IJCPE Vol.11 No.2 (June 2010) Iraqi Journal of Chemical and Petroleum Engineering Vol.11 No.2 (June2010) 43-48 ISSN: 1997- 4884 Effect of the Forming Conditions in the Production of Gamma Alumina Catalyst Support on the Crushing Strength Property Alaa Dhari Jawad, Ibrahim Richeh, and Riad Ahmed Saleh Chemical engineering Department- College of Chemical and Petroleum Engineering- Al-Baath university- Syria Abstract An investigation was conducted for the determination of the effects of the forming conditions in the production of Gamma Alumina catalyst support on the crushing strength property. Eight variables were studied , they are ;binder content which is the sodium silicate , Solvent content which is the water, speed of mixing , time of mixing, drying temperature , drying time , calcinations temperature and the calcinations time Design of the experiments was made by using the response Surface method in Minitab 15 software which supply us 90 experiments . The results of this investigation show that the crushing strength for the dried Gamma alumina extrudate was affected by the drying temperature and the drying time only and there is no interaction effect between the variables studied. Furthermore, the results show that, the crushing strength for the calcined extrudate was affected by the speed of mixing only and the optimum speed is 900rpm. The maximum crushing strength of 38.38 after calcinations and 11.865 Kg/mm after drying were obtained Keywords: Gamma Alumina, Catalyst Support, Crushing strength. _____________________________________________________________________ Introduction The physical characteristics of the naphtha reforming catalysts are determined primarily by the material which serves as a support for the metal or bimetallic function. Alumina is the support for nearly all reforming catalysts .The strength of the macroscopic catalyst particles is an important property. For most fixed- bed operations, if a catalyst can survive the handling during manufacturing and loading, it has adequate strength [1]. The physical strength parameters of the catalysts, such as crushing strength and resistance to abrasion, are of significant importance. In industrial reactors, a catalyst with greater abrasion and crumbling tendency can cause severe pressure drop in reactors and pipe lines. Changes in the environment inside the reformer caused by physical degradation of the catalyst adversely affect the the selectivity, activity, and ultimately the life of the catalyst [1]. The crush strength is the resistance of a solid to compression, a property of paramount importance not only for industrial catalysts, but also for ceramics, pharmaceutical tablets and many other solid materials. In The case of catalysts, it is noteworthy that many plant shutdowns occur due to mechanical failure of the catalyst (and not due to its loss of activity) [2]. As far as catalysts are concerned, the ASTM standard methods D 4179 and D6175 are recommended. D 4179 refer to tableted pellets which can be measured in either axial or radial way. As the axial crush strength is much higher, it is not representative of the catalyst behavior in the reactors, therefore the radial crush strength must be measured for industrial purposes (the type of the crush strength measured must always be specified).D 6175-98 procedure refers to extrudates (the radial measurements can be only performed in this case).The radial crush strength is usually expressed in Kg/mm [2]. The crush strength of a catalyst is not appreciably dependent on reactor loading , but mainly on reactor operation .When the catalyst does not require activation , the crush test should be conducted on fresh dried samples, when the catalyst has to be activated in the reactor , only measurements on activated samples are significant [2]. University of Baghdad College of Engineering Iraqi Journal of Chemical and Petroleum Engineering Effect of the Forming Conditions in the Production of Gamma Alumina Catalyst Support on the Crushing Strength Property IJCPE Vol.11 No.2 (June 2010) 44 Single pellet radial or, for irregularly shaped particles, bulk crush strength must be measured