1、PDF外文：http:/ 中文 1960字 出处： Carbon, 2005, 43(13): 2808-2811 中文 3D interconnected macroporous carbon monoliths preparedby ultrasonic irradiation Nattaporn Tonanon , Adisak Siyasukh , Yunyong Wareenin , Tawatchai Charinpanitkul , Wiwut Tanthapanichakoon , Hirotomo Nishihara , Shin R. Mukai ,
2、 Hajime Tamon Abstract： A new method in preparation of 3D interconnected macroporous carbon monolith has been introduced. Ultrasonic irradiation(ultrasonic intensity 78 W/cm2) and low catalyst concentration (C/W = 10 mol/m3) of RF solution are used as an interesting and unique preparation method for
3、 3D interconnected macroporous sonogel (gel irradiated by ultrasound at gelation stage) and/or3D interconnected macroporous carbon monolith without using templates. Keywords: Porous carbon； Pyrolysis； Adsorption； Scanning electron microscopy； Porosity Macroporous monolith is an interesting structure
4、 that has interconnected skeletons in a single column, and this unique structure allows flow paths (throughpores)through the monolithic columns . Carbon monolith has high potential to be good candidates for applications such as columns for chromatography, catalyst supports, adsorbents and porous ele
5、ctrodes under continuous flow conditions. Macroporous carbon monoliths are mostly prepared by using carbon precursors and macroscopic shape templates . In general, macroscopic shape templates are interconnected skeleton such as silica template, zeolite, stable emulsions, polymer latex and the inters
6、titial volume of other porous structures. Carbon precursors are polymeric materials or precursor of polymeric materials such as sucrose, some thermoplastics, phenolic resin, copolymerization of resorcinol Fe(II) complex and other thermosettings. There are some reports on macroporous carbon aerogels
7、prepared by using metal catalyst or acid catalyst. In this work, a new method in preparation of 3D interconnected macroporous carbon monolith has been introduced. In general, ultrasonic irradiation has outstanding effects in many chemical reactions such as increasing reaction rates and yields
8、of products, shortening reaction time, altering the reaction path and making milder reaction conditions possible. An interesting role of ultrasonic irradiation on mesoporous properties of RF carbon gel when the ratio of catalyst to water C/W or pH is high was also reported 10. To the best of our kno
9、wledge, this study is the first to report on the work of ultrasonic irradiation (ultrasonic intensity 78W/cm2) together with low catalyst concentration (C/W = 10 mol/m3) of RF solution as an interestingand unique preparation method for 3D interconnected macroporous sonogel (gel irradiated by ultraso
10、und at gelation stage) and/or carbon monoliths without using templates. Macroporous sonogel monolith, precursors for macroporous carbon monolith, were prepared from resorcinol formaldehyde (RF) solutions which were composed of resorcinol (C6H4(OH)2) (R), formaldehyde (HCHO) (F), sodium carbonate (Na
11、2CO3) (C) and distilled water (W). All chemicals were research grades from Wako Pure Chemical Industries. Na2CO3 and distilled water were used as a basic catalyst and a diluent respectively. The ratios of resorcinol to formaldehyde (R/F), resorcinol to water (R/W) and catalyst to water (C/W) were fi
12、xed at 0.5 mol/mol, 8100 mol/m3 and 10 mol/m3 respectively. Gelation temperature was 308 K. Ultrasonic wave was applied into RF solution right from the start by Vibra Cell model VC 130 (frequency 20 kHz) with a titanium alloy transducer at intensity 78 W/cm2. When it was close to the gelation time,
13、the ultrasonic irradiation was stopped and the RF solution was then poured into the cylindrical glass tube (inner diameter = 3 mm, length = 40 mm) followed by aging for 7 days at 348 K in the oven. Before freeze drying, water in RF sonogel monolith was replaced by solvent exchange with t-butanol for
14、 three times. After that, RF sonogels were freeze-dried at 263 K for 3 h to obtain freeze dried macroporous RF sonogel monolith. Macroporous carbon sonogel monoliths were obtained by pyrolyzing macroporous RF sonogel monoliths at 1023 K. Pyrolysis was conducted under a 200 cm3STP/min flow of nitroge
15、n gas. At first, the freezedried sonogels were heated to 523 K at a constant heating rate of 523 K/h, and were kept at this temperature for 2 h.Then they were heated to 1023 K at a constant heating rate of 523 K/h and were kept at 1023 K for 4 h. The structures of RF gel and RF sonogel monoliths wer
16、e observed by scanning electron microscope(SEM). Macropore size distribution was measured by using mercury porosimeter. Porous properties, BET surface area (SBET), mesopore volume (Vmes) and micropore volume (Vmic), were determined from the N2 adsorption method using an adsorption apparatus. T
17、he effect of ultrasonic irradiation at gelation stage can be seen as followed. In gelation process, gelation time is shortened outstandingly with ultrasonic irradiation. Gelation time obviously decreases from 48 h (RF gel monolith) to 8 h (RF sonogel monolith). The shrinkages of 3D interconnected ma
18、croporous RF gel monolith and RF sonogel monolith, after freeze drying, are 21% and 1% respectively. It is obvious that ultrasonic irradiation leads to small shrinkage in RF gel sonogel monolith compared to RF gel monolith. In Fig. 1, the cross section of RF sonogel monolith observed by SEM shows 3D
19、 interconnected macroporous structure which is totally different from mesoporous structure of RF gel monolith. SBET are 228 (RF gel monolith) and 5 (RF sonogel monolith) m2/g. Vmic and Vmes of RF gel are 0.02 and 0.32 cm3/g respectively. For RF sonogel monolith, Vmic and Vmes cannot be detected. Aft
20、er pyrolysis of RF sonogel monolith, no change in macroporous structure and very low shrinkage are observed.After pyrolysis SBET and Vmic of sonogel increases from 5 to 366 m2/g and N/D to 0.11 cm3/g respectively (Vmes cannot be detected). It can be seen from SEM micrograph in Fig. 2 together with p
21、orous properties that RF carbon monolith can keep 3D interconnected macroporous structures. The macropore size distributions of carbon monolith are narrow, the average macropore size around 1 3 lm as shown in Fig. 3. In this work, new synthesis method for 3D interconnected macroporous sonogel
22、and/or carbon monolith is proposed with some advantages to other methods such as shorter gelation time of polymer monolith, small shrinkage percentage, no template preparation and template removal. In addition to this preliminary work, the effect of R/C on t
23、he structure of 3D interconnected macroporous carbon monolith (microwave drying at 200 W after solventexchange with t-butanol) has been investigated. In Figs. 4 and 5, R/C = 1200 mol/mol gives 3D interconnected macroporous carbon monolith with smaller pore diameters than R/C = 800 mol/mol. 3D interconnected macroporous carbon monolith
