CO Copper-based Shift Catalyst PH₃Poisoning Mechanism

Blast furnace ironmaking enriched oxygen gas by the water gas shift system to take the ammonia synthesis feed gas, coal consumption can eliminating the need for synthetic ammonia, while reducing the CO2emissions of the steel and synthetic ammonia industry, to achieve the iron industry, and synthetic ammonia industry joint purpose of energy saving.Against oxygen-enriched blast furnace gas PH3resulting copper-based the conversion catalyst poisoning problem, the system of the catalyst in the oxygen-enriched blast furnace gas atmosphere under optimum reaction conditions, catalyst poisoning mechanism under different conditions of PH3and poisoning characterized in, and poisoning of the catalyst after regeneration. The main conclusions are as follows:(1) According to the actual situation of copper-based low-temperature shift catalyst prepared in oxygen-enriched blast furnace gas atmosphere of ammonia synthesis gas experiments to determine the temperature of steam and gas to transform the main factors of the experiment. The were investigated temperature of160to260℃, steam and gas within the range of0.3to0.7on the conversion rate of the low-temperature shift catalyst law. In the case of holding experiments, other conditions are not changed except temperature transformation in the temperature range of160to190℃. The activity of the catalyst gradually increased as the temperature rises, when the temperature reaches190℃to transform the transformation of a catalyst rate reaches a peak, the description of the copper-based shift catalyst activity of the catalyst in its active temperature range, there is an optimum temperature, but started to decline when the temperature exceeds190℃when the conversion ratio of the copper-based shift catalysts described copper-based shift catalysts transform temperature exceeds the optimum temperature, the catalyst may occur side reactions such as sintering; while maintaining the experiment except the case of steam and gas other than the outer conditions are not changed, within the scope of the copper-based catalyst for the vapor-gas ratio, the active gradually increases with the increase of the ratio of steam and gas, steam and gas0.6catalyst conversion rate maximum, and when the steam and gas continues to increase conversion rates have declined, which indicates that the steam and gas than in the past The high also affect the normal use of the catalyst.(2) in the blast furnace gas atmosphere poisoned by carbon monoxide shift catalyst PH3thermodynamic analysis can be drawn:①Copper-based low-temperature shift catalyst the catalyst easily with PH3poisoning reaction in the presence of oxygen, and oxygen also copper-based catalyst copper oxide and cuprous oxide passivation reaction occurs. Therefore, to minimize the oxygen content is the key point to prevent the copper-based catalyst poisoning in the blast furnace gas atmosphere PH3.②The copper converting catalyst active center of Cu covered PH3reaction oxides and carbon easy clogging the pores of the catalyst surface of the catalyst cause temporary poisoning; the generated CuP2with Cu (H2PO4)2will occupy the center of activity of the catalyst, resulting in permanent poisoning of the catalyst.③Copper-based shift catalyst in terms of the above-mentioned what kind of atmosphere the activity changes as the temperature changes are not large, with the experimental literature mentioned different calcination temperature Cu grain grew up in different degrees, but did not show The apparent inactivation conclusion pertinence.(3) Experimental changed by a single factor analysis method for copper-based CO low temperature shift catalyst deactivation process, inactivation behavior was studied, the following conclusions can be drawn through the experimental results:①Under the same experimental conditions, the catalyst of the The larger the particle size that is the specific surface area is smaller, the catalyst in the presence of gas in the case of the conversion ratio from the volatility reach the stable value, the shorter the time, and to achieve more stable conversion rate and the initial conversion rate also decreased Multi.②Under the same experimental conditions, the catalyst under the conditions of low concentration of PH3, the poisoning of the catalyst after the conversion rate into the fluctuations in its conversion rate reached stable when compared to the conversion rate and the initial conversion rate decreased much, the low concentration of the gas just the catalyst temporary toxic reactions.More volatile catalyst under the conditions of high concentrations of PH3and to stabilize the conversion rate and the initial conversion rate fell more than high concentrations of toxic gases causes the catalyst to cause permanent inactivation.③In the atmosphere of oxygen-enriched blast furnace gas shift catalyst in the presence of CO2in the atmosphere conversion rate suddenly dropped fluctuations stabilized and then decline as compared to the initial activity; did not have any impact on the conversion rate of the catalyst in the presence of N2conditions.(4) The use of XPS, XRD, SEM and other characterization means PH3poisoning of the catalyst sample under different conditions, analysis of the fresh catalyst, the reduction of samples, as well as under different conditions PH3poisoning of the catalyst surface composition, structure, shape, etc. changes, combined with the experimental results and thermodynamic calculations, analysis of the causes and mechanism of copper-based catalyst PH3poisoning. Combined with thermodynamic calculations comprehensive analysis of the data and poisoning experiments PH3poisoning mechanism of the shift catalyst:phosphide will invade the catalytic active center and active substances (copper microcrystalline) react to the active center of the catalyst reactants occupied, resulting in its internal changes in the structure, and these reactants is difficult by a general method will be removed, thus resulting in a catalyst temporary or permanent deactivation caused by the irreversible poisoning or permanent poisoning. The reduction of the activity of the catalyst in addition to poison poisoned, carbon so that it is also one of the reasons for the decline of activity, coke clog the catalyst active center of the gap, hinder the contact of the reactants with the catalyst, so that the decreased activity.(5) will be part of the poisoning, and mandatory poisoning the catalyst after the activity recovery experiments combined with the the thermodynamics calculation results can be drawn:①For the partial poisoning the catalyst activity center may only occur with a small amount of toxicant in the oxidation reaction, or simply coke coverage, resulting in a temporary deactivation. Pass into the raw gas in the process of recovery of activity, the activity center comprising CO, carbon is CO gas flow away, and the active centers react oxide by reduction of CO to play a catalytic activity of the catalyst to restore the initial state.②while catalyst for mandatory poisoning, active centers of the catalyst may have a large area of the occurrence of the reaction, resulting in a permanent deactivation of the catalyst.