for any catalyst used in fixed –bed and trickle-bed reactors. A minimum value of the force required to break the pellets is usually specified for single –pellet crush strength (such values should not refer to axial measurements) [2]. For bulk crush strength, either the minimum pressure giving 1% fines (ASTM D 7804-04) or the maximum percentage of fines formed under the pressure of 23 bar are specified [2]. The crushing strength of the Alumina spheres measured by single –pellet radial is 7 Kg minimum. Without knowledge of the mechanical properties of the materials used, it is impossible to utilize high pressure, temperatures and rates which characterize the present day development of all industries [3]. Contact masses experience different loads when operating under the conditions of fixed and supensed beds. Under the conditions of a fixed bed, the grains are under the pressure of the overlying beds, i.e., they" work” for compression under the conditions of different temperatures and media .Under the conditions of suspension , friction forces and to a certain extent impact Forces act on the catalyst .Taking account of the difference in the load, contact masses are tested likewise by different methods [3]. The purpose of this research is to show which of the variables participating in the forming of gamma alumina support has an effect on the mechanical characteristic of the support by measuring the radial crush strength of the extrudate. Experimental work The variables that were studied in this work and which is participating in the steps of forming the gamma alumina supports from the gamma alumina powder are as shown in table 1 with the upper and the lower limit for each of them (based on gamma alumina powder) . Table 1 Details of the variables and its lower and upper limits No. Variable Lowe r limit upper limit 1 Binder: Sodium silicate (50% soln.) % 20% 50% 2 Solvent: Water % 70% 90% 3 Speed of mixing ,rpm 300 1500 4 Time of mixing,min 10 45 5 Drying temperature,C o 100 200 6 Drying time,min 30 120 7 Calcination temperature, C o 300 700 8 Calcination time,hr. 2 6 Raw Materials Gamma alumina powder supplied from Suzhou Yuguang Lighting Materials Co. Ltd. From China was used with the properties shown in table 2 .The XRD chart for it is shown in fig. 1. Table 2 Properties of the Gamma alumina powder No. Specification Value 1 Name High purity Alumina powder 2 Type Gamma-Al2O3 3 Purity% 99.99 4 Particle size,µm 0.2 5 Loose density, g/cm 3 0.16 6 BET,m 2 /g 120 7 K,ppm 30 8 Na,ppm 18 9 Fe,ppm 10 10 Si,ppm 20 11 Mg,ppm 10 12 Mn,ppm 9 13 Ti,ppm 10 14 Cr,ppm 10 15 Cr,ppm 10 16 Zn,ppm 10 Figure 1 XRD chart for the Gamma alumina powder used Commercial Sodium silicate solution was used as a binder, its specific gravity is 1.500 and its concentration is 44% Alaa Dhari Jawad, Ibrahim Richeh, and Riad Ahmed Saleh IJCPE Vol.11 No.2 (June 2010) 45 Gamma Alumina Extrudate manufacturing steps Figure 2 show the steps used in making the alumina paste and forming the extrudate for the support [4]. Figure 2 Block diagram of the steps used in producing the Gamma alumina Extrudate (Support) Method of Moulding There are many methods to mould the catalyst supports [3], In this work the gamma alumina paste was rubbed into the aperture of perforated steel plate. The size of granules produced is determined by the thickness of the plate and the diameter of the aperture, this is the same as mentioned in reference [3]. Design of Experiments The response surface method from the Minitab 15 software was used to get the table of design for the 8 variables mentioned above, 90 experiments were got from the Minitab software [5,6] . From each experiment two samples was tested for crush strength , one after drying and other after calcination, so from the 90 experiments 180 samples were gotten and the crush strength was repeated 20 times for each sample, i.e. , 3600 single pellets were tested for the crushing strength according the standard method, ASTM D-6175-03 [7].Each pellet length over diameter ratio was measured before test , to assure that the L/D is equal or greater than 1.1 as mentioned in the ASTM method above. Results