Ok, I suppose the initial question was kind of answered so let's close it here.Here is a word of advice when posting questions on AAC.
You began by requesting information on how to use an op amp to convert 5 V to 12 V.
Now we can see that the final goal has nothing to do with the problem stated. In other to avoid playing the game of 101 Q & A, it is better for everyone if you start off with the actual problem and not what you envision is your problem.
We see this too often here on AAC forums and strive to make the AAC experience more efficient and enjoyable for everyone concerned.
Thanks everyone