Catalytic Dehydration Of Ethanol Research Articles

Ethanol Dehydration over WO3/TiO2Catalysts Using Titania Derived from Sol-Gel and Solvothermal Methods

The present study aims to investigate the catalytic ethanol dehydration to higher value products including ethylene, diethyl ether (DEE), and acetaldehyde. The catalysts used for this reaction were WO3/TiO2catalysts having W loading of 13.5 wt.%. For a comparative study, the TiO2supports employed were varied by two different preparation methods including the sol-gel and solvothermal-derived TiO2supports, denoted as TiO2-SG and TiO2-SV, respectively. It is obvious that the different preparation methods essentially altered the physicochemical properties of TiO2supports. It was found that the TiO2-SV exhibited higher surface area and pore volume and larger amounts of acid sites than those of TiO2-SG. As a consequence, different characteristics of support apparently affected the catalytic properties of WO3/TiO2catalysts. As expected, both catalysts WO3/TiO2-SG and WO3/TiO2-SV exhibited increased ethanol conversion with increasing temperatures from 200 to 400°C. It appeared that the highest ethanol conversion (ca. 88%) at 400°C was achieved by the WO3/TiO2-SV catalysts due to its high acidity. It is worth noting that the presence of WO3onto TiO2-SV yielded a remarkable increase in DEE selectivity (ca. 68%) at 250°C. In summary, WO3/TiO2-SV catalyst is promising to convert ethanol into ethylene and DEE, having the highest ethylene yield of ca. 77% at 400°C and highest DEE yield of ca. 26% at 250°C. These can be attributed to proper pore structure, acidity, and distribution of WO3.

Carbon-Based Catalyst from Pyrolysis of Waste Tire for Catalytic Ethanol Dehydration to Ethylene and Diethyl Ether

This work investigated the use of waste tire as a source of carbon in preparation of carbon-based catalysts for applying in ethanol dehydration. The pyrolysis of waste tire was performed to obtain the solid carbon, and then it was treated with two different acids including HCl and HNO3 prior to the activation process with different temperatures to gain suitable carbon catalysts. All carbon catalysts were characterized using nitrogen physisorption, XRD, FTIR, and acid-base titration. The catalysts were tested for catalytic ethanol dehydration in a micropacked-bed reactor under the temperature range from 200°C to 400°C. It revealed that the ethanol conversion increased with increasing the reaction temperature for all catalysts. The carbon catalyst treated with HCl and calcined at 420°C (AC_H420) exhibited the highest ethanol conversion of 36.2% at 400°C having ethylene and diethyl ether selectivity of 65.9 and 33.5%, respectively. The high activity of this catalyst can be attributed to the high acid density at the surface (18.5 μmol/m2), which was significantly higher than those of most other catalysts (less than 8.0 μmol/m2).

Modeling of Catalyst Deactivation in Bioethanol Dehydration Reactor

The catalytic ethanol dehydration route is a reality for the production of polyethylene from renewable sources. Ethanol dehydration process is performed in the presence of acid catalysts, under tem...

Catalytic dehydration of ethanol to ethylene and diethyl ether over alumina catalysts containing different phases with boron modification

The catalytic ethanol dehydration of ethanol over the solvothermal-derived alumina catalysts was investigated in this study. First, alumina catalysts were synthesized by the solvothermal methods to obtain three different phase composition of alumina catalysts including γ-phase (G–Al), χ-phase (C–Al) and equally mixed χ–γ phases (M–Al). Then, all catalysts were modified with boron (G–Al–B, C–Al–B and M–Al–B). It was found that the boron modification increased the amounts of total acid sites and the ratio of weak to strong acid sites (WSR). The catalytic activity and product selectivity of six catalysts via catalytic ethanol dehydration at 200, 300, and 400 °C were measured. For all catalysts, it revealed that ethanol conversion increased with increased temperatures from 200 to 400 °C. At 200–300 °C, the unmodified catalysts tended to exhibit the higher catalytic activity than the boron-modified catalysts. However, at high temperature (400 °C), the boron modification tended to increase the catalytic activity, especially for the M–Al–B catalyst (complete ethanol conversion at 400 °C). Considering ethylene production, the M–Al–B exhibited the highest ethylene yield among other catalysts with 92% at 400 °C. For diethyl ether, it was observed that the M–Al catalyst gave the highest diethyl ether yield of 57% at 300 °C. This is because the boron modification increased the amounts of total acid sites, which can promote the production of ethylene, while this is not preferable for diethyl ether production, which is favored by weak acid sites.

