MICROMERITICS equations

The surface area was calculated using the BET equation,36 while the total pore volume and the average pore size were calculated from the nitrogen desorption branch applying the Barrett-Joyner-Halenda (BJH) method.37 BET and BJH adsorption measurements were carried out with a Micromeritics Tri-Star system on both the supports and the calcined catalysts. Prior to measurements, the samples were evacuated at 433 K to approximately 50 mTorr for 4 h. 

Nitrogen adsorption and desorption isotherms were performed at 77 K on a Micromeritics ASAP 2400 volumetric adsorption system. The pore size distribution and surface area were deduced from the adsorption isotherms using the BJH method and the BET equation. 

EXAMPLE 2.2 Use of the Sedimentation Equation for Particle Size Determination. A titanium dioxide pigment of density 4.12 g cm 3 is suspended in water at 33°C. At this temperature, the density and viscosity of water are 0.9947 g cm-3 and 7.523 10-3 P, respectively. A particle size analyzer (SediGraph, Micromeritics Instruments Corp., Norcross, GA 30093) plots the following data for cumulative weight percent versus equivalent spherical radius ... 

Specific surface areas and micropore volumes were obtained from nitrogen adsorption - desorption isotherms at -196°C using Micromeritics ASAP 2010. Prior to the measurements all powdered samples were degassed at 175 °C under vacuum 10 6 Torr for 6 hours. The total surface area was calculated using BET equation. The method of Horvath and Kawazoe was used to determine the pore size diameters of the product. 

The poly-[HIPE] sample intrusion mercury porosimetry study reported in Figure 4.67 was carried out in a Micromeritics, Atlanta, GA, USA, AutoPore IV-9500 automatic mercury porosimeter.1 The sample holder chamber was evacuated up to 5 x 10-5 Torr the contact angle and surface tension of mercury applied by the AutoPore software in the Washburn equation to obtain the pore size distribution was 130° and 485mN/m, respectively. Besides, the equilibration time was 10 s, and the mercury intrusion pressure range was from 0.0037 to 414 MPa, that is, the pores size range was from 335.7 to 0.003 pm. The poly-(HIPE) sample was prepared by polymerizing styrene (90%) and divinylbenzene (10%) [157],... 

As a matter of fact, the kind of distribution of interest to us is actually represented by a Type III Pearsonian curve (see Elderton, 1938). We have, however, chosen to omit discussion of Pearson s distribution since it is simpler to deal with the forms of equations we developed. There are few situations where rigorous adherence to distribution types is required in micromeritics. In our developments the ease of obtaining parameters has governed our selection of formulas. (See Chapter 4.)... 

The mercury porosimetry experiments were carried out using an Autopore 9220 apparatus (Micromeritics). Around 4 g of sample were placed into the penetrometer. The initial results were obtained on a low pressure port between 0.004 and 0.1 MPa. The high pressure curve was obtained up to 400 MPa before extrusion and reintrusion. A contact angle of 130° was used to interpret the results using the Washburn equation. 

The specific surface area (Sbet) was evaluated by full 3-parameters BET equation and by 2-parameters linear BET plot in the range p/p° 0.01-0.2. The total pore volume (Vt) was evaluated by Gurvitsch rule. BJH method was applied on the desorption isotherm branch only for mesoporous materials, in order to evaluate the mesopore width. Mean pore size (doFi) was calculated using DFT method (Micromeritics DFT Plus software) for all materials with the cylindrical pores in oxide surface model. 

Adsorption/desorption isotherms of nitrogen at 77 K were measured with an automated apparatus ASAP 2010 (Micromeritics, USA). The specific surface areas, Sbet, were calculated from the linear form of the BET equation, taking the cross-sectional area of the nitrogen molecule to be 16.210 m. Pore size distributions were calculated in the standard maimer by using BJH method [6]. The total pore volumes, Vp, for the samples under study were determined from a single point adsorption at a relative pressure of 0.98 by converting the value of the adsorbed gas to the volume of the liquid adsorbate. 

The BET surface areas of the zeolite samples were determined by N2 adsorption-desorption at -196 C in a Micromeritics ASAP 2010 equipment. Prior to the determination of the adsorption isotherm, the calcined sample (0.5 g) was outgassed at 400 C under a residual pressure of 1 Pa in order to remove moisture. The adsorption data were treated with the full BET equation. The t-plot method using the universal t-curve was applied in order to obtain an estimation of the micropore volume, microporous surface and external surface area [7]. 

Specific surface area was calculated from the Brunauer-Emmett-Teller (BET) equation for N2 adsorption at 77 K (Micromeritics, ASAP 2010) [10], The t-method of de Boer was used to determine the micropore volume [11]. The pore size distribution curves of micropores were obtained by the Horvath-Kawazoe (H-K) method [12]. 

Nitrogen isotherms were measured by using an ASAP (Micromeritics) at 77K. Prior to each analysis, the samples were outgassed at S73K for 10 - 12 h to obtain a residual pressure of less than 10 torr. The amount on nitrogen adsorbed was used to calculate specific surface area, and the micro pore volumes determined from the BET equation [14] and t-plot method [15], respectively. Also, the Horvath-Kawazoe model [16] was applied to the experimental nitrogen isotherms for pore size distribution. 

