Prospect of Molecular Sieves Production using Rice Husk in Bangladesh: A Review

A growing need of molecular sieves, now a day, in many industries of Bangladesh makes the materials most important and attracted special attention. The review explores each step involved in the whole process of molecular sieves preparation from rice husk (RH). Many refineries and chemical industries are using molecular sieves as adsorbent material and process catalyst very efficiently. Rice husk is one of the potential sources of biomass to get a maximum percent of SiO2 that is required to synthesize molecular sieves. 93.2% of SiO2 can be extracted from rice husk ash (RHA). In the fiscal year of 2016-2017, about 6.86 million tons of rice husk are produced in Bangladesh whereas worldwide production of rice husk is approximately 97.24 million tons. Geographical locations, combustion methods, and temperature are influencing factor mainly to get the content of silica and structure of molecular sieves.) Rice husk ash containing amorphous silica is produced at temperatures lower than 800C (500-800C). The chemical method with washing pretreatment and post heat treatment are considered as the most simple and successful SiO2 extraction methods from RH. Different types of molecular sieves; 13x, 3A, 4A & 5A can successfully be synthesized via the widely used hydrothermal method. Molar ratio of ingredients, reaction temperature, time, acid-base media, ageing etc. are key factors to be considered in designing different molecular sieves. Keywords— Molecular sieves, Biomass, Rice husk, Bio-silica, pyrolysis.