Reaction Of Isopropanol Research Articles

Development of soft x-ray absorption spectroscopy technique with simultaneous measurement in electron- and fluorescence-yield modes from high vacuum to ambient pressure for observation of surface adsorbed species

To understand the reactions of heterogeneous catalysts at the solid–gas interface under actual reaction conditions, it is important to develop a method to observe the surface-adsorbed species during the reaction, including the changes before and after the adsorption of light elements involved in the surface reaction. We developed a soft x-ray absorption spectroscopy (XAS) technique that allows simultaneous measurements in the electron- and fluorescence-yield modes in the pressure range of 10−4–1 × 105 Pa. In the developed system, the reaction gas near the sample surface is separated from the beamline vacuum by a Si3N4 window and confined to a small area to suppress x-ray absorption by the gas. The electron-yield spectra were obtained by measuring the sample current while applying a bias potential to the Si3N4 window. XAS measurements were performed from high vacuum to ambient pressure by setting the bias potential to 600 and 39 V below and above 100 Pa, respectively. An anatase TiO2 nanoparticle-deposited film was prepared by spin coating, and soft XAS was performed to observe the photocatalytic oxidative decomposition reactions of isopropanol in the presence of water and oxygen. The obtained O K-edge spectra showed that it is possible to observe adsorbed oxygen on solid oxides even under ambient pressure conditions containing 0.1% of oxygen gas.

SrTiO3 catalysts prepared from topochemical conversion of Bi4Ti3O12 nanoplatelets: Surface characterizations and interactions with isopropanol

The heterostructural Bi4Ti3O12-SrTiO3 (or BIT-STO) platelets with various STO contents (i.e., 40, 65, and 100%) were synthesized by the topochemical conversion of well-defined BIT platelets via the alkaline hydrothermal treatment. The surface properties of synthesized BIT-STO platelets were characterized, and probed by the temperature-programmed surface reaction of isopropanol (IPA). It is found that all BIT-STO catalysts are highly selective in IPA dehydrogenation (to yield acetone) as opposed to IPA dehydration (to yield propene). With the increase in STO content, the desorption temperature of acetone from the BIT-STO surface gradually decreases, suggestive of an improved IPA dehydrogenation activity. The BIT-derived STO exhibits much higher activity and selectivity in IPA dehydrogenation in comparison to the hydrothermally-synthesized STO and commercial STO, which is attributed to the desirable (100) facet with abundant surface defects formed during the topochemical conversion. In-situ infrared spectroscopy indicates that upon IPA adsorption, the BIT-derived STO shows a higher proportion of bridged isopropoxide (IPO) presents on the surface than the reference STO samples. It is proposed that the abundant oxygen vacancies present on the surface of BIT-derived STO could facilitate the bridged adsorption of IPO intermediate that favors further decomposition into acetone, thus promoting the selective IPA dehydrogenation.

A Brief Review on Key Role of Perovskite Oxides as Catalyst

AbstractThe research work conducted mainly on the reduction reaction of NOx, the oxidation reaction of CO, and hydrocarbons, electro‐catalysis of oxygen in alkaline medium, and photocatalytic water splitting has proved excellent catalytic behavior of perovskite oxides.[16–23] Although only a few reports published usages of the perovskite oxides as catalysts for the organic transformation such as catalytic hydrogenation, Ullmann, Sonogashira reactions, and Suzuki couplings.[24–26] Yoon et al. have prepared K2CO3 based LaMn1‐xCuxO3 perovskite oxide as a potential catalyst and discussed their mechanistic aspects in various reactions occurring at room temperature.[27] Recently, Wu and Ajayan group has demonstrated the relationship between stoichiometry and activity of pure and B‐site substituted layered perovskite oxide in the decomposition reaction of isopropanol by considering Sr2Sn1‐xRuxO4 (0≤x≤1) as catalyst.[28] In this scenario, present work aims to summarize the contribution of perovskite oxides as catalyst in numerous organic syntheses and catalysis, photocatalysis, and electrocatalysis reactions.

