

Impacts of aerosol nuclei on amine emissions

Amine emissions are an environmental and economic concern for CO2 capture by amine scrubbing. Aerosol nuclei, including hydrolyzed SO3 and fly ash, can lead to amine aerosol emissions. Aerosol grows by collecting water and amine while passing through the absorber column; current mitigation techniques are ineffective at capturing the aerosol prior to atmospheric release. This work measures the varying impacts of aerosol nuclei on amine emissions at multiple pilot plants. Aerosol emissions were quantified by the use of Fourier Transform Infrared Spectrometry (FTIR). MEA emissions were measured in the Slipstream Solvent Test Unit (SSTU) at the National Carbon Capture Center (NCCC). The effect of baghouse pretreatment of the inlet flue gas on the aerosol emissions was observed by FTIR and Phase Doppler Interferometry (PDI); these tests were performed before and after the installation of a pulsed-jet baghouse designed for flue gas mercury control. The baghouse resulted in a ten-fold reduction of amine aerosol emissions, due to the collection of SO3 aerosol nuclei, probably on injected Ca(OH)2. This emissions reduction was due to a decrease in the inlet SO3 content from a max of 9 ppm to 0.5 ppm. FTIR sampling was used to quantify this emissions reduction. PDI analysis confirmed the absence of aerosol at diameters greater than 0.1 μm. Aerosol generation was performed through the injection of sulfur trioxide into the process inlet at the University of Texas Separations Research Program (UT-SRP) Pilot Plant. SO3 was generated by the oxidation of sulfur dioxide in air over a heated vanadium pentoxide catalyst bed. The 8% SO2/Air mix was fed at flow rates up to 6 liters per minute, and resulted in up to 110 ppm of SO3 at the absorber inlet. The generator converted an average of 94 % SO2 into SO3, with production rates up to 1.7 grams per minute of SO3. The injected aerosol was allowed to grow within the absorber and water wash. SO3 was found to increase PZ emissions by up to 7.6 mol PZ per mol SO3. Increasing inlet SO3 correlated with increasing PZ emissions.

Innovative Path-Breaking “Cold Process” to Manufacture Sulphonating Agents and Sulphur-Based Chemicals

Manufacture of Sulphuric acid and Sulphonating agents underwent revolutionary change as a result of the inventive contact process using Vanadium Pentoxide catalyst in the 1950’s. The “Single-Contact Single-Absorption” process was widely used until the1970’s. The conversion efficiency of SO2 to SO3 was restricted to 96.5% resulting in stack emissions of 16 to 20 Kgs of Sulphur dioxide per ton of acid produced. Global warming and environmental concern prompted further improvement by introducing DCDA, Double-Contact Double-Absorption process. In the DCDA process the product SO3 was absorbed by introduction of Inter-Pass Absorption Tower (IPAT) keeping V2 O5 contact process unchanged. Thus, the overall conversion efficiency was raised to 99.5-99.7 %, thereby reducing Sulphur dioxide emissions to below 4 Kgs per ton of acid produced. This is today taken as an International Standard as recommended by Environmental Protection Agency of USA. Even so, at the current production level of over 150 million tons of Sulphuric acid per annum, this results into over one million tons of acid rain per year! This acid rain has serious impact on flora and fauna as well as aquatic life. The path-breaking “Cold Process” invented by Navdeep Enviro and Technical Service Pvt. Ltd, Mumbai (India), and for which a patent has been applied at the International Patent Agency in Geneva, is designed to produce Sulphuric acid and Sulphonating agents with zero emission of Sulphur dioxide, which totally eliminates acid rain. This paper outlines the techno economic features of the process, giving cost effectiveness of reduced plant area, lower maintenance costs, and higher cogeneration of steam with lower utility consumption.

Recovery of Vanadium from Acid and Basic Leach Solutions of Spent Vanadium Pentoxide Catalysts

