阅读说明：本技术 一种丙烯气相直接环氧化法制备环氧丙烷的反应工艺 (Reaction process for preparing epoxypropane by propylene gas-phase direct epoxidation method ) 是由 周兴贵 张志华 陆梦科 宋楠 段学志 于 2021-09-26 设计创作，主要内容包括：本发明提供了一种丙烯气相直接环氧化法制环氧丙烷的反应工艺,包括丙烯、氢气、氧气及致稳气预混合形成原料气以及所述原料气在反应器中进行环氧化反应两个步骤。其中：在预混合过程确保无爆炸危险的前提下,使用了经济性高的丙烯、氢气和氧气摩尔配比；在反应过程中通过控制反应温度、压力和空速,在反应器出口得到产物环氧丙烷。本发明能够显著提高氧气在丙烯、氢气、氧气及致稳气形成的混合气中的爆炸极限,并且能够在预混合过程中避免爆炸危险的前提下使用经济性高的丙烯、氢气和氧气摩尔配比,在安全操作的条件下提高了反应性能,得到的环氧丙烷选择性、氢气利用效率和环氧丙烷出口浓度可满足工业生产的条件。(The invention provides a reaction process for preparing propylene oxide by a propylene gas-phase direct epoxidation method, which comprises two steps of premixing propylene, hydrogen, oxygen and stabilizing gas to form feed gas and carrying out epoxidation reaction on the feed gas in a reactor. Wherein: on the premise of ensuring no explosion hazard in the premixing process, the economic propylene, hydrogen and oxygen molar ratio is used; and in the reaction process, the product propylene oxide is obtained at the outlet of the reactor by controlling the reaction temperature, the pressure and the space velocity. The invention can obviously improve the explosion limit of oxygen in the mixed gas formed by propylene, hydrogen, oxygen and stabilizing gas, can use the economic propylene, hydrogen and oxygen molar ratio on the premise of avoiding explosion danger in the premixing process, improves the reaction performance under the condition of safe operation, and can ensure that the selectivity of the obtained propylene oxide, the utilization efficiency of the hydrogen and the outlet concentration of the propylene oxide can meet the conditions of industrial production.)

1. A reaction process for preparing propylene oxide by a propylene gas-phase direct epoxidation method comprises the steps of premixing propylene, hydrogen, oxygen and stabilizing gas to form a raw material gas and introducing the raw material gas into a reactor to generate propylene oxide.

2. The reaction process of claim 1, wherein the reactor is a tubular fixed bed reactor.

3. The reaction process of claim 1, wherein the stabilizing gas is carbon dioxide (CO)₂) Methane (CH)₄) Ethane (C)₂H₆) And propane (C)₃H₈) One or a mixture of more than one of them.

4. The reaction process of claim 3, wherein the stabilizing gas is methane or propane.

5. The reaction process of claim 4, wherein the stabilizing gas is propane.

6. The reaction process of claim 3, wherein the molar ratio of propylene to hydrogen in the feed gas is 10% to 30% respectively, and the balance is oxygen and stabilizing gas; the mixed gas of propylene, hydrogen, oxygen and stabilizing gas has no explosion danger.

7. The reaction process of claim 1, wherein the reaction temperature is 80-320 ℃.

8. The reaction process of claim 1, wherein the reaction pressure is 0.05 to 2 MPa.

9. The reaction process of claim 1, wherein the space velocity is 10-50000h^-1。

10. The reaction process of claim 1, wherein the propylene oxide selectivity, hydrogen utilization efficiency, and propylene oxide outlet concentration of the reaction process are greater than 84%, 40%, and 0.7%, respectively.

Technical Field

The invention belongs to the field of chemical industry, and particularly relates to a reaction process for preparing propylene oxide by a propylene gas-phase direct epoxidation method.

Background

Propylene Oxide (PO) is an important basic chemical raw material, is mainly used for producing organic intermediates such as polyether polyol, Propylene glycol ether and the like, and is further widely applied to industries such as food, textile, chemical industry, medicine, light industry and the like. At present, the industrial production process of propylene oxide mainly comprises a chlorohydrin method, a co-oxidation method, a CHP method and an HPPO method. The propylene gas phase direct epoxidation method is a new method for producing propylene oxide, has the outstanding advantages of cheap and easily obtained raw materials, simple process, easy separation of products and the like, and is an ideal process for PO production. The current positive PO capacity is expanded dramatically, so the process has recently received unprecedented emphasis.