Selective cleavage of lignin-derived diphenyl ether C-O bond over weakly acidic Ni/Nb2O5 catalyst

Selective cleavage of stable ether C-O bonds is particularly of significance for the valorization of lignin and designing high active and cheap catalysts attracts researchers to conduct a lot of investigations. The niobium species containing both Brønsted and Lewis acid sites can be applied in hydrodeoxygenation of diphenyl ether (DPE). It is important to regulate the acidity of niobium to achieve the selective cleavage of DPE without hydrodeoxygenation. Herein, the weakly acidic Ni/Nb2O5 prepared by an incipient wetness impregnation method could efficiently cleave C-O bonds of DPE without hydrodeoxygenation. DPE was completely converted and the yields of target products (cyclohexane and cyclohexanol) reached 90% under the coexistence of H2 and isopropanol. It was ascribed to the common hydrogen supply between H2 and isopropanol which could produce more active hydrogen. Acetone was detected in the solution after the reaction, demonstrating that a dehydrogenation reaction of isopropanol provided hydrogen. In addition, the turnover frequency (TOF) and the apparent activation energy (Ea) for catalytic hydrogenolysis of DPE revealed that Ni/Nb2O5 possessed higher activity than Co/Nb2O5 under the same conditions. The possible reaction pathways were also summarized and analyzed.

1,3-Butadiene production from aqueous ethanol over ZnO/MgO-SiO2 catalysts: Insight into H2O effect on catalytic performance

A series of ZnO/MgO-SiO2 systems have been prepared and characterized by one-pass temperature-programmed desorption of CO2, NH3 and H2O, FTIR spectroscopy with adsorbed pyridine and CO2, temperature programmed surface reaction of ethanol and isopropanol, and reaction of isopropanol conversion. Effect of MgO:SiO2 ratio in the catalysts on catalytic performance in 1,3-butadiene production from aqueous ethanol have been investigated. The results indicate that hydrophilicity of ZnO/MgO-SiO2 are determined by MgO:SiO2 ratio, and chemisorption of water occurs preferably on Mg-containing sites. The presence of water in the initial ethanol leads to a decrease in formation of the CC coupling products. The hydrated sites formed in the interface of magnesia and silica remain active in the CC coupling reaction even in the presence of water. 1,3-Butadiene selectivity >60 % in the conversion of aqueous ethanol (80 vol%) is achieved in the presence of ZnO/MgO-SiO2 catalysts with the ratio of MgO:SiO2 = (1:1) and (3:1).

Total Oxidation of Isopropanol in Its Liquid Phase, at a Low Temperature in the Presence of Prepared and Characterized Zinc Oxide

The complete oxidation of isopropanol in its liquid phase at a low temperature was studied in the presence of zinc oxide (ZnO). This solid was prepared with the precipitation method. Structural analysis (infrared in Fourier transform and diffraction of X-rays) and textured (adsorption/desorption of N2) were conducted for the wurtzite structure results, an IV type isotherm with a type H3 hysteresis. This solid presents a good catalytic activity against the complete oxidation of isopropanol, a constant of selectivity equal to 1; however, the studied temperatures were 40, 60, and 80°C. In addition, a kinetic study of the oxidation was performed and showed that the reaction follows a successive mechanism isopropanol-acetone-carbon dioxide. The low value of the apparent energy of the activation of this solid confirms the high value of the initial rate of the catalytic oxidation reaction of isopropanol in the temperature range studied.

Synthesis and characterization of vanadium pentoxide on different metal oxides by the sol-gel process for application in the conversion of the SO2 to SO3

Sulfuric acid is the largest volume chemical currently produced in the world. Is manufactured by the contact process, it involves three stages: combustion, conversion and absorption. The SO 2 conversion reaction is the key step in the process, it uses catalysis. The objective of this work is to synthesize a series of mixed vanadium oxides X% / MO 2 with M (Si, Al and Ti) by sol-gel process followed by calcination at 400 ° C, in order to study their reactivity in the catalytic oxidation of SO 2 to SO 3 . Characterization of those materials was carried out by Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM) with energy dispersive X-ray (EDX), X-ray diffraction, thermal analysis (TDA/TGA) and N 2 adsorption at 77 K. Their acid-base properties are studied by the decomposition reaction of isopropanol (propan-2-ol). In this work, we have studied the reactivity of the catalysts prepared in the conversion of SO 2 to SO 3 by an iodometric as dosage which consists in assaying the iode with sodium thiosulfate.

