where is the Microsoft.SharePoint.IdentityModel location in SharePoint 2013

you can find Microsoft.SharePoint.IdentityModel.dll in the GAC on SharePoint 2013. Note that the GAC location has changed since .net framework 4.0. It's now in c:\windows\microsoft.net\assembly

Here is the location:

C:\Windows\Microsoft.NET\assembly\GAC_MSIL\Microsoft.SharePoint.IdentityModel\v4.0_15.0.0.0__71e9bce111e9429c