Regeneration of Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>-based high-temperature coal gas desulfurization sorbent in atmosphere with sulfur dioxide

Regeneration of a high-temperature coal gas desulfurization sorbent is a key technology in its industrial applications. A Fe₂O₃-based high-temperature coal gas desulfurizer was prepared using red mud from steel factory. The influences of regeneration temperature, space velocity and regeneration gas concentration in SO₂ atmosphere on regeneration performances of the desulfurization sorbent were tested in a fixed bed reactor. The changes of phase and the composition of the Fe₂O₃-based high-temperature coal gas desulfurization sorbent before and after regeneration were examined by X-ray diffraction (XRD) and X-ray Photoelectron spectroscopy(XPS), and the changes of pore structure were characterized by the mercury intrusion method. The results show that the major products are Fe₃O₄ and elemental sulfur; the influences of regeneration temperature, space velocity and SO₂ concentration in inlet on regeneration performances and the changes of pore structure of the desulfurization sorbent before and after regeneration are visible. The desulfurization sorbent cannot be regenerated at 500°C in SO₂ atmosphere. Within the range of 600°C–800°C, the time of regeneration becomes shorter, and the regeneration conversion increases as the temperature rises. The time of regeneration also becomes shorter, and the elemental sulfur content of tail gas increases as the SO₂ concentration in inlet is increased. The increase in space velocity enhances the reactive course; the best VSP is 6000 h^?1 for regeneration conversion. At 800°C, 20 vol-% SO₂ and 6000 h^?1, the regeneration conversion can reach nearly to 90%.     

Regeneration of Fe2O3-based high-temperature coal gas desulfurization sorbent in atmosphere with sulfur dioxide

Regeneration of a high-temperature coal gas desulfurization sorbent is a key technology in its industrial applications. A Fe₂O₃-based high-temperature coal gas desulfurizer was prepared using red mud from steel factory. The influences of regeneration temperature, space velocity and regeneration gas concentration in SO₂ atmosphere on regeneration performances of the desulfurization sorbent were tested in a fixed bed reactor. The changes of phase and the composition of the Fe₂O₃-based high-temperature coal gas desulfurization sorbent before and after regeneration were examined by X-ray diffraction (XRD) and X-ray Photoelectron spectroscopy(XPS), and the changes of pore structure were characterized by the mercury intrusion method. The results show that the major products are Fe₃O₄ and elemental sulfur; the influences of regeneration temperature, space velocity and SO₂ concentration in inlet on regeneration performances and the changes of pore structure of the desulfurization sorbent before and after regeneration are visible. The desulfurization sorbent cannot be regenerated at 500°C in SO₂ atmosphere. Within the range of 600°C–800°C, the time of regeneration becomes shorter, and the regeneration conversion increases as the temperature rises. The time of regeneration also becomes shorter, and the elemental sulfur content of tail gas increases as the SO₂ concentration in inlet is increased. The increase in space velocity enhances the reactive course; the best VSP is 6000 h⁻¹ for regeneration conversion. At 800°C, 20 vol-% SO₂ and 6000 h⁻¹, the regeneration conversion can reach nearly to 90%.     

Investigation on the Esterification of Fatty Acids Catalyzed by the H<Subscript>3</Subscript>PW<Subscript>12</Subscript>O<Subscript>40</Subscript> heteropolyacid

In this work, the H₃PW₁₂O₄₀ heteropolyacid (HPW) was employed as a homogeneous catalyst to promote the efficient esterification (ethanolysis) of a number of saturated and unsaturated fatty acids (myristic, palmitic, stearic, oleic, and linoleic) under mild reaction conditions. HPW showed a similar activity to those observed for p-toluene sulfonic acid (PTSA) and sulfuric acid (H₂SO₄), the other acidic catalysts we compared them with in this study. In the HPW-catalyzed esterification of stearic acid, the addition of water caused a remarkable decrease in the ethyl stearate yields. On the other hand, the increase in the HPW concentration (up to a maximum value) promoted a proportional improvement in the oleic acid to ethyl oleate conversion. Kinetic measurements using oleic acid as a prototype substrate revealed that the esterification reactions catalyzed by HPW, H₂SO₄, and PTSA are of first-order in relation to the fatty acid concentration. Finally, the catalytic activity of HPW remained unaltered even after several recovery/reutilization cycles whereas the tungsten content in the final product (biodiesel produced by the HPW-catalyzed esterification of oleic acid) was found to be at an acceptably low level (0.0095 mg of W per g of biodiesel).     

