DE68921777T2 - Hochwirksame Silberkatalysatoren zur Herstellung von Ethylenoxid durch Ethylenoxidation. - Google Patents

Hochwirksame Silberkatalysatoren zur Herstellung von Ethylenoxid durch Ethylenoxidation.

Info

Publication number
DE68921777T2
DE68921777T2 DE68921777T DE68921777T DE68921777T2 DE 68921777 T2 DE68921777 T2 DE 68921777T2 DE 68921777 T DE68921777 T DE 68921777T DE 68921777 T DE68921777 T DE 68921777T DE 68921777 T2 DE68921777 T2 DE 68921777T2
Authority
DE
Germany
Prior art keywords
process according
alumina
silver
catalyst
weight
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
DE68921777T
Other languages
German (de)
English (en)
Other versions
DE68921777D1 (de
Inventor
Guoquan Research Institute Jin
Jiquan Research Institute Jin
Guochun Tianjin Chemical R Luo
Liandi Tianjin Chemical Shang
Yong Research Institute Of Xu
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Beijing Research Institute of Beijing Yanshan Petrochemical Corp
China Petrochemical Corp
Original Assignee
Beijing Research Institute of Beijing Yanshan Petrochemical Corp
China Petrochemical Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Beijing Research Institute of Beijing Yanshan Petrochemical Corp, China Petrochemical Corp filed Critical Beijing Research Institute of Beijing Yanshan Petrochemical Corp
Application granted granted Critical
Publication of DE68921777D1 publication Critical patent/DE68921777D1/de
Publication of DE68921777T2 publication Critical patent/DE68921777T2/de
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Classifications

    • CCHEMISTRY; METALLURGY
    • C07ORGANIC CHEMISTRY
    • C07DHETEROCYCLIC COMPOUNDS
    • C07D301/00Preparation of oxiranes
    • C07D301/02Synthesis of the oxirane ring
    • C07D301/03Synthesis of the oxirane ring by oxidation of unsaturated compounds, or of mixtures of unsaturated and saturated compounds
    • C07D301/04Synthesis of the oxirane ring by oxidation of unsaturated compounds, or of mixtures of unsaturated and saturated compounds with air or molecular oxygen
    • C07D301/08Synthesis of the oxirane ring by oxidation of unsaturated compounds, or of mixtures of unsaturated and saturated compounds with air or molecular oxygen in the gaseous phase
    • C07D301/10Synthesis of the oxirane ring by oxidation of unsaturated compounds, or of mixtures of unsaturated and saturated compounds with air or molecular oxygen in the gaseous phase with catalysts containing silver or gold
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01JCHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/38Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
    • B01J23/48Silver or gold
    • B01J23/50Silver
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01JCHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/38Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
    • B01J23/54Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
    • B01J23/66Silver or gold
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01JCHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/0009Use of binding agents; Moulding; Pressing; Powdering; Granulating; Addition of materials ameliorating the mechanical properties of the product catalyst
    • B01J37/0018Addition of a binding agent or of material, later completely removed among others as result of heat treatment, leaching or washing,(e.g. forming of pores; protective layer, desintegrating by heat)
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02PCLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P20/00Technologies relating to chemical industry
    • Y02P20/50Improvements relating to the production of bulk chemicals
    • Y02P20/52Improvements relating to the production of bulk chemicals using catalysts, e.g. selective catalysts

Landscapes

  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Catalysts (AREA)
  • Epoxy Compounds (AREA)
  • Low-Molecular Organic Synthesis Reactions Using Catalysts (AREA)
DE68921777T 1988-02-03 1989-02-02 Hochwirksame Silberkatalysatoren zur Herstellung von Ethylenoxid durch Ethylenoxidation. Expired - Lifetime DE68921777T2 (de)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN88100400A CN1009437B (zh) 1988-02-03 1988-02-03 乙烯氧化制环氧乙烷高效银催化剂

Publications (2)

Publication Number Publication Date
DE68921777D1 DE68921777D1 (de) 1995-04-27
DE68921777T2 true DE68921777T2 (de) 1995-11-23

Family

ID=4831321

Family Applications (1)

Application Number Title Priority Date Filing Date
DE68921777T Expired - Lifetime DE68921777T2 (de) 1988-02-03 1989-02-02 Hochwirksame Silberkatalysatoren zur Herstellung von Ethylenoxid durch Ethylenoxidation.

