Study On Active Site,Pore Structure Regulation And Performance Of Supported Ni-based Hydrodeoxidation Catalyst

Bio-oil has been well known for its advantages of low price,abundant storage and less pollution.Pyrolysis is an important way to utilize bio-oil.However,there are a large number of oxygen-containing groups in the crude bio-oil produced during pyrolysis,resulting in low calorific value of bio-oil and low added value of products.Therefore,it is necessary to obtain high-quality bio-oil by hydrodeoxygenation（HDO）.Therefore,the development of cheap and efficient HDO catalysts is key.In this paper,nickel nitrate was used as nickel source,aluminum nitrate and sodium metaluminate were used to modify SiO₂ base support,and the preparation method of special structure of radioactive silicon dioxide（DMSN）support was explored.A series of supported Ni,Ni₂P and Ni@C,Ni₂P@C catalysts were prepared.The catalysts were characterized by XRD,BET,SEM,TEM,H₂-TPR,NH₃-TPD,XPS and Py-FTIR.Using m-cresol as the model compound,the HDO performance of the catalyst was studied.Experimental results show that:SiO₂ support was modified with aluminum nitrate,and the effect of Al addition amount on the HDO performance of Ni/SiO₂-Al-x catalyst was studied.The results showed that the incorporation of Al increased the acidity of Ni/SiO₂-Al-x catalyst and promoted the dehydration of MCHnol to MCH reaction.The HDO activity of Ni/SiO₂-Al-5 catalyst prepared with the addition of 5%Al is the best,and the M-cresol conversion of Ni/SiO₂-Al-5 catalyst reaches100%and the deoxidation product selectivity reaches 100%when the reaction time is 120 min at 250℃and 3 MPa.A radial silica nanosphere material carrier modified with sodium metabaluminate was designed and prepared,and Ni/DMSN-Al-x catalyst with different Al contents was prepared by one-pot method.The results show that the Ni/DMSN-Al-x catalyst has a spherical shape with a three-dimensional radial structure and the size is about 200 nm.The doping of Al can improve the specific surface of the catalyst,the dispersion of Ni and the acidity of the catalyst.Among Ni/DMSN-Al-x catalysts,the Ni/DMSN-Al-10 catalyst prepared with Si/Al=10 has the best HDO performance.Under the conditions of 10 m L n-dodecane solvent,0.149 g m-cresol,20mg catalyst,reaction temperature 250℃,reaction pressure 3 MPa,reaction time 75 min,the Ni/DMSN-Al-10 catalyst with radial channel structure can achieve the M-cresol conversion of99.8%,and the selectivity of deoxidation product is 100%.Carbon coated Ni₂P@C/DMSN-Al catalyst with radial channel structure was prepared by phosphating using sodium hypophosphate as P source.It was found that compared with the non-phosphating Ni@C/DMSN-Al catalyst,the specific surface area of the catalyst decreased and the acidity increased after phosphating,which was conducive to the dehydration of MCHnol and the formation of MCH reaction.Under the conditions of 10 m L n-dodecane solvent,0.149 g m-cresol,20 mg catalyst,reaction temperature 250℃,reaction pressure 2 MPa,reaction time 60 min,the conversion of m-cresol between Ni₂P@C/DMSN-Al catalyst reached99.9%,and the selectivity of deoxidation products was 99.0%.Compared with the non-phosphating Ni@C/DMSN-Al catalyst,the conversion rate was improved by 10%and the selectivity was improved by 6%.