Production of renewable fuels by blending bio-oil with alcohols and upgrading under supercritical conditions

The work studied a non-catalytic upgrading of fast pyrolysis bio-oil by blending under supercritical conditions using methanol, ethanol and isopropanol as solvent and hydrogen donor. Characterisation of the bio-oil and the upgraded bio-oils was carried out including moisture content, elemental content, pH, heating value, gas chromatography-mass spectrometry (GCMS), Fourier transform infrared radiation, 13C nuclear magnetic resonance spectroscopy, and thermogravimetric analysis to evaluate the effects of blending and supercritical reactions. The GCMS analysis indicated that the supercritical methanol reaction removed the acids in the bio-oil consequently the pH increased from 2.39 in the crude bio-oil to 4.04 after the supercritical methanol reaction. The ester contents increased by 87.49% after the supercritical methanol reaction indicating ester formation could be the major deacidification mechanism for reducing the acidity of the bio-oil and improving its pH value. Simply blending crude bio-oil with isopropanol was effective in increasing the C and H content, reducing the O content and increasing the heating value to 27.55 from 17.51 MJ·kg−1 in the crude bio-oil. After the supercritical isopropanol reaction, the heating value of the liquid product slightly further increased to 28.85 MJ·kg−1.

Green synthesis of bio‐ethyl acetate over Egyptian natural red clay as a highly active, selective, and eco‐friendly catalyst

AbstractThe present work focused on the utilization of Egyptian red clay (ERC) without any treatment as a highly efficient, selective, and eco‐friendly catalyst for synthesis of bio‐ethyl acetate in the gas phase. The best conditions used in conventional fixed bed reactor were 130 cm3/min total flow rate of air with 1.6 and 2.1 vol% bio‐ethanol and bio‐acetic acid, respectively, 1 g clay catalyst calcined at 300 and 225°C reaction temperature. Under these conditions, the conversions to ester achieved were about 80 and 98% after 5 and 30 min, respectively, from the initial admission of the reactants into the reactor. The amount and type of surface acidity were identified by isopropanol reaction and chemisorption of basic probes. The results demonstrated that the majority of intermediate strength of BrØnsted acid sites are the key role for the dehydration reaction toward ester formation. The virgin and annealed clay solids were characterized using X‐ray fluorescence (XRF), thermogravimetry (TG) and differential thermal analysis (DTA), Fourier transform infrared (FTIR), X‐ray diffraction (XRD), and N2 sorption.

Enzymatic characterization of a recombinant carbonyl reductase from Acetobacter sp. CCTCC M209061

BackgroundAcetobacter sp. CCTCC M209061 could catalyze carbonyl compounds to chiral alcohols following anti-Prelog rule with excellent enantioselectivity. Therefore, the enzymatic characterization of carbonyl reductase (CR) from Acetobacter sp. CCTCC M209061 needs to be investigated.ResultsA CR from Acetobacter sp. CCTCC M209061 (AcCR) was cloned and expressed in E. coli. AcCR was purified and characterized, finding that AcCR as a dual coenzyme-dependent short-chain dehydrogenase/reductase (SDR) was more preferred to NADH for biocatalytic reactions. The AcCR was activated and stable when the temperature was under 35 °C and the pH range was from 6.0 to 8.0 for the reduction of 4′-chloroacetophenone with NADH as coenzyme, and the optimal temperature and pH were 45 °C and 8.5, respectively, for the oxidation reaction of isopropanol with NAD+. The enzyme showed moderate thermostability with half-lives of 25.75 h at 35 °C and 13.93 h at 45 °C, respectively. Moreover, the AcCR has broad substrate specificity to a range of ketones and ketoesters, and could catalyze to produce chiral alcohol with e.e. >99% for the majority of tested substrates following the anti-Prelog rule.ConclusionsThe recombinant AcCR exhibited excellent enantioselectivity, broad substrate spectrum, and highly stereoselective anti-Prelog reduction of prochiral ketones. These results suggest that AcCR is a powerful catalyst for the production of anti-Prelog alcohols.Graphical abstractThe biocatalytic reactions conducted with the recombinant AcCR

Highly porous TiO2 hollow microspheres constructed by radially oriented nanorods chains for high capacity, high rate and long cycle capability lithium battery

Hierarchical nanorods chains-constructed TiO2 hollow microspheres (HNC-TiO2-HMSs) have been designed and prepared through a facile one-pot fluorine-free solvothermal alcoholysis route using TiCl4 and isopropanol reaction system. Owing to the assembly of radially oriented nanorods chains leading to the formation of the shell of the hollow spheres, a large series of straight channels along nanorods chains are formed. Such highly porous hollow microspheres with hollow cavity, straight nanorods chains and straight nanochannels are highly desirable for Li ions batteries because such structure can easily store the electrolyte, facilitate the charge diffusion and Li+ insertion and buffer the volume change during the Li+ insertion/extraction process. One of the key innovation of the present work is the fine tuning of water amount released from the esterification of alcohol to induce in a well controlled hydrolysis of TiCl4 and engineer precisely HNC-TiO2-HMSs formation. Most importantly, the released Cl− ions direct the nanorods growing along (001) crystal plane and self-assembling along the radial direction accompanying with nanorods size controlling to form HNC-TiO2-HMSs. The obtained TiO2 anode material with such special structure demonstrates excellent Li+ storage capacity with outstanding cycle performance and superior rate capability at different rates over 700 cycles: a reversible capacity of 216mAhg−1 is obtained after 100 cycles at 1C and a reversible capacity of 112mAhg−1 is retained after 100 cycles at 10C. The SEM, TEM, HRTEM and in-situ XRD techniques have been utilized to shed light on the Li+ insertion process and the phase transformation. Most importantly, a self-improving phenomenon of cycle performance and storage capacity was observed owing to the formation of numerous ~5nm Li2Ti2O4 nanocrystals formed on the surface of the nanorods chains. The results reveal that the high performance of the as-prepared HNC-TiO2-HMSs in terms of storage capacity, cycle performance and rate capability can be attributed to the synergy of the special structure and the self-improving phenomenon. Our simple reaction system may provide a concrete example on the construction of novel hollow spherical porous anode materials for high performance lithium batteries.

Effect of the plasma-chemical treatment of ZnO and NiO on their activity in the dehydrogenation of isopropanol

Treating ZnO and NiO oxides with glow discharge oxygen plasma and high-frequency argon plasma is found to affect the catalytic activity of these oxides in the dehydrogenation reaction of isopropanol, leading to an increase in the conversion of alcohol and the yield of acetone. The increased activity of ZnO is due to the high number of acid sites induced by plasma-chemical treatment. With NiO, the increased activity results from the formation of new, more active sites with low experimental activation energy, rather than a change in the surface acidity.

Tailoring acid–metal functions in molybdenum oxides: Catalytic and XPS-UPS, ISS characterization study

Formation of acid, metal and metal–acid (bifunctional) functions in titania-supported molybdena following controlled partial reduction of MoO3 using hydrogen at different temperatures are monitored by a combination of surface XPS-UPS, ISS techniques. Addition of controlled amount of sodium or potassium alkali metals to the bifunctional MoO2−x(OH)y/TiO2 (MoTi) enabled to neutralize the Brønsted acid Mo-OH functions. Sodium or potassium molybdenum bronze metallic function is formed following the addition of the alkali metal to the Mo salt following its calcination at 773K. The catalytic functions of these MoTi and Na, KMoTi systems were evaluated for the dehydration/hydrogenation, oxidation reactions of isopropanol to acetone as well as the ring shortening of cyclohexane to methylcyclopentane MCP and its oxidative dehydrogenation to benzene.

