Study On The Properties Of In-Situ Crystallization Catalysts For Heavy Metals

In this paper,the crystallization products in the in-situ crystallization process are used as raw material,and phosphoric acid,citric acid,magnesium chloride and a solution containing rare earth elements are used as modified substances respectively.The in-situ crystallization after modification is prepared by impregnation method and ion exchange method.The specific surface area,crystallinity,and acid amount of the in-situ crystallization catalyst are used as evaluation indexes,and a suitable mass fraction of various modified substances is preferable.Then,the activity of the catalyst was further evaluated by a micro-reaction activity experiment.The catalyst was subjected to heavy metal nickel and vanadium,contamination experiments,and then applied to fixed fluidized bed experiments so as to evaluate its catalytic performance and resistance to heavy metals such as nickel and vanadium.(1)Phosphorus-modified in-situ crystallization catalyst can increase appropriately the specific surface area.And its acidity is effectively modulated.Under the condition of nickel pollution,when the phosphorus was loaded 1.5%,the micro-reaction activity of the catalyst decreased by 9 percentage points compared with the blank sample.The results of fixed fluidized bed experiments show that under the condition of nickel pollution,when the phosphoric acid modification amount on the catalyst is 1.0%,the dry gas and coke yield are reduced by 0.82 percentage points and 4.36 percentage points compared with the blank sample.C5+-gasoline is collected.The rate change is very small,just increasing by 0.03 percentage points,the diesel yield increased by 3.54 percentage points.The product distribution is general.The catalytic reaction performance is not significantly improved,and the effect on the nickel resistance of the catalyst is less.(2)The citric acid modified in-situ crystallization catalyst can increase its specific surface area.It has little effect on the crystallinity;and can greatly reduce the amount of L acid Under the condition of nickel pollution,when the modification amount of citric acid on the catalyst was 1.5%,the micro-reaction activity decreased by 7 percentage points.The results of fixed fluidized bed experiments show that under the condition of nickel pollution,when the modification amount of citric acid was 1.0%,the conversion rate of heavy oil increased by 4.09 percentage points compared with the blank sample.The yield of C5+gasoline increased by 4.30 percentage points.The yield of diesel oil decreased by 1.84 percentage points.The heavy oil yield decreased by 2.35 percentage points.At the same time,the coke yield decreased by 3.65 percentage points.The dry gas yield decreased by 0.55 percentage points.The hydrogen to methyl ratio decreased by 0.26 percentage points.The product selectivity increased.The product distribution became better,and the nickel resistance performance improved.(3)The magnesium-modified in-situ crystallization catalyst can slightly increase the specific surface area of the catalyst;the relative crystallinity increases by 1 percentage points.The acidity decreases,Under the condition of nickel pollution,magnesium was found at the first,second and third positions in the catalyst preparation process,and the micro-reaction activity of the sample was found to decrease,but the decrease was small,when the amount of magnesium modified At 0,6%,the microreaction activity of the catalysts in the three processes was good.In addition,under the condition of nickel pollution,the effect of magnesium on the catalytic performance of the catalyst at three locations was investigated.It was found that under the same conditions,the gasoline yield at the first magnesium was slightly increased,and the third magnesium was added.The increase of heavy oil conversion rate is more obvious,and the diesel oil yield and heavy oil yield in the three processes are not changed much.On the whole,the effect of magnesium on the third place is better,and the ability to resist nickel pollution is relatively strong.(4)The rare earth-modified in-situ crystallization catalyst has little effect on the specific surface area and crystallinity of the catalyst.It can increase the amount of B acid and L acid.Under the condition of vanadium pollution,when the rare earth modification amount on the catalyst is 1.5%,the micro-reaction activity of the catalyst increases by 11%.The results of fixed fluidized bed experiments show that at this time,the conversion rate of heavy oil is the highest compared with the blank sample.The yield of heavy oil is reduced by 3.73 percentage points.The conversion rate is increased by 9.74 percentage points.The gasoline yield is increased by 8.18 percentage points.The dry gas yield is decreased by 1.06 percentage points.The coke yield decreased by 0.85 percentage points.The conversion depth of heavy oil was strengthened.The cracking activity and selectivity of the catalyst were improved.The product distribution became better,and the vanadium resistance became stronger.