Method for preparing branched-chain high-carbon oxygen-containing compound through catalytic conversion of isopropanol

Abstract

The invention belongs to the technical field of green chemistry, and discloses a method for preparing a branched-chain high-carbon oxygen-containing compound through catalytic conversion of isopropanol. A fixed bed normal-pressure reactor is selected, and under the conditions of temperature control and mass space velocity control, an isopropanol raw material is introduced into the reactor loaded with a catalyst for reaction through carrier gas. The method has the advantages of short process flow, environmental friendliness and the like, and only water is a theoretical byproduct in an ideal state. The metal-acid-base composite catalyst designed and prepared by the invention is easy to synthesize, metal atoms and oxides are in atomic-scale dispersion, and the metal-acid-base composite catalyst has the characteristics of high activity and high selectivity. The used raw material is isopropanol which can be obtained from biomass through fermentation, and the source is sufficient. When the solid metal-acid-base composite catalyst provided by the invention is used for the isopropanol coupling reaction, the product is easy to separate, the whole process has economical efficiency and practicability, the concept of sustainable development is met, and the solid metal-acid-base composite catalyst has a good industrial application prospect in the field of biomass conversion.

Description

Technical Field

[0001] The invention belongs to the technical field of green chemistry, and relates to a method for preparing branched high-carbon oxygen-containing compounds by catalytic conversion of isopropanol, and specifically to a method for preparing branched high-carbon oxygen-containing compounds by catalyzing isopropanol with a solid acid-base catalyst. Background Art

[0002] High-carbon oxygenates are important raw materials for fine chemicals and are also very attractive biofuels, especially high-carbon oxygenates with branched chains. Compared with traditional biofuel ethanol, high-carbon oxygenates have higher energy density and lower hygroscopicity as gasoline substitutes. In addition, high-carbon oxygenates with branched carbon skeletons have higher octane numbers and are ideal biofuels and oil additives in the future. At present, the industrial production of high-carbon oxygenates is mainly through carbonyl synthesis (OXO), but the reaction requires a large pressure (>20Mpa), a precious metal catalyst (Rh), and petroleum-based olefins as the main raw materials [Chemical Technology, 2020, 28(1): 59-64].

[0003] Low-carbon alcohols and ketones such as ethanol, acetone or acetone-containing liquids can be synthesized into high-carbon oxygen-containing compounds through Guerbet condensation. Ethanol has a wide range of sources and can be obtained from biomass. It is the focus of academic research. Recently, the literature reported that Ni was used to partially replace Mg in the hydrotalcite structure to obtain Ni4MgAlO catalysts for ethanol coupling to prepare high-carbon alcohols. The ethanol conversion rate was 18.7%, and the selectivity of n-butanol and C4-C8 primary alcohols was 55.2 and 85%, respectively [Journal of Catalysis 344 (2016) 184-193.]. Researchers used tin-doped cerium dioxide catalysts to achieve direct catalytic conversion of acetone-containing liquids, with a carbon conversion rate of 70% and a selectivity of the main product 4-heptanone of up to 86% [Nature Communications|(2018)9:5183.].

[0004] The products of the above two methods are mainly high-carbon alcohols and ketones with straight-chain carbon skeletons. Theoretically, 100% branched carbon skeleton products can be obtained from acetone to prepare high-carbon oxygen-containing compounds, which is conducive to improving the combustion quality. However, the equilibrium constant of the aldol condensation reaction of acetone is less than 1.0, and the conversion rate of the reaction is limited. H2 needs to be added to saturate the C=C bond of the intermediate, break the reaction equilibrium limit, and drive the reaction equilibrium to C 6+ The product was processed [ChemSusChem, 2016, 9, 3382-3386.].

