USRE38532EExpiredUtilityPatentIndex 62

Hydrodealkylation processes

Assignee: CHEVRON PHILLIPS CHEMICAL COPriority: Jan 4, 1993Filed: Dec 6, 1999Granted: Jun 8, 2004

Est. expiryJan 4, 2013(expired)· nominal 20-yr term from priority

Inventors:HEYSE JOHN V MULASKEY BERNARD F INNES ROBERT A HAGEWIESCHE DANIEL P CANNELLA WILLIAM J KRAMER DAVID C

C07C 4/16C07C 4/08C10G 75/00C07C 4/04B01J 2219/024C07C 2/64C07C 2/00B01J 2219/0286B01J 2219/0236B01J 19/02C07C 2/864B01J 19/0026C07C 5/327C07C 6/123C07C 5/48

PatentIndex Score

Cited by

163

References

151

Claims

Abstract

Carburization and metal-dusting while hydrodealkylating a hydrodealkylatable hydrocarbon are reduced even in the substantial absence of added sulfur.

Claims

exact text as granted — not AI-modified

What is claimed is:

1. A method for hydrodealkylating a hydrodealkylatable hydrocarbon comprising (i) treating at least a portion of a hydrodealkylation reactor system with a carburization resistant composition, and (ii) contacting said hydrocarbon in said treated reactor system with hydrogen under low sulfur hydrodealkylation conditions of 100 ppm or less and wherein said carburization resistant composition comprises, in major proportion, a member selected from the group consisting of aluminum, antimony, arsenic, bismuth, brass, gallium, germanium, indium, lead, selenium, tellurium, tin or intermetallic compounds and alloys thereof.

2. The method for hydrodealkylating a hydrodealkylatable hydrocarbon according to claim 1 , wherein treating step (i) comprises applying a coating or film of a carburization resistant composition to a surface of the reactor system susceptible to carburization under hydrodealkylation conditions.

3. The method for hydrodealkylating a hydrodealkylatable hydrocarbon according to claim 2 , wherein said carburization resistant composition comprises a member selected from the group consisting of aluminum, antimony, arsenic, bismuth, brass, chromium, copper, germanium, indium, lead, selenium, tellurium, tin or intermetallic compounds and alloys thereof.

4. The method for hydrodealkylating a hydrodealkylatable hydrocarbon according to claim 3 1 , wherein at least a portion of said coating or film is a Cu—Sn alloy or a Cu—Sb alloy.

5. The method for hydrodealkylating a hydrodealkylatable hydrocarbon according to claim 2 , wherein said coating or film is provided as a plating, cladding, paint or other coating, to a base construction material.

6. The method for hydrodealkylating a hydrodealkylatable hydrocarbon according to claim 1 , wherein said carburization resistant composition contains tin.

7. A method for hydrodealkylating a hydrodealkylatable hydrocarbon according to claim 1 , comprising adding an anti-carburizing and anti-coking agent selected from the group of organo-tin compounds, organo-antimony compounds, organo-bismuth compounds, organo-arsenic compounds and organo-lead compounds to the hydrocarbon.

8. The method for hydrodealkylating a hydrodealkylatable hydrocarbon according to claim 1 , wherein an organo-tin non-sulfur, anti-carburizing and anti-coking agent is added to the hydrocarbon.

9. The method for hydrodealkylating a hydrodealkylatable hydrocarbon according to claim 1 , wherein at least a portion of said reactor system is constructed from a nickel containing stainless steel having sufficient chromium content so that an intermediate layer comprising chromium and carbide between the steel and an outer protective layer is formed when the steel is treated with a metal coating resistant to carburization comprising tin, antimony, bismuth or arsenic.

10. The method of claim 9 , wherein the metal coating comprises tin.

11. The method of claim 10 , wherein the tin coating is applied by electroplating, vapor deposition or soaking in a molten tin bath.

12. The method for hydrodealkylating a hydrodealkylatable hydrocarbon according to claim 1 , wherein said portion of the reactor system is made of steel and treated by coating with aluminum or tin followed by application of a chromium oxide coating having a thickness sufficient to protect the aluminum coated or tin coated steel from carburization, metal-dusting and coking under low sulfur reaction conditions.

