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Ruthenium catalysts anchored on three distinct supports (γ‐Al2O3, γ‐χ‐Al2O3, and silica [SiO2]) are tested for ethanol dehydration at 250°C. The catalytic materials were characterized using X‐ray diffraction (XRD), N2 physisorption, ammonia temperature programmed desorption (NH3‐TPD), FTIR, UV‐Vis spectroscopy, in situ UV‐Vis spectroscopy, H2 temperature programmed reduction experiments (H2‐TPR), and thermogravimetric analysis (TGA) after reaction. The activity was correlated to the number of acid sites present in the support. However, the addition of Ru increased the activity for alumina supported catalysts. Product selectivity depends on the nature of the acid sites present on the catalytic material, with ruthenium playing a critical role on the acid properties of the catalysts. [ABSTRACT FROM AUTHOR]

MgCl2-SiO2/TiCl4 Ziegler-Natta catalysts for ethylene polymerization were prepared by impregnation of MgCl2 on SiO2 in heptane and further treatment with TiCl4. MgCl2·nEtOH adduct solutions were prepared with various EtOH/MgCl2 molar ratios for preparation of the MgCl2-supported and MgCl2-SiO2-supported catalysts in order to investigate the effect on polymerization performance of both catalyst systems. The catalytic activities for ethylene polymerization decreased markedly with increased molar ratios of [EtOH]/[MgCl2] for the MgCl2-supported catalysts, while for the bi-supported catalysts, the activities only decreased slightly. The MgCl2-SiO2-supported catalyst had relatively constant activity, independent of the [EtOH]/[MgCl2] ratio. The lower [EtOH]/[MgCl2] in MgCl2-supported catalyst exhibited better catalytic activity. However, for the MgCl2-SiO2-supported catalyst, MgCl2 can agglomerate on the SiO2 surface at low [EtOH]/[MgCl2] thus not being not suitable for TiCl4 loading. It was found that the optimized [EtOH]/[MgCl2] value for preparation of bi-supported catalysts having high activity and good spherical morphology with little agglomerated MgCl2 was 7. Morphological studies indicated that MgCl2-SiO2-supported catalysts have good morphology with spherical shapes that retain the morphology of SiO2. The BET measurement revealed that pore size is the key parameter dictating polymerization activity. The TGA profiles of the bi-supported catalyst also confirmed that it was more stable than the mono-supported catalyst, especially in the ethanol removal region. [ABSTRACT FROM AUTHOR]

The present research focuses on investigation of the catalytic behaviors of MgCl2-SiO2/TiCl4/THF Ziegler-Natta (ZN) catalysts_ with fumed SiO2 variously treated with silane compounds. The non-treated silica (NTS) and other silicas treated with dimethylsilicone fluid (TSDMSF), dimethyldichlorosilane (TSDMDCS), and hexamethyldisilazane (TSHMDS) were employed. It was found that the Cat-TSDMDCS and Cat- TSHMDS exhibited remarkably high activity, even with a similar bulk Ti content as the others. Thus, the more powerful technique of XPS analysis was used to determine the Ti content at the catalyst surface. It was evident that the surface concentrations of Ti could play important role on the catalyst activity. As the result, the increased activity is proportional to the surface concentration of Ti. It was mentioned that the change in surface concentration of Ti with different treated silica can be attributed to the effect of silane spacer group and steric hindrance. The distribution of Ti on the external surface can be also proven by means of EDX mapping, which matched the results obtained by XPS analysis. The treated silica also resulted in narrower molecular weight distribution (MWD) due to the more uniform active sites produced. There was no significant change in polymer morphology upon treatment of the silica. [ABSTRACT FROM AUTHOR]

The present research focuses on investigation of the catalytic behaviors of MgCl2-SiO2/TiCl4/THF Ziegler-Natta (ZN) catalysts_ with fumed SiO2 variously treated with silane compounds. The non-treated silica (NTS) and other silicas treated with dimethylsilicone fluid (TSDMSF), dimethyldichlorosilane (TSDMDCS), and hexamethyldisilazane (TSHMDS) were employed. It was found that the Cat-TSDMDCS and Cat- TSHMDS exhibited remarkably high activity, even with a similar bulk Ti content as the others. Thus, the more powerful technique of XPS analysis was used to determine the Ti content at the catalyst surface. It was evident that the surface concentrations of Ti could play important role on the catalyst activity. As the result, the increased activity is proportional to the surface concentration of Ti. It was mentioned that the change in surface concentration of Ti with different treated silica can be attributed to the effect of silane spacer group and steric hindrance. The distribution of Ti on the external surface can be also proven by means of EDX mapping, which matched the results obtained by XPS analysis. The treated silica also resulted in narrower molecular weight distribution (MWD) due to the more uniform active sites produced. There was no significant change in polymer morphology upon treatment of the silica. [ABSTRACT FROM AUTHOR]