[0005] With the continuous advancement of fermentation engineering technology, isopropanol produced by fermentation using biomass raw materials such as straw has been regarded as a potential biomass-based platform chemical [Bioresource Technology 396 (2024) 130416.], but the technical maturity of this fermentation production method still needs to be further improved. At present, the leading production technologies on the market include propylene direct hydration, acetone hydrogenation process, and isopropyl acetate hydrogenation process. Since my country's isopropanol industry is facing serious overcapacity problems and market supply far exceeds demand, exploring and expanding new application areas of isopropanol is of great significance to promoting the sustainable development of the isopropanol industry. At present, the existing catalytic system for preparing high-carbon oxygen-containing compounds from isopropanol is molybdenum carbide, but the synthesis of the catalyst is complex, the selectivity of the reaction is less than 60%, and the reaction uses a kettle reactor, which requires high pressure and is difficult to produce on a large scale [Green Chem., 2022, 24, 5083]. Summary of the invention

[0006] The purpose of the present invention is to provide a method for preparing branched high-carbon oxygen-containing compounds based on isopropanol for the deficiencies in the current technology. The method is carried out under normal pressure with isopropanol as raw material, has the advantages of short process flow, clean reaction process (theoretically, byproduct has only water), is a green process route, compared with other low-carbon oxygen-containing compounds, isopropanol carries out hydrogen transfer reaction on the catalyst surface by hydrogen generated in situ, does not need to add extra H2, and in the reaction product, high-carbon alcohol ketone is all branched carbon skeleton high-carbon oxygen-containing compounds. The present invention also designs a mixed oxide catalyst for isopropanol catalytic reaction, obtains a cobalt-containing composite metal oxide catalyst by coprecipitation, and has the characteristics of high activity and high selectivity compared with the magnesium-aluminum mixed oxide derived from commercial magnesium-aluminum hydrotalcite.

[0007] The technical solution of the present invention is:

[0008] A method for preparing branched high-carbon oxygen-containing compounds by catalytic conversion of isopropanol comprises the following steps:

[0009] A fixed bed atmospheric pressure reactor is selected, the reaction temperature is 150-350°C, preferably 250-325°C; the mass space velocity is 0.5-7.3h -1 , preferably 1.45~3.63h -1 Specifically, the mass space velocity refers to the ratio of the mass flow rate of isopropanol to the amount of catalyst loaded. The isopropanol raw material is introduced into the reactor loaded with the catalyst through a carrier gas, the isopropanol pressure is 1-10 kPa, and the reaction gas flow rate is 20-200 mL / min; the carrier gas is nitrogen, argon, helium or other inert atmospheres.

[0010] The catalyst is a mixed metal oxide based on a hydrotalcite precursor. The catalyst is composed of magnesium, aluminum, oxygen, and at least one element of cobalt, zinc, and copper. The oxygen content is determined by the oxygen value of each metal oxide in the composition.

[0011] Furthermore, in the catalyst, the molar ratio of trivalent ions to divalent ions is 3:1, the trivalent ions provided are aluminum, and the divalent ions provided are one of magnesium, cobalt, zinc, and copper, the mass fractions of magnesium, aluminum, and oxygen in the catalyst are 25-45wt%, 10-20wt%, and 35-45wt%, respectively, and the mass fractions of transition metal additives cobalt, zinc, and copper are 0.4-45wt%. The sum of the mass percentages of all metal elements and oxygen elements in the catalyst is 100wt%.

[0012] Furthermore, the catalyst is obtained by co-precipitation, and the precipitant used in the co-precipitation method is at least two of sodium carbonate, sodium hydroxide, potassium carbonate, and potassium hydroxide. The precipitant adjusts the final solution pH to 8-11, the aging temperature is 35-65°C, and the aging time is 2-18 hours.

[0013] Further, after the catalyst is aged, it is filtered, washed, dried, and calcined to obtain the desired catalyst. The calcination temperature is 300-600° C., the calcination time is 0.5-4 hours, and the calcined catalyst is named X according to the molar ratio of metal ions n(X):n(Mg):Al=n:3-n:1. n Mg 3-n AlO m (0.01≤n≤0.72), X=one or more elements selected from cobalt, zinc and copper.

[0014] Beneficial effects of the present invention:

[0015] (1) The present invention has the advantages of short process flow and environmental friendliness, especially under ideal conditions, the only theoretical byproduct of the process is water;

[0016] (2) The metal-acid-base composite catalyst designed and prepared by the present invention is easy to synthesize, the metal atoms and the oxide atoms are dispersed at the atomic level, and it has the characteristics of high activity and high selectivity. The raw material used is isopropanol, which can be obtained by fermentation of biomass and has an abundant source. At 275°C and normal pressure, the conversion rate of isopropanol is 43.7%, C 6-12 The selectivity of oxygen-containing compounds reached 70.3%, all of which were branched oxygen-containing compounds.