Country Status (6)

Country Link
US (1) US5063195A (enExample)
EP (1) EP0327356B1 (enExample)
JP (1) JPH0667475B2 (enExample)
CN (1) CN1009437B (enExample)
DE (1) DE68921777T2 (enExample)
IN (1) IN171804B (enExample)

Families Citing this family (71)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5173469A (en) * 1989-11-09 1992-12-22 Huels Aktiengesellschaft Silver catalyst suitable for oxidation of ethylene and process for the production of the catalyst
EP0428845B2 (de) * 1989-11-09 1998-12-23 Hüls Aktiengesellschaft Silberkatalysator für die Oxidation von Ethylen und Verfahren zu seiner Herstellung
DE4106508A1 (de) * 1991-03-01 1992-09-03 Basf Ag Silberkatalysator
DE4311608A1 (de) * 1993-04-08 1994-12-15 Huels Chemische Werke Ag Silberkatalysator zur Oxidation von Ethylen zu Ethylenoxid und Verfahren zur Herstellung von Ethylenoxid
US5380697A (en) * 1993-09-08 1995-01-10 Shell Oil Company Ethylene oxide catalyst and process
DE69600628T2 (de) * 1995-02-01 1999-02-25 Shell Internationale Research Maatschappij B.V., Den Haag/S'gravenhage Alkylenoxidkatalysator und verfahren
US5739075A (en) * 1995-10-06 1998-04-14 Shell Oil Company Process for preparing ethylene oxide catalysts
US5801259A (en) * 1996-04-30 1998-09-01 Shell Oil Company Ethylene oxide catalyst and process
EP1002575B1 (en) * 1998-11-17 2005-03-30 Nippon Shokubai Co., Ltd. Catalyst carrier for use in production of ethylene oxide
US6831037B2 (en) * 2002-02-25 2004-12-14 Saint-Gobain Norpro Corporation Catalyst carriers
CN100553763C (zh) * 2002-02-25 2009-10-28 国际壳牌研究有限公司 负载的银催化剂和使用该催化剂的环氧化方法
US6987080B2 (en) * 2002-03-01 2006-01-17 Scientific Design Company, Inc. Ethylene oxide catalyst carrier preparation
BR0312011B1 (pt) * 2002-06-28 2014-08-05 Shell Int Research Processo para a partida de um processo de epoxidação, um catalisador e um processo para a epoxidação de uma olefina
US20040224841A1 (en) 2003-05-07 2004-11-11 Marek Matusz Silver-containing catalysts, the manufacture of such silver-containing catalysts, and the use thereof
AU2004238820B2 (en) * 2003-05-07 2008-01-31 Shell Internationale Research Maatschappij B.V. Silver-containing catalysts, the manufacture of such silver containing catalysts, and the use thereof
US8148555B2 (en) * 2003-06-26 2012-04-03 Shell Oil Company Method for improving the selectivity of a catalyst and a process for the epoxidation of an olefin
EP1658135A1 (en) * 2003-08-22 2006-05-24 Union Carbide Chemicals & Plastics Technology Corporation Modified alumina carriers and silver-based catalysts for the production of alkylene oxides
JP4824569B2 (ja) * 2003-10-16 2011-11-30 ダウ テクノロジー インベストメンツ リミティド ライアビリティー カンパニー アルキレンオキサイド製造用の増強された安定性、効率及び/又は活性を有する触媒
TW200600190A (en) 2004-04-01 2006-01-01 Shell Int Research Process for preparing a silver catalyst, the catalyst, and use thereof in olefin oxidation
CA2571179C (en) * 2004-06-18 2014-06-10 Shell Internationale Research Maatschappij B.V. A process for the production of an olefin oxide, a 1,2-diol, a 1,2-diol ether, or an alkanolamine
CN100572370C (zh) 2004-06-18 2009-12-23 国际壳牌研究有限公司 生产烯烃氧化物、1,2-二醇、1,2-二醇醚或链烷醇胺的方法
