Staples Inc. lost $596.3 million in its third quarter, hurt by restructuring, impairment charges, and a drop in revenue. But the Framingham office products company’s adjusted results beat estimates. The chain’s loss amounted to 89 cents per share, compared to a profit of $326.4 million, or 47 cents, a year earlier. Total revenue fell 2 percent to $6.35 billion, from $6.48 billion. Revenue for global operations dropped 12 percent to $1.1 billion, hurt by soft sales in Europe and Australia.