[0017] (3) When the solid metal-acid-base composite catalyst provided by the present invention is used for the isopropanol coupling reaction, the product is easy to separate, and the whole process is both economical and practical, which conforms to the concept of sustainable development and has good industrial application prospects in the field of biomass conversion. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is the Co with different cobalt contents in Example 1 n Mg 3-n AlO x XRD pattern of .

[0019] Figure 2 is Co in Example 1 0.24 Mg 2.76 AlO x Spherical aberration electron microscope images. (a, b) are Co 0.24 Mg 2.76 AlO x High-angle annular dark-field scanning transmission electron microscopy images of Co 0.24 Mg 2.76 AlO x Intensity distribution diagram of regions 1 and 2; (e) is Co 0.24 Mg 2.76 AlO x EDS element spectrum; (fi) element distribution diagrams corresponding to aluminum, cobalt, magnesium and oxygen respectively. DETAILED DESCRIPTION

[0020] The specific implementation of the present invention is further described below in conjunction with the accompanying drawings and technical solutions.

[0021] Before the experiment, 100 mg of the catalyst was loaded into the reactor and pretreated at 673 K for 2 h in a N2 atmosphere. After the pretreatment, it was cooled to 373 K in a N2 atmosphere. Subsequently, the isopropanol reactant was introduced into the reactor by bubbling with nitrogen as a carrier. The liquid product was separated by a FFAP capillary column (30 m × 0.32 mm × 0.5 μm) and collected in an ice-water bath at 273 K. The gaseous product was detected by a thermal conductivity detector (TCD) and separated by GDX-102 and 5A molecular sieves. The liquid product was qualitatively analyzed using an HP-FFAP capillary column (30 m × 0.32 mm × 0.25 μm) in conjunction with an Agilent 7890 / 5975C gas chromatograph-mass spectrometer.

[0022] The isopropanol conversion rate and product selectivity were calculated by normalization method based on the molar number of carbon in the product.

[0023] Isopropanol conversion rate:

[0024]

[0025] Product selectivity

[0026]

[0027] ni Indicates the number of carbon atoms in the reactants or products;

[0028] A i represents the peak area of ​​product i obtained by integration in the chromatogram;

[0029] f i represents the relative molar correction factor.

[0030] Example 1

[0031] Co 0.08 Mg 2.99 AlO x Taking the preparation of catalyst as an example, the preparation process is as follows:

[0032] (1) Weigh 0.349 g Co(NO3)2·6H2O, 11.231 g Mg(NO3)2·6H2O and 5.63 g Al(NO3)3·9H2O and dissolve them in 50 mL deionized water and stir well;

[0033] (2) Weigh 4.24 g of Na2CO3 and 3.60 g of NaOH and dissolve them in 60 mL of ionized water to prepare a mixed alkaline solution;

[0034] (3) pouring the mixed metal salt solution into the mixed alkali solution along a glass rod, adjusting the pH value with 3 mol / L NaOH solution under stirring in a 65°C water bath to 10, and aging at this pH and temperature for 18 h;

[0035] (4) The suspension after aging is filtered to obtain a precipitate, which is washed to neutrality and then placed in an oven at 50° C. to dry for 12 h;

[0036] (5) calcined at 600°C in air atmosphere for 2 h; finally, the calcined sample was treated at 350°C in nitrogen atmosphere for 2 h, denoted as Co 0.08 Mg 2.99 AlO x .

[0037] (6) By changing the contents of cobalt nitrate and magnesium nitrate in step (1), the ratio of n(Co):n(Mg):Al changes accordingly. The preparation method is the same as the above steps, corresponding to numbers 1-5 in Table 1.

[0038] The preparation conditions and processes of other catalysts are the same as those in Example 1. The corresponding relationship between the sample numbers and the preparation conditions is shown in Table 1.

[0039] Table 1 Correspondence between sample numbers and preparation conditions of Example 1

[0040]

[0041] Example 2

[0042] Different Co n Mg 3-n AlO x The catalyst catalyzes the coupling of isopropanol to prepare branched high-carbon oxygen-containing compounds.

