Role of support bio-templating in Ni/Al2O3 catalysts for hydrogen production via dry reforming of methane

Bio-templating, a synthetic approach inspired by nature, is an emerging area in material engineering. In this study, waste leaves of Sycamore were utilized as a bio-template for producing alumina support to prepare catalyst. The performance of Ni and Ce impregnated on bio-templated alumina support was investigated in dry reforming of methane for the first time. The effect of process and catalytic variables were examined in detail. The results showed that impregnation of 20% Ni and 3% Ce on the bio-templated alumina led to improved Ni dispersion and achieving the maximum CH4 conversion of 88.7%, CO2 conversion of 78.5%, and H2 yield of 85.3%, compared to 84.4%, 75.6% and 83.4% for the non-templated catalyst at 700 °C, respectively. Detailed characterization of the catalysts revealed that the enhanced performance in the bio-templated catalyst could be attributed to smaller Ni particles, superior dispersion of Ni on the support, the mesoporous structure of alumina, and the larger surface area of support. Furthermore, analysis of the used catalyst showed reduced coke formation on the catalyst surface and high stability of bio-templated catalysts, highlighting the main advantage of bio-templated catalysts over non-templated ones. The findings presented in this study contribute to the potential future applications of bio-templating materials and shed light on the rational design of bio-templating materials.


Pre-treatment of bio-template
The waste leaves were initially pre-treated to remove contaminants and get rid of inorganic ions.To this end, the leaves were immersed in dilute acid (5% v/v HCl) overnight.Next, they were washed with deionized water several times to remove acid, and then dried in an oven for 24 h.Consequently, the treated leaves were crushed using a mini-laboratory electric grinder to form a fine yellow powder (Step I in Fig. 1).

Synthesis of final catalyst
The alumina support was prepared by the sol-gel method.For this purpose, 4 g Al[OCH(CH 3 ) 2 ] 3 precursor salt was initially solved in 150 ml acidic water (pH = 4) and stirred for 3 h at 80 °C, followed by standing at the same temperature for 12 h.Subsequently, 2 g of the treated waste leaves were soaked in alumina precursor solution and stayed at 80 °C overnight.Next, the solution was filtered and dried in an oven at 100 °C for 30 min and calcined in a furnace at 800 °C for 3 h under air.The obtained white powder is designated as "Bio-Al" in the text (Step II in Fig. 1).To investigate the effect of bio-templating, a non-templated (bulk) alumina sample was prepared using the same procedure, except adding the bio-template.The non-templated Al 2 O 3 was named Bulk-Al in the manuscript.
The wet impregnation method was employed to introduce the active phase (Ni) and promoter (Ce) to the prepared alumina.For this purpose, separated aqueous solutions of Ce(NO 3 ) 2 .6H 2 O and Ni(NO 3 ) 2 .6H 2 O with 0.05 M concentration were added dropwise to the suspension of prepared Bio-Al in the water simultaneously while stirring at 40 °C for 4 h.The prepared solid pastes were then kept in an oven at 100 °C for 15 h.Finally, the obtained samples were calcined at 650 °C for 3 h at a rate of 4 °C/min (Step III in Fig. 1).The calcined catalysts were designated as (z)Ni-(x)Ce@Bio-Al for bio-templated catalysts and (z)Ni-(x)Ce@Bulk-Al and in the text, in which z is Ni weight percentage with 10, 15, 20 and 25 wt% amounts, and x is Ce weight percentage with 0, 1.5, 3, and 4.5 wt% loadings.The amount of Ni and Ce loading ranges were chosen based on literature review 37,44,45 .Figure 1 presents a schematic of catalyst preparation steps.

