Search

Abstract: In the present study, the solvent effects on the catalytic behaviors of [t-BuNSiMe2Flu]TiMe2 complex during ethylene/1-hexene (EH) copolymerization were investigated. Based on the study, it revealed that activities of polymerization strongly depended on the solvent medium used regarding to its dielectric constant value (ε). In fact, four solvent mediums such as heptane, chlorobenzene, toluene, and dichloromethane were selected. It was found that at 70°C, the catalytic activity was the highest when toluene was employed during ethylene polymerization and EH copolymerization. However, with changing the polymerization temperature to 0°C, the solvent effect was less pronounced and low activities were obtained. In order to give a better explanation, the contact ion-pair model was applied. The microstructure of polymer was further discussed in more details. [Copyright &y& Elsevier]

Mesocellular foam carbon (MCF-C) is one the captivating materials for using in gas phase dehydrogenation of ethanol. Extraordinary, enlarge pore size, high surface area, high acidity, and spherical shape with interconnected pore for high diffusion. In contrary, the occurrence of the coke is a majority causes for inhibiting the active sites on catalyst surface. Thus, this study aims to investigate the occurrence of the coke to optimize the higher catalytic activity, and also to avoid the coke formation. The MCF-C was synthesized and investigated using various techniques. MCF-C was spent in gas-phase dehydrogenation of ethanol under mild conditions. The deactivation of catalyst was investigated toward different conditions. Effects of reaction condition including different reaction temperatures of 300, 350, and 400 °C on the deactivation behaviors were determined. The results indicated that the operating temperature at 400 °C significantly retained the lowest change of ethanol conversion, which favored in the higher temperature. After running reaction, the physical properties as pore size, surface area, and pore volume of spent catalysts were decreased owing to the coke formation, which possibly blocked the pore that directly affected to the difficult diffusion of reactant and caused to be lower in catalytic activity. Furthermore, a slight decrease in either acidity or basicity was observed owing to consumption of reactant at surface of catalyst or chemical change on surface caused by coke formation. Therefore, it can remarkably choose the suitable operating temperature to avoid deactivation of catalyst, and then optimize the ethanol conversion or yield of acetaldehyde. [ABSTRACT FROM AUTHOR]

The catalytic dehydration of ethanol was studied over spherical silica particle (SSP) and alumina-silica composite (Al-SSP). The catalysts were prepared by the modified sol-gel method with various alumina content ranging from 20 to 80 mol%. The 60Al-SSP catalyst exhibited the highest weak (Lewis) and total acid site giving the best ethanol conversion of 98% and ethylene selectivity of 99% at 400 °C and enhanced the catalytic performance with the excellent activity and stability with TOS for 10 h. Changing acid sites of catalyst due to water effect in different ethanol concentrations also led to a better ethylene selectivity. Unlabelled Image • Al-SSP catalysts were identified in large aggregates between silica and alumina. • The selectivity of ethylene and diethyl ether could be altered by adding alumina. • Using bioethanol showed higher ethylene selectivity and less coke decomposition. [ABSTRACT FROM AUTHOR]

The catalytic ethanol dehydration with oxygen cofeeding over different pretreated Pd-HBZ catalysts was investigated. The catalyst was pretreated with different gas including air, nitrogen, and hydrogen. It was tested in ethanol dehydration in the presence and absence of oxygen cofeeding. It was significantly found that with the presence of oxygen cofeeding, the complete ethanol conversion was obtained at very low temperature (ca. 200 °C) and ethylene was a major product. This can be attributed to increased moderate and strong acid sites of catalyst by oxygen cofeeding. In addition, the different gas pretreatment seemed to have less effect on catalytic behaviors. Unlabelled Image • Different pretreatments on Pd-HBZ and O 2 cofeeding affected ethanol dehydration. • Enhanced ethylene yield was observed at 200 °C under oxygen cofeeding. • Pd-HBZ-H exhibited the highest ethylene yield of 62% at 200 °C with O 2 cofeeding. [ABSTRACT FROM AUTHOR]

[Display omitted] • Addition of Ag to Montmorillonite promotes direct ethanol dehydrogenation pathway. • Presence of Li increases Ag reducibility on Montmonitrolline and Al 13 -modified Montmonitrolline. • Ethanol dehydrogenation triggers dispersion of Ag clusters on Montmonitrolline and Al 13 -modified Montmonitrolline. • Lithium increases Ag redispersion during ethanol dehydrogenation. The oxidative dehydrogenation (ODH) of ethanol over Ag and AgLi catalyst anchored on unmodified and modified (aluminated) montmorillonite (MT) clay was studied. The results indicate that AgLi formulations anchored on aluminated MT were effective for acetaldehyde production, while unmodified formulations favored ethylene production. Characterization studies indicate that the catalyst activity is regulated by the crystalline size of the silver clusters and the amount of weak basic sites present in the support. The synergism observed is rationalized in terms of a Ag re-dispersion mechanism probed through operando and in situ UV–vis analysis. [ABSTRACT FROM AUTHOR]