However, the feed gas to the propylene gas phase direct epoxidation process contains combustible gas C₃H₆And H₂And a combustion-supporting gas O₂And C is₃H₆And H₂At O₂The explosive limits in (1) are very wide (2.0% -59% and 4.0% -95%, respectively), and thus the feed gas presents an explosion hazard during premixing. To avoid explosion hazards, current research processes typically use large volumes of inert gases such as nitrogen, helium, or argon to dilute the reaction gases. Alexander Nijhuis et al in Journal of Catalysis, 338(2016), 284-294 teach that when helium is used to dilute the reaction gas, in order to avoid explosion hazard, the oxygen concentration needs to be strictly controlled in the range of 2% -10%, indicating that the inert gases helium and the combustible gas C₃H₆And H₂And combustion-supporting gas O₂O in the mixed gas of₂Has a narrow explosive limit range when O₂Above 10% or below 2% there is a risk of explosion. Mengke Lu et al in Chinese Journal of Chemical Engineering,27(2019),2968-2978 propose a combustible gas C in the gas-phase direct epoxidation of propylene to propylene oxide with nitrogen as diluent gas₃H₆And H₂And a combustion-supporting gas O₂The research result shows that the highest allowable oxygen concentration is seriously dependent on the propylene concentration, and when the propylene concentration is lower, the highest allowable oxygen concentration is sharply reduced. However, in combustible gas C₃H₆And H₂And a combustion-supporting gas O₂In the mixing and reaction process, the problem of mixing uniformity is inevitable. Therefore, this pair of C when diluted with an inert gas such as nitrogen, helium or argon₃H₆And H₂And a combustion-supporting gas O₂The safety of the reaction, i.e. the mixing of the gas mixture of the composition, poses a great challenge. Therefore, there is a strong need in the art to provide a safe and efficient reaction process for diluting C by selecting a suitable stabilizing gas₃H₆And H₂And a combustion-supporting gas O₂The composition of the mixed gas can obviously improve O₂Explosive limits in the above-mentioned mixtures, especially in C₃H₆O at a lower content₂The operation safety can be greatly improved, and the economic propylene, hydrogen and oxygen molar ratio is used on the premise of no explosion hazard, so that the reaction performance of the gas-phase direct epoxidation of the propylene is improved, and the industrial requirement is met.

Disclosure of Invention

The invention aims to provide a reaction process for preparing propylene oxide by a propylene gas-phase direct epoxidation method, which is characterized in that proper stable gas is screened, explosion limit data of mixed gas containing propylene, hydrogen, oxygen and the stable gas is obtained, the economic propylene, hydrogen and oxygen molar ratio is used under safe conditions, explosion danger is avoided, and reasonable reaction temperature, reaction pressure and space velocity are selected to ensure that the reaction performance of the propylene gas-phase direct epoxidation reaches the industrial level, namely, the PO selectivity is higher than 84%, the hydrogen utilization efficiency (namely, hydrogen efficiency) is higher than 40%, and the PO outlet concentration is higher than 0.7%.

In order to achieve the purpose, the invention adopts the following technical scheme:

a reaction process for preparing propylene oxide by a propylene gas-phase direct epoxidation method, wherein the process comprises the steps of premixing propylene, hydrogen, oxygen and stabilizing gas to form a feed gas and introducing the feed gas into a reactor to generate propylene oxide, wherein:

(1) in the premixing process, the propylene, the hydrogen, the oxygen and the stabilizing gas are introduced into a premixer, and the molar ratio of the propylene, the hydrogen, the oxygen and the stabilizing gas is controlled, so that the raw material gas formed after premixing has no explosion danger;

(2) and (2) introducing the raw material gas obtained in the step (1) into a reactor, and controlling the reaction temperature, the reaction pressure and the reaction space velocity to obtain the propylene oxide which meets the industrial requirements on PO selectivity and PO outlet concentration at the outlet of the reactor.

The invention is further configured in that the reactor is a tubular fixed bed reactor.

The invention is further configured such that the stabilizing gas is carbon dioxide (CO)₂) Methane (CH)₄) Ethane (C)₂H₆) And propane (C)₃H₈) One or a mixture of more than one of them. The ballast gas is preferably methane or propane; more preferably propane.