Process Modeling and Simulation of an Industrial-Scale Plant for Green Ethylene Production

Catalytic dehydration of ethanol is a key step in the production of polyethylene from renewable raw materials. Obtaining a mathematical model to optimize the ethanol-to-ethylene reactor setup is of great interest to the industry, allowing the optimal design of larger plants and improvements to existing plants. This work presents a phenomenological model of an ethanol dehydration reactor that takes into account 8 chemical reactions and 10 chemical species, considering nonidealities in the reaction rates and axial catalyst activity profile. Additionally, the axial variation of pressure, velocity, and thermodynamics properties are considered in the proposed model. Model validation at different operating conditions shows that the predicted temperature and composition profiles match the data from an industrial plant with relative deviations below 5% and from a pilot plant with relative deviation below 0.4%.

Production of Ethylene through Ethanol Dehydration on SBA-15 Catalysts Synthesized by Sol-gel and One-step Hydrothermal Methods.

The present work deals with the catalytic performance of SBA-15 supported catalysts in the gas phase catalytic dehydration of ethanol in the temperature range of 200 to 400°C. The SBA-15 support was incorporated on a zirconium (Zr) and bimetal of zirconium and lanthanum (Zr-La) prepared by sol-gel (SG) and hydrothermal (HT) methods. The catalysts were characterized by means of N2 physisorption, SEM/EDX, and NH3-TPD. The experimental results demonstrated that the Zr-La/SBA-15-HT exhibited the highest catalytic activity. Ethanol conversion and ethylene selectivity were found to increase with increased reaction temperature. The best catalytic results were achieved for Zr-La/SBA-15-HT indicating values of ethanol conversion and ethylene yield of ca. 84% and 80%, respectively at 400°C. The most important parameter influencing their catalytic properties appears to be the interaction between metal and support depending on different methods. The metal dispersion inside the siliceous matrix of SBA-15 has a direct influence on their surface acidity. Meanwhile, the performance of these SBA-15 supported catalysts in ethanol dehydration is also related with the alteration of surface acidity caused by the introduction of Zr and Zr-La.

Characterization of Different Si- and Al-based Catalysts with Pd Modification and Their Use for Catalytic Dehydration of Ethanol.

This study aims to investigate the production of ethylene and diethyl ether from ethanol via catalytic dehydration using Si- and Al-based catalysts with Pd modification. First, six catalysts including H-beta zeolite (HBZ), mixed phases of γ-χ-Al2O3 (M-Al) and γ-Al2O3 (G-Al) with and without Pd modification (0.5 wt%) were prepared. The catalytic dehydration of vaporized ethanol at temperature ranging from 200 to 400°C was performed over the catalysts. For ethylene production, the most promising catalyst is HBZ (giving ethylene yield of ca. 99% at 400°C), whereas Pd modification has no significant effect on ethylene production. Considering the production of diethyl ether, it is produced at lower temperature (ca. 250°C) than that of ethylene. The most active catalyst to produce diethyl ether is HBZ with Pd modification (giving diethyl ether yield of ca. 48% at 250°C). Thus, increased diethyl ether yield can be achieved with Pd modification at low temperature for the HBZ catalyst. Other catalysts such as M-Al and G-Al can also produce significant amounts of ethylene. To elucidate the effect of Pd modification on these catalysts, different characterization techniques such as nitrogen physisorption (BET and BJH methods), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS) and ammonia temperature-programmed desorption were performed and further discussed in more detail.

Effects of boron and fluorine modified γ-Al2O3 with tailored surface acidity on catalytic ethanol dehydration to ethylene

The effect of boron and fluorine modified γ-Al2O3 was investigated during ethanol dehydration to ethylene. The conventional and modified γ-Al2O3 were prepared by a sol–gel method and characterized by various techniques. The results showed that boron modified γ-Al2O3 possessed decreased amount of Lewis acid sites by increasing the boron content. Fluorine modified γ-Al2O3 created new Bronsted acid sites with increasing the fluorine content, which resulted in the coexistence of Bronsted and Lewis acid sites, at the same time, strong acid sites appeared. Boron modified γ-Al2O3 catalyst (Al-B1) at 340 °C exhibited excellent catalytic stability and good selectivity for ethanol conversion to ethylene. The improvement in the catalytic stability could be attributed to the lower acidity after boron modification. The results indicated that on γ-Al2O3 catalyst, strong acid sites especially Bronsted acid sites were responsible for coking deactivation and unfavorable to ethanol dehydration to ethylene.