Catalyst characterization
Power X-ray diffraction (XRD, PHILIPS X'Pert PW1730) with a Cu-Kα monochromatizer (40 kV, 30 mA) and a Cu anode X-ray tube was used to analyze the crystalline phases of the samples.The catalyst morphology and structure were characterized by a field-emission scanning electron microscope (FESEM, TESCAN MI RA III) and a transmission electron microscope (TEM, Philips CM120).Energy-dispersive X-ray spectroscopy (EDX) analysis was used with a SAMX detector coupled with the FESEM instrument to measure the elemental composition of samples and their dispersions.Nitrogen adsorption-desorption isotherms were obtained using a surface area and porosity analyzer BELSORP MINI II at 200 °C.The Brunauer-Emmett-Teller (BET) methods and Barrett-Joyner-Halenda (BJH) models were used to calculate the specific surface areas of the mesopores and pore-size distributions, respectively.Temperature-programmed hydrogen reduction (H 2 -TPR, NanoSORD NS9) was used to study the reducibility of catalysts.The thermogravimetric analysis (TGA) technique was used to determine the thermal stability and amount of deposited coke on the synthesized catalysts with the aim of an SDT Q 600 instrument.Raman analysis was carried out to get information about the type of deposited coke using Raman spectrometer (Technooran company-model Ram-532-004).The inductively coupled plasma optical emission spectrometry (ICP-OES) technique was used to analyze the chemical compositions of final catalysts (VISTA-PRO spectrophotometer instrument).

Catalyst activity in dry reforming of methane
To determine the effectiveness of the prepared catalysts in the DRM process, practical tests were carried out at atmospheric pressure using an isothermal stainless steel fixed-bed reactor with a diameter of 1.6 cm and length of 1 m (Fig. S2).An electric furnace was used to control the reaction temperature.In a typical experiment, 1 g of the synthesized catalyst (catalyst size: 150-200 µm) was loaded into the reactor.Subsequently, the catalyst was reduced by elevating the reactor temperature to 750 °C for a duration of 1 h, using pure hydrogen with a flow rate of 150 ml/min.In the next step, the reactor temperature was fixed to the reaction temperature (600, 650, and 700 °C) and pure nitrogen was passed till reaching this temperature.CH 4 and CO 2 were then introduced into the reactor by the ratio of unity following the reaction's stoichiometry, and a flow rate of 100 ml.min -1 with the constant gas hourly space velocity (GHSV) of 12,000 ml g cat −1 h −1 for 1 h.Six injections of an online Bruker 450 gas chromatograph (GC) instrument with a TCD were taken to analyze the composition of the exited dry gas stream at each reaction temperature.The TDX-01 column was used for gas separation and argon was applied as a carrier gas.A schematic presentation of the set-up is shown in Fig. 2.
(2) where F CH 4 , F CO 2 ,F H 2 , and F CO refer to CH 4, CO 2 , H 2 , and CO molar flow rates, and in and out subscripts denote input and output streams, respectively.

Thermodynamic study
The thermodynamic analysis was conducted to understand the operating conditions in DRM and compare the theoretical values with the experimental ones.Predicting the equilibrium conversions is helpful to determine which reaction is complete and the extremum amount of each product 48 .The DRM reaction (Eq. 1) was considered as the main reaction and three other reactions, including reverse water-gas shift reaction (Eq.6), methane cracking (Eq.7), and CO disproportion (Eq.8), were considered as the side reactions 49 .
The equilibrium thermodynamic calculations were carried out using Aspen Plus software Version 12.1.The thermodynamic model of Peng-Robinson thermodynamic was chosen for our system.Reactions 1, 6-8 with feed ratio (CO 2 /CH 4 ) of unity and pressure of 1 bar were considered in this simulation.Temperature was set from 600 to 700 °C using sensitive analysis.

