Selected New Developments in Catalyst and Adsorbent Manufacture

Zeolite and molecular sieve science is still a very active area of investigation and numerous new developments are continually appearing. This sechon is topical but not comprehensive, covering some new areas that should be of interest to the reader. 

Early reports include a patent from W.R. Grace describing nano-sized zeolite X and Y, another from Mobil for nano-sized MFl catalysts and a third describing the preparation of nano-sized zeolite L [147-149]. The explosion of nanotechnology research in the past few decades has led to an enormous number of additional 

Microwave Synthesis of Zeolites and Molecular Sieves The use of microwaves holds promise for efficiency improvements in zeolite synthesis due to the rapid heating possible when using microwave radiation [166], The first report of microwave synthesis of zeolites was by Mobil Oil in 1988, which broadly claimed the synthesis of zeolite materials in the presence of a microwave-sympathetic material, such as water or other pro tic component [167]. A number of reports have appeared since, including synthesis of zeolites Y, ZSM-5 [168] and metaUoaluminophosphate-type materials, such as MAPO-5 [169], There have also been extensive investigations in using microwaves for zeoHte membrane synthesis. Recent reviews discuss the progress in microwave zeoHte synthesis [170, 171]. 

Continuous and Semi-Continuous Zeolite Synthesis The first report of continuous synthesis, rather than the usual batch-wise synthesis of zeolites, was from Mobil Oil in 1963 [172]. Another similar patent was from Alcoa Aluminum in 1969 [173]. 

A 1969 paper presented a mathematical crystallization model for the continuous crystallization of zeolite A [174]. The successful implementation of continuous synthesis of zeoHtes must accommodate the relatively slow crystallization rates with the reactor design to allow sufficient residence time at the necessary digestion temperature. A recent patent publication describes continuous zeolite synthesis using microwave heating, which couples the often significant advantages of faster zeolite crystallization under microwave radiation with a continuous synthesis, dewatering and work-up process [175], 

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