N5

gas using a series of inexpensive solids

and two commercial catalysts.

E. FURIMSKY

Improved Selective Dehydrogenation

Process

Linde AG (Munich) have commer-

cialised a catalyst-based dehydrogenation

process that converts propane or isobu-

tane (2-methylpropane) to propene or but-

2-ene, respectively. The process is 2%

more selective than alternative techno-

logies It has been tested since 1989 in a

10,000 ton per year plant at Ludwigshafen

in Germany. Dehydrogenaticn occurs in a

fixed bed reactor with a chronium oxide

catalyst on an alumina carrier. Catalytic

selection is 91 mol-% for propene and 95

mol-% for but-2-ene. The reaction tem-

perature is 500-550°C and the pressure 2

bars. The catalyst contains no precious

metals and has a cost of 25% of that of

other dehydrogenation catalysts. There is

a nine-hour cycle time between catalyst

regeneration and this doubles the catalyst

life.

Diesel Fuels from Vegetable Oil

Novamont S.p.A. (Milan) is planning to

produce diesel fuel from vegetable oils in

a 60,000 ton per year plant at Livorno, Italy.

The fuel will be called Diesel-Bi; because it

is not produced from fossil fuels, it pro-

duces no net increase in CO2 and will be

immune from the proposed EC Carbon

Tax. Diesel-Bi is also sulphur-free and

emits 50% less paniculates than ordinary

diesel; engines using it require no modifi-

cation. It is formed by the catalytic trans-

esterification of sunflowerlsoyalcanola oils

(90% with 10% methanol), giving methyl

esters. Novamont is planning a second

European plant in either France or Ger-

many.

Cyanide-Free Gold Process

A one-step route to extract gold from

refractory sulphide ores has been de-

veloped at the South Dakota School of

Mines and Technology by Professor K.

Han. Such ores are usually difficult to treat

and require two steps: one to liberate the

gold and the second using cyanide to

leach out the gold.

In the new process, the ore is oxidised

by oxygen injection and pressure-leached

in ammoniacal solution at 400 psi and 150-

180°C with a copper(ammine catalyst;

this facilitates the dissolution of gold as a

gold ammine with 95% recovery. Ammonia

alone does not dissolve the gold.

New Catalysts for Polyolefins

Dow Plastics (Midland, Michigan) have

developed a new process to produce

polyolefins using single-site metallocene

catalysts. Such “constrained geometry”

catalysts are becoming more efficient, are

giving bigger yields and have the big ad-

vantage of not needing supports. Dow’s

new catalysts are cyclopentadienyl tita-

nium complexes with a cation-forming ac-

tivator. This increases the amounts of

higher a-olefins in the product and the new

catalysts can be used to tailor-make poly-

mers with narrow molecular mass distribu-

tions and low crystallinities; however, the

products have broad ranges of polymer

properties e.g. polethylenes with densities

ranging from 0.855-0.97 g cmm3. The cata-

applied catalysis A: General Volume 87 No. 1 - 11 August 1992