The vanadium pentoxide catalysts are used in the sulfuric acid manufacture, but as an inherent consequence of the process, they are deactivated or poisoned, because of that they need to be renewed. In Ecuador, the increase of environmental pollution concerns and the legislation related with the final dispose of hazardous residues is forcing to companies to process their waste products and residues. For the present investigation, catalysts samples were characterized using AAS (atomic absorption spectroscopy), XRD (X-ray diffraction), surface area (BET) and SEM-EDS (scanning electron microscopy). Results show presence of 6-5% w/w of vanadium pentoxide (V2O5), 10-11% w/w of potassium oxide (K2O) and 55-60% w/w of silicon oxide (SiO2). The material presents a pore size of 3 nm and a specific surface area of 200 m²/s. The spent catalyst was firstly pulverized in a powder mill until 200 µm was attempted, then a calcination at 450 °C was made. Different leaching agents were used: nitric, sulfuric, hydrochloric acid and sodium hydroxide with variation of percentage of solids, particle size, leaching agent concentration and leaching time. Sodium carbonate was added to the solution to obtain a precipitate. A final calcination step was made at 450 °C to obtain vanadium pentoxide. The best results were obtained by using sulfuric acid at 75 g/L, 20 w/w percentage solids, environmental temperature, agitation speed was maintained 750 rpm and 30 minutes leaching, the recovering vanadium rate was 94.41%. In the precipitation stage 92.2% of sodium meta vanadate, for that a pH 7 was required. Finally, precipitation was calcinated getting vanadium pentoxide at 97% purity and it costs is $104.5 per 500 grams.

Characterization of vanadia catalysts on structured micro-fibrous glass supports for selective oxidation of hydrogen sulfide

AbstractThis work is focused on the characterization of a novel vanadium pentoxide catalysts on a glass-fiber support. The catalyst support consists of a non-porous glass-fiber fabric covered with an additional external surface layer of porous secondary support of SiO2. The vanadia active component is synthesized from vanadyl oxalate precursor by means of an impulse surface thermo-synthesis method. Such catalysts demonstrate high activity and appropriate selectivity in the reaction of H2S oxidation by oxygen into sulfur in the practically important temperature range below 200°C. According to the characterization data, the freshly prepared vanadia catalyst partially consists of mostly the amorphous and badly ordered vanadia with some part of the wellcrystallized V2O5 phase. Under the reaction conditions the main part of vanadia in the catalyst remains in the amorphous V2O5 form, while the less part becomes reduces into of VO2 and other vanadium oxides (such as VO, V2O3 V3O7 and V4O9). Most probably, the crystallized V2O5 in course of reaction is responsible for the deep oxidation of hydrogen sulphide into SO2, while the lower vanadium oxides promote the selective H2S oxidation into elemental sulfur.

Vanadium Pentoxide Catalyst over Carbon-Based Nanomaterials for the Oxidative Dehydrogenation of Propane

A series of V2O5 catalysts supported on multiwall carbon nanotube (MWCNT), single wall carbon nanotube (SWCNT), and graphene were synthesized by hydrothermal and reflux methods for oxidative dehydrogenation of propane (ODHP) to propylene. The catalysts were characterized by techniques including the BET surface area measurements, XRD, FTIR, H2-TPR, NH3-TPD, FESEM, and UV–vis diffuse reflectance spectroscopy. The performance of the catalysts and the supports were subsequently examined in a fixed bed reactor. The main products were propylene, ethylene and COx. The vanadium catalyst supported on graphene with C/V molar ratio of 1:1 synthesized through the hydrothermal method had the best performance under the reactor test conditions of 450 °C, feed C3H8/air molar ratio of 0.6, and the total feed flow rate of 90 mL/min resulting in average values of 53.6% and 50.7% for propylene selectivity and propane conversion, respectively. This catalyst was further employed in a series of experiments to study the effects of operating parameters including the reaction temperature, propane to air ratio, and the total feed flow rate on conversions and product selectivities using an experimental design method utilizing the response surface methodology (RSM) with central composite design at three levels. The resulting quadratic equations properly correlated the obtained experimental data. Optimum conditions for maximizing propane conversion and propylene selectivity as well as minimizing the COx selectivity were determined at the temperature of 500 °C, C3H8/air molar ratio of 0.28, and total flow rate of 60 mL/min. Ultimately, results under optimum conditions revealed satisfactory agreement between the experimental and predicted data.

Comparison between the performances of a fluidized-bed reactor and a fixed-bed reactor for the oxidation of benzene to maleic anhydride

The selective oxidation of benzene to maleic anhydride (MAN) was studied to compare the performances of fluidized-bed and fixed-bed reactors. The gas-phase catalytic oxidation of benzene was carried out in laboratory-scale fluidized-bed and fixed-bed reactors with a vanadium pentoxide catalyst supported by silica gel. The influences of parameters such as temperature, space time, and air-to-benzene molar ratio on the reaction selectivity were investigated at normal atmospheric pressure. Similar operating conditions were provided in the experiments carried out in both reactors. Because of the limitations of the experimental sets-up and the recommended operating conditions given in the literature, some differences could be seen between the reactors. It was observed that the conversion of benzene to MAN increased with increasing temperature in both reactors. It was further found that both the conversion of benzene to MAN (x 1 )a nd the total conversion of benzene (x T ) also increased with increasing air-to-benzene molar ratios. This study demonstrates the availability of the 2 reactors for the oxidation reaction of benzene to MAN.

