Investigation of the Selective Production of Ethylene from Propylene Over Small-Pore Zeolites.

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.

Effects of Zeolite Supports on the Production of Fuel-Range Hydrocarbons in the Hydrotreatment of Various Vegetable Oils with Platinum-Based Catalysts.

The effects of catalyst supports on catalyst performance in the hydrotreatment of vegetable oils (to produce fuel-range hydrocarbons such as gasoline, jet fuel, and diesel) were investigated, using three types of zeolites (ZSM-5, HY, and zeolite-beta (BEA)) that differ in their silica/alumina ratios. Structural characterization of the catalysts was performed using ICP, XRD, BET, TEM, and NH3-TPD. Catalytic tests were carried out in a fixed-bed reaction system at 400 °C and 50 bar. In the hydrotreatment of soybean oil, higher conversions into liquid hydrocarbons and fuel-range hydrocarbons were found when supports with lower Si/Al2 ratios were used. Specifically, Pt/BEA (Si/Al2 = 25) produced the highest conversion into liquid products (72%) and the highest selectivity for hydrocarbons in the jet fuel (46%) and diesel (51%) fuels. A Pt loading amount of 3 wt% in this catalyst gave the best catalytic performance because of the optimal balance between acidic and metallic sites. Finally, the kinds of vegetable oils in the hydrotreatment performance over Pt/BEA (Si/Al2 = 25) affected the order; waste-cooking oil > jatropha oil > soybean oil.

Hydroupgrading of Bio-Oil Over PtMg/KIT-6 Catalysts.

The objective of this study is to evaluate the catalytic potential of PtMg/Al-KIT-6 during the hydroupgrading of a mixture composed of C15-C18 alkane as a model compound of bio-oil obtained by a hydrodeoxygenation of palm oil. Al-KIT-6 was prepared through a post-alumination method using KIT-6, after which platinum and magnesium precursors were impregnated onto the synthesized Al-KIT-6. PtMg/Al-KIT-6 catalysts were shown to have a well-arranged mesoporous structure, a large surface area, and a large pore size. The jet-fuel yield (55-59%) in the hydroupgrading of the long-chain n-alkane mixture over PtMg/Al-KIT-6 catalysts was much higher than that over the PtMg/KIT-6 catalyst, which could be ascribed to the higher number of acid sites of the PtMg/Al-KIT-6 catalysts. The highest isomer selectivity of the PtMg/Al-KIT-6(20) catalyst can be attributed to the strong acidity as well as the abundance of acid sites. PtMg/Al-KIT-6 catalysts can be effective catalysts for producing jet fuel through the hydroupgrading of bio-oil.

Dimerization of Ethylene to Butenes Over Ordered Mesoporous Silica SBA-15 Supported Ni-Al Catalysts with Different Morphologies.

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.

Selective Production of p-Xylene from Dimethylfuran and Ethylene Over Tungstated Zirconia Catalysts.

p-Xylene (PX) is an important large-volume commodity chemical in the petrochemical industry. Therefore, research on producing PX from bio-mass-derived resources is a considerable interest in relation to future alternative technologies. Recently, a new potential route for the direct and selective production of bio-based PX was reported, referred to as the Diels-Alder cycloaddition of biomassderived 2,5-dimethylfuran (DMF) and ethylene followed by the dehydration of an intermediate. Here, we prepared tungstated zirconia (WOx-ZrO2) materials at different calcination temperatures and times as solid acid catalysts for PX production. From structural analyses and measurements of the surface acidity, the WOx-ZrO2 was found to be composed of mesopores with high surface acidity within the optimum calcination temperature and time range. This WOx-ZrO2 catalyst exhibited high catalytic activity upon the cycloaddition of DMF with ethylene as compared to commercial beta zeolite and previously reported silica-alumina catalysts.

Effect of Silica Content on Production of p-Xylene from Dimethylfuran/Ethylene Over Mesoporous SiO2­Al2O3 Catalysts.