Experimental study of isopropanol dehydrogenation over amorphous alloy raney nickel catalysts

The dehydrogenation reaction of isopropanol occurring at low temperature is of great industrial importance. It is a key procedure in isopropanol/acetone/hydrogen chemical heat pump system. An experimental investigation was performed to study the behavior of the liquid phase dehydrogenation of isopropanol over amorphous alloy Raney nickel catalysts. Un-promoted and promoted catalysts were used and their performances were compared under various catalyst amounts, acetone content in the reactant and reaction temperature ranging from 348 K to 355 K. It is found that there exists an optimum catalyst concentration which is about 0.34 g in 300 ml isopropanol. The temperature has evident effect on the reaction. The presence of activities of Fe-promoted catalyst decrease slightly compared to the un-promoted catalyst when the temperature are 348 K and 351 K. Besides, the reaction rate decreases almost linearly with the increase of acetone volume fraction in the reactant.

Hydrothermal synthesis and acidity characterization of TiO2 polymorphs

The goal of this study was to improve the understanding of key parameters determining the surface acidity of titanium dioxide. For this sake, pure phases of nanocrystalline anatase, rutile and brookite were prepared from the same hydrous titania precursor using hydrothermal treatment at variable pH. Nanoparticles of the three different phases have well defined shape and expose low index crystallographic planes.The solids were characterized by several physical techniques and their acidity was compared using IR spectroscopy of adsorbed pyridine, Zeta-potential measurements and catalytic activity in the model reaction of isopropanol (IPA) decomposition.Significant differences of acidity between the three polymorphs were observed. The specific activity in IPA decomposition changed in the sequence: brookite>anatase≥rutile. Compensation effect was clearly observed relating the activation energy and pre-exponential factor in the rate equation. From the IR spectra of adsorbed pyridine, Lewis and Bronsted acidity were estimated separately and found to be in agreement with the results of catalytic tests. Stronger Lewis centers are present on anatase and rutile surfaces whereas brookite shows more pronounced Brönsted acidity. Zeta-potential measurements showed that point of zero charge (PZC) values change in the sequence: rutile>anatase>brookite, consistently with the catalytic tests and IR spectra. However the variations of acidity between different preparations of the same phase were sometimes comparable to the variations between three polymorphs. A qualitative explanation of the observed behavior has been proposed.

Decomposition of Epoxy Resin in Supercritical Isopropanol

This paper reports the decomposition of an amine-cured bisphenol A diglycidyl ether (DGEBA) epoxy resin in supercritical isopropanol in a flow reactor with and without potassium hydroxide (KOH). The decomposition process was monitored by the change of the refractive index of the exit solution with time. The product distribution was analyzed using gas chromatography−mass spectroscopy (GC-MS) and compared with those obtained from the decomposition in supercritical 1-butanol and pyrolysis processes. This study indicated that thermolysis played a key role in cleaving the chemical bonds of the epoxy resin, and that supercritical isopropanol reduced char formation, because of the rapid removal of the primary decomposition products from the reaction zone to lessen secondary reactions. KOH reduced the initial decomposition temperature of the epoxy resin, but it also promoted the Guerbet reaction of isopropanol to form complex alcohols.

The influence of the preparation method on the structural, acidic and redox properties of V2O5-TiO2/SO42− catalysts

V 2 O 5 -TiO 2 /SO 4 2− catalysts were prepared by different methods and calcined at different temperatures. Co-precipitation was by far the best preparation method. The reaction of isopropanol conversion in air was used to probe the strength of surface acidic sites and redox properties. The surface acidic properties were enhanced and the redox properties weakened upon addition of SO 4 2− species. The introduction of sulfates into vanadia-titania catalysts and the influence of the preparation method on the properties of the sulfated samples have been studied. Series of V 2 O 5 -TiO 2 /SO 4 2− (VTiS) catalysts were prepared by co-precipitation, sol–gel and mechanical grinding methods and calcined at different temperatures. Their structural properties were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS). Co-precipitation was by far the best preparation method in terms of maximizing the surface area and the mesoporosity. Temperature-programmed reduction (TPR) revealed that only the vanadia species were reducible. The results from XRD and FT-IR showed that V 2 O 5 was well dispersed on the surface of TiO 2 . XPS showed that the surface vanadium oxide was composed of stoichiometric V 2 O 4 and V 2 O 5 , as well as V 2 O 3 species especially for the samples prepared by mechanical grinding. Meanwhile, titanium was present in its fully oxidized state in all the VTiS samples, and the sulfur-containing species presented an oxidation state of +6. The reaction of isopropanol (IPA) conversion in air was used to characterize the surface acid/base and redox properties. The higher activity for the IPA conversion over the VTiS catalysts as compared to TiO 2 was possibly due to the generation of redox sites upon the addition of V 2 O 5 . Moreover, the surface acidic properties were enhanced and the redox properties weakened upon addition of SO 4 2− species.

