What is the purpose of 焉 in 「不近人情焉」?
Several Classical Chinese particles are of onomatopoetic origin, and have neither a fixed translation nor a fixed character representation.「焉」sometimes means where or at, but you'll have to rely on context to figure when this meaning applies.

Those meanings do not apply here.「焉」, in this context, is an end-of-phrase modal particle (句末語气詞).


  吾聞言於接輿，大而無當，往而不反。吾驚怖其言，猶河漢而無極也，大有逕庭，不近人情「焉」。
  
  I heard words from 接輿 which were extravagant but hollow, and irretrievable once uttered. His words frightened me;  (1) they were vast and boundless like the galaxy, polar opposite to reality, and worlds apart from the experiences of man (2)


Two options for translating「焉」in this passage. Place one of these in their respective numbered positions:


surely,
!



  For reference, a passage where where or at applies as a translation to「焉」:
  
  
    《左傳・隱公元年》：＂制，巖邑也，虢叔死「焉」。＂
    
    Commentary of Zuo, first ruling year of Duke Yin of Lu: " 制 , (name of a) strategically important city. 虢叔 passed away「here」."
  




Reference:


《王力古漢語字典》