The invention is further set that the molar ratio of the propylene to the hydrogen in the raw material gas is respectively 10-30%, and the rest is oxygen and stabilizing gas; the mixed gas of propylene, hydrogen, oxygen and stabilizing gas has no explosion danger.

The invention is further configured such that the reaction temperature is between 80 and 320 ℃.

The invention is further set up in that the reaction pressure is between 0.05 and 2 MPa.

The invention is further set that the space velocity is 10-50000h^-1。

The invention has the beneficial effects that:

(1) the invention adopts an economic and environment-friendly propylene gas-phase direct epoxidation method to synthesize the propylene oxide.

(2) The invention can obviously improve the explosion limit of oxygen in the mixed gas formed by propylene, hydrogen, oxygen and stabilizing gas, and can use the economic propylene, hydrogen and oxygen molar ratio on the premise of avoiding explosion danger in the premixing process, thereby improving the safety of the process.

(3) Under the process conditions provided by the invention, the reaction performances of the propylene gas-phase direct epoxidation, including PO selectivity, hydrogen utilization efficiency and PO outlet concentration, can be obviously improved, and reach the level suitable for industrial production.

Drawings

FIG. 1 is a graph of the explosive limits of propylene, hydrogen, oxygen and various stabilizing gases;

FIG. 2 is a diagram of the premixing and reaction process for the vapor phase direct epoxidation of propylene.

Detailed Description

The present invention will be described in further detail with reference to examples. It is to be understood that the following examples are for illustrative purposes only and are not to be construed as limiting the scope of the present invention, and that certain insubstantial modifications and adaptations of the invention may be made by those skilled in the art based on the teachings herein.

The inventor of the present invention has conducted extensive and intensive studies to find that, in the case of a gas-phase direct epoxidation of propylene, a high molar ratio of propylene, hydrogen and oxygen is used under the precondition of ensuring no explosion hazard in the premixing process, and after the propylene, hydrogen, oxygen and stabilizing gas are uniformly mixed, the mixture is introduced into a tubular fixed bed reactor to perform epoxidation, so as to obtain industrial PO selectivity and PO outlet concentration.

The method provided by the invention comprises the steps of firstly screening stabilizing gas, and determining the highest allowable oxygen concentration under the safe condition according to the ratio of propylene to hydrogen and the type of the stabilizing gas, as shown in figure 1; then, as shown in fig. 2, selecting a higher molar ratio of propylene, hydrogen and oxygen, and uniformly mixing the selected propylene, hydrogen and oxygen with stabilizing gas in a premixer to form a reactant; and finally, introducing the reactants into a tubular fixed bed reactor, and controlling the reaction temperature, the reaction pressure and the reaction space velocity to obtain the propylene oxide which meets the industrial requirements on PO selectivity, hydrogen efficiency and PO outlet concentration at the outlet of the reactor.

Example 1

Selecting CO₂For gas stabilization, propylene, hydrogen, oxygen and CO₂The molar ratio of (A) is 10%, 10% and 70%; mixing the above-mentioned components in mole ratio₂Introducing the reactant into a premixer to form reactant, wherein the reactant gas has no explosion danger; introducing the reaction gas into a tubular fixed bed reactor, controlling the reaction temperature at 80 ℃ and the pressure at 01MPa and space velocity of 10h^-1(ii) a At the reactor outlet, the PO selectivity was 90.0%, the hydrogen efficiency was 42%, and the outlet concentration of PO was 0.95%.

Example 2

Selecting CO₂For gas stabilization, the molar ratios of propylene and hydrogen were chosen to be 20% and 20%, with the maximum safe concentration of oxygen allowed to be 21.66%, with CO at this point₂The molar ratio of (A) is 38.34%; mixing the above-mentioned components in mole ratio₂Introducing the reactant into a premixer to form reactant, wherein the reactant gas has no explosion danger; introducing the reaction gas into a tubular fixed bed reactor, controlling the reaction temperature at 210 ℃, the pressure at 0.7MPa and the space velocity at 8000h^-1(ii) a At the reactor outlet, the selectivity for PO was 92.0%, the hydrogen efficiency was 42%, and the outlet concentration of PO was 1.59%.

