Business visa for travel to Xinjiang. Any special requirements?

Our US company wishes to establish a long-term business relationship with a renewable energy company based in Urumqi, Xinjiang. Hence, I wish to apply for a 12 or 24 month, multiple entry business type to visit the company and several possible renewable energy locations in Xinjiang. I understand the normal procedures in applying for a business one, but are there any special requirements to visit Xinjiang?