Activity tests in dry reforming of methane
To investigate the effect of support bio-templating on DRM performance and optimize the Ni and Ce percentages, the prepared catalysts with and without bio-template were tested at three temperatures (600, 650, and 700 °C).CH 4 and CO 2 conversion, H 2 yield, and H 2 /CO ratio were calculated according to Eqs. ( 2)-( 5), respectively.The results of CH 4 and CO 2 conversion for 10, 15, 20, and 25% Ni loading are shown in Fig. 3a Reverse water − gas shift : www.nature.com/scientificreports/CO 2 conversion by enhancing the reaction temperature for all samples, regardless of the support structure and Ni loading amount.This can be attributed to the endothermic nature of DRM (Eq.1), meaning that raising the temperature enhances the equilibrium conversion and leads to higher CH 4 and CO 2 conversion 30,50 .Furthermore, at higher temperatures, molecular collisions are more effective, further facilitating the reaction.For instance, by boosting the temperature from 600 to 700 °C for 25% Ni loading, the CH 4 and CO 2 conversion were increased by 25.2% and 27.5% for the bio-templated and 26.9% and 32.9% for the non-templated catalysts.Higher CH 4 conversion than CO 2 conversion is due to reverse water gas reaction (Eq.6).
Results of H 2 yield and H 2 /CO ratio are shown in Fig. 4a-d for different amounts of Ni loading.Regarding products, H 2 /CO molar ratio is more than unity and less than 2 in all cases due to carbon accumulation.Therefore, this catalyst is an appropriate option for applications where high amounts of hydrogen are needed.As can be seen in this figure, the highest H 2 yield were obtained for 20Ni catalyst for both non-templated and bio-templated catalysts.It is noteworthy that the highest H 2 yield is at 700 °C48,51 .Regarding H 2 /CO ratio, in almost all Ni loadings, the minimum H 2 /CO ration was observed at 650 °C, either for the templated or non-templated catalyst.
By examining the effect of Ni loading amount, it is evident that increasing the Ni content from 10 to 20% enhances CH 4 and CO 2 conversion, and H 2 yield.This improvement can be attributed to the availability of more active sites and larger surface areas at higher Ni loadings.However, further increasing the Ni content (25%) has a detrimental effect, resulting in decreased CH 4 and CO 2 conversion, and H 2 yield.This decline could be ascribed to the agglomeration of Ni particles, leading to the loss of active sites and surface area.This agglomeration is more pronounced in higher temperatures.In summary, loading 20% Ni demonstrated the best performance, either for the bio-templated (CH 4 and CO 2 conversion, and H 2 yield of 80.7%, 56.4%, and 75.8% respectively, at 700 °C), or the non-templated catalyst (CH 4 and CO 2 conversion of 75.4%, 52.1%, and 75.6% respectively, at 700 °C).
Figure 3 also highlights the remarkable influence of support bio-templating in achieving higher CH 4 and CO 2 conversion, and H 2 yield regardless of Ni loading amount.This effect can be ascribed to multiple factors, including the more porous structure of bio-templated alumina, smaller Ni particles and their better distribution on the support in the case of bio-templated alumina compared with non-templated one, which have been confirmed by the characterization results, presented in the subsequent sections.Consequently, the bio-templating approach mitigates Ni particles' agglomeration and is predicted to reduce coke formation and minimize catalyst deactivation.Details of excited gaseous products from the GC column are presented in Table S1.
To determine the effect of adding the promoter, different amounts of Ce (1.5, 3.0, and 4.5%) were loaded on both bio-templated and non-templated catalysts.CH 4 and CO 2 conversion and H 2 yield were calculated for  -S5.The figures demonstrate that the addition of Ce promotes higher CH 4 conversion and H 2 yield.This can be attributed to the activation of CO 2 facilitated by CeO 2 and a reduction in coke formation.When higher Ce loading is used (up to 3%), this increscent is more noticeable.At 3% Ce loading, the highest improvement in CH 4 conversion (9.9% for bio-templated and 11.9%  www.nature.com/scientificreports/for non-templated catalysts) and H 2 yield (5.7% for bio-templated and 10.6% for non-templated catalysts) were achieved at 20%Ni loading and 700 °C.However, further increasing the Ce content (4.5%) adversely affects both CH 4 conversion and H 2 yield, possibly due to agglomeration of Ce particles.Similar to the previous observations, a direct relationship between temperature and catalytic performance is evident, which is due to the endothermic nature of DRM.Higher amounts of CH 4 conversion and H 2 yield were obtained for the bio-templated catalysts compared with the non-templated ones for all Ce loading amounts.
In summary, the optimal CH 4 conversion and H 2 yield of 88.7% and 85.3% were achieved by loading 20% Ni and 3% Ce on the bio-templated support and 84.4% and 83.4% on the non-templated catalysts, respectively at 700 °C.The superior performance of the bio-templated catalysts can be attributed to the presence of smaller Ni particles that are better distributed on the bio-templated support.For a better understanding, the optimized catalysts, both with and without bio-template, underwent characterizations, which the results are presented in the following section.