Bulk Si/Al ratios were determined by AAS. Surface areas and pore volumes were determined by N2 absorption isotherms measured at liquid nitrogen temperature using a Micromeritics ASAP 2000M (Table 1). The zeolites were degassed under vacuum at 150°C for the as-s)mthesised and 450°C for the modified zeolites for at least 3 hours. The total surface area was derived using the BET equation [12], the micropore volume and the external surface area (ESA) were estimated by means of the t-plot method of Lippens et al [13] and the total and mesopore volumes were calculated by Barrett-Joyner-Halenda anaylsis of the desorption branch of the N2 isotherm [14]. 

X-ray powder diffraction (XRD) patterns were taken on a Spectrolab CPS Series 3000 120 diffractometer, using Ni filtered Cu Ka radiation. The nitrogen adsorption isotherms were determined at 77 K by means of a Micromeritics Gemini 2370 surface area analyser. Surface areas were derived from the BET equation in the relative pressure range 0.05-0.25, assuming a cross-sectional area of 0.162 nm" for the nitrogen molecule [ 18]. 

Specific surface area (SSA) by gas adsorption Specific surface areas (expressed in m /g) were measured by Krypton adsorption at 77K (Micromeritics ASAP2400) and calculated using BET equation [3] Prior to measurements, powder specimens were outgassed under vacuum (5 millitorrs) at room temperature. Krypton was chosen as adsorbate because of the low SSA of some samples (SSAphysisorption method allows for measuring the overall surface developed by the powder particles including interparticular porosity (except sealed pores). 

Surface areas (SBET) were measured with a Micromeritics Flowsorb II using the single point approximation of the BET equation for the adsorption of N2 at 77 K. Carbon deposits on the catalyst were quantified by elemental analysis involving combustion to CO2, absorption in a Ba(C104)2 solution and coulometric titration. 

Textural properties of fresh and deactivated samples were determined using an ASAP 2000 analyzer (Micromeritics). To determine total surface area, the BET equation was applied to adsorption uptakes obtained in the relative pressure interval, P/Po, of 0.01 to 0.05. Zeolite and matrix surface areas were determined according to the ASTM D-4365 method, using P/Po pressures of 0.01 to 0.60. Mesopore volume and pore-size distribution were determined according to the ASTM D-4222 method at P/Po relative pressures of 0.01 to 0.99. 

Specific surface area and pore volume distribution were measured by nitrogen adsorption in an Accusorb 2100E Micromeritics adsorption analyzer. The data were interpreted using the BET equation, assuming a cross-sectional area of 16.2 for Nj. 

The nitrogen adsorption-desorption isotherms of the calcined samples were determined at -196°C on a Micromeritics ASAP 2010 apparatus. Prior to the measurements, the samples were outgassed at 90°C during 1 hours and then at 350°C for 16 hours. The BET equivalent surface area was calculated using the BET equation [22]. 

The catalysts were characterized by using various techniques. X-ray diffraction (XRD) patterns were recorded on a Siemens D 500 diffractometer using CuKa radiation. The specific surface areas of the solids were determined by using the BET method on a Micromeritics ASAP 2000 analyser. Acid and basic sites were quantified from the retention isotherms for two different titrants (cyclohexylamine and phenol, of p/Ta 10.6 and 9.9, and L ,ax 226 and 271.6 nm, respectively) dissolved in cyclohexane. By using the Langmuir equation, the amount of titrant adsorbed in monolayer form, Xm, was obtained as a measure of the concentration of acid and basic sites [11]. Also, acid properties were assessed by temperature-programmed desorption of two probe molecules, that is, pyridine (pKa= 5.25) and cyclohexylamine. The composition of the catalysts was determined by energy dispersive X-ray analysis (EDAX) on a Jeol JSM-5400 instrument equipped with a Link ISI analyser and a Pentafet detector (Oxford). 

Mercury Intrusion Analysis. Mercury intrusion measurements were carried out with a porosimeter (Micromeritics 9220) capable of intruding mercury with intrusion pressures (p) up to 414 MPa (60,000 psi). Pore size distributions were calculated from the intrusion curve by using the Washburn (7) equation ... 

Nitrogen physisorption measurements were performed on a Micromeritics Tristar 3000 apparatus at -196 °C. Prior to analysis the samples were dried in a helium flow for 14 horns at 120 °C. Surface areas (St), and micropore (Vmicro) and mesopore (Vmeso) volumes were determined using the t-method [13] with the Harkins-Jura thickness equation. There is no standard method for the determination of blocked mesopore volume (Vmeso,bi)- For this we used the pore size distribution from the desorption branch of the isotherm calculated using BJH theory [14]. The total amoimt of Vmeso,bi was determined considering that the volume in pores with a diameter of 2 - 5 run is (partially) blocked. 

Az physisorption measurements. The catalyst and support surface areas were measured by physisorption of Nz at -196°C on a Micromeritics ASAP 2000 instrument. Prior to measurement, samples were outgassed overnight at 150°C under 0.13 Pa. Surface area values were computed using the BET equation from the amount of Nz physisorbed at different relative pressures. 

Specific surface area of the Mn oxide powder was measured using a liquid nitrogen adsorption (BET) method using Micromeritics FlowSorb II 2300 surface area analyzer. The point of zero charge zc) of the Mn oxide was determined using the method described by Sigg and Stumm (13), which is based on the following equation ... 

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