Removal of NOx with Selective Catalytic Reduction Based on Nonthermal Plasma Preoxidation

An extensive series of experiments have been conducted using a nonthermal plasma generated by dielectric barrier discharge (DBD) process combined with vanadium pentoxide catalyst to reduce the nitrogen oxides (NOx) from diesel engine exhaust over a broad reaction temperature (100−500 °C). In this system, the effects of input voltage, propylene (C3H6) concentration, and sulfur content, etc. on the plasma facilitated (PF) selective catalytic reduction of NOx with NH3 were examined. In the presence of C3H6 as an additive, the oxidation of NO to NO2 is largely enhanced even with lower input voltages. The PF NH3−SCR system enhanced the overall reaction and showed a remarkable improvement in NOx removal efficiency at temperatures of 100−250 °C. The removal of NOx was found to be largely increased by the input voltage and the addition of propylene. Besides the small amount of nitrous oxide and the significant amount of carbon monoxide, aldehydes-type unregulated byproduct such as formaldehyde and acetaldehyde were also observed at the outlet of the DBD reactor, while formaldehyde and acetaldehyde could be almost completely removed in the NH3−SCR reactor. The NOx conversion decreases at lower temperatures but increases at higher temperatures with SO2 concentration increases. The PF NH3−SCR hybrid system can be used stably with several hundreds of ppm of SO2 in durability tests. Moreover, the presence of SO2 inhibits N2O formation at all employed reaction temperatures.

Tmperature programmed techniques study on the nature of the oxidant in/on V2O5catalyst

The nature of the oxidising species in/on a vanadium pentoxide (V2O5) catalyst has been studied using a combination of transient techniques: (i) Temperature programmed desorption (TPD), (ii) Temperature programmed reduction (TPR), (iii) Temperature programmed oxidation (TPO) and (iv) Temperature programmed reaction (TPRn). Chemisorbed oxygen was found not to exist on a fully oxidised V2O5 catalyst by TPD. The TPR in CO over V2O5 catalyst gave three peak maxima at 930, 982 and 1043 K, indicating that three types of kinetically different oxygen states exist in/on the catalyst. Reoxidation of the CO reduced V2O5 catalyst by N2O resulted in the quantitative replacement of the lattice oxygen. A further reduction of the N2O reoxidised catalyst gave a significantly different TPR profile compared to the original material suggesting that a less crystalline material had formed. The presence of phosphorus in (VO)2P2O7 was found to labilise the lattice oxygen.

Trickle‐bed scrubbing of flue gas SO2 using non‐aqueous solvents

AbstractExperiments were carried out on the performance of several ketone solvents for the scrubbing of dilute SO2 from a gas stream and its conversion to sulfuric acid in a trickle‐bed reactor packed with activated carbon. Using a bench‐scale trickle bed packed with a structured packing based on Sulzer static mixers coated with CentaurTM activated carbon and a Teflon binder, measurements of SO2 removal, conversion to acid and catalyst productivity showed that all were considerably greater than levels achieved with water flushing. The combination of Teflon‐coated Centaur activated carbon with a non‐aqueous solvent as the flushing agent provided from 10 to 100 times higher catalyst productivity than those obtained with water alone and other activated carbons. Also, the productivities obtained by this combination were up to 40 times higher than the productivity of typical vanadium pentoxide catalyst operating at 350°C to 400°C.