Theoretical investigation of the selective dehydration and dehydrogenation of ethanol catalyzed by small molecules

Catalytic dehydration and dehydrogenation reactions of ethanol have been investigated systematically using the ab initio quantum chemistry methods The catalysts include water, hydrogen peroxide, formic acid, phosphoric acid, hydrogen fluoride, ammonia, and ethanol itself. Moreover, a few clusters of water and ethanol were considered to simulate the catalytic mechanisms in supercritical water and supercritical ethanol. The barriers for both dehydration and dehydrogenation can be reduced significantly in the presence of the catalysts. It is revealed that the selectivity of the catalytic dehydration and dehydrogenation depends on the acidity and basicity of the catalysts and the sizes of the clusters. The acidic catalyst prefers dehydration while the basic catalysts tend to promote dehydrogenation more effectively. The calculated water-dimer catalysis mechanism supports the experimental results of the selective oxidation of ethanol in the supercritical water. It is suggested that the solvent- and catalyst-free self-oxidation of the supercritical ethanol could be an important mechanism for the selective dehydrogenation of ethanol on the theoretical point of view.

Catalytic dehydration of ethanol into ethylene in a tubular reactor of the pilot installation on alumina catalysts with varied grain size

Synthesis of ethylene on trefoil and cylindrical experimental acid-modified aluminum oxide samples was studied under an ethanol (94%) gas load of 920–2200 h–1 and heat-carrier temperature of 400–440°C. In the conditions of a 98% ethanol conversion, the higher activity of the trefoil made it possible to reduce the height of the bed and its hydraulic resistance and, accordingly, raise the specific catalyst throughput for ethylene. Compared with industrial aluminum oxide, the throughput of 1 g of the catalyst for ethylene on experimental samples is higher by 2.5–6.5 kg yr–1, and the specific expenditure of ethanol is lower by 0.22–0.23 kg kg–1. The endothermic process in a tubular reactor is characterized by a high parametric sensitivity of the average integral temperature along the catalyst bed, with the average temperature being higher on the less active catalyst. Thus, the higher average temperature can compensate for the lower activity of the catalyst without additional increase in the contact duration and(or) heat-carrier temperature.

Alkaline-acid treated zeolite L as catalyst in ethanol dehydration process

In the present study, the catalytic dehydration of ethanol to obtain ethylene over efficiently top-down modified zeolites L was investigated at temperature range of 100–300 °C. It revealed that the nature of an acidic Si(OH)Al groups determined the catalytic activity of the studied materials. The alkaline/acid treated zeolites L accommodating solely the isolated Si(OH)Al groups exhibited the highest catalytic activity and selectivity to ethylene. Modification routes increasing population of the hydrogen bonded Si(OH)Al⋯O species reduced an activity of the catalysts. The most active catalyst yielded 99% of ethanol conversion having 96% of ethylene yield at 280 °C. Upon the stability test for 30 h during the reaction, the modified zeolite L showed neither formation of higher hydrocarbons nor deactivation due to carbon deposition.

Diethyl Ether Production during Catalytic Dehydration of Ethanol over Ru- and Pt- modified H-beta Zeolite Catalysts.

In the present study, the catalytic dehydration of ethanol over H-beta zeolite (HBZ) catalyst with ruthenium (Ru-HBZ) and platinum (Pt-HBZ) modification was investigated. Upon the reaction temperature between 200 and 400°C, it revealed that ethanol conversion and ethylene selectivity increased with increasing temperature for both Ru and Pt modification. At lower temperature (200 to 250°C), diethyl ether (DEE) was the major product. It was found that Ru and Pt modification on HBZ catalyst can result in increased DEE yield at low reaction temperature due to increased ethanol conversion without a significant change in DEE selectivity. By comparing the DEE yield of all catalysts in this study, the Ru-HBZ catalyst apparently exhibited the highest DEE yield (ca. 47%) at 250°C. However, at temperature from 350 to 400°C, the effect of Ru and Pt was less pronounced on ethylene yield. With various characterization techniques, the effects of Ru and Pt modification on HBZ catalyst were elucidated. It revealed that Ru and Pt were present in the highly dispersed forms and well distributed in the catalyst granules. It appeared that the weak acid sites measured by NH3 temperature-programmed desorption technique also decreased with Ru and Pt promotion. Thus, the increased DEE yields with the Ru and Pt modification can be attributed to the presence of optimal weak acid sites leading to increased intrinsic activity of the catalysts. It can be concluded that the modification of Ru and Pt on HBZ catalyst can improve the DEE yields by ca. 10%.

