Can a trustee sell assets in a irrevocable trust when the decease owns 99 percent of the property named in the trust?

You must review the terms of the trust to determine the powers of the trustee. If you still have questions then you need to consult an attorney who specializes in trust law.

On one point you seem to be confused. A decedent cannot be the owner of 99% of the property in a trust. The property is owned by the trust. The most common purpose of a trust is to remove property out of a person's estate (the grantor) so that the property bypasses probate.

Once a person transfers her property to a trust, it is managed by a trustee according to the terms of the trust. A properly drafted trust has provisions that direct the distribution of property after the death of the grantor.