Propane is selectively converted to propylene via propane dehydrogenation (PDH) process for an on-purpose propylene usage. Due to regional market demands, olefin interconversion for propylene-to-ethylene (PTE) is required to control the supply-demand of light olefins. Our concern centers on combining the PDH and PTE reactions to achieve a simple catalytic process for selective production of light olefins from propane. Herein, converting propane to light olefins is investigated via cascade and series PDH-PTE reactions over highly selective two catalysts. From the catalytic results, selectively produced propylene over a PDH catalyst (Cr2O3/Al2O3) from propane was readily converted to other light olefins over a PTE catalyst (modified ZSM-5). The modified ZSM-5 as the PTE catalysts was further studied in the both cascade and series reactions with different reaction conditions in order to find an optimum reaction condition for high olefin yield and selectivity with low methane selectivity as well as to investigate the influence of process parameters on the catalytic activity. The AHFS treated ZSM-5 (AHFS-ZSM-5) as the PTE catalyst in PDH-PTE series reaction exhibited a superior light olefin yield (50.7 wt%) and olefin selectivities up to 76.7 wt% (26.9 wt% ethylene, 38.0 wt% propylene, and 11.8 wt% butenes) with low methane selectivity (4.27 wt%) at 550 degrees C, WHSV 7 h(-1), and propylene partial pressure in the PDH model feed 0.025 MPa.

The selective production of ethylene from the direct conversion of propylene (propylene-to-ethylene, PTE) was examined for the first time using various types of 8-membered ring (8-MR) zeolite materials with different pore structures. Among these 8-MR zeolites, SSZ-13 zeolite with a threedimensional chabazite structure exhibited the highest ethylene yield. To increase the ethylene selectivity further, the PTE reactions were conducted over SSZ-13 zeolite external surface modifications with silylation or phosphorus. The external surface modifications enhanced the ethylene selectivity due to the passivation of external acid sites. The surface-modified SSZ-13 catalyst exhibited the highest selectivity to ethylene, at more than 90% at 450 °C, a WHSV of 0.33 h-1, and a propylene particle pressure of 0.1 MPa.

The conversion of Y zeolites having wide silica/alumina ratio (SAR, 5.1–80) into SSZ-13s was carried out in the presence of N,N,N-dimethylethylcyclohexylammonium (DMCHA) ion, as an organic structure directing agent (OSDA). SSZ-13 zeolites could be obtained from siliceous Y zeolites; however, another phase, analcime (ANA) was obtained when aluminous Y zeolites (SAR: 5.1–12) were converted. Sodium silicate was used not only to successfully convert the aluminous Y zeolites into SSZ-13s but also to increase the SAR of the obtained SSZ-13 zeolites. The synthesis of SSZ-13 with DMCHA was possible in the absence of any seed, which is advantageous in the viewpoint of both the expense and convenience of the synthesis. Moreover, the synthesized SSZ-13s were utilized in the direct conversion of ethylene-to-propylene (ETP). Moderately siliceous SSZ-13s (SAR: 18–24) showed better performance in ETP than aluminous or siliceous SSZ-13s. DMCHA-derived SSZ-13 was also competitive or better in ETP than SSZ-13s prepared with other reported templates including N,N,N-trimethyl-1-adamantanamine hydroxide (TMAda-OH). For example, the maximum propylene yield in ETP over SSZ-13s (with similar SAR of 15–19) prepared with choline chloride, tetraethylammonium hydroxide (TEA-OH), TMAda-OH, and DMCHA-Br were 51, 61, 65 and 68%, respectively. Based on the syntheses and ETP reactions, DMCHA ion can be recommended as a versatile/inexpensive OSDA for the conversion of Y (with wide SARs) into SSZ-13 zeolites which can be effective in ETP reaction. However, further work is required to understand the reason of the competitiveness of the DMCHA-derived SSZ-13 and the effect of the SAR on the propylene yield in ETP.

For the first time, beta zeolites (IZA code: BEA with 12-membered rings, having a wide range of SiO2/Al2O3) were converted into SSZ-13s (IZA code CHA, having 8-membered rings) in the presence of external silica source (here, Na2SiO3) and N, N, N-trimethyl-1-adamantanamine hydroxide as a structure directing agent. Na2SiO3 was essential for the successful conversion when the parent zeolite beta was Al-rich. The conversion of beta into SSZ-13 zeolite can be explained by the relative stabilities of beta and SSZ-13 zeolites, where pore size had more dominant role than the framework density. The obtained SSZ-13s were highly porous, had both weak and strong acidic sites and composed of tetrahedral aluminum. Finally, the synthesized SSZ-13s were applied in the direct conversion of ethylene-to-propylene (ETP) as a solid catalyst. The results showed that the SSZ-13s, converted from beta, were better or competitive in ETP (especially in the stable conversion of ethylene) against the SSZ-13 (synthesized by using tetraethylammonium hydroxide) that had showed very competitive performances earlier in ETP.

The SSZ-13 zeolite was synthesized via seed-assisted method without an organic structure-directing agent (OSDA) from sodium silicate, sodium aluminate, and seed crystals using a wide range of silica/alumina ratios (SARs) in the precursor gels. The SAR of the SSZ-13 was quite high (10) when the SAR of the precursor gel was 40, which was the optimum ratio for high crystallinity. The zeolite was steamed at a high temperature to further increase the SAR via dealumination. The crystal structure of SSZ-13 was stable during steaming because of its high SAR, quite different from another SSZ-13 zeolite obtained from the conversion of zeolite Y in K+ ion in the absence of an OSDA. Steaming at 800 degrees C and further washing with acid led not only to an increase in the SAR up to 21, but also to a steady increase in porosity. However, the concentration of acid sites, especially strong ones, decreased steadily with increasing steaming time, and octahedral aluminum was removed successfully after adequate steaming. Both pristine and steamed SSZ-13 zeolites were applied to the ethylene-to-propylene (ETP) reaction. With increased steaming time, both the stability of the ethylene conversion and the maximum propylene yield increased. Compared to conventional SSZ-13 zeolites synthesized using expensive OSDAs, adequately steamed SSZ-13 zeolites were competitive for catalyzing the ETP. The exceptional performance of the SSZ-13 zeolite obtained in this study may be understood in terms of its adequate SAR and the decreased number of acid sites (especially strong acid sites), which might be active for hydrogen transfer and ethylene oligomerization. Therefore, it could be suggested that the SSZ-13 zeolite synthesized without an OSDA can be effective in the ETP reaction when steam-treated under suitable conditions. (C) 2018 Elsevier Inc. All rights reserved.

A series of ordered mesoporous silica (OMS) SBA-15 supports with different morphologies were prepared by different synthetic methods to investigate the effect of the characteristics of the morphology of OMS on the ethylene dimerization outcomes. After additions of Ni and Al species into the SBA-15 support, a dimerization reaction of ethylene was performed using a fixed-bed reactor. Rod-type Ni-Al-SBA-15 with a small micron size showed better catalytic performance compared to those of the other catalysts. From these catalytic results, the particle size and morphology of a SBA-15 support critically influenced the catalytic activities and lifetimes of the dimerization catalysts. The optimum reaction pathway in the Ni-Al-SBA-15 catalyst enhanced the overall catalytic performance due to the suppression of the further oligomerization of ethylene and butenes. Moreover, ethylene dimerization was investigated over the rod-type Ni-Al-SBA-15 catalyst to discover an optimum reaction condition. The maximum yield of butenes was 24.7% at 300 °C at 11.5 bar with a WHSV of 1.5 h-1.

The conversion of Y-zeolites having a wide silica/ alumina ratio (SAR, 5.2-80) into other zeolites was attempted using tetraethylammonium hydroxide (TEA-OH) as an organic structure directing agent (SDA). Depending on the SARs of the Y-zeolites, different zeolite phases, either pure or mixed, were obtained from the same reaction precursors (TEA-OH, Y zeolite, etc.) and conditions. To investigate the obtained phase selectivity and phase transformation, the effects of the reaction temperature and times were evaluated. The phase selectivity or transformation could be explained using the framework density or pore size of zeolites. Zeolites Y having SARs of 12 and 30 were also applied to examine the effects of alkali metal ions (AMIs; Li+, Na+, K+, and Cs+) on the conversion. The results showed that AMIs also have a dominant influence on the phase of the obtained zeolite, and Na+ was the most effective for the production of the SSZ-13 zeolite. The protonated SSZ-13 zeolites (obtained from zeolite Y with an SAR of 12 or 30) were employed in the direct conversion of ethylene-to-propylene (ETP). The results showed that these SSZ-13 s were better or competitive in ETP against SSZ-13 s synthesized from various organic SDAs or SSZ-13 s prepared under SDA-free conditions. Therefore, TEA-OH can be suggested as a competitive SDA to synthesize SSZ-13 zeolites, especially for ETP, from Y zeolites.

