Catalyst continued pretreatment

The MDA experiments were performed in a continuous down-flow fixed bed reactor at 700°C, atmospheric pressure, and a space velocity of 1500 em3/(gcat h). Catalysts were pretreated in He flow at 700°C for 30 min before feeding a CH4 N2 mixture in a 9 1 voEvol ratio (N2 used as internal standard). Unreacted methane, the reference N2, and the reaction products were analyzed on line in a gas chromatograph (HP-GC6890) as detailed in [6]. Product selectivities are given on a carbon basis. The use of N2 as internal standard allows to obtain the amount of carbonaceous residues as the amount of carbon required to close the mass carbon balances to 100%. 

Methane conversion was performed in a conventional fixed-bed continuous flow reactor operated under atmospheric pressure. The reactor consisted of a quartz, U type tube of 9 mm internal diameter. The amount of catalyst used for a test run was about 0.25 g, which was held in place by quartz wool plugs. The reactor was placed in an electric furnace with approximately 20 cm of the quartz-filled tube serving as a preheater. Before the reaction the catalysts were pretreated in an oxygen flow at 1048 K for 1 h. The reactant mixture of CH4 and 5% O2 in He was adjusted to meet several CH4/O2 ratios and a total flow rate of about 1.2 dm /h, keeping constant the oxygen... 

The patentees condua severi experiments to test the feasibility of the process. A continuous process is described in which the catalyst with approximately 40 wt% is placed in a 1" X 12 cylindrical cell and the fatty acid is extracted with supercritical CO2. The extractor is brought to a temperature of 50 to 65 °C, and pressurized to between 2,000 and 4,000 psi. The caiix>n dioxide is allowed to flow through the system at a rate of 8 standard cubic feet per hour until about 60 liters of carbon dioxide passes through the system. At a temperature of 50 °C and a pressure of 2,500 psi, approximately 65 % of the fatty acid was removed from the catalyst. When the temperature was increased to 65 °C at a pressure of 2,500 psi, about 90% of the acid was removed. The use of pressures greater than 2,500 psi did not cause a significant increase in the total percent acid recovered. A separate experiment was conducted in which the catalyst was pretreated with sulfuric acid and subsequently treated with carbon dioxide at 2,500 psi and 65 °C. With this method, about 95 to 97% of the acid could be removed. 

The catalyst was pretreated at atmospheric pressure with synthesis gas (2H2 ICO) at a rate of 500 liters gas per liter of catalyst and a temperature of 225°C. After 48 hours it was necessary to extract paraffin collected in the catalyst. Pretreatment was continued, under the same conditions for another 24 hours. After a second extraction, the catalyst was ready for use in normal-pressure and medium-pressure synthesis. 

N20-decomposition was employed as a model reaction to test the derived Fe-zeolite catalysts. Activity tests were carried out in a parallel-flow reactor system, which typically consumes 50 mg of catalyst particles (125-250 pm). The catalysts were tested in pure N20/He conditions (4.5 mbar N2O) at a total pressure of 3 bar-a. The space time, W/F°(N20), was 900 kgxsxmoT (W is the catalyst mass and F°(N20) the molar flow of N2O at the reactor inlet). The products were analyzed by gas chromatography (Chrompack CP 9001) and continuously analyzed with a chemiluminescence NOx analyzer (Ecophysics CLD 700 EL). The catalysts were pretreated in He at 673 K for 1 h, and cooled down in the same gas to the starting reaction temperature. Typically, one hour ensures steady state operation for this reaction at the conditions described above. 

Reactions were carried out with a continuous flow-reactor operating at atmospheric pressure. Before the reaction the catalyst was pretreated in a stream of air at 550" for 1,5h. 

Hall and Hassell (50) continued these studies with the intention of proving that possible traces of oxide dissolved in the metal play no significant role in the poisoning or promoting effects arising from hydrogen which had been presorbed during the pretreatment procedure. The catalysts were prepared in essentially the same manner as before. The kinetics... 

In Section 4.1.3. it was stated that the stability of CoTAA catalyst increases continuously on thermal pretreatment of mixtures with activated carbon (BRX) at temperatures of up to 900 °C, whereas the activity peaks below this level. 

The catalyst pretreatment process for both the clay-supported and the reference catalysts consists of loading into the HDS reactor under N2, purging in N2 at 20°C for 30 min at 1000 cmVmin., drying in N2 at 150°C for 60 min and at 400°C for 60 min, and finally sulfiding in a 5% H2S/H2 mixture at 400°C for two hr prior to use as catalysts. The laboratory scale liquid-phase continuous-flow HDS reactor consists of a thick-walled 0.375" ID 316 SS tube, with 1 g catalyst diluted with 5 g tabular alumina (LaRoche T-1061, 10 m2/g) sitting between plugs of quartz wool. Beneath the lower plug is a 0.125" ID, 0.375" OD deadman used to minimize volume between the reactor and the liquid receiver. The liquid test feed consisted of 0.75 wt % sulfur as dibenzothiophene (DBT), dissolved in hexadecane and is representative of a middle distillate oil. All liquid-filled lines were heated to 50°C. The reaction was carried out at 400°C LHSV = 10-40/hr. 

Conversion in the liquid phase has the disadvantage that the carbon tetrachloride formed during the disproportionation of trichlorofluoromethane forms a complex compound with the aluminum trichloride possessing no catalytic effect, so that only a relatively small amount of trichlorofluoromethane can be converted with a predetermined amount of aluminum trichloride. The continuous gas-phase method in a tubular reactor is more practicable the temperature at which it takes place must be high enough to prevent any products from condensing on the catalyst. It is also possible to perform the disproportionation process continuously in the liquid phase in a tubular reactor, under pressure and at an increased temperature. In this case aluminum trichloride must first be activated by pretreatment (partial fluorination), since the partial fluorination of aluminum trichloride greatly reduces the tendency for complex compounds to form with the chlorinated hydrocarbon when this itself has formed. 

The ultrafine iron oxide catalyst run was conducted in a 300 mL autoclave operated as a continuous stirred tank reactor (CSTR) using a configuration similar to that reported previously.12 The catalyst (10 g) was slurried with a C30 oil (ethyl), pretreated with CO (Liquid Carbonic,... 

Pretreatments such as filtration can have a direct impact on the quality of the final ester product, as well as on yields. Table 6.4 shows the effect on product quality of the ester from acid oil, which had been filtered to remove solids and other components. The filtered acid oil was pre-esterified under reflux with methanol (12 1 ratio MeOH to FFA) in the presence of 0.56wt% of 98% sulfuric acid as catalyst, based on the acid oil charge. The reaction was continued until the acid value was less than 5 mg KOH/g, followed by neutral-... 

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