• Bacterial cellulose-derived activated carbon can generate high mesoporosity in MFI. • Mesoporous ZSM-5 exhibited a fast formaldehyde adsorption rate. • Mesoporous ZSM-5 showed excellent stability for reuse as an adsorbent. • The reported zeolites can be used for fast removal of aqueous organics. Mesoporous ZSM-5 (MFI) zeolite was synthesized by using bacterial cellulose-derived activated carbon (BC-AC500) with a high surface area as a hard template. Different ratios of BC-AC500 and zeolite precursor gel were prepared in a Teflon-lined autoclave and crystallized at 180 °C for 48 h in a rotating oven. The physicochemical properties of the samples were characterized by x-ray diffraction (XRD), scanning/transmission electron microscopies (SEM/TEM), and N 2 physisorption techniques. It was found that the mesoporous ZSM-5 zeolites have a specific surface area of 184-190 m2/g, a high mesopore volume of 0.120–0.956 ml/g and a wide pore size distribution ranging from 5 to 100 nm with a maximum at approximately 25.3 nm. The successfully made mesoporous ZSM-5 was tested as an adsorbent for formaldehyde adsorption in batch mode. The mesoporous ZSM-5 zeolite made from bacterial cellulose-derived activated carbon showed significantly faster adsorption kinetics than conventional ZSM-5 (0.0081 vs. 0.0007 g/mg min, respectively). The prepared material has an adsorption capacity of 98 mg/g and is highly reusable. The reported mesoporous ZSM-5 zeolites can be deployed for the rapid removal of toxic organics from wastewater when urgently needed, e.g., under breakthrough conditions. [ABSTRACT FROM AUTHOR]

Three AgLi/SiO2 catalysts containing different types of silica supports [small particle size (SPS), medium particle size (MPS), and large particle size (LPS)] were prepared by incipient wetness coimpregnation techniques and tested in oxidative dehydrogenation of ethanol into acetaldehyde. The catalysts were characterized and evaluated by various characterization techniques (e.g. XRD, N2 physisorption, SEM-EDX, UV-Visible spectroscopy, H2-TPR, and CO2-TPD). This study reveals that the catalyst with the best performance is AgLi/SiO2-LPS with a yield in acetaldehyde of 76.8% at 300 °C. The results obtained with the tested catalysts are discussed, and the reasons of performance improvement caused by the presence of the dispersion of active components, the interaction between active components and silica supports, the textural properties of catalysts and reducibility, are raised. Besides, the cooperation of redox properties (Agnδ+ cluster and Ag0) and weak basic density played a pivotal role in promoting the formation of acetaldehyde from ethanol oxidative dehydrogenation. [ABSTRACT FROM AUTHOR]

The Na-ZSM-5 catalysts (SiO2/Al2O3 molar ratio = 20, 35, and 50) were prepared by rapid crystallization method to investigate their performance in butene cracking reaction. The XRD, XRF, NH3-TPD, FT-IR, TPO, UV–Vis, and 1H, 27Al, 29Si MAS NMR techniques were used to identify the physical and chemical properties of Na-ZSM-5 catalysts. The silanol group (Si–OH) was the main acid site of Na-ZSM-5, and it was proposed to be the active site for the butene cracking reaction. The butene conversion and coke formation were associated with the abundance of silanol groups over the Na-ZSM-5 catalyst. The dealumination, resulting in the deformation of tetrahedral framework aluminum species was a key factor for Na-ZSM-5 catalyst deactivation, because of the Si–O–Al bond breaking and formation of Si–O–Si bond. The stability of the Si–O–Al bond was linked to the molar number of sodium since the Na atom interacts with the Si–O–Al bond to form Si–ONa–Al structure, which enhances the stability of the silanol group. Therefore, the Si–ONa–Al in zeolite framework was an essential structure to retain the catalyst stability during the reaction. The Na-ZSM-5 with the lowest SiO2/Al2O3 molar ratio showed the best performance in this study resulting the highest propylene yield and catalyst stability. [ABSTRACT FROM AUTHOR]