[0043] The isopropanol coupling reaction was carried out in a fixed bed reactor using isopropanol as the raw material. The reaction conditions are as follows: the catalyst is loaded in a fixed bed reactor with an inner diameter of 8 mm, the reaction temperature is 275°C, and the isopropanol is introduced into the reactor by nitrogen bubbling, wherein the isopropanol partial pressure is 6.02 kPa, and the mass space velocity is 2.18 h -1 The total flow rate of the reaction gas was 30 mL / min. After the reaction was stable, the liquid product was collected by a 0°C cold trap for analysis. The conversion rate of isopropanol and the selectivity of the product were calculated by the normalization method. The results are shown in Table 2.

[0044] Table 2 Isopropanol activity and C of different catalysts 6-12 Corresponding relationship of selectivity of branched high carbon oxygen-containing compounds

[0045]

[0046]

[0047] Comparative Example 1

[0048] No transition metal was added during the preparation of the mixed metal oxide catalyst. Magnesium nitrate and aluminum nitrate were weighed in a ratio of n(Mg):n(Al)=3:1. The catalyst was named Mg3AlO x , the loading amount of transition metal is 0wt%. The rest of the preparation process is the same as that of Example 1.

[0049] The catalyst was used for the coupling reaction of isopropanol to C 6-12 Branched oxygen-containing compounds. Reaction conditions: atmospheric pressure, reaction temperature of 275°C, isopropanol is introduced into the reactor by nitrogen bubbling, where the isopropanol partial pressure is 6.02 kPa, and the mass space velocity is 2.18 h -1 . Isopropanol conversion rate 2.5%, C 6-12 The selectivity of branched oxygen-containing compounds is 34%.

[0050] Comparative Example 2

[0051] Sn / CeO2 was selected as the catalyst, and the loading amount of Sn was 1wt%

[0052] The catalyst was used for the coupling reaction of isopropanol to C 6-12Branched oxygen-containing compounds. Reaction conditions: atmospheric pressure, reaction temperature of 275°C, isopropanol is introduced into the reactor by nitrogen bubbling, where the isopropanol partial pressure is 6.02 kPa, and the mass space velocity is 2.18 h -1 Isopropanol conversion rate 7.9%, C 6-12 The selectivity of higher alcohols is 0.2%.

[0053] Comparative Example 3

[0054] MgO is selected as catalyst

[0055] The catalyst was used for the coupling reaction of isopropanol to C 6-12 Branched oxygen-containing compounds. Reaction conditions: atmospheric pressure, reaction temperature of 275°C, isopropanol is introduced into the reactor by nitrogen bubbling, where the isopropanol partial pressure is 6.02 kPa, and the mass space velocity is 2.18 h -1 Isopropanol conversion rate 0.6%, C 6-12 The selectivity of higher alcohols is 0.1%.

[0056] Example 3

[0057] Different active components are added to the hydrotalcite precursor, and the preparation method is the same as that in Example 1. The catalyst is used to catalyze the coupling of isopropanol to prepare branched high-carbon oxygen-containing compounds.

[0058] The isopropanol coupling reaction was carried out in a fixed bed reactor using isopropanol as the raw material. The reaction conditions are as follows: the catalyst is loaded in a fixed bed reactor with an inner diameter of 8 mm, the reaction temperature is 275°C, and the isopropanol is introduced into the reactor by nitrogen bubbling, wherein the isopropanol partial pressure is 6.02 kPa, and the mass space velocity is 2.18 h -1 The total flow rate of the reaction gas was 30 mL / min. After the reaction was stable, the liquid product was collected by a 0°C cold trap for analysis. The conversion rate of isopropanol and the selectivity of the product were calculated by the normalization method. The results are shown in Table 3.

[0059] Table 3 Isopropanol activity and C of transition metal catalysts 6-12 Corresponding relationship of selectivity of branched high carbon oxygen-containing compounds

[0060]

[0061] Example 4

[0062] In Example 1, Co 0.24 Mg 2.76 AlO x The catalyst catalyzes the coupling of isopropanol to produce high-carbon oxygen-containing compounds.

[0063] Using isopropanol as raw material, the reaction of isopropanol to branched high-carbon oxygen-containing compounds was carried out in a fixed bed reactor. The reaction conditions are as follows: the catalyst is loaded in a fixed bed reactor with an inner diameter of 8 mm, normal pressure, reaction temperature 250-325℃, mass space velocity 2.18h -1 After the reaction stabilized, the liquid product was collected and analyzed by chromatography. The conversion rate of isopropanol and the selectivity of the product were calculated by normalization method. The results are shown in Table 4.