Mesoporous SiO2­Al2O3 (SA) catalysts with different SiO2 contents were prepared, for the selective production of p-xylene from dimethylfuran/ethylene through the combination of cycloaddition and dehydrative aromatization reactions, by a co-precipitation method. For comparison, commercial SiO2­Al2O3 and ZSM-5 zeolites (Si/Al2 = 30, Si/Al2 = 80) were also employed as catalysts in the same reaction. The pore size of the catalysts played an important role in determining the catalytic performance in the production of p-xylene. Among the catalysts tested, the order of the yield and production rate of p-xylene was as follows: mesoporous SA > commercial SiO2­Al2O3 > commercial ZSM-5. In the mesoporous SA catalysts in particular, p-xylene yields showed a volcano-shaped trend with respect to the catalyst's SiO2 content. The SA-60 catalyst, with SiO2 = 52.3, showed the highest yield (75%) and production rate (57.7 mmol/g-cat · h) because of a catalyst structure with moderate pore size, which prevented side reactions.

Aromatization of Ethanol Over Desilicated ZSM-5 Zeolites: Effect of Pore Size in the Mesoporous Region.

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.

Selective Ring Opening of 1-Methylnaphthalene Over NiW-Supported Catalyst Using Dealuminated Beta Zeolite.

Nanoporous Beta zeolite was dealuminated by weak acid treatment for reducing the acidity. Bi-functional catalysts were prepared using commercial Beta zeolites and the dealuminated zeolites for acidic function, NiW for metallic function. 1-Methylnaphthalene was selected as a model compound for multi-ring aromatics in heavy oil, and its selective ring opening reaction has been investigated using the prepared bi-functional catalysts with different acidity in fixed bed reaction system. The dealuminated Beta zeolites, which crystal structure and nanoporosity were maintained, showed the higher SiO2/Al2O3 ratio and smaller acidity than their original zeolite. NiW-supported catalyst using the dealuminated Beta zeolite with SiO2/Al203 mole ratio of 55 showed the highest performance for the selective ring opening. The acidity of catalyst seemed to play an important role as active sites for the selective ring opening of 1-methylnaphthalene but there should be some optimum catalyst acidity for the reaction. The acidity of Beta zeolite could be controlled by the acid treatment and the catalyst with the optimum acidity for the selective ring opening could be prepared.

Mesoporous Carbon Supported Rh Nanoparticle Catalysts for the Production of C2+ Alcohol from Syngas.

Uniform rhodium nanoparticles (NP) with three different particle sizes (1.9, 2.4, and 3.6 nm) were prepared via a polyol method with rhodium (III) acetylacetonate, poly(vinylpyrrolidone) with different concentrations of sodium citrate. The prepared Rh nanoparticles were impregnated into the ordered mesoporous carbon supports with two different pore structures (2D hexagonal and 3D cubic). The prepared Rh nanoparticle-supported ordered mesoporous carbons (OMCs) were introduced as catalysts for the CO hydrogenation of syngas to produce C2 higher alcohols. The characteristics of the Rh nanoparticle-supported ordered mesoporous carbons catalysts were analyzed through transmission electron microscopy, powder X-ray diffraction, and N2 physisorption analysis. The catalytic tests of the catalyst were performed using a fixed-bed reactor. The results revealed that the catalysts exhibited the different catalytic activity and selectivity of higher alcohols, which could be attributed to the different OMC structures, the nanoparticle size of Rh, and aggregation of Rh nanoparticles during the reaction.

The Effect of K and Acidity of NiW-Loaded HY Zeolite Catalyst for Selective Ring Opening of 1-Methylnaphthalene.

