Sagar B. Gadewar

Improved light olefin yield from methyl bromide coupling over modified SAPO-34 molecular sieves

As an alternative to the partial oxidation of methane to synthesis gas followed by methanol synthesis and the subsequent generation of olefins, we have studied the production of light olefins (ethylene and propylene) from the reaction of methyl bromide over various modified microporous silico-aluminophosphate molecular-sieve catalysts with an emphasis on SAPO-34. Some comparisons of methyl halides and methanol as reaction intermediates in their conversion to olefins are presented. Increasing the ratio of Si/Al and incorporation of Co into the catalyst framework improved the methyl bromide yield of light olefins over that obtained using standard SAPO-34.

A systematic method for reaction invariants and mole balances for complex chemistries

Abstract Reaction invariants are quantities that take the same values before, during and after a reaction. We identify a set of reaction invariants that are linear transformations of the species mole numbers. The material balances for chemically reacting mixtures correspond exactly to equating these reaction invariants before and after reaction has taken place. We present a systematic method for determining these reaction invariants from any postulated set of chemical reactions. The strategy presented not only helps in checking the consistency of experimental data, and the reaction chemistry but also greatly simplifies the task of writing material balances for complex reaction chemistries. For examples where the reaction chemistry is not known, we employ Aris and Mahs (Ind. Eng. Chem. Fundam. 2 (1963) 90) classic method to determine a candidate set of chemical equations. Application of reaction invariants in validating proposed reaction chemistry is discussed. One of the important applications of this method is the automation of mole balances in the conceptual design of chemical processes.

Process Alternatives for Coupling Reaction and Distillation

Areactive distillation column combines reaction with distillation, and is known to be advantageous for some reaction systems, but not for others. Sometimes it is a breakthrough technology, yet in others a reactive distillation column does not give pure products, and is therefore infeasible. For cases where a reactive distillation column is not feasible, it is useful to determine alternatives with combined reaction and distillation that rely on conventional distillation systems to give pure products. The advantage of such alternatives is the use of simultaneous reaction and distillation to improve the yields and/or selectivities to products, and also that they require smaller recycle flows. Many alternatives can be generated with a potential advantage over the conventional process of reaction followed by distillation. During the conceptual design stage of a process it is vital to decide quickly whether reactive distillation is likely to be a good process concept. We describe an approach that first determines feasible product splits for single-feed continuous reactive distillation. For chemistries where one or more products cannot be obtained as a pure product stream from the column, the geometric method of attainable regions is used to determine the feasible products and alternatives using simultaneous reaction and distillation. These alternatives are then combined with conventional separation systems to get pure products. Using systematic methods, a large number of flowsheets are generated, which are then evaluated for feasibility using rules, heuristics and mass balances.