Elemental sulfur production through regeneration of a SO2-adsorbed V2O5-CoO/AC in H2

H₂ regeneration of an activated carbon supported vanadium and cobalt oxides (V₂O₅-CoO/AC) catalyst–sorbent used for flue gas SO₂ removal is studied in this paper. Elemental sulfur is produced during the H₂-regeneration when effluent gas of the regeneration is recycled back to the reactor. The regeneration conditions affect the regeneration efficiency and the elemental sulfur yield. The regeneration efficiency is the highest at 330 °C, with SO₂ as the product. The production of elemental sulfur occurs at 350 °C and higher with the highest elemental sulfur yield of 9.8 mg-S/g-Cat. at 380 °C. A lower effluent gas recycle rate is beneficial to elemental sulfur production. Intermittent H₂ feeding strategy can be used to control H₂S concentration in the gas phase and increase the elemental sulfur yield. Two types of reactions occur in the regeneration, reduction of sulfuric acid to SO₂ by AC and reduction of SO₂ to elemental sulfur through Claus reaction. H₂S is an intermediate, which is important for elemental sulfur formation and for conversion of CoO to CoS that catalyzes the Claus reaction. The catalyst–sorbent exhibits good stability in SO₂ removal capacity and in elemental sulfur yield.     

The effect of HCl and H<Subscript>2</Subscript>O on the H<Subscript>2</Subscript>S removing capacities of Zn-Ti-based desulfurization sorbents promoted by cobalt and nickel oxide

The sulfur removing capacities of various Zn-Ti-based sorbents were investigated in the presence of H₂O and HCl at high-(sulfidation, 650 °C; regeneration, 800 °C) and medium-(sulfidation, 480 °C; regeneration, 580 °C) temperature conditions. The H₂O effect of all sorbents was not observed at high-temperature conditions. At mediumtemperature conditions, the reaction rate of ZT (Zn/Ti : 1.5) sorbent decreased with the level of H₂O concentration, while modified (ZTC, ZTN) sorbents were not affected by the water vapor. HCl vapor resulted in the deactivation of ZT sorbent with a cycle number at high-temperature due to the production of ZnCl₂ while the sulfur removing capacities of ZTC and ZTN sorbents were maintained during 4–5 cyclic tests. In the case of medium-temperature conditions, ZT sorbent was poisoned by HCl vapor while cobalt and nickel added to ZT sorbent played an important catalytic role to prevent from being poisoned by HCl due to providing heat, emitted when these additives quickly react with H₂S even at medium-temperature conditions, to the sorbents     

SO_2对钙基吸收剂吸收NO的作用机理

针对低温条件下SO2对Ca(OH)2吸收NO的影响进行了实验研究,分析了烟气中O2和H2O对SO2促进Ca(OH)2吸收NO的影响。实验结果表明,当烟气不含SO2时,Ca(OH)2对NO基本无吸收作用;烟气中SO2的存在对NO吸收具有促进作用。H2O和O2对SO2促进NO吸收有显著影响;当烟气不含O2时,即使大量的SO2被吸收,NO吸收效率仍较低;只有SO2与O2和H2O共存才能促进NO吸收。脱硫产物CaSO3对NO无氧化作用;NO、H2O和SO2未在吸收剂表面产生可分解释放NO2的大分子中间配合物。分析认为在脱硫过程中产生了可以促进NO与O2反应的非稳定中间活性组分。     