MX2007001684A (es) * 2004-08-12 2007-04-12 Shell Int Research Metodo para la preparacion de un catalizador formado, el catalizador, y uso del catalizador.
BRPI0514814A (pt) * 2004-09-01 2008-06-24 Shell Int Research processo de epoxidação de olefina, um catalisador para uso no processo, um veìculo para uso na preparação do catalisador, e processo para preparar o veìculo
US8536083B2 (en) 2004-09-01 2013-09-17 Shell Oil Company Olefin epoxidation process, a catalyst for use in the process, a carrier for use in preparing the catalyst, and a process for preparing the carrier
BRPI0515905A (pt) 2004-09-24 2008-08-12 Shell Int Research processo para selecionar partìculas moldadas, um processo para instalar um sistema, um processo para reagir uma carga de alimentação gasosa em um tal sistema, um produto de programa de computação e um sistema de computação
KR20070106772A (ko) * 2005-02-21 2007-11-05 셀 인터나쵸나아레 레사아치 마아츠샤피 비이부이 올레핀의 에폭시화 방법, 그 방법에 사용하기 위한 촉매,그 촉매를 제조하는데 이용하기 위한 담체, 및 그 담체의제조방법
US7507844B2 (en) * 2005-05-09 2009-03-24 Sd Lizenzverwertungsgesellschaft Mbh & Co. Kg Nanometer scale restructuring of alumina carrier surface and catalysts for the production of alkene oxides
KR101369619B1 (ko) * 2005-06-07 2014-03-05 셀 인터나쵸나아레 레사아치 마아츠샤피 비이부이 산화올레핀, 1,2-디올, 1,2-디올 에테르 또는 알칸올아민의제조방법, 이를 위한 촉매, 이 촉매의 제조방법
TWI334363B (en) 2005-06-07 2010-12-11 Saint Gobain Ceramics A catalyst carrier
US8791280B2 (en) * 2005-08-10 2014-07-29 Sd Lizenzverwertungsgesellschaft Mbh & Co. Kg Process for preparation of catalyst carrier and its use in catalyst preparation
US7879126B2 (en) 2006-07-21 2011-02-01 Dow Global Technologies Inc. Diesel particulate filter
JP4267015B2 (ja) * 2006-09-29 2009-05-27 株式会社日本触媒 エチレンオキシド製造用触媒およびエチレンオキシドの製造方法
EP2089155B1 (en) * 2006-11-01 2020-04-01 Dow Global Technologies LLC Methods for the preparation of shaped porous bodies of alpha-alumina
EP2152411B1 (en) 2007-05-09 2019-12-04 Shell International Research Maatschappij B.V. An epoxidation catalyst, a process for preparing the catalyst, and a process for the production of an olefin oxide, a 1,2-diol, a 1,2-diol ether, a 1,2-carbonate, or an alkanolamine
US7507845B1 (en) * 2007-08-27 2009-03-24 Sd Lizenzverwertungsgesellschaft Mbh & Co Kg Process for production of an olefin oxide
US7714152B2 (en) 2007-08-30 2010-05-11 Sd Lizenzverwertungsgesellschaft Mbh & Co. Kg Carrier for olefin oxide catalyst
WO2009119416A1 (ja) * 2008-03-26 2009-10-01 株式会社日本触媒 エチレンオキシド製造用触媒および該触媒を用いたエチレンオキシドの製造方法
CN102056909B (zh) * 2008-05-07 2014-03-05 国际壳牌研究有限公司 环氧化工艺的开车方法及环氧乙烷、1,2-二醇、1,2-二醇醚、1,2-碳酸酯或链烷醇胺的制备方法
KR101629038B1 (ko) 2008-05-07 2016-06-09 셀 인터나쵸나아레 레사아치 마아츠샤피 비이부이 산화올레핀, 1,2-디올, 1,2-디올 에테르, 1,2-카보네이트 또는 알칸올아민의 생산방법
BRPI0915854A2 (pt) * 2008-07-14 2015-08-04 Basf Se Processo para preparar óxido de etileno
JP5101428B2 (ja) * 2008-08-05 2012-12-19 株式会社日本触媒 エチレンオキシド製造用触媒の充填方法、エチレンオキシド製造用反応器およびエチレンオキシドの製造方法
JP5584284B2 (ja) 2009-04-21 2014-09-03 ダウ テクノロジー インベストメンツ リミティド ライアビリティー カンパニー レニウム促進されたエポキシ化触媒の効率を高める方法及びこれらの方法を利用したエポキシ化方法
JP5756088B2 (ja) * 2009-04-21 2015-07-29 ダウ テクノロジー インベストメンツ リミティド ライアビリティー カンパニー エポキシ化反応及びその運転条件
US8524927B2 (en) 2009-07-13 2013-09-03 Velocys, Inc. Process for making ethylene oxide using microchannel process technology
