156 AJ.Foster et aL Applied Catalysis A:General 423-424(2012)154-161 Glucose Monocyclic Aromatics Anhydrosugars Furans HO x HO L yco, OH z HCOH Hydrocarbo OH Polyeyclic Aromatics x H2O xHO xHO yCOx yCOx COKE Scheme 1.Proposed reaction chemistry for glucose CFP over ZSM-5. Adapted from Ref.[11]. After synthesis,zeolite samples were washed repeatedly with 2.4.Catalytic testing water,filtered and dried overnight at 80C.Samples were then cal- cined in air at 550C for 6 h to remove occluded organic molecules. Catalytic testing of the zeolite samples for conversion of glucose Zeolite samples were ion-exchanged to the ammonium form by and maple wood was carried out using a semi-batch Pyroprobe treatment in 0.1 M NH4NO at 70C for 24h followed by filtration, reaction system coupled with a HP 5890 Series ll gas chromato- and drying at 80C.The samples were then calcined again at 550C graph and HP 5792 Series mass-selective detector.During a typical to prepare the acid form of the zeolite before catalytic testing. test,a physical mixture consisting of 95 wt%ZSM-5 and 5 wt%glu- Samples used to study the effect of framework SiO2/Al2O3 were cose was prepared and inserted into the reaction chamber.The obtained from Zeolyst with silica-to-alumina ratios of 23,30,50 chamber was heated at a nominal rate of 1000C/s to a final reac- and 80. tion temperature of 600C.Products from the reaction cell were analyzed by GC-MSD.The reaction procedure is described in detail 2.2.Surface dealumination in a previous report 12.The aromatic yield is calculated as the sum of the yields of all non-oxygenated carbon species volatile enough Zeolite samples in the acid form were treated in a 2M L- to be analyzed by the in-line GC.Carbon content in the form of coke tartaric acid solution in water for 1 h at 70C to selectively remove was calculated from combustion elemental analysis performed by surface acid sites (MicZSM-5*and MesZSM-5).After treatment Galbraith Laboratories(Knoxville,TN)after reaction.Mass balances samples were quickly cooled to room temperature,filtered and were calculated on a molar carbon basis.Carbon balances including dried at 80C.The samples were then ion-exchanged with aque- coke,gas products,and aromatics were between 90 and 105%in all ous ammonium nitrate and calcined again as described above.The semi-batch experiments effectiveness of the acid treatment for removal of surface aluminum Conversion of furan was carried out in a 0.5 in.diameter flow was quantified using X-ray photoelectron spectroscopy.The bulk fixed bed reactor.Approximately 57mg of catalyst was loaded composition of the ZSM-5 particles was measured before and after in the reactor.Prior to reaction,the catalyst bed was calcined dealumination using energy dispersive X-ray spectroscopy(EDS) in helium (Airgas,ultra-high purity)at 600C.Furan was fed using a Jeol JSM 7400FScanning Electron Microscope.Samples were via syringe pump (Fisher,KDS100)at a rate of 0.58mL/h into coated with gold using a Denton Vacuum Desk IV sputtering system 408 mL/min ofhelium,resulting in a furan partial pressure of 6 Torr prior to EDS measurements. The furan-containing stream was bypassed around the reactor for 30 min before switching to flow through the reactor.During 2.3.Analytical reaction,the catalyst bed was maintained at 600C and ambient pressure.An air bath condenser was used to trap heavy prod- Powder X-ray diffraction patterns were obtained using a Philips ucts,and gas-phase products were collected in gas sampling bags X'Pert Diffractometer operated at 45kV and 40mA using a Cu After 270s of reaction,the flow of furan was stopped and the source.Electron micrographs and energy dispersive X-ray spectra reactor was flushed with helium for 45 s.The spent catalyst was of zeolite samples were collected using a Jeol JSM 7400F Scan- then treated in air at 600C to burn off accumulated coke.Any ning Electron Microscope.Samples were first coated with gold CO produced was further converted to CO2 over a bed of Cuo using a Denton Vacuum Desk IV sputtering system.X-ray photo- (Sigma-Aldrich)at 240C.The CO2 was trapped by a CO2 trap electron spectra were recorded using a Physical Electronics XPS (Ascarite,Sigma-Aldrich).Coke yield was calculated by measuring system equipped with an Al-anode X-ray generator and multi- the weight change of the COz trap.Gas-phase reaction products channel hemispherical analyzer.Textural characterization of the were analyzed by GC-FID(Shimadzu GC-2014).Gaseous species samples was carried out with a Micromeritics ASAP 2010 adsorp- and coke deposited on the catalyst accounted for the vast majority tion instrument using N2 gas.Samples were degassed overnight of products.In our study,heavy products condensed in the liquid under vacuum at 320C prior to the measurement.Isotherms trap accounted for less than 0.05%of the total carbon fed through were analyzed using the t-plot method to calculate microporous the reactor.As in the semi-batch reactor experiments,mass bal- volume.The mesoporous volume and size distribution were calcu- ances were calculated on a molar carbon basis.Carbon balances lated using the Barrett-Joyner-Halenda method on the adsorption including coke,gas products,and aromatics ranged from 97 to branch of the isotherm. 