PDF Publication Title:
Text from PDF Page: 004
Table 1 Elemental composition and N2 sorption characteristics of untreated and the alkaline treated samples M. Bjørgen et al. / Applied Catalysis A: General 345 (2008) 43–50 45 Sample Si/Ala NH3 capacityb (mmol/g) SBET (m2/g) Sextc (m2/g) Smicroc (m2/g) Vtotald (mL/g) Vmicroc (mL/g) PARENT 46 0.35 0.05M 39 0.37 0.20M 27 0.36 313 142 171 372 192 180 419 213 206 0.28 0.09 0.39 0.09 0.37 0.10 a ICP-AES. b NH3-TPD. c t-Method. d Volume adsorbed at p/p0 = 0.99. 5008Cfor2hinN2 flowandthencooledto1508C.NH3 inHewas adsorbed at 150 8C for 30 min followed by purging with N2 at the same temperature for 3 h in order to remove loosely adsorbed NH3. The remaining, strongly adsorbed NH3 was then desorbed by heating to 550 8C. Quantification of the total acidity, which may correspond to all both Brønsted sites, Lewis sites, and other defect sites acidic enough for strong adsorption of NH3 at 150 8C was performed by trapping the desorbed NH3 in boric acid followed by titration with HCl. Textural properties were determined by N2 adsorption at 196 8C on a Quantachrome Autosorb 3B instrument. The sample (50–100 mg) was outgassed at 300 8C for 16 h prior to the N2 adsorption measurement. Scanning electron micrographs were recorded without deposi- tion of any conducting material or layer using a FEI Quanta 200 FEGESEM instrument. X-ray powder diffraction (XRD) patterns were recorded on a Siemens D5000 diffractometer using Cu Ka1 radiation (l = 1.541 A ̊ ). A Pawley fitting was performed using the Materials Studio software supplied by Accelrys. Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) spectra of the powdered samples were recorded at room temperature at 2 cm1 resolution using a commercial cell from Harrick Scientific. Prior to the experiments, the samples were pretreated at 450 8C in a flow of dry N2. The spectra were recorded on a BioRad FTS 60 spectrometer, equipped with a MCT detector. 2.4. Catalytic testing All catalytic reactions were performed in a fixed bed Pyrex reactor (3 mm i.d.). Methanol was fed by passing the carrier gas (He) through a saturation evaporator kept at 17 8C. The resulting partial pressure of methanol was 110 mbar, and the total pressure equaled atmospheric pressure. The reaction temperature was measured with a stainless steel sheathed thermocouple (1.4 mm diameter) placed in the catalyst bed. The reaction temperature was 370 8C. All experiments were performed with a total gas flow through the reactor of 35 mL/min and 40 mg of catalyst, resulting in a weight hourly space velocity (WHSV) of 8 grams of methanol per gram catalyst per hour (g g1 h1). Product analysis was performed using gas chromatography. Quantitative effluent composition was determined using an on-line Carlo Erba GC6000 Vega with flame ionization detector (FID) equipped with a Supelco SPB-5 column (60 m 0.53 mm 3 mm). The following tem- perature program was employed: isothermal at 50 8C for 6 min, heating at 15 8C/min to 260 8C, isothermal at 260 8C for 5 min. 3. Results and discussion 3.1. Catalyst characterization The elemental composition as determined with ICP-AES and the total acidity as determined by NH3-TPD/titration in the untreated sample (designated PARENT) and the two alkaline- treated samples are reported in Table 1 together with the N2 sorption data. The Si/Al ratio of the PARENT sample is somewhat higher than that of the synthesis gel. The desilicated samples contain more aluminum than the PARENT sample, and this effect is much more pronounced for the 0.20M sample than for the 0.05M sample. This trend is in agreement with previous reports [11] and the notion that the desilication procedure leads predominantly to a removal of Si. No trend is seen for the NH3 capacities or total acidities (meaning all sites acidic enough for strong adsorption of NH3 at 150 8C) among the samples, as the results listed in Table 1 are virtually identical for all three samples. The NH3 adsorption capacity of 0.35 mmol/g seen for the PARENT sample may be converted into an equivalent Si/Al ratio by assuming that only Al in framework positions gives rise to acidity, and an Si/Al value of 47 is thus found, which is a perfect match with the result for this sample from ICP-AES. Indeed, previous studies have shown that the quantification of acidity from this NH3-TPD procedure corresponds well with the concentration of tetrahedrally coordinated aluminum as measured with 27Al NMR [27], but this apparently holds only for the unmodified sample in this study. The discrepancies between the elemental composi- tions and the total acidities for the desilicated samples clearly indicates that not all of the Al present in these samples give rise to