R. Le Van Mao

Aromatization of n-butane over new LD-HBS catalysts. Effect of the gallium oxide support

It is shown that even “pure” quartz, other silicas or aluminas can enhance the aromatization activity of a ZSM-5 zeolite. Incorporation of gallium oxide onto these supports increases further the production of aromatics. The use of supported gallium oxide co-catalyst obtained by co-evaporation of a colloidal silica and a Ga salt has led to extremely high aromatization performance for the hybrid catalyst.

Synthesis of methyl terbutyl ether (MTBE) over triflic acid loaded ZSM-5 and y zeolites

Triflic acid loaded Y-type zeolite appears to be as active as the Amberlysi 15 in the (gas phase) synthesis of MTBE. However, the zeolite catalyst produces less by-products and is more thermally stable than the resin based catalyst.

Selective deep catalytic cracking process (SDCC) of petroleum feedstocks for the production of light olefins. I. The Catlever effect obtained with a two reaction-zones system on the conversion of n-hexane

The “n-hexane and steam” gaseous mixture was first sent through a precatalytic zone containing quartz beads (temperature T1), and then through a catalyst bed (T2). The latter contained a ZSM5 zeolite or a zeolite-containing hybrid catalyst. By moderately increasing T1 (T2 being kept constant), significant increases in the total n-hexane conversion and in the total yield of light olefins were obtained. The ethylene/propylene product ratio could be varied widely, for instance, from 1.0 to 2.0 by varying T1 from 660 to 720 °C. Such temperature effect of zone I on the overall process performance was explained by the formation of selectivity modifiers such as diolefins. With the hybrid catalyst, the enhanced production of light olefins was also assigned to the formation of large olefins on the Cr–Al-containing cocatalyst.

Selective Deep Catalytic Cracking Process of Hydrocarbon Feedstocks for the Production of Light Olefins: II. Cooperative Effect of Thermal Cracking and Catalytic Reactions Observed in a 1-Zone Reactor

Hybrid catalysts comprising a chromium-based cocatalyst and a silica-rich ZSM-5 zeolite, when doped with lithium, showed quite a high on-stream stability even at a relatively high reaction temperature (735 °C). The cooperative effect of the thermal cracking and the catalytic reactions, and the interactions between the two catalyst components of the hybrid catalyst, resulted in maximum production of light olefins when the hybrid catalyst contained ∼40 wt% of zeolite. The main chemical links between the thermal cracking (TC) and the catalytic reactions were the conversions of diolefins and large olefins, the latter being produced by the TC and the active sites of the chromium-bearing cocatalyst, respectively.

1H broad-line and MAS NMR: application to the study of acid sites of desilicated zeolite ZSM-5

Broad-line1H NMR study of desilicated zeolite ZSM-5 was carried out as a function of the number of adsorbed water molecules in amounts lower than or equal to that of the Brønsted acid sites. The dissociation coefficient of the acid OH groups, currently associated with the acid strength, was shown not to be affected by the selective removal of Si from the zeolite ZSM-5 framework which resulted in more Brønsted acid sites per unit surface area. On the other hand, by using MAS NMR, bridging Brønsted acid sites hydrogen-bonded to the zeolite framework were identified on the “anhydrous” surface of the desilicated ZSM-5. Moreover, MAS NMR spectra of the desilicated zeolite partially rehydrated showed the presence of some Lewis acid sites.

AC3B Technology for Direct Liquefaction of Lignocellulosic Biomass: New Concepts of Coupling and Decoupling of Catalytic/Chemical Reactions for Obtaining a Very High Overall Performance

The acid-catalyzed conversion of lignocellulosic biomass (AC3B) process has been developed for the direct liquefaction of lignocellulosic biomass. In the original version, the main products, ethyl esters, are produced in acidic medium containing ethanol, using a one-pot conversion system. Our research strategy for obtaining a high overall performance is based on two general concepts: (a) coupling of catalytic/chemical reactions that lead to desired products and (b) decoupling of reactions that produce unwanted products, by decreasing the effectiveness of these reactions. Concept (a) is realized by using oxidizers (hydrogen peroxide and Fenton’s reagent) that promote a higher production of carboxylic acids as main intermediates, while concept (b) contributes to a significant decrease of undesired formation of polymeric products. As result of these reaction coupling and decoupling, the overall yield of liquid products has been multiplied by a factor of 2.5 (from 27 to over 70 wt%). Not only the yields of products from cellulose and hemicellulose components experience considerable increases, but also the lignin component starts undergoing a noticeable conversion. Essentially, the AC3B process, in the most recent version, consumes ethanol that is partly used to produce liquid fuels and chemicals from lignocellulosic biomass. The other amount of feed ethanol is converted—via diethyl ether and over ZSM-5-based catalysts—into aromatics-rich gasoline and liquefied petroleum gas—grade hydrocarbons.Graphical AbstractSequence of actions that have significantly improved the total product yield (RP): AC = acidic medium, HP = addition of hydrogen peroxide, DL-st = use of a delignification step, FR = use of a Fenton-type reagent, PIn = use of a polymerization inhibitor