From Introduction: "This report on the development of the oil-recycle process covers: 1. Review of the work in Germany on the first oil-circulation process. 2. Work by the Bureau of Mines, United States Department of the Interior. (a) Preliminary experiments on a laboratory scale, consisting of orientation tests and bench-scale operation, employing a 1-foot bed of catalyst in a 3-inch diameter vessel. (b) Operation of 2 pilot plants with a 4- or - 8 foot bed of catalyst in 3-inch-diameter reactors. Up to 3 gallons of C2+ hydrocarbons was produced per day in each of these plants. (c) Operation of a barrel-per-day pilot plant with an 8-foot bed of catalyst in an 8-inch-diameter reactor."