Activity testing

Activity measurements have been important ever since industrial catalysts were first introduced. BASF carried out some 20,000 tests during the production of a successful ammorua synthesis catalyst. Until the 1960s, however, when many new catalytic processes were developed, laboratory activity tests were fairly erode. It was only possible to screen different samples and obtain relative activities before new catalysts reached the semitechnical plant stage and commercial trials were considered possible. More recently, new testing equipment has been able to simulate plant conditions and provide accurate kinetic information for reliable design calculations. 

Chemical analysis X-ray fluorescence (XRF) Samples emit secondary X-rays following bombardment with hard X-rays which allow complete elemental analysis. 

Particle size Simple measurement of solid particles or size grading of powders. 

Crushing strength Determined by compressing catalyst particles between anvils or by bulk crushing the catalyst in a standard container. 

Bulk density Packing weight per unit volume of loose or dense packed catalyst particles. 

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Appearance of the active test pieces in a 6-month experiment according... 

As mentioned in Section 2.2 (Fixed-Bed Reactors) and in the Micro activity test example, even fluid-bed catalysts are tested in fixed-bed reactors when working on a small scale. The reason is that the experimental conditions in laboratory fluidized-bed reactors can not even approach that in production units. Even catalyst particle size must be much smaller to get proper fluidization. The reactors of ARCO (Wachtel, et al, 1972) and that of Kraemer and deLasa (1988) are such attempts. 

If the pH level of drilling fluid drops and the hydrogen sulfide test result is negative, there is a good possibility that carbon dioxide will be present. Positive results of microbial activity tests (described later) also indicate the possibility of carbon dioxide presence. Carbon dioxide meters are also available commercially and can be used. 

The first step in E-cat testing is to bum the carbon off the sample. The sample is then placed in a MAT unit (Figure 3-13), the heart of which is a fixed bed reactor. A certain amount of a standard gas oil feedstock is injected into the hot bed of catalyst. The activity i.s reported as the conversion to 430°F (221°C) material. The feedstock s quality, reactor temperature, catalyst-to-oil ratio, and space velocity are four variables affecting MAT results. Each catalyst vendor uses slightly different operating variables to conduct micro activity testing, as indicated in Table 3-2. 

Unknown structure activity relationships, mainly because methods for activity testing were poorly available. 

Biological activity tests on organotin(lV) complexes with a potent antihypertensive agent, captopril[(2S)-l-[(2S)-2-methyl-3-sulfanyl propanoyl]pyrroli-dine-2-carboxylic acid cap], were carried toward the embryos of C. intestinalis. The main results obtained were as follows ... 

The detection of reactions mediated by specific IgE to agents triggering anaphylaxis may be achieved by means of serological methods serum-specific IgE, or by means of cellular tests which determine the release of basophil mediators (leukotrienes and histamine) or by means of the analysis of basophil expression markers, a technique known as the basophil activation test (BAT). 

Sanz ML, Gamboa PM, Antepara I, Uasuf C, Vila L, Garda-Aviles C, Chazot M, De Week L Flow cytometric basophil activation test by detection of CD63 expression in patients with immediate-type reactions to (J-lactam antibiotics. Clin Exp Allergy 2002 32 277-286. 

Garda BE, Barber D, Salcedo G, Rihs HP, Raulf-Heimsoth M Basophil activation test and specific IgE measurements using a panel of recombinant natural rubber latex allergen to determine the latex allergen sensitization profile in children. Pediatr 52 Allergy Immunol 2006 17 148-156. 

No increase of plasma leukotrienes after RCM administration Mast cell mediator release correlates with severity of reaction, positive basophil activation test to RCM in patients... 

Positive lymphocyte transformation test and lymphocyte activation tests... 

Positive basophil activation tests were reported in patients with immediate RCM hypersensitivity reactions, which may be regarded as another indirect indication for an IgE-mediated allergy [35]. 

Unfortunately there is no commercial assay for routine measurement of serum levels of RCM-specific IgE antibodies. The reliability of other in vitro tests, such as the basophil activation test, has not yet been established. Results from individual patients indicate that the basophil activation test may be helpful [36]. However, at the moment it is only added on an experimental scientific basis. Provocation is not generally recommended, as intravenous applications of as low as 0.5-1 ml RCM have led to severe anaphylaxis [41]. 

RCM-related T-cell activity may be assessed in vitro by lymphocyte transformation test [19, 24]. In addition, CD69 upregulation (lymphocyte activation test) was observed in patients with a positive lymphocyte transformation test [24, 39]. These tests appear to be a promising tool to identify drug-reactive T cells in the peripheral blood of patients with RCM-induced drug-hypersensitivity reactions. However, the sensitivity and specificity remain unknown and, therefore, these tests cannot be recommended for routine use yet, but further research on the specificity and sensitivity is indicated. 

Kanny G, Pichler W, Morisset M, et al T-cell-mediated reactions to iodinated contrast media evaluation by skin and lymphocyte activation tests. J Allergy Clin Immunol 2005 115 179-185. 

From the results of the urease activity test summarized in Figure 15, it is clear that the deposition procedure preserved to a certain extent the enzyme catalytic activity. Heating the sample before testing decreased the enzyme in the film by about 30% but did not eliminate it completely. The results of the activity test of two samples are summarized in Table 1 together with reference values for a spontaneous reaction without enzyme. It is necessary to underline that enzymatic activity on spherical supports was higher than the respective value in flat films, which could indicate that apparent catalytic efficiency was improved due to an increased area-to-volume ratio. 

The catalyst (0.15 g) was loaded into a quartz tube reactor (internal diameter = 4 mm). The catalyst was pretreated in nitrogen at 400°C. Simulated gasoline reformate was used for the activity test of the catalyst. The composition of the simulated reformate was 36 wt% H2, 17 wt% CO2, 28 wt% N2, 17 wt% H2O, 1 wt% CO, and air was added additionally as the oxidant. The total flow rate was maintained at 100 ml/min. The test was performed over the temperature range of 120 280°C at various flow rates of inlet air. 

Presulfiding for the activity tests was accomplished by first heating the catalyst in nitrogen at 204°C. 10% H2S/H2 was intro-... 

Activity Tests. Figure 2 shows results of activity tests for a commercial American Cyanamid HDS-2 catalyst which had been in use for about six years. The catalyst was sampled at various depths and results for three samples containing 0.01% As, 0.6% As, and 3.6% As show a decrease in activity with Increasing arsenic content. 

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