13. The method according to claim 12 , wherein said portion of the reactor system has been coated with aluminum by deeply diffusing a mixture of blended aluminum powders onto said portion at elevated temperatures.

14. The method according to claim 12 , wherein said portion of the reactor system has been coated with tin by electroplating.

15. The method for hydrodealkylating a hydrodealkylatable hydrocarbon according to claim 1 , wherein a portion of said reactor system has initially been coated with a coating comprising aluminum, followed by a post-treatment process comprising application of a metal coating comprising tin.

16. The method according to claim 15 , wherein the initial aluminum coating is applied by deeply diffusing a mixture of blended aluminum powders onto said portion at elevated temperatures.

17. The method for hydrodealkylating a hydrodealkylatable hydrocarbon according to claim 1 , wherein a portion of said reactor system is exposed to temperatures of at least about 700° F. during said contacting.

18. The method for hydrodealkylating a hydrodealkylatable hydrocarbon according to claim 16 , wherein a portion of said reactor system is exposed to temperatures of at least about 900° F. during said contacting.

19. The method for hydrodealkylating a hydrodealkylatable hydrocarbon according to claim 18 , wherein a portion of said reactor system is exposed to temperatures of between about 900° F. and 1800° F. during said contacting.

20. The method for hydrodealkylating a hydrodealkylatable hydrocarbon according to claim 1 , wherein said contacting takes place in the absence of a catalyst.

21. The method for hydrodealkylating a hydrodealkylatable hydrocarbon according to claim 1 , wherein said hydrocarbon comprises an alkyl-substituted benzene.

22. The method for hydrodealkylating a hydrodealkylatable hydrocarbon according to claim 21 , wherein said hydrocarbon is selected from the group consisting of toluene, m-xylene, o-xylene, p-xylene, mixed xylenes, ethyl benzene, n-propyl benzene, n-butyl benzene, cumene, isobutylbenzene, sec-butylbenzene, tert butylbenzene, and p-cymene.

23. The method for hydrodealkylating a hydrodealkylatable hydrocarbon according to claim 22 , wherein said hydrocarbon is toluene.

24. The method for hydrodealkylating a hydrodealkylatable hydrocarbon according to claim 1 , wherein toluene is contacted with hydrogen at a temperature from about 900° F. to 1800° F.

25. The method of hydrodealkylating a hydrodealkylatable hydrocarbon according to claim 24 , wherein said portion of said reactor system is coated with a film of a carburization resistant composition comprising tin or antimony.

26. A method according to claim 1 , wherein sulfur levels in the reactor system do not exceed about 50 ppm.

27. A method according to claim 26 , wherein sulfur levels in the reactor system do not exceed about 20 ppm.

28. A method for hydrodealkylating a hydrodealkylatable hydrocarbon comprising:
(i) providing a carburization and abrasion resistant protective layer to a nickel containing stainless steel portion of a hydrodealkylation reactor system by (a) applying to the stainless steel portion a metal plating, cladding or other coating of a metal effective for forming a carburization resistant protective layer, to a thickness effective to isolate the steel portion from hydrocarbons during operation while avoiding any substantial liquid metal embrittlement, and (b) forming the protective layer, anchored to the stainless steel portion through an intermediate bonding layer comprising carbide;
(ii) hydrodealkylating a hydrodealkylatable hydrocarbon feed wherein the sulfur levels in the reactor system do not exceed 100 ppm and wherein said metal is applied as a plating, cladding, or other coating comprising at least in major portion a metal selected from the group consisting of antimony, arsenic, bismuth, aluminum, gallium, germanium, indium, lead, selenium, tellurium, tin and mixtures thereof.

29. A method for hydrodealkylating a hydrodealkylatable hydrocarbon according to claim 28 , wherein said hydrocarbon feed comprises an alkyl-substituted benzene.

30. A method for hydrodealkylating a hydrodealkylatable hydrocarbon according to claim 28 , wherein said hydrocarbon feed comprises at least one member selected from the group consisting of toluene, m-xylene, o-xylene, p-xylene, mixed xylenes, ethyl benzene, n-propyl benzene, n-butyl benzene, cumene, isobutyl benzene, sec-butyl benzene, tert butyl benzene, and p-cymene.

31. A method for hydrodealkylating a hydrodealkylatable hydrocarbon according to claim 30 , wherein said hydrocarbon feed comprises toluene.