KR101786935B1 (ko) 2009-12-28 2017-10-18 다우 테크놀로지 인베스트먼츠 엘엘씨. 알킬렌 옥사이드의 제조시 은 촉매 상의 은 클로라이드의 생성을 제어하는 방법
EP2547434B1 (en) 2010-03-17 2020-01-08 Dow Technology Investments LLC Catalytic fixed bed reactor and method for producing ethylene oxide by partial oxidation of ethylene
CN102397795B (zh) * 2010-09-13 2014-03-19 中国石油化工股份有限公司 环氧乙烷生产用银催化剂的载体、其制备方法、由其制成的银催化剂及其应用
CN102441435B (zh) 2010-09-30 2014-01-01 中国石油化工股份有限公司 制备银催化剂用氧化铝载体的方法、由此得到的载体及其应用
CN102463141B (zh) 2010-11-02 2015-05-06 中国石油化工股份有限公司 一种氧化铝载体、其制备方法、由其制成的银催化剂及其应用
EP2649059B1 (en) 2010-12-10 2016-02-24 Dow Technology Investments LLC Method of reducing the value of an alkylene oxide production parameter in a process of making an alkylene oxide using a high efficiency catalyst
WO2012082389A1 (en) 2010-12-15 2012-06-21 Dow Technology Investments Llc Method of starting-up a process of producing an alkylene oxide using a high-efficiency catalyst
CA2836060C (en) 2011-05-30 2020-06-02 John Richard MAYER Testing and selection methods for catalyst support structures
US9259726B2 (en) 2011-06-06 2016-02-16 Dow Technology Investments Llc Methods for producing epoxidation catalysts and epoxidation methods utilizing them
SG11201401948UA (en) 2011-10-31 2014-09-26 Dow Technology Investments Llc Methods for producing epoxidation catalysts and epoxidation methods utilizing these
SG11201403042SA (en) 2011-12-09 2014-10-30 Dow Technology Investments Llc Method of maintaining the value of an alkylene oxide production parameter in a process of making an alkylene oxide using a high efficiency catalyst
CN104125858B (zh) 2011-12-19 2017-07-11 陶氏技术投资有限责任公司 根据催化剂参考性质配制环氧烷催化剂的方法
US9468906B2 (en) 2012-03-02 2016-10-18 Basf Se Porous inorganic body
EP2819781A4 (en) * 2012-03-02 2016-01-27 Basf Se Porous inorganic body
JP6247279B2 (ja) 2012-03-27 2017-12-13 ダウ テクノロジー インベストメンツ リミティド ライアビリティー カンパニー マンガン含有担持銀触媒中間体の製造方法
CN103816941B (zh) * 2012-11-19 2016-03-30 中国石油化工股份有限公司 一种α-氧化铝载体及其制备方法
CA2987427A1 (en) * 2015-06-02 2016-12-08 Scientific Design Company, Inc. Epoxidation process
TWI772322B (zh) 2016-09-02 2022-08-01 美商陶氏科技投資有限公司 製備環氧化催化劑之方法
CA3043504A1 (en) 2016-12-02 2018-06-07 Shell Internationale Research Maatschappij B.V. Methods for conditioning an ethylene epoxidation catalyst and associated methods for the production of ethylene oxide
US10449520B2 (en) 2017-05-15 2019-10-22 Scientific Design Company, Inc. Porous bodies with enhanced crush strength
CN109107553B (zh) * 2017-06-23 2021-04-13 中国石油化工股份有限公司 氧化铝载体及其制备方法和银催化剂及应用
CN107902745B (zh) * 2017-11-30 2021-08-17 浙江奇彩环境科技股份有限公司 一种垃圾渗滤液浓水的处理方法
EP3731963A1 (en) 2017-12-28 2020-11-04 Dow Technology Investments LLC Process for preparing an epoxidation catalyst
US10676401B2 (en) 2018-04-23 2020-06-09 Scientific Design Company, Inc. Porous bodies with enhanced pore architecture prepared with oxalic acid
CN112206798B (zh) * 2020-10-29 2022-03-22 润和催化材料(浙江)有限公司 一种乙烯氧化制环氧乙烷的银催化剂及其制备方法和应用
CN115475609A (zh) * 2021-06-15 2022-12-16 中国石油化工股份有限公司 一种具有高稳定性的α-氧化铝载体与银催化剂和烯烃环氧化方法
WO2025189084A1 (en) * 2024-03-08 2025-09-12 Scientific Design Llc Methods of forming substantially all platelet alumina powders and alumina carriers

