我们还发现，在催化氧化环境中连续使用的钼酸铋粒径会越来越长，对丙烯醛的选择性会相应提高。

The poor acrolein selectivity of this catalyst was improved by continuous use in the catalytic oxidation for making the particle size of the dispersed bismuth molybdate larger.

但由于丙烷的稳定性和丙烯醛的活泼性，该反应对催化剂的要求苛刻，有关的研究并未取得重大的突破。

However, due to the chemical stability of propane and the activity of acrolein, this reaction required a multiple functional catalyst and no great progress was made in this field.

第一部分讨论了DL-蛋氨酸及其衍生物的化学合成，包括丙烯醛法、丙二酸酯法，氨基内酯法等，并着重介绍了海因法。

In the first part, chemical synthesis, including by acraldehyde, malonic ester, ami no lactone and others were discussed and synthesis by hydantoin was emphasized.