Mixed Naphtha/Methanol Feed Used in the Thermal Catalytic/Steam Cracking (TCSC) Process for the Production of Propylene and Ethylene

Abstract

The addition of some methanol to petroleum light naphtha used as feed in the Thermal Catalytic/Steam Cracking(TCSC) process significantly increases the product yield of C 2 -C 4 olefins, particularly that of ethylene ? propylene. However, over 20-25 wt% of methanol content in the naphtha feed, the beneficial effect is attenuated. At relatively high values of contact time, the (Zn-Pd) co-catalyst of the hybrid catalyst exerts noticeably its coke cleaning effect on the zeolite acid sites, particularly when methanol is present in the feed. The product weight ratio (propylene/ethylene) is not affected by such ''moderate'' addition of methanol and remains higher than 1.3.

Catalytic Compatibility of Methanol with Petroleum Naphtha in Mixed Feeds Used in the Thermal-Catalytic/Steam-Cracking (TCSC) Process for the Production of Propylene and Ethylene

“…The preparation of the hybrid catalyst followed the same procedure as described in our previous work [15]. Thus, the final hybrid catalyst resulted from the extrusion of two porous components by using bentonite clay as ''pressurizing'' binder: the main component was the H-ZSM-5 zeolite and the co-catalyst, an yttria-stabilized alumina aerogel loaded with Zn-Pd [15].…”

“…The thermal-catalytic/steam-cracking (TCSC), also formerly named (SDCC or selective deep catalytic cracking, TCC or thermo-catalytic cracking) [2][3][4][5][6], has been developed in our laboratory to selectively produce propylene and ethylene from the same hydrocarbon feeds as in steamcracking. The TCSC process, which combines the (mild) thermal cracking (TC) with the acid cracking promoted by a zeolite-based catalyst, can provide very high yields of light olefins with a propylene-to-ethylene weight ratio much higher than 1.0 while operating at temperatures much lower than those used in the steam cracking technology.…”

“…A ''pressurizing'' binder is used to firmly hold the two types of particles together within the hybrid catalyst extrudates. Some hydrogen species, produced by the co-catalyst surface, can be transferred to the zeolite surface using the experimentally proven effect of ''pore continuum'' [7,8]: these ''hydrogen spillover'' species show some very significant cleaning effect on the coke precursors formed and still adsorbed on the zeolite acid sites [2,[4][5][6].…”

“…Two papers on the TCSC of mixtures of gas oil and a short chain alcohol (and particularly methanol) [14], and of light naphtha and methanol [15], were already published by our group.…”

“…catalytic) cracking. In addition, by measuring some kinetic parameters such as the apparent activation energy, we would like to answer the question that was raised in our previous works [14,15]: when mixed with the light naphtha hydrocarbons, does methanol incorporate itself into the cracking ''hydrocarbon pool'' or react merely by itself as in steam (thermal) cracking?…”