32. A method for hydrodealkylating a hydrodealkylatable hydrocarbon according to claim 28 , wherein toluene is contacted with hydrogen under temperature conditions of from about 900° F. to 1800° F.

33. A method according to claim 28 , wherein sulfur levels do not exceed about 50 ppm.

34. A method according to claim 33 , wherein sulfur levels do not exceed about 20 ppm.

35. A method according to claim 28 , wherein the metal is applied as a plating, cladding or other coating comprising at least in major proportion selected from the group consisting of antimony, arsenic, bismuth aluminum, copper, chromium, gallium, germanium, indium, lead, selenium, tellurium, tin and mixtures thereof.

36. A method according to claim 35 28 , wherein the material is selected from tin, antimony, germanium, selenium, and tellurium and chromium .

37. A method according to claim 36 , wherein the material is selected from tin, antimony, and germanium and chromium .

38. A method according to claim 35 28 , wherein the metal plating, cladding or other coating is applied to a thickness of between 0.5 mils and 15 mils.

39. A method according to claim 38 , wherein the metal plating, cladding or other coating is applied to a thickness of between 1 and 10 mils.

40. A method,according to claim 39 , wherein the metal plating, cladding or other coating is applied to a thickness of between 2 and 8 mils.

41. A method according to claim 28 , wherein the protective layer is applied to a furnace tube.

42. A method according to claim 35 28 , wherein the metal is applied as a plating.

43. A method according to claim 35 28 , wherein the metal is applied as a paint.

44. A method according to claim 43 , wherein the metal is applied as a tin-containing paint.

45. A method according to claim 44 , wherein the metal is applied as a tin-containing paint comprising a hydrogen decomposable tin compound, a solvent system, a finely divided tin metal and tin oxide effective as a sponge/dispersing/binding agent.

46. A method according to claim 44 , wherein the paint contains iron.

47. A method according to claim 46 , wherein the paint contains tin to iron in a ratio of between 10 and 1 by weight.

48. A method according to claim 28 , wherein the steel portion is a stainless steel portion and the bonding layer comprises carbide.

49. A method according to claim 28 , further comprising forming at least one additional protective layer on the surface of the protective layer.

50. A method according to claim 49 , further comprising forming a copper-based protective layer on a stannide protective layer.

51. A hydrocarbon conversion process conducted with a hydrocarbon feed having a sulfur content lower than about 100 ppm, said process selected from the group consisting of nonoxidative dehydrogenation of hydrocarbons to olefins and dienes, oxidative dehydrogenation of hydrocarbons to olefins and dienes, dehydrogenation of ethylbenzene to styrene, conversion of light hydrocarbons to aromatics, transalkylation of toluene to benzene and xylenes, dealkylation of alkylaromatics to aromatics, alkylation of aromatics to alkylaromatics, production of fuels and chemicals from H 2 and CO, steam reforming of hydrocarbons to H 2 and CO, and methanol alkylation of toluene to xylenes, comprising:
(i) providing a carburization and abrasion resistant protective layer to a nickel containing stainless steel portion of a reactor system by (a) applying to the stainless steel portion a metal plating, cladding or other coating of a metal effective for forming a carburization resistant protective layer, to a thickness effective to isolate the steel portion from hydrocarbons during operation while avoiding any substantial liquid metal embrittlement, and (b) forming the protective layer, anchored to the stainless steel portion through an intermediate carbide-rich bonding layer comprising carbide;
(ii) converting hydrocarbons in the reactor system and wherein said metal is applied as a plating, cladding or other coating comprising at least in major proportion a metal selected from the group consisting of antimony, arsenic, bismuth, aluminum, gallium, germanium, indium, lead, selenium, tellurium, tin and mixtures thereof.

52. A low-sulfur hydrocarbon conversion process according to claim 51 , wherein the metal is applied as a plating, cladding or other coating comprising at least one metal in major proportion selected from the group consisting of antimony, arsenic, bismuth aluminum, copper, chromium, gallium, germanium, indium, lead, selenium, tellurium, tin and mixtures thereof.

53. A method according to claim 52 51 , wherein the metal plating, cladding or other coating is applied to a thickness of between 0.5 mils and 15 mils.