Role of water vapor in oxidative decomposition of calcium sulfide

CaS formed from the CaO sorbent during desulfurization in coal gasifiers has to be converted to CaSO₄ before disposal. CaS is mainly decomposed to CaO and SO₂ by O₂ and then CaO is converted to CaSO₄ by SO₂ and O₂. The role of H₂O in the oxidative decomposition of CaS with O₂ was studied using reagent grade CaS and H₂¹⁸O. The following results were obtained: (1) there is a synergistic effect of H₂O and O₂ on the oxidative decomposition of CaS to CaO and SO₂; (2) H₂O reacts with CaS to form CaO, SO₂ and H₂ in the absence of O₂; (3) the oxidative decomposition of CaS to CaO and SO₂ occurs stepwise; (4) H₂O directly reacts with CaS in the presence of O₂; (5) H₂O plays an important role in the oxidative decomposition of CaS even if the O₂ concentration is high.     

Effect of pretreatment and regeneration conditions of Ru/γ-Al2O3 catalysts for N2O decomposition and/or reduction in O2-rich atmospheres and in the presence of NOX, SO2 and H2O

The effect of the pretreatment (inert, oxidative, and reducing) of Ru/γ-Al₂O₃ catalyst on its activity and stability in the decomposition of N₂O in the absence or presence of O₂, SO₂, H₂O and NO_X was studied in the present work. Decomposition of pure N₂O was slightly enhanced by the H₂-pretreated catalyst (metallic Ru) compared to the O₂- or He-pretreated ones, owing to a cyclic oxidation–reduction pathway of metallic Ru. The observed decrease of activity by O₂ or H₂O addition was reversible compared to SO₂ which caused a strong, irreversible deactivation of the catalyst, irrespective of the type of pretreatment. This was attributed to the formation of stable sulphates, mainly those on RuO₂ surface, which could only be removed by regeneration under reducing (H₂ in He) atmosphere at temperatures of ca. 500 °C. Oxidative or inert regeneration required very high temperatures (i.e. >700 °C) in order to decompose these sulphates. A method of retaining N₂O conversion activity very high (≥98%) for long reaction times is suggested and is based on frequent and short-time (ca. 10 min) regenerations of the catalyst under reducing atmosphere (ca. 5% H₂ in He). The effect of co-feeding various reducing agents, such as CO or C₃H₆, on the N₂O conversion activity in the presence of O₂, SO₂, H₂O and NO_X is negligible, mainly because they are oxidized at relatively low temperatures in the O₂-rich feeds used in this study.     

Removal of SO2 by activated carbon fibers in the presence of O2 and H2O

This work describes the potential capability of activated carbon fibers (ACFs) in continuously removing SO₂ from inert atmosphere without requiring further regeneration. A tubular reactor packed with ACF was used to study the conversion of SO₂ into H₂SO₄ in the presence of O₂ and H₂O with varying concentrations of SO₂ (3000-10,000 ppm), O₂ (10-20%), and H₂O (10-70%) and temperatures (313-348 K). The experiments were carried out on two precursors (viscose rayon and phenolic resin) based ACFs. The breakthrough data revealed that the steady-state SO₂ concentration levels at the reactor exit increased with increasing inlet SO₂ concentration and decreased with increasing concentration levels of O₂ as well as H₂O. Increase in the reaction temperature was found to moderately enhance the steady-state exit concentration levels of SO₂. The viscose rayon-based ACF exhibited higher SO₂ removal activity in comparison to the phenolic resin-based ACF. A mathematical model was developed to predict the gas concentration profiles in the reactor, incorporating the mass transfer in the bed as well as within the ACF pores, along with the surface reactions on the ACF. The model predictions agreed reasonably well with the data.     