Two types of mesoporous perovskite-type oxides (Meso-PTOs) were synthesized by combining a templated synthesis and a citrate complex method. The Meso-PTO catalysts exhibited superior catalytic activity in the higher alcohols synthesis from syngas compared to the bulk-PTO, likely due to the increased dispersion of active sites on the high surface of the Meso-PTOs. Moreover, the Meso-PTOs show higher productivity for C-3 and C-4 alcohols as well as C2+ oxygenates. Among the two Meso-PTOs developed here, the mesoporous LaFe0.7Cu0.3O3 catalyst was capable of significant suppression of the methanation reaction and better selectivity to higher alcohols compared to the mesoporous LaCo0.7Cu0.3O3 catalyst. (C) 2017 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.

This study is the first to examine the selective production of ethylene from propylene (propyleneto-ethylene, PTE) with using various structural types of zeolites. The catalytic performances of these zeolite catalysts were tested in a continuous fixed-bed reactor. Among these zeolite catalysts, ten-membered ring zeolites with three-dimensional pore structures (ZSM-5 and ZSM-11) exhibited stable catalytic performances with considerable ethylene selectivity compared to other zeolite catalysts. The phosphorous-modified ZSM-5 catalyst exhibited the highest ethylene selectivity of more than 70% with moderate propylene conversion of 36.3% at a low propylene space velocity and a partial pressure condition.

This study is the first to examine the selective production of ethylene from propylene (propylene-to-ethylene, PTE) with using various structural types of zeolites. The catalytic performances of these zeolite catalysts were tested in a continuous fixed-bed reactor system with respect to ethylene selectivity and catalyst stability during the overall reaction period. Among these zeolite catalysts, ten-membered ring zeolites with three-dimensional pore structures (ZSM-5 and ZSM-11) exhibited stable catalytic performances with considerable ethylene selectivity compared to other zeolite catalysts. The ZSM-5 zeolite, thus selected, was further studied in the PTE reaction with different silica-alumina ratios (Si/Al-2, SARs), a surface modification with phosphorus, and under different reaction conditions in order to investigate the effect of acidity, surface properties, and process variables on the catalytic activity as well as to additional improve the ethylene selectivity. From these studies, the PTE reaction was found to depend strongly on the reaction condition, SAR and surface P modification in the ZSM-5 zeolite. The phosphorous-modified ZSM-5 catalyst exhibited the highest ethylene selectivity of more than 70% with moderate propylene conversion of 36.3% at a low propylene space velocity and a low partial pressure condition.

SSZ-39 and mordenite zeolites were obtained from the conversion of zeolite Y in the presence of the same reaction precursors (organic templates, NaOH, water, etc.) under a wide range of reaction conditions. The applied templates were N,N-dialkyl-2,6-dimethyl-piperidinium-OH and -I (alkyl: ethyl or methyl). Curiously, SSZ-39 and mordenite were obtained from hydroxides and iodides, respectively, showing firstly the importance of the anion in the selective crystallization of zeolites. Reactions were also performed at the same set of pH values (achieved by adding small amounts of NaOH to the iodide-based precursors) to investigate the effect of basicity; the results did not vary appreciably with the pH of the synthesis precursors. Based on the phase conversion (MOR - > AEI or ANA with increasing reaction time and pH), the selective formation of SSZ-39 and mordenite from hydroxides and iodides, respectively, could be explained in terms of zeolite-promoting and -preventing anions (hydroxide and iodide, respectively). The phase conversion of zeolites could be explained on the basis of the maximum pore size of zeolites, rather than the framework densities. The obtained zeolites (SSZ-39 and mordenite), in their protonated forms, were employed in ethanol dehydration and direct ethylene-to-propylene conversion, and the results showed that the two zeolites have potential application in acid catalysis. In particular, the SSZ-39 with an AEI structure can be applied in the direct production of propylene from ethylene or ethanol. (C) 2016 Elsevier Inc. All rights reserved.

Pressure-dependent structural and chemical changes of the metal organic framework (MOF) compound MIL-47(V) have been investigated up to 3 GPa using different pore-penetrating liquids as pressure transmitting media (PTM). We find that at 0.3(1) GPa the terephthalic acid (TPA) template molecules located in the narrow channels of the as synthesized MIL-47(V) are selectively replaced by methanol molecules from a methanol ethanol water mixture and form a methanol inclusion complex. Further pressure increase leads to a gradual narrowing of the channels up to 1.9(1) GPa, where a second irreversible insertion of methanol molecules leads to more methanol molecules being inserted into the pores. After pressure release methanol molecules remain within the pores and can be removed only after heating to 400 degrees C. In contrast, when MIL-47(V) is compressed in water, a reversible replacement of the TPA by H2O molecules takes place near 1 GPa. The observed structural and chemical changes observed in MIL-47(V) demonstrate unique high pressure chemistry depending on the size and type of molecules present in the liquid PTM. This allows postsynthetic nonthermal pressure-induced removal and insertion of organic molecules in MOFs forming novel and stable phases at ambient conditions.