54. A method according to claim 53 , wherein the metal plating, cladding or other coating is applied to a thickness of between 1 and 10 mils.

55. A method according to claim 54 , wherein the metal plating, cladding or other coating is applied to a thickness of between 2 and 8 mils.

56. A method according to claim 53 , wherein the protective layer is applied to a furnace tube.

57. A method according to claim 52 51 , wherein the metal is applied as a plating.

58. A method according to claim 57 , wherein the metal is applied as a chromium plating.

59. A method according to claim 52 51 , wherein the metal is applied as a paint.

60. A method according to claim 59 , wherein the metal is applied as a tin-containing paint.

61. A method according to claim 60 , wherein the metal is applied as a tin-coating paint comprising a hydrogen decomposable tin compound, a solvent system, a finely divided tin metal and tin oxide effective as a sponge/dispersing/binding agent.

62. A method according to claim 60 , wherein the paint contains iron.

63. A method according to claim 62 , wherein the paint contains tin to iron in a ratio of between 10 and 1 by weight.

64. A method according to claim 59 , wherein the metal is applied as a chromium-containing paint.

65. A method according to claim 52 , wherein the steel portion is a stainless steel portion and the bonding layer comprises carbide.

66. A method according to claim 52 51 , wherein the metal is selected from tin, antimony, germanium, selenium, tellurium, chromium, and mixtures thereof.

67. A method according to claim 66 , wherein the metal is selected from tin, antimony, germanium, chromium, and mixtures thereof.

68. A process according to claim 51 , wherein said low-sulfur hydrocarbon conversion process is selected from the conversion of C 2 -C 5 hydrocarbons to aromatics, production of fuels and chemicals from H 2 and CO, and steam reforming of hydrocarbons to H 2 and CO.

69. In a method for hydrodealkylating and hydrodealkylatable hydrocarbon wherein said hydrocarbon is contacted with hydrogen the improvement comprising conducting said hydrodealkylation under low sulfur hydrodealkylation conditions of 100 ppm or less in a reactor system in which at least a portion of said reactor system which is susceptible to carburization has been subjected to treatment with a carburization resistant composition wherein said treatment comprises applying a coating or film of said carburization resistant composition and wherein said composition comprises, in major proportion, a member selected from the group consisting of aluminum, antimony, arsenic, bismuth, brass, germanium, indium, lead, selenium, tellurium, tin or intermetallic compounds and alloys thereof.

70. The method of claim 69 , wherein at least a portion of said coating or film is a Cu—Sn alloy or a Cu—Sb alloy.

71. The method of claim 69 , wherein said treatment is applied as a coating or film provided as a plating, cladding, paint or other coating, to a base construction material.

72. The method of claim 69 , wherein said carburization resistant composition contains tin.

73. The method of claim 69 , wherein said treatment is effected by adding an anti- carburizing and anti - coking agent selected from the group of organo - tin compounds, organo - antimony compounds, organo - bismuth compounds, organo - arsenic compounds and organo - lead compounds to said hydrocarbon.

74. The method to claim 69 , wherein said treatment is effected by adding an organo- tin non - sulfur, anti - carburizing and anti - coking agent to the hydrocarbon.

75. The method of claim 69 , wherein at least a portion of said reactor system is constructed from a stainless steel treated with a metal coating resistant to carburization comprising tin, antimony, germanium, bismuth or arsenic.

76. The method of claim 75 , wherein said coating comprises tin.

77. The method of claim 76 , wherein the tin coating is applied by electroplating, vapor deposition, or soaking in a molten tin bath.

78. The method of claim 69 , wherein said portion of the reactor system is made of steel and wherein said treatment comprises coating said portion with aluminum or tin followed by application of a chromium oxide coating having a thickness sufficient to protect the aluminum coated or tin coated steel from carburization, metal- dusting and coking under low sulfur reaction conditions.

79. The method of claim 78 , wherein said portion of the reactor system has been coated with aluminum by deeply diffusing a mixture of blended aluminum powders onto said portion at elevated temperatures.

80. The method according to claim 78 , wherein said portion of the reactor system has been coated with tin by electroplating.

81. The method of claim 69 , wherein a portion of said reactor system has initially been coated with a coating comprising aluminum, followed by a post- treatment process comprising application of a metal coating comprising tin.