Bi-functional catalysts were prepared using HY zeolites with various SiO2/Al2O3 ratios for acidic function, NiW for metallic function, and K for acidity control. 1-Methylnaphthalene was selected as a model compound for multi-ring aromatics in heavy oil, and its selective ring opening reaction was investigated using the prepared bi-functional catalysts with different levels of acidity in a fixed bed reactor system. In NiW/HY catalysts without K addition, the acidity decreased with the SiO2/Al2O3 mole ratio of the HY zeolite. Ni1.1W1.1/HY(12) catalyst showed the highest acidity but slightly lower yields for the selective ring opening than Ni1.1W1.1/HY(30) catalyst. The acidity of the catalyst seemed to play an important role as the active site for the selective ring opening of 1-methylnaphthalene but there should be some optimum catalyst acidity for the reaction. Catalyst acidity could be controlled between Ni1.1W1.1/HY(12) and Ni1.1W1.1/HY(30) by adding a moderate amount of K to Ni1.1W1.1/HY(12) catalyst. K0.3Ni1.1W1.1/HY(12) catalyst should have the optimum acidity for the selective ring opening. The addition of a moderate amount of K to the NiW/HY catalyst must improve the catalytic performance due to the optimization of catalyst acidity.

Solar Carboxylation Using CO2: Interfacially Synthesized Flexible Covalent Organic Frameworks Film as a Photocatalyst for Highly Selective Solar Carboxylation of Arylamines with CO2.

Carbon dioxide (CO2) conversion into value-added chemicals/fuels by utilizing solar energy is a sustainable way to mitigate our dependence on fossil fuels and stimulate a carbon-neutral economy. However, the efficient and affordable conversion of CO2 is still an ongoing challenge. Here, we report an interfacially synthesized visible-light-active Ni(II)-integrated covalent organic frameworks (TaTpBpy-Ni COFs) film as a photocatalyst for efficient CO2 conversion into carboxylic acid under ambient conditions. Notably, the TaTpBpy-Ni COFs film showed excellent photocatalytic activity for the carboxylation of various arylamines with CO2 to the corresponding arylcarboxylic acid via C-N bond activation under solar-light irradiation. Moreover, this carboxylation protocol exhibits mild reaction conditions and good functional group tolerance without the necessity of using stoichiometric metallic reductants. This work shows a benchmark example of not only the interfacially synthesized COFs film used as a photocatalyst for solar-light energy utilization but also the selective solar chemical production system of arylcarboxylic acid directly from CO2.

Hydroconversion of n-dodecane over nanoporous catalysts.

Platinum catalysts impregnated on different nanoporous materials, Meso-MFI, Si-SBA-15 and AI-SBA-15, were synthesized, and the hydroconversion of n-dodecane over these catalysts was performed. The catalytic characteristics were analyzed by Brunauer-Emmett-Teller surface area, X-ray diffraction, N2-adsorption-desorption and temperature programmed desorption of NH3. The effects of operation parameters, such as temperature and pressure, on the catalytic activities were investigated. The catalytic activities were affected considerably by the acidic properties of the catalysts, temperature and pressure. Higher acidity, high temperature and low hydrogen pressure resulted in higher hydroconversion and facilitated hydrocracking. The weak acidity, low temperature and high hydrogen pressure resulted in lower hydroconversion and higher selectivity to i-dodecane.

Synthesis of mesoporous SAPO-34 molecular sieves and their applications in dehydration of butanols and ethanol.

Microporous SAPO-34 molecular sieves were hydrothermally synthesized with microwave irradiation in the presence of tetraethylammonium hydroxide (TEAOH) as a template. SAPO-34 molecular sieves with mesoporosity were also prepared in the presence of carbon black as a hard template. By increasing the content of the carbon black template in the synthesis, the mesopore volume increased. Dehydration of alcohols (butanols and ethanol) was carried out with the synthesized SAPO-34 molecular sieves, and the lifetime of the catalysts for the dehydration reaction increased as the mesoporosity increased. Moreover, the performance of the microporous catalyst synthesized with microwave was better than that of the catalyst obtained with conventional electric heating. The relative performance of the catalytic dehydration may be explained by the mesoporosity and the crystal size. Therefore, it may be concluded that small-sized SAPO-34 molecular sieves with high mesoporosity can be produced efficiently with microwave irradiation in the presence of carbon black template, and the molecular sieves are effective in the stable dehydration of alcohols.

