Metta Chareonpanich

Direct synthesis of dimethyl ether from CO2 hydrogenation over Cu–ZnO–ZrO2/SO42−–ZrO2 hybrid catalysts: effects of sulfur-to-zirconia ratios

Sulfated zirconia catalysts were prepared by a direct sulfation method and were admixed with a CuO–ZnO–ZrO2 catalyst for the direct synthesis of DME from CO2 hydrogenation. The effects of sulfur-to-zirconia ratios on the physicochemical properties, activity, selectivity and stability of the catalysts were investigated. The sulfur loading content significantly influenced the structure and surface chemistry of the catalysts. The addition of a small amount of sulfur (5–15 wt%) created numerous mesopores on the catalyst surface, remarkably enhancing the surface area and total pore volume. However, at high sulfur loading (20–30 wt%), the mesopores tended to merge and form a larger pore. The detailed characterization by FT-IR, XANES and NH3-TPD reveals that the sulfated zirconia with low sulfur content (5–10 wt%) mainly contained weak acid sites and acted as Lewis acids. Increasing the sulfur loading (15–30 wt%) resulted in the formation of Bronsted acid sites, thus increasing the acid strengths. The sulfated zirconia catalyst with 20 wt% sulfur loading achieved a superior DME productivity of 236 gDME kgcat−1 h−1 at a reaction temperature and pressure of 260 °C and 20 MPa. However, after 75 h of a time-on-stream experiment, the sulfated zirconia catalyst lost approximately 16.9% of its initial activity while a commercial H-ZSM-5 catalyst was more stable as only a 2.85% reduction was observed.

Production of aromatic hydrocarbons from Mae-Moh lignite

Lignite from Mae-Moh basin in Thailand was used as raw feed to produce value-added chemicals, especially aromatic hydrocarbons. It was found that the hydropyrolysis of Mae-Moh lignite in atmospheric pressure of hydrogen gas is suitable for aromatic hydrocarbon production. For the hydropyrolysis of Mae-Moh lignite at 600 °C and the heating rate of 15 °C/s, 15 wt.% (dry, ash-free basis; daf) of benzene, toluene and xylenes (BTX) and decalin, tetralin and naphthalene (DTN) was produced. To enhance the yield of aromatic fractions, the upgrading of coal volatile over HY zeolite at 500 °C was investigated. The yield of BTX and DTN was 14 wt.% (daf). The attempt was made to convert aliphatic hydrocarbons to aromatic products by reforming of aliphatic products from the above hydropyrolysis/upgrading process over H-ZSM-5 zeolite. The calculated yield of BTX and DTN after this treatment was 20 wt.% (daf).

Effect of Catalysts on Yields of Monocyclic Aromatic Hydrocarbons in Hydrocracking of Coal Volatile Matter

The use of catalysts for upgrading volatile matter from hydropyrolysis of Millmerran coal was investigated. The activities of Mo, W, CoMo, NiMo and NiW catalysts, all loaded on Al2O3, together with various zeolites were tested for the hydrocracking of coal volatile matter under high hydrogen pressure. The activities of the metal-loaded catalysts reached maxima at a moderate metal loading. Of all the catalysts, USY-zeolite exhibited the highest activity. The BTX yield reached 14.0 wt% (daf) or 16.7 wt% (carbon basis) at a pyrolysis temperature of 800°C and a post-cracking temperature of 600°C under a hydrogen pressure of 5 MPa.

Catalytic hydrocracking reaction of nascent coal volatile matter under high pressure

Abstract The volatile matter evolved during the rapid pyrolysis of coal was hydrocracked over catalysts in the last stage to increase the yield of valuable products like benzene, toluene and xylenes (BTX). The effects of gas atmosphere, coal type, pyrolysis temperature, hydrocracking temperature and catalyst type were examined. The highest BTX yield, 10.4 wt%(daf), was obtained under the following conditions: Millmerran coal, H 2 pressure of 5 MPa, primary pyrolysis temperature of 800 °C, secondary hydrocracking temperature of 620 °C and with a NiMoS catalyst.

Multimetallic catalysts of RuO2–CuO–Cs2O–TiO2/SiO2 for direct gas-phase epoxidation of propylene to propylene oxide

RuO2–CuO/SiO2 catalysts doped with Cs2O and TiO2 were investigated for the direct gas phase epoxidation of propylene to propylene oxide (PO) using molecular oxygen under atmospheric pressure. The optimal catalyst was achieved at Ru/Cu/Cs/Ti = 8.3/4.2/0.6/0.8 by weight and total metal loading of 21 wt% on SiO2 support. NH3 and CO2 temperature programmed desorption measurements of RuO2–CuO/SiO2 catalyst modified with Cs2O showed that the surfaces acidity decreased, resulting in enhanced PO selectivity. The addition of TiO2 increased the PO formation rate by promoting the synergy effect between RuO2 and CuO. Using the Box–Behnken design of experiments on the RuO2–CuO–Cs2O–TiO2/SiO2 catalyst, an extraordinarily high optimal PO formation rate of 3015 gPO h−1 kgcat−1 was obtained with a feed comprised of O2/C3H6 at a volume ratio of 3.1 and (O2 + C3H6)/He at a volume ratio of 0.26, all at 272 °C and 34 cm3 min−1. To the knowledge of the authors, this is the highest PO formation rate ever reported for direct propylene epoxidation via O2.