Improving the SO<Subscript>2</Subscript> absorption rate of CeFeMg-based sorbent promoted with titanium promoter

To improve the poor SO₂ absorption rate of CeFeMgTi sorbent with high sulfur removal capacity and fast regeneration, a new sorbent, CeFeMgTi-sol was prepared by the modified co-precipitation method and tested in a packed bed reactor at RFCC conditions (sulfation of MgO to MgSO₄ in the presence of low concentration of SO₂ at 973 K, regeneration of MgSO₄ to MgO and H₂S in the presence of H₂ at 803 K). The CeFeMgTi-sol sorbent showed excellent SO₂ absorption and sulfur removal capacity (46.2 sulfur g/g absorbent×100). It was found that the SO₂ absorption rates were related to the structure of the Mg and Ti and the textural properties such as surface area and pore volume. In the case of the fresh state of CeFeMgTi sorbent, CeO₂, MgO and MgTiO₃ structures were observed. But the new CeFeMgTisol sorbent before SO₂ absorption, showed a separated MgO and TiO₂ peak only. These differences in the sorption rates were discussed by the difference in the XRD pattern, surface area and pore volume.     

SO2 and NO removal from flue gas over V2O5/AC at lower temperatures — role of V2O5 on SO2 removal

Supporting V₂O₅ onto an activated coke (AC) has been reported to significantly increase the AC's activity in simultaneous SO₂ and NO removal from flue gas. To understand the role of V₂O₅ on SO₂ removal, V₂O₅/AC is studied through SO₂ removal reaction, surface analysis, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) techniques. It is found that the main role of V₂O₅ in SO₂ removal over V₂O₅/AC is to catalyze SO₂ oxidation through a VOSO₄-like intermediate species, which reacts with O₂ to form SO₃ and V₂O₅. The SO₃ formed transfers from the V sites to AC sites and then reacts with H₂O to form H₂SO₄. At low V₂O₅ loadings, a V atom is able to catalyze as many as 8 SO₂ molecules to SO₃. At high V₂O₅ loadings, however, the number of SO₂ molecules catalyzed by a V atom is much less, due possibly to excessive amounts of V₂O₅ sites in comparison to the pores available for SO₃ and H₂SO₄ storage.     

Structural evolution of hierarchical porous NiO/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> composites and their application for removal of dyes by adsorption

Hierarchical porous NiO/Al₂O₃ composites were successfully prepared by two-steps. First, the core-shell structured Al₂O₃ microspheres were prepared via a template-free hydrothermal route using KAl(SO₄)₂·12H₂O and Al₂(SO₄)₃·18H₂O as aluminum source. Then, the NiO/Al₂O₃ composites with micro- and nano-hierarchical structures were prepared by a hydrothermal method combining the subsequent calcination process. The obtained characterization result presented that the morphology of hierarchical Al₂O₃ microsphere tuned to irregular platelets by simply varying Ni/Al ratios. The BET analysis showed that the special surface area from 52.12m² g^?1 to 214.8m² g^?1 after two hydrothermal complex process. Effects of Ni/Al ratio, adsorbent dosage, Congo red (CR) concentration, coexisting ions, adsorption time and temperature were investigated. The obtained results indicated that NiO/Al₂O₃ composite had the high adsorption efficiency (99.6%) and great adsorption capacity (186.9mg g^?1) under the optimum conditions. The adsorption isotherm and kinetics data were found to be well fitted and in good agreement with the Langmuir isotherm model and pseudo-second order model, respectively. The hierarchical porous NiO/Al₂O₃ composites presented remarkably higher adsorption efficiency during five recycling, which showed their potential as the highly efficient adsorbent for removal of CR in wastewater.     

Mo and Co doped V2O5/AC catalyst-sorbents for flue gas SO2 removal and elemental sulfur production

Flue gas SO₂ removal at 200 °C over Mo and Co doped V₂O₅/AC catalyst-sorbents and regeneration of the used catalyst-sorbents in H₂ at 380 °C in the same reactor are studied in this paper. Compared with V₂O₅/AC, the catalyst-sorbents containing Co show higher SO₂ uptake while the one containing Mo shows a slightly lower SO₂ uptake. Elemental sulfur is produced during H₂-regeneration of the used catalyst-sorbents when effluent gas of the regeneration is recycled back to the reactor. H₂-regeneration of the used V₂O₅/AC produces little elemental sulfur, but the Mo and Co doped ones show high elemental sulfur yields with an elemental sulfur selectivity of 50% for a catalyst-sorbent containing 2% V₂O₅, 0.5% MoO₃ and 0.5% CoO, V2Mo0.5 Co0.5/AC. Molybdenum and cobalt sulfides are likely formed in the regeneration, which catalyze the elemental sulfur formation but reduce the SO₂ uptake of the catalyst-sorbents in the subsequent SO₂ removal stage.     

