Vinylidene chloride copolymer-based carbon molecular sieve adsorbent compositions and processes therefor

Abstract

Novel carbon molecular sieve (CMS) compositions comprising carbonized vinylidene chloride copolymer having micropores with an average micropore size ranging from 3.0 to 5.0 angstroms. These materials offer capability in separations of gas mixtures including, for example, propane / propylene; nitrogen / methane; and ethane / ethylene. Such may be prepared by a process wherein vinylidene chloride copolymer beads, melt extruded film or fiber are pretreated to form a precursor that is finally carbonized at high temperature. Preselection or knowledge of precursor crystallinity and attained maximum pyrolysis temperature enables preselection or knowledge of a average micropore size, according to the equation sigma= 6.09 +(0.0275*C) - (0.00233*T), wherein sigma is the average micropore size in Angstroms, C is the crystallinity percentage and T is the attained maximum pyrolysis temperature in degrees Celsius, provided that crystallinity percentage ranges from 25 to 75 and temperature in degrees Celsius ranges from 800 to 1700. The beads, fibers or film may be ground, post-pyrolysis, and combined with a non-coating binder to form extruded pellets, or alternatively the fibers may be woven, either before or after pre-treatment, to form a woven fiber sheet which is thereafter pyrolyzed to form a woven fiber adsorbent.

Description

[0001] Cross References to Related Applications [0002] This application claims a U.S. provisional patent entitled "CARBONIZED VINYLIDENE CHLORIDE COPOLYMER-BASED MOLECULARSIEVE ADSORBENT COMPOSITIONS AND PROCESSES THEREFOR," filed June 30, 2014 Benefit of Application No. 62 / 018,828, which is hereby incorporated by reference in its entirety. technical field [0003] The present invention relates to the field of molecular sieve compositions. More specifically, it relates to carbon molecular sieve compositions based on vinylidene chloride copolymers. Background technique [0004] Over the years, researchers have sought means to separate gas mixtures for use as either starting materials or as products. A material that has attracted much attention as a means of such separations has been carbon molecular sieves (CMS). These CMSs can be prepared from a variety of resins and pyrolyzed at various temperatures and / or under various conditions. Pyrolysis reduces the resin to pure...

AI Technical Summary

Problems solved by technology

However, previous researchers have not established that polyvinylidene chloride copolymer-based CMSs are capable of effectively and / or efficiently separating gas pairs of much smaller molecules, including, in a non-limiting example, C 3 h 8 / C 3 h 6 、C 2 h 6 / C 2 h 4 and / or CH 4 / N 2

[0011] Accordingly, it will be found that the prior art does not recognize carbonized PVDC having an average pore size as specified to be suitable for small molecule separations, i.e. especially having to Molecules in a representative molecular diameter range

Furthermore, the prior art does not disclose a method for preparing carbonized PVDC CMS that can be easily and precisely tuned for various molecular separations in this representative molecular diameter range, and in specific embodiments, its Also exhibits stable geometries, whether in the form of pellets, pellets, unsupported membranes, unsupported membranes, woven fibrous sheets, etc.

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