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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-C 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. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

HMCM-22 zeolite with a high Si/Al2 ratio (158) was applied to the 1-butene cracking reaction in a fixed-bed reactor. On basis of the product distribution, the main reaction pathways of C4 alkenes catalytic transforming on HMCM-22 were proposed. Also, the preferences of the reaction pathways influenced by the temperature and conversion level were discussed, which could provide good guidance on enhancing the propene production. [ABSTRACT FROM AUTHOR]

HY zeolite modified by La2O3 on olefin alkylation of thiophenic sulfur in fluid catalytic cracking (FCC) gasoline was studied in the micro fixed-bed reactor. Reaction pressure 1.5 MPa, reaction temperature 180 °C, WHSV 3.5 h−1, using HY zeolite modified by 2% La2O3, the conversion of thiophene sulfur promoted nearly 10% with good selectivity, comparing with no-modified by La2O3. Acidity of modification of HY zeolite with La2O3 was tested in Pyridine–IR, it showed that increasing the amount of weak Bronsted (B) acid and the ratio of total B acid with total Lewis (L) acid could strengthen the hydrogen transfer activity of the catalyst, which leaded to improving the capacity of thiophene alkylation. The X-ray diffraction (XRD) results showed that the structure of catalysts could be optimized by loaded proper amount of La2O3 for promoting the acidic properties of HY zeolite. [ABSTRACT FROM AUTHOR]

To develop a novel additive that has excellent olefin reduction capability for FCC gasoline without loss in octane number, different additives based on magnesia-alumina spinel were prepared by sol–gel method. The catalytic activities of additives for reducing the olefins in the fluid catalytic cracking (FCC) gasoline were assessed in a micro fixed bed reactor and the influences of Mg/Al ratio, the modification of La and Nb on the additive performance were studied as well. Results indicated that the additive with the Mg/Al ratio of 1.0 possessed the highest reaction activity due to the formation of MgAl2O4·MgO spinel. The activities of additives modified by La and Nb were also improved, for example, the reaction activity of additive with 4–5 wt% La was 34%. The XRD results showed that the effect of reducing olefin was the function of both MgAl2O4·MgO spinel and La m O n or MgAl2O4·MgO spinel and Nb2O5. [ABSTRACT FROM AUTHOR]

The CrHZSM-5 catalysts with trace amount of Cr were firstly used for catalytic cracking of isobutane, and the effect of Cr-loading 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(C2+C3) and ethylene were obtained. For instance, the yield of olefins(C2+C3) and ethylene reached 56.1% and 30.8%, respectively, at 625 °C when 0.004 mmol/g Cr was loaded on HZSM-5 sample. [ABSTRACT FROM AUTHOR]

The high performance of hybrid catalysts in the selective deep catalytic cracking ofn-hexane andn-heptane - used herein as model molecules for petroleum naphthas - is due to the pore continuum effect created by the close connection between the micropores of the acidified silicalite crystallites and the mesopores of the cocatalyst particles, located in fixed positions within a rigid matrix. The resulting enhanced conversion over the “micro-meso” hybrid catalyst is obtained regardless of the surface composition of the mesoporous cocatalyst or the molecular nature of the feed. However, it disappears when the two catalyst components are both mesoporous materials, i.e. in the case of a “meso-meso” hybrid catalyst. The main active component of the mesoporous cocatalyst, molybdenum oxide supported on silica-alumina, shows surface acidity of both nature (Bronsted and Lewis). Cerium oxide incorporated as dopant, has as main catalytic effect to increase the selectivity to light olefins, while the production of aromatics significantly decreases. However, when the ratio of [Ce]/[Mo] molar concentrations is higher than 0.8, the?yield of product BTX aromatics rapidly increase at the expenses of that of light olefins. On the other hand, Ce loading onto the microporous silicalite or ZSM5 zeolite results in the same catalytic behavior as with the cerium-doped cocatalyst. [ABSTRACT FROM AUTHOR]

