can i charge my 15 pro max with my ipad 4th gen adapter and cable?

Yes and no. The 4th gen iPad has a Lightning connector port. The iPhone 15 has a USB-C port. I couldn't find which exact power adapter came with the 4th gen iPad, but I am guessing that the power cable you have has a Lightning connector.

To best charge your iPhone, especially if you want to fast charge it, would require a 20W USB-C adapter.

Ref: About Apple USB power adapters - Apple Support

Vivek8887 wrote:

Ipad 4th gen have 20w adapter and come with type C cable

Is it perhaps an iPad Air 4? If so, yes it uses a USB-C charge cable.

Interesting as the Apple Specifications for this iPad model shows that it has a Lightning connector. Odd that they would provide a USB-C power adapter for it.

Ref: iPad (4th generation) - Technical Specifications - Apple Support