The preparation of D‐glucaric acid by oxidation of molasses in packed beds

AbstractAn attempt has been made to prepare glucaric acid by oxidation of sugar beet molasses in packed beds. In the first part, a suitable oxidizing medium was sought. Experiments were performed in a cylindrical Pyrex‐glass reactor with air–molasses cocurrent downflow. Spherical glass and cylindrical vanadium pentoxide particles were used as an inert packing and catalyst respectively. The addition of catalyst, sodium nitrite, nitric and sulfuric acids to the medium resulted in an improvement in glucaric acid yield. The presence of nitric acid in the oxidizing medium and the use of vanadium pentoxide catalyst were the most effective factors as regards the yield. In the second part, the effects of temperature, molasses concentration, amount of catalyst and air flow rate on the yield were studied; each of these variables increased the yield. The use of a longer catalyst bed, however, resulted in a decrease in the yield. The highest rate of conversion of glucose to glucaric acid was 63.9% at optimum conditions.© 2001 Society of Chemical Industry

Obtaining benzaldehyde via promoted V 2O 5 catalysts

Catalytic activity was measured for the partial oxidation of toluene to benzaldehyde on potassium-promoted vanadium pentoxide catalysts. In addition, the surface acidity of these solids was inferred from the 2-propanol decomposition reaction, which gives an indication of the acid strength. The results of this work showed that both toluene conversion and selectivity to benzaldehyde are related to the presence of acidic sites in the catalyst.

Active Sites of V2O5/γ-Al2O3Catalysts in the Oxidative Dehydrogenation of Ethane

The oxidative dehydrogenation (ODH) of ethane to ethylene was studied on V2O5/γ-Al2O3catalysts (1–20 wt% V2O5). The reducibility of the catalysts by hydrogen, ethane, and ethylene and their reoxidation by oxygen were determined by thermogravimetry linked to differential scanning calorimetry and by a pulse catalytic test linked to a microcalorimeter. Ammonia and sulphur dioxide microcalorimetry adsorptions were carried out on all catalysts to characterize their acid–base properties. In ethane ODH reaction at the steady state at 823 K, 60% ethylene selectivity was obtained at 28% ethane conversion. The improved catalytic properties for such reaction on vanadia/γ-alumina catalysts compared to vanadia/silica and bulk vanadium pentoxide catalysts appear to be related in the first place to the dispersion and coordination degree of the vanadium cations of the active sites, and in the second to the development of their acidic properties. The active sites are suggested to be oxidized vanadate dimers composed of tetrahedrally coordinated and oxygen-bridged vanadium cations operating according to a redox mechanism involving very probably transient radicals generated via one-electron transfer. Such dimers undergo a relatively high rate of reduction by ethane. The population of vanadate dimers was estimated in the case of the sample with 20 wt% V2O5loading. The number and strength of active sites are described. More than silica, γ-alumina induces the dispersion of such active sites for ethane ODH.

Promotion Effects of Titanium on Partial Oxidation of Methanol over Vanadium Pentoxide Catalysts

This article reports studies on the catalytic activity of V2O5coprecipitated with different TiO2concentrations, and on the chemical characterization of the fresh and used catalysts by the following methods of chemical analyses: EDAX, XRD, FTIR, SEM, BET, TPR, and XPS. Catalytic tests were performed under integral and differential conditions. In the former (integral) series of experiments, formaldehyde, methyl formate, methylal, and CO were obtained as major products of methanol partial oxidation. A minor production of CO2and dimethyl ether was noticed as well. Under the latter (differential) conditions, the results led to the notion of catalytic activity (reaction rate) dependence on the surface concentration of vanadium. From calculation of the turnover frequencies, it was concluded that both the catalytic activity and the HCHO production decrease with stronger V=O bonds. In turn, the reactivity of those species was influenced by addition of TiO2.

TPSR, TPR, and TPO Studies of Pd-V2O5/Al2O3 Catalysts in Complete Catalytic Oxidation of Benzene

Alumina-supported palladium vanadium-pentoxide catalysts were studied by means of temperature-programmed surface reaction, temperature-programmed reduction, temperature-programmed oxidation, and by ESR spectroscopy in the complete oxidation of benzene. The surface reaction measurements indicated that 0.5% Pd - 30% V2O5 / Al2O3 produced most oxidation products, compared to 0.5% Pd / Al2O3 or 30% V2O5 / Al2O3 samples. A drastic fall of peak maxima in temperature-programmed oxidation and reduction spectra indicates the decisive role of palladium in the mixed metal metal oxide system in facilitating the vanadium redox transitions. During initial period of catalysts operation, there proceeds formation of vanadium oxide phases which contain clustered V4+ ions in a matrix of vanadium pentoxide. These ions are responsible for the high activity of the palladium vanadium pentoxide catalyst.