Characterization of the fresh optimized catalyst
In the present study, the alumina support was synthesized in the presence of waste leaves, as shown in Fig. 1.These leaves served as a natural scaffold to improve the physical properties of catalysts.Additionally, a nontemplated support was prepared for comparison purposes.To investigate the structural and morphological characteristics of both bio-templated and non-templated catalysts, various techniques were employed.
To evaluate the effect of bio-templating on catalysts' morphology and structure, the FESEM analysis was conducted.A comparison between the FESEM images of bulk alumina and bio-templated alumina (Fig. 6a  and b) shows that the non-uniform and low-porous structure of bulk alumina was remarkably affected by the bio-template and resulted in a uniform and porous structure with spherical-shape particles and size range of 44.92-91.46nm.Moreover, the overall morphology of the leaf was successfully retained within the alumina support, which is evidence of the successful synthesis bio-templating route.This observation is further supported by the TEM image of the bio-templated alumina, as shown in Fig. 6c, which confirms the formation of an ordered and uniform mesoporous structure in the supporting material in the presence of bio-template.The TEM image in Fig. 6d presents the presence of Ni and Ce on the porous structure of alumina.
The templated alumina serves as an appropriate support for immobilizing Ni and Ce particles while maintaining the structure provided by the template.The agglomerated particles were observed after adding Ni to the alumina (Fig. 7a).However, after the addition 3% Ce to the 20% Ni@Bio-Al surface (Fig. 7b), well-dispersed particles with smaller sizes are observed.
To prove the presence of Ni and Ce in the prepared catalysts, EDX analysis was also conducted.The results are presented in Fig. 7a and b for 20% Ni@Bio-Al with and without 3% Ce, respectively.As expected, Al, O, Ni, (and Ce) components were detected in these samples, with a porous structure in their alumina mapping images, facilitating the effective dispersion of Ni or Ni-Ce particles on the alumina surface.The actual chemical compositions of 3%Ce-20%Ni on the templated and non-templated support using ICP analysis is presented in Table S2.The results show the presence of Ni and Ce, and highlight that bio-template did not affect the presence of Ni and Ce.The XRD patterns of catalysts were obtained in the 2θ range of 10-80°, in which all samples were well crystallized.Both bio-templated and non-templated catalysts showed diffraction peaks at 2θ = 45.2°, and 65.4° related to Al 2 O 3 (Fig. 8).The presence of alumina diffraction peaks in samples after impregnation with Ni and Ce indicates that the crystal structure of alumina remained unchanged during the impregnation process.The peaks related to NiAl 2 O 4 (at 37.5°) and Ni 0 (at 44.5° and 75.6°) were detected in both bulk and bio-templated samples.By calcination of the samples at 650 °C, enough energy was obtained by Ni ions to overcome the surface barrier of alumina and result in spinel structure from incorporating into alumina lattice.This results in reacting NiO with Al 2 O 3 and forming NiAl 2 O 4 .The lower intensity of Ni 0 and NiO peaks in the bio-templated catalyst confirms the smaller size and better distribution of Ni in the templated support, which resulted in better performance of bio-template catalysts in DRM.Meanwhile, the CeO 2 peaks could not be detected in both bio-templated and non-templated catalysts due to its low content.
