TECHNOLOGY FOCUS - CHEMICAL ENGINEERING - Preferred Method: The precipitation is effected at 40-80 degreesC and a pH of 6-9. The divalent iron is partially oxidized by the use of an oxidizing agent that converts a portion of the divalent iron into trivalent iron. The oxidizing agent is added concurrently with the base.Preferred Composition: The aqueous solution comprises divalent and trivalent iron salts and trivalent modifier metal salts in such proportion that there are 1.5-2.5 trivalent metal atoms per divalent iron atom. The precipitated composition has an atomic ratio of iron to modifier of 5:1 to 20:1. The shaped catalyst unit contains divalent copper of 0.5-3 wt.% based on the weight of the shaped catalyst units. It contains acicular particles having an aspect ratio of at least 2 and an average (by wt.) maximum dimension of 500-1500 nm and including alumina, alumina monohydrate, zinc oxide, iron oxide, or iron oxyhydroxide at 2-40 wt.% on the shaped unit. The modifier metal comprises chromium in 5-15 wt.%.Preferred Components: The aqueous solution comprises metal salts in the trivalent state and a reducing agent is used in an amount to give the desired proportions of divalent and trivalent compounds. The reducing agent is hydrazine or formaldehyde. The oxidizing agent is an alkali metal nitrate in an amount to convert one half to 2/3 of the divalent iron to trivalent iron. EXAMPLE - 200 g iron sulfate heptahydrate, 1.11 g copper (II) sulfate pentahydrate, and 24.48 g chromium (III) sulfate monohydrate were dissolved sequentially in 1400 ml de-ionized water, deoxygenated by flushing with nitrogen. The solution was heated to 72degreesC and 20.19 g potassium nitrate and 140.27 g potassium hydroxide dissolved in 750 ml deionized water were added drop-wise over 1 hour. Nitrogen was continuously bubbled though the boiling suspension. The suspension was refluxed for a further 30 minutes and allowed to cool to room temperature over 90 minutes. The resulting grey-black precipitate was washed thrice with deionized water until free of sulfate, followed by two washings of acetone before drying in an oven at 50degreesC for 6 hours. By interchanging the washing procedure for one where the material was re-slurried with hot demineralized water, the residual sulfate content was lowered from 3000 to 600 ppm. Shaped catalyst units were prepared by mixing the modified magnetite sample with 2 wt.% graphite, pre-compacting to a density of 1.5-1.6 g/cm3, grinding and sieving the pre-compacted material to give a pellet feed having a particle size of 300-850 mum and forming pellets of 3.6 mm X 5.4 mm diameter. The pellets were evaluated to have superior mean horizontal crush strength (6.11 kg).