Effect of the preparation method of support on the aqueous phase reforming of ethylene glycol over 2 wt% Pt/Ce0.15Zr0.85O2 catalysts.

The effect of catalyst support on the aqueous phase reforming of ethylene glycol over supported 2 wt% Pt/Ce0.15Zr0.85O2 catalysts have been investigated. Various types of Ce0.15Zr0.85O2 mixed oxides were prepared by hydrothermal precipitation (CZH), modified precipitation (CZM), co-precipitation (CZC), sol-gel (CZS) methods, respectively. Catalysts were characterized by XRD, N2 sorption analysis, and cyclohexane dehydration for relative metal dispersion. The support effect on the activity of 2 wt% Pt/Ce0.15Zr0.85O2 catalysts with different preparation method was given as follows: CZH < CZM < CZC < CZS. Pt/Ce0.15Zr0.85O2 (CZS) catalyst showed good catalytic activity for APR reaction due to its high metal dispersion and reducibility. The effect of reaction conditions such as reaction temperature, weight hourly space velocity (WHSV) was also studied. The hydrogen production rate and hydrogen yield increased in proportion to the reaction temperature and corresponding system pressure, whereas WHSV did not affect.

Synthesis of mesoporous SAPO-34 zeolite from mesoporous silica materials for methanol to light olefins.

Mesoporous SAPO-34 zeolites were synthesized by using as-prepared mesoporous silica material as both silica source and mesopore tailor. The mesoporous SAPO-34 zeolite materials thus obtained are characterized by a series of different techniques, including poweder X-ray diffraction pattern, nitrogen physisorption analysis, scanning electron micrograph, temperature programmed desorption of ammonia, and inductively coupled plasma atomic emission spectrometry. The resultant mesoporous SAPO-34 crystals exhibit sphere-like particle with zeolite layer units. The mesopore size distribution and particle size can be changed by amounts of silica source and water. The methanol-to-olefins (MTO) reactions using these mesoporous SAPO-34 zeolites are carried out with a fixed-bed reactor. Catalytic tests exhibit that the mesoporous SAPO-34 zeolite materials show high catalytic activity compared with the conventional SAPO-34 for MTO reaction. The better catalytic activity and longer life time of the mesoporous SAPO-34 catalysts in MTO are mainly due to the existence of the mesoporosity of SAPO-34 with small particle size.

Structural influence of ordered mesoporous carbon supports for the hydrogenation of carbon monoxide to alcohols.

A series of ordered mesoporous carbon materials (OMCs) possessing well-ordered nanoporosity with different mesopore structures were synthesized by the template-synthesis route. Two different pore strucutes (2-dimensional hexagonal and 3-dimensional cubic structures) and two different framework-configurations (rod-type and hollow-type carbon frameworks) are prepared by using the two different silica templates and synthetic conditions. The ordered mesoporous carbon supported promoted-rhodium catalysts were preparted by an incipient wetness method. The promoted Rh-OMC catalysts are tested by a fixed bed reactor for the catalytic conversion of syngas-to-alcohols. The characteristics of the promoted Rh-OMCs catalysts were scrutinized through a series of different techniques, including transmission electron microscopy (TEM), powder X-ray diffraction (XRD), and N2 sorption analysis, and the catalytic performance was tested in a fixed-bed reactor. It was found that the promoted Rh-OMC catalysts exhibited the different catalytic activity and selectivity of alcohols, which could be attributed to the size of metal nanoparticles being confined by the different mesostructure of OMCs.

Compositional dependence of Co- and Mo-supported beta zeolite for selective one-step hydrotreatment of methyl palmitate to produce bio jet fuel range hydrocarbons.