The TPR analysis was carried out to determine the reducibility of nickel species on the templated and nontemplated alumina surfaces and their interaction strength in the calcined catalysts 52 .As per Fig. 9, there is one main peak at more than 700 °C with a small shoulder peak at 350-550 °C for all samples.The peak in the range of 350-550 °C belongs to NiO species reduction with a low interaction with the alumina support.The peak at more than 700 °C is attributed to the Ni species strong chemical interaction with alumina support (NiAl 2 O 4 ), which consists well with the XRD results.Shifting the highest peak to higher temperatures for bio-templated catalysts presents a stronger interaction between Ni and Al.Therefore, the Ni particles are more properly distributed by bio-templating, which is consistent with XRD results Compared with the non-promoted catalysts, the promoted catalysts showed a higher reduction temperature, which indicates much stronger metal-support interaction which will result in a higher stability of the catalyst.Although adding Ce did not change the place of peaks significantly, more hydrogen is consumed in the promoted catalyst, which shows a higher oxygen storage capacity of 3% Ce-20% Ni@Bio-Al catalyst than 20% Ni@Bio-Al, and thus its lower tendency for coke deposition during the DRM reaction.This indicates that bio-templating promoted the formation of Ni species that had a strong interaction with the support, which is consistent with the XRD results.The textural properties of catalysts with and without bio-template were determined via the N 2 adsorption-desorption analysis, which results are summarized in Table 1.The adsorption-desorption isotherms and the pore size distributions are also shown in Fig. 10a and b, respectively.For all samples, the isotherm presented a typical type IV curve with H3 shaped hysteresis loop.The hysteresis loops for all samples started at about 0.4, which was characteristic of mesoporous material, as was confirmed by the FESEM and TEM analysis.The uniformity   www.nature.com/scientificreports/ of mesoporous structure is proven by the sharpness of the capillary condensation stage.Figure 10b illustrates a narrow pore size distribution in approximately equal center points of 4.00nm for 20%Ni@Bio-Al and 3% Ce-20% Ni @Bio-Al samples.The sharper peak in Bio-Al supporting material indicates a higher number of pores in this confined range and a blockage of some pores by Ni and/or Ni-Ce particles, as indicated by the adsorption and desorption diagrams.As per Table 1, the specific BET surface areas and pore volumes of each sample are different.The bio-templated samples showed higher textural properties compared with the non-templated samples, which shows the synergic effect of bio-template in increasing the surface area of catalyst.After impregnating Ni, the surface area of templated catalyst decreased from 214.01 m 2 /g of pure Al 2 O 3 to 173.23 m 2 /g 19,53,54 .The BET surface area of the promoted sample did not change significantly against the un-promoted one, which can be correlated to the enhancement effect of CeO 2 particles on the dispersion of NiO active sites that caused smaller particles and thus lower pore blockage of the supporting material.A slight reduction in surface area can be attributed to the deposition of Ce inside the catalyst.Therefore, the pore volume and pore size of promoted catalysts become somewhat smaller than un-promoted ones as still small pores of alumina support are not covered by active sites.

