Pore volume measurement

A new, simple, and practical method for pore volume measurement was proposed... 

Figure 18. Procedure for EPV (effective pore volume) measurement (a) a 50 g MnO, sample is placed in a 100 mL graduated cylinder (2) water is added gradually in 0.5 mL portions (3) with a stopper in place, the cylinder is turned upside down 10 times while being shaken (4) the cylinder is droppes 4 cm onto a wooden surface (5) the Mn02 sample volume is read after 5 and 10 taps (i.e., drops).

The location or distribution of the Mo sulfide species, that is, inside or outside the zeolite cavities, was examined by HREM, XRD [17], and pore volume measurements by using benzene as adsorbate [18]. HREM observations for MoSx/NaY possessing 2Mo/SC obviously demonstrated that no Mo sulfide spiecies were formed on the outside of the zeolite and that the framework structure of the zeolite was not destroyed at all on the accommodation of Mo sulfide species. The XRD and pore volume measurements confirmed the HREM observations. It is concluded that highly dispiersed intrazeolite Mo sulfide species are produced by using Mo(CO),. 

Unlike chemisorption, physical adsorption may lead to surface coverage by more than one layer of adsorbate. Thus, pores can be filled by the adsorbate for pore volume measurements. 

Catalyst analysis by XRD, [6] area and pore volume measurements and C and S elemental analysis was performed on the samples before and after use in the laboratory micro reactors. 

When dealing with particles having porous crusts of finite thickness, it appears that calculation is the only means that can be resorted to, and the required information may be obtained from surface area and pore volume measurements by gas adsorption and by microscopic examination. 

The difference in the pore volumes measured for the two membranes, 0.17 mlg (A20) and 0.39 mlg (A200), may be ascribed to the different anodic oxidation conditions employed in the preparations. This can influence the pore density in the membranes as earlier discussed [2-4]. 

Throughout this work was aasumed that the coke is uniformly distributed over the catalyst particles on a macroscopic scale. This implies that we assumed no significant coke gradients over the particles to be present and, moreover, that pore mouth plugging by coke had occurred. With the email particles (30—30 mesh) used in this work both assumptions seem Justified. The absence of pore mouth plugging has been substantiated by pore volume measurements of the fresh and spent catalysts, which led to derived densities for the coke deposits in the range 1.2-1.5 g/mlh... 

Figure 27.7 Relation between sorption capacity of difierent carbon sorbents for the A-grade heavy oil and pore volume measured by using a new dilatometer for mercury porosimetry.

Hg specific pore volume measured by mercury porosimetry Kc m<75 m diameter between 2 and 7.5 nm determined by Broekhoff-de-Boer theory V volume obtained by addition of tag, Tc m<7 5mii and Sbet specific surface si02 silica particle diameter measured by TEM. 

The syntheses of the ZSM-5 zeolites were based on two different patents (refs. 2-3). In two of the synthesis mixtures sodium ions were, however, largely replaced by potassium ions (table 1). Protonation was achieved by ion-exchange with an aqueous 1 M solution of ammonium-nitrate followed by calcination for 8 hours at 500 °C. In addition, one H-ZSM-5 catalyst was kindly supplied from MOBIL. The zeolites were characterized by x-ray diffraction, scanning electron microscopy, pore-volume measurements (BET) and elemental analysis (ICP). Catalytic experiments were performed at atmospheric pressure by feeding methanol diluted with nitrogen (1 5) into a continuous flow quartz microreactor containing 25-300 mg H-ZSM-5. The reaction temperature was varied from 245 to 400 °C and the products were analyzed by gas-chromatography. 

UV spectra used for a semi-quantitive determination of the amount of intracrystalline phthalocyanine complexes were taken on a Perkin Elmer UV-visible spectrophotometer. A calibration curve was obtained by dissolving known amounts of metal complex in concentrated sulfuric acid. Zeolite was added to take into account matrix effects. Surface area and pore volume measurements were performed on a Micromeritics ASAP 2000 by absorption of nitrogen gas at liquid nitrogen temperature. X-ray powder diffraction of the zeolites was used to ensure good crystallinity after the exchange and encapsulation procedures... 