82. The method of claim 69 , wherein a portion of said reactor system is exposed to temperatures of at least about 700 ° F. during said contacting.

83. The method of claim 82 , wherein a portion of said reactor system is exposed to temperatures of between about 900 ° F. and 1800 ° F. during said contacting.

84. The method of claim 69 , wherein said contacting takes place in the absence of a catalyst.

85. The method of claim 69 , wherein said hydrocarbon comprises an alkyl- substituted benzene.

86. The method of claim 85 , wherein said hydrocarbon is selected from the group consisting of toluene, m- xylene, o - xylene, p - xylene, mixed xylenes, ethyl benzene, n - propyl benzene, n - butyl benzene, cumene, isobutylbenzene, sec - butylbenzene, tert butylbenzene, and p - cymene.

87. The method of claim 85 , wherein said hydrocarbon is toluene.

88. The method of claim 87 , wherein said portion of said reactor system is coated with a film of a carburization resistant composition comprising tin or antimony.

89. In a method for hydrodealkylating a hydrodealkylatable hydrocarbon the improvement comprising:
( i ) conducting said method in a hydrodealkylation reactor system to which a nickel containing stainless steel portion of said reactor system has been provided with a carburization and abrasion resistant protective layer by ( a ) applying to said stainless steel portion a metal plating, cladding or other coating of a metal effective for forming a carburization resistant protective layer, to a thickness effective to isolate said stainless steel portion from hydrocarbons during operation while avoiding any substantial liquid metal embrittlement, and ( b ) forming the protective layer, anchored to said stainless the steel portion through an intermediate bonding layer comprising carbide; and
( ii ) hydrodealkylating a hydrodealkylatable hydrocarbon feed wherein the sulfur levels in the reactor system do not exceed about 100 ppm; and wherein said metal was applied as a plating, cladding or other coating comprising at least in major proportion a metal selected from the group consisting of antimony, arsenic, bismuth, aluminum, gallium, germanium, indium, lead, selenium, tellurium, tin and mixtures thereof.

90. A method for hydrodealkylating a hydrodealkylatable hydrocarbon according to claim 89 , wherein said hydrodealkylatable hydrocarbon comprises an alkyl- substituted benzene.

91. A method for hydrodealkylating a hydrodealkylatable hydrocarbon according to claim 89 , wherein said hydrodealkylatable hydrocarbon comprises at least one member selected from the group consisting of toluene, m- xylene, o - xylene, p - xylene, mixed xylenes, ethyl benzene, n - propyl benzene, n - butyl benzene, cumene, isobutyl benzene, sec - butyl benzene, tert butyl benzene, and p - cymene.

92. A method for hydrodealkylating a hydrodealkylatable hydrocarbon according to claim 89 , wherein toluene is contacted with hydrogen under temperature conditions of from about 900 ° F. to 1800 ° F.

93. The method of claim 89 , wherein at least one additional protective layer has been formed on the surface of the protective layer.

94. The method of claim 93 , wherein said additional layer is a copper- based protective layer and said protective layer is a stannide protective layer.

95. In a hydrocarbon conversion method selected from the group consisting of nonoxidative dehydrogenation of hydrocarbons to olefins and dienes; oxidative dehydrogenation of hydrocarbons to olefins and dienes; dehydrogenation of ethylbenzene to styrene; conversion of light hydrocarbons to aromatics; transalkylation of toluene to benzene and xylenes; dealkylation of alkylaromatics to aromatics; alkylation of aromatics to alkylaromatics; production of fuels and chemicals from H 2 and CO; steam reforming of hydrocarbons to H 2 and CO; and methanol alkylation of toluene to xylenes the improvement comprising conducting said hydrocarbon conversion with a hydrocarbon stream or H 2 and CO stream having a sulfur content lower than about 100 ppm in a reactor system in which a nickel containing stainless steel portion thereof has a carburization and abrasion resistant protective layer obtained by applying to said stainless steel portion a metal plating, cladding or other coating of a metal effective for forming a carburization resistant protective layer to thickness effective to isolate said stainless steel portion through an intermediate carbide - rich bonding layer comprising carbide and wherein said protective layer is formed from a plating, cladding or other coating comprising at least one metal in major proportion selected from the group consisting of antimony, arsenic, bismuth, aluminum, gallium, germanium, indium, lead, selenium, tellurium, tin and mixtures thereof.