Catalytic Ethanol Dehydration to Ethylene over Nanocrystalline χ- and γ-Al2O3 Catalysts.

The study is aimed to investigate the combination of nanocrystalline γ- and χ- alumina that displays the attractive chemical and physical properties for the catalytic dehydration of ethanol. The correlation between the acid density and ethanol conversion was observed. The high acid density apparently results in high catalytic activity, especially for the equally mixed γ- and χ- phase alumina (G50C50). In order to obtain a better understanding on how different catalysts would affect the ethylene yield, one of the most powerful techniques such as X-ray photoelectron spectroscopy (XPS) was performed. Hence, the different O 1s surface atoms can be identified and divided into three types including lattice oxygen (O, 530.7 eV), surface hydroxyl (OH, 532.1 eV) and lattice water (H2O, 532.9 eV). It was remarkably found that the large amount of O 1s surface atoms in lattice water can result in increased ethylene yield. In summary, the appearance of metastable χ-alumina structure exhibited better catalytic activity and ethylene yield than γ- alumina. Thus, the introduction of metastable χ- alumina structure into γ- alumina enhanced catalytic activity and ethylene yield. As the result, it was found that the G50C50 catalyst exhibits the ethylene yield (80%) at the lowest reaction temperature ca. 250°C among other catalysts.

Effect of Calcination Temperatures and Mo Modification on Nanocrystalline (γ-χ)-Al2O3 Catalysts for Catalytic Ethanol Dehydration

The mixed gamma and chi crystalline phase alumina (M-Al) catalysts prepared by the solvothermal method were investigated for catalytic ethanol dehydration. The effects of calcination temperatures and Mo modification were elucidated. The catalysts were characterized by X-ray diffraction (XRD), N2 physisorption, transmission electron microscopy (TEM), and NH3-temperature programmed desorption (NH3-TPD). The catalytic activity was tested for ethylene production by dehydration reaction of ethanol in gas phase at atmospheric pressure and temperature between 200°C and 400°C. It was found that the calcination temperatures and Mo modification have effects on acidity of the catalysts. The increase in calcination temperature resulted in decreased acidity, while the Mo modification on the mixed phase alumina catalyst yielded increased acidity, especially in medium to strong acids. In this study, the catalytic activity of ethanol dehydration to ethylene apparently depends on the medium to strong acid. The mixed phase alumina catalyst calcined at 600°C (M-Al-600) exhibits the complete ethanol conversion having ethylene yield of 98.8% (at 350°C) and the Mo-modified catalysts promoted dehydrogenation reaction to acetaldehyde. This can be attributed to the enhancement of medium to strong acid with metal sites of catalyst.

A Comparative Study of Different Al-based Solid Acid Catalysts for Catalytic Dehydration of Ethanol

In this present study, the catalytic dehydration of ethanol over three different Al-based solid acid catalysts including H-beta zeolite (HBZ), modified H-beta zeolite with γ-Al 2 O 3 (Al-HBZ) and mixed γ- χ phase of Al 2 O 3 (M-Al) catalysts was investigated. The ethanol dehydration reaction was performed at temperature range of 200 to 400 o C. It revealed that all catalysts exhibited higher ethanol conversion with increased temperatures. At low temperatures (ca. 200 to 250 o C), diethyl ether (DEE) was obtained as a major product for all catalysts. However, with increased temperatures (ca. 300 to 400 o C), ethylene was a major product. Among all catalysts, HBZ exhibited the highest ethanol conversion giving the ethylene yield of 99.4% at 400 o C. This can be attributed to the largest amount of weak acid sites present in HBZ, which is related to the Bronsted acid. It should be mentioned that HBZ also rendered the highest yield of DEE (ca. 35.3%) at 250 o C. As the results, HBZ catalyst is promising to produce ethylene and DEE from ethanol, which is considered as cleaner technology.

