US 11,634,326 B2 · Separation and concentration of nitrate from aqueous solutions and gaseous streams

Abstract

A process for recovering nitric acid or salts thereof, comprising: contacting, in the presence of water, an water-immiscible ionic liquid of the formula [A+][X−], wherein [A+] represents a phosphonium or ammonium cation and [X−] represents a counter anion which is NO3−, an halide anion displaceable by NO3−, or both, with a fluid which contains HNO3 and at least one more mineral acid, or precursors of said acids, and partition, under mixing, said acids between aqueous and organic phases and form nitrate-loaded ionic liquid of the formula [A+][NO3−]z>0.25 where Z indicates a molar amount of nitrate held in the ionic liquid beyond the positions occupied by the nitrate counter ions; separating the so-formed mixture into an organic phase comprising a nitrate-loaded ionic liquid of the formula [A+][NO3−]z>0.25 and an aqueous phase consisting of a nitrate-depleted aqueous solution that contains the other mineral acid(s); stripping the nitric acid from said nitrate-loaded ionic liquid to create an aqueous nitrate solution and regenerate ionic liquid of the formula [A+][NO3−]z≥0 with reduced nitrate loading, or unloaded [A+][NO3−]z=0 ionic liquid.

Claims18

Dependent claims

A process for recovering nitric acid or salts thereof, comprising:

contacting, in the presence of water, an water-immiscible ionic liquid of the formula [A+][X−], wherein the ionic liquid [A+][X−] with which the process begins is [R1R2R3R4P+][X−] wherein R1, R2, R3 and R4 are the same or different and wherein at least two of R1, R2, R3 and R4 are C5-C15 alkyl groups and [X−] is chloride, bromide or nitrate, with a fluid which contains HNO3 and at least one more mineral acid, or precursors of said acids, and partition, under mixing, said acids between aqueous and organic phases and form nitrate-loaded ionic liquid of the formula [A+][NO3−]z>0.25 where Z indicates a molar amount of nitrate held in the ionic liquid beyond the positions occupied by the nitrate counter ions;
separating the so-formed mixture into an organic phase comprising a nitrate-loaded ionic liquid of the formula [A+][NO3−]z>0.25 and an aqueous phase consisting of a nitrate-depleted aqueous solution that contains the other mineral acid(s);
stripping the nitric acid from said nitrate-loaded ionic liquid to create an aqueous nitrate solution and regenerate ionic liquid of the formula [A+][NO3−]z≥0 with reduced nitrate loading, or unloaded [A+][NO3−]z=0 ionic liquid.

A process for producing nitric acid or salts thereof by removing NOx from a flue gas, said process comprising the steps of:

passing an oxidized flue gas stream that contains NO2 and SO2 through a gas-liquid contactor, where the flue gas is brought into intimate contact with an water-immiscible ionic liquid of the formula [A+][X−], wherein [A+] represents a phosphonium or ammonium cation and [X−] represents a counter anion which is NO3−, an halide anion displaceable by NO3−, or both, in the presence of an aqueous oxidizer, and form nitrate-loaded ionic liquid of the formula [A+][NO3−]z>0.25 where Z indicates a molar amount of nitrate held in the ionic liquid beyond the positions occupied by the nitrate counter ions;
releasing a purified flue gas into the atmosphere;
withdrawing ionic liquid-containing stream from the gas-liquid contactor and feeding regenerated ionic liquid stream back into the gas-liquid contactor through a circulation loop, wherein the ionic liquid-containing stream flows through said circulation loop where it is subjected to regeneration treatment comprising the steps of:
separating the ionic liquid-containing stream, optionally after addition of water, into a first organic stream consisting essentially of H2SO4-free and HX-free ionic liquid [A+][NO3−]z>0.25 and a first aqueous acidic stream which contains H2SO4 and optionally HX, wherein X is halide;
stripping the nitrate from the organic stream consisting of the ionic liquid [A+][NO3−]z>0.25 to create a second aqueous stream which contains HNO3 or salt thereof;
and regenerating ionic liquid of the formula [A+][NO3−]z≥0 with reduced nitrate loading or unloaded [A+][NO3−]z=0 ionic liquid;
leading said [A+][NO3−]z≥0 with reduced Z value back to the gas-liquid contactor;
and
recovering H2SO4 solution from said first aqueous acidic stream and optionally HX solution, wherein X is halide, or salts thereof, and from the second aqueous stream a nitrate salt or nitric acid solution.

6 more elements

Dependencies are inferred from the claim text.

Separation and concentration of nitrate from aqueous solutions and gaseous streams

Life of this patent

Separation and concentration of nitrate from aqueous solutions and gaseous streams

Life of this patent

Abstract

Claims18