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Super Lattice Integrated Catalyets

At the 11 th Surface Science Seminar of the Surface Science Society of Japan (June 1991) DrA. Kato of Hitachi Ltd. gave a review of Super Lattice Integrated Cata- lyst (WC). Recently, catafytic thin films

have been attracting much interest, not oflly as model materials, but also as new functional catalysts such as sensors. One of the important subjects to be solved in preparing thin film catalysts is to increase the porosity of these materials. As the sur- faue area of a thin film catalyst is usually very low, its practical activity is inevitably

IOW. Physical fabrication techniques such as

deposition, etching, and lithographic pat- terning are used for making thin films in microelectronics. These techniques are also applicable to the preparation of thin film catalyst with controlled pore structure. Professor Dr. lnoue of Nagaoka Gijyutsu Kagaku University has recently developed

a super-lattice-type thin-film catalyst of Cu-

TiC2 on Si (111) (Shokubai, 26 (1966) 77). This catalyst has a cylindrical pore struc- ture (diameter 166 m) and is fabricated by vapour deposition with MO masking tech- nique. Researchers of Exxon Research

and Engineering Company have pro-

posed a super-lattice material with control- led pore size and slot geometry. They have fabricated a Si-Ge super lattice with micro- pores of 2.5 nm. (See U.S. Patent 4,701,666, Oct. 291967).

Using thin-film technology, a new de-

gree of freedom in preparing super lattices of controlled macro-micro pore structures has been realized. Super Lattice Integrated Catalysts (WC) are expected to exhibit novel functions.

Methane Conversion

I have received the following comments from Professor Heinz Heinemann in con- nection with an item in the News Brief of Vol. 77, No. 1, of Applied Catalysis.

The reviewer states that we had pre-

viously described catalysts which gave 199% selectivii to hydrocarbon products at conversions of about 19%. He contrasts this with a hydrocarbon selectivii in the current paper of about 92% at a conversion of about 10%. In fact there is no contradic- tion between our two papers. As is clearly

stated in the later paper on page 692, a blank run with an empty reactor gave about

0.6 to 1% conversion to CO2 or a CO2 selectivity of 69-100%. This would corre- spond to 619% CO2 selectivii at 19% conversions of CH4. This amount of CO2 must therefore be assumed to be formed

purely thermally at the prevailing condi- tions. If one deducts this thermal CO2 se-

lectivky from the values shown in Table 2 of the paper, one arrives at an essentially

199% hydrocarbon selectivity or the same as claimed on our preceding paper. Per- haps it would be best to say that the cata- lytic hydrocarbon selectivity is very close to 199%.

I would be sorry if our not going into greater detail in the paper would have lead to a misconception.”

JULIAN ROSS

Survey of Experimental Techniques In Surface Chemical Physics

A sunrey with the above title, which re- cently appeared in Pure and Applied Chemistry (62 (1999) 2297-2922), was commissioned by IUPAC commissions I.5 and I.6 and prepared for publication by

applied catalysis - Volume 79 No. 2 -l 0 December 1991