This study aims to investigate the catalytic behaviors on W/TiO2 catalysts having different phases of TiO2 towards catalytic dehydration of ethanol to higher value products including ethylene, diethyl ether, and acetaldehyde. In fact, TiO2 support with different crystalline phases can result in differences of physico-chemical properties of the catalyst. Therefore, the present work reports on the catalytic behaviors that were altered with different phases of TiO2 in catalytic ethanol dehydration to diethyl ether or ethylene as a major product. To prepare the catalysts, three different phases [anatase (A), rutile (R), and mixed phases (P25)] of TiO2 supports were impregnated with 10 wt% of tungsten (W). It was found that the W/TiO2-P25 catalyst revealed higher activity among other catalysts. At 300 °C, all catalysts can produce the diethyl ether yield of 24.1%, 22.8%, and 10.6% for W/TiO2-P25, W/TiO2-A, and W/TiO2- R catalysts, respectively. However, when the reaction temperature was increased to 400°C, ethylene is the major product. The W/TiO2-P25 and W/TiO2-A catalysts render the ethylene yield of 60.3% and 46.2%, respectively, whereas only 15.9% is obtained from W/TiO2-R catalyst. The most important parameter influencing their catalytic properties appears to be the proper pore structure, acidity, and distribution of W species. [ABSTRACT FROM AUTHOR]

Activated carbon derived from bacterial cellulose (BC-AC) was modified with various amounts of H 3 PO 4 (x wt% P/BC-AC) and used as a catalyst for the selective dehydration of ethanol to ethylene. The BC-AC obtained at a carbonization temperature of 500 °C had a mesoporous structure with surface area and total pore volume of ~1730 m2/g and 1.0 cm3/g, respectively. An increase in the H 3 PO 4 loading from 5% to 40% increased the number of weak acid sites on the catalyst surface, which consequently enhanced ethanol conversion. At the reaction temperature of 400 °C, the modified BC-AC with 30-40 wt% H 3 PO 4 loading (P/BC-AC) gave an ethanol conversion at 100% and an ethylene selectivity of 100%. A high selectivity for diethyl ether (DEE) at ~ 67% at ethanol conversion of ~ 50% was obtained at 200 °C. Stability tests with a time-on-stream of 12 h, at reaction temperatures of 200 and 400 °C, showed that the P/BC-AC catalyst had high thermal stability and stable catalytic activity. Therefore, P/BC-AC was found to be very effective as an inexpensive and environmentally friendly catalyst for ethylene production via ethanol dehydration. Unlabelled Image • Activated carbon (AC) from bacterial cellulose (BC) was modified with H3PO4 loading • P/BC-AC was very effective as an inexpensive and environmentally friendly catalyst • Nanocellulose fiber network structure of BC is beneficial for the development of AC [ABSTRACT FROM AUTHOR]

The incorporation of different metal types (Fe, Al, Mn, Zn, and Cu) on MCM-48 synthesized by the direct sol-gel method was investigated. In this work, tetraethyl orthosilicate (TEOS) was used as a silica source, whereas cetyltrimethylammonium bromide (CTAB) was employed as a structure directing agent. The molar ratio of Silicon/metal was kept at 45. The obtained samples were characterized by XRD, N 2 physisorption, SEM, and UV-VIS techniques. It revealed that Fe, Mn, and Zn incorporated into the framework of MCM-48 resulted in increased thickness of the pore wall, leading to better thermal stability than pure MCM-48. In contrast, the agglomeration of metal oxides, and the nature of aluminum perhaps lead to the decreased thickness of the pore wall in MCM-48 and consequently lower thermal stability. Additionally, the findings indicate that when the thickness of the pore wall is approximately 1.3 nm onward, the thermal stability of metal-incorporated MCM-48 will be improved. [Display omitted] • Type of metals alters thermal stability of MCM-48 synthesized by direct sol-gel method. • Enhancement of MCM-48 by incorporation of Fe, Mn and Zn ions. • Fe-MCM-48 provides the highest thermal stability. • The pore wall thickness ca. 1.3 nm onwards, enhances thermal stability. [ABSTRACT FROM AUTHOR]

• Metallosilicate (Al, Fe, Cu, and Ni) catalysts were synthesized. • The +3 oxidation state of metal bonded in the zeolite structure. • Brønsted acid and redox sites of catalyst handled product distribution. • Oligomerization-cracking route occurred on B 1 Brønsted acid site. • Butene isomerization route reacted on B 2 Brønsted acid site. The metallosilicate catalysts (H-M-silicate, when M = Al, Fe, Cu, and Ni and Si/metal = 20) were synthesized and characterized by XRD, SEM-EDX, XRF, N 2 adsorption and desorption, 27Al MAS NMR, XANES, EXAFS, NH 3 -TPD, NH 3 -IR, and TPO methods to investigate the effect of transition metals substitution in zeolite structure for 1-butene reaction. Only Fe3+ of H-Fe-silicate bonded in the MFI structure like H-ZSM-5, whereas transition metals of H-Cu-silicate and H-Ni-silicate embedded in zeolite matrix over catalyst surface; therefore: the reduction reaction occurred over metal of H-M-silicate catalyst during the reaction. There were two different roles of Brønsted acid site, detected by NH 3 -IR (B 1 at ca. 1470 cm−1 and B 2 at ca. 1660 cm−1). The B 1 Brønsted acid site over micropore surface of catalyst (Si-OH-M) favored oligomerization-cracking route of 1-butene reaction, while butene isomerization route reacted on B 2 Brønsted acid site (Si-OH) over external surface of catalyst (Acid strength: B 1 > B 2) [Display omitted] [ABSTRACT FROM AUTHOR]

