I'm not familiar with Neural Tensor Networks, so I'm not super sure. From the bit of reading I did, it seems like they're related to recursive neural networks somehow.

I couldn't find any implementations of either concept on top of Keras, so I probably wouldn't recommend it.

Your best bet is probably to find an existing implementation and study it in whatever language/framework it's in.

Depending on how related recursive neural networks are, I found a few implementations of those in theano, etc, and I'd probably suggest starting there.

If they're not super related, Keras may be a good option, since the learning curve isn't very steep to get started, but you'll probably have to assemble the architecture yourself and since it's an abstraction it will really depend on how easily NTNs can be expressed in that abstraction.

Isn't that the same thing? You use tensors to build a computational graph.