107%in all fixed bed reactor experiments.Incomplete removal156 A.J. Foster et al. / Applied Catalysis A: General 423–424 (2012) 154–161 O H OH OH OH OH OH O HO HO OH OH OH H2O O O HO OH OH O x HO HO OH O Glucose Anhydrosugars O O O O OH HO O Furans x H2O yCOx z HCOH Hydrocarbon Pool x H2O yCOx x H2O yCOx COKE Monocyclic Aromatics Polycyclic Aromatics x H2O yCOx x H2O yCOx Scheme 1. Proposed reaction chemistry for glucose CFP over ZSM-5. Adapted from Ref. [11]. After synthesis, zeolite samples were washed repeatedly with water, filtered and dried overnight at 80 ◦C. Samples were then cal￾cined in air at 550 ◦C for 6 h to remove occluded organic molecules. Zeolite samples were ion-exchanged to the ammonium form by treatment in 0.1 M NH4NO3 at 70 ◦C for 24 h followed by filtration, and drying at 80 ◦C. The samples were then calcined again at 550 ◦C to prepare the acid form of the zeolite before catalytic testing. Samples used to study the effect of framework SiO2/Al2O3 were obtained from Zeolyst with silica-to-alumina ratios of 23, 30, 50 and 80. 2.2. Surface dealumination Zeolite samples in the acid form were treated in a 2 M l￾tartaric acid solution in water for 1 h at 70 ◦C to selectively remove surface acid sites (MicZSM-5* and MesZSM-5*). After treatment, samples were quickly cooled to room temperature, filtered and dried at 80 ◦C. The samples were then ion-exchanged with aque￾ous ammonium nitrate and calcined again as described above. The effectiveness ofthe acid treatmentfor removal of surface aluminum was quantified using X-ray photoelectron spectroscopy. The bulk composition of the ZSM-5 particles was measured before and after dealumination using energy dispersive X-ray spectroscopy (EDS) using a JeolJSM7400F Scanning ElectronMicroscope. Samples were coated with gold using a Denton Vacuum Desk IV sputtering system prior to EDS measurements. 2.3. Analytical Powder X-ray diffraction patterns were obtained using a Philips X’Pert Diffractometer operated at 45 kV and 40 mA using a Cu source. Electron micrographs and energy dispersive X-ray spectra of zeolite samples were collected using a Jeol JSM 7400F Scan￾ning Electron Microscope. Samples were first coated with gold using a Denton Vacuum Desk IV sputtering system. X-ray photo￾electron spectra were recorded using a Physical Electronics XPS system equipped with an Al-anode X-ray generator and multi￾channel hemispherical analyzer. Textural characterization of the samples was carried out with a Micromeritics ASAP 2010 adsorp￾tion instrument using N2 gas. Samples were degassed overnight under vacuum at 320 ◦C prior to the measurement. Isotherms were analyzed using the t-plot method to calculate microporous volume. The mesoporous volume and size distribution were calcu￾lated using the Barrett–Joyner–Halenda method on the adsorption branch of the isotherm. 2.4. Catalytic testing Catalytic testing of the zeolite samples for conversion of glucose and maple wood was carried out using a semi-batch Pyroprobe reaction system coupled with a HP 5890 Series II gas chromato￾graph and HP 5792 Series mass-selective detector. During a typical test, a physical mixture consisting of 95 wt% ZSM-5 and 5 wt% glu￾cose was prepared and inserted into the reaction chamber. The chamber was heated at a nominal rate of 1000 ◦C/s to a final reac￾tion temperature of 600 ◦C. Products from the reaction cell were analyzed by GC-MSD. The reaction procedure is described in detail in a previous report[12]. The aromatic yield is calculated as the sum of the yields of all non-oxygenated carbon species volatile enough to be analyzed by the in-line GC. Carbon content in the form of coke was calculated from combustion elemental analysis performed by Galbraith Laboratories (Knoxville, TN) after reaction. Mass balances were calculated on a molar carbon basis. Carbon balances including coke, gas products, and aromatics were between 90 and 105% in all semi-batch experiments. Conversion of furan was carried out in a 0.5 in. diameter flow fixed bed reactor. Approximately 57 mg of catalyst was loaded in the reactor. Prior to reaction, the catalyst bed was calcined in helium (Airgas, ultra-high purity) at 600 ◦C. Furan was fed via syringe pump (Fisher, KDS100) at a rate of 0.58 mL/h into 408 mL/min of helium, resulting in a furan partial pressure of 6 Torr. The furan-containing stream was bypassed around the reactor for 30 min before switching to flow through the reactor. During reaction, the catalyst bed was maintained at 600 ◦C and ambient pressure. An air bath condenser was used to trap heavy prod￾ucts, and gas-phase products were collected in gas sampling bags. After 270 s of reaction, the flow of furan was stopped and the reactor was flushed with helium for 45 s. The spent catalyst was then treated in air at 600 ◦C to burn off accumulated coke. Any CO produced was further converted to CO2 over a bed of CuO (Sigma–Aldrich) at 240 ◦C. The CO2 was trapped by a CO2 trap (Ascarite, Sigma–Aldrich). Coke yield was calculated by measuring the weight change of the CO2 trap. Gas-phase reaction products were analyzed by GC-FID (Shimadzu GC-2014). Gaseous species and coke deposited on the catalyst accounted for the vast majority of products. In our study, heavy products condensed in the liquid trap accounted for less than 0.05% of the total carbon fed through the reactor. As in the semi-batch reactor experiments, mass bal￾ances were calculated on a molar carbon basis. Carbon balances including coke, gas products, and aromatics ranged from 97 to 107% in all fixed bed reactor experiments. Incomplete removal