2-氯-5-三氟甲基吡啶和3-三氟甲基吡啶的制备

Production of 2-chloro-5-trifluoromethylpyridine and 3-trifluoromethylpyridine

研究了以3-甲基吡啶、氟化氢和氯气为原料在流化床反应器中一步法气相氯氟化反应制备2-氯-5-三氟甲基吡啶和3-三氟甲基吡啶的工艺,并对催化剂进行了筛选和考评,发现CrO-Al、Cr Cl-Al的活性较佳。以CrO-Al为催化剂,空速为288 h-1,温度为300℃时,2-氯-5-三氟甲基吡啶和3-三氟甲基吡啶的总收率最高,为66.6%,且失活催化剂在350℃,氮气和空气的体积比为1:1的混合气体下再生后,其催化活性基本可以恢复,2-氯-5-三氟甲基吡啶和3-三氟甲基吡啶的总收率均保持在66%左右。根据实验结果提出了反应机理和结焦机理。对催化剂进行了BET、TG和NH3-TPD表征,发现催化剂失活的主要原因是积炭覆盖了催化剂表面以及孔道,使催化剂强酸中心大量减少所致。

2-Chloro-5-trifluoromethylpyridine and 3-trifluoromethylpyridine are produced by β-picoline reacting with chlorine and hydrogen fluoride in a fluidized-bed reactor. The total yield of 2-chloro-5-trifluoromethylpyridine and 3-trifluoromethylpyridine reaches 66.6% over the CrO-Al catalyst at a space velocity of 288 h-1 and temperature of 300℃. The reactivity of the deactivated catalysts is recovered after regeneration at 350℃ with mixed gas of nitrogen and air at volume ratio of 1：1. The total yield is around 66% with regenerated catalysts under the condition of 288 h-1 and 300℃. According to the reaction result, the mechanism of one-step chlorofluorination reaction is proposed, dehydrochlorination-condensation of intermediate products accounted for coking. The results of BET, TG and NH3-TPD characterizations indicate that the deactivation of the catalysts is caused by the carbonaceous by-products which cover the surface and pores of the catalyst.