Effect of bimodal porous silica on particle size and reducibility of cobalt oxide

In this study, the effect of bimodal porous silica (BPS) on particle size and reducibility of cobalt oxide has been investigated. Unimodal porous silica (UPS) was used for comparison purposes. Both silica supports were impregnated with an aqueous solution of cobalt nitrate to obtain cobalt loadings of about 10 wt%. Pore structure, specific surface area, morphology and cobalt oxide crystallite size of the cobalt oxide loaded on porous silicas were systematically characterized by means of N2-sorption, X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The reduction behavior profiles and the activation energy for the reducibility of the cobalt oxide were studied by dynamic thermal gravimetric under flow of H2. The average particle size of cobalt oxide loaded on the BPS sample was revealed to be slightly larger than that loaded on the UPS sample, likely because cobalt oxide particles were distributed both on mesopores and macropores. The reduction temperatures of the cobalt oxide loaded on the BPS sample were found to be evidentially lower than those of the cobalt oxide loaded on the UPS sample.

Preparation of Mesoporous Silica from Rice Husk Ash: Effect of Depolymerizing Agents on Physico-Chemical Properties

The aim of this work was to prepare mesoporous silicas derived from rice husk ash (RHA) using three different depolymerizing agents; glycerol, 1,3 propanediol and 1,4 butanediol. The reaction of RHA with different depolymerizing agents was carried out between 200-250°C for 2 hrs. The solution was then hydrolyzed with deionized water to obtain gels. After a few washing step, gels were oven-dried and calcined at 500 °C for 24 hrs. Prepared mesoporous silicas were then characterized using Nitrogen adsorption-desorption measurement, FTIR, TGA, SEM, XRD and XRF. The percent hydrophobicity was determined based on the amount of moisture absorbed using TGA. It was shown that RHA reacted with depolymerizing agents above 200°C to form gels, which, after hydrolysis and calcination, still maintained the mesoporous characteristics. The BET and SEM results indicated that the RHA reacted with 1,3 propanediol had highest pore volume (0.95 cm3/g) and specific surface area (129.30 m2/g) compared to RHA reacted with glycerol and 1,4 butanediol. The distribution of pores computed from BJH desorption branch was also more uniform. FTIR indicated that there was no significant change in the chemical structure of RHA reacted with different depolymerizing agents. The residual C-H bands were found in FTIR spectra for all prepared mesoporous silicas. TGA thermograms confirmed the existence of organic residues (below 2 %wt), which might result from incomplete elimination even after calcination. This was found to be an important factor affecting the hydrophobic property of the reacted RHA. The hydrophobicity of RHA may be tailored by controlling depolymerizing agents and organic residues. Depolymerizing agents with longer carbon chains also favoured the hydrophobic characteristics.

Remarkable Increase of BTX Yield by Zeolite Catalyst in the Hydrocracking of Coal Volatile Matter

Publisher Summary This chapter discusses the use of zeolite catalyst in the hydrocracking of coal volatile matter to yield benzene, toluene, xylenes (BTX). Coal can be economically utilized in the production of high value-added chemicals, such as BTX and phenol, cresols, xylenols (PCX), followed by using the residue as the energy sources. Continuous catalytic reaction is carried out by pyrolyzing coal at 800°C in a free-fall reactor and evolved volatile matter hydrotreated at 600°C by using ultrastable Y-zeolite, which is active in the production of BTX from coal volatile matter. The deactivation of catalyst is not observed under the present conditions even in the continuous operation. The use of model compounds showed the high activity of zeolite catalyst in the hydrogenation and hydrocracking reactions.

Hydrophilic and Hydrophobic Mesoporous Silica Derived from Rice Husk Ash as a Potential Drug Carrier

This work describes the preparation of mesoporous silica by the green reaction of rice husk ash (RHA) with glycerol, followed by the modification and the potential use as a drug carrier. The reaction was carried out at 215 °C for 2 h. The solution was further hydrolyzed with deionized water and aged for various times (24, 48, 120, 360, 528 and 672 h) before calcinations at 500 °C for 24 h. Further treatment of prepared mesoporous silica was performed using trimethylmethoxysilane (TMMS) to obtain hydrophobic Mesoporous silica. For all synthesized silicas, silica contents were as high as 95 wt %, whereas organic residues were less than 3 wt %. RHA-glycerol showed the highest specific surface area with smallest pore diameter (205.70 m2/g, 7.46 nm) when aged for 48 h. The optimal hydrolysis-ageing period of 120 h resulted in 500.7 m2/g specific surface area, 0.655 cm3/g pore volume and 5.23 nm pore diameter. The surface modification of RHA-glycerol occurred through the reaction with TMMS as confirmed by FTIR (Fourier-transform infrared spectroscopy). Ibuprofen was selected as a model drug for the adsorption experiments. The adsorption under supercritical CO2 was carried out at isothermal temperature of 40 °C and 100 bar; % ibuprofen loading of TMMS modified mesoporous silica (TMMS-g-MS) was 6 times less than that of mesoporous silica aged for 24 h (MS-24h) due to the hydrophobic nature of modified mesoporous silica, not surface and pore characteristics. The release kinetics of ibuprofen-loaded mesoporous silicas were also investigated in vitro. The release rate of ibuprofen-loaded MS-24h was much faster than that of ibuprofen-loaded TMMS-g-MS, but comparable to the crystalline ibuprofen. The slower release rate was attributed to the diffusion control and the stability of hydrophobic nature of modified silica. This would allow the design of a controlled release drug delivery system.