Yee Soong

Methyl formate hydrogenolysis for low-temperature methanol synthesis

Abstract The hydrogenolysis of methyl formate to methanol was studied in a liquid-phase reactor using a heterogeneous copper catalyst. This reaction is part of a process to produce methanol from synthesis gas starting with the carbonylation of methanol to methyl formate. Raney copper was compared with copper-chromite for hydrogenolysis activity at 110 to 160°C. The inhibition of the hydrogenolysis reaction by carbon monoxide was found to be lower at higher temperatures. A rate equation was derived to include this temperature dependence. Also, carbon monoxide made by a side reaction, the decarbonylation of methyl formate, was carefully measured and shown to account for only 1 to 2% of the total methanol produced at these temperatures.

Numerical simulation and experimental validation of solids flows in a bubbling fluidized bed

Abstract A transient two-phase simulation reactor model for describing the hydrodynamics in a bubbling-fluidized bed was performed. A summary of the numerical method refined for over a decade is presented. The hydrodynamic model, based on the two-fluid theory, was validated with regards to the solids flow patterns in a fluidized bed operated under isothermal conditions. The predicted trends compared well with the experimental solids velocity field. The simulation appears to mimic experimental results accurately: both the simulation and the experiment show that the solids motion follows a `gulf–stream pattern with solids rising upward in the middle of the bed and falling downward near the side walls. The weak vortex patterns observed in the lower portion of the bed have also been simulated. Comparison of predicted and experimental axial solids velocities were in generally good agreement. This good agreement was found to be a function of the solids viscosity and not of the nonuniform inlet gas velocity.

Capture of carbon dioxide by solid amine sorbents

The reaction of tetraethylorthrosilcate (TEOS) with y-aminopropyltriethoxysilane (APTS) has produced stable solid amine sorbents for the capture of carbon dioxide. The resulting amine-enriched silicon sorbent (SBA-15) has been proven to be competitive with existing environmental CO2 controlled life sorbents based on the immobilised amine technology. XPS analysis has indicated that the amine groups (N1s Peak) were incorporated onto the surfaces of this amine-based sorbent in the range of 7%. The performance of the SBA-15 was comparable to the commercially available immobilised amine sorbent (IAS).

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.

Dry beneficiation of Slovakian coal

Abstract The dry beneficiation of three types of Slovakian brown coal, namely Cigel, Handlova, and Novaky coal was conducted via triboelectrostatic separation. Three different types of separators—parallel plate, cylindrical and louvered plate—were used for this study. It was found that a parallel plate separator could reduce the ash contents of Cigel and Handlova coals. The poor quality of separation for the Novaky coal studied is probably due to the particle–particle interactions and surface oxidation states of the coal.

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.

Temperature-programmed desorption study on manganese-iron catalysts

Abstract A systematic temperature-programmed desorption (TPD) study of Mn-Fe catalysts was conducted. Hydrogen chemisorption on Mn-Fe catalysts is a highly activated process. Fe, MnO and MnFe 2 O 4 related desorption spectra have been assigned. Hydrogen does adsorb on the spinel phase (MnFe 2 O 4 ) in the form of activated adsorption. Carbon monoxide does not adsorb on the spinel phase. The results suggest that the spinel phase alone may not be an active phase for syngas conversion.

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.