96. The method of claim 95 , wherein said hydrocarbon conversion process is selected from the conversion of C 2 -C 5 hydrocarbons to aromatics; production of fuels and chemicals from H 2 and CO; and steam reforming hydrocarbons to H 2 and CO.

97. The method of claim 96 , wherein said hydrocarbon conversion process is the production of fuels and chemicals from H 2 and CO.

98. The method of claim 96 , wherein said conversion process is steam reforming of hydrocarbons to H 2 and CO.

99. The method of claim 96 , wherein said stainless steel portion comprises furnace tubes.

100. The method of claim 95 , wherein said conversion process is selected from the group consisting of nonoxidative dehydrogenation of hydrocarbons to olefins and dienes and oxidative dehydrogenation of hydrocarbons to olefins and dienes.

101. The method of claim 95 , wherein said conversion process is selected from the group consisting of dehydrogenation of ethylbenzene to styrene and the conversion of light hydrocarbons to aromatics.

102. The method of claim 95 , wherein said conversion process is selected from the group consisting of the transalkylation of toluene to benzene and xylenes.

103. The method of claim 95 , wherein said conversion process is selected from the group consisting of the alkylation of aromatics to alkylaromatics and the methanol alkylation of toluene to xylenes.

104. In a hydrocarbon conversion method selected from the group consisting of nonoxidative dehydrogenation of hydrocarbons to olefins and dienes; oxidative dehydrogenation of hydrocarbons to olefins and dienes; dehydrogenation of ethylbenzene to styrene; conversion of light hydrocarbons to aromatics; transalkylation of toluene to benzene and xylenes; dealkylation of alkylaromatics to aromatics; alkylation of aromatics to alkylaromatics; production of fuels and chemicals from H 2 and CO; steam reforming of hydrocarbons to H 2 and CO; and methanol alkylation of toluene to xylenes the improvement comprising conducting said hydrocarbon conversion with a hydrocarbon stream or H 2 and CO stream having a sulfur content lower than about 100 ppm in a reactor system in which an essentially nickel free steel portion thereof has a carburization and abrasion resistant protective layer obtained by applying to said steel portion a metal plating, cladding or other coating of a metal effective for forming a carburization resistant protective layer to thickness effective to isolate said steel portion from hydrocarbons during operation while avoiding any substantial liquid metal embrittlement and wherein said protective layer comprises intermetallic compounds or alloys of iron and said metal.

105. The method of claim 104 , wherein said protective layer is formed from a plating, cladding or other coating comprising at least one metal in major proportion selected from the group consisting of antimony, arsenic, aluminum, copper, chromium, gallium, germanium, selenium, tellurium, tin and mixtures thereof.

106. The method of claim 104 , wherein said hydrocarbon conversion process is selected from the conversion of C 2 -C 5 hydrocarbons to aromatics, production of fuels and chemicals from H 2 and CO, and steam reforming hydrocarbons to H 2 and CO.

107. The method of claim 106 , wherein said hydrocarbon conversion process is the production of fuels and chemicals from H 2 and CO.

108. The method of claim 107 , wherein said protective layer is formed from a plating, cladding or other coating comprising at least one metal in major proportion selected from the group consisting of antimony, arsenic, aluminum, copper, chromium, gallium, germanium, selenium, tellurium, tin and mixtures thereof.

109. The method of claim 104 , wherein said conversion process is steam reforming of hydrocarbons to H 2 and CO.

110. The method of claim 109 , wherein the protective layer is formed from a plating, cladding or other coating comprising at least one metal in major proportion selected from the group consisting of antimony, arsenic, aluminum, copper, chromium, gallium, germanium, selenium, tellurium, tin and mixtures thereof.

111. The method of claim 106 , wherein said steel portion comprises furnace tubes.

112. The method of claim 104 , wherein said conversion process is selected from the group consisting of nonoxidative dehydrogenation of hydrocarbons to olefins and dienes and oxidative dehydrogenation of hydrocarbons to olefins and dienes.

113. The processing according to claim 112 , wherein said protective layer is formed from a plating, cladding or other coating comprising at least one metal in major proportion selected from the group consisting of antimony, arsenic, aluminum, copper, chromium, gallium, germanium, selenium, tellurium, tin and mixtures thereof.

