Preparation Of Bi-Functional Calcium-Based Catalysts And Study For Hydrogen Production On Phenol Reforming

Tar is a kind of complex organic mixture,which cann't be effectively degraded by pyrolysis and incineration.Biomass gasification technology is a clean,efficient and potential utilization method,but the generated CO₂ will affect the quality of syngas.Therefore,it is a meaningful research to obtain a catalyst with high efficiency for tar pyrolysis and good CO₂ capture efficiency.In this paper,CaO-Ca₁₂Al₁₄O₃₃(CaO-C₁₂A₇)was synthesized by two methods.Four kinds of calcium-based catalysts were prepared by loading single metal Ni and bimetal Ni-Ce,respectively.Hydrogen production from phenol,a model tar,was studied in a small fixed-bed reactor.The main conclusions are as follows:?1?Calcium-based carriers were successfully synthesized by calcination-hydration?ch method?and sol-gel/loading?sl method?,and there was no significant difference in composition.In the structure of calcium-based carriers,calcium aluminate(C₁₂A₇)as the carrier of CaO cann't only significantly increase its specific surface area,but also improve the mechanical properties of calcium-based catalysts.Two kinds of calcium-based carriers were loaded with single metal Ni and bimetal Ni-Ce respectively.The BET results showed that the addition of Ce improves the dispersion of NiO particles on the surface,thus increasing the specific surface area of the calcium-based catalyst.?2?Four calcium-based catalysts were prepared for hydrogen production from phenol.The effects of reaction temperature and steam carbon ratio?S/C?were investigated.The results showed that the addition of CeO₂ could significantly promote the production of H₂.The optimum reaction conditions were obtained by using Ni-Ce/CaO-C₁₂A₇ synthesized by ch method as catalyst at 650 C and S/C of 3.At this time,the relative concentration of H₂ reached the maximum of 73.09%,and the production of H₂ was 2.27L/g.Cyclic activity of single metal Ni catalyst was investigated under optimum conditions.It was found that after only four cycles,the H₂ yield decreased to 21.12%of the initial hydrogen production.Which was the result of sintering of Ni particles and reduced the activity rapidly.?3?TG analysis of four calcium-based catalysts after reforming was carried out to investigate the CO₂ adsorption capacity of different catalysts at different temperatures.The results showed that the CO₂ adsorption of the two catalysts of the same type was almost the same,while the CO₂ adsorption amounts before and after the addition of Ce was significantly different.The CO₂ adsorption decreased sharply in the presence of Ce,indicating that CeO₂ had a certain inhibitory effect on CO₂ adsorption.The liquid products of reforming reaction of Ni and Ni-Ce catalysts were analyzed.It was found that the presence of Ce could promote the cracking and conversion of phenol.?4?According to the analysis of H₂ production performance of four calcium-based catalysts under different reaction parameters,the activity of the catalysts prepared by two preparation methods was explored.The results showed that the concentration and quantity of H₂ production of calcination-hydration method were better than that of sol-gel/loading method.Therefore,calcination-hydration method is superior to sol-gel/loading method in the preparation of calcium based carrier.?5?Monometallic Ni catalysts were modified by Co and Cu,and the hydrogen production performance of Ni-Ce,Ni-Co and Ni-Cu in recycling process under optimum operating conditions was investigated.The results showed that the activity of the three modified catalysts is higher than the single metal Ni catalyst.The initial H₂ yield increases from 1.61L/g to 2.31L/g?Ni-Co?.With the increase of cycle numbers,the Ni-Cu catalyst showed the best hydrogen production stability.The Ni-Co catalyst showed higher catalytic activity,while the activity of Ni-Ce catalyst decreases significantly.At the seventh cycle,H₂ yield was only 27.62%of the initial hydrogen production.