Is it permissible to give zakat to a debtor who refuses to take it, in the form of a loan, and if it is refused, must it be given to another eligible recipient?

It is not permissible to give Zakat to someone who refuses to take it, even with the intention of giving it when the loan is repaid, because Zakat is obligatory immediately and it is not permissible to delay it. And if you lend him a good loan, you will be rewarded.