Formation of High Molecular Weight Byproducts during the Pyrolysis and Oxidative Pyrolysis of CH3Cl

Abstract

The chlorine-catalyzed oxidative pyrolysis (CCOP) process was recently developed as a method to convert methane, the major component in natural gas, into more valuable products such as ethylene, acetylene, and vinyl chloride. The CCOP process involves the initial chlorination of CH{sub 4} into CH{sub 3}Cl (as well as other chlorinated methanes), followed by the oxidative pyrolysis of CH{sub 3}Cl into products such as C{sub 2}H{sub 4}, C{sub 2}H{sub 2} and C{sub 2}H{sub 3}Cl, and HCl. The formation of high molecular weight byproducts in the pyrolysis and oxidative pyrolysis of CH{sub 3}Cl was studied experimentally in an isothermal, atmospheric pressure flow reactor. The effects of process variables such as residence time (0.43--0.86 s), temperature (850--910 C), and oxygen concentration (0.0--6.72%) on product formation were investigated. The concentration profiles of the high molecular weight byproducts, up to naphthalenes and substituted naphthalenes, together with those for the major products, were determined by withdrawing samples from within the reactor using a heated microprobe, followed by gas analysis using on-line gas chromatography/mass spectrometry. The presence of oxygen in the feed initially reduced the formation of all the high molecular weight products. However, the levels of acetylenic and aromatic products were subsequently enhanced at higher oxygenmore » loadings. Since no coke was observed in the presence of O{sub 2}, the suppression of coke formation by O{sub 2} cannot be explained by the diminished production of aromatics; instead, surface reactions of O{sub 2} are implicated in the apparent decrease in the production of coke.« less