The mechanism of synthesis process of tributyl citrate using aluminum dihydrogen tripolyphosphate supported on modified activated carbon as a catalyst was investigated by gas chromatography-mass spectrometry, and the kinetic equation was also studied. The results showed that the influence of internal diffusions was eliminated with the particle size smaller than 180 µm, but the influence of external diffusions was eliminated with the stirring speed higher than 450 r/min. The yield of 97% for tributyl citrate was achieved under the the following optimized condition: 1:4.2 of acid to alcohol, 8% of dosage of catalyst accounting for total reaction amount, 5 h of reaction time for water segregating and refluxing, and 150°C of reaction temperature. The apparent reaction activation energy was E a = 61.4 KJ/mol. The mechanism of this catalytic reaction was considered to be attributable to the fact that the steps of the esterification of citrate to produce both monobutyl citrate and dibutyl citrate were very fast, but the rate of the formation of tributyl citrate was slow. The control step of total reaction was the reaction between dibutyl citrate and n-butanol to produce tributyl citrate.

Lanthanum aluminate(LaAlO3) single crystal as a substrate for high Tc superconducting film has attracted attention recently. We report here a transmission electron microscopy(TEM) study of the crystal structure and phase transformation of LaAlO3 by using Philips EM420 and EM430 microscopes. Single crystals of LaAlO3 were investigated first by optical microscope. Stripe-shaped domains of mm size are clearly seen(Fig.1a), and 90° domain boundary is also obvious. TEM specimens were prepared by mechanical grinding and polishing followed by ion-milling.Fig.lb shows μm size stripe domains of LaAlO3. Convergent beam electron diffraction patterns (CBED) from single domain were taken.Fig. 2a and Fig. 2c are [001] zone axis patterns which show a 4mm symmetry, and the (200) dark field of this zone axis gives 2mm symmetry(fig.2b). Therefore the point group of this crystal is either 4/mmm or m3m. The projection of the first order Laue zone(FOLZ) reflections on zero layer (fig. 2c) shows that the unit cell is face centered. A tetragonal unit ceil is chosen, with a=0.532nm and c=0.753nm, c being determined from the FOLZ ring diameter.