What lines give examples of passionate love in Shakespeare's Sonnet 18?
I've never gotten the feel that sonnet 18 is about "passionate" love. To me, "passionate" makes me think of Romeo and Juliet type love. The kind of love where it is painful to be away from that person. The kind of love that makes you do stupid stuff. Sonnet 18 doesn't feel like that kind of love, because it isn't a sonnet that is overflowing with flowery comparisons. It feels like a logical argument instead of a romantic outpouring. Comparisons are made, but in each case the speaker implies that it's pointless to compare her to anything, because she is so much grander.
Considering your question further, though, I think there are a few lines that could be used to illustrate passionate love. Line 2, for example.
Thou art more lovely and more temperate:
I think it illustrates passionate love because it is spoken directly at "her." It says "you are" (thou art). I can imagine a young couple in love, staring longingly into each others' eyes and saying something like that. It sounds passionate.
Line 9 is very similar, because it again uses the word "you."
But thy eternal summer shall not fade
That line also sounds like a classic lovers line. "You'll never fade away in my eyes. You'll always be beautiful to me." It's perfect for a romantic comedy of some kind, because it sounds so deeply passionate.