Hydrogen sulfide (H 2 S) is a critical problem for biogas applications, such as electricity and heat generation, or the production of different chemical compounds, due to corrosion and toxic effluent gases. The selective catalytic oxidation of H 2 S to S is the most promising way to eliminate H 2 S from biogas due to the lack of effluents, therefore can be considered a green technology. The most extensively used catalysts for H 2 S selective oxidation can be classified in two groups: metal oxide-based catalysts, including vanadium and iron oxides, and carbon-based catalysts. Numerous studies have been devoted to studying their different catalytic performances. For industrial applications, the most suitable catalysts should be less sensitive to the operating parameters like the temperature, O 2 /H 2 S ratio, and H 2 O content. More specifically, for metal oxides and carbon-based catalysts, the temperature and O 2 /H 2 S ratio have a similar effect on the conversion and selectivity, but carbon-based catalysts are less sensitive to water in all operating conditions. • Fe 2 O 3 , V 2 O 5 , and carbon-based catalysts have a similar temperature and O2/H2S ratio sensitive on activity and selectivity. • Carbon-based catalysts are less sensitive to operating conditions when compared with vanadium and iron-based catalysts. • Iron oxide-based catalysts represent an excellent option for future development of catalysts. [ABSTRACT FROM AUTHOR]

• Acid treatment improves catalytic properties of spent RFCC catalyst. • Sulfuric acid treatment increases the ratio of Brønsted to Lewis acid. • Citric acid treatment decreases the ratio of Brønsted to Lewis acid. • Lewis acid sites lead to the formation of short-chain hydrocarbons. • Citric acid-treated catalyst produces more hydrocarbons than that by sulfuric acid. In this study, the reactivation and modification of the spent Residue Fluid Catalytic Cracking (RFCC) catalyst using sulfuric acid and citric acid as acids treatment was evaluated by varying the acid solution concentrations. The effect of acid types and acid-solution concentrations on structural, textural, and acidic properties of spent RFCC catalyst was observed using X-ray diffraction, X-ray fluorescence, N 2 -sorption and pyridine-probed Fourier transform infrared measurements. Catalytic cracking of palm oil was used to evaluate the catalytic activity of the acid-treated catalysts. All the results showed the different beneficial effects of the sulfuric acid- and citric acid- treatments on the physicochemical properties of the modified catalyst with an improvement of surface area and pore volume of catalysts as well as the crystallinity due to the metal and matrix material removal. The sulfuric acid-treated catalysts have higher Brønsted/Lewis (B/L) ratio than the citric acid treatment, while the citric acid-treated catalysts have lower B/L ratio due to the enhancement of Lewis acid site. The acid-treated catalysts showed better performance than the non-treated catalyst. The selectivity of the kerosene-diesel range product fraction increased with the acid concentrations treatment. Graphical abstract [Display omitted]. [ABSTRACT FROM AUTHOR]

Abstract: Three fluorinated bis(phenoxy-imine)titanium complexes bearing ortho-halide substituents on the phenoxy rings [Cl (1), Br (2), I (3)] were synthesized, characterized and evaluated as precatalysts for the polymerization of ethylene in conjunction with methylaluminoxane (MAO) under atmospheric pressure. These C2-symmetric catalysts exhibit high activity toward ethylene polymerization and produce ultra high molecular weight polyethylene (UHMWPE) (M W > 3,000,000). The living polymerization was presented as evidenced by the narrow molecular weight distribution. The living nature of these catalysts is attributed to the interaction of a fluorine atom adjacent to the imine nitrogen and a β-hydrogen of a polymer chain resulting in the suppression of β-hydrogen transfer. The highest activity at 11.65 kg PE/mmol cat h was observed for the polymerization using complex 2. In comparison with complex 1, the more bulky bromo substituents can induce an effective ion-pair separation between the cationic active species and an anionic cocatalyst yielding a higher polymerization rate. However, in case of complex 3 with iodo substituents, the enhancement of the steric congestion at the metal center results in the decreased polymerization activity. [Copyright &y& Elsevier]

