Hiroyuki Hagiwara

Deactivation resistance of ZSM-5-type zeolites containing alkaline earth metals used for methanol conversion

Abstract ZSM-5 and its alkaline earth forms were used for methanol conversion at 600°C where unmodified ZSM-5 rapidly cokes. Of the alkaline earth forms, the calcium and strontium forms are much more coke resistant providing a long on-stream life for methanol conversion. Coke burning regeneration of the calcium form after one cycle results in some migration of calcium to the external surface of the zeolite which lowers the coke resistance. These findings are attributed to the effect of the alkaline earth on the acidity of the zeolite.

Improvement of catalyst stability of ZSM-5 zeolite containing calcium by modification with CaCO3.

Abstract The catalyst life of Ca H ZSM 5, which yields high selectivities to light olefins in methanol conversion, was significantly extended by modification with CaCO 3 . The amount of coke on CaCO 3 /Ca H ZSM 5 after a long-term aging in methanol conversion was considerably less than that on Ca H ZSM 5, indicating that CaCO 3 inhibits the formation of an excessive amount of coke. However, CaCO 3 can hardly prevent the catalyst structure from degradation caused by dealumination with water. From these results, we have concluded that CaCO3 is effective for the improvement of resistance to coking rather than that to steaming, for high catalyst stability.

High Steam Stability of ZSM-5 type Zeolites Containing Alkaline Earth Metals

Abstract In order to examine the dealumination of the framework of H-ZSM-5 type zeolites containing alkaline earth metals, which yields high selectivities to light olefins in methanol conversion at high temperatures, the characteristics of the steamed zeolites were investigated by means of 27 Al MASNMR, FT-ir, TPD of NH 3 and methanol conversion. It was found that the dealumination of the framework of the H-ZSM-5 type zeolites is greatly inhibited due to alkaline earth metals occluded and that the rate of the dealumination has a secondorder dependence on the amount of the framework aluminiums.

Effect of the Dust Components on the Life of Catalysts Used for the Reduction of NOx in the Sintering Furnace Gas

Fe2O3-Al2O3およびV2O5-Al2O32触媒を用い,アンモニア接触還元法を焼結炉排ガス脱硝に適用した場合の問題,主としてダスト成分中触媒に付着しNOx還元能を低下させる成分の検討を行なった。焼結炉排ガス脱硝試験は,鉄鉱石焼結炉煙道の途中から排ガスの一部を吸引し,1000Nm2/hr移動層反応器によって行なった。排ガス処理に用いた触媒は100時間ごとに反応器から一部抜き出し,実験室で模擬ガスによる活性試験,触媒劣化要因を検討するための付着ダスト成分,表面積および細孔容穣などの分析,物姓測定を行なった。その結果,活性は経時的に低下するが,排ガス中のSOxによる影響は少なく,アルカリ成分とくにカリウム塩の付着量の増加と触媒の活性低下がよい対応を示すこと,Si,Ca成分など微細ダスト成分による触媒細孔の閉塞が認められることから,活性低下は,主としてダスト成分の付着に起因することが明らかになった。また,Fe2O3系触媒とV2O5系触媒で活性低下速度が大きく異なる原因として,K成分はFe成分が存在する場合容易に触媒に付着し,両者は複塩を形成すること,V2O5系触媒では触媒毒成分であるK成分の蓄積が主として触媒粒表面から数10μ程度にかぎられるのに対し,Fe2O3系触媒ではK成分は触媒粒内(150μ以上)まで侵入していることなどを明らかにした。