For producing a drop-in bio jet fuel, one-step hydrotreatment, which includes deoxygenation, isomerization and cracking in one step, is essential to overcome the typical biofuel drawbacks due to high oxygen content, out of jet fuel range hydrocarbons, and low isomerization degree. Herein, Co- or/and Mo-supported Beta(25) zeolites with various Co/Mo ratios were prepared as transition metal-supported zeolite catalysts without the need for sulfidation of conventional transition metal catalysts. Based on the catalyst characterization, the Co/Mo ratio alters the metal phase with the appearance of CoMoO4 and the altered Co metal phase strongly influences the acidic properties of Beta(25) by the formation of Lewis (L) acid sites with different strengths as Co3O4 and CoMoO4 for strong and weak L acid sites, respectively. The catalytic activities were investigated for hydrotreatment of methyl palmitate as a biofuel model compound of fatty acid methyl esters. Primarily, Co is required for deoxygenation and Mo suppresses overcracking to enhance the yield of jet fuel range hydrocarbons. The Co/Mo ratio plays an important role to improve the C8-C16 selectivity by modifying the acidic properties to inhibit excessive cracking. Co5Mo10/Beta(25) achieved the best catalytic performance with the conversion of 94.2%, C8-C16 selectivity of 89.7 wt%, and high isomer ratio of 83.8% in organic liquid product. This unique modification of acidic properties will find use in the design of optimal transition metal-supported zeolite catalysts for selective one-step hydrotreatment to produce bio jet fuel range hydrocarbons.

Oxidation of refractory sulfur compounds over Ti-containing mesoporous molecular sieves prepared by using a fluorosilicon compound.

Titanium containing mesoporous molecular sieve (Ti-MMS) catalysts were studied for the oxidative desulfurization of refractory sulfur compounds. Ti-MMS catalysts were synthesized from fluorosilicon compounds and Ti with the hydrolysis reaction of H2SiF6 in an ammonia-surfactant mixed solution. The solid products were characterized by XRD, XRF, nitrogen adsorption, and diffuse reflectance UV-vis spectroscopy. Effects of Ti loading and oxidant/sulfur mole ratio, and sulfur species on ODS activity were investigated.

Physicochemical characteristics of SAPO-34 molecular sieves synthesized with mixed templates as MTO catalysts.

In the present work, a variety of SAPO-34 catalysts have been prepared using various templates such as a single or mixtures of tetraethylammonium hydroxide (TEAOH), morpholine, diethylamine (DEA), triethylamine (TEA), dipropylamine (DPA), isopropylamine (IPA) and Diethanolamine (DEtA). It is shown that crystal morphology and physicochemical properties were affected by the kinds of templates and mixture contents. Especially, inexpensive SAPO-34 catalyst with good crystal properties and catalytic performance was obtained by using mixed template of DEA and TEAOH. Through N2 isotherm, XRD, SEM, NH3 TPD and 29Si-NMR techniques, the effect of mixed template on the crystal morphology, acidity and Si distribution were investigated. Catalytic activity and life stability of SAPO-34 in MTO reaction was improved by using mixed template because of the distinction of the crystal size, acidity and Si distribution.

Ordered Mesoporous Carbon Supported Rh Nanocubes as Catalysts for Higher Alcohol Synthesis.

Among higher alcohol synthesis (HAS) catalysts, Rh-based catalysts show catalytic activity for the selective production of ethanol and C2+ oxygenates, because both CO dissociation and CO insertion are available on the surface of Rh. Theoretical studies have indicated that the activation barrier of CO on the Rh(100) surface is lower than other Rh surfaces, and this can lead to higher catalytic activity for HAS on Rh-based catalysts. Uniform and specifically size-controlled Rh nanocubes (NCs) with Rh(100) planes were prepared via a polyol synthesis route, and introduced onto ordered mesoporous carbon (OMC) supports. The Rh NC/OMC materials were employed for HAS from syngas to investigate the effect of the Rh crystal surface. TEM analysis and catalytic reactions clearly demonstrated that Rh NCs in the OMC support can improve the catalytic performance for HAS by both enhancing CO dissociation and suppressing methane formation. Moreover, additional chain growth reactions for the synthesis of C3 and C4 alcohols were induced by the Rh NCs on OMC supports.