Abstract: Here, the copolymerization of ethylene/1-octene with zirconocene/dMMAO catalyst using different pore sized silica-based supports was investigated. It revealed that the large pored silica [SiO2 (LP)] exhibited the highest polymerization activity due to both highest amount of available active sites present along with the moderate interaction between dMMAO and the support. The strong interaction between dMMAO and the support as proven by TGA analysis apparently resulted in dramatically decreased polymerization activity for the bimodal pored silica–alumina [Si–Al (BP)]. The copolymers produced were further characterized by means of DSC and 13C NMR. Although they exhibited the similar triad distribution, the degree of 1-octene insertion was different. [Copyright &y& Elsevier]

Abstract: In this present study, the use of silica and zirconia as a support for zirconocene/MAO catalyst for copolymerization of ethylene/1-olefin (1-hexene, 1-octene, and 1-decene) was investigated. First, MAO as the cocatalyst was impregnated onto the support. Then, copolymerization of ethylene/1-olefin was performed. It was found that the use of zirconia support showed promising activities compared to those of the silica. Increased activities can be attributed to higher amount of [Al]MAO present on the zirconia support coupled with strong interaction between the Osupport–Alcocatalyst linkage. In addition, the use of zirconia also resulted in higher degree of 1-olefin insertion and decreased T m of copolymers produced. [Copyright &y& Elsevier]

Abstract: In the present study, the characteristics of cobalt (Co) dispersed on mixed nano-SiO2–ZrO2 supports were investigated. The samples were prepared by impregnation of the cobalt precursor onto the various mixed nano-SiO2–ZrO2 supports. After calcination, the samples were characterized with different techniques. XRD revealed that the Co oxide species were highly dispersed on the various supports without changes in morphologies. The reduced Co metal atoms determined by the H2 chemisorption apparently increased with the use of mixed nano-SiO2–ZrO2 supports. It was suggested that the presence of mixed nano-SiO2–ZrO2 supports facilitated the reduction of cobalt oxide species. [Copyright &y& Elsevier]

Abstract: In the present study, the characteristics and catalytic properties of [t-BuNSiMe2Flu]TiMe2/dMMAO catalyst dispersed on various supports towards ethylene/1-octene copolymerization were investigated. First, the dMMAO was impregnated onto various supports, such as SiO2, SiO2–TiO2, and TiO2. Then, copolymerization of ethylene/1-octene was conducted with and without the presence of supports in different solvent mediums. The SiO2–TiO2 support exhibited the highest activity among all the supports. The high activity observed for the SiO2–TiO2 support can be attributed to fewer interactions between the support and dMMAO, as confirmed by XPS and TGA results. The different solvents can alter the nature of the catalyst in two ways: (i) changing the interactions between the support and cocatalyst and/or (ii) changing the form of active species i.e., active ion-pair and solvent-separated ion-pair, as seen in the homogeneous system. However, there was no effect with regards to activity of the solvent mediums employed for the homogeneous system. It is worth noting that the Ti-complex made possible high incorporation of 1-octene having the triblock (OOO) and diblock (EOO) copolymers. The properties of copolymers by means of GPC, DSC, and 13C NMR were further discussed in more detail. [Copyright &y& Elsevier]

Abstract: In the present study, the catalytic behaviors of mixed TiO2-SiO2-supported cobalt (Co) Fischer–Tropsch (FT) catalysts via carbon monoxide (CO) hydrogenation were investigated. The various weight ratios of TiO2/SiO2 were prepared, then consequently impregnated with the cobalt precursor. After calcination, the various samples were characterized using XRD, Raman spectroscopy, scanning electron microscopy/energy dispersive X-ray (SEM/EDX), transmission electron microscopy (TEM), temperature-programmed reduction (TPR), and H2 chemisorption. The characteristics of various samples were further discussed in more details. Based on the reaction study, it revealed that the presence of titania in the mixed supports resulted in decreased activities dramatically. However, longer chain hydrocarbons such as C2–C5 can be obtained substantially with increasing the amounts of titania in the mixed supports. [Copyright &y& Elsevier]

The present study showed enhanced activities of ethylene/1-octene copolymerization via TiO2-SiO2 mixed oxides-supported MAO with a zirconocene catalyst. It was proposed that titania was decorated on silica surface and acted as a spacer to anchor MAO to the silica support resulting in less steric hindrance and less interaction on the support surface. [ABSTRACT FROM AUTHOR]

Effect of SiCl4-modified silica/MAO-supported Et[Ind]2ZrCl2 metallocene catalyst on copolymerization of ethylene with α-olefins was investigated. Effect of SiCl4 on activities was diminished with higher α-olefins. Molecular weights of copolymers decreased with SiCl4 modification. SiCl4 modification also resulted in a lower molecular weight distribution. 13C NMR showed that ethylene incorporation in all systems gave copolymers with similar triad distribution. In addition, a narrow branching distribution can be achieved with SiCl4 modification. [Copyright &y& Elsevier]

The silica-supported MAO was in situ- and ex situ immobilized with zirconocene catalyst to produce ethylene copolymers. The in situ catalytic system exhibited higher activities compared with the ex situ one. The ethylene/1-hexene (EH) copolymerization showed the highest activities for both catalytic systems. 13C NMR revealed that the copolymers produced in all systems were random copolymers. In addition, the in situ system resulted in narrow molar mass distributions (MMD) for all copolymers indicating a uniform catalytic site present. [Copyright &y& Elsevier]

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]

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]

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]