In-situ Synthesis Of FC3R-supported Ni Catalyst And Study Of Rosin/pine Resin Hydrogenation

Fluid catalytic cracking catalyst residue(FC3R)is a large-scale solid waste discharged from petroleum refineries.Heavy metals(Ni,Fe,and V)depose on the catalyst and deactivate it.Disposal in landfills results in environmental problems and resources wastage because of the presence of heavy metal and zeolite structure.Pine resin is natural and can be separated into rosin and turpentine after distillation.Hydrogenated rosin is the largest modified rosin product that is conventionally used in adhesives,coatings,and pharmaceutical and food industries.The major component of turpentine can be transformed to pinane via catalytic hydrogenation,and pinane plays an important role in the synthesis of pharmaceutical products,flavors,and perfumes.Hydrogenated rosin and pinane are traditionally produced with Pd/C catalysts.However,these noble metallic catalysts present disadvantages,such as high cost,poor tolerance,and harsh reactions.Therefore,new catalysts need to be developed,production must be optimized,and the kinetics of hydrogenation should be studied to solve these problems.However,the complex composition of rosin and pine resin makes studying kinetics difficult.In this research,a novel and effective Ni catalyst was developed with FC3R as the support.The reaction processes of rosin or pine resin were modified,and the kinetics of these two reactions were investigated.Impregnation method is a traditional method of synthesizing supported metal catalysts.However,catalysts prepared through this method exhibit weak metal-support interaction,which decrease the activity of catalysts.Layered double hydroxides(LDH)are inorganic materials with a special layered structure;they present several advantages,such as stable structure,uniform distribution of active components,and with high dispersion of metals.LDHs have been widely used as catalysts and support materials.In this work,activated FC3R was utilized as a support and sole Al3+ source for in-situ synthesis of an LDH-derived FC3R-supported Ni catalyst(LP-Ni/FC3R).The structure and properties of LP-Ni/FC3R were characterized through X-ray diffraction,Brunauer-Emmett-Teller surface analysis,H2-TPR/TPD,scanning electron microscopy/energy-dispersive X-ray spectroscopy,transmission electron microscopy,and X-ray photoelectron spectroscopy and compared with those of the FC3R-supported Ni catalyst prepared by the impregnation method(IM-Ni/FC3R).Results showed that the FC3R contains kaolin,Y zeolite,and Al2O3,and the NiAl-LDH was successfully grown in situ on the surface and pore of FC3R.The specific surface area of LP-Ni/FC3R increased from 63.06 m2·g-1 to 108.75 M2·g-1.Compared with IM-Ni/FC3R,LP-Ni/FC3R possessed a smaller crystallite size,higher Ni dispersion,and stronger Ni-FC3R interaction.The effects of temperature,reaction time,and stirring speed on the activity of LP-Ni/FC3R were also investigated.The optimum conditions for preparing the LP-Ni/FC3R catalyst were as follows:Ni loading of 8 wt.%,crystallization temperature of 313 K,crystallization time of 12 h,and stirring speed of 200 rpm.The LP-Ni/FC3R catalyst was used to catalyze the hydrogenation of rosin.Single-factor test and response surface modeling with an experimental Box-Behnken design were implemented to determine the effects of catalyst dosage,reaction pressure,and reaction temperature on rosin hydrogenation and to modify the reaction process.Temperature exerted the most significant effect on abietic acid conversion,and the highest abietic acid conversion of 99.73%was achieved at a temperature of 451 K,H2 pressure of 5.5 MPa,and reaction time of 94 min.LP-Ni/FC3R exhibited higher activity and better stability than IM-Ni/FC3R.After nine times of recycling,LP-Ni/FC3R maintained high hydrogenation activity(89.42%conversion of abietic acid),whereas the conversion of abietic acid was only 61.93%after three times of recycling for the IM-Ni/FC3R catalyst.The thermodynamics of rosin hydrogenation were analyzed with the group contribution method.The reaction enthalpy(?rH?)of partial hydrogenation of abietic acid varied from-115.55 to-114.38 kJ·g-1,and free enthalpy(?rG?)varied from-99.24 to-97.54 kJ·mol-.This result indicates that partial hydrogenation of abietic acid is a spontaneous exothermic reaction.The concentrations of different components over time at a temperature of 423 K to 453 K and the pressure of 3MPa to 6 MPa were traced by via gas chromatography-mass spectrometry(GC-MS).After eliminating internal and external mass transfer limitations,the Levenberg-Marquart method,Matlab program,and Auto2Fit software were used to estimate the parameters of the power dynamic model of rosin hydrogenation.The activation energies for each reaction were between 37.60 and 107.42 kJ·mol-1.The mechanism of rosin hydrogenation over the LP-Ni/FC3R catalyst was discussed using 17 Langmuir-Hinshelwood kinetic models.The most suitable model was(?)and the controlling step in rosin hydrogenation was the surface reaction between the abietic acid molecule and hydrogen atom.The LP-Ni/FC3R catalyst was used to catalyze the hydrogenation of pine resin to obtain hydrogenated rosin and hydrogenated turpentine simultaneously.The effects of reaction conditions,such as reaction pressure,reaction temperature,and reaction time,on pine resin hydrogenation were investigated through a single-factor test and response surface modeling with an experimental Box-Behnken design.The optimum reaction conditions were as follows:reaction temperature of 432 K,hydrogen pressure of 6 MPa,and reaction time of 75 min.Under these conditions,the conversion of abietic acid-type acids and pinene and the selectivity of cis-pinane were 96.90%,98.84%,and 82.15%,respectively.The concentrations of different components over time at a temperature of 413K to 443 K were traced by GC-MS.Lumping theory was utilized to divide the components of pine resin and its hydrogenated products into pinene,cis-pinane,tra-pinane,abietic acid-type resin acids,pimaric acid-type resin acids,hydrogenated abietic acid-type resin acids,and hydrogenated pimaric acid-type resin acids.Internal and external mass transfer limitations in pine resin hydrogenation were eliminated at a stirring speed of 600 rpm and particle size of<80 ?m.The kinetic model of the hydrogenation of pine resin and the reaction rate constants were estimated using Matlab and Auto2Fit software.The activation energies(Ea)for pinene hydrogenation,abietic acid-type resin acid hydrogenation,and pimaric acid-type resin acid hydrogenation range from 23.98 kJ·mol-1 to 111.05 kJ·mol-1.The data from the lumped kinetics model fit the experimental results well,and the confidence interval was narrow.F-test showed that the results were statistically significant.