Influence of the Formation of Aluminium Spinel, AlVO4, on the Catalytic Activity of V2O5 Supported on γ-Alumina

Vanadium pentoxide catalysts supported on γ-alumina (1 - 50 mole %) were prepared by impregnation method and calcined at 400 and 680 °C for 4 h. The structure of the original and calcined samples was characterized by DTA and X-ray diffraction. The electrical conductivity measurements of the calcined samples reveal that the conductance increases while the Fermi potential decreases on increasing V2O5 content up to 50 mole %. The catalytic dehydration of isopropanol was carried out at 250 °C using a flow system. The results showed an observable increase in the extent of catalytic dehydration of the alcohol on increasing V2O5 content from 5 mole % to 50 mole % with the samples calcined at 400 °C. The catalysts calcined at 680 °C were found to exhibit maximum activity at the composition of 20 mole % V2O5. Above the maximum a sharp decrease in the conversion and the yield towards propylene was found due to formation of aluminium vanadate, i.e. AlVO4 spinel. The low activity associated with the existence of this spinel was correlated with the sharp decrease in the Fermi potential.

Role of Ammonia Oxidation in Selective Catalytic Reduction of Nitric Oxide over Vanadia Catalysts

The role of direct oxidation of ammonia in SCR reactions and the catalytic anisotropy of V2O5 catalysts in this reaction network were investigated. The catalysts were characterized using BET surface area measurement, X-ray diffraction, laser Raman spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, and 3-D imaging. Temperature-programmed reduction experiments using ammonia and hydrogen as reducing agents and temperature-programmed desorption studies were also performed. A steady-state fixed-bed reactor system was used for activity and selectivity measurements. The product analysis was carried out by a combination of techniques including chemiluminescence NOx analysis, on-line gas chromatography and on-line mass spectrometry, and chemical titration methods. The results obtained in this study, when combined with our previous studies in SCR reactions, indicate that over vanadium pentoxide catalysts, ammonia oxidation and NO reduction reactions are closely coupled. The results suggest that ammonia adsorption takes place on at least two types of sites located on the (010) and (100) planes of V2O5. The sites that selectively reduce NO to N2 are the VOV sites located on the side planes, whereas VO sites promote direct oxidation of ammonia to NO and the formation of N2O from NO and NH3 interaction more readily. It is found that the VO sites are more easily reduced with both hydrogen and ammonia.

Effect of crystal morphology in selective catalytic reduction of nitric oxide over V 2O 5 catalysts

Structural specificity of vanadium pentoxide catalysts was investigated in the selective catalytic reduction (SCR) of nitric oxide. Catalysts were prepared by different temperature-programmed methods to obtain particles having preferential exposure of different crystal planes. Catalyst samples were characterized using the BET surface area technique, X-ray diffraction, laser Raman spectroscopy. X-ray photoelectron spectroscopy, scanning electron microscopy and 3-D imaging techniques. A steady-state fixed-bed reactor system was used for activity and selectivity measurements. Identification and quantification of reaction effluents were achieved using an analytical scheme that combined gas chromatography, chemiluminescence, gas chromatography-mass spectroscopy and wet chemistry techniques. Samples that preferentially exposed the (010) basal planes were found to promote direct oxidation of ammonia more readily than nitric oxide reduction as evidenced by the differences in nitric oxide and ammonia conversions and in nitrogen and nitrous oxide yields. The difference in catalytic activity and selectivity was related to the relative abundance of V O sites exposed on the catalyst surface and the competing reactions that are involved in SCR and direct ammonia oxidation reaction schemes.

Ammoxidation of cyclohexanol to adiponitrile on vanadium oxide

The reaction pathway of ammoxidation of cyclohexanol to adiponitrile (ADN) on vanadium pentoxide catalyst has been investigated. ADN was produced directly via adipic acid obtained from oxidation of cyclohexanone. The main end-products were carbon dioxide and benzene.

Calorimetric study of vanadium pentoxide catalysts used in the reaction of ethane oxidative dehydrogenation

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTCalorimetric study of vanadium pentoxide catalysts used in the reaction of ethane oxidative dehydrogenationJ. Le Bars, J. C. Vedrine, A. Auroux, B. Pommier, and G. M. PajonkCite this: J. Phys. Chem. 1992, 96, 5, 2217–2221Publication Date (Print):March 1, 1992Publication History Published online1 May 2002Published inissue 1 March 1992https://doi.org/10.1021/j100184a035RIGHTS & PERMISSIONSArticle Views284Altmetric-Citations45LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (623 KB) Get e-Alerts