All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
It is unlawful to delay the prayer from its prescribed fixed time until its time is over under any circumstances unless it is for combining between two prayers (like Thuhr and Asr, and Maghrib and 'Isha) provided there is a sound reason for doing so.
The place where you work is acceptable for performing the prayer in, and you may use a rug and the like if you doubt the purity of the place. Jabir Ibn 'Abdullaah narrated that the Prophet said: "I was given five things that were not given to any person before me, among which he mentioned: '...and the earth was made a mosque and a pure place (for me to pray on). so, when the time of the prayer comes every man (i.e. every person) from my nation should pray (whenever she/he is)." [Al-Bukhari and Muslim]
So, when the time of the prayer comes, look for a pure place and pray therein, even if this is in your work place. But, beware of delaying the prayer from its prescribed fixed time. Indeed, any person who delays the prayer from its prescribed fixed time without a sound reason is considered like a person who gives up praying completely.
For more benefit, please refer to Fatwa 81555.
Allaah Knows best.