[0064] Table 4 Co in Example 1 at different reaction temperatures 0.24 Mg 2.76 AlO x Catalytic activity of the catalyst for isopropanol and selectivity for branched high-carbon oxygenated compounds

[0065]

[0066] As the reaction temperature increases, Co 0.24 Mg 2.76 AlO x The conversion rate of isopropanol on the catalyst gradually increased, the selectivity of branched alcohols decreased, and the selectivity of branched ketones increased.

[0067] Example 5

[0068] At different mass space velocities, Co in Example 1 0.24 Mg 2.76 AlO x The catalyst catalyzes the coupling of isopropanol to produce branched high-carbon oxygen-containing compounds.

[0069] The isopropanol coupling reaction was carried out in a fixed bed reactor using isopropanol as the raw material. The reaction conditions are as follows: the catalyst is loaded in a fixed bed reactor with an inner diameter of 8 mm, the reaction temperature is 275°C, and the isopropanol is introduced into the reactor by nitrogen bubbling, wherein the isopropanol partial pressure is 6.02 kPa, and the mass space velocity is 1.45-7.3 h -1 After the reaction stabilized, the liquid product was collected for the first 2 hours of the reaction and analyzed by chromatography. The conversion rate of isopropanol and the selectivity of the product were calculated by normalization method. The results are shown in Table 5.

[0070] Table 5 Co in Example 1 at different mass space velocities 0.24 Mg 2.76 AlO x Catalytic activity of the catalyst for isopropanol and selectivity for branched high-carbon oxygenated compounds

[0071]

[0072] At 275°C, the mass space velocity is 1.5 h -1 The conversion rate of isopropanol was 70.8%, C 6-12The selectivity of branched high-carbon oxygen-containing compounds is the highest, at 76.0%.

[0073] Example 6

[0074] Preparation of branched high-carbon oxygen-containing compounds by coupling of isopropanol under different carrier gas atmospheres.

[0075] Using Co in Example 1 0.24 Mg 2.76 AlO x Catalyst, atmospheric pressure, reaction temperature of 275°C, isopropanol was introduced into the reactor by hydrogen bubbling, wherein the isopropanol partial pressure was 6.02 kPa, the hydrogen partial pressure was 94 kPa, and the mass space velocity was 2.18 h -1 Isopropanol conversion rate 42.4%, C 6-12 The selectivity of branched oxygen-containing compounds is 69.3%. When the reaction atmosphere is hydrogen, the conversion rate of isopropanol and the selectivity of high-carbon oxygen-containing compounds are not significantly different from those when the reaction atmosphere is nitrogen, which indicates that isopropanol undergoes hydrogen transfer reaction on the catalyst surface through hydrogen generated in situ.

[0076] Example 7

[0077] Co 0.24 Mg 2.76 AlO x Catalytic preparation of branched high-carbon oxygen-containing compounds from different raw materials

[0078] Using Co in Example 1 0.24 Mg 2.76 AlO x Catalyst, atmospheric pressure, reaction temperature of 275°C, raw materials were brought into the reactor by nitrogen bubbling, where the raw gas partial pressure was 6.02 kPa, the hydrogen partial pressure was 94 kPa, and the mass space velocity was 2.18 h -1 After the reaction stabilized, the liquid product was collected for 1 hour before the reaction and analyzed by chromatography. The conversion rate of isopropanol and the selectivity of the product were calculated by normalization method. The results are shown in Table 6.

[0079] Table 6 Preparation of high carbon oxygen-containing compounds from different raw materials

[0080]

[0081] Example 8

[0082] Co-feeding experiment of isopropanol and intermediate product acetone.

[0083] Using Co in Example 1 0.24 Mg 2.76 AlO xCatalyst, atmospheric pressure, reaction temperature of 275°C, isopropanol was introduced into the reactor by nitrogen bubbling, wherein the isopropanol partial pressure was 4.02 kPa, the acetone partial pressure was 2 kPa, the nitrogen partial pressure was 94 kPa, and the mass space velocity was 2.18 h -1 Isopropanol conversion rate 49.9%, C 6-12 The selectivity of branched oxygenates was 73.5%. The addition of acetone resulted in C 6-12 The selectivity of higher-carbon oxygenates increased, indicating that acetone is a key reaction intermediate during the conversion of isopropanol.

[0084] Example 9

[0085] Co 0.24 Mg 2.76 AlO x Stability test experiment of catalytic isopropanol to produce branched high-carbon oxygen-containing compounds.

[0086] Using isopropanol as raw material, the reaction of isopropanol to branched high-carbon oxygen-containing compounds was carried out in a fixed bed reactor. The reaction conditions are as follows: the catalyst is loaded in a fixed bed reactor with an inner diameter of 8 mm, normal pressure, reaction temperature is 275°C, isopropanol is brought into the reactor by nitrogen bubbling, wherein the isopropanol partial pressure is 6.02 kPa, and the mass space velocity is 2.18 h -1 After the reaction stabilized, the liquid product was collected every 1 h, and the reaction raw materials and products were analyzed by online chromatography. The change of conversion rate and selectivity within the reaction time of 12 h is shown in Table 7.

[0087] Table 7 Co in Example 1 at different mass space velocities 0.24 Mg 2.76 AlO x Catalytic activity of the catalyst for isopropanol and selectivity for branched high-carbon oxygenated compounds

[0088] Reaction time / h Isopropanol conversion rate / % <![CDATA[C 6-12 Selectivity / %]]> 1 45.7 69.8 2 37.7 66.3 3 37.1 65.5 4 36.0 65.6 5 36.6 67.6 6 34.6 63.5 7 33.6 62.6 8 32.9 64.0 9 33.3 63.4 10 31.6 62.4 11 31.9 60.9 12 31.0 62.1

[0089] As the reaction time increases, the conversion of isopropanol decreases first and then gradually stabilizes. The selectivity of branched high-carbon compounds decreases first and then gradually stabilizes.

[0090] The above descriptions are only individual embodiments of the present invention and are not intended to limit the present invention. Any modifications, substitutions and modifications made within the scope of the patent application of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing branched high-carbon oxygen-containing compounds by catalytic conversion of isopropanol, characterized in that: The following steps are involved: Use fixed bed atmospheric pressure reactor, reaction temperature 150~350℃; mass space velocity 0.5~7.3h -1 ; The isopropanol raw material is introduced into the reactor containing the catalyst through a carrier gas, the isopropanol pressure is 1 to 10 kPa, and the reaction gas flow rate is 20 to 200 mL / min.

2. The method according to claim 1, characterized in that The catalyst is a mixed metal oxide based on a hydrotalcite precursor, which is composed of magnesium, aluminum, oxygen, and at least one element of cobalt, zinc, and copper. The oxygen content is determined by the oxygen value of each metal oxide in the composition.

3. The method according to claim 2, characterized in that In the catalyst, the molar ratio of trivalent ions to divalent ions is 3:1, the trivalent ions provided are aluminum, and the divalent ions provided are one of magnesium, cobalt, zinc, and copper. The mass fractions of magnesium, aluminum, and oxygen in the catalyst are 25-45wt%, 10-20wt%, and 35-45wt%, respectively, and the mass fractions of cobalt, zinc, and copper are all 0.4-45wt%. The sum of the mass percentages of all metal elements and oxygen elements in the catalyst is 100wt%.

4. The method according to claim 2 or 3, characterized in that: The catalyst is prepared by a coprecipitation method. The precipitant used in the coprecipitation method is at least two of sodium carbonate, sodium hydroxide, potassium carbonate and potassium hydroxide. The precipitant is used to adjust the pH of the final solution to 8-11, the aging temperature is 35-65°C, and the aging time is 2-18 hours.

5. The method according to claim 2 or 3, characterized in that: After the catalyst is aged, it is filtered, washed, dried and calcined to obtain the desired catalyst. The calcination temperature is 300-600°C and the calcination time is 0.5-4 hours. According to the molar ratio of metal ions n(X):n(Mg):Al=n:3-n:1, the calcined catalyst is named X n Mg 3-n AlO m , 0.01≤n≤0.72, X=one or more elements selected from cobalt, zinc and copper.

6. The method according to claim 1, characterized in that The carrier gas is nitrogen, argon, helium or other inert atmospheres.

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