Supplementary Information:
Catalyst Activity Test:
The schematic of the experimental set-up is shown in Fig. S1. A tubular flow reactor was
used to carry out the complete oxidation of cyclohexane in air at atmospheric pressure. The
desired inlet concentration of cyclohexane was obtained by introducing an air stream at a
constant flow rate to an isolated bubbling saturator filled by liquid cyclohexane which was kept
in a refrigeration unit to hold the saturator at a constant temperature. The concentration of
cyclohexane in the air flow was calculated by the vapor pressure of cyclohexane at the saturator
temperature. A thermocouple was located at the center of the packed reactor to record the
oxidation temperature. The feed flow rate was set by rotameters. 1 g of the supported catalyst
was placed in the horizontal quartz tubular reactor that was 10 cm in length and 12 mm internal
diameter. Supported cobalt oxide catalyst was packed with glass beads into the middle section of
the reactor in between glass wool to prevent flow channeling. The reactor was heated to the
reaction temperature in the range of (150 to 300oC) and maintained at that temperature using a
PID controller. The concentration of cyclohexane in the feed was adjusted in range of 5000 to
20000 ppm. The reactor exit was analyzed using gas chromatography-mass spectroscopy (GCMass, Agilent model) system that was equipped with 5975C mass detector and HP-5MS stainless
steel column with 30 m, at regular time intervals from the start of each run. Typical GC-MS for
products from the start of a run are seen in Fig. S2. No intermediate oxidation products, carbon
monoxide, hydrogen, cylohexene or cyclohexanol were detected by GC-MS, and the products
included carbon dioxide, water, and unreacted cyclohexane. To investigate the kinetic behavior
of complete oxidation of cyclohexane over HDP catalyst, several experiments were performed to
determine the appropriate conditions (catalyst particles size and feed flow rate) to eliminate both
internal and external mass transfer resistances. All kinetic experiments were performed with
particle size below Mesh number 40 using a feed flow rate of 166 ml/min.
Optimization Strategies for Estimation of Kinetic Parameters
Fig. S3 represents the GA procedure used in this study that can avoid the trapping in the
local optimum. Matlab software version 7.8 was used with appropriate specified parameters
included generation size (1000), population size (30), elitecount, crossover fraction (0.9),
crossover, and mutation functions. Isothermal plug flow with constant fluid velocity and
negligible pressure drop was considered as a simple reactor model.
Oxidation Resistance of Almond Shell Based Activated Carbon
One of the important properties of activated carbon as a support in the oxidation process
is its resistance to oxidation. Figure S4 shows the TGA (Thermogravimetric Analysis) results for
almond based activated carbon indicating no oxidation below 450 C. The carbonization of
almond shell under water vapor at 800 C had increased the oxidation resistance. Almond
activated carbon could therefore be utilized as a support for oxidation of cyclohexane below
400oC and it is stable during BET pretreatment at 300 C. The oxidation resistance of the support
was evaluated by thermogravimetric analysis (TGA) using a TGA-25 apparatus (Mettler-Toledo,
Switzerland) by heating the sample up to 1000 C under an air flow of 55 cm3/min (STP) and a
heating rate of 10 C/min.
Catalyst Preparation Methods
Almond shells were obtained from Iranian local source as an agricultural solid waste.
Powder activated carbon was produced by drying the original almond shells at 120 C for 24 h.
The dried shells were grinded then carbonized and activated under water vapor at 800 C in a
tubular furnace. Prepared activated carbon was washed with distilled water several times to
remove all undesirable materials and was then dried in oven at 110 C overnight. Supported
cobalt oxide catalysts with 8wt. % metal loading were prepared by the following two methods:
1) heterogeneous deposition-precipitation (HDP) and 2) combined impregnation and depositionprecipitation (IMP-DP). In the HDP method, powder almond activated carbon (below mesh
No.40) was placed in a cobalt nitrate solution (Co(NO3)26H2O) (0.04 M) with heating at 70-80
C and stirring for about 8 h. Cobalt ions were precipitated by addition of NaOH solution (6 wt.
%) until reaching a basic solution of pH = 10-11. In the second method, activated carbon was
impregnated with cobalt solution at room temperature for about 3 h. The impregnated solution
was then heated to reach a temperature in the range of 70-80 C. Heterogeneous DP was then
carried out after the impregnation step for 4 h using NaOH. The catalysts prepared by each
method were then washed to reach pH = 7 and dried at 110 C for 6 h. The dried samples were
calcined for 3 h under N2 at 500 C. Supported cobalt oxide catalysts over almond activated
carbon were named IMP-DPCo8/AC500 and HDPCo8/AC500 for IMP-DP and HDP method,
respectively. Details and the flow charts (Figs. S5 and S6) for the catalyst preparation techniques
are presented in the supplementary information file.
Figure Captions:
Figure S1: Schematic of the experimental set-up
Figure S2: GC-Mass of products from catalytic oxidation of cyclohexane at (a) 10 min and (b)
60 min from start-of run
Figure S3: Genetic Algorithm flowchart for kinetic parameter estimation
Figure S4: TGA result for almond shell based activated carbon (heating the sample up to 1000
C under an air flow of 55 cm3/min (STP) and a heating rate of 10 C/min).
Figure S5: Flow chart of heterogeneous deposition-precipitation method.
Figure S6: Flow chart of combined impregnation and deposition-precipitation method.
Figure S1:
Figure S2:
Figure S3:
Start
Optimization
Produce Initial
Population (population
size = 30)
Evaluate Population
Crossover
(0.9)
Mutation
No
Objective
criteria
Generation size = 1000
Yes
End
Figure S4:
100
Weight (%)
80
60
40
20
0
0
200
400
600
Temperature (oC)
Figure S5:
800
1000
Figure S6: