Clarence D. Chang

The conversion of methanol and other O-compounds to hydrocarbons over zeolite catalysts

Abstract The conversion of methanol and other O-compounds to C 2 ue5f8C 10 hydrocarbons using a new class of shape-selective zeolites is reported. Methanol, dimethyl ether, or an equilibrium mixture thereof appears to be converted in a first reaction sequence to olefins predominantly in the C 2 ue5f8C 5 range. In the final steps of the reaction path, the C 2 ue5f8C 5 olefins are converted to paraffins, aromatics, cycloparaffins and C 6 + olefins. The final hydrocarbons are largely in the gasoline (C 4 ue5f8C 10 ) boiling range. The thermochemistry of the methanol to hydrocarbon reaction is described and possible reaction mechanisms are discussed.

Hydrocarbons from Methanol

Abstract The conversion of methanol to hydrocarbons is a remarkable reaction. The mechanism involves C-C bond formation from C1 fragments generated in the presence of certain acidic catalysts and reagents. The precise nature of these reactive C1 species is unknown at present and is the subject of lively debate. The considerable diversity of current opinion will become apparent from the following account.

Methanol Conversion to Light Olefins

Abstract Light olefins will play a dominant role in any future methanol-based chemicals economy. Olefins are initial products in the conversion of methanol to hydrocarbons over zeolite catalysts [1]. The overall reaction path may be represented by

Methanol conversion to olefins over ZSM-5 I. Effect of temperature and zeolite SiO2/Al2O3

Abstract The conversion of methanol to olefins over ZSM-5 zeolites is described. The interdependence of reaction parameters T , P , contact time, and catalyst Bronsted acidity in controlling olefin selectivity is characterized and interpreted. It is found that olefin formation can be decoupled from aromatization via a combination of high temperature and low catalyst acidity.

Synthesis gas conversion to aromatic hydrocarbons

Abstract The conversion of synthesis gas to aromatic hydrocarbons over a new class of catalysts comprising a CO reduction function combined with a ZSM-5 class zeolite is reported. The polystep nature of the catalysis is analyzed.

The conversion of methanol and other O-compounds to hydrocarbons over zeolite catalysts: II. Pressure effects

Abstract The effect of pressure on the conversion of methanol to hydrocarbons over ZSM-5 class zeolites is reported. Varying reactant partial pressure affects mainly the relative rates of the dehydration and aromatization steps in the reaction sequence.

Studies on the mechanism of ZSM-5 formation

The nucleation of (Al-free) zeolite precursor gels was studied using X-ray diffraction,29Si FT-NMR, and ion exchange. Results suggest that in ZSM-5 nucleation, the channel intersections are first formed. These clathrate-like units, each containing essentially one TPA+ cation, are initially randomly connected, but progressively “anneal” with rearrangement under the influence of OH− ions to form the ZSM-5 framework.

Isomorphous substitution in zeolite frameworks: II. Catalytic properties of [B]ZSM-5

The catalytic activity of [B]ZSM-5 is examined for a number of acid-catalyzed reactions: n-hexane cracking, xylene isomerization, ethylbenzene dealkylation, cyclopropane isomerization, and hydrocarbon formation from methanol. In each case, it was determined that catalytic activity was due mainly, if not entirely, to trace amounts (80–580 ppm) of framework Al. The remarkable effectiveness of minute concentrations of framework Al in ZSM-5 zeolites has had little recognition until recently.

A kinetic model for methanol conversion to hydrocarbons

Abstract A phenomenological kinetic model is developed which describes the reaction path for methanol conversion to hydrocarbons over ZSM-5 class zeolites. The model correctly predicts conversion and selectivities over a wide range of pressure.

Methanol conversion to olefins over ZSM-5: II. Olefin distribution

The distribution of olefins from methanol conversion over ZSM-5 zeolite is examined. Thermodynamic equilibrium is approached at low conversion levels. With increasing conversion, olefin distribution is governed by kinetics, due to autocatalysis and competitive sorption of water. Ethylene is the initial olefin.