Examination under reactor conditions

In most microscopy studies the catalyst is examined under vacuum. To understand the system, the catalyst should be examined under reactor conditions. Environmental chambers that do not reduce instrument resolution are presently not available. Similarly, pretreatment systems attached to the instrument would extend characterization insight. At the very least, sample delivery systems that minimize air exposure are necessary. For example, air exposure during sample transfer as might occur with a reduced Pd catalyst can alter the crystallite morphology. Such studies would be expected to enhance catalyst development. 

CO oxidation measurements were carried out in the SFR at varying CO/ O2 ratios. Ar-diluted gas mixtures were fed to the reactor with a flow rate of 15.5 SLPM (standard liter per minute at 293 K, 1 atm.). The calculated flow velocity and working pressure were 51 cm/s and 500 mbar, respectively. The reactor inlet temperature was 313 K. The reaction was studied at steady-state conditions (Table 2.2). At low temperatures, oxygen-rich conditions were selected to avoid external mass transport hmitations and examine the kinetic effects (Case 1). However, for moderate- and high-temperature regimes (Case 2 and Case 3), the reactions were examined under stoichiometric conditions. 

Operation of a reactor in steady state or under transient conditions is governed by the mode of heat transfer, which varies with the coolant type and behavior within fuel assembHes (30). QuaHtative understanding of the different regimes using water cooling can be gained by examining heat flux, q, as a function of the difference in temperature between a heated surface and the saturation temperature of water (Eig. 1). 

Babcock et al. (Bl) examined the hydrogenation of a-methylstyrene catalyzed by palladium and platinum catalysts in a reactor of 1 -in. diameter under countercurrent flow. Flow rates were above 1500 kg/m2-hr for the liquid phase and above 15 kg/m2-hr for the gas, and it was concluded from the experimental results that mass transfer was not of rate-determining influence under these conditions. 

The effects of feedstock cellulose content on cellulase enzyme activities in the digester system were examined in multiple laboratory-scale CSTR digesters operated under similar conditions with identical levels of feedstock organic loading (g VS/reactor d) but different levels of cellulose (Solka Floe). In general, all celli se enzyme... 

A route of chemical recycling by pyrolysis has been examined (71). The pyrolysis of COC was performed in a fluidized-bed reactor. Various parameters, such as pyrolysis temperature, fluidizing gas or residence time were varied. Under favorite conditions, the undesired tar fraction could be reduced to a minimum of around 10%. Up to 44% of valuable gases and 45% of aromatic light oils could be obtained at a pyrolysis temperature of 700°C. In general, nor-bornene was recovered only in traces. Thus, it is concluded that 2-norbomene is not sufficiently stable to resist the conditions of pyrolysis. Actually, a retro-Alder reaction occurs resulting in ethene and cyclopentadiene. 

Finally, we have not discussed cases where Raman spectroscopy can be used to study catalysts indirectly, as for example, by extracting a sample from a reactor and preparing a KBr disc for IR or Raman investigation. Such techniques may be useful in special circumstances (50) but have limited applicability with regard to the direct examination of surfaces under reaction conditions. 

Experimental. To further understand the process of droplet combustion and particulate formation, a more fundamental study of the effects of droplet size, local stoichiometry and gas-droplet relative velocity has been carried out. This work made use of a controlled flow variable slip reactor in which the combustion of droplet streams can be examined under well defined conditions. 

A continuous-flow, fixed-bed reactor was utilized for the catalytic cracking of the heavy oil. Reactions were conducted under temperature conditions ranging from 300 to 600°C, at a catalyst weight W of about 1.0 x 10 kg and a feed oil mass flow rate F of about 1.0 X 10 kg h In order to examine the catalysis of Ni in Ni-REY for hydrogenation, experiments using hydrogen as the carrier gas were also conducted. 

The excessive formation of powders occurs only under limited conditions, although powder formation has been observed in reactors of different designs and types of discharge and with various monomers, particularly in a specific section of a reactor that is related to the flow pattern of gas. Therefore, powder formation provides an excellent opportunity for examining the basic principles of the polymer deposition mechanism. 

The early workers (1,3) claimed the rates they measured were kinetically controlled, but the evidence in support of their claims was critically examined by later workers (6,T) and found wanting. Albright and Hanson (7 ) went so far as to conclude in 1969 that toluene nitration in the two phase is mass transfer controlled under all conditions so far investigated. Recent results (8,9) with a batch reactor must cast doubts upon this conclusion. This paper therefore seeks to clarify the conditions under which kinetic and mass transfer control occur in the nitration of toluene in CFSTRs and to provide an explanation for the rate correlations shown in Figures 1 and 2. 

PCE was oxidized in a fixed-bed continuous flow reactor. The reactor was a 6-mm-o.d. Pyrex glass tube operated in the down flow mode. A reactant mainly containing air with 30 10,000 ppm of PCE was fed into the reactor charging 60/80 mesh size catalyst at a flow rate of 600 ml/min to avoid mass transfer resistance. The reaction temperatures were maintained at 350 °C under atmospheric pressure as a typical reactor condition [9]. The feed and product streams of the reactor were analyzed by on-line H.P. 5890A gas chromatography (GC) with TCD and FID detectors. The steady-state conversion of PCE was calculated based upon the difference between inlet and outlet concentrations of PCE. It has also been examined that more than 90% of PCE is converted to CO and CO2 by carbon balance. More detailed experimental procedures are described elsewhere [2]. 

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