Richard R. Schehl

Direct Conversion of Methane to Liquid Hydrocarbons Through Chlorocarbon Intermediates

Abstract The chemical activation of methane and its subsequent conversion to oxygenates or higher hydrocarbons have been the objects of intensive research in the past several years. At the Pittsburgh Energy Technology Center, a novel combination of two existing process concepts has been examined and appears capable of producing higher hydrocarbons from methane with high yield and selectivity. Methane, oxygen, and hydrogen chloride are reacted over an oxyhydrochlorination catalyst in the first stage to produce methyl chloride and water. In the second stage, the methyl chloride is converted to higher hydrocarbons, namely paraffins, olefins, aromatics, and cycloparaffins, over a zeolite, such as ZSM-5. In the process concept described, the final hydrocarbon mixture is largely in the gasoline (C 4 , C 10 ) boiling range.

Secondary reactions on metal-zeolite catalysts used in synthesis gas conversion☆

The mechanism of synthesis gas conversion over cobalt-ZSM-5 catalysts to gasoline-range hydrocarbons has been examined. A correlation exists between the methane yield and the percentage aromatics in the liquid hydrocarbon product. This could be due to heat transfer effects or to the hydrogenolysis of propane and butane over cobalt, leading to the formation of additional methane. The formation of additional alkanes (propane and butane) is known to accompany the aromatization process. The percentage of methane made by the bifunctional catalyst 4.2% CoSiO2 + ZSM-5 was 1.7 times that made by the CoSiOm2 catalyst with a feed of H2CO = 1 at 280 °C, 21 atm, and WHSV = 0.77. An attempt was made to inhibit secondary hydrogenolysis reactions by the addition of copper to the cobalt catalyst. Under similar process conditions, this provided a very small help in keeping down the increase in percentage of methane upon the addition of ZSM-5. Addition of 5 and 10% propane to the synthesis gas showed no additional methane made by hydrogenolysis. If indeed some of the methane produced over cobalt-ZSM-5 catalysts is coming from hydrogenolysis of light alkanes, it is a small amount.

Hydrodynamic study in a slurry-bubble-column reactor

Abstract Local gas holdup, bubble diameter and bubble rise velocity in the nitrogen/Drakeol-10 oil system were measured at both laboratory (ambient temperature and pressure) and industrially relevant (high temperature and pressure) conditions using a dual conductivity probe in a slurry-bubble-column reactor. It was found that a constant superficial velocity, the Sauter mean bubble diameter decreases with increasing pressure and temperature. The bubble rise velocity significantly decreases as the pressure increases. Large bubbles rise faster than smaller bubbles. Akita and Yoshidas correlation [1] was utilized to compute the bubble size. Predicted values agree with the experimental data at high temperature.

Influence of preparative procedure on the activity and selectivity of FeZSM-5 catalysts in syngas conversion

Abstract The ZSM-5 supported iron catalysts have been investigated with respect to physical and chemical properties and to activity and product selectivity for conversion of synthesis gas to hydrocarbon products. The catalyst preparations consisted of (1) direct decomposition of (C5H5Fe(CO)2)2 on ZSM-5, (2) impregnation of ZSM-5 with an aqueous solution of iron nitrate, and (3) physical admixture of precipitated iron oxide with ZSM-5. Some H2 and CO chemisorption studies and magnetization measurements were conducted to measure the average metal crystallite size. At the metal loading of about 8 wt%, the catalysts prepared by the first method produced higher metal dispersion compared to the other two methods of preparation, although the amount of aromatic compounds in liquid hydrocarbon products was very low. Infrared studies of chemisorbed pyridine on these samples indicate that ion exchange of Fen+ for acidic protons occurs in aqueous solution impregnated catalysts, while no ion exchange is found in organometallic impregnated or physically admixed catalysts.

Slurry phase Fischer-Tropsch synthesis with iron-manganese catalysts

Abstract Synthesis gas was reacted over different compositions of iron-manganese Fischer-Tropsch catalysts in a slurry reactor. The reactor operates in a back-mixed mode with a continuous flow of feed gas through the catalyst suspended in the liquid medium. Four catalysts with iron-manganese ratios of 57/43, 44/56, 22/78, and 10/90 were investigated at identical process conditions after a standard activation procedure. With time on stream for each catalyst system, hydrogenation of olefins occurred, along with olefin isomerization reactions. Activity, selectivity, and stability are discussed in general. Analyses of used catalyst samples are also reported.

ULTRASONIC CHARACTERIZATION OF THREE-PHASE SLURRIES

An ultrasonic technique is under development for measuring solids concentration in a three-phase slurry reactor. Preliminary measurements have been made on slurries consisting of water, glass beads, and air bubbles. The data show that both the sound speed and attenuation are well-defined functions of both the solid and gas concentrations in the slurries. A simple model is proposed to correlate the solids concentration with the measured ultrasonic signals.

CARBON MONOXIDE HYDROGENATION OVER NA-MN-NI CATALYSTS : EFFECTS OF CATALYST PREPARATION METHODS ON THE C2+ OXYGENATE SELECTIVITY

Abstract The effect of catalyst preparation methods on carbon monoxide hydrogenation selectivity over na-mn-ni catalysts has been studied. the sio2-supported ni and mn-ni catalysts prepared from impregnation exhibited high methanation and hydrocarbon synthesis selectivity. the mn-ni catalysts prepared from coprecipitation of manganese and nickel nitrates with sodium carbonate showed high selectivity for c2+ oxygenate synthesis. temperature-programmed desorption studies revealed that hydrogen chemisorption on the coprecipitated catalysts was highly activated. the results suggest that highly activated hydrogen chemisorption may lead to a hydrogen-deficient surface which would favor carbon monoxide insertion relative to hydrogenation.

ULTRASONIC CHARACTERIZATIONS OF GAS HOLDUP IN A BUBBLE COLUMN REACTOR

An indirect method of measuring gas holdup in gas-liquid bubble column reactors has been developed. This technique is based on the analysis of the ultrasonic wave transmitted through the two-phase flow. Gas holdup measurements have been made on water-nitrogen bubble system at ambient conditions. The data clearly show that the attenuation of the sound is a well-defined function of the gas holdup in the bubble column for homogeneous flow regime only (i.e., the superficial gas velocity is 4 cm/sec or less).

Measurements of solids concentration in a three-phase reactor by an ultrasonic technique

An ultrasonic technique was developed to measure the concentration of solids in a three-phase slurry reactor. Preliminary measurements were taken on slurries consisting of water, glass beads, and nitrogen bubbles. The data show that the speed and attenuation of the sound are well defined functions of the solid and gas concentrations in the slurries. A simple model is proposed to correlate the concentration of solids with the measured characteristics of the ultrasonic signals.

Characterization of Cu−Rh/SiO2 by temperature-programmed desorption (TPD) of hydrogen

The presence of Cu on Rh/SiO2 inhibited H2 chemisorption at 303 K and suppressed CO hydrogenation. TPD study shows that chemisorption of H2 on Cu−Rh/SiO2 is an activated process at 303 K.AbstractПрисутствие Cu на Rh/SiO2 ингибирует хемосорбцию H2 при 303 К и подавляет гидрирование CO. Результаты исследований ТПД свидетельствуют о том, что хемосорбция H2 на Cu−Rh/SiO2 является активированным процессом при температуре 303 К.