Family Cites Families (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3172893A (en) * 1964-08-27 1965-03-09 Ethylene oxtoationximproved s silver catalyst
US4012425A (en) * 1972-01-07 1977-03-15 Shell Oil Company Ethylene oxide process
FR2179967B1 (enExample) * 1972-04-13 1978-03-03 Norton Co
GB1465523A (en) * 1973-01-26 1977-02-23 Norton Co Low surface area alumina
US4066575A (en) * 1976-07-26 1978-01-03 Halcon International, Inc. Process for the preparation of a supported silver catalyst
FR2396588A1 (fr) * 1977-07-08 1979-02-02 Ugine Kuhlmann Catalyseurs a base d'argent pour la production d'oxyde d'olefines
US4379134A (en) * 1981-02-13 1983-04-05 Union Carbide Corporation Process of preparing high purity alumina bodies
US4575494A (en) * 1984-02-08 1986-03-11 The Dow Chemical Company Alumina compositions useful as catalyst supports for ethylene oxidation
EP0211521B1 (en) * 1985-07-31 1990-03-21 Imperial Chemical Industries Plc Process of promoting catalysts for the production of alkylene oxides
GB8611121D0 (en) * 1986-05-07 1986-06-11 Shell Int Research Silver catalyst
JPH084745B2 (ja) * 1986-05-09 1996-01-24 三菱化学株式会社 エチレンオキシド製造用銀触媒

Also Published As

Publication number Publication date
US5063195A (en) 1991-11-05
CN1009437B (zh) 1990-09-05
JPH0667475B2 (ja) 1994-08-31
EP0327356A1 (en) 1989-08-09
CN1034678A (zh) 1989-08-16
DE68921777D1 (de) 1995-04-27
JPH0256246A (ja) 1990-02-26
EP0327356B1 (en) 1995-03-22
IN171804B (enExample) 1993-01-09

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