低压合成甲醇催化剂母料变色点性质的研究

STUDY ON COLOUR-TURNING POINT OF PRECURSORS OF METHANOL SYNTHESIS CATALYST

研究了合成甲醇催化剂母料陈化期间pH值的变化情况,尤其是母料变色点前后pH值的变化,考察了反应pH值及反应温度对变色时间及催化剂活性的影响。结果表明,合成甲醇催化剂母料在陈化期间pH值一直在改变,在变色点附近出现了pH值的一个极小值,与其相应的是在母料变色前后催化剂的活性发生了明显的变化,因此,在变色点前后母料的组成及结构都发生了明显的变化。升高反应温度有利于母料结构的调变,升高反应pH值不利于母料结构的这种变化。通过本实验确定了催化剂母料在并流情况下最佳沉淀pH值范围为7 5～8 5,最佳沉淀温度大于80℃。

The precursors of methanol synthesis catalyst have been prepared using different coprecipitation method, and the catalytic activity and stability were tested using differential fixed-bed reactor. The pH values of the precursors of methanol synthesis catalyst in the period of ageing , especially around the colour-turning point have been studied. At the same time the effect of reaction temperature and reaction pH on the time of colour-turning of precursors and cata-lytic activity have been investigated as well. It is shown that the pH values of the precursors of methanol synthesiscatalyst in the period of ageing changes continuously, the pH values appear a minimum in the vicinity of colour-turning point, at the same time the activity of the catalyst has a sharp increase after the colour-turning point. It is predicted that the composition and structure of the precursors altered obviously after the colour-turning point. It is shown that from the test result increasing reaction temperature favors structure adjustment of precursors; while increasing reaction pH restrain the structure adjustment of precursors. The experimental results showed that co-current feed method was the best method. The activity and stability of the catalyst prepared from co-current method was higher than those prepared by other methods. The optimum pH range of precursor was 7.5～8.5 and the temperature should be higher than 80?℃.