Stability test during long-term reaction
The time-on stream reaction tests were carried out for 30 h at 650 °C using the optimized 3% Ce-20% Ni on bio-templated and non-templated catalysts to evaluate their stability and coke resistance.Figure 11 shows the  www.nature.com/scientificreports/results for CH 4 conversion.The initial CH 4 conversions were 84.8% and 81.8% for the bio-templated and nontemplated catalysts, respectively.The methane conversion of bio-templated catalyst remained almost stable and only a 1.76% reduction resulted after 30 h reaction, showing its good stability.It is while, the non-templated catalyst experienced a 24.81% loss in CH 4 conversion after 30h, indicating its less stability compared to the biotemplated catalyst.These results present less coke formation and sintering for the bio-templated catalyst, which is consistent well with what expected from the TPR and XRD results of fresh bio-templated and non-templated catalysts (Figs. 8 and 9) and stability is more in case of bio-templated catalyst as expected.Due to the higher stability of the bio-templated catalysts, the characterization analysis was done for this catalyst after 30 h long-time reaction to determine the factors participating in the catalyst deactivation, which are presented in the following.
The XRD patterns of the bio-templated catalyst before and after the reaction are depicted in Fig. 12.In the pristine catalyst, the presence of Al 2 O 3 , NiO, Ni 0 , and NiAl 2 O 4 phases was confirmed.However, in the used catalyst, additional carbon peaks emerged, indicating the formation of coke.Furthermore, the intensity of NiO and Ni 0 peaks was higher, suggesting a larger particle size due to sintering.These results show that despite the bio-templated catalyst experiencing slight sintering and coke formation during the 30 h DRM reaction, it has good stability, which is in line with the FESEM, TGA, and BET results.
The N 2 adsorption/desorption isotherm of 3% Ce-20% Ni @Bio-Al after 30 h of the DRM reaction is illustrated in Fig. 13a.According to this figure, the type of isotherm is same as its fresh state (IV type with an H3  www.nature.com/scientificreports/hysteresis loop), showing that the bio-template catalyst's structure did not change after 30h reaction.However, its hysteresis loop becomes closer after the reaction, possibly due to the blockage of small pores by deposited coke or the sintering of the catalyst at high temperatures.As a result, its BET surface area had reduced by 7.85% and its pore size (Fig. 13b) and pore volume were increased slightly due to coke formation, which was also confirmed by the XRD results (Table 2).The FESEM and EDX results of 3% Ce-20% Ni@Bio-Al are shown in Fig. 14 to determine the amount of coke formation.According to the results of the elemental composition the elements of Al, Ni, Ce, C, and O have been detected in this catalyst with a low carbon content of 4.91 wt% after 30 h DRM time-on-stream.This observation is in line with the findings of the FESEM image, in which dark areas that present coke deposition on the catalyst surface are not observed.The comparison between FESEM images of 3% Ce-20% Ni @Bio-Al before and after the high-temperature DRM reaction indicates that some Ni particles are sintered and stuck together after the reaction.
TGA analysis was used to evaluate the thermal stability of the catalyst and determine the amount of carbon deposited on the catalyst's surface after 30 h DRM reaction at 650 °C.Given that, the fresh catalyst was heated to 1000 °C under Ar media with 20 °C/min heating ramp, while the used catalyst was heated to this temperature using air molecules to burn the coke deposited on its surface.As presented in Fig. 15, the bio-templated catalyst showed a sharp reduction in its weight percentage before 100 °C, which is caused by the desorption of H 2 O and other adsorbed reactants 55 .For the case of the non-templated catalyst, the weight of the used catalyst initially decreased until 200 °C (Fig. 15a) due to the desorption of adsorbed water molecules.Following this reduction, an increment was observed in the weight of the non-templated catalyst between 200 °C and 600 °C due to reoxidation of the Ni active sites under oxidative atmosphere.In this case TGA profile is not reliable to determine the type of coke and the Raman analysis was further done to analyze the type of carbon in non-templated catalyst.From the Raman spectra in Fig. 15b two main peaks at 1361.098 cm −1 (disordered sp 2 hybridized carbons named D band) and 1588.67 cm −1 (sp 2 hybridized graphite-like carbons named G band) are observed, which are respectively correspond to amorphous and graphitic carbon [12][13][14][15]56,57 . The sarp loss of weight after 600 °C is the result of oxidation of deposited carbon on 3%Ce-20%Ni@Bulk-Al after 30h DRM reaction at 650 °C.It was assumed that there was no significant deposited carbon oxidation below 600 °C.The bio-templated catalyst's weight decreased slightly by only about 8.06% until the end of the analysis, representing the bio-templated catalyst's good thermal stability.It is while the total weight loss was 20.70% for the non-templated catalyst.Typically, three types of carbon can be formed and detected using TGA analysis; amorphous carbon at about 320 °C, filament carbon in the range of 320-520 °C, and graphitic carbon at temperatures more than 650 °C.Considering this, the detected deposited carbon on bio-templated catalysts is attributed to amorphous and filament carbon.