Abstract: In this present study, the copolymerization of ethylene and 1-hexene was conducted over the [t-BuNSiMe2(2,7-t-Bu2Flu)]TiMe2 (CGC)/MAO catalyst immobilized on different supports. The effects of Ga and the Lewis acid BCl3 modification of the silica support on the copolymerization behavior were investigated based on catalytic activity and polymer properties. It was found that the silica support modified with BCl3 exhibited the highest activity. However, both Ga and BCl3 modifiers are capable of enhancing the catalytic activity, probably attributed to stronger interaction between the MAO and support together with the acidic sites exerted by the modification which could assist MAO to activate the catalyst during polymerization. Besides, a role of BCl3 as a spacer to keep apart the catalyst on the silica surface was proposed as another probable reason for activity increased. This led to the more homogeneous-like behavior with less effect of support and also caused the higher comonomer incorporation content. Moreover, the results revealed that narrow polymer molecular weight distribution can be achieved by the supported CGC catalyst, especially for acidic modified supports. On the other hand, there was no noticeable effect with regards to the melting temperature and copolymer microstructure of the Ga and BCl3 modification. Therefore, based on the study it may be regarded that the efficient supported CGC catalyst can be accomplished through the acidic modification namely Ga and BCl3. [Copyright &y& Elsevier]

Abstract: In the present study, nanocrystalline χ-Al2O3 were prepared by thermal decomposition of fine gibbsite (χ-GB) and solvothermal method (χ-SV) and employed as supports for preparation of 20wt% Co/Al2O3 catalysts. As compared to the use of γ-Al2O3 with similar BET surface area, Co dispersion and CO hydrogenation activity were higher on the nanocrystalline χ-Al2O3 supported Co catalysts. The transmission electron microscopy (TEM) results revealed that the wrinkled sheets-like structure of γ-Al2O3 was completely destroyed after CO hydrogenation for 6h whereas the spherical particles of χ-SV and plate-like structure of χ-GB were maintained. The H2-temperature program reduction (H2-TPR) also revealed a stronger interaction between cobalt and alumina supports for the Co/χ-Al2O3 catalysts. [Copyright &y& Elsevier]

The decline of bioethanol consumption can jeopardize the future of bioethanol producers. This research aims to design the conversion process of ethanol into a more versatile and valuable product, e.g., diethyl ether (DEE). To produce DEE, two types of ethanol can be utilized. Previously, the anhydrous ethanol was tested experimentally via catalytic dehydration on the Ru-HBZ catalyst. Satisfactory results were obtained, particularly acetaldehyde was not formed in the reaction. Herein, the catalytic experiment is extended using hydrous ethanol as feed resulting in an observable amount of acetaldehyde. These experimental results are implemented in the design of DEE production processes. Three production cases are investigated including the utilization of the anhydrous ethanol (Case I) and the utilization of the hydrous ethanol (Cases II and III). The most profitable process is obtained in Case I with the pay-out period of 4 years and % IRR (percentage of internal rate of return) of 55%. Acetaldehyde appears problematic in the DEE purification in Case II – the process is not profitable if distillation is selected for acetaldehyde removal. By implementing adsorption for the acetaldehyde removal, the process in Case III becomes profitable which is comparable to Case I. In addition, about a 5% reduction in the CO 2 emission and a 7% gain in the energy utilization efficiency are observed in Case III. Finally, the utilization of hydrous ethanol (Case III) can be more attractive when the difference in selling prices of the hydrous and the anhydrous ethanols is more than 50%. • Acetaldehyde was attained if hydrous ethanol was used in catalytic dehydration. • Diethyl ether production was simulated rigorously based on the laboratory results. • Useful techno-economic analysis was conducted for diethyl ether production. • Formation of acetaldehyde negatively influenced the process profitability. • Removal of acetaldehyde via adsorption could enhance the process profitability. [ABSTRACT FROM AUTHOR]

[Display omitted] • Transition metals (Fe, Cu, and Ni) were impregned on Na-ZSM-5 and H-ZSM-5. • Hydrogen transfer index related with Si-(OH)-Al and external silanol group. • Transition metals loading on ZSM-5 enhanced propylene selectivity. • Both medium acid site and metal site participate in propylene production. • Coke content on metal was in the order of nickel > iron > copper. The transition metals: iron (Fe), copper (Cu), and nickel (Ni) were doped on ZSM-5 (Si/Al = 20), Na-ZSM-5, and H-ZSM-5 supports by incipient-wetness impregnation to investigate the influence of transition metals loading on the hydrogen transfer reaction in butene cracking. All samples were characterized by XRD, SEM, XRF, N 2 adsorption and desorption, FT-IR, NH 3 -IR, NH 3 -TPD, UV–VIS, and TPO techniques. It was found that the propylene selectivity increased by the transition metal-loaded catalysts due to the increased medium acid sites on the catalyst surface. The hydrogen transfer index of modified ZSM-5 catalysts was lower than that of the unmodified ones. Moreover, the lack of strong acid sites on ZSM-5 was one of the significant factors that suppressed the formation of light alkanes. Besides, the acidic bridging hydroxyl groups and the external silanol group on ZSM-5 were also active sites during the hydrogen transfer reaction producing light alkanes (propane and butane). Hence, the Na-ZSM-5 exhibited the best performance in terms of propylene yield and catalyst stability. The Ni-loaded ZSM-5 was the least stable catalyst for the reaction due to high coke content and deactivation rate. [ABSTRACT FROM AUTHOR]