Example 3

Selecting CO₂For gas stabilization, the molar ratios of propylene and hydrogen were chosen to be 30% and 30%, with the maximum safe concentration of oxygen allowed to be 26.83%, and with CO at this point₂The molar ratio of (A) is 13.17%; mixing the above-mentioned components in mole ratio₂Introducing the reactant into a premixer to form reactant, wherein the reactant gas has no explosion danger; introducing the reaction gas into a tubular fixed bed reactor, controlling the reaction temperature at 320 ℃, the pressure at 1MPa and the space velocity at 10000h^-1(ii) a At the reactor outlet, the PO selectivity was 84.2%, the hydrogen efficiency was 40.5%, and the outlet concentration of PO was 2.84%.

Example 4

Selecting methane as stabilizing gas, wherein the mol ratio of propylene, hydrogen, oxygen and methane is 10%, 10% and 70%; introducing the propylene, the hydrogen, the oxygen and the methane in the molar ratio into a premixer to form reactants, wherein the reaction gas has no explosion danger; introducing the reaction gas into a tubular fixed bed reactor, controlling the reaction temperature at 120 ℃, the pressure at 0.1MPa and the space velocity at 1500h^-1(ii) a At the reactor outlet, the selectivity for PO was 95.5%, the hydrogen efficiency was 52.5%, and the outlet concentration of PO was 0.85%.

Example 5

Methane is selected as the stabilizing gas to be used,selecting the molar ratio of the propylene to the hydrogen to be 20 percent and 20 percent, wherein the maximum allowable safe concentration of the oxygen is 20.09 percent, and the molar ratio of the methane is 39.91 percent; introducing the propylene, the hydrogen, the oxygen and the methane in the molar ratio into a premixer to form reactants, wherein the reaction gas has no explosion danger; introducing the reaction gas into a tubular fixed bed reactor, controlling the reaction temperature at 230 ℃, the pressure at 0.8MPa and the space velocity at 20000h^-1(ii) a At the reactor outlet, the PO selectivity was 90.0%, the hydrogen efficiency was 42.5%, and the outlet concentration of PO was 1.87%.

Example 6

Selecting methane as stabilizing gas, selecting the mol ratio of propylene to hydrogen as 30% and 30%, wherein the maximum allowable safe concentration of oxygen is 26.13%, and the mol ratio of methane is 13.87%; introducing the propylene, the hydrogen, the oxygen and the methane in the molar ratio into a premixer to form reactants, wherein the reaction gas has no explosion danger; introducing the reaction gas into a tubular fixed bed reactor, controlling the reaction temperature at 270 ℃, the pressure at 2MPa and the space velocity at 50000h^-1At the reactor outlet, the selectivity for PO was 87.1%, the hydrogen efficiency was 41.2%, and the outlet concentration of PO was 2.42%.

Example 7

Ethane is selected as stabilizing gas, and the molar ratio of propylene, hydrogen, oxygen and ethane is 10%, 10% and 70%; introducing the propylene, the hydrogen, the oxygen and the ethane in the molar ratio into a premixer to form reactants, wherein the reaction gas has no explosion danger; introducing reaction gas into a tubular fixed bed reactor, controlling the reaction temperature at 100 ℃, the pressure at 0.1MPa and the space velocity at 1500h^-1(ii) a At the reactor outlet, the PO selectivity was 96.8%, the hydrogen efficiency was 56.2%, and the outlet concentration of PO was 0.80%.

Example 8

Ethane is selected as stabilizing gas, the molar ratio of propylene to hydrogen is selected to be 20% and 20%, the maximum allowable safe concentration of oxygen is 20.09%, and the molar ratio of ethane is 39.91%; introducing the propylene, the hydrogen, the oxygen and the ethane in the molar ratio into a premixer to form reactants, wherein the reaction gas has no explosion danger; will reactIntroducing gas into a tubular fixed bed reactor, controlling the reaction temperature at 240 ℃, the pressure at 0.5MPa and the space velocity at 20000h^-1At the reactor outlet, the selectivity for PO was 90.0%, the hydrogen efficiency was 49.1%, and the outlet concentration of PO was 1.89%.