Porous MnO<Subscript>2</Subscript>/CNT catalysts with a large specific surface area for the decomposition of hydrogen peroxide

H₂O₂ vapor sterilization is an effective and safe method for removing various pathogens. To improve the efficiency of this technique, the time required for sterilization must be shortened. The aeration time constitutes a large portion of the total sterilization time; therefore, the development of a catalyst for H₂O₂ decomposition is necessary. Bulk MnO₂ is typically used in H₂O₂ decomposition, but it has a low specific surface area. To increase H₂O₂ decomposition activity, specific surface area and electron transfer ability of catalyst need improvement. In this study, MnO₂/CNT(x), where x denotes the weight ratio of CTAB to H₂O in the catalyst preparation, was synthesized using a soft template method with varying amounts of the template. Overall, the catalyst specific surface area remarkably increased to 190–200 m²/g from 0.043 m²/g for bulk MnO₂ and these increased surface areas resulted in superior H₂O₂ decomposition activity. Among the CNT-supported catalysts tested, MnO₂/CNT (1.0) exhibited the highest activity, which was 570 times that of bulk MnO₂. Aeration times were also calculated with some assumptions and the aeration can be finished within 1 hr (bulk MnO₂ needs about 25 hr).     

Chemical desulfurization of petroleum fractions for ultra-low sulfur fuels

An improved desulfurization process for removing sulfur from hydro treated diesel oil based on the oxidation of thiophenic type sulfur-containing compounds with H₂O₂ and acetic acid (AcOH) using H₂SO₄ as catalyst has been studied. The experimental results show that the sulfone content in the oxidation product increased rapidly with an increase in acetic acid and sulfuric acid ratios from 1:0 to 2:1 mole ratios. The maximum DBT conversion (wt.%) was at 2:1 mole ratio of acetic acid/sulfuric acid. This oxidation process is found to be capable of removing up to 90% of the sulfur compounds in hydro treated real fuels and can provide an alternative way to meet the future sulfur environmental requirements.     

Electrical conductivity and the nature of charge carriers in glasses of the Tl<Subscript>2</Subscript>O-B<Subscript>2</Subscript>O<Subscript>3</Subscript> system

The concentration dependence of the electrical conductivity of glasses in the Tl₂O-B₂O₃ system is studied. The nature of charge carriers in this system is experimentally investigated for the first time. It is demonstrated using the Hittorf, Tubandt, and Hebb-Liang-Wagner techniques and the Faraday law that neither Tl⁺ ions nor electrons are involved in the electricity transport. The verification of the Faraday law does not reveal the presence of thallium in the amalgam of the cathode or a change in the sample weight after electrolysis, to within the experimental error. This allows one to make the inference that protons can be charge carriers in glasses of the Tl₂O-B₂O₃ system. It is shown using extended X-ray absorption fine structure (EXAFS) spectroscopy that Tl³⁺ ions and thallium Tl⁰ reduced to the metallic state are absent in the structure of the glasses under investigation. This means that thallium in glasses of the Tl₂O-B₂O₃ system occurs only in the form of Tl⁺ ions. The analysis of the IR spectroscopic data leads to only a qualitative conclusion that the water content in the glasses insignificantly increases with an increase in the thallium oxide content. An increase in the electrical conductivity of glasses in the Tl₂O-B₂O₃ system with an increase in the thallium oxide content is explained by the increase in the number of protons formed upon dissociation of H⁺[BO_4/2]^? structural-chemical units, because their concentration increases with increasing Tl₂O content. In the structure of boron oxide, impurity hydrogen enters predominantly into the composition of H⁺[O_2/2BO^?] structural-chemical units, for which the dissociation energy is higher than that for the H⁺[BO_4/2]^? structural-chemical units. The increase in the concentration of H⁺[BO_4/2]^? structural-chemical units is accompanied by the increase in the number of dissociated protons, which are charge carriers in glasses of the Tl₂O-B₂O₃ system.     