114. The method of claim 104 , wherein said conversion process is selected from the group consisting of dehydrogenation of ethylbenzene to styrene and the conversion of light hydrocarbons to aromatics.

115. The processing according of claim 114 , wherein said protective layer is formed from a plating, cladding or other coating comprising at least one metal in major proportion selected from the group consisting of antimony, arsenic, bismuth, aluminum, copper, chromium, gallium, germanium, indium, lead, selenium, tellurium, tin and mixtures thereof.

116. The method of claim 104 , wherein said conversion process is selected from the group consisting of the transalkylation of toluene to benzene and xylenes.

117. The method according to claim 116 , wherein said protective layer is formed from a plating, cladding or other coating comprising at least one metal in major proportion selected from the group consisting of antimony, arsenic, bismuth, aluminum, copper, chromium, gallium, germanium, indium, lead, selenium, tellurium, tin and mixtures thereof.

118. The method of claim 104 , wherein said conversion process is selected from the group consisting of the alkylation of aromatics to alkylaromatics and the methanol alkylation of toluene to xylenes.

119. The method according to claim 118 , wherein said protective layer is formed from a plating, cladding or other coating comprising at least one metal in major proportion selected from the group consisting of antimony, arsenic, aluminum, copper, chromium, gallium, germanium, selenium, tellurium, tin and mixtures thereof.

120. The process of claim 104 , wherein said steel is mild steel.

121. In a hydrocarbon conversion process selected from the group consisting of nonoxidative dehydrogenation of hydrocarbons to olefins and dienes; oxidative dehydrogenation of hydrocarbons to olefins and dienes; dehydrogenation of ethylbenzene to styrene; conversion of light hydrocarbons to aromatics; transalkylation of toluene to benzene and xylenes; dealkylation of alkylaromatics to aromatics; alkylation of aromatics to alkylaromatics; production of fuels and chemicals from H 2 and CO; steam reforming of hydrocarbons to H 2 and CO; and methanol alkylation of toluene to xylenes the improvement comprising conducting said hydrocarbon conversion with a hydrocarbon stream having a sulfur content lower than about 100 ppm in a reactor system in which a steel portion thereof has a carburization and abrasion protective layer derived from a metal, in major proportion, selected from the group consisting of tin, arsenic, antimony, aluminum, bismuth, germanium, gallium, indium, selenium, tellurium, lead, brass and intermetallic compounds and alloys thereof attached thereto of a thickness effective to isolate the steel portion from hydrocarbons during operations while avoiding any substantial liquid embrittlement.

122. The process of claim 121 , wherein said steel portion is nickel containing stainless steel and wherein said protective layer is anchored to said stainless steel portion thereof through an intermediate bonding layer comprising carbide and wherein said metal is selected from the group consisting of copper, tin, arsenic, germanium, gallium, selenium, tellurium and intermetallic compounds and alloys thereof.

123. The process of claim 121 , wherein said steel portion is essentially nickel free steel and wherein said protective layer comprises at least one intermetallic compound or alloy of said metal and iron.

124. In a hydrocarbon conversion method utilizing a cracking furnace the improvement comprising conducting said hydrocarbon conversion with a hydrocarbon stream having a sulfur content lower than about 100 ppm and wherein a nickel containing stainless steel portion of said cracking furnace has a carburization and abrasion resistant protective layer obtained by applying to said stainless steel portion a metal plating, cladding or other coating of a metal effective for forming a carburization resistance protective layer of a thickness effective to isolate the steel portion from hydrocarbons during operation while avoiding any substantial liquid metal embrittlement and wherein said protective layer is anchored to the stainless steel portion through an intermediate carbide- rich bonding layer comprising carbide and wherein said protective layer is formed from a plating, cladding or other coating comprising at least one metal in major proportion selected from the group consisting of antimony, arsenic, bismuth, aluminum, gallium, germanium, indium, lead, selenium, tellurium, tin and mixtures thereof.

125. The method of claim 124 , wherein said hydrocarbon comprises ethane and said cracking furnace is an ethane cracking furnace having furnace tubes having said protective layer.