Synthesis and characterization of tungstophosphoric acid intercalated Ni/Al HTlc with magnetite

Tungstophosphoric acid (TPA) was intercalated in magnetic nickel aluminium hydrotalcite-like compounds (NAH) by direct intercalation via ion exchange method and the materials were characterized by TG–DSC, XRD, FT-IR, TEM, SEM, Raman and VSM techniques. XRD results revealed intercalation of TPA species, which is further corroborated by the presence of these Keggin ions by FT-IR and Raman. TG–DSC results indicated that higher thermal stability of the obtained materials was related to the presence of Keggin ions in the NAH. The catalytic activity of the prepared catalysts was tested for the isopropanol reaction. The effect of reaction temperature on the conversion and selectivity of TPA-NAH was studied and the findings are discussed. The samples synthesized at 180 °C showed highest catalytic activity in isopropanol reaction.

Surface acidic and redox properties of V-Ag-Ni-O catalysts for the selective oxidation of toluene to benzaldehyde

Abstract V-Ag-O and V-Ag-Ni-O complex oxides were found to exhibit good catalytic reactivity for the selective oxidation of toluene to benzaldehyde. In order to understand the effects of each metal in the two catalysts, a series of single and complex oxides were prepared including V 2 O 5 , Ag 2 O, NiO, V-Ni-O, Ag-Ni-O, V-Ag-O and V-Ag-Ni-O with the previously optimized compositions for the binary and tertiary oxides. Data from the X-ray diffraction (XRD), infrared spectroscopy and laser Raman spectroscopy showed the formation of complex oxides with phases of silver and nickel vanadates as well as the broadening and red shift of the band of V O bonds, suggesting the formation of V O Ag and V O Ni bonds and the increased redox ability of vanadium species. The results from temperature programmed reduction (TPR) and the combined technique of TPR-XRD revealed that the addition of Ag and Ni promoted the reduction of vanadium species in the complex catalysts. Microcalorimetric adsorption of ammonia and the probe reaction of isopropanol in air demonstrated that the surface acidity was greatly decreased while the redox cycles of vanadium sites were significantly enhanced upon the addition of Ag and Ni. The reactivity for the selective oxidation of toluene was evaluated by using a fixed-bed microreactor, and was correlated with the surface acidity and redox property of the catalysts. Silver seemed to be a special promoter that not only decreased the surface acidity but also enhanced the redox cycles of vanadium sites, leading to the increased conversion of toluene and the selectivity to benzaldehyde. Such effect was even more pronounced when Ag and Ni were added simultaneously. Accordingly, the V-Ag-Ni-O catalyst studied in this work exhibited excellent performance for the selective oxidation of toluene to benzaldehyde. The conversion of toluene was found to be 8% with 95% selectivity to benzaldehyde on the V-Ag-Ni-O at 613 K.

Grafting sulfated zirconia on mesoporous silica

Recently, sulfated zirconia has received considerable attention as a potential solid acid catalyst to replace problematic homogeneous acid catalysts. In this paper, the preparation and properties of acid catalysts obtained by grafting ziconia with atomic precision on MCM-41 mesoporous silica were studied. TEM and potential titration characterizations revealed that ZrO2/MCM-41 with monolayer coverage can be obtained using this grafting technique. Sulfated ZrO2/MCM-41 exhibits improved thermal stability than that of bulk sulfated zirconia, as evidenced by temperature programmed characterizations and XRD analysis. Temperature programmed reaction of isopropanol was used to evaluate the acidity of sulfated ZrO2/MCM-41. It was found that the acid strength of sulfated ZrO2/MCM-41 with monolayer coverage is weaker than bulk sulfated zirconia but stronger than SiO2–Al2O3, a common strong acid catalyst.