BET surface area measurement

The single-point BET surface area measurement was used to check for open pores. The results for some soft and hard carbon samples heated at 700°C and 1000°C are presented in Table 2 for comparison. The hard carbon samples studied here have about ten times more open porosity than the soft carbons. 

Grinding was performed using Retsch ball-mill. Particle size distribution was measured using Malvern (Mastersizer) laser particle sizer. BET surface area measurements were carried out using ASAP (Micromeritics) surface area analyzer. 

BET surface area measurements were carried out using a Micromeritics TriStar 3000 gas adsorption analyzer. Approximately 0.35 g of sample was weighed out and loaded into a 3/8-inch sample tube. Nitrogen was used as the adsorption gas and sample analysis was performed at the boiling temperature of liquid nitrogen. 

There are many ways to characterize the structure and properties of carbonaceous materials. Among these methods, powder X-ray diffraction, small angle X-ray scattering, the BET surface area measurement, and the CHN test are most useful and are described briefly here. To study lithium insertion in carbonaceous materials, the electrochemical lithium/carbon coin cell is the most convenient test vehicle. 

The authors would like to thank Dr. Firooz Rasouli and Dr. Hoongsun Im for technical discussions and Felecia Logan for experimental work. Special thanks to Dr. Weizhong Zhu for BET surface area measurements. Dr. Weizhong Zhu and Dr. Hoongsun Im were participants in the Philip Morris USA Postgraduate Research... 

The results of XRF, BET surface area measurements and catalytic testing are summarized in Table I, while the results of catalytic testing are also shown in Figure 1. The rates displayed in Table I are the rates of reaction of propane per unit surface area as calculated from the interpolated propane conversion. Propane conversion was 3% or less, while oxygen conversion was less than 30%. 

Table I. Results of XRF, BET Surface Area Measurements and Catalytic Testing...

The broad line 2H NMR results, combined with the H and 29Si MAS-NMR results, confirm that acetone-d6 molecules are able to penetrate into the microporous channels of sepiolite, and cannot be removed by heating to only 60°C. This result is in agreement with a previous study that found, on the basis of BET surface area measurements, that molecules such water, ammonia, ethanol, benzene and pyridine were small enough to fit inside the microporous channels [10],... 

In contrast with the Fe system, only one crystallographic phase has so far been produced by laser pyrolysis from Group 6 (Mo and W) carbonyls or chlorides. A variety of experimental conditions have been found to lead to fee Mo2NtQy, Mo2CAOv and W2Nj.Oy phase. However, an amorphous phase is obtained in the case of WCA (Table 27.1).6 BET surface areas measured for the Mo nitride and carbide systems are in the range of 50-80 m2 g-1. 

To conclude this section, it must be reiterated that following the discussion above, it is obvious that different causes exist for the spreading of the specific surface area measured in an adsorption experiment. Thus, it is usually estimated, by measuring repeatedly the tested samples, that the relative error in the BET surface area measurements of the adsorption parameters is normally around 20% [5], For samples with very large surface areas, the relative error could be even 30% [2],... 

The measurement of pore size distributions is well established. However, the use of BET surface area measurements for zeolitic materials has been called into question due to potential multiple adsorption and nonconformity of monolayer adsorption implicite in the BET theory. The type of gas used, the method of data analysis, and even the use of the term surface area for a zeolitic material has been seriously questioned lately. On the other hand, most commercial manufacturers supply a surface area determined often by a three point or even a one point procedure that some researchers feel tells something about the material. 

The catalysts were characterized by BET surface area measurement, XRD, in-situ CO2 H2 chemisorption measurements, and Temperature Programmed Reduction (TPR). CO2 hydrogenation was carried out in a fixed bed flow reactor made of stainless steel. Prior to the activity studies, the catalysts were reduced in 99.99 % H2 flow at 723K for 12hrs. After this, the reaction gas (H2/CO2 = 3) was introduced into the reactor at 573K at 10 atm. The gas phase effluents were analyzed by on-line GC. 

The physical and chemical characteristics of prepared HY and KY zeolite were analyzed by AAS and BET surface area measurements. These results are summarized in Table 1 and show that they are highly crystalline and free from impurities. 

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