The catalytic ethanol dehydration and dehydrogenation over γ-Al 2 O 3 -P catalysts with Pd modification were investigated. The Al 2 O 3 -P is promising to obtain the highest yield of diethyl ether (ca. 38.4%) at 350 °C attributing to increased portion of weak/moderate to strong acid site. Further investigation was conducted with Pd modification on this catalyst. It revealed that the 0.5Pd/Al 2 O 3 -P catalyst produced diethyl ether yield of ca. 33.3% at 350 °C with significant amount of acetaldehyde at low temperature. Increased reaction temperature to 400 °C obtained the highest ethylene yield (ca. 43.7%) with this catalyst because of both acid site and Pd site. Unlabelled Image • Reaction temperature plays the key role on Al 2 O 3 -P catalyst with Pd modification. • Changes in acidity with P and Pd modification correlate with product distribution. • At high temperature, Pd modification seems to have less effect. • It is promising to produce diethyl ether from ethanol dehydration with Al 2 O 3 -P. [ABSTRACT FROM AUTHOR]

In this study, the efficiency of a series of biochar-supported Cu catalysts, biochar-supported Zn catalysts, and biochar-supported Cu-Zn catalysts was determined through bioethanol dehydrogenation to the high-value chemical, acetaldehyde. Each metal, with weight percentages of 10, 20, and 30, and the combination of Cu-Zn, including 10 wt% of Cu and Zn, 15 wt% of Cu - 5 wt% of Zn, and 15 wt% of Cu and Zn, were fully loaded onto biochar using an incipient wetness impregnation technique. Subsequently, all biocatalysts were subjected to bioethanol dehydrogenation reactions in a temperature range of 200-400 °C. The optimum metal loading for the catalyst was found to be the combination of 15 wt% Cu and 15 wt% Zn. This catalyst resulted in a reasonable acetaldehyde yield of 56.2%, an initial bioethanol conversion of 57.3%, and a very high acetaldehyde selectivity of 98.1% at a mild reaction temperature of 300 °C and ambient pressure. These results were attributed to the optimal concentration of weak-medium acid and medium base sites. Active acid and base sites were identified through temperature-programmed desorption of ammonia (NH 3 -TPD) and temperature-programmed desorption of carbon dioxide (CO 2 -TPD), respectively. Furthermore, the reaction stability test of the best biocatalyst (15Cu-15Zn/BB) was proven by maintaining this reaction at the same temperature (300 °C) for 10 h. However, the catalytic performance slightly decreased due to the coke formation of Cu species.

The aim of this research was to examine the effect of strontium content in the MgAlO catalyst for the catalytic ethanol reaction on the product distribution. The structure of the catalysts and the actual amount of strontium on the catalysts were verified using XRD and ICP techniques, respectively. The acid and basic strength characteristics of catalysts were examined using NH 3 -TPD and CO 2 -TPD techniques, respectively. The strontium content was found to influence the textural properties and the acidic and basic characteristics of the catalysts, leading to differences in product selectivity and ethanol conversion. The MgAlO catalyst with 1.9 wt % strontium provided the maximum ethylene and butanol selectivity, probably due to the presence of appropriate medium acidic and strong basic sites. All catalysts can efficiently produce ethylene by a dehydration reaction and acetaldehyde by a dehydrogenation reaction. Acetaldehyde selectivity was dominant with increased strontium loading., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)

The deterioration behaviors of Cu/ZnO/Al 2 O 3 (CZA) catalysts upon different Cu contents were elucidated. The fresh and spent catalysts after being used in CO and CO 2 hydrogenation at 250 °C under atmospheric pressure were properly characterized using various techniques including X-ray powder diffraction, X-ray photoelectron spectroscopy, and temperature-programmed reduction for the changes of metal sites, while the textural and chemical properties and carbon deposition on spent CZA catalysts were analyzed by N 2 physisorption, energy-dispersive X-ray spectroscopy, and temperature-programmed oxidation. During the hydrogenation reaction for both CO and CO 2 , the unstable Cu 0 site on the spent CZA catalyst having a low Cu loading (sCZA-L) was oxidized to CuO and the aggregation of metal crystallite sites (Cu-ZnO and ZnO) was observed. Moreover, the amount of carbon deposition on sCZA-L (ca. >2%) is higher than the spent CZA catalyst having a high Cu loading (sCZA-H, ca. <0.5%). These phenomena led to a decrease in the surface area and the blockage of active sites. These findings can be determined on the catalytic deactivation and the obvious decrease in the catalytic activity of the CZA catalyst having a low Cu content (CZA-L, Cu:Zn = 0.8)., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)