In this paper we report about coke formation during catalytic cracking of n-hexane and 1-hexene over acidic ultrastable Y zeolite in a fixed-bed reactor. The study is based on a classification between coke precursors, whose amount is estimated through volatilisation by nitrogen purging, and coke, large formed coke molecules that remain during nitrogen purging even at 873 K and whose amount is estimated by oxidation at that temperature. The role of coke precursors on the coking process and catalytic cracking reaction is discussed as well as differences in coking tendencies between the two reactants. The results show that the amount of coke precursors and/or coke may decrease with reaction temperature resulting into a reversal of the coking dependence upon temperature. [ABSTRACT FROM AUTHOR]

The preparation of light alkenes by the gas phase oxidative cracking (GOC) or catalytic oxidative cracking (COC) of model high hydrocarbons (hexane, cyclohexane, isooctane and decane in the GOC process and hexane in the COC process) was investigated in this paper. The selection for the feed in the GOC process was flexible. Excellent conversion of hydrocarbons (over 85%) and high yield of light alkenes (about 50%) were obtained in the GOC of various hydrocarbons including cyclohexane at 750°C. In the GOC process, the utilization ratio of the carbon resources was high; CO dominated the produced COX (the selectivity to CO2 was always below 1%); and the total selectivity to light alkenes and CO was near or over 70%. In the COC of hexane over three typical catalysts (HZSM-5, 10% La2O3/HZSM-5 and 0.25% Li/MgO), the selectivity to COX was hard to decrease and the conversion of hexane and yield of light alkenes could not compete with those in the GOC process. With the addition of H2 in the feed, the selectivity to COX was reduced below 5% over 0.1% Pt/HZSM-5 or 0.1% Pt/MgAl2O4 catalyst. The latter catalyst was superior to the former catalyst due to its perfect performance at high temperature, and with the latter, excellent selectivity to light alkenes (70%) and the conversion of hexane (92%) were achieved at 850°C (a yield of light alkenes of 64%, correspondingly). [ABSTRACT FROM AUTHOR]

The deactivation of an ultrastable Y-zeolite during cracking of n-octane, isooctane and 1-octene was studied in a fixed-bed reactor. The relative reactivities of the three reactants in increasing order were n-octane < isooctane < 1-octene. At high residence times, complete conversion was achieved followed by a relatively slow decline that, in fact, presented a falsified deactivation picture. On the other hand, a surprising olefin yield increase with time onstream was observed, i.e., isobutene during isooctane cracking and octene isomers in the case of 1-octene. The isobutene yield increase was assigned to preferential deactivation of strong acid sites that allowed primary products to desorb into the gas phase, increasing their apparent yield rather than undergo secondary reactions. Similarly, 1-octene isomers showed a yield increase with time onstream due to stronger deactivation of cracking reactions than isomerization. [ABSTRACT FROM AUTHOR]

The deposition of metal contaminants (e.g., Ni, V, and Fe) from the hydrocarbon feed causes the deactivation of fluid catalytic cracking (FCC) catalyst used in petroleum refining. It is very important to understand the changes in the morphology and chemical composition on the catalyst surface and how these structural and chemical changes affect the catalyst performance. In this research, metal-contaminated FCC catalysts from a commercial unit have been characterized using AFM together with SEM–EDS. The AFM images showed the surface pores as well as the features that surround the pore's entrance on the catalyst surface. Catalyst surface contains debris that appear as bright spots in AFM images. SEM–EDS results have shown the presence of iron in these bright spots. Fe enrichment at the catalyst particle surface was also confirmed by XPS analyses. [ABSTRACT FROM AUTHOR]

Mesoporous AlMSU-X molecular sieves with high acidity have been prepared from preformed beta nanoclusters under strong acidic conditions in the presence of nonionic TX-100 as structure directors. These materials were characterized by XRD, HRTEM, N2-adsorption, 27Al MAS NMR, NH3-TPD, IR-pyridine adsorption and catalytic cracking of cumene and 1,3,5-triisopropylbenzene. The experimental results showed that Al heteroatoms had been successfully incorporated into the framework structure of mesoporous MSU-X, and so-produced catalysts exhibited superior catalytic properties. [ABSTRACT FROM AUTHOR]

Homemade BEA(HTS) catalysts prepared by the hydrothermal synthesis method exhibited much higher activity than commercial BEA, USY and ZSM-5 in catalytic cracking of n-heptane. It is characteristic that BEA(HTS) has a much larger amount of Brönsted acid sites than other zeolites. This is related to the high activity. [ABSTRACT FROM AUTHOR]