acidity, and it seems plausible that part of the Al in the 0.05M sample and especially the 0.20M sample is present as (partially) extra framework or even amorphous species. Similar results have been obtained by Groen et al. [28] for the desilication of zeolite H- mordenite. In that study, the overall Si/Al ratios determined with ICP-OES in two samples decreased markedly, from 21 and 27 to 17 and 19, respectively, without any appreciable change in NH3 uptake. Also, Su et al. [18] observed a decrease in Si/Al ratio (from 26 to 15), the appearance of non framework aluminum in the 27Al NMR spectra, and a very modest increase in the concentration of Brønsted sites probed with 1H MAS NMR after severe alkali treatment. The N2 adsorption/desorption isotherms are shown in Fig. 1. For the PARENT sample, a typical type I isotherm is seen, correspond- ing to a strictly microporous material. The isotherms for the 0.05M and 0.20M samples exhibit hysteresis loops, which usually are associated with the filling and emptying of mesopores by capillary condensation. This feature appears to be slightly more pronounced for the 0.20M sample compared to the 0.05M sample. The BET surface areas listed in Table 1, increase considerably as a consequence of the exposure to NaOH solution, and the increase is greatest for the most severely treated sample (0.20M). As can be seen from the t-plot data (Table 1), this is mainly caused by the higher external surface areas, which may be attributed to dissolution of the framework and mesopore formation, in accord with reports from Groen et al. [11,12,14]. The micropore areas increase less, possibly indicating that the zeolite micropore system is unaffected. The micropore volumes, as determined using the t- plot method, is almost unaffected by the treatments, whereas the total pore volumes increase significantly for the 0.05M and 0.20M samples, indicating an increase in the mesopore volume.PDF Image | Methanol to gasoline over zeolite H-ZSM-5
PDF Search Title:
Methanol to gasoline over zeolite H-ZSM-5Original File Name Searched:
Methanol_to_gasoline_over_zeolite_H-ZSM-5_Improved.pdfDIY PDF Search: Google It | Yahoo | Bing
NFT (Non Fungible Token): Buy our tech, design, development or system NFT and become part of our tech NFT network... More Info
IT XR Project Redstone NFT Available for Sale: NFT for high tech turbine design with one part 3D printed counter-rotating energy turbine. Be part of the future with this NFT. Can be bought and sold but only one design NFT exists. Royalties go to the developer (Infinity) to keep enhancing design and applications... More Info
Infinity Turbine IT XR Project Redstone Design: NFT for sale... NFT for high tech turbine design with one part 3D printed counter-rotating energy turbine. Includes all rights to this turbine design, including license for Fluid Handling Block I and II for the turbine assembly and housing. The NFT includes the blueprints (cad/cam), revenue streams, and all future development of the IT XR Project Redstone... More Info
Infinity Turbine ROT Radial Outflow Turbine 24 Design and Worldwide Rights: NFT for sale... NFT for the ROT 24 energy turbine. Be part of the future with this NFT. This design can be bought and sold but only one design NFT exists. You may manufacture the unit, or get the revenues from its sale from Infinity Turbine. Royalties go to the developer (Infinity) to keep enhancing design and applications... More Info
Infinity Supercritical CO2 10 Liter Extractor Design and Worldwide Rights: The Infinity Supercritical 10L CO2 extractor is for botanical oil extraction, which is rich in terpenes and can produce shelf ready full spectrum oil. With over 5 years of development, this industry leader mature extractor machine has been sold since 2015 and is part of many profitable businesses. The process can also be used for electrowinning, e-waste recycling, and lithium battery recycling, gold mining electronic wastes, precious metals. CO2 can also be used in a reverse fuel cell with nafion to make a gas-to-liquids fuel, such as methanol, ethanol and butanol or ethylene. Supercritical CO2 has also been used for treating nafion to make it more effective catalyst. This NFT is for the purchase of worldwide rights which includes the design. More Info
NFT (Non Fungible Token): Buy our tech, design, development or system NFT and become part of our tech NFT network... More Info
Infinity Turbine Products: Special for this month, any plans are $10,000 for complete Cad/Cam blueprints. License is for one build. Try before you buy a production license. May pay by Bitcoin or other Crypto. Products Page... More Info
CONTACT TEL: 608-238-6001 Email: greg@infinityturbine.com (Standard Web Page)