The MgAlO catalyst was obtained from thermal decomposition of the MgAl-LDH catalyst having Mg/Al molar ratio of 5. The catalytic Guerbet reaction of ethanol was investigated to determine the effect of WHSV and nitrogen flow rate on butanol production and product distribution. It was performed in a fixed-bed microreactor under continuous flow of vaporized ethanol mixed with N 2 . The MgAlO catalyst had high total basic sites and high total acid sites that were crucial for ethanol Guerbet reaction. The MgAlO catalyst showed the highest butanol selectivity at 300℃ under WHSV = 3.10 h -1 and nitrogen flow rate = 3,600 mL/h, and the highest butanol yield at 400℃ under WHSV = 3.10 h -1 and nitrogen flow rate = 900 mL/h. It can be summarized that in order to enhance the butanol yield, the low WHSV is preferred to increase the contact time of ethanol and catalyst under moderate temperature.

The ternary Cu/ZnO/Al 2 O 3 (CZA) catalysts having different Cu loading were prepared by the co-precipitation method. Then, they were used in CO and CO 2 hydrogenation to produce methanol under atmospheric pressure at 250 °C. The high Cu loading CZA catalyst (CZA-H) resulted in the enhancement of structural features and textural properties (e.g., BET surface area and the crystallite size of copper species). Furthermore, the conversion of CO and CO 2 over CZA-H catalyst was apparently higher than that of the CZA-L (low Cu loading) catalyst. The major product of CO hydrogenation obtained from both catalysts was methanol, whereas in CO 2 hydrogenation, the main product was CO. Deactivation of catalysts was also crucial during CO and CO 2 hydrogenation. Therefore, the spent catalysts were determined to identify the nature of carbon formation. It revealed that amorphous and graphitic cokes were present. These cokes have different mechanisms in the elimination from the surface leading to influencing the deactivation process. The spent CZA-L was found to have higher carbon content, which was around 2.3% and 3.1% for CO and CO 2 hydrogenation, respectively. Besides the amorphous coke, the graphitic coke was also observed in CZA-L after time on stream for 5 h., Competing Interests: The authors declare no conflict of interest., (© 2021 The Author(s).)

This study aims to convert ethanol to higher value-added products, particularly diethyl ether and ethylene using the catalytic dehydration of ethanol. Hence, the gas-phase dehydration of ethanol over Al 2 O 3 -HAP catalysts as such and modified by addition of palladium (Pd) in a microreactor was evaluated. The commercial Al 2 O 3 -HAP catalyst was first prepared by the physical mixing method, and then, the optimal ratio of the Al 2 O 3 -HAP catalyst (2:8 by wt %) was impregnated with Pd to develop a new functional catalyst to alter surface acidity. Based on the results, the combination of Al 2 O 3 and HAP catalysts generated significant quantities of weak acid sites which demonstrates an enhancement in catalytic activity. In addition, Pd modification in the optimal composition ratio of the Al 2 O 3 -HAP catalyst extremely increased the amount of weak acid sites as well as weak acid density due to the synergistic effect between the Pd and Al 2 O 3 -HAP catalyst that are supposed to suggest the active sites in the reaction. Among all catalysts, the Al20-HAP80-Pd catalyst displayed brilliant catalytic performance in the course of diethyl ether yield (ca. 51.0%) at a reaction temperature of 350 °C and ethylene yield (ca. 75.0%) at a reaction temperature of 400 °C having an outstanding stability under time-on-stream for 10 h. This is recognized to the combination of the effects of weak acid sites (Lewis acidity), small amount of strong acid sites, and structural characteristics of the catalytic materials used., Competing Interests: The authors declare no competing financial interest., (© 2021 The Authors. Published by American Chemical Society.)

In the present work, the palladium (Pd) modification and supporting effect of W/TiO 2 catalysts on catalytic ethanol dehydration to ethylene and diethyl ether were investigated. The Pd modification with different sequence of Pd and W impregnation on the catalysts was prepared by the incipient wetness impregnation technique. The catalyst characterization and activity testing revealed that the different sequence during impregnation influenced the physicochemical properties and ethanol conversion of catalyst. The differences in structure and surface properties were investigated by XRD, BET, SEM, EDX, XPS and NH 3 -TPD. Upon the reaction temperature between 200 to 400°C, it was found that the conversion increased with increasing of temperature for all catalysts. The Pd incorporated into catalysts enhanced the ethanol conversion depending on the sequence of impregnation. At low temperature (ca. 200 to 300°C), diethyl ether is a major product and the Pd modification over W/TiO 2 catalyst resulted in increased diethyl ether yield. This is because an increase of ethanol conversion was obtained with Pd modification, while diethyl ether selectivity did not change. This can be attributed to the higher amount of weak acids sites present after Pd modification into catalyst. Among all catalysts, the PdW/TiO 2 catalyst (coimpregnation) achieved the highest diethyl ether yield of 41.4% at 300℃. At high temperature (ca. 350 to 400°C), ethylene is the major product. The W/Pd/TiO 2 catalyst (with sequential impregnation of Pd on TiO 2 followed by W) exhibited the highest ethylene yield of 68.1% at 400°C. It can be concluded that the modification of Pd onto W/TiO 2 upon different sequence of Pd and W impregnation can improve the diethyl ether and ethylene yield in catalytic ethanol dehydration.