Table I compares the pore properties for the starting metakaolln and the LSX pellets, and Figure 6 plots differential pore volume distributions for both materials. The pore distribution data show that the macroporosity of the LSX pellets 1s approximately half that of the starting metakaolln. The difference between pore volumes measured with helium and mercury 1s used as an Indicator for the microporosity of the sample.

Pore Volume Measurement The pore volume was measured from the differences of mercury and helium displacement values. 

When the pore size of silicas is very small (as in C60), the compression of the structure caused by the mercury intrusion decreases the pore size to such an extent that it is outside the range for mercury intrusion analysis. The pore volumes measured represent only the compression region of the curve, and as a consequence the total pore volumes measured are lower than those measured for nitrogen. Nitrogen sorption methods are the only appropriate technique for this type of material. 

The curve fitting procedure used (7, has one other adjustable parameter, pulse input, or number of pore volumes for which the contaminant was fed. As column pore volume was known from independently measurements, pulse input was fixed rather than fit. That is, particle and bulk density of the packing were known from prior measurements, pore volume was determined for each column by weighing dry versus wet, and flow velocity was measured for each experiment. Further, fitted conservative-tracer breakthrough curves gave R = I, suggesting that pulse input and pore volume measurements were consistent. 

Thermoporimetry [10,11] can reliably be used to obtain the pore-size distribution of porous particles suspended in water. The basis of the technique is that the surface area of the ice-liquid water interface increases when the ice penetrates narrow pores. As the diameter of a pore is smaller, the increase in interfacial area is larger. To freeze the water in narrower pores thus requires lower temperatures. The temperature at which the heat of solidification of water is set free thus indicates the width of the pores, and the amount of heat released indicates the pore volume. Measurement by DSC (differential scanning calorimetry) can provide the data for determination of the pore-size distribution of porous particles suspended in pure water. It has been observed that the first layer of water molecules present on the surface of oxides cannot be frozen apparently the interaction with the surface of the oxides is so high that the layer is already frozen without attaining the structure of ice. Thermoporimetry can, therefore, also provide data about the interaction of water with the surfaces of solids. Thermoporimetry with other liquids, e. g. benzene, can provide information about the interaction of surfaces with, e. g., apolar liquids. 

The pore volume measurements have also been used to demonstrate the state and location of the nickel in SAPO-5. The adsorption capacity of the modified materials decreases to 67-87% of that of pure SAPO (Table 2), which probabiy confirms the presence of considerabie amounts of extra-lattice nickel in aii the sampies. This effect may be due to the occiusion of highiy dispersed nickel species in the channeis and/or to the... 

Adsorption measurements allow the determination of coke location. When the volume occupied by coke is much smaller than the volume inaccessible to adsorbates, it means that there is a pore blockage. However, in many cases the adsorption study is carried out at a different temperature than the reaction, and therefore diffusivity could be quite different. Another aspect that should be taken into account is that if the pretreatment for adsorption measurement requires temperatures higher than the reaction temperature, an important fraction of carbonaceous deposits could be stripped off the catalyst and, therefore, the pore volume measured in this way will be higher than the actual volume under reaction conditions. A modification in the coke structure might also occur under these circumstances ... 

Taking as a reference the textural characteristics of the heat treated sepiolite support "ST", the data in Table 1 indicated that washing this natural silicate with an acid solution produced an appreciable increase in tlie BET surface area but had little effect on the surface area and pore volume measured by merciuy porosimetry. Thus, this increase must have been in pores of between 1 and 3nm radius, since evaluation of the adsorption isotlierm by use of the t-plot... 

Figure 46.6 depicts the internal cumulative pore volume as a function of pore diameter for Sorbsil C500. The total pore volumes as measured by the two techniques agree to within 0.05 cm /g the pore volume measured by mercury porosimetry is slightly higher, possibly because this is an extremely wide-pored silica, with some pores too wide to be measured by nitrogen sorption. 

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