Thermodynamic analysis of DRM
The results of thermodynamic equilibrium studies for CH 4 , CO 2 conversion, and H 2 /CO ratio in products at the temperature range of 600-700 °C is shown in Fig. 16a and b.It is noteworthy that the feed ratio was CH 4 :CO 2 = 1:1 and pressure was 1 atm.It is evident that temperature has a significant effect on CH 4 and CO 2 conversions.The CH 4 and CO 2 conversions are small at lower temperatures (600 °C), while they are enhanced by increasing temperature to 700 °C.For the strong endothermic reaction of DRM, the equilibrium conversion of CH 4 and CO 2 increases dramatically with increasing reaction temperature.Thus, high conversion is favored at high temperatures.The moderate endothermic reactions, methane decomposition, and the reverse water-gas shift reaction, also increase with temperature.The two carbon deposition reactions, the Boudouard reaction and the reverse carbon gasification reaction, are exothermic and thermodynamically unfavorable at high temperatures.Therefore, high reaction temperatures (i.e., 700 °C and above) are more favorable to increasing the equilibrium conversion of the main reaction than that of the side reactions.

Comparing results in present work with the similar studies
For the sake of fair comparison, the performance of the best catalyst evaluated in the present study (20%Ni-3%Ce on bio-templated alumina at 700 °C) with similar works in previous studies in the DRM reaction, Table 3 is presented.According to Table 3, CH 4 conversion varies between 54.5% and 94%, using different promoted or

Conclusion
In the present study, the waste leaves of Sycamore were utilized as the scaffold to prepare alumina for catalyst support, with the subsequent co-impregnating Ni and Ce on the bio-templated alumina.Comparing the activity of a bio-templated catalyst with a non-templated one in the same condition proved that the bio-templated catalyst has higher efficiency and excellent stability in DRM reaction.The enhanced catalytic performance can be attributed to higher surface area, improved Ni dispersion on support, and stronger Ni-Al interaction in biotemplated catalyst compared to the non-templated one.The optimal catalytic performance was achieved with 20% Ni and 3% Ce loading at 700 °C for both catalyst types.The successful bio-template synthesis approach was evident from the FESEM images, which reveals a uniform and highly porous structure.XRD, TPR, and N 2 adsorption/desorption analyzes confirmed strong interaction between nickel and alumina and enhanced surface area in templated catalyst.The templated catalyst showed enhanced stability, reduced catalyst deactivation by coke formation and sintering during 30 h DRM.

Plant material
The waste leaves of Sycamore that fell in autumn were collected as the bio-template under the Environmental Organization of Shiraz University by considering Institute of Standards & Industrial Research of Iran (http:// www.isiri.com).

Figure 1 .
Figure 1.A schematic of Ni-Ce@Bio-Al preparation process: (I) preparation of bio-template, (II) preparation of Bio-Al support, (III) co-impregnating of Ni and Ce on Bio-Al to prepare the final catalyst.

Figure 11 .
Figure 11.Time on stream reaction for bio-templated and non-templated catalysts.

Figure 15 .
Figure 15.(a) TGA profile of spent bio-templated and non-templated catalysts, (b) Raman spectra of spent non-template catalyst.
to d.It is noteworthy that the promoter had not added at this stage.The results indicate a clear increasing trend of CH 4 and

Table 3 .
A comparison of the CH 4 conversion for similar studies.