New Membrane Cuts Oil-Refining Energy Use by About 90%, Chinese Team Says

Chinese scientists say they have developed a new oil-refining technique that cuts the energy used in the process by roughly 90%, according to a study from the Dalian Institute of Chemical Physics. If the method can be scaled up for industry, the researchers say it would lower production costs and emissions while making the process more precise.

Crude oil cannot be turned directly into petrol or plastics — refineries must first separate it into different fractions, one of the most energy-intensive steps in the process. The conventional method, distillation, exploits tiny differences in boiling point, repeatedly heating the mixture so it vaporises and condenses; it consumes large amounts of energy and is relatively imprecise.

The new process, called "molecular refining," instead uses metal-organic framework membranes — a kind of molecular sieve with specially designed pores — to sort compounds directly, sending each to the production line best suited to it. In a technique the team calls cascade membrane separation, a first membrane screens molecules by size, splitting off the straight-chain and single-branched alkanes used to make ethylene, since these molecules differ from their neighbours by only about 0.1 nanometre. A second membrane, working on molecules that differ by less than 0.01 nanometre, uses surface chemistry to separate aromatic compounds — key ingredients for plastics, resins and fibres — from the multi-branched alkanes and cycloalkanes used in petrol. The researchers tuned the membranes' pore size and surface chemistry using a tannic acid micro-etching method.

In laboratory tests on a simulated light naphtha mixture containing 15 components, the two membranes working in series separated it into three high-value product groups with a recovery rate of 85 to 90%. Because the oil no longer needed repeated heating, vaporisation and condensation, the process used about 91% less energy than traditional distillation. The work was published last month in the journal National Science Review.