126. The method according to claim 125 , wherein said metal coating is a plating, cladding or other coating comprising at least one metal in major proportion selected from the group consisting of antimony, arsenic, bismuth, aluminum, copper, gallium, germanium, indium, lead, selenium, tellurium, tin and mixtures thereof.

127. The process of claim 124 , wherein said cracking furnace is operated at temperatures between 800 and 2000 ° F.

128. The process of claim 124 , wherein said cracking furnace is operated at temperatures between 1400 and 1700 ° F.

129. The process of claim 124 , wherein said hydrocarbon is propane.

130. In a hydrocarbon conversion process utilizing a cracking furnace the improvement comprising conducting said hydrocarbon conversion with a hydrocarbon stream having a sulfur content lower than about 100 ppm and wherein an essentially nickel free steel portion of said cracking furnace has a carburization and abrasion resistant protective layer obtained by applying to said steel portion a metal plating, cladding or other coating of a metal effective for forming a carburization resistent protective layer of a thickness effective to isolate the steel portion form hydrocarbons during operation while avoiding any substantial liquid metal embrittlement and wherein said protective layer comprises intermetallic compounds of or alloys of iron and said metal.

131. The process of claim 130 , wherein said hydrocarbon is ethane.

132. The process of claim 130 , wherein said hydrocarbon is propane.

133. The process of claim 130 , wherein said steel is mild steel.

134. The method of claims 88 , 89 , 97 , 121 , 124 or 130 wherein said sulfur levels do not exceed 50 ppm.

135. The method of claims 88 , 89 , 97 , 121 , 124 or 130 wherein said sulfur levels do not exceed 20 ppm.

136. The method of claims 89 , 95 , 97 , 98 , 104 , 107 , 109 , 124 , or 127 , wherein the plating, cladding or other coating has a thickness of between 0 . 5 mils and 15 mils.

137. The method of claims 89 , 95 , 97 , 98 , 104 , 107 , or 109 wherein the plating, cladding or other coating has a thickness of between 1 and 10 mils.

138. The method of claims 89 , 95 , 97 , 98 , 104 , 107 , 109 , 124 , or 130 wherein the plating, cladding or other coating has a thickness of between 2 and 8 mils.

139. The method of claims 89 , 95 , 97 , 98 , 104 , 107 , 109 , 121 , 124 , or 130 wherein the metal is applied as a tin- containing paint.

140. The method of claims 89 , 95 , 97 , 98 , 104 , 107 , 109 , 121 , 127 , or 130 wherein the metal is applied as a tin- containing paint comprising a hydrogen decomposable tin compound, a solvent system, a finely divided tin metal and tin oxide effective as a sponge/dispersing/binding agent.

141. The method of claim 140 , wherein the paint contain iron.

142. The method of claim 141 , wherein the paint contains iron in a tin to iron ratio of between 10 and 1 by weight.

143. The method of claim 95 , 97 , 98 , 100 , 101 , 102 , 103 , 104 , 106 , 109 , 112 , 114 , 116 , 118 , 124 , 126 , or 130 wherein a major portion of said plating, cladding or other coating is tin.

144. The method of claims 105 , 108 , 110 , 113 , 115 , 117 , 119 , or 130 , wherein a major portion of said plating, cladding or other coating is chromium.

145. A method according to claim 95 , 97 , 98 , 100 , 101 , 102 , 103 , 104 , 106 , 109 , 112 , 114 , 116 , 118 , 124 , or 130 wherein the metal is selected from tin, antimony, germanium, selenium, tellurium, and mixtures thereof.

146. A method according to claim 145 , wherein said metal is selected from tin, antimony, germanium, and mixtures thereof.

147. The method of claim 89 , 97 , 98 , 104 , 107 , 109 , 124 , or 130 wherein the plating, cladding or other coating is a plating.

148. The method of claims 104 , 108 , 110 , or 130 , wherein the plating, cladding, or other coating is a plating and said plating is chromium plating.

149. The method of claim 89 , 97 , 98 , 104 , 107 , or 109 , wherein the plating, cladding or other coating is a paint.

150. The method of claims 105 , 109 , 110 , or 130 , wherein the plating, cladding or other coating is a paint and said paint is a chromium containing paint.

151. The method of claim 9 , 51 , or 89 wherein said nickel containing stainless steel contains about 75 wt. % nickel, 16 wt. % chromium and 9 wt. % iron.

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