From propylene , ammonia and air montecatini edison’s highly active, low bulk density fluid catalyst gives acrylonitrile at lowest cost
Giorgio Caporali , Montecatini Edison S.p.A,Milan ,Italy
Since about 1960,the leading route to acrylonitrile has been by catalytic reaction of propylene with ammonia and air。 Montedison’s process was first commercialized in 1968 in their 60,000-ton/year plant. This process has been licensed to Paular CO. in Spain for a 40,000-ton/year plant and montedison is planning another plant for themselves with 100,00 ton/year capacity.
Although modern commercial acrylonitrile process appear similar and produce very pure product ,each is characterized by its own original features:
Catalyst system and rector technique
Nature, condition and sequence of recovery and purification step.
These step and features in the Montecatini Edison process are shown in FIG .1 and other data may be found in the literature.
RAW materials . There are only three reactants, the oxygen being supplied as air and no stream is repuired as diluent . Technical grade propylene(92-93 percent,the balance being propane ) and anhydrous fertilizer grade ammonia are satisfactory. Higher olefins are undesirable since they make byproducts which burden the purification steps. The there gaseous reactants are premixed and fed to the bottom of the reactors.
Reactors. Large size fluid bed catalytic reactors are used which provide:
A bottom distribution plate for supporting the catalyst and distributing the gas;
A top set of multiple effect cyclones, with dip legs ,recover and return the catalyst to near the bottom of the reaction zone;
Special sets of heat exchangers in the fluid bed for reaction heat removal and steam generation.
Reaction conditions . Typical reaction condition values are: 420-460。C ; 2kg/cm2 absolute pressure ;feed composition ranging from 6.7-8 vol. percent propylene ,0.2-0.6percent propane,7.5-9percent ammonia,82.5-86percent air (which gives a minimum excess ammonia with respect to propylene and about 50percent stoichiometric excess air); liner gas velocity between 1 and 2 feet per second(based on empty reactor with total inlet gases volume at average operating conditions);and contact time in the order of a few second,e.g.,2to 6 second when gas volume is based as stated above, at the average operating conditions and referred to the volume of the packed catalyst.
Catalyst The catalyst consists of oxygenated compounds of tellurium, cerium and molybdenum supported on a microspheroidal silica carrier. It contains about 20-30wt./wt. percent of active elements and has has a bulk density. The catalyst is presently produced by in facilities near the acrylonitrile plant.
拒绝机译 拒绝机译 分不是问题,有诚意的来,机译的靠边站!!!