Published March 1998
The following review is a speculative interpretation of a process to produce 1,4-butanediol (1,4-BDO) from butadiene (BD) via 3,4-epoxybutene (EPB), based on Eastman Chemical patents. The process requires three reactions: (1) oxidation of BD to EPB, (2) hydrolysis of EPB to 1,4-butenediol, and (3) hydrogenation of 1,4-butenediol to 1,4-BDO. A major by-product of the process is 1,2-butanediol (1,2-BDO).
For the first reaction, makeup BD is fed into a recycle gas stream using n-butane as a diluent. Makeup oxygen is added, and the combined recycle/makeup streams are fed to a multitube epoxidation reactor containing a silver-based catalyst. The reactor converts 17-18% of the BD (single-pass basis) to EPB. Effluents from the reactor are compressed and sent to an absorber/stripper system to recover EPB. Crude recycle gases from the absorber/stripper are scrubbed to remove CO2 and are returned to the epoxidation reactor for conversion of unreacted BD.
EPB from the epoxidation step is hydrolyzed with an excess of water to a mixture of 1,4- and 1,2-butenediols using a copper/zeolite catalyst in a packed-bed reactor. The hydrolysis effluent is pumped directly to a two-stage hydrogenation system that converts butenediols to the corresponding BDOs.
Effluent from the hydrogenation reactors is sent to a series of five distillations: (1) a light ends column to remove light organics; (2) a triple-effect evaporator to recover water for recycle; (3) a vacuum drying column to remove residual water; (4) a by-product column to recover 1,2-BDO; and (5) a BDO product column to recover 1,4-BDO as an overhead product and to purge heavy ends.
Process economics were estimated for a base case capacity of 60 million lb/yr (27,200 t/yr) of 1,4-BDO. An assessment of the future potential of this process is made based on the resulting economics.