and Discussion From the analysis of variance for the dried and calcined crush strength made by the Minitab Software, we get that there is a linear regression for the dried crush strength,also it appeared that there is no any interaction effects between the variables affect the crush strength for both the dried and calcined extrudate. The estimated regression coefficients for the dried crush strength show that drying temperature and the drying time were the only variables that affect the crush strength in dried state. Figure 3 show the interaction effect for the two above variables on the dried crush strength. From figure 3 , it can be seen that the crush strength increased with increasing the drying time for each drying temperature .Also we can see that the best drying time is between 90-120 minutes.The best drying temperature is between 150-200 C o . 120.00090.91075.00059.09030.000 11 10 9 8 7 6 5 4 3 2 DRYING TIME M e a n 100.000 132.322 150.000 167.678 200.000 TEMP DRYING Interaction Plot for CRUSH STRENGHT DRIED Data Means Figure 3 The interaction plot of the drying temperature and drying time on the crush strength in dried extrudate figures 4 and 5 show that only the drying time and the drying temperature has clear affect on the mean crush strength. 50 .0 00 0 40 .3 03 3 35 .0 00 0 29 .6 96 7 20 .0 00 0 10.0 7.5 5.0 2.5 0.0 90 .0 00 0 73 .8 38 8 65 .0 00 0 56 .1 61 2 40 .0 00 0 15 00 .0 0 11 12 .1 3 90 0. 00 68 7. 87 30 0. 00 45 .0 00 0 33 .6 87 2 27 .5 00 0 21 .3 12 8 10 .0 00 0 10.0 7.5 5.0 2.5 0.0 20 0. 00 0 16 7. 67 8 15 0. 00 0 13 2. 32 2 10 0. 00 0 12 0. 00 0 90 .9 10 75 .0 00 59 .0 90 30 .0 00 sODIUM SILIC A TE% M e a n W A TER % RPM TIME OF MIXING DRYING TEMP DRYING TIME Main Effects Plot for CRUSH STRENGHT DRIED Data Means Mixing ,wetting the mixture Gamma alumina+water+sodium silicate Granule Moulding Drying the extrudate Calcination the extrudate Effect of the Forming Conditions in the Production of Gamma Alumina Catalyst Support on the Crushing Strength Property IJCPE Vol.11 No.2 (June 2010) 46 Figure 4 the main effects plot for the crush strength dried Figure 5 the main effect plot for the crush strength calcined. The estimated regression coefficients for the calcined crush strength show that speed of mixing is the only one variable that has a little affect on the crush strength in calcined state. . High crush strength values which is agree with the required minimum values of the alumina support (7Kg/mm) obtained in the experiments shown in table 3.The detailed formulation conditions of the above experiments is shown in table 4. Table 3 details of the experiments of high crush strength in the dried and claimed conditions. Table 4 details of the formulation conditions for the high crush value experiments E x p e ri m e n t S o d iu m S il ic a te % W A T E R % R P M T IM E O F M IX IN G ,m in D R Y IN G T E M P ,C o D R Y IN G T IM E ,m in C A L C IN A T I O N T E M P ,C o T IM E O F C A L C IN A T I O N ,h r, 12 35 65 900 27.5 150 30 500 4.00 13 20 65 900 27.5 150 75 500 4.00 14 29.69 73 687.8 33.6 132. 90. 570 4.70 15 35 65 900 27.5 150 75 500 4.00 16 40.30 73 1112 21.31 132 59. 429 4.70 18 29.696 56 687 21.31 167 90. 570 4.70 24 29.69 73 1112 33.6 132 90. 429 4.70 31 40.30 73 1112 21.31 167 90. 429 4.70 34 29.69 73 1112 33.68 167 90. 429 3.29 37 35 65 900 45 150 75 500 4.00 Figure 6, shows that the best concentration of sodium silicate which give high values of crush strength was 40.30%. 50.000020.000035.000040.303329.6967 180 160 140 120 100 80 60 40 20 0 sODIUM SILICATE% C R U S H S T R E N G H T C A L C IN E D Chart of CRUSH STRENGHT CALCINED Figure 6 Sodium silicate effect on calcined Crush strength No experiment state Crush value,KG 1 12 Calcined 10.545 2 13 Calcined 11.585 3 14 Calcined 13.555 4 15 Calcined 38.36 5 16 Calcined 19.689 6 18 Dried 11.865 7 24 Calcined 13.875 8 31 Dried 10.776 9 31 Calcined 12.07 10 34 Calcined 7.665 11 37 Calcined 10.7042 50.000040.303335.000029.696720.0000 10 5 0 90.000073.838865.000056.161240.0000 1500.001112.13900.00687.87300.00 45.000033.687227.500021.312810.0000 10 5 0 200.000167.678150.000132.322100.000 90.909975.000059.090130.0000 700.000570.711500.000429.289300.000 10 5 0 6.000004.707114.000003.292892.00000 sO D IU M S ILIC A TE % M e a n WA TE R % RP M TIM E O F M IXIN G D RYIN G TE M P D RYIN G TIM E A LC IN A TIO N TE M P TIM E O F C A LC IN A TIO N Main Effects Plot for CRUSH STRENGHT CALCINED Data Means Alaa Dhari Jawad, Ibrahim Richeh, and Riad Ahmed Saleh IJCPE Vol.11 No.2 (June 2010) 47 Figure 7, shows that the best water content which give high crush strength is 65 and 73%, it is compatible with the results of table 3 and 4. 