How can a good and loving God send souls to Hell?
Hell is the state of eternal separation from communion with God and the blessed in Heaven. God sends no one to Hell without that person having chosen complete separation from him. In allowing us the freedom to choose good or evil, God necessarily allows each person to accept him or to reject him.
Those who die having willfully and definitively rejected God and his salvific grace—often by violating his Commandments in a grievous manner and then refusing repentance—place themselves in Hell, the state of eternal self exclusion from his presence. Thus, the souls in Hell are those who die stubbornly unrepentant of mortal sin by refusing the love and mercy of God to the end. Jesus spoke often of Hell as "fire" and "darkness" where the damned "will be wailing and grinding [their] teeth" (Luke 13:28). The souls in Hell continually suffer separation from God even as they wallow in hatred of him. (Cf. CCC 1035-1036)
We cannot be united to God unless we freely choose to love him. We cannot love God if we sin grievously against him, our neighbor, or our own selves, "Whoever does not love remains in death. Everyone who hates his brother
is murderer, and you know that no murderer has eternal life remaining in him" (l John 3:14-15) To die in mortal sin—without repentance and without seeking refuge in the compassionate love of God—implies a willful choice to be separated from him. God respects our freedom and will not force us to choose him or abide by his will. (Cf. CCC 1033-1034)
God wills that all people will be saved and become one with him. The liturgy of the Church prays that all may seek and find God and that his mercy may draw everyone into eternal life. (Cf. CCC 1037)
-The Didache Bible