Continuous Nitration of Alternative Cellulose Feedstocks

Dr. Joost van Lingen | TNO

WP20-1249

Objective

Hundreds of tons of high quality nitrocellulose (NC) are required yearly for the gun and rocket propellant industry. Typically NC is produced in batch processes with large excesses of nitrating acids. This process has been used by NC plants for decades and has several drawbacks: waste streams related to NC production, including NC fines, acids and salts; requires purified cellulose which generates additional waste streams related to this purification; and variabilities in the feedstock and in the batch process are reflected in variability in the NC. These drawbacks may be addressed by moving from batch processing to continuous processing, as well as, alternative, less variable cellulose feedstocks. One of the advantages of continuous processing is the improved control over reaction conditions. This possibly allows reduction of the required nitration acid excess, directly reducing waste streams. On top of that, process induced variation of the NC product can significantly be reduced using a continuous process instead of a batch process. Alternative cellulose feedstocks include bacterial cellulose (BC) and microcrystalline cellulose (MCC). The latter is a processed form of cellulose for which is has been demonstrated that in can be nitrated continuously to microcrystalline nitrocellulose (MCNC). BC is obtained from bacteria as a high purity material and it requires no extensive chemical extraction process that produces additional waste streams. Both are more pure than cellulose used for commercial NC production. Consequently, the NC may have a higher purity, possibly contributing to longer shelf life and better performance. The primary objective of this project is to demonstrate that NC based on alternative cellulose feedstocks like MCC and BC has less variable properties compared to NC from conventional cellulose. The secondary objective is show that it is feasible to nitrate BC feedstocks to a comparable or superior performance as conventional NC using continuous processing techniques.

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Technical Approach

BC will be produced using known methods on a scale suitable for continuous nitration. In parallel, alternative BC production/processing methods will be assessed to determine their effect on the quality parameters of the resulting NC. The alternative cellulose will be chemically and physically analyzed and compared to traditional cellulose. Optimal settings for a continuous nitration setup will be determined using a design of experiments approach with small scale batch syntheses using nitrogen content as response parameter. With these settings, BC will be nitrated in a continuous setup. Reproducibility will be demonstrated via the standard deviations in nitrogen content measurements. The NCs will also be thermally characterized.

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Benefits

This work will indicate if alternative cellulose feedstocks can yield NC with comparable or superior performance as NC produced using traditional methods and materials. Furthermore, it will be demonstrated if use of alternative cellulose sources combined with continuous processing results in NC with reduced variability. The results of this work may be used by NC producers to: reduce waste streams related to the production of NC; reduce variation in produced NC; extend the availability of feedstock sources; and obtain NC of superior purity, performance and shelf life.

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Points of Contact

Principal Investigator

Dr. Joost Van Lingen

TNO Defence, Security & Safety

Phone: +31888661299

Fax: +31888666942

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