The high ethylene selectivity exhibited on the zirconia-activated-carbon bi-support catalyst is investigated by experiment and density functional theory-based (DFT) analysis. This bi-support catalyst systems prepared by the physical mixing method for the tungsten catalyst show a significant increase in ethylene selectivity up to 90% compared to the zirconia single support system (~58%) during the ethanol dehydration reaction. Besides, the optimal percent weight ratio of zirconia to activated carbon, which results in the highest ethanol conversion is 50:50. The DFT-based analysis is used to investigate high ethylene selectivity in the bi-support system. It shows that the WO 5 /zirconia is the most stable model for the zirconia single-support tungsten catalyst represented by the zirconia (101) facet of the tetrahedral phase. The carbon atoms were added to the WO 5 /zirconia to model the tungsten catalyst on the bi-support system. The Bader charge analysis is carried out to determine the electron transfer in the catalyst. The bonding between ethylene and the WO 5 active site on the catalyst is weakened when the system is bi-support, where the added carbon atoms on the catalyst in the ZrO 2 region decrease the ethylene adsorption energy. Thus, the desorption and the selectivity of ethylene are promoted. The decrease in adsorption energy can be explained via the analysis of the projected density of states (PDOS) profiles of atom involving the adsorption. It was found that the added carbon in the ZrO 2 region induces the electron transfer from the ethylene molecule to the surface, especially to the ZrO 2 region. The depletion of the electron around the ethylene molecule weakens the bonds, thus, promote desorption. Hence, the advantages of using the bi-support system in the tungsten catalyst are that the catalyst exhibit (1) high conversion due to the zirconia support and (2) high ethylene selectivity due to the added carbon promoting the desorption of ethylene via the induction of electron from an ethylene molecule to surface.

This research investigated pyrolysis as a potential method to manage plastic waste in Sichang Island, Thailand. Pyrolysis was chosen to convert waste plastic into fuel oil using Al-Si catalysts derived from cogon grass. The study consisted of three stages. The first stage determined the composition of the waste plastics found in Sichang Island. High-density polyethylene (48%) comprised the highest proportion of the waste plastics, followed by low-density polyethylene (22%), polyethylene terephthalate (13%), polypropylene (10%), and polystyrene (7%). In the second stage, the Al-Si catalysts were prepared from cogon grass ( Imperata cylindrica (L.) Beauv) by treating it with acid and calcination. The optimum conditions to extract silica from cogon grass through acid treatment were heating at 700 °C for 2 h, which yielded 97.7% of amorphous silica with a surface area of 172 m 2 /g and a pore volume of 0.43 cc/g. This amorphous silica was combined with an aluminum precursor to form Al-Si catalysts with 20-80 wt% of Al-Si. The results showed that the surface area of the catalyst increased with increasing aluminum content. The optimum ratio was 60 wt% of Al-Si with a surface area of 200 m 2 /g. In the final stage, the catalytic properties of the previously prepared Al-Si catalysts in the pyrolysis of waste plastics were evaluated. The catalyst enhanced the plastic cracking process and the oil yield while decreasing the reaction time. The optimum ratio of 60% Al-Si to 10% waste plastic provided the maximum oil yield of 93.11% and the minimum reaction time of 20 min. The results showed that catalytic cracking with 60% Al-Si contributed to a high quantity of oil yield, similar to using a commercial Al-Si catalyst. The results of this research will be applied as an alternative method of recycling plastic for sustainable waste management in Sichang Island.

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 (H 2 O, 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.

Activities during ethylene/1-hexene copolymerization were found to increase using the mixed titania/silica-supported MAO with rac-Et[Ind]2ZrCl2 metallocene catalyst. Energy Dispersive X-ray spectorcopy (EDX) indicated that the titania was apparently located on the outer surface of silica and acted as a spacer to anchor MAO to the silica surface. IR spectra revealed the Si-O-Ti stretching at 980 cm(-1) with low content of titania. The presence of anchored titania resulted in less steric hindrance and less interaction due to supporting effect.