40.000090.000065.000056.161273.8388 180 160 140 120 100 80 60 40 20 0 WATER % C R U S H S T R E N G H T C A L C IN E D Chart of CRUSH STRENGHT CALCINED Figure 7 Water content effect on calcined crush strength Figure 8 show that the best speed of mixing which gives high crush strength is 900 rpm, it is compatible with the results of table 3 and 4. 300.001500.001112.13900.00687.87 180 160 140 120 100 80 60 40 20 0 RPM C R U S H S T R E N G H T C A L C IN E D Chart of CRUSH STRENGHT CALCINED Figure 8 speed of mixing effect on calcined crush strength Figure 9 show that the time of speed which gives high crush strength is between 21-33 minutes, it is compatible with the results of table 3 and 4. 10.000045.000033.687227.500021.3128 160 140 120 100 80 60 40 20 0 TIME OF MIXING C R U S H S T R E N G H T C A L C IN E D Chart of CRUSH STRENGHT CALCINED Figure 9 main effect of the time of mixing on calcined crush strength. Figure 10. shows that the range of the drying temperature which gives high calcined crush strength is 132-150 C o . 200.000100.000150.000167.678132.322 160 140 120 100 80 60 40 20 0 DRYING TEMP C R U S H S T R E N G H T C A L C IN E D Chart of CRUSH STRENGHT CALCINED Figure 10 main effect of drying temperature on calcined Crush strength Figure 11 shows that the drying time which give high calcined crush strength is between 75-90 minutes, it is compatible with the results of table 3 and 4. 120.00030.00075.00059.09090.910 180 160 140 120 100 80 60 40 20 0 DRYING TIME C R U S H S T R E N G H T C A L C IN E D Chart of CRUSH STRENGHT CALCINED Figure 11 main effect of drying time on calcined Crush strength. Figure 12 shows that the calcined time which give high calcined crush strength is 4 hours , it is compatible with the results of table 3 and 4. 6.000002.000003.292894.000004.70711 180 160 140 120 100 80 60 40 20 0 TIME OF CALCINATION C R U S H S T R E N G H T C A L C IN E D Chart of CRUSH STRENGHT CALCINED Figure 12 main effect of the calcination time on Effect of the Forming Conditions in the Production of Gamma Alumina Catalyst Support on the Crushing Strength Property IJCPE Vol.11 No.2 (June 2010) 48 Crush strength Figure 13 shows that the calcination temperature which give high calcined crush strength is 500 C O . 700.000300.000570.711500.000429.289 180 160 140 120 100 80 60 40 20 0 ALCINATION TEMP C R U S H S T R E N G H T C A L C IN E D Chart of CRUSH STRENGHT CALCINED Figure 13 main effect of calcinations temperature on Crushgt strength For dried crush strength the best results was obtained at the following operating conditions: a. Sodium silicate solution concentration 40.30% b. Water content 73% c. Speed of mixing: 900 rpm. d. time of mixing 21 minutes e. Drying temperature 167 C o . f. Drying time 90 minutes. Conclusions: 1. The drying time and the drying temperature are very important variables on the crush strength values of the gamma alumina extrudates while forming them. 2. The best drying temperature is between 150-167 C o ,whileThe best drying time is 1.5hours. 3. There is no interaction effect between the variables studied in forming the gamma alumina extrudate. 4. There is linear regression between the dried crush strength and the drying time and drying temperature. 5. Calcination in general raise the crush strength of the dried extrudate to the required acceptable value. 6. The best calcination temperature and time of calcination are is 500 C o and 4h respectively. 7. The best mixing speed in the step of making the alumina paste and the time of mixing are is 900 rpm and 27 minutes respectively. 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