Current Status of related R&D activity
Benzoid compounds were introduced to a petrol for increasing of octane number
instead of led compounds. But their toxicity and possible thermal destruction to
carcinogenic polyaromatic products initiated research in development of new
generation of petrol. This petrol should contain no led and benzoid components
and posses high octane number. To solve this problem petrol should contain
minimum of n-alkanes and maximum of iso-alkanes. Catalytic isomerization is used
for this. Many disadvantages related to the use of liquid catalysts, namely
H2SO4 or HF, mainly employed for catalytic alkylation have led to intensive
research on solid catalysts. Fundamental expectations are connected with strong
solid acids immobilised on inorganic carriers [1–4] in general.
Titanium [5–6], binary and trinary metal oxides [7], zeolites [8] and
mesoporous media [9] were tested as supports. Most researches were made on
regular [10 – 13] and mesoporous [14] zirconium oxide, metal
doped zirconia [8,15 – 17]. Sulphation of the support surface is used
in most cases [18]. Other acids, like phosphoric [5], molibdo- and tungsto-phosphoric
[19] were also studied as promoters. But most research was
made on sulphated zirconia. According to proposed mechanism of short-chain alkan
transformation the
catalytic process is bifunctional and requires co-operation among neighbouring
acidic groups in transfer of a hydron. Such co-operation is essential feature in the
manifestation of superacidity. We demonstrated that on the surface of silica
with covalently bonded groups despite to absence of long-distance order in the
system of surface groups, the micro-order is present. It leads to formation of
supramolecular structure organised from functional groups with similar
orientated dipoles.
Investigation of dielectric relaxation in such materials enables us to determine
existence of such supramolecular structures by means of monitoring molecular
mobility of dipoles depending on surface nature and particularly depending on
the bonded group nature. Significant increase in dielectric losses from
temperature higher then 248 Ê can be stipulated as melting of physically
adsorbed water which is definitely present at silica gel. On surface of the
hydrophobic silica two supramolecular structures generated by uno-dimentional
physically adsorbed water and two-dimensional residual silanol groups co-exist.
From this research can be sudgested that covalent immobilisation of functional
groups will ensure higher stability of the catalysts and more freedom of acidic
fragments for surface movements.
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Today, 1997, 38(3), 309-319.
[2] Sommer J., Sassi A., Hachoumy M., Jost R., Karlsson A., Ahlberg P. Journal
Of Catalysis, 1997, 171(2), 391-397.
[3] Cheung T.K., Gates B.C. Chemtech, 1997, 27(9), 28-35.
[4] Johansson M., Klier K. Topics In Catalysis, 1997, 4(1-2), 99-108.
[5] dosSantos A.C.B., Kover W. B., Faro A.C. Applied Catalysis A-General, 1997,
153(1-2), 83-101.
[6] Hess A., Kemnitz E. Applied Catalysis A-General 1997, 149(2), 373-389.
[7] Miao C.X., Hua W.M., Chen J.M., Gao Z. Science In China Series B-Chemistry,
1996, 39(4), 406-415.
[8] Cheung T. K., Gates B.C. Journal Of Catalysis, 1997, 168(2), 522-531.
[9] Wang Y., Kim A.Y., Wang L.Q., Li S., Liu J., Bunker B.C. Abstracts Of
Papers Of The American Chemical Society, 1997, 213(Pt1), 315-COLL.
[10] Song X. M., Sayari A. Catalysis Reviews-Science And Engineering, 1996, 38(3),329-412.
(Review).
[11] Drago R.S., Kob N. Journal Of Physical Chemistry B, 1997, 101(17),
3360-3364.
[12] Morterra C. Cerrato G., Bolis V., DiCiero S., Signoretto M.
Journal Of The Chemical Society-Faraday Transactions, 1997, 93(6), 1179-1184.
[13] Farcasiu D. Li J.Q., Kogelbauer A. Journal Of Molecular Catalysis
A-Chemical, 1997, 124(1),67-78.
[14] Huang Y.Y., McCarthy T.J., Sachtler W.M.H. Applied Catalysis A-General,
1996, 148(1), 135-154.
[15] Yori J.C., Parera J.M. Applied Catalysis A-General 1996, 147(1), 145-157.
[16] Sikabwe E.C.,White R.L. Catalysis Letters, 1997, 44(3-4), 177-183.
[17] Patel A., Coudurier G., Essayem N., Vedrine J.C. Journal Of The Chemical
Society-Faraday Transactions, 1997, 93(2), 347-353.
[18] Arata K. Applied Catalysis A-General, 1996, 146(1),3-32.(Review)
[19] Okuhara T., Nishimura T., Misono M. Studies In Surface Science And
Catalysis, 1996, 101(PtA&B),581-590.