Example 9

Selecting ethane as stabilizing gas, selecting the mol ratio of propylene to hydrogen to be 30% and 30%, wherein the maximum allowable safe concentration of oxygen is 26.13%, and the mol ratio of ethane is 13.87%; introducing the propylene, the hydrogen, the oxygen and the ethane in the molar ratio into a premixer to form reactants, wherein the reaction gas has no explosion danger; introducing the reaction gas into a tubular fixed bed reactor, controlling the reaction temperature to be 250 ℃, the pressure to be 0.05MPa and the space velocity to be 10000h^-1(ii) a At the reactor outlet, the selectivity for PO was 89.0%, the hydrogen efficiency was 49.9%, and the outlet concentration of PO was 1.65%.

Example 10

Selecting propane as stabilizing gas, wherein the molar ratio of propylene to hydrogen to oxygen to propane is 10%, 10% and 70%; introducing the propylene, the hydrogen, the oxygen and the propane in the molar ratio into a premixer to form reactants, wherein the reaction gas has no explosion danger; introducing the reaction gas into a tubular fixed bed reactor, controlling the reaction temperature at 130 ℃, the pressure at 0.1MPa and the space velocity at 1500h^-1(ii) a At the reactor outlet, the PO selectivity was 95.0%, the hydrogen efficiency was 50.5%, and the outlet concentration of PO was 0.91%.

Example 11

Selecting propane as stabilizing gas, selecting the molar ratio of propylene to hydrogen to be 20% and 20%, wherein the maximum allowable safe concentration of oxygen is 20.09%, and the molar ratio of propane is 39.91%; introducing the propylene, the hydrogen, the oxygen and the propane in the molar ratio into a premixer to form reactants, wherein the reaction gas has no explosion danger; introducing the reaction gas into a tubular fixed bed reactor, controlling the reaction temperature at 190 ℃, the pressure at 0.15MPa and the space velocity at 4000h^-1(ii) a At the reactor outlet, the PO selectivity was 94.0%, the hydrogen efficiency was 53.8%, and the outlet concentration of PO was 1.52%.

Example 12

Selecting propane as stabilizing gas, selecting the molar ratio of propylene to hydrogen to be 30% and 30%, wherein the maximum allowable safe concentration of oxygen is 26.13%, and the molar ratio of propane is 13.87%; introducing the propylene, the hydrogen, the oxygen and the propane in the molar ratio into a premixer to form reactants, wherein the reaction gas has no explosion danger; introducing the reaction gas into a tubular fixed bed reactor, controlling the reaction temperature at 260 ℃, the pressure at 0.1MPa and the space velocity at 10000h^-1(ii) a At the outlet of the reactor, the PO selectivity was 86.2%, the hydrogen efficiency was 41.8%, and the outlet concentration of PO was 2.43%

Comparative example 1

Selecting propane as stabilizing gas, wherein the molar ratio of propylene to hydrogen to oxygen to propane is 10%, 10% and 70%; introducing the propylene, the hydrogen, the oxygen and the propane in the molar ratio into a premixer to form reactants, wherein the reaction gas has no explosion danger; introducing the reaction gas into a tubular fixed bed reactor, controlling the reaction temperature at 50 ℃, the pressure at 0.1MPa and the space velocity at 1500h^-1(ii) a At the reactor outlet, the PO selectivity was 98.8%, the hydrogen efficiency was 58.9%, and the outlet concentration of PO was 0.22%. The results show that when the reaction temperature is too low, the outlet concentration of PO does not meet 0.7% of the industrial conditions. Therefore, the reaction temperature for producing propylene oxide by the vapor phase direct epoxidation of propylene is not preferably too low.

Comparative example 2

Selecting propane as stabilizing gas, selecting the molar ratio of propylene to hydrogen to be 20% and 20%, wherein the maximum allowable safe concentration of oxygen is 20.09%, and the molar ratio of propane is 39.91%; introducing the propylene, the hydrogen, the oxygen and the propane in the molar ratio into a premixer to form reactants, wherein the reaction gas has no explosion danger; introducing the reaction gas into a tubular fixed bed reactor, controlling the reaction temperature at 340 ℃, the pressure at 0.15MPa and the space velocity at 4000h^-1(ii) a At the reactor outlet, the PO selectivity was 75.1%, the hydrogen efficiency was 35.9%, and the outlet concentration of PO was 2.15%. The results show that when the reaction temperature is too high, the selectivity of PO does not meet 84% of the commercial conditions. Therefore, the reaction temperature for producing propylene oxide by the vapor phase direct epoxidation of propylene is not preferably too high.