•SSZ-13 zeolites with wide Si/Al ratios (SARs) were obtained from Y zeolites.•Microwave was applied to produce SSZ-13 zeolites in short reaction time.•Direct conversion of ethylene to propylene (ETP) was done with SSZ-13s.•SSZ-13s with moderate SARs showed stable ethylene conversion.•SSZ-13s with low SARs were effective to have high propylene yield.

Mesoporous ZSM-5 zeolites were obtained from microporous ZSM-5 by desilication using aqueous NaOH solutions, and their catalytic activity in the aromatization of ethanol was investigated in order to understand the effects of pore size, in the mesoporous region, on the product distribution and stability of the catalysts. Mesopores generally enhanced the selectivities towards aromatics and stability for aromatization. Mesopores with a maximum pore diameter of around 13 nm were the most effective in the aromatization process (especially for benzene and toluene), suggesting that pore-diameter optimization is necessary for efficient catalysis such as aromatization.

The adsorptive removal of p-arsanilic acid (ASA) from water using zeolitic imidazolate framework-8 (ZIF-8) materials was investigated for the first time. The adsorption kinetics and adsorbed amount of ASA were improved by introducing mesoporosity into the pristine ZIF-8 structure. The high adsorption capacity of mesoporous ZIF-8 for ASA and facile regeneration of the used adsorbent show that mesoporous ZIF-8 has potential applications in the adsorptive removal of organoarsenic compounds such as ASA. Based on the adsorption results at various pH values and the surface charges on ZIF-8s, the adsorption mechanism of ASA on ZIF-8s can be explained by electrostatic interactions between the positively charged ZIF-8 surface and the anionic forms of ASA. (C) 2015 Elsevier B.V. All rights reserved.

Adsorptive denitrogenation (ADN) was carried out by adsorption of indole (IND) and quinoline (QUI) over metal-organic frameworks (MOFs) including acidic UiO-66-SO3H for the first time. The adsorbed amount of IND increased with increasing content of -SO3H in UiO-66. The favorable effect of the -SO3H group on the adsorptive removal of IND could be explained by hydrogen bonding between the O of -SO3H and the H of IND, which was firmly supported by the adsorption of pyrrole and methylpyrrole and by theoretical calculations. The application of an -SO3H group in the adsorptive removal of neutral IND is meaningful since neutral nitrogen-containing compounds are not easy to remove and since UiO-66-SO3H is reusable after simple washing with ethanol. The expected increase in QUI adsorption (due to acid-base interaction) with acidic -SO3H was observed when QUI was present at low concentrations (<similar to 400 ppmw). This favorable contribution of acidic -SO3H to the adsorption of basic QUI was also supported by calculations for the adsorption of one QUI molecule on the -SO3H group of UiO-66. Interestingly, the adsorbed amount of QUI decreased with increasing content of -SO3H in UiO-66 when the QUI concentration was high (initial concentration of 1000 ppmw). One of the reasons for the negative effect of acidic -SO3H on QUI adsorption might be the presence of only one H atom in -SO3H or steric hindrance (due to decreased pore space), although detailed works are needed to support this.

A metal-organic framework (MOF), MIL-100(Fe), was impregnated with a Lewis acidic salt, AlCl3, in order to prepare an acidic adsorbent. The adsorbent was used in adsorptive denitrogenation (ADN) of model fuels to investigate the effect of the Lewis acidity of the composite adsorbent. To provide more in-depth understanding of the interaction/adsorption mechanism, a basic quinoline (QUI) and a neutral indole (IND) were utilized as adsorbates. A sulfur-containing compound, benzothiophene (BT), was also used along with the two nitrogen-containing compounds (NCCs) in order to investigate the selectivity of the adsorption of the NCCs. The maximum adsorption capacity of AlCl3/MIL-100(Fe) for QUI was 17% higher than that of the pristine MIL-100(Fe), despite an 8% reduction of the surface area upon loading the MOF with AlCl3. In contrast, the performance of the AlCl3/MIL-100(Fe) adsorbents in the adsorption of neutral IND decreased with the content of AlCl3 due to little interaction between the acidic adsorbent and neutral IND and the low porosities of the modified adsorbents. Therefore, the investigation shows that MOFs impregnated with Lewis acidic materials such as AlCl3 can be effectively used for adsorptive removal of basic NCCs by means of an acid-base interaction. It can also be concluded that MOFs, when modified suitably with specific functional materials, can be used for specific and improved adsorption. (C) 2014 Elsevier B.V. All rights reserved.