CrHZSM-5 Zeolites – Highly Efficient Catalysts for Catalytic Cracking of Isobutane to Produce Light Olefins

Abstract

The CrHZSM-5 catalysts with trace amount of Cr were firstly used for catalytic cracking of isobutane, and the effect of Crloading on the catalytic performances of CrHZSM-5 catalysts for the cracking of isobutane was also studied. The results suggested that when the loading of Cr in the CrHZSM-5 catalysts was less than 0.038 mmol/g Cr, especially at Cr loading of 0.004 mmol/g, both the reactivity of isobutane cracking and the selectivity to light olefins of CrHZSM-5 samples were greatly enhanced compared with the unpromoted HZSM-5, and very high yields of olefins(C 2 +C 3 ) and ethylene were obtained. For instance, the yield of olefins(C 2 +C 3 ) and ethylene reached 56.1% and 30.8%, respectively, at 625°C when 0.004 mmol/g Cr was loaded on HZSM-5 sample.

Catalytic cracking of naphtha: The effect of Fe and Cr impregnated ZSM-5 on olefin selectivity

“…In particular Cr ions are shown to favour aromatization and alkylation reactions. The chromium loadings in our study fall in the range of 0.059-0.409 mmol/g which is higher than the range established by Lu et al [8] for promotion of dehydrogenative cracking which may suggest that higher loadings of chromium above 0.038 mmol/g may promote aromatization reactions. The exact cause, i.e., role of acidity and metal support interaction is not clearly understood and further analysis of the amount of Lewis and Bronsted acid sites as well as XPS and DRIFTS analysis may be required to elucidate the role of the Fe and Cr ions.…”

“…The 2% Cr catalyst has the highest selectivity of ~ 29% of which the composition is mainly toluene and xylenes and small amount of benzene is produced. Lu et al [8] have shown that Cr in small amounts between 0.004 and 0.038 mmol/g alters acidity and plays an important role in promoting cracking of isobutane and dehydrogenation of isobutane to isobutene which is then easily cracked to lighter olefins and is similar to iron in promotional effects. However, the differences in product distribution observed in this study between Fe and Cr modified samples indicate different promotional mechanisms in the cracking of refinery naphtha.…”

“…Other modifications of the ZSM-5 catalyst include alterations of the acidic properties using transition metals [1]. Previous studies conducted by Lu et al [8] have shown that Fe and Cr promoted ZSM-5 have good selectivity to C 2 and C 3 olefins in the cracking of Isobutane at 625 °C. This may be due to metals such as Fe and Cr being able to enhance the dehydrogenative cracking of Isobutane.…”

Conversion of Ethene to Propene on Nickel Ion-loaded Mesoporous Silica Prepared by the Template Ion Exchange Method

“…Supported molybdenum [15] and tungsten oxide [16] have been reported as the catalysts, but their activity was so low as to be observed only in a closed recirculation system. On the other hand, various zeolites have been employed as the catalysts for this reaction [17]. The reaction includes oligomerization/polymerization of lower olefins, subsequent decomposition to yield propene or the others on strong acid sites of zeolites, and selective evolution of propene due to the shape-selectivity of zeolite pores.…”

High Selectivity Production of Propylene from n-Butene: Thermodynamic and Experimental Study Using a Shape Selective Zeolite Catalyst

“…Currently, propylene is mainly produced by steam cracking (61%) and fluid catalytic cracking (FCC) in refineries (34%). It is expected that these traditional methods will be unable to produce enough propylene to satisfy the increasing market demand, and some new methods using other raw materials as the feed are being developed, which include the dehydrogenation of propane [3], conversion of methanol or dimethyl ether to propylene [4], metathesis of ethylene and 2-butene [5], and butene cracking [6][7][8][9][10][11]. Among these methods, the process of butene cracking has attracted much more attention, because of the large and stable supply of butene from FCC and stream cracking processes.…”