Synthesis of Heterogeneous Li<Subscript>4</Subscript>Ti<Subscript>5</Subscript>O<Subscript>12</Subscript> Nanostructured Anodes with Long-Term Cycle Stability

The 0D-1D Lithium titanate (Li₄Ti₅O₁₂) heterogeneous nanostructures were synthesized through the solvothermal reaction using lithium hydroxide monohydrate (Li(OH)·H₂O) and protonated trititanate (H₂Ti₃O₇) nanowires as the templates in an ethanol/water mixed solvent with subsequent heat treatment. A scanning electron microscope (SEM) and a high resolution transmission electron microscope (HRTEM) were used to reveal that the Li₄Ti₅O₁₂ powders had 0D-1D heterogeneous nanostructures with nanoparticles (0D) on the surface of wires (1D). The composition of the mixed solvents and the volume ratio of ethanol modulated the primary particle size of the Li₄Ti₅O₁₂ nanoparticles. The Li₄Ti₅O₁₂ heterogeneous nanostructures exhibited good capacity retention of 125 mAh/g after 500 cycles at 1C and a superior high-rate performance of 114 mAh/g at 20C.     

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.     

Dynamics and Selectivity of N<Subscript>2</Subscript>O Formation/Reduction During Regeneration Phase of Pt-Based Catalysts

The formation of N₂O has been studied by means of isothermal lean-rich experiments at 150, 180 and 250 °C over Pt–Ba/Al₂O₃ and Pt/Al₂O₃ catalysts with H₂ and/or C₃H₆ as reductants. This allows to provide further insights on the mechanistic aspects of N₂O formation and on the influence of the storage component. Both gas phase analysis and surface species studies by operando FT-IR spectroscopy were performed. N₂O evolution is observed at both lean-to-rich (primary N₂O) and rich-to-lean (secondary N₂O) transitions. The production of both primary and secondary N₂O decreases by increasing the temperature. The presence of Ba markedly decreases secondary N₂O formation. FT-IR analysis shows the presence of adsorbed ammonia at the end of the rich phase only for Pt/Al₂O₃ catalyst. These results suggest that: (i) primary N₂O is formed when undissociated NO in the gas phase and partially reduced metal sites are present; (ii) secondary N₂O originates from reaction between adsorbed NH₃ and residual NO_x at the beginning of the lean phase. Moreover, N₂O reduction was studied performing temperature programming temperature experiments with H₂, NH₃ and C₃H₆ as reducing agents. The reduction is completely selective to nitrogen and occurs at temperature higher than 250 °C in the case of Pt–Ba/Al₂O₃ catalyst, while lower temperatures are detected for Pt/Al₂O₃ catalyst. The reactivity order of the reductants is the same for the two catalysts, being hydrogen the more efficient and propylene the less one. Having H₂ a high reactivity in the reduction of N₂O, it could react with N₂O when the regeneration front is developing. Moreover, also ammonia present downstream to the H₂ front could react with N₂O, even if the reaction with stored NO_x seems more efficient.     

Photocatalytic Generation of H<Subscript>2</Subscript> Gas from Neat Ethanol over Pt/TiO<Subscript>2</Subscript> Nanotube Catalysts

TiO₂ nanotubes promoted with Pt metal were prepared and tested to be the photocatalytic dehydrogenation catalyst in neat ethanol for producing H₂ gas (C₂H₅OHC₃CHO +H₂). It was found that the ability to produce H₂, the liquid phase product distribution and the catlyst stability of these promoted nano catalysts all depended on the Pt loading and catalyst preparation procedure. These Pt/TiO₂ catalysts with TiO₂ nanotubes washed with diluted H₂SO₄ solution produced 1, 2-diethoxy ethane (acetal) as the major liquid phase product, while over those washed with diluted HCl solution or H₂O, acetaldehyde was the major liquid phase product.