Catalytic dehydration of ethanol over hierarchical ZSM-5 zeolites: studies of their acidity and porosity properties

The catalytic activity of novel micro/mesoporous ZSM-5 in the dehydration process of alcohols has been studied with respect to their acidity and porosity.

Catalytic Ethanol Dehydration over Different Acid-activated Montmorillonite Clays.

In the present study, the catalytic dehydration of ethanol to obtain ethylene over montmorillonite clays (MMT) with mineral acid activation including H2SO4 (SA-MMT), HCl (HA-MMT) and HNO3 (NA-MMT) was investigated at temperature range of 200 to 400°C. It revealed that HA-MMT exhibited the highest catalytic activity. Ethanol conversion and ethylene selectivity were found to increase with increased reaction temperature. At 400°C, the HA-MMT yielded 82% of ethanol conversion having 78% of ethylene yield. At lower temperature (i.e. 200 to 300°C), diethyl ether (DEE) was a major product. The highest activity obtained from HA-MMT can be attributed to an increase of weak acid sites and acid density by the activation of MMT with HCl. It can be also proven by various characterization techniques that in most case, the main structure of MMT did not alter by acid activation (excepted for NA-MMT). Upon the stability test for 72 h during the reaction, the MMT and HA-MMT showed only slight deactivation due to carbon deposition. Hence, the acid activation of MMT by HCl is promising to enhance the catalytic dehydration of ethanol.

Effect of Mo-Doped Mesoporous Al-SSP Catalysts for the Catalytic Dehydration of Ethanol to Ethylene

The catalytic dehydration of ethanol to ethylene over the mesoporous Al-SSP and Mo-doped Al-SSP catalysts was investigated. The Al-SSP catalyst was first synthesized by the modified sol-gel method and then doped with Mo by impregnation to obtain 1% Mo/Al-SSP and 5% Mo/Al-SSP catalysts (1 and 5 wt% of Mo). The final catalysts were characterized using various techniques such as XRD, N2physisorption, SEM/EDX, TEM, and NH3-TPD. The catalytic activity for all catalysts in gas-phase ethanol dehydration reaction was determined at temperature range of 200°C to 400°C. It was found that the most crucial factor influencing the catalytic activities appears to be the acidity. The acid property of catalysts depended on the amount of Mo loading. Increased Mo loading in Al-SSP resulted in increased weak acid sites, which enhanced the catalytic activity. Besides acidity, the high concentration of Al at surface of catalyst is also essential to obtain high activity. Based on the results, the most suitable catalyst in this study is 1% Mo/Al-SSP catalyst, which can produce ethylene yield of ca. 90% at 300°C with slight amounts of diethyl ether (DEE) and acetaldehyde.

Catalytic Dehydration of Ethanol to Ethylene Over Steam-Treated ZSM-5 Zeolites

The steam-treated ZSM-5 zeolites are characterized by XRD, N-2 sorption, SEM, Al-27 MAS NMR and NH3-TPD techniques. The steaming procedures do not alter textural structures, but generate significant variations in the acidity. The catalytic properties of steam-treated ZSM-5 catalysts in dehydration of ethanol into ethylene are investigated in a fixed bed reactor at 150-350 degrees C and an atmospheric pressure. The decreased total acid sites and increased ratio of weak acid to strong acid after steam treatment may suppress ethylene from secondary reactions, and therefore lead to improved ethylene selectivity at higher temperature. Compared to parent ZSM-5, ZSM-5 treated at 600 degrees C (ZSM-600) shows excellent stability for ethylene production. The reaction conditions (space velocity and ethanol partial pressure) have significant influences on ethanol conversion and ethylene selectivity.

Ordered crystalline mesoporous γ-alumina fabricated by vacuum-promoted self-assembly and alkaline hydrothermal method

As a commonly adopted approach to mesoporous alumina (MA), evaporation induced self-assembly (EISA) method with precursors containing chloride (e.g. AlCl3) faces a challenge to yield an ordered MA with crystalline pore walls because the chloride ion (Cl−) could affect the assembly and crystallization, resulting from the strong coordination of Cl− to aluminum. Herein, a vacuum-promoted self-assembly and alkaline hydrothermal approach was developed and realized the preparation of ordered crystalline MA from AlCl3. The obtained MA possesses ordered mesoporous structure, crystallized pore walls, narrow pore size distribution, large surface (390m2/g) and shows a superior catalytic performances towards catalytic dehydration of ethanol to ethylene.