Comparative example 3

Selecting methane as stabilizing gas, wherein the mol ratio of the propylene to the hydrogen to the oxygen to the methane is 5%, 5% and 85%; introducing the propylene, the hydrogen, the oxygen and the methane in the molar ratio into a premixer to form reactants, wherein the reaction gas has no explosion danger; introducing the reaction gas into a tubular fixed bed reactor, controlling the reaction temperature at 230 ℃, the pressure at 0.8MPa and the space velocity at 20000h^-1(ii) a At the reactor outlet, the selectivity to PO was 92.2%, the hydrogen efficiency was 46.9%, and the outlet concentration of PO was 0.52%. The results show that when the molar ratio of propylene, oxygen and oxygen is too low, the outlet concentration of PO is much lower than 0.7% of the industrial conditions. Therefore, the molar ratio of propylene, hydrogen and oxygen in the reaction of preparing propylene oxide by gas-phase direct epoxidation of propylene should not be too low.

Comparative example 4

Selecting methane as stabilizing gas, wherein the mol ratio of the propylene to the hydrogen to the oxygen to the methane is 30%, 30% and 10%; at this time, the molar ratio of oxygen is higher than the maximum safe concentration of oxygen by 26.13%, and the gas in the ratio has explosion danger in the premixing process. Therefore, the molar ratio of propylene, hydrogen and oxygen in the reaction of preparing propylene oxide by gas-phase direct epoxidation of propylene should not be too high.

Comparative example 5

Selecting methane as stabilizing gas, wherein the mol ratio of propylene, hydrogen, oxygen and methane is 10%, 10% and 70%; introducing the propylene, the hydrogen, the oxygen and the methane in the molar ratio into a premixer to form reactants, wherein the reaction gas has no explosion danger; introducing the reaction gas into a tubular fixed bed reactor, controlling the reaction temperature at 120 ℃, the pressure at 0.1MPa and the space velocity at 1h^-1(ii) a The oxygen has reacted to completion before the exit of the reactor, resulting in the catalyst in the latter reactor not being used. Therefore, the space velocity in the reaction for producing propylene oxide by the gas-phase direct epoxidation of propylene is not preferably too low.

Comparative example 6

Selecting propane as stabilizing gas, wherein the molar ratio of propylene to hydrogen to oxygen to propane is 10%, 10% and 70%; mixing the above-mentioned componentsPropylene, hydrogen, oxygen and propane are fed into a premixer to form reactants, and the reaction gas has no explosion danger; introducing the reaction gas into a tubular fixed bed reactor, controlling the reaction temperature at 120 ℃, the pressure at 0.1MPa and the space velocity at 70000h^-1(ii) a At the reactor outlet, the selectivity for PO was 98.9%, the hydrogen efficiency was 56.5%, and the outlet concentration of PO was 0.31%. The results show that the outlet concentration of PO does not meet 0.7% of the industrial conditions when the airspeed is too high. Therefore, the space velocity in the reaction for preparing propylene oxide by the gas-phase direct epoxidation of propylene is not preferably too high.

Comparative example 7

Selecting different stabilizing gases, selecting the molar ratio of the propylene to the hydrogen to be 15% and 15%, determining the maximum safe concentration of the oxygen allowed by the oxygen through figure 1, and respectively listing the maximum safe concentrations in table 1; introducing the propylene, the hydrogen, the oxygen and the stabilizing gas in the molar ratio into a premixer to form reactants, wherein the reactant gas has no explosion danger; introducing reaction gas into a tubular fixed bed reactor, controlling the reaction temperature at 210 ℃, the pressure at 0.12MPa and the space velocity at 4000h^-1(ii) a The selectivity of PO at the reactor outlet was about 90% when different stabilising gases were chosen, at which point the PO outlet concentration was higher when using propane and methane as stabilising gases, as shown in table 1. It is worth noting that H in the stabilizing gas of Table 1₂The cost of O is low. But taking into account the subsequent product separation process, H₂O is liquefied and vaporized due to H₂The latent heat of O is high, and therefore a large amount of energy is required to circulate H₂O, which makes the subsequent separation operation costly. The stabilizing